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Proceedings, Volume 2, ICEM 2018

The 18th International Conference on Experimental Mechanics (ICEM 2018)

Brussels, Belgium | 1–5 July 2018

Issue Editors: Danny Van Hemelrijck, Dimitrios Aggelis, Nele De Belie, Fabienne Delaunois, Thomas Geernaerts, Patrick Guillaume, Anne Marie Habraken, Patrick Hendrick, Edwin Reynders, Aude Simar and Steve Vanlanduit


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Cover Story (view full-size image) Experimental mechanics play a crucial role in all stages of a material’s or structure’s life cycle, [...] Read more.
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Research

Open AccessProceedings Early Detection of Damages Based on Comprehensive Theory of Deformation and Fracture
Proceedings 2018, 2(8), 354; https://doi.org/10.3390/ICEM18-05201
Published: 7 May 2018
PDF Full-text (404 KB)
Abstract
Numerical studies have been conducted based on the recently published Deformation Field Theory. Effects of pulling rates on displacement waves and volume expansion waves are analyzed in a finite element model (FEM) of a solid experiencing a uni-axial tensile load. Without relying on
[...] Read more.
Numerical studies have been conducted based on the recently published Deformation Field Theory. Effects of pulling rates on displacement waves and volume expansion waves are analyzed in a finite element model (FEM) of a solid experiencing a uni-axial tensile load. Without relying on empirical data, the model’s numerical results demonstrate empirically known concepts that a fracture occurs more easily when the pulling rate is high, and the direction of external load is reversed. Full article
Open AccessProceedings Experimental Approach for Metals Mechanical Behavior Characterization at High Temperature: Development of a Complex Tensile Test Machine
Proceedings 2018, 2(8), 355; https://doi.org/10.3390/ICEM18-05207
Published: 9 May 2018
PDF Full-text (926 KB)
Abstract
To characterize the mechanical behaviour at high temperature close to the melting point, a tensile test machine has been developed through resistive heating by Joule effect. A closed chamber is designed to control the working environment. By the two windows in the chamber,
[...] Read more.
To characterize the mechanical behaviour at high temperature close to the melting point, a tensile test machine has been developed through resistive heating by Joule effect. A closed chamber is designed to control the working environment. By the two windows in the chamber, the temperature and displacement fields can be measured directly. For the machine, both temperature and tensile force can be controlled by the proportional-integral-derivative controller. In this paper, the main features of the machine’s design and development will be discussed, with a specific section dedicated to the optimization of the specimens’ shape, which is of utmost importance in the context of Joule heating. Full article
Open AccessProceedings Dynamic Behavior of Metals at Elevated Temperatures and Ultra-High Strain Rates
Proceedings 2018, 2(8), 372; https://doi.org/10.3390/ICEM18-05204
Published: 7 May 2018
PDF Full-text (8665 KB)
Abstract
This paper presents the results of a series of reverse geometry normal plate impact experiments designed to investigate the onset of incipient plasticity in commercial purity polycrystalline magnesium (99.9%) under weak uniaxial-strain shock compression loading and elevated temperatures up to the melting point
[...] Read more.
This paper presents the results of a series of reverse geometry normal plate impact experiments designed to investigate the onset of incipient plasticity in commercial purity polycrystalline magnesium (99.9%) under weak uniaxial-strain shock compression loading and elevated temperatures up to the melting point of magnesium. To enable the characterization of dynamic material behavior under extreme conditions, i.e., ultra-high strain rates (~106/s) and test temperatures up to sample melt (1000 °C), strategic modifications were made to the single-stage gas-gun facility at the Case Western Reserve University. In this configuration, thin metal samples (also representing the flyer plate), carried by a specially designed heat-resistant sabot, are heated uniformly across the diameter in a 100 mTorr vacuum prior to impact by a resistance coil heater at the breech end of the gun barrel. Moreover, a compact fiber-optics-based heterodyne normal displacement interferometer is designed and implemented to measure the normal component of the particle velocity history at the free surface of the target plate. Similar to the standard photonic Doppler velocimetry (PDV), this diagnostic tool is assembled using commercially available telecommunications hardware and uses a 1550-nm wavelength 2 W fiber-coupled laser, an optical probe and single mode fibers to transport light to and from the target. Using this unique approach, normal plate impact experiments are conducted on preheated (room temperature to near the melting point of magnesium) 99.9% polycrystalline magnesium using Inconel 718 target plates at impact velocities of 100–110 m/s. As inferred from the measured normal particle velocity history, the stress at the flyer/target interface shows progressive weakening with increasing sample temperatures below the melting point. At higher test temperatures, the rate of material softening under stress is observed to decrease and even reverse as the sample temperatures approach the melting point of magnesium samples. Scanning electron microscopy is utilized to understand the evolution of sample material microstructure including twinning following the impact event. Full article
Open AccessProceedings Experimental Model Validation and Fatigue Behaviour of Cold-Formed High Strength Steel
Proceedings 2018, 2(8), 373; https://doi.org/10.3390/ICEM18-05200
Published: 4 May 2018
PDF Full-text (806 KB)
Abstract
In the present paper, fatigue fracture behaviour of cold-formed High Strength Steel (HSS) S690QL are investigated. S690QL is often employed, in a pre-deformed state, for load-bearing applications, where cyclic service loads can be critical. Bending processes can induce residual plastic strain in bent
[...] Read more.
In the present paper, fatigue fracture behaviour of cold-formed High Strength Steel (HSS) S690QL are investigated. S690QL is often employed, in a pre-deformed state, for load-bearing applications, where cyclic service loads can be critical. Bending processes can induce residual plastic strain in bent areas and this changes the fatigue behaviour significantly. Traditional uniaxial dogbone testing cannot represent this multi-axial phenomenon properly and for this purpose a benchmark specimen is proposed, that is first bent and after subjected to fatigue loading. The bending process is modelled with a quasi-static Finite Element (FE) model, performed in the commercial code Abaqus. To validate the numerical model, a stereo Digital Image Correlation (DIC) set-up is used, capable of measuring the residual plastic strains in the specimen. The present article covers the validation of a cold-forming process followed by a preliminary fatigue analysis of S690QL. Full article
Open AccessProceedings Characterization of the Modal Parameters of Composite Laminates Using Innovative Ultrathin Polymer Waveguide Sensor Foils
Proceedings 2018, 2(8), 374; https://doi.org/10.3390/ICEM18-05195
Published: 4 May 2018
PDF Full-text (841 KB)
Abstract
The use of composite materials, like glass- and carbon- fiber reinforced polymers, is expected to increase exponentially in the coming years. Consequently, in order to monitor the structural health of these materials, the development of new sensing devices is rapidly accelerating. For this
[...] Read more.
The use of composite materials, like glass- and carbon- fiber reinforced polymers, is expected to increase exponentially in the coming years. Consequently, in order to monitor the structural health of these materials, the development of new sensing devices is rapidly accelerating. For this purpose, our research groups have recently developed new ultra-thin polymer waveguide sensors which can be exploited to measure both uniaxial and multiaxial strains occurring in composite components. These sensing foils are manufactured by creating Bragg gratings in waveguides realized in flat polymeric substrates, which makes their placement and alignment easier compared to traditional fiber optic sensors. Moreover, using a non-straight waveguide it is possible to spatially multiplex the sensing gratings in such a way that an optical strain rosette can be created. This paper investigates the suitability of the proposed polymer waveguide sensors for the estimation of the modal parameters of composite components. Full article
Open AccessProceedings Experimental Characterization of Thermoplastics for Use in Heat Exchangers
Proceedings 2018, 2(8), 375; https://doi.org/10.3390/ICEM18-05198
Published: 4 May 2018
PDF Full-text (1407 KB)
Abstract
For the prediction of long term behavior several methods are known. This paper focuses on creep in dynamic mechanical analysis (DMA) and in a tensile setup. The investigated material was Polyamide 6 (PA6). As a pre-study for the DMA, Polypropylene (PP) was tested
[...] Read more.
For the prediction of long term behavior several methods are known. This paper focuses on creep in dynamic mechanical analysis (DMA) and in a tensile setup. The investigated material was Polyamide 6 (PA6). As a pre-study for the DMA, Polypropylene (PP) was tested considering five different factors. To determine the significant influences, the results were interpreted statistically. Full article
Open AccessProceedings Constructing a Transparent Air Chamber for an Innovative Ventilation System in an Operating Room
Proceedings 2018, 2(8), 376; https://doi.org/10.3390/ICEM18-05199
Published: 4 May 2018
PDF Full-text (365 KB)
Abstract
While surgical techniques have been improving during last decades to the benefit of patients’ safety, infections are still recorded. It is in part due to airborne particles entering the wound during surgery, as a result of the disturbance of the unidirectional flow of
[...] Read more.
While surgical techniques have been improving during last decades to the benefit of patients’ safety, infections are still recorded. It is in part due to airborne particles entering the wound during surgery, as a result of the disturbance of the unidirectional flow of clean air (LAF) by the presence of a surgical luminaire system. To prevent this negative interaction, an integrated system of light and ventilation has been designed. However, this system is still conceptual and a mechanical design is needed to prototype the system. Compliance with the European standard on surgical luminaires and the Heating, Ventilation and Air-Conditioning (HVAC) guidelines for operating rooms (OR) have to be checked for this prototype. We thus perform a structural analysis of the air chamber using Autodesk Inventor and SCIA Engineer considering different partitioning scenarios. The impact of each configuration is then assessed by considering the optical performance in the optical simulation TracePro. By comparing shifts in the results to a reference scenario an optimized configuration can be chosen. By consequence, a good balance between optical performance and mechanical strength is determined and leads to an optimized supporting solution. This mechanical design further enables us to build the integrated concept that aims to suppress the negative interaction between light and ventilation in the operating theater. Full article
Open AccessProceedings Long-Term In-Situ Study of Mild Steel Stress Corrosion Cracking Kinetics in a Carbonate-Rich Solution
Proceedings 2018, 2(8), 377; https://doi.org/10.3390/ICEM18-05197
Published: 9 May 2018
PDF Full-text (860 KB)
Abstract
A long-term SCC crack growth kinetics study, using precracked WOL samples, was performed. The samples were exposed in a mild steel storage tank containing a solution with high levels of ammonium and carbonate ions. Some samples were fully immersed in the tank content,
[...] Read more.
A long-term SCC crack growth kinetics study, using precracked WOL samples, was performed. The samples were exposed in a mild steel storage tank containing a solution with high levels of ammonium and carbonate ions. Some samples were fully immersed in the tank content, while in other cases, intermittent drying took place in the tank upper regions. At short times, the highest (intergranular) crack growth rates were obtained at immersed regions and initially, the region with intermittent drying showed considerably slower growth rates. With pronounced exposure times, the trend however reversed and the growth in the intermittent drying region accelerated while the samples in the immersed location experienced a retardation in the SCC growth velocities. It was found that the SCC mechanism progressed through a process where small cracks first formed at the fatigue crack front and thereafter merged to form a continuous SCC crack front. Full article
Open AccessProceedings A Robust Test-Based Modal Model Identification Method for Challenging Industrial Cases
Proceedings 2018, 2(8), 378; https://doi.org/10.3390/ICEM18-05196
Published: 4 May 2018
PDF Full-text (435 KB)
Abstract
Abstract: In this paper, the MLMM modal parameter estimation method (Maximum Likelihood estimation of a Modal Model) and its new variant will be introduced. The MLMM method tackles some of the remaining challenges in modal analysis (e.g., modal analysis of highly-damped cases
[...] Read more.
Abstract: In this paper, the MLMM modal parameter estimation method (Maximum Likelihood estimation of a Modal Model) and its new variant will be introduced. The MLMM method tackles some of the remaining challenges in modal analysis (e.g., modal analysis of highly-damped cases where a large amount of excitation locations is needed such as the modal analysis of a trimmed car body). Another big advantage of the MLMM method is its capability to fully integrate, within the estimated modal model, some important physical constraints, which are required for the intended applications, e.g., realness of the mode shape and FRFs reciprocity. More classical modal parameter estimation methods have rarely the possibility to fully integrate these constraints and the obtained modal parameters are typically altered in a subsequent step to satisfy the desired constraints. It is obvious that this may lead to sub-optimal results. The MLMM method uses the Levenberg-Marquardt optimization scheme to directly fit the modal model to the measured FRFs. The applicability of MLMM to estimate an accurate constrained modal model will be demonstrated using two challenging industrial applications. Full article
Open AccessProceedings The Cause Estimation of Damages in Pathein Suspension Bridge Based on Vibration Measurements
Proceedings 2018, 2(8), 379; https://doi.org/10.3390/ICEM18-05209
Published: 9 May 2018
PDF Full-text (1421 KB)
Abstract
Pathein suspension bridge situated in Pathein City in the south of Myanmar has shown various symptoms of damage, and the safety of the bridge is questionable. The authorities concerned reported that the bridge has undergone severe deterioration since its construction, involving the towers’
[...] Read more.
Pathein suspension bridge situated in Pathein City in the south of Myanmar has shown various symptoms of damage, and the safety of the bridge is questionable. The authorities concerned reported that the bridge has undergone severe deterioration since its construction, involving the towers’ inclination, excessive deflections, bearing failure, heavy corrosion of main cables and hangers, hangers’ inclination, and slippage of clamps. The deformed shape of the stiffening girder was found to be unusual, with maximum deflection nearer to the towers; however, in a single span bridge, such as Pathein Bridge, the maximum deflection is expected to be at mid-span. This paper will explain the possible reasons for the unusual excessive deformations in the stiffening girder and bearing failure. The tension force of hangers was estimated based on vibration measurements, and the distribution of hangers’ tension force along the bridge’s span was found to be non-uniform with low-tension force in hangers closer to the towers. The non-uniform distribution of the hangers’ tension force is possibly due to shortcomings of the design of the cable system. The towers’ inclination has caused the road level to drop down; however, the unusual deformations in stiffening girder are attributed to the non-uniform distribution of the tension force in the hangers. Low-tension force in the hangers near the towers caused the bearing to carry excessive force, which eventually caused the bearing to fail; the bearing was rehabilitated by adding steel rollers. Full article
Open AccessProceedings Fatigue Damage Evaluation by Diffraction Contrast Tomography Using Ultra-Bright Synchrotron Radiation
Proceedings 2018, 2(8), 380; https://doi.org/10.3390/ICEM18-05210
Published: 9 May 2018
PDF Full-text (1066 KB)
Abstract
A three-dimensional grain mapping technique for polycrystalline materials, called X-ray diffraction contrast tomography (DCT), was developed at SPring-8, which is the brightest synchrotron radiation facility in Japan. The developed technique was applied to an austenitic stainless steel. The shape and location of grains
[...] Read more.
A three-dimensional grain mapping technique for polycrystalline materials, called X-ray diffraction contrast tomography (DCT), was developed at SPring-8, which is the brightest synchrotron radiation facility in Japan. The developed technique was applied to an austenitic stainless steel. The shape and location of grains could be determined by DCT using the apparatus in a beam line of SPring-8. To evaluate the dislocation structure in fatigue, the total misorientation of individual grains was measured by DCT. The average value of the total misorientation over one sample was increased with the number of cycles. In a grain, the change of the total misorientation was largest for the primary slip plane. The maximum change of the total misorientation in fatigue was larger for planes with larger Schmid factor, and the first fatigue crack initiation was occurred in a grain, which had the greatest change of the total misorientation. Full article
Open AccessProceedings An Improved Load Introduction Technique for Dynamic Material Characterisation at Intermediate Strain Rate
Proceedings 2018, 2(8), 381; https://doi.org/10.3390/ICEM18-05203
Published: 9 May 2018
PDF Full-text (1187 KB)
Abstract
Dynamic properties at intermediate strain rate are inherently difficult due to the dynamic interactions between the test specimen and the test machine. These effects obscure the interpretation of test results and therefore can make the derivation of the material properties difficult and unprecise.
[...] Read more.
Dynamic properties at intermediate strain rate are inherently difficult due to the dynamic interactions between the test specimen and the test machine. These effects obscure the interpretation of test results and therefore can make the derivation of the material properties difficult and unprecise. Soft materials can be used within load introduction devices to mitigate the inertia effect that typically occurs in dynamic tests. In this paper, dynamic tensile tests were performed within the strain rate range of 0.1 s−1 to 400 s−1 on high strength steels. With the aim of evaluating the performance of damping materials in the slack adaptor, copper and acrylic tapes were used. Experimental results show that both damping materials may be used to effectively reduce the oscillations in the measured force signal. The outcome of this project will provide the test procedure for dynamic testing at intermediate strain rates, which can produce reliable test results for materials with low failure to strain. Full article
Open AccessProceedings Inverse Yield Locus Identification of Sheet Metal Using a Complex Cruciform in Biaxial Tension and Digital Image Correlation
Proceedings 2018, 2(8), 382; https://doi.org/10.3390/ICEM18-05208
Published: 9 May 2018
PDF Full-text (2173 KB)
Abstract
Finite Element Model Updating (FEMU) is an intuitive inverse technique enabling to efficiently characterize plastic material behavior. Although, conclusive proof of concept for this method can be found in literature, a thorough understanding of the key FEMU-ingredients and their impact on the identification
[...] Read more.
Finite Element Model Updating (FEMU) is an intuitive inverse technique enabling to efficiently characterize plastic material behavior. Although, conclusive proof of concept for this method can be found in literature, a thorough understanding of the key FEMU-ingredients and their impact on the identification of plastic anisotropy is currently missing. In this paper, we aim at minimizing the experimental work associated with yield locus identification of sheet metal via homogeneous biaxial tensile tests. To this end, a biaxial tension apparatus with link mechanism is used to generate a heterogeneous deformation field within a perforated cruciform specimen. The experimentally measured force and displacement field are used in the FEMU procedure to identify an anisotropic yield criterion. The FEMU approach is assessed by comparing the results with experimental data acquired from state-of-the-art stress-controlled biaxial tensile test in the first quadrant of stress-space. Full article
Open AccessProceedings Mechanical Characterization of Compact Basalt by Using SHPB Device
Proceedings 2018, 2(8), 383; https://doi.org/10.3390/ICEM18-05202
Published: 9 May 2018
PDF Full-text (2101 KB)
Abstract
In the present work, dynamic stress-strain response of compact basalt is tested under high loading rates using 38 mm split Hopkinson pressure bar (SHPB) device. The physical and static mechanical properties of compact basalt, e.g., density, specific gravity, static compressive strength and elastic
[...] Read more.
In the present work, dynamic stress-strain response of compact basalt is tested under high loading rates using 38 mm split Hopkinson pressure bar (SHPB) device. The physical and static mechanical properties of compact basalt, e.g., density, specific gravity, static compressive strength and elastic modulus values are also determined. Petrological studies of compact basalt are carried out through X-ray diffraction (XRD) test and scanning electron microscope (SEM) test. In the SHPB tests, it is observed from the stress-strain response that the dynamic peak stress increases with increasing strain rate however the elastic modulus is nearly constant with increase in strain rate. Dynamic force equilibrium at the incident and transmission bar ends of the rock samples is attained in all tests till the failure of the rock samples. Dynamic increase factor (DIF) for the rock is determined at a particular strain rate by comparing the dynamic to static peak compressive stress. Correlation equation for dynamic strength increase factor with respect to strain rate has been proposed herein. Full article
Open AccessProceedings Overview of Current Challenges in Self-Pierce Riveting of Lightweight Materials
Proceedings 2018, 2(8), 384; https://doi.org/10.3390/ICEM18-05206
Published: 9 May 2018
PDF Full-text (1053 KB)
Abstract
This paper shows an overview of different analyses regarding current challenges at self-pierce riveting with solid rivets as well as semi-tubular rivets of lightweight materials like aluminum die casting, carbon fiber reinforced plastic and 7xxx series aluminum alloy. The joining process analyses will
[...] Read more.
This paper shows an overview of different analyses regarding current challenges at self-pierce riveting with solid rivets as well as semi-tubular rivets of lightweight materials like aluminum die casting, carbon fiber reinforced plastic and 7xxx series aluminum alloy. The joining process analyses will demonstrate the cause and the development as well as the influence on joint quality of individual joining process-induced defects. In addition, methods are described how these imperfections can be avoided or reduced. Full article
Open AccessProceedings Proposal to Standardize Fatigue Delamination Growth Tests Using Double Cantilever Beam Specimens without Fibre Bridging
Proceedings 2018, 2(8), 385; https://doi.org/10.3390/ICEM18-05194
Published: 9 May 2018
PDF Full-text (554 KB)
Abstract
Up until today, mode-I fatigue delamination testing has not been standardized, because no consensus exists on best practices to reduce the observed scatter in data, and on the proper parameter describing similitude. A dominant contributor to the scatter seems the fibre bridging observed
[...] Read more.
Up until today, mode-I fatigue delamination testing has not been standardized, because no consensus exists on best practices to reduce the observed scatter in data, and on the proper parameter describing similitude. A dominant contributor to the scatter seems the fibre bridging observed in the tests. This paper proposes a straightforward experimental and analysis approach to derive zero-bridging delamination resistance curves from each tested specimen without requiring a theoretical model. Full article
Open AccessProceedings Global Response of a Three-Story Building Exposed to Blast Loading
Proceedings 2018, 2(8), 386; https://doi.org/10.3390/ICEM18-05211
Published: 9 May 2018
PDF Full-text (793 KB)
Abstract
Experimental data from full-scale experiments with reinforced concrete buildings exposed to blast loading are limited. As full-scale experiments are expensive, numerical simulations of the global response of structures exposed to blast loading may be an attractive substitute. A full-scale experiment on a three-story
[...] Read more.
Experimental data from full-scale experiments with reinforced concrete buildings exposed to blast loading are limited. As full-scale experiments are expensive, numerical simulations of the global response of structures exposed to blast loading may be an attractive substitute. A full-scale experiment on a three-story reinforced concrete building exposed to air-blast is employed to evaluate the performance of FE simulations to represent global response of reinforced concrete structures. The building experienced close to elastic response in the load bearing walls and columns, while cracks were observed in the front wall facing the charge. FE simulations of the global response of the building are performed with a solid element model and a structural element model (shell elements) to compare accuracy to computational cost. The results show that the FE simulations with solid and structural elements give an adequate representation of the global response of the building to a relatively low cost. Full article
Open AccessProceedings Experimental and Numerical Investigation on the Impact Response of Elastomer-Coated Concrete
Proceedings 2018, 2(8), 387; https://doi.org/10.3390/ICEM18-05212
Published: 9 May 2018
PDF Full-text (468 KB)
Abstract
The use of a spray application elastomer coating as an effective retrofit strategy for blast and impact mitigation has gained increasing attention in recent years. Despite some encouraging studies in the literature, there remains a great deal yet to be understood, particularly regarding
[...] Read more.
The use of a spray application elastomer coating as an effective retrofit strategy for blast and impact mitigation has gained increasing attention in recent years. Despite some encouraging studies in the literature, there remains a great deal yet to be understood, particularly regarding the coating’s impact mitigating capabilities when applied to structural elements. In this work, we consider the application of a spray-on elastomer coating to the impacted face of a concrete cube. High-speed, gas gun experiments are performed on concrete cubes in their uncoated and coated configurations and it is observed that the coating provides a significant protective benefit across the range of test velocities, 45–150 m/s. Quasi-static compression and indentation experimental tests are performed on uncoated and coated concrete cubes to inform the development of a numerical model. Despite a number of modelling challenges, we validate our model against experimental measurements and conclude it provides accurate predictions of behaviour at early time steps, before the concrete becomes severely damaged. Future work will focus on using this validated numerical model as an analysis tool for understanding the mechanism by which the elastomer alters the damage response of the underlying concrete substrate. Full article
Open AccessProceedings 3D Modeling of Plaque Progression in the Human Coronary Artery
Proceedings 2018, 2(8), 388; https://doi.org/10.3390/ICEM18-05213
Published: 9 May 2018
PDF Full-text (1042 KB)
Abstract
The inflammation and lipid accumulation in the arterial wall represents a progressive disease known as atherosclerosis. In this study, a numerical model of atherosclerosis progression was developed. The wall shear stress (WSS) and blood analysis data have a big influence on the development
[...] Read more.
The inflammation and lipid accumulation in the arterial wall represents a progressive disease known as atherosclerosis. In this study, a numerical model of atherosclerosis progression was developed. The wall shear stress (WSS) and blood analysis data have a big influence on the development of this disease. The real geometry of patients, and the blood analysis data (cholesterol, HDL, LDL, and triglycerides), used in this paper, was obtained within the H2020 SMARTool project. Fluid domain (blood) was modeled using Navier-Stokes equations in conjunction with continuity equation, while the solid domain (arterial wall) was modeled using Darcy’s law. For the purpose of modeling low-density lipoprotein (LDL) and oxygen transport, convection-diffusion equations were used. Kedem-Katchalsky equations were used for coupling fluid and solid dynamics. Full article
Open AccessProceedings Crack Tip Monitoring of Mode I and Mode II Delamination in CF/Epoxies under Static and Dynamic Loading Conditions Using Digital Image Correlation
Proceedings 2018, 2(8), 389; https://doi.org/10.3390/ICEM18-05225
Published: 9 May 2018
PDF Full-text (847 KB)
Abstract
Digital image correlation has been used, in conjunction with Mode I and Mode II fracture mechanics tests under static and dynamic loading conditions, to determine the position of the crack front during interlaminar testing. A MATLAB code has been developed to post process
[...] Read more.
Digital image correlation has been used, in conjunction with Mode I and Mode II fracture mechanics tests under static and dynamic loading conditions, to determine the position of the crack front during interlaminar testing. A MATLAB code has been developed to post process the digital image correlation analysis to determine the experimentally measured crack position and these results have been compared to compliance-based predictions of crack position which do not use a physical measure of the crack length. Results have shown that the digital image correlation analysis has successfully tracked the crack position providing a physical measure of the crack front during static and dynamic testing for the calculation of fracture toughness values. This methodology, incorporating digital image correlation for crack position monitoring, was then expanded to analyses for fatigue tests showing that the physical crack length has a varied growth rate in comparison to the steady change in specimen compliance. Full article
Open AccessProceedings Lab-on-Chip Prototype for the Detection of Coronary Artery Disease Biomarkers
Proceedings 2018, 2(8), 390; https://doi.org/10.3390/ICEM18-05215
Published: 9 May 2018
PDF Full-text (1693 KB)
Abstract
We report an easy-to-use Lab-on-Chip (LoC) device able to detect soluble, circulating biomarkers in plasma that are relevant to Coronary Artery Disease (CAD). The LoC prototype is developed within the SMARTool European project and is intended to be used for Point-of-Care (PoC) testing
[...] Read more.
We report an easy-to-use Lab-on-Chip (LoC) device able to detect soluble, circulating biomarkers in plasma that are relevant to Coronary Artery Disease (CAD). The LoC prototype is developed within the SMARTool European project and is intended to be used for Point-of-Care (PoC) testing of patients with CAD, facilitating more rapid and efficient monitoring and treatment decisions. A LoC prototype is presented, enabling chemiluminescent assays to be performed on chip targeting biomarkers relevant to CAD. In parallel, a robust technology for electrostatically actuated, capillary burst valve for PoC applications, integrated in potentially disposable, thermoplastic devices is reported. The devices were fabricated using easily scalable fabrication techniques and can be used to perform multistep assays on single-use microfluidic devices. Full article
Open AccessProceedings Steps towards Industrial Validation Experiments
Proceedings 2018, 2(8), 391; https://doi.org/10.3390/ICEM18-05216
Published: 9 May 2018
PDF Full-text (878 KB)
Abstract
Imaging systems for measuring surface displacement and strain fields such as stereoscopic Digital Image Correlation (DIC) are increasingly used in industry to validate model simulations. Recently, CEN has published a guideline for validation that is based on image decomposition to compare predicted and
[...] Read more.
Imaging systems for measuring surface displacement and strain fields such as stereoscopic Digital Image Correlation (DIC) are increasingly used in industry to validate model simulations. Recently, CEN has published a guideline for validation that is based on image decomposition to compare predicted and measured data fields. The CEN guideline was evaluated in an inter-laboratory study that demonstrated its usefulness in laboratory environments. This paper addresses the incorporation of the CEN methodology into an industrial environment and reports progress of the H2020 Clean Sky 2 project MOTIVATE. First, while DIC is a well-established technique, the estimation of its measurement uncertainty in an industrial environment is still being discussed, as the current approach to rely on the calibration uncertainty is insufficient. Second, in view of the push towards virtual testing it is important to harvest existing data in the course of the V&V activities before requesting a dedicated validation experiment, specifically at higher levels of the test pyramid. Finally, it is of uttermost importance to ensure compatibility and comparability of the simulation and measurement data so as to optimize the test matrix for maximum reliability and credibility of the simulations and a quantification of the model quality. Full article
Open AccessProceedings Static and Fatigue Damage Characterization of Carbon/Epoxy Angle-Ply Laminates with the Use of Acoustic Emission and Online Microscopy
Proceedings 2018, 2(8), 392; https://doi.org/10.3390/ICEM18-05220
Published: 14 May 2018
PDF Full-text (1962 KB)
Abstract
In the current work, a combined non-destructive methodology is proposed in order to investigate the static and fatigue damage of carbon fiber reinforced epoxy composites. Flat angle-ply laminates are used in order to examine the influence of multiaxial stress states on the mechanical
[...] Read more.
In the current work, a combined non-destructive methodology is proposed in order to investigate the static and fatigue damage of carbon fiber reinforced epoxy composites. Flat angle-ply laminates are used in order to examine the influence of multiaxial stress states on the mechanical performance using different non-destructive techniques. Acoustic emission is combined with an online microscope and digital image correlation and this combination is used to comprehend the performance of composites with unequal stress states. Full article
Open AccessProceedings Analysis of the Flexural Behavior of Textile Reinforced Reactive Powder Concrete Sandwich Elements Using Optical Measurements
Proceedings 2018, 2(8), 393; https://doi.org/10.3390/ICEM18-05221
Published: 14 May 2018
PDF Full-text (680 KB)
Abstract
Prefabricated and non-load bearing sandwich façade elements were developed using Textile Reinforced Reactive Powder Concrete (TRRPC) along with low density Foamed Concrete (FC) and Glass Fiber Reinforced Polymer (GFRP) continuous connecting devices. Four-point bending tests were performed on large-scale TRRPC sandwich element beams
[...] Read more.
Prefabricated and non-load bearing sandwich façade elements were developed using Textile Reinforced Reactive Powder Concrete (TRRPC) along with low density Foamed Concrete (FC) and Glass Fiber Reinforced Polymer (GFRP) continuous connecting devices. Four-point bending tests were performed on large-scale TRRPC sandwich element beams to characterize the structural performance, which included the flexural capacity, level of composite action, resulting deformation, crack propagation and failure mechanisms. Optical measurements based on Digital Image Correlation (DIC) were taken simultaneously to enable a detailed analysis of the underlying composite action. The structural behavior of the developed elements was found to be highly dependent on the stiffness and strength of the connectors to ensure composite action between the two TRRPC panels. Full article
Open AccessProceedings Acoustic Emission Signal Associated to Fiber Break during a Single Fiber Fragmentation Test: Modeling and Experiment
Proceedings 2018, 2(8), 394; https://doi.org/10.3390/ICEM18-05222
Published: 14 May 2018
PDF Full-text (1663 KB)
Abstract
The objective of this work is to build a quantitative relationship between the fiber break as source of Acoustic Emission (AE) and the detected signal by unravelling the effect of each stage of the AE acquisition chain. For this purpose, an AE modelling
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The objective of this work is to build a quantitative relationship between the fiber break as source of Acoustic Emission (AE) and the detected signal by unravelling the effect of each stage of the AE acquisition chain. For this purpose, an AE modelling is carried out using the Finite Element Method and then the simulation is compared to experimental results of Single Fiber Fragmentation Test (SFFT). The SFFT is used in order to produce preferential fiber break. It is carried out on specimens made from a long carbon fiber embedded in epoxy/amine matrix. Two different types of sensor are used in order to gather information on a wider frequency bandwidth. For the modeling part, the entire geometry of the specimen is modelled using Finite Element Method. There is a good agreement between experiment and modeling results. Full article
Open AccessProceedings Characterization Procedure for Bond, Anchorage and Strain-Hardening Behavior of Textile-Reinforced Cementitious Composites
Proceedings 2018, 2(8), 395; https://doi.org/10.3390/ICEM18-05224
Published: 15 May 2018
PDF Full-text (663 KB)
Abstract
A fast adoption of innovative composite materials such as textile reinforced concrete (TRC) in practice is hindered by the lack of efficient and standardized characterization and design procedures. In this paper, we discuss results of uniaxial tensile tests and double sided pullout tests.
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A fast adoption of innovative composite materials such as textile reinforced concrete (TRC) in practice is hindered by the lack of efficient and standardized characterization and design procedures. In this paper, we discuss results of uniaxial tensile tests and double sided pullout tests. The analysis of the tests is done with a modelling framework for tensile behavior developed at IMB RWTH Aachen. The overall goal is to simulate the tensile response of composite specimen based on the reinforcement and matrix characteristics. Thus, the need for cost-intensive composite tensile tests could be reduced, which facilitates the material development and adoption of TRC in engineering practice. Full article
Open AccessProceedings Experimental Analysis of Monotonic and Cyclic Pull-Out of Steel Fibres by Means of Acoustic Emission and X-ray Microfocus Computed Tomography
Proceedings 2018, 2(8), 396; https://doi.org/10.3390/ICEM18-05226
Published: 15 May 2018
PDF Full-text (929 KB)
Abstract
This research aims to investigate the monotonic and cyclic pull-out behavior of steel fibres by means of advanced non-destructive testing methods (NDT). Forty individually embedded steel fibres in a concrete matrix are tested in a pull-out setup with continuous acoustic emission monitoring and
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This research aims to investigate the monotonic and cyclic pull-out behavior of steel fibres by means of advanced non-destructive testing methods (NDT). Forty individually embedded steel fibres in a concrete matrix are tested in a pull-out setup with continuous acoustic emission monitoring and X-ray microfocus computed tomography is applied before, during and after testing. The developed setup allows to improve and to better control the experiments. The combination of NDT methods leads to a deeper insight compared to the traditional pull-out tests, by inspection of deviating results, detection of the pull-out stages, and localization of internal damage combined with visualization of the internal structure. Full article
Open AccessProceedings Investigation of 3D TRC’s by Means of Three Point Bending Tests on Short Beam Specimens
Proceedings 2018, 2(8), 397; https://doi.org/10.3390/ICEM18-05227
Published: 15 May 2018
PDF Full-text (2932 KB)
Abstract
Textile reinforced cements (TRC), combining a cementitious matrix with fibre textiles, are a well-researched subject in literature. The material offers several advantages such as the design of low-weight, slender structures. However, one of the main drawbacks of this composite material is the time
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Textile reinforced cements (TRC), combining a cementitious matrix with fibre textiles, are a well-researched subject in literature. The material offers several advantages such as the design of low-weight, slender structures. However, one of the main drawbacks of this composite material is the time consuming manufacturing process using two dimensional fibre textiles. Three dimensional fibre textile architectures offer a solution to this problem, while retaining the TRC advantages. Most 3D fibre textiles use distance holders to bridge two, or more textile layers at a certain distance from each other. The influence of this distance holder on the mechanical properties of the whole TRC remains relatively unstudied in literature and will be the research topic of this paper. This research will present the results of three point bending experiments, performed on short TRC beams with a length to thickness ratio of approximately 4 to 1. A comparison is drawn between 3D TRC with fully operational 3D fibre textiles and 2D TRC with the same textile geometry and orientation, but without distance holders. A positive influence on the flexural response is witnessed for the 3D fibre textile, with an increased flexural stiffness up to 35%. Full article
Open AccessProceedings Ultrahigh Carbon Nanotube Volume Fraction Effects on Micromechanical Quasi-Static & Dynamic Properties of Poly(Urethane-Urea) Filled Nanocomposites
Proceedings 2018, 2(8), 398; https://doi.org/10.3390/ICEM18-05228
Published: 15 May 2018
PDF Full-text (508 KB)
Abstract
Poly(urethane-urea) (PUU) has been infused into ultrahigh volume fraction carbon nanotube (CNT) forests using a heat-curable polymer formula. Polymer nanocomposites with carbon nanotube volume-fractions of 1%, 5%, 10%, 20%, and 30% were fabricated by overcoming densification and infusion obstacles. These polymer nanocomposites were
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Poly(urethane-urea) (PUU) has been infused into ultrahigh volume fraction carbon nanotube (CNT) forests using a heat-curable polymer formula. Polymer nanocomposites with carbon nanotube volume-fractions of 1%, 5%, 10%, 20%, and 30% were fabricated by overcoming densification and infusion obstacles. These polymer nanocomposites were nanoindented quasi-statically and dynamically to discern process-structure-(mechanical) property relations of polymerizing PUU in such densely-packed CNT forests. A 100× increase in indentation modulus has been observed, which is attributed not only to CNT reinforcement of the matrix, but also to molecular interactions in the matrix itself. Quasi-static elastic moduli ranging from 10 MPa–4.5 GPa have been recorded. Storage modulus for all materials is found to track well at loadings of 200 Hz, with little effect observed from increasing CNT volume fraction. Full article
Open AccessProceedings Comparison of Fracture Resistance of the Normal and High Strength Concrete Evaluated by Brazilian Disc Test
Proceedings 2018, 2(8), 399; https://doi.org/10.3390/ICEM18-05236
Published: 19 May 2018
PDF Full-text (609 KB)
Abstract
Nowadays, high performance concrete is used more frequently because of the many advantages compared to traditional concrete. The higher mechanical properties (e.g., compressive strength, flexural strength, and Young’s modulus) allow for larger spans and slender cross-sections. Despite the use of advanced material, standards
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Nowadays, high performance concrete is used more frequently because of the many advantages compared to traditional concrete. The higher mechanical properties (e.g., compressive strength, flexural strength, and Young’s modulus) allow for larger spans and slender cross-sections. Despite the use of advanced material, standards for structural design do not fully use materials’ potential. This can be minimized by using fracture mechanical properties in structural analysis. The fracture mechanical properties help to perform advanced structural analysis, especially when some of the structural elements have a crack. The load presence on the structure can be divided into tensile—mode I, shear—mode II, and combination of tension and shear—mixed mode I/II load. Therefore, it is necessary to perform test, which covers mixed mode loading conditions. One of the tests usually used for the evaluation of fracture resistance of concrete is Brazilian disc test. This contribution compares fracture resistance of two types of structural concrete (normal and high strength) under the mixed mode I/II. The generalized maximum tangential stress (GMTS) criterion was used for the evaluation of the fracture resistance. Full article
Open AccessProceedings On the Material Characterization of an Aluminium Alloy Using Different Specimens and Identification Methods
Proceedings 2018, 2(8), 400; https://doi.org/10.3390/ICEM18-05237
Published: 19 May 2018
PDF Full-text (1027 KB)
Abstract
The validity of material properties obtained from uniaxial tension tests using different specimen types and measurement techniques is investigated in this paper. Four different specimen geometries were tested, including round axisymmetric and rectangular flat samples of different sizes. This gave a significant variation
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The validity of material properties obtained from uniaxial tension tests using different specimen types and measurement techniques is investigated in this paper. Four different specimen geometries were tested, including round axisymmetric and rectangular flat samples of different sizes. This gave a significant variation in both size and shape of the specimens. The specimens were strained in tension to fracture, and different measurement techniques were applied to measure the deformation of the specimens during loading. This involved an extensometer, a laser micrometre, digital image correlation (DIC) and edge tracing. Cauchy stress versus logarithmic strain curves were obtained from the experimental data, and little spread was seen between the different test series. The data were further used to calibrate a work-hardening relation for the material, and it was found that the fitted curves differed mainly for strains beyond diffuse necking. Full article
Open AccessProceedings Analysis of Failure Modes in Fiber Reinforced Concrete Using X-ray Tomography and Digital Volume Correlation
Proceedings 2018, 2(8), 401; https://doi.org/10.3390/ICEM18-05238
Published: 19 May 2018
PDF Full-text (1253 KB)
Abstract
Pull-out mechanisms for different common steel fibers were investigated using adapted pull-out tests performed in-situ in an X-ray micro tomograph (µXRT). High-resolution volume images from the µXRT scans enable clear visualization of aggregates, pores, the fiber and the fiber-matrix interface. Furthermore, the natural
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Pull-out mechanisms for different common steel fibers were investigated using adapted pull-out tests performed in-situ in an X-ray micro tomograph (µXRT). High-resolution volume images from the µXRT scans enable clear visualization of aggregates, pores, the fiber and the fiber-matrix interface. Furthermore, the natural density speckle pattern from aggregate distribution and pores was found suitable for Digital Volume Correlation (DVC) analysis. From the DVC results it was possible to visualize and quantify the strain distribution in the matrix around the fiber at the different load levels up to final failure, being marked by either pull-out or fiber rupture. This study demonstrates that strain measurements within the concrete matrix can be obtained successfully using µXRT imaging and DVC analysis, which leads to an increased understanding of the interaction mechanisms in fibre reinforced concrete under mechanical loading. Full article
Open AccessProceedings Crack Resistance of RT-PMMA under Impact Loading
Proceedings 2018, 2(8), 402; https://doi.org/10.3390/ICEM18-05239
Published: 19 May 2018
PDF Full-text (459 KB)
Abstract
Analysis of failure mechanisms under high strain rate loading in engineering materials is a key point for the design of structures submitted to accidental overloads. We are here interested in the crack arrest capability under impact loading of polymers used as structural and/or
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Analysis of failure mechanisms under high strain rate loading in engineering materials is a key point for the design of structures submitted to accidental overloads. We are here interested in the crack arrest capability under impact loading of polymers used as structural and/or protection materials. In the present work, crack arrest capability is defined by how an engineering structure which is initially weakened by a pre-crack behaves when dynamically reloaded. The Kalthoff and Winkler (KW) impact test, consisting in impacting the edge of a double notched plate, is retained for that purpose. An experimental investigation of the dynamic crack arrest capability of shock-resistant PMMA under high strain rate loading is presented, evidencing the brittle feature of the material failure. A high-speed camera is used to record the chronology of the failure mechanisms. It is notably shown that the higher the impact velocity (in the range 50–100 m/s) the larger the number of fragments. Moreover, depending on the impact velocity, changes in the crack path and thus in the mechanisms controlling the PMMA dynamic fracture can be seen. Full article
Open AccessProceedings Experimental Study on Spallation of Titanium Alloy Plates under Intense Impulse Loading
Proceedings 2018, 2(8), 403; https://doi.org/10.3390/ICEM18-05240
Published: 20 May 2018
PDF Full-text (659 KB)
Abstract
The dynamic response and spall characteristics of a double-layer TC4 titanium alloy thin target under intense impulse loading was investigated experimentally using electric gun technique. A velocity-measuring instrument, known as VISAR (velocity interferometer system for any reflector), measured the free surface velocity of
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The dynamic response and spall characteristics of a double-layer TC4 titanium alloy thin target under intense impulse loading was investigated experimentally using electric gun technique. A velocity-measuring instrument, known as VISAR (velocity interferometer system for any reflector), measured the free surface velocity of targets. Typical characteristic parameters of the velocity were calculated by the obtained data. The deformation/failure modes of the samples were analyzed, and based on stress wave propagation theory, the spall thickness was derived. Furthermore, it was found that the oscillation period of the free surface velocity can be used to estimate the location of spalling damage, but cannot directly reflect the full spallation of the target. Full article
Open AccessProceedings Research on the Artificial Acceleration Test System of Combined Environment and Loading Effect for the Bridge Structure
Proceedings 2018, 2(8), 404; https://doi.org/10.3390/ICEM18-05282
Published: 29 May 2018
PDF Full-text (803 KB)
Abstract
The bridges will be in service in a complex environment for over 100 years under the increasing traffic loading. So the long-term performance determines their safety and durability. Limited by the test condition and ability, present researches are mostly focused on the natural
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The bridges will be in service in a complex environment for over 100 years under the increasing traffic loading. So the long-term performance determines their safety and durability. Limited by the test condition and ability, present researches are mostly focused on the natural environment exposure tests and artificial environment acceleration tests for materials and components. According to the service conditions and load characteristics of the bridges, the accelerated test system was developed for bridge structure under combined environment and loading. This test system consists of three parts, including a large environment box, loading system and monitoring system. The environment box is 32 m long, 4 m wide and 3/10 m high. It is divided into 5 working bins which can be used alone or in combination. The simulation environment includes high temperature drying, low temperature freezing and thawing, damp cold, high temperature cycle, salt fog, rain, carbonation, temperature and humidity alternating and optical spectrum light aging environment. The servo static and dynamic loading system adopts Servotest actuators with loading tonnage from 400 tons to 50 tons. And the total tonnage is 1200 tons. Aided by the prestressed concrete reaction wall, steel structure frames and the anchor system, the external loading system can exert dynamic and static loads on the bridge structure in the environment box. And the non-contact nondestructive monitoring system can real-time monitor and measure their long-term deformation, internal force, cracking and other damage. This artificial acceleration test system can support the Chinese Long Term Bridge Program, and improve the safety, durability, reliability and long service life of bridges and other civil engineering. Full article
Open AccessProceedings Dynamic Tensile Testing of Brittle Composites Using a Hydraulic Pulse Machine: Stress-Strain Synchronization and Strain Rate Limits
Proceedings 2018, 2(8), 405; https://doi.org/10.3390/ICEM18-05274
Published: 27 May 2018
PDF Full-text (667 KB)
Abstract
The effect of synchronization on the test results is explored by performing dynamic tensile tests on several continuous-fibre composite laminates. The results show that synchronization is key, because a delay of a single microsecond significantly affects the test outcome at high strain rates.
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The effect of synchronization on the test results is explored by performing dynamic tensile tests on several continuous-fibre composite laminates. The results show that synchronization is key, because a delay of a single microsecond significantly affects the test outcome at high strain rates. Additionally, several upper limits on the maximum achievable strain rate of the experimental set-up are determined with the aid of a finite element model. These limits depend on the characteristics of the used equipment, the properties of the tested material and the chosen specimen dimensions. Full article
Open AccessProceedings Investigation to Local Defect Resonance for Non-Destructive Testing of Composites
Proceedings 2018, 2(8), 406; https://doi.org/10.3390/ICEM18-05273
Published: 27 May 2018
PDF Full-text (732 KB)
Abstract
Local defect resonance (LDR) makes use of high frequency vibrations to get a localized resonant activation of a defective region. In this study, the LDR behavior of carbon fiber reinforced polymer (CFRP) coupons with three different types of damages is investigated using broadband
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Local defect resonance (LDR) makes use of high frequency vibrations to get a localized resonant activation of a defective region. In this study, the LDR behavior of carbon fiber reinforced polymer (CFRP) coupons with three different types of damages is investigated using broadband measurements obtained with a scanning laser Doppler vibrometer (SLDV). First, the LDR response of flat bottom holes of different depths and sizes is evaluated using a signal-to-noise ratio. Next, results are obtained for ETFE inserts where the difference between (artificial) delaminations and inserts is outlined. At last, the vibrational response of a CFRP coupon with barely visible impact damage is investigated. This type of damage has a more complex structure, and it is shown that frequency band data (an alternative to the single frequency LDR) performs well in identifying such complex damage. Full article
Open AccessProceedings Inverse Analysis for Estimating Temperature and Residual Stress Distributions in a Pipe from Outer Surface Temperature Measurement and Its Regularization
Proceedings 2018, 2(8), 407; https://doi.org/10.3390/ICEM18-05284
Published: 30 May 2018
PDF Full-text (937 KB)
Abstract
This paper presents an inverse analysis method for estimating the temperature and thermal residual stress distributions in the pipe from the temperature history measured on the outer surface. A regularization method was introduced. It is found from numerical simulations that the proposed inverse
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This paper presents an inverse analysis method for estimating the temperature and thermal residual stress distributions in the pipe from the temperature history measured on the outer surface. A regularization method was introduced. It is found from numerical simulations that the proposed inverse analysis method with regularization is useful for obtaining a reasonable estimate of the inner surface temperature and thermal stress. Full article
Open AccessProceedings Novel Experimental Design for Two-Dimensional Delamination in Fiber-Reinforced Polymer Laminates
Proceedings 2018, 2(8), 408; https://doi.org/10.3390/ICEM18-05283
Published: 30 May 2018
PDF Full-text (2463 KB)
Abstract
The two-dimensional (2D) delamination behavior of composite laminates under quasi-static out-of-plane opening loads has been experimentally investigated. A novel design and experimental set-up for fiber-reinforced polymer (FRP) laminated plates with a circular embedded pre-crack was developed. Increasing load-displacement curves were obtained due to
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The two-dimensional (2D) delamination behavior of composite laminates under quasi-static out-of-plane opening loads has been experimentally investigated. A novel design and experimental set-up for fiber-reinforced polymer (FRP) laminated plates with a circular embedded pre-crack was developed. Increasing load-displacement curves were obtained due to the increasing crack front length during propagation. Throughout the loading process, stiffening and softening mechanisms were activated. The stretching of delaminated part of the laminates constituted the main stiffening mechanism. Once the crack started growing, a corresponding softening due to crack propagation occurred together with a secondary stiffening mechanism, fiber-bridging. These stiffness-related mechanisms were reflected in the compliance. Full article
Open AccessProceedings Effect of the Nitrogen Diffusion Layer Formed by Gas Blow Induction Heating Nitriding on Wear Resistance and Fatigue Properties of Titanium Alloy
Proceedings 2018, 2(8), 409; https://doi.org/10.3390/ICEM18-05285
Published: 30 May 2018
PDF Full-text (1268 KB)
Abstract
The effect of the nitrogen diffusion layer formed by gas blow induction heating nitriding on the wear resistance and the fatigue properties of a titanium alloy was investigated. The nitrogen diffusion layer deteriorated the wear resistance of a titanium alloy. This is probably
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The effect of the nitrogen diffusion layer formed by gas blow induction heating nitriding on the wear resistance and the fatigue properties of a titanium alloy was investigated. The nitrogen diffusion layer deteriorated the wear resistance of a titanium alloy. This is probably because hard abrasive particles worn from the diffusion layer accelerates the wear of the material. In contrast, the diffusion layer improved the fatigue properties of a titanium alloy. This is due to the high hardness of the diffusion layer, and because the layer and the substrate share the same elastic modulus, the surface stress concentration is inhibited. Full article
Open AccessProceedings Finite Element Modelling of Cardiac Ischemia and Data Mining Application for Ischemic Detection and Localization
Proceedings 2018, 2(8), 410; https://doi.org/10.3390/ICEM18-05269
Published: 24 May 2018
PDF Full-text (1387 KB)
Abstract
The main aim of this paper was to computationally simulate the cardiac ischemia employing Finite Element Method (FEM) and detect its presence and localization using data mining approach. A simplified heart-torso model was created based on computed tomography (CT) images, with performed segmentation
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The main aim of this paper was to computationally simulate the cardiac ischemia employing Finite Element Method (FEM) and detect its presence and localization using data mining approach. A simplified heart-torso model was created based on computed tomography (CT) images, with performed segmentation of the heart (17 zones). Ischemic and non-ischemic cardiac beats were simulated in different zones with aim to create a virtual database which was used for data mining. Using the virtual database, we trained several classifiers and tested them for the purpose of ischemic beat detection based on the body surface potentials map (BSPM). If the ECG is classified as ischemic by the first stage classifier, potentials were processed by the second stage data mining model, which predicted the location of the ischemic area. The use of the second stage classifier, which located the ischemia in one of the heart’s segments created in the FEM model, goes beyond the current state of the art. Thus, the proposed approach is improved solution which can instantly allow clinicians to implement an adequate treatment strategy in future. Full article
Open AccessProceedings Investigations of Cruciform Specimen Designs for Biaxial Tensile Testing of SMC
Proceedings 2018, 2(8), 411; https://doi.org/10.3390/ICEM18-05279
Published: 31 May 2018
PDF Full-text (702 KB)
Abstract
This proceedings paper presents the investigation of different cruciform specimen designs for the characterization of Sheet Molding Compounds under biaxial loading. Biaxial tensile tests allow the investigation of damage evolution under multiaxial stress states, which is particularly interesting due to the different damage
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This proceedings paper presents the investigation of different cruciform specimen designs for the characterization of Sheet Molding Compounds under biaxial loading. Biaxial tensile tests allow the investigation of damage evolution under multiaxial stress states, which is particularly interesting due to the different damage phenomena in composite materials. A key challenge is to find a suitable specimen shape, because typical cruciform specimens fail in the arms before damage occurs in the area of interest which is the area of the biaxial stress state in the center region of the specimen. For all of the introduced designs the stiffness degradation is analyzed more in detail and compared to that of a uniaxial bone specimen. For the best performing specimen which is reinforced by unidirectional reinforced tapes on the arms, the strain field is analyzed by finite element simulations, taking into account the mechanical properties of the different layers of the specimen. Especially in the center area and at critical points, strain concentrations and non-symmetrical strain distributions are analyzed and evaluated. Full article
Open AccessProceedings Rigid–Flexible Contact Analysis of an Inflated Membrane Balloon with Various Contact Conditions
Proceedings 2018, 2(8), 412; https://doi.org/10.3390/ICEM18-05264
Published: 24 May 2018
PDF Full-text (653 KB)
Abstract
Considering the Mooney–Rivlin hyperelastic model, a semi-analytical approach is introduced to analyze the rigid–flexible contact behavior of an inflated membrane balloon between two plates with various interface conditions. This approach is based on differential formulation, and the coupling properties of equilibrium equations are
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Considering the Mooney–Rivlin hyperelastic model, a semi-analytical approach is introduced to analyze the rigid–flexible contact behavior of an inflated membrane balloon between two plates with various interface conditions. This approach is based on differential formulation, and the coupling properties of equilibrium equations are well-solved. In order to verify the reliability of the proposed theoretical model, an experimental test was designed, by which some important contact characteristics and patterns (no-slip condition) were obtained. Two special phenomena were observed for the meridian stretch ratio with different friction coefficients. One is that the intersection points of all curves fall in a small interval, and the intersection of any two curves represents the same changing rate of the horizontal ordinate, resulting in the maximum difference. The other is the dividing point, where the stretch ratio decreases on the left and increases on the right due to the introduction of friction. These results provide solid guidance and support for our understanding of the rigid–flexible contact behavior of inflated membrane balloons. Full article
Open AccessProceedings In-Situ Experimental Modal Testing of Railway Bridges
Proceedings 2018, 2(8), 413; https://doi.org/10.3390/ICEM18-05286
Published: 30 May 2018
PDF Full-text (1772 KB)
Abstract
In this paper the potential application of experimental modal testing of railway bridges by application of the forced vibration excitation method is proposed to identify reliable and reproduceable values of the natural frequencies and damping coefficients. It will be shown, that the damping
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In this paper the potential application of experimental modal testing of railway bridges by application of the forced vibration excitation method is proposed to identify reliable and reproduceable values of the natural frequencies and damping coefficients. It will be shown, that the damping values that are determined by in-situ experimental modal testing are in most cases significant higher than the values given in EN 1991-2 and that the normative damping values are quite conservative. The measuring results of a framed concrete bridge with 16.1 m span length are presented and the dependence of dynamic parameters to seasonable temperature changes and to the size of bridge vibration amplitude will be discussed in detail. Full article
Open AccessProceedings Mechanical Behaviour of Clinched Joints in Configurations
Proceedings 2018, 2(8), 414; https://doi.org/10.3390/ICEM18-05280
Published: 31 May 2018
PDF Full-text (687 KB)
Abstract
Clinch joining or clinching is a mechanical joining technique for sheet material. In this paper, the mechanical behaviour of multiple clinched joints under mixed-mode loads (peel, shear and pull-out) is investigated using a modified Arcan test. The experimental results are compared with a
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Clinch joining or clinching is a mechanical joining technique for sheet material. In this paper, the mechanical behaviour of multiple clinched joints under mixed-mode loads (peel, shear and pull-out) is investigated using a modified Arcan test. The experimental results are compared with a proposed equivalent model for clinched joints to validate if the model can reproduce the deformation behaviour up to maximum force. The theoretical maximum resistance force of the configurations are then compared to the experimental maximum resistances to investigate the influence of interaction effects on the maximum strength of the configuration. This study is part of a global design strategy for clinched joints in large structures. Full article
Open AccessProceedings Numerical Investigations on the Fatigue Life of Lean Duplex Transverse Stiffeners in Bridges
Proceedings 2018, 2(8), 415; https://doi.org/10.3390/ICEM18-05278
Published: 28 May 2018
PDF Full-text (849 KB)
Abstract
Numerical fatigue assessment of welded joints can be done using several approaches. The structural hot spot stress (SHSS) method based on finite element (FE) analysis is considered an effective approach when complex geometries or loading conditions exist. However, in the case of numerical
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Numerical fatigue assessment of welded joints can be done using several approaches. The structural hot spot stress (SHSS) method based on finite element (FE) analysis is considered an effective approach when complex geometries or loading conditions exist. However, in the case of numerical evaluation of the SHSS, the results can differ significantly depending on the FE modelling parameters. In the present paper, the sensitivity of the SHSS to several of these parameters is investigated numerically on one selected critical fatigue-prone detail, namely a transverse weld attachment, in a stainless steel bridge. In parallel a static tensile test performed on the same welded stainless steel detail is presented to measure the SHSS. The strain field near the welded area is measured with digital image correlation (DIC). The experimentally measured and numerically computed SHSS as well as the deduced fatigue lives are then compared and the sources of discrepancy discussed. Full article
Open AccessProceedings Nondestructive Damage Detection of a Magnetostrictive Composite Structure
Proceedings 2018, 2(8), 416; https://doi.org/10.3390/ICEM18-05276
Published: 28 May 2018
PDF Full-text (558 KB)
Abstract
The integrity of composite structures gradually degrades due to the onset of damage such as matrix cracking, fiber/matrix debonding, and delamination. Over the last two decades, great strides have been made in structural health monitoring (SHM) community using various sensing techniques such as
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The integrity of composite structures gradually degrades due to the onset of damage such as matrix cracking, fiber/matrix debonding, and delamination. Over the last two decades, great strides have been made in structural health monitoring (SHM) community using various sensing techniques such as acoustic emission, eddy current, strain gages, etc., to diagnose damage in aerospace, mechanical and civil infrastructures. Embedded sensing offers the prospects of providing for real-time, in-service monitoring of damage were weight savings is a major factor in Aerospace Industry. In this present work, magnetostrictive particles such as Terfenol-D were embedded in a composite structure, along with multiple SHM techniques, to capture the damage in an IM7-carbon fiber reinforced polymer composite system undergoing fatigue loading. As the internal stress state increases, the change in the magnetization flux intensity was captured using a non-contact magnetic field sensor. A damage diagnosis system was established along with an acoustic emissions technique to further validate the damage captured by the embedded system. The goal of this project is to identify the change in the mechanical and magnetic property within a composite material during the evolution of damage. Several characterization techniques were used to determine interfacial fiber-matrix interactions which will provide for a more comprehensive understanding of the composite interfaces. Full article
Open AccessProceedings Experimental Characterization of Bond Fatigue Using Beam-End Tests with Push-In Loading
Proceedings 2018, 2(8), 417; https://doi.org/10.3390/ICEM18-05270
Published: 24 May 2018
PDF Full-text (826 KB)
Abstract
Realistic characterization of fatigue loading resistance is a paramount for an economical and reliable structural design of reinforced concrete (RC) and prestressed concrete (PC) structures. The need for innovative experimental methods for the characterization of fatigue behavior is driven by the current aims
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Realistic characterization of fatigue loading resistance is a paramount for an economical and reliable structural design of reinforced concrete (RC) and prestressed concrete (PC) structures. The need for innovative experimental methods for the characterization of fatigue behavior is driven by the current aims to construct wind turbine towers that must resist up to N = 107 loading cycles corresponding to 25 years of service life. Considering the number of possible configurations with regard to structural geometries, cross-sectional layout of reinforcement and loading scenarios, experimental data are required that capture the key mechanisms driving the fatigue damage between the reinforcement and concrete matrix. Experimental investigations of bond behavior under fatigue loading have been reported in the literature in the 90′s of last century. Since then, no systematic investigation of bond fatigue behavior has been published. As a consequence, no assessment rules are available for the bond fatigue, only separate assessment rules for concrete and steel. The present paper will report on the ongoing research of bond fatigue behavior using the beam-end test setup. The test campaign includes the push-in loading with the goal to provide data characterizing the compressive behavior of reinforced cross sections in wind turbine towers. Full article
Open AccessProceedings Development of Delamination Detection System for Concrete Decks by Using Convolutional Neural Network
Proceedings 2018, 2(8), 418; https://doi.org/10.3390/ICEM18-05281
Published: 28 May 2018
PDF Full-text (773 KB)
Abstract
Bridges in Japan, especially those managed by municipalities, deteriorate over time. Due to lack of civil engineers in municipalities, appropriate and automated assistance for degradation judgement is thought to be important for the concerned authorities. Automated judgement systems for some types of damage
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Bridges in Japan, especially those managed by municipalities, deteriorate over time. Due to lack of civil engineers in municipalities, appropriate and automated assistance for degradation judgement is thought to be important for the concerned authorities. Automated judgement systems for some types of damage (e.g., cracks) started to be developed by geometrical approaches. Yet, there is no comprehensive method to detect more complicated types of damage, such as delamination, for regular inspection. This research aims to develop a delamination-detection system which identifies the location of the damage. Images with delaminated parts were provided by Niigata Prefecture (in Japan), and annotation of the location of delamination and/or rebar exposure was conducted. Fully Convolutional Network (FCN), one of the deep learning networks for pixel-to-pixel segmentation, was used to detect the areas of the delamination and rebar exposure. The result of the training aided by FCN showed a good agreement with the result with the naked eye. The soundness, judged based on the FCN result according to the inspection code of Niigata Prefecture, was close to the soundness judgement at the site. These outcomes support the reliability of the system to detect delamination and rebar exposure in manual inspection. This technology is expected to be used in bridges’ inspection at municipalities, which have a lack of inspection engineers. Full article
Open AccessProceedings Characterization of the Bond between Textile Reinforced Cement and Extruded Polystyrene by Shear Tests
Proceedings 2018, 2(8), 419; https://doi.org/10.3390/ICEM18-05275
Published: 27 May 2018
PDF Full-text (863 KB)
Abstract
Loadbearing sandwich panels used as wall elements are a promising development since they combine structural and energy efficiency. Composite behaviour needs to be ensured so that the sandwich panel works as one element under a flexural load (meaning that the shear forces due
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Loadbearing sandwich panels used as wall elements are a promising development since they combine structural and energy efficiency. Composite behaviour needs to be ensured so that the sandwich panel works as one element under a flexural load (meaning that the shear forces due to bending are transferred from one face to the other). To assure this full composite behaviour, an investigation of the bond strength between the faces and the core of the sandwich panel is necessary. Therefore, two different bond test set-ups were performed on sandwich panels with Textile Reinforced Cement (TRC) faces and an Extruded Polystyrene (XPS) insulating foam core. The two bond test set-ups were compared and revealed that one of the set-ups showed a combination of bond and shear failure of the core so that a clear conclusion on the bond strength couldn’t be obtained. The second set-up showed clear bond failure and gave a good estimation of the bond strength between TRC and XPS. Full article
Open AccessProceedings Biaxial Compression Tests on Hopkinson Bars
Proceedings 2018, 2(8), 420; https://doi.org/10.3390/ICEM18-05263
Published: 24 May 2018
PDF Full-text (985 KB)
Abstract
A biaxial compression Hopkinson bar set-up bas been designed. It consists in a projectile, an input bar and two co-axial output bars. After the projectile impact on the input bar, the internal output bar measures the axial loading of the cross sample whereas
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A biaxial compression Hopkinson bar set-up bas been designed. It consists in a projectile, an input bar and two co-axial output bars. After the projectile impact on the input bar, the internal output bar measures the axial loading of the cross sample whereas the external output bar measures its transversal loading via a mechanism with sliding surfaces. Gauges glued on the bars enable stain measurements which lead to the forces and to the displacements on the interfaces between the bars and the mounting. The displacement field of the sample is obtained by high-speed imaging and by digital image correlation. Experiments show that the set-up works despites two disadvantages. Firstly, the transversal force in the sample is over-estimated because of the friction in the mechanism. Moreover, comparisons between the displacements on the bars interfaces and the sample displacement field display that the clearance have an influence on the sample loading. Full article
Open AccessProceedings Combined ND Techniques for Structural Assessment: The Case of Historic Nepali Constructions after the 2015 Gorkha Earthquake
Proceedings 2018, 2(8), 421; https://doi.org/10.3390/ICEM18-05271
Published: 27 May 2018
PDF Full-text (2669 KB)
Abstract
Combined non-destructive in situ techniques—namely sonic tests and ambient vibration measurements—are applied on two Nepali Pagoda temples damaged by the 2015 Gorkha earthquake, providing the dynamic elastic modulus of masonry and the buildings’ frequencies Full article
Open AccessProceedings A Novel Geometry for Shear Test Using Axial Tensile Setup
Proceedings 2018, 2(8), 422; https://doi.org/10.3390/ICEM18-05277
Published: 28 May 2018
PDF Full-text (1807 KB)
Abstract
This paper studies a novel geometry for the in-plane shear test performed with an axial electromechanical testing machine. In order to investigate the influence of the triaxiality rate on the mechanical behavior, different tests will be performed on the studied material: simple tensile
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This paper studies a novel geometry for the in-plane shear test performed with an axial electromechanical testing machine. In order to investigate the influence of the triaxiality rate on the mechanical behavior, different tests will be performed on the studied material: simple tensile tests, large tensile tests and shear tests. For the whole campaign, a common equipment should be employed to minimize the impact of the testing device. As a consequence, for the shear tests, the geometry of the specimen must be carefully designed in order to adapt the force value and make it comparable to the one obtained for the tensile tests. Like most of the existing shear-included tensile test specimens, the axial loading is converted to shear loading at a particular region through the effect of geometry. A symmetric shape is generally preferred, since it can restrict the in-plane rotation of the shear section, keep shear increasing in a more monotonic path and double the force level thanks to the two shear zones. Due to the specific experimental conditions, such as dimensions of the furnace and the clamping system, the position of the extensometer or the restriction of sheet thickness (related to the further studies of size effect at mesoscale and hot temperature), several geometries were brought up and evaluated in an iterative procedure via finite element simulations. Both the numerical and experimental results reveal that the final geometry ensures some advantages. For instance, a relatively low triaxiality in the shear zone, limited in-plane rotation and no necking are observed. Moreover, it also prevents any out-of-plane displacement of the specimen which seems to be highly sensitive to the geometry, and presents a very limited influence of the material and the thickness. Full article
Open AccessProceedings Elasticity Constants of a Two-Phase Tungsten Thin Film
Proceedings 2018, 2(8), 423; https://doi.org/10.3390/ICEM18-05272
Published: 27 May 2018
PDF Full-text (477 KB)
Abstract
The IET was used to determine the macroscopic elasticity constants of the multiphase coating. In order to determine the macroscopic elasticity constants of the film firstly, a critical assessment of Young’s modulus determination was done by comparing all the models proposed in the
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The IET was used to determine the macroscopic elasticity constants of the multiphase coating. In order to determine the macroscopic elasticity constants of the film firstly, a critical assessment of Young’s modulus determination was done by comparing all the models proposed in the literature. The best model was identified and a study was performed to identify and quantify the most influent factors on the global uncertainty. Secondly, an enhanced formulation to determine the shear modulus of coating by IET was developed. The methodology was applied on a tungsten thin film deposited by DC magnetron sputtering. Full article
Open AccessProceedings Experimental Investigation on the Explosive Substitute by Drop Test
Proceedings 2018, 2(8), 424; https://doi.org/10.3390/ICEM18-05296
Published: 5 June 2018
PDF Full-text (1544 KB)
Abstract
The drop tests of the experimental structure with explosive substitute material were carried out to study the dynamic deformation and failure of the explosive substitute. The PBX simulation material was designed as a cylindrical flat head structure, with the support structure of the
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The drop tests of the experimental structure with explosive substitute material were carried out to study the dynamic deformation and failure of the explosive substitute. The PBX simulation material was designed as a cylindrical flat head structure, with the support structure of the PBX simulation material as an aluminum support ring, and with an affixed counterweight to the upper part of the PBX simulation material. The PBX simulation materials, the counterweight and the support ring, were glued together to form the drop test pieces. A special drop test system was designed, which realized the non-deflection of the falling posture of the drop test pieces and that the drop was pure free. The results show that in the drop impact tests, the critical height of the explosive simulant failure is about 600 mm to 700 mm when the counterweight of 19.62 kg is used. Full article
Open AccessProceedings Robotic Welding Tests MIG Standard and CMT+P in Aluminum Alloy 6082-T6 for Optimization of Penetration, Cord Width and Reinforcement
Proceedings 2018, 2(8), 425; https://doi.org/10.3390/ICEM18-05295
Published: 5 June 2018
PDF Full-text (624 KB)
Abstract
The present article describes an experimental analysis of a robotized Gas Metal-arc Welding (GMAW) in aluminum alloy, using Metal Inert Gas (MIG) in its transfer method variation Standard and pulsed Cold Metal Transfer (CMT+P), developed in order to optimize the penetration depth, width
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The present article describes an experimental analysis of a robotized Gas Metal-arc Welding (GMAW) in aluminum alloy, using Metal Inert Gas (MIG) in its transfer method variation Standard and pulsed Cold Metal Transfer (CMT+P), developed in order to optimize the penetration depth, width and reinforcement of the weld bead. The base metal was the aluminum alloy 6082-T6 and the filler metal was aluminum alloy 5754. Full article
Open AccessProceedings Optimization of Robotized Welding in Aluminum Alloys with Pulsed Transfer Mode Using the Taguchi Method
Proceedings 2018, 2(8), 426; https://doi.org/10.3390/ICEM18-05294
Published: 8 June 2018
PDF Full-text (471 KB)
Abstract
In order to obtain an optimal combination of welding parameters to weld an aluminum alloy (6082-T6) with MIG (Metal Inert Gas) it was used an L27 Taguchi orthogonal array. The array originated 27 different combinations that gives rise to 27 welding programs for
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In order to obtain an optimal combination of welding parameters to weld an aluminum alloy (6082-T6) with MIG (Metal Inert Gas) it was used an L27 Taguchi orthogonal array. The array originated 27 different combinations that gives rise to 27 welding programs for the metal pulsed spray mode. The welds were made in aluminum bars using an industrial robot. All welds were repeated three times to ensure string repeatability. Metallographic tests were performed on the weld beads for measuring the width bead, penetration and reinforcement. Measurement data was analyzed for signal/noise and analysis of variance (ANOVA). Applying the Taguchi’s method, an optimal combination of welding parameters was reached. Full article
Open AccessProceedings Blast Loading of Concrete Pipes Using C-4 Charges
Proceedings 2018, 2(8), 428; https://doi.org/10.3390/ICEM18-05292
Published: 8 June 2018
PDF Full-text (970 KB)
Abstract
The E39 coastal highway route in Norway is envisioned a future without ferries. A submerged floating tunnel built in concrete has been suggested as a means of crossing wide and deep fjords. Blast loading against this type of structure could have disastrous consequences,
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The E39 coastal highway route in Norway is envisioned a future without ferries. A submerged floating tunnel built in concrete has been suggested as a means of crossing wide and deep fjords. Blast loading against this type of structure could have disastrous consequences, and potentially cause the collapse of the entire structure. To investigate the response of tubular concrete structures subjected to blast loading, standard off-the-shelf unreinforced concrete pipes were tested using live explosives. A plastic explosive was used to generate the load, and the tests were filmed by two synchronised high-speed cameras. Three pressure sensors equidistant from the charge position logged the pressure. Further, three different positions for the charges were used to investigate the effect of charge position. The charge size was varied for each position to find the amount of explosives needed to breach the pipe. It was found that a contact charge detonated from the outside requires almost twice the explosive amount to breach the pipe than a contact charge detonated from the inside, suggesting a significant confinement effect. Numerical simulations using finite elements produced good qualitative results. Full article
Open AccessProceedings Experimental Investigation on Crack Growth in Pre-Notched Concrete Beams
Proceedings 2018, 2(8), 429; https://doi.org/10.3390/ICEM18-05287
Published: 1 June 2018
PDF Full-text (2447 KB)
Abstract
It is well-known that failure of unreinforced, pre-notched concrete beams in bending is mainly governed by the tensile strength (“ductile” behaviour) or by the fracture toughness (brittle behaviour) depending on the geometrical scale (beam size), and the value of the relative notch depth.
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It is well-known that failure of unreinforced, pre-notched concrete beams in bending is mainly governed by the tensile strength (“ductile” behaviour) or by the fracture toughness (brittle behaviour) depending on the geometrical scale (beam size), and the value of the relative notch depth. In particular, relatively large beams made of high-strength concrete and with a small relative notch depth, show a brittle structural behaviour (unstable crack propagation); whereas relatively small beams made of low-strength concrete and with a large relative notch depth, show a relatively ductile structural behaviour (stable crack propagation). In this contribution, the damage progress, due to crack formation and propagation, in unreinforced, pre-notched concrete beam specimens, tested in three-point bending, is analysed by the Acoustic Emission (AE) and Digital Image Correlation (DIC) techniques. Beams with rectangular cross-section were considered. A relative notch depth (a/d) equal to 0.5 is assumed in all cases. The loading process was operated by controlling the vertical displacement. The specimens were instrumented by four transducers measuring the vertical displacements in correspondence to the supports and at mid-span, and the Crack Mouth Opening Displacement (CMOD). In addition, two AE transducers were located near the notch to acquire the AE signals originated by material damage. Moreover, the evolution of the deformation process was monitored around the notch by a DIC system, therefore obtaining the time evolution of strains. By analysing the acquired data, a correlation between the AE signals registered and the displacements/strains measured at several points was looked for. Furthermore, the fracture energy of each specimen was evaluated, according to RILEM recommendation, based on the measured load–deflection curves. Scale effects on fracture energy, bending strength, and AE energy per unit area were investigated. Full article
Open AccessProceedings Digital Image Correlation Measurements of Mode I Fatigue Delamination in Laminated Composites
Proceedings 2018, 2(8), 430; https://doi.org/10.3390/ICEM18-05289
Published: 4 June 2018
PDF Full-text (993 KB)
Abstract
A Digital Image Correlation (DIC) based method is proposed to characterize Mode I fatigue delamination onset and propagation in laminated composites. With the help of DIC, the displacement field around a delamination crack is obtained and further processed to determine the position of
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A Digital Image Correlation (DIC) based method is proposed to characterize Mode I fatigue delamination onset and propagation in laminated composites. With the help of DIC, the displacement field around a delamination crack is obtained and further processed to determine the position of the crack tip. With this method the delamination length can be measured automatically in each cycle with a precision on the order of few hundreds of micrometers. The fatigue delamination onset life is then determined by detecting the increase of the delamination length, and the fatigue delamination propagation rate is calculated. The proposed method produces more conservative fatigue life measurements in comparison with the compliance increase method in ASTM D6115. Full article
Open AccessProceedings Experimental Study on the Strength of Stainless Steel Fillet Welds
Proceedings 2018, 2(8), 431; https://doi.org/10.3390/ICEM18-05290
Published: 8 June 2018
PDF Full-text (500 KB)
Abstract
This paper describes 18 tensile tests performed on welded specimens made of 3 stainless steel grades: EN 1.4307 (304L) and EN 1.4404 (316L) austenitic grades and EN 1.4062 duplex grade. For each grade, 3 tests were carried out parallel to the weld causing
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This paper describes 18 tensile tests performed on welded specimens made of 3 stainless steel grades: EN 1.4307 (304L) and EN 1.4404 (316L) austenitic grades and EN 1.4062 duplex grade. For each grade, 3 tests were carried out parallel to the weld causing shear stresses (in the weld throat plane, parallel to the weld throat axis) and 3 tests along the transverse direction, perpendicular to the weld, causing a combination of normal (perpendicular to the weld throat plane) and shear (in the weld throat plane, perpendicular to the weld throat axis) stresses. The digital image correlation (DIC) technique was used to measure the fracture surface. Based on these experiments, an assessment of the current design rules was made. Full article
Open AccessProceedings Use of Spectral Entropy for Damage Detection in Masonry Buildings in the Presence of Mild Seismicity
Proceedings 2018, 2(8), 432; https://doi.org/10.3390/ICEM18-05288
Published: 4 June 2018
PDF Full-text (1721 KB)
Abstract
The seismic events that struck central Italy in 2016 caused severe damage to a wide range of buildings and infrastructures. Masonry buildings were particularly affected, even for low values of peak ground acceleration. In this paper, the data recorded for three masonry buildings
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The seismic events that struck central Italy in 2016 caused severe damage to a wide range of buildings and infrastructures. Masonry buildings were particularly affected, even for low values of peak ground acceleration. In this paper, the data recorded for three masonry buildings belonging to the Seismic Observatory of Structures (OSS) network are used to detect their seismic damage by means of Spectral Entropy (SE). However, entropy measures are sensitive to the energy inserted in the system, since an input of energy can lead to a more deterministic behavior of the structure and thus to a reduction of the entropy indicator. When non-stationary time series are used to evaluate the presence of damage (e.g. mild seismicity) the entropy of the system could be underestimated, leading to misleading results. For these reasons, in this paper an indicator based on SE is proposed to assess the occurrence of damage also in the presence of mild seismicity. Full article
Open AccessProceedings Evaluation of Crack Repair Effect for RC Slab Using AE Tomography
Proceedings 2018, 2(8), 433; https://doi.org/10.3390/ICEM18-05331 (registering DOI)
Published: 11 June 2018
PDF Full-text (1919 KB)
Abstract
Three reinforced concrete (RC) slab-panels are repaired by using the crack injection method. This is because web-shaped crack networks are observed after 46 years in service. In the present research, an attempt is made to confirm the effectiveness of the repair by comparing
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Three reinforced concrete (RC) slab-panels are repaired by using the crack injection method. This is because web-shaped crack networks are observed after 46 years in service. In the present research, an attempt is made to confirm the effectiveness of the repair by comparing the velocity distribution of elastic waves obtained from Acoustic Emission (AE) tomography analysis, before and after the repair. Thus, the velocity recoveries due to injection are found in all of the slab panels, and it is confirmed that the elastic wave velocities obtained using this technique can serve as an indicator for examining the state of crack and void filling with injected material. Further, a good correlation is found between the low-velocity region before repair and the amount of injection. These results show the potential of the AE tomography technique to be used as a method for estimating the effect of injection repair. Full article
Open AccessProceedings Towards a Phased Array Based Ultrasonic Polar Scan: Simulation Study and Comparison with Plane Wave Results
Proceedings 2018, 2(8), 435; https://doi.org/10.3390/ICEM18-05327 (registering DOI)
Published: 11 June 2018
PDF Full-text (1068 KB)
Abstract
The ever-increasing use of composite materials in the industry has resulted in the need for new, intricate approaches to not only properly characterize their anisotropic mechanical properties (i.e., the visco-elastic tensor), but also to detect various types of internal flaws. Both goals can
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The ever-increasing use of composite materials in the industry has resulted in the need for new, intricate approaches to not only properly characterize their anisotropic mechanical properties (i.e., the visco-elastic tensor), but also to detect various types of internal flaws. Both goals can be achieved by the Ultrasonic Polar Scan (UPS). During an UPS experiment, a material spot is insonified at many oblique incidence angles Ψ(θ,φ), with θ the vertical incident angle and φ the in-plane polar angle, after which the reflected or transmitted ultrasound signal is recorded. The resulting dataset provides an integral view of the angle-dependent reflection (R) and transmission (T) scatter coefficients, and can be employed to infer the material properties. Although the current UPS scanner provides highly accurate experimental data, it is impractical for in-situ measurements. In order to create a more compact and practical measuring device, we propose the use of a hemispherical phased array, consisting of small piezoelectric elements, to generate a broadband, quasi plane wave signal. It will be shown, based on simulations, that a circular phased array concept allows for the determination of the reflection coefficients in θ f space, from which the dispersion curves can be immediately inferred. Comparison of these results with the plane wave theoretical results show an excellent agreement. Full article
Open AccessProceedings Experimental Analysis of CFRP Strengthened Reinforced Concrete Slabs Loaded by Two Independent Explosions
Proceedings 2018, 2(8), 436; https://doi.org/10.3390/ICEM18-05317 (registering DOI)
Published: 11 June 2018
PDF Full-text (1079 KB)
Abstract
The use of carbon fiber reinforced polymer (CFRP) as an externally bonded reinforcement (EBR) for the strengthening of reinforced concrete (RC) structures loaded by a blast wave is confirmed as an efficient solution. This observation is complementary to other advantages of CFRP such
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The use of carbon fiber reinforced polymer (CFRP) as an externally bonded reinforcement (EBR) for the strengthening of reinforced concrete (RC) structures loaded by a blast wave is confirmed as an efficient solution. This observation is complementary to other advantages of CFRP such as high tensile strength, light weight and durability. This paper discusses the behavior of CFRP as EBR in the event that two successive independent blast loads are applied on the same target. The main problems are the lack of knowledge regarding the failure modes of the CFRP strips under high strain rate and the blast response of the retrofitted structures when total debonding of the CFRP strips occurs. Four simply supported slabs with different EBR but with the same bond contact surface are tested using an explosive driven shock tube (EDST) to generate the blast wave. Digital image correlation (DIC) is used to measure the strain evolution in the concrete and the CFRP strips during the first explosion. The results show that for the first explosion, EBR increases the flexural strength and stiffness of the RC slabs. In the second explosion, total debonding of the CFRP strips occurs which initiates from the midspan of the slabs towards the supports. When the total debonding of the CFRP strips occurs, the strain distribution in the steel rebars are the same for all slabs regardless of the quantity of applied EBR. Full article
Open AccessProceedings Comparison of Non-Destructive Techniques for Impact Damage Area Assessment in Aramid/Epoxy Composites
Proceedings 2018, 2(8), 437; https://doi.org/10.3390/ICEM18-05320
Published: 11 June 2018
PDF Full-text (669 KB)
Abstract
This research focused on the assessment of the damaged area on aramid/epoxy composites subjected to high velocity impact. Digital X-ray radiography and active pulsed thermography techniques were used for performing post-mortem analysis of the impacted specimens (8 to 28 aramid layers). Two types
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This research focused on the assessment of the damaged area on aramid/epoxy composites subjected to high velocity impact. Digital X-ray radiography and active pulsed thermography techniques were used for performing post-mortem analysis of the impacted specimens (8 to 28 aramid layers). Two types of projectiles were used: 9 mm Luger FMJ and 0.357 Magnum FMJ. Two types of dedicated algorithms were developed to post-process the thermograms obtained and the results are compared with the damaged diameter measured directly on the X-ray radiographs. The output of the three methods are therefore compared and discussed. Full article
Open AccessProceedings Effect of Loading Pattern on Fatigue Behavior of Laminated Composites
Proceedings 2018, 2(8), 438; https://doi.org/10.3390/ICEM18-05321
Published: 12 June 2018
PDF Full-text (1018 KB)
Abstract
The effect of load interruptions on the fatigue behavior of (±45)2s angle-ply glass/epoxy composite laminates was investigated in this work. Constant amplitude fatigue experiments were performed at different stress levels to derive base line fatigue data. In addition, interrupted-fatigue experiments were performed
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The effect of load interruptions on the fatigue behavior of (±45)2s angle-ply glass/epoxy composite laminates was investigated in this work. Constant amplitude fatigue experiments were performed at different stress levels to derive base line fatigue data. In addition, interrupted-fatigue experiments were performed by removing the cyclic loading for two hours repetitively, after cycling for 20% of the fatigue life achieved under continuous loading at the same maximum cyclic stress level. The specimens loaded under interrupted fatigue exhibited longer fatigue live than those continuously loaded until failure. Full article
Open AccessProceedings Excitation Source Optimisation for Active Thermography
Proceedings 2018, 2(8), 439; https://doi.org/10.3390/ICEM18-05325 (registering DOI)
Published: 11 June 2018
PDF Full-text (528 KB)
Abstract
In active thermography, the use of an optimised excitation source can simplify the interpretation of measurement results. Our custom designed source, especially designed for dynamic line scanning thermography, minimises the needed excitation power and the biasing side effects generated by a wide-range heat
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In active thermography, the use of an optimised excitation source can simplify the interpretation of measurement results. Our custom designed source, especially designed for dynamic line scanning thermography, minimises the needed excitation power and the biasing side effects generated by a wide-range heat source. The source is redesigned, starting from a regular heat source, to focus the available energy such that the needed heating power is provided in a small band. Ray tracing software is used to design absorbers and reflectors to focus the electromagnetic radiation as well as the heat in a thin line. The most optimal design is manufactured and validated on a laminated test sample. The acquired thermographic data are then compared to the data captured in the old-fashioned way with widely available excitation sources. The redesign is also tested on durability and practical use to make sure that it is easy to handle and that it can be used as a long-term solution. Experienced inspectors evaluated the ease of use of it in comparison to the existing sources. A redesigned excitation source minimises the generated biasing side-effects resulting in more energy efficient and safer measurements. Full article
Open AccessProceedings Assessment of Environmental Effects for Vibration-Based Damage Detection of Historic Masonry Towers
Proceedings 2018, 2(8), 441; https://doi.org/10.3390/ICEM18-05324 (registering DOI)
Published: 11 June 2018
PDF Full-text (4514 KB)
Abstract
The paper firstly focuses on selected results obtained by continuously monitoring the dynamic response of three ancient masonry towers in Italy in order to highlight the possible effects of changing temperature on the resonant frequencies; subsequently, the removal of environmental effects (needed for
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The paper firstly focuses on selected results obtained by continuously monitoring the dynamic response of three ancient masonry towers in Italy in order to highlight the possible effects of changing temperature on the resonant frequencies; subsequently, the removal of environmental effects (needed for an effective performance assessment and damage detection) is addressed and discussed using the data acquired on a challenging historic tower. Full article
Open AccessProceedings Influence of Charge Backing on the Response of Blast Loaded Plates
Proceedings 2018, 2(8), 442; https://doi.org/10.3390/ICEM18-05312
Published: 12 June 2018
PDF Full-text (1584 KB)
Abstract
This study focuses on characterizing the transient deformation of test plates which have been exposed to air blasts arising from air-backed and metal-backed explosive detonations. Four charge masses are considered, namely 10 g, 15 g, 20 g and 25 g masses of PE4
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This study focuses on characterizing the transient deformation of test plates which have been exposed to air blasts arising from air-backed and metal-backed explosive detonations. Four charge masses are considered, namely 10 g, 15 g, 20 g and 25 g masses of PE4 plastic explosive which were moulded into cylindrical charges of a constant 38 mm diameter. The transient deformation of the test plates was captured using high speed Digital Image Correlation (DIC), which utilized two high speed cameras to record the experiments. The experimental plates exhibited plastic deformation with no tearing. The impulse imparted to the test plates increased fivefold when the charge was metal-backed. The permanent deflections from the metal-backed detonations were larger than for air, but not to the same degree as the impulse increase. Full article
Open AccessProceedings Study on the Identifiability of Material Properties Using Solely the Residual Imprint in Instrumented Indentation Experiment
Proceedings 2018, 2(8), 443; https://doi.org/10.3390/ICEM18-05316
Published: 12 June 2018
PDF Full-text (1452 KB)
Abstract
Indentation test has been widely used to determine the mechanical properties of materials. In the present work, based on our previous developed inverse computation approach, we investigated the identifiability of the plastic properties of metal materials using solely the residual imprint in instrumented
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Indentation test has been widely used to determine the mechanical properties of materials. In the present work, based on our previous developed inverse computation approach, we investigated the identifiability of the plastic properties of metal materials using solely the residual imprint in instrumented indentation. The indentation experiment was implemented on the Al 2024-t3 alloy, and result shows the experiment error exists unavoidably. To quantitatively investigate the influence of experiment error on the inverse derived material properties, the indentation simulation models were built, of which three different indenter shapes (conical, flat and spherical) and two different simulation set-ups (load or displacement control types) are considered. The sensitivity of the inverse problem in the relevant questions are systematically investigated. Results show the inverse problem formulated by the force control using a non-self-similar indenter is able to give more robust solution of the inverse derived material parameters. Besides, the numerical protocol was verified by application on the Al 2024-t3 alloy, and the plastic properties (yield stress and strain hardening exponent) obtained from indentation and uniaxial tests show good agreement. Full article
Open AccessProceedings Considerations of Failure Analysis in a Multi-Layered Composite Structure under Thermomechanical Loading
Proceedings 2018, 2(8), 447; https://doi.org/10.3390/ICEM18-05329 (registering DOI)
Published: 12 June 2018
PDF Full-text (283 KB)
Abstract
The study seeks to investigate a failure of laminated composite structure subjected to a thermomechanical loading. Failure analysis of composite structures is an important design requirement. The stacking sequence of the structure investigated is restricted to ten thin layers. The fiber orientation, stacking
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The study seeks to investigate a failure of laminated composite structure subjected to a thermomechanical loading. Failure analysis of composite structures is an important design requirement. The stacking sequence of the structure investigated is restricted to ten thin layers. The fiber orientation, stacking sequence and material properties influence the response from the composite structure. Formulas are presented which are used to estimate the response of multi-layered composite structure to thermomechanical loads. A failure analysis is performed based on some known failure criteria. The values of the engineering properties for multi-layered composite structure and the results of the stress and strain distributions subjected to the forces and bending moments are presented. The numerical results were computed by using MATLAB script. Selected results of the numerical analysis have been presented. Full article
Open AccessProceedings Experimental Techniques Synergy towards the Design of a Sensing Tool for Autonomously Healed Concrete
Proceedings 2018, 2(8), 449; https://doi.org/10.3390/ICEM18-05310
Published: 12 June 2018
PDF Full-text (700 KB)
Abstract
The first-generation of autonomously healed concrete elements is under construction: beams (SIM-SECEMIN project, Flanders Belgium), one-way flat slabs (MeMC, VUB, Belgium) and wall panels (Materials4Life project, UK) are designed with the embedment of encapsulated repair agent. In the presence of cracks, capsules rupture
[...] Read more.
The first-generation of autonomously healed concrete elements is under construction: beams (SIM-SECEMIN project, Flanders Belgium), one-way flat slabs (MeMC, VUB, Belgium) and wall panels (Materials4Life project, UK) are designed with the embedment of encapsulated repair agent. In the presence of cracks, capsules rupture releasing the agent that fills the crack void. The released agent seals and mechanically restores the crack discontinuity. This automatic process can be repeatable using vascular networks that carry the agent and release it at different locations into concrete. The innovative design is built up following several series of laboratory-scale beam tests configured over the last decade. This paper discusses the application of numerous experimental techniques that assess the mechanical performance of autonomously healed concrete: Acoustic Emission, Ultrasound Pulse Velocity, Optical Microscopy, Digital Image Correlation, Capillary Water Absorption, Computed Tomography. The study focuses on the performance and efficiency of each method on laboratory and real-scale tests. The techniques with the most promising output are selected and combined in order to design a sensing tool that evaluates healing on real applications. Full article
Open AccessProceedings Using 3D Digital Image Correlation (3D-DIC) to Measure CTOD in a Semi-Elliptical Surface Crack
Proceedings 2018, 2(8), 451; https://doi.org/10.3390/ICEM18-05311 (registering DOI)
Published: 8 June 2018
PDF Full-text (3032 KB)
Abstract
The subsurface nature of Crack Tip Opening Displacement (CTOD) makes its direct measurement very difficult, if not impossible. During fracture toughness testing, CTOD is commonly calculated by applying a plastic hinge model using externally applied clip gauges. However, clip gauge CTOD calculations merely
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The subsurface nature of Crack Tip Opening Displacement (CTOD) makes its direct measurement very difficult, if not impossible. During fracture toughness testing, CTOD is commonly calculated by applying a plastic hinge model using externally applied clip gauges. However, clip gauge CTOD calculations merely provide information relating to the center of the defect (which is typically the most critical point, but not always). For the case of a finite-length surface defect, CTOD will be variable over the defect front. Exact knowledge of CTOD over the entire front is useful for detailed calculations, such as crack profile evolution due to ductile tearing or calculations involving interacting defects. To experimentally measure the CTOD at locations other than the center of the crack, the authors propose a technique based on full field three-dimensional profile measurement of the notched surface by means of stereoscopic Digital Image Correlation (3D-DIC). The method is based on the plastic hinge model assuming that the crack flanks rotate in a rigid manner around a plastic hinge point in the un-cracked ligament. Having measured full-field out-of-plane displacement at the surface of the specimen around the crack using the 3D-DIC method, CTOD can be inferred over the entire crack front. Results show that, due to the acceptable agreement between the DIC based calculation and CTOD measured from cast replicas, the proposed technique has a sufficient accuracy to measure CTOD on the entire crack front in plastically deforming specimens. Full article
Open AccessProceedings Investigating Hydrofracture Evolution of Quasi-Brittle Material Using a Post-Peak Control Technique Associated with Speckle-Shearing Interferometry
Proceedings 2018, 2(8), 452; https://doi.org/10.3390/ICEM18-05326
Published: 12 June 2018
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Abstract
This paper presents the experimental results obtained with a post-peak loading device of hydraulic fracture controlled by setting circumferential deformation of a specimen to be a closed-loop feedback signal during servo-water-driven and monitored with the optical technique of speckle-shearing interferometry (SSI). The macro-scale
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This paper presents the experimental results obtained with a post-peak loading device of hydraulic fracture controlled by setting circumferential deformation of a specimen to be a closed-loop feedback signal during servo-water-driven and monitored with the optical technique of speckle-shearing interferometry (SSI). The macro-scale complete loading curve obtained by the post-peak loading system indicate the stiffness, peak strength and post-peak behavior of quasi-brittle material subjected to borehole water pressure. The micro-scale out-of-plane displacement (OPD) obtained by SSI corresponding to complete loading curve was exhibited where the internal crack tip was located. The complete hydrofracture evolution from displacement continuity to displacement discontinuity was investigated. The test results provide a better understanding of the hydraulic fracture mechanism which is helpful for the development of theoretical and numerical solutions related to hydraulic fractures. Full article
Open AccessProceedings Experimental Characterization of the Self-Healing Capacity of Cement Based Materials: An Overview
Proceedings 2018, 2(8), 454; https://doi.org/10.3390/ICEM18-05322 (registering DOI)
Published: 11 June 2018
PDF Full-text (515 KB) | Supplementary Files
Abstract
This paper, prepared in the framework of the COST Action SARCOS WG2 activities (http://www.cost.eu/COST_Actions/ca/CA15202), provides an overview of the main concepts underlying the experimental characterization of the self-sealing capacity of cement-based materials. This effort intends to pave the way towards standardization of such
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This paper, prepared in the framework of the COST Action SARCOS WG2 activities (http://www.cost.eu/COST_Actions/ca/CA15202), provides an overview of the main concepts underlying the experimental characterization of the self-sealing capacity of cement-based materials. This effort intends to pave the way towards standardization of such experimental methods for a comparative assessment of the self-healing capacity of different cement-based materials and of the effectiveness of different techniques, in order to incorporate self-healing concepts and outcomes into durability-based predictive models and design approaches. Full article
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