Search Results (14)

Bolted connections are critical in deep-sea engineering, yet classical theories (such as VDI 2230) implicitly assume atmospheric pressure conditions, neglecting the volume contraction of components due to hydrostatic pressure. This fundamental flaw hinders accurate prediction of preload retention—especially when bolts and clamped components exhibit differential compressibility (a common scenario in practical applications). To bridge this scientific gap, this paper establishes the first analytical model for bolt preload under pressure-induced volumetric contraction based on deformation coordination relations. The derived closed-form expressions explicitly quantify residual preload as a function of deep-sea ambient pressure, component bulk modulus, and geometric parameters. Model predictions closely match finite element calculations, showing that stainless steel bolts clamping aluminum alloys under 110 MPa pressure can experience up to a 40% preload reduction. This theoretical framework extends classical bolt connection mechanics to high-pressure environments, providing a scientific basis for optimizing deep-sea connection designs through material matching and dimensional control to effectively mitigate pressure-induced preload loss. Full article

Computer vision in the structural health monitoring (SHM) field has become popular, especially for processing unmanned aerial vehicle (UAV) data, but still has limitations both in experimental testing and in practical applications. Prior works have focused on UAV challenges and opportunities for the vibration-based SHM of buildings or bridges, but practical and methodological gaps exist specifically for linear infrastructure systems such as pipelines. Since they are critical for the transportation of products and the transmission of energy, a feasibility study of UAV-based SHM for linear infrastructures is essential to ensuring their service continuity through an advanced SHM system. Thus, this study proposes a single UAV for the seismic monitoring and safety assessment of linear infrastructures along with their computer vision-aided procedures. The proposed procedures were implemented in a full-scale shake-table test of a natural gas pipeline assembly. The objectives were to explore the UAV potential for the seismic vibration monitoring of linear infrastructures with the aid of several computer vision algorithms and to investigate the impact of parameter selection for each algorithm on the matching accuracy. The procedure starts by adopting the Maximally Stable Extremal Region (MSER) method to extract covariant regions that remain similar through a certain threshold of image series. The feature of interest is then detected, extracted, and matched using the Speeded-Up Robust Features (SURF) and K-nearest Neighbor (KNN) algorithms. The Maximum Sample Consensus (MSAC) algorithm is applied for model fitting by maximizing the likelihood of the solution. The output of each algorithm is examined for correctness in matching pairs and accuracy, which is a highlight of this procedure, as no studies have ever investigated these properties. The raw data are corrected and scaled to generate displacement data. Finally, a structural safety assessment was performed using several system identification models. These procedures were first validated using an aluminum bar placed on an actuator and tested in three harmonic tests, and then an implementation case study on the pipeline shake-table tests was analyzed. The validation tests show good agreement between the UAV data and reference data. The shake-table test results also generate reasonable seismic performance and assess the pipeline seismic safety, demonstrating the feasibility of the proposed procedure and the prospect of UAV-based SHM for linear infrastructure monitoring. Full article

Traditionally, initial material cost has been the governing factor for material selection in structural construction. However, the growing maintenance cost of existing infrastructure has demanded a long-term vision in material selection and in this regard, life cycle cost assessment has been proven to be a better assessment tool than the initial cost of construction. Despite its higher initial cost, aluminum offers many positive attributes, such as a high resistance to weight ratio, good recyclability, and excellent corrosion resistance, which can significantly reduce the life cycle cost of a structure over its entire service life. Yet, the limited use of aluminum in bridge construction and the lack of literature on this matter do not provide comprehensive evidence of its superior performance in the long-term. Based on this premise, this study performs a life cycle cost analysis on the first all-aluminum bridge situated in Arvida, Quebec. The analysis has revealed that most maintenance costs are associated with the rehabilitation of the concrete deck. The frequent concrete deck maintenance dismisses the benefits of the low maintenance aluminum structure. In order to investigate further, an alternative analysis has also been performed on the bridge with a hypothetical aluminum deck that replaces the existing concrete deck. The comparison shows that the aluminum deck reduces the maintenance cost significantly. However, further analysis should be performed with an optimized aluminum deck that can also yield a significantly lower life cycle cost compared to the existing bridge. Full article

Zinc-coated carbon steel is commonly used in the construction of buildings, infrastructure objects such as roads and bridges, automotive production, etc. Coatings based on zinc-aluminum-magnesium alloys that may have better corrosion resistance than zinc have been developed. The coatings made of the new alloys have been available on the market for a shorter period of time than conventional zinc coatings. This paper presents data on the corrosion resistance of zinc and zinc-aluminum-magnesium coatings on carbon steel obtained by tests in four locations in Russia with marine and non-marine atmospheres. Four one-year exposures at the beginning of each season and two-year tests were performed. It is shown that the corrosion resistance of the coatings depends significantly on the beginning of the exposure. The categories of atmosphere corrosivity in relation to the coatings were determined at each location. Based on the dose–response function (DRF) for zinc developed for the territory of Russia, DRFs for the coatings were obtained. A match between the categories of atmosphere corrosivity determined by the first-year corrosion losses and estimated from the values of corrosion losses calculated using the DRF is shown. Based on the data of two-year tests, the variation in the corrosion rate over time is obtained. The corrosion rates of the coatings in the territory of Russia are compared to the corrosion rates of coatings observed in various locations around the world. An approximate estimate of the service life of the coatings at the test sites is given. Full article

Water-quenched copper slag (WCS) modified with alumina (Al₂O₃) has been proven as a cement substitute; however, the effect of Al₂O₃ on structural properties of WCS related to pozzolanic activity has not been well investigated. The structural properties and the pozzolanic activity of WCS with different amounts of Al₂O₃ are characterized by X-ray diffraction, differential scanning calorimetry, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and the uniaxial compressive strength test. The results show that only amorphous exists in copper slag, and the stability of amorphous first increases and then decreases with the increase in the alumina content. The addition of alumina significantly improves the pozzolanic activity of WCS at 7 and 28 days, but it has little effect on the pozzolanic activity of WCS when the slag’s curing age is 3 days. The results also show the increase in the non-bridging oxygen content, the decrease in the degree of polymerization, and the transition from Q² and Q⁴ to Q³ with the increase of alumina content. Moreover, the addition of aluminum will convert Si-O-Si into Si-O-Al. These experimental results show that the addition of alumina can improve the pozzolanic activity of WCS, which can be used to partially replace cement. Full article

This paper is an extended paper from the 24th International Conference on Mechatronics Technology, ICMT 2021. The basic mechanical characteristic that gauges the stiffness of a solid material is known as the Young’s modulus. To evaluate the Young’s modulus, destructive material testing is frequently used. This paper describes how to determine a material’s dynamic Young’s modulus using Digital Image Correlation (DIC) in conjunction with numerical back-analysis. Three different materials (brass, aluminum, and steel) were examined for their static and dynamic reactions. A static transverse displacement was first applied at the free end of the beam before it was released and the beam was allowed to vibrate freely. The resulting vibrations at the free end were monitored using the DIC method, following which the natural frequencies of the beam were derived by applying the Fast Fourier Transform (FFT) to the DIC measured time history. The Young’s modulus corresponding to the fundamental natural frequency of the beam was then obtained via modal back-analysis using the finite element program Ansys 2022 R1. In this way, the Young’s modulus of the material may be calculated using a combination of numerical and DIC techniques, thus allowing for the non-contact evaluation of the structural integrity without subjecting the material to destructive testing. Potential applications of this method include bridge and building assessments, and structural health monitoring (SHM). Full article

A novel damage detection approach is proposed in this study for a continuous girder bridge in which support reaction influence lines (ILs) are adopted. First, the relationship between the local damage of a continuous girder bridge and a damage index, based on support reaction ILs, is established through analytical derivation. Subsequently, the sensitivity of a support reaction IL-based damage index is analyzed using Dempster-Shafer (D-S) evidence theory, and it shows that the support reaction IL-based damage index is more noise-resistant if more support reaction ILs from a variety of locations are used. Three case studies (a simple numerical study of a two-span continuous beam, a laboratory experimental study of a two-span aluminum beam, and a complicated numerical study of a continuous girder bridge in Xiamen) have been conducted to validate the effectiveness of the proposed method in different damage scenarios, including single damage and multiple damages. Satisfactory damage identification results can be obtained even in high-level measurement noise conditions, showing that the proposed approach offers a promising field detection technique for identifying local structural damages in continuous girder bridges. Full article

Nowadays, the application of composite materials and light-weight structures is required in those industrial applications where the primary design aims are weight saving, high stiffness, corrosion resistance and vibration damping. The first goal of the study was to construct a new light-weight structure that utilizes the advantageous characteristics of Carbon Fiber Reinforced Plastic (CFRP) and Aluminum (Al) materials; furthermore, the properties of sandwich structures and cellular plates. Thus, the newly constructed structure has CFRP face sheets and Al stiffeners, which was manufactured in order to take experimental measurements. The second aim of the research was the elaboration of calculation methods for the middle deflection of the investigated sandwich-like structure and the stresses that occurred in the structural elements. The calculation methods were elaborated; furthermore, validated by experimental measurements and Finite Element analysis. The third main goal was the elaboration of a mass and cost optimization method for the investigated structure applying the Flexible Tolerance optimization method. During the optimization, seven design constraints were considered: total deflection; buckling of face sheets; web buckling in stiffeners; stress in face sheets; stress in stiffeners; eigenfrequency of the structure and constraints for the design variables. The main added values of the research are the elaboration of the calculation methods relating to the middle deflection and the occurred stresses; furthermore, elaboration of the optimization method. The primary aim of the optimization was the construction of the most light-weighted structure because the new light-weight sandwich-like structure can be utilized in many industrial applications, e.g., elements of vehicles (ship floors, airplane base-plate); transport containers; building constructions (building floors, bridge decks). Full article

Greenhouse gases emitted by the aluminum electrolysis industry have brought great challenges to environmental protection. To address this problem, understanding the micro-generation mechanism of greenhouse gases in the electrolysis process is of great significance to their source suppression. Based on the first principles calculation method, the formation paths of CO, CO₂ and COF₂ during normal electrolysis were obtained by studying the adsorption behavior of oxygen and fluorine complex anions (short for [O]²⁻, [F]⁻) on the anode surface in cryolite alumina molten salt. The calculation results indicate that the O and F atoms prefer to adsorb at bridge site 1 of Model A, with the adsorption energies of −4.82 eV and −3.33 eV. In the [O]²⁻ priority discharge stage, Path 3 is the most likely path for CO₂ generation, while in the [O]²⁻, [F]⁻ co-discharge stage, Path 3 is the most likely path for COF₂ generation. It is deduced that the thermal decomposition of COF₂ at high temperature should account for the generation of CF₄ with a low concentration of the so-called non-anode effect PFC (NAE-PFC). Experiments were also conducted to verify the calculation by disclosing the bonding information of C, O and F, which are in good accordance with the results calculated by the first principle. Full article

A control circuit for inductive levitation micro-actuators was developed in this research, the circuit’s performance and its electrical parameters are discussed. The developed control circuit was fabricated on a four-layer printed circuit board (PCB) board with a size of 60 × 60 × 25 mm. It consisted of a generator based on high-speed Flip-Flop components and a current amplifier build on a H-bridge configuration. The circuit was able to generate an AC current with a squared waveform in a frequency range from 8 to 43 MHz and with a peak-to-peak amplitude of up to 420 mA. To demonstrate the efficiency of developed circuit and its compatibility with a micro-actuation system, an inductive levitation micro-actuator was fabricated by using 3D micro-coil technology. The device was composed of two solenoidal coil designs, a levitation and a stabilization coil, with outer diameters of 2 and 3.8 mm, respectively. A 25 μm diameter gold wire was used to fabricate the coils, with the levitation coil having 20 turns and the stabilization coil having 12 turns, similar to the micro-structure presented previously by our group. Using the developed control circuit, the micro-actuator was successfully excited and it demonstrated the actuation of aluminum disc-shaped micro-objects with diameters of 2.8 and 3.2 mm and, for the first time, an aluminum square-shaped object with a side length of 2.8 mm at a frequency of 10 MHz. To characterize the actuation, the levitation height and the current amplitude were measured. In particular, we demonstrated that the square-shaped micro-object could be lifted up to a height of 84 μm with a current of 160 mA. The characterization was supported by a simulation using a 3D model based on the quasi-finite element model (FEM) approach. Full article

Sandwich panels are commonly used across industries for their ability to bear structural and thermal loads. In this paper, a panel chamber matching apparatus was designed to investigate the thermal performance of eight steel-based panels by exposing them to an impinging jet at approximately 550 °C for 30 min. Three types of low-cost materials (polycrystalline filaments, silica aerogel, and aluminum silicate) were used as the insulation core. The temperature of the panel surfaces was measured, as well as the metallic fasteners, including bolts, nails, battens, seams, and angle iron, to examine their thermal bridge effects. Major conclusions include the following: first, the maximum temperature on the impinged surface was consistent among all 20 cases, whereas that of the surface under free convection varied, ranging from 41 to 120 °C, depending on the core and thermal bridges. Second, most of the highest temperatures on opposite surfaces were caused by a section of bare angle iron, and this bridging effect could be significantly reduced by up to 50 °C using a few layers of cloth, although the improvement could be temporary. Bolts and nails were less effective as thermal bridges, while the battens could be more effective. Third, the estimated heat flux of all specimens ranged from 167 to 331 W·m⁻². Full article

In this work, experimental and numerical analyses of repairs on carbon fiber reinforced epoxy (CFRE) substrates, with CFRE and aluminum alloy doublers typical of aircraft structures, are presented. The substrates have a bridge gap of 12.7 mm (simulated crack), repaired with twin doublers joined with riveted, adhesive bonded, and hybrid joints. The performance of the repairs using different doubler materials and joining techniques are compared under static loading. The experimental results show that riveted joints have the lowest strength, while adhesive bonded joints have the highest strength, irrespective of the doubler material. Finite element analysis (FEA) of the studied joints is also performed using commercial FEA tool Abaqus. In the FEA model, point-based fasteners are used for the rivets, and a cohesive zone contact model is used to simulate the adhesive bond. The FEA results indicate that the riveted joints have higher tensile stresses on the metal doublers compared to the composite doublers. As per the failure modes, interestingly, for hybrid joints using composite doublers, the doublers fail due to net-section failure, while, for hybrid joints using metal doublers, it is the composite substrate that fails due to net-section failure. This suggests vulnerability of the composite structures to mechanical fastener holes. Lastly, the Autodesk Helius composite tool is used for prediction of first-ply failure and ply load distribution, and for progressive failure analysis of the composite substrate. Full article

During the casting of high aluminum steel, the dramatic increase in the Al₂O₃/SiO₂ ratio is inevitable, resulting in significant changes of the crystallization behavior, which would result in heat transfer and lubrication problems. Crystallization products and structure characterization of glassy CaO-SiO₂-based mold fluxes with different Al₂O₃/SiO₂ ratios were experimentally investigated using a differential scanning calorimetry technique and Raman spectroscopy. With increasing Al₂O₃/SiO₂ ratios, the following results were obtained. The crystallization temperature and the crystallization products are changed. With increasing Al₂O₃/SiO₂ ratios from 0.088 to 0.151, the crystallization temperature first increases greatly from 1152 °C to 1354 °C, and then moderately increases. The crystallization ability of the mold flux is strengthened. The species of the precipitated crystalline phase change from two kinds, i.e., Ca₄Si₂O₇F₂ and Ca₂SiO₄, to four kinds, i.e., Ca₄Si₂O₇F₂, Ca₂SiO₄, 2CaO·Al₂O₃·SiO₂ and Ca₁₂Al₁₄O₃₂F₂, the crystallization ability of Ca₄Si₂O₇F₂ is gradually attenuated, but other species show the opposite trend. The results of Raman spectroscopy indicate that Al³⁺ mainly acts as a network former by the information of [AlO₄]-tetrahedral structural units, which can connect with [SiO₄]-tetrahedral by the formation of new bridge oxygen of Al–O–Si linkage, but there is no formation of Al–O–Al linkage. The linkage of Al–O–Si increases and that of Si–O–Si decreases. The polymerization degree of the network and the average number of bridging oxygens decrease. Further, the relatively strong Si–O–Si linkage gradually decreases and the relatively weak Al–O–Si gradually increases. The change of the crystalline phase was interpreted from the phase diagram and structure. Full article

Two series of alumina (Al₂O₃)–mesoporous organosilica (Al–MO) hybrid materials were synthesized using the co-condensation method in the presence of Pluronic 123 triblock copolymer. The first series of Al–MO samples was prepared using aluminum nitrate nanahydrate (Al–NN) and aluminum isopropoxide (Al–IP) as alumina precursors, and organosilanes with three different bridging groups, namely tris[3-(trimethoxysilyl)propyl]isocyanurate, 1,4-bis(triethoxysilyl)benzene, and bis(triethoxysilyl)ethane. The second series was obtained using the aforementioned precursors in the presence of an amine-containing 3-aminopropyltriethoxysilane to introduce, also, hanging groups. The Al–IP-derived mesostructures in the first series showed the well-developed porosity and high specific surface area, as compared to the corresponding mesostructures prepared in the second series with 3-aminopropyltriethoxysilane. The materials obtained from Al–NN alumina precursor possessed enlarged mesopores in the range of 3–17 nm, whereas the materials synthesized from Al–IP alumina precursor displayed relatively low pore widths in the range of 5–7 nm. The Al–IP-derived materials showed high CO₂ uptakes, due to the enhanced surface area and microporosity in comparison to those observed for the samples of the second series with AP hanging groups. The Al–NN- and Al–IP-derived samples exhibited the CO₂ uptakes in the range of 0.73–1.72 and 1.66–2.64 mmol/g at 1 atm pressure whereas, at the same pressure, the Al–NN and Al–IP-derived samples with 3-aminopropyl hanging groups showed the CO₂ uptakes in the range of 0.72–1.51 and 1.70–2.33 mmol/g, respectively. These data illustrate that Al–MO hybrid materials are potential adsorbents for large-scale CO₂ capture at 25 °C. Full article