Special Issue "Non-Destructive Testing of Structures"

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Structure Analysis and Characterization".

Deadline for manuscript submissions: closed (30 June 2020).

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editor

Prof. Dr. Magdalena Rucka
E-Mail Website
Guest Editor
Department of Mechanics of Materials and Structures, Faculty of Civil and Environmental Engineering, Gdansk University of Technology, Narutowicza 11/12, 80-233 Gdansk, Poland
Interests: non-destructive testing; ultrasonic waves; ground penetrating radar; dynamics of structures; material testing

Special Issue Information

Dear Colleagues,

Engineering structures are gradually destroyed over time due to the influence of atmospheric conditions, excessive loads, and processes of natural aging. Since damage in a structural element may lead to improper operation of the whole object, various damage detection and structural health monitoring methods have thus been investigated and developed to improve reliability and safety and to solve maintenance problems of infrastructural and mechanical structures.

It is my pleasure to invite you to submit a manuscript for this Special Issue focused on novel NDT approaches, development of single and integrated measurement techniques, and advanced signal processing and modeling. The aim of this Special Issue is to gather the experience of civil, mechanical, and aerospace research communities in the latest advances and trends in the field of non-destructive diagnostics of structures and their components.

The topics of interest include but are not limited to:

  • Condition assessment of civil, mechanical, aerospace, and offshore structures, as well as connections of structural elements;
  • Diagnostics of cultural heritage monuments;
  • Testing of structures made of novel materials;
  • Structural health monitoring systems;
  • Integration of non-destructive testing methods (e.g., guided waves, ground penetrating radar, acoustic emission, thermography);
  • Advanced signal processing for NDT;
  • Damage detection and damage imaging;
  • Modeling and numerical analyses for supporting SHM systems.

Prof. Dr. Magdalena Rucka
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Materials is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • non-destructive testing
  • structural health monitoring
  • metallic, concrete, wood, and composite structures
  • smart materials and structures
  • damage detection and visualization
  • modeling and simulations

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Published Papers (24 papers)

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Editorial

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Editorial
Special Issue: “Non-Destructive Testing of Structures”
Materials 2020, 13(21), 4996; https://doi.org/10.3390/ma13214996 - 06 Nov 2020
Cited by 1 | Viewed by 494
Abstract
The Special Issue “Non-Destructive Testing of Structures” has been proposed to present recent developments in the field of diagnostics of structural materials and components in civil and mechanical engineering. The papers highlighted in this editorial concern various aspects of non-invasive diagnostics, including such [...] Read more.
The Special Issue “Non-Destructive Testing of Structures” has been proposed to present recent developments in the field of diagnostics of structural materials and components in civil and mechanical engineering. The papers highlighted in this editorial concern various aspects of non-invasive diagnostics, including such topics as condition assessments of civil and mechanical structures and connections of structural elements, the inspection of cultural heritage monuments, the testing of structural materials, structural health monitoring systems, the integration of non-destructive testing methods, advanced signal processing for the non-destructive testing of structures (NDT), damage detection and damage imaging, as well as modeling and numerical analyses for supporting structural health monitoring (SHM) systems. Full article
(This article belongs to the Special Issue Non-Destructive Testing of Structures)

Research

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Article
Detection and Imaging of Damages and Defects in Fibre-Reinforced Composites by Magnetic Resonance Technique
Materials 2021, 14(4), 977; https://doi.org/10.3390/ma14040977 - 19 Feb 2021
Viewed by 619
Abstract
Defectively manufactured and deliberately damaged composite laminates fabricated with different continuous reinforcing fibres (respectively, carbon and glass) and polymer matrices (respectively, thermoset and thermoplastic) were inspected in magnetic resonance imaging equipment. Two pulse sequences were evaluated during non-destructive examination conducted in saline solution-immersed [...] Read more.
Defectively manufactured and deliberately damaged composite laminates fabricated with different continuous reinforcing fibres (respectively, carbon and glass) and polymer matrices (respectively, thermoset and thermoplastic) were inspected in magnetic resonance imaging equipment. Two pulse sequences were evaluated during non-destructive examination conducted in saline solution-immersed samples to simulate load-bearing orthopaedic implants permanently in contact with biofluids. The orientation, positioning, shape, and especially the size of translaminar and delamination fractures were determined according to stringent structural assessment criteria. The spatial distribution, shape, and contours of water-filled voids were sufficiently delineated to infer the amount of absorbed water if thinner image slices than this study were used. The surface texture of composite specimens featuring roughness, waviness, indentation, crushing, and scratches was outlined, with fortuitous artefacts not impairing the image quality and interpretation. Low electromagnetic shielding glass fibres delivered the highest, while electrically conductive carbon fibres produced the poorest quality images, particularly when blended with thermoplastic polymer, though reliable image interpretation was still attainable. Full article
(This article belongs to the Special Issue Non-Destructive Testing of Structures)
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Article
Corrugated Sheeting as a Member of a Shear Panel Under Repeated Load—Experimental Test
Materials 2020, 13(18), 4032; https://doi.org/10.3390/ma13184032 - 11 Sep 2020
Cited by 1 | Viewed by 409
Abstract
In stressed-skin design, the cladding stiffening effect on structures is taken into account. However, the “traditional” design is more usual, wherein this effect is neglected. Even if the diaphragm actions are not regarded, in particular cases such as big sheds (and others), the [...] Read more.
In stressed-skin design, the cladding stiffening effect on structures is taken into account. However, the “traditional” design is more usual, wherein this effect is neglected. Even if the diaphragm actions are not regarded, in particular cases such as big sheds (and others), the parasitic (unwanted) stressed-skin action may occur with the result of leakage or even failure. The structures of this kind have already been built. Thus, an important question arises: How can one assess them if there is a need to correct or redesign them? What kind of non-destructive approach can be used to achieve that? Experimental tests of small-scale shear panels made of trapezoidal sheeting were designed in order to observe the behaviour of the diaphragm under increasing and repeated load. The tests were oriented toward force–displacement relations and strains in selected areas of the sheeting. The results revealed nonlinear, hysteretic force–displacement behaviour of the panel and the occurrence of the persistent deflections and stresses which remain even after the unloading. The relation among the stresses, force–displacement paths and modes of failure can be potentially used in monitoring systems of existing buildings in terms of parasitic stressed-skin action. Full article
(This article belongs to the Special Issue Non-Destructive Testing of Structures)
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Article
Material Parameters Identification of Historic Lighthouse Based on Operational Modal Analysis
Materials 2020, 13(17), 3814; https://doi.org/10.3390/ma13173814 - 28 Aug 2020
Cited by 2 | Viewed by 605
Abstract
In the present paper, the identification of the material parameters of a masonry lighthouse is discussed. A fully non-invasive method was selected, in which the material properties were determined via numerical model validation applied to the first pair of natural frequencies and their [...] Read more.
In the present paper, the identification of the material parameters of a masonry lighthouse is discussed. A fully non-invasive method was selected, in which the material properties were determined via numerical model validation applied to the first pair of natural frequencies and their related mode shapes, determined experimentally. The exact structural model was built by means of the finite element method. To obtain experimental data for the inverse analysis, operational modal analysis was applied to the structure. Three methods were considered: peak picking (PP), eigensystem realization algorithm (ERA) and natural excitation technique with ERA (NExT-ERA). The acceleration’s responses to environmental excitations, enhanced in some periods of time by sheet piling hammering or by sudden interruptions like wind stroke, were assumed within the analysis input. Different combinations of the input were considered in the PP and NExT-ERA analysis to find the most reasonable modal forms. A number of time periods of a free-decay character were considered in the ERA technique to finally calculate the averaged modal forms. Finally, the elastic modulus, Poisson’s ratio and material density of brick, sandstone and granite masonry were determined. The obtained values supplement the state of the art database concerning historic building materials. In addition, the numerical model obtained in the analysis may be used in further cases of structural analysis. Full article
(This article belongs to the Special Issue Non-Destructive Testing of Structures)
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Article
Non-Destructive Testing of the Longest Span Soil-Steel Bridge in Europe—Field Measurements and FEM Calculations
Materials 2020, 13(16), 3652; https://doi.org/10.3390/ma13163652 - 18 Aug 2020
Cited by 4 | Viewed by 713
Abstract
The article describes interdisciplinary and comprehensive non-destructive diagnostic tests of final bridge inspection and acceptance proposed for a soil-steel bridge made of corrugated sheets, being the European span length record holder (25.74 m). As an effect of an original concept a detailed and [...] Read more.
The article describes interdisciplinary and comprehensive non-destructive diagnostic tests of final bridge inspection and acceptance proposed for a soil-steel bridge made of corrugated sheets, being the European span length record holder (25.74 m). As an effect of an original concept a detailed and precise information about the structure short-term response was collected. Periodic diagnostics of bridge deformations was done one year after it was built. Load test design was based on numerical simulations performed by means of finite element method (FEM). In situ measurements were done with the aid of: inductive sensors, optical total station, and terrestrial laser scanner. The results produced by terrestrial laser scanning were used to build a precise image of structure deformation in 3D space during the tests. The accuracy of laser mapping was significantly increased using the information coming from total station and inductive sensors. These have higher accuracy and therefore can be used as reference. Thus, new quality in measurements is introduced. Good correspondence between in situ values and FEM estimations was achieved. Therefore, such a combination of testing methods can be used in non-destructive diagnostics of structures and is an interesting alternative for the standard approach, in which the measurements are done in limited number of points. Full article
(This article belongs to the Special Issue Non-Destructive Testing of Structures)
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Article
Application of Elastic Waves and Neural Networks for the Prediction of Forces in Bolts of Flange Connections Subjected to Static Tension Tests
Materials 2020, 13(16), 3607; https://doi.org/10.3390/ma13163607 - 14 Aug 2020
Cited by 1 | Viewed by 550
Abstract
There is a group of measurement techniques that can be used in the task of force identification in steel bolts. In this paper, the potential of elastic wave propagation signals was studied for possible application in force monitoring systems. A series of laboratory [...] Read more.
There is a group of measurement techniques that can be used in the task of force identification in steel bolts. In this paper, the potential of elastic wave propagation signals was studied for possible application in force monitoring systems. A series of laboratory tests was carried out on flange connections subjected to static tensile tests. Each one contained six screws of the same diameter. Four bolts were equipped with washer load cells. Alternatively, selected bolts were equipped with piezoelectric transducers (actuator and sensor) in order to measure the elastic wave signals. Principal components analysis, time of arrival, and neural network compression were used for dimensionality reduction of the measured signals. Examples of the obtained results with respect to the studied connections show that the tension forces in bolts can be estimated with relatively good accuracy. Full article
(This article belongs to the Special Issue Non-Destructive Testing of Structures)
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Article
2D Digital Image Correlation and Region-Based Convolutional Neural Network in Monitoring and Evaluation of Surface Cracks in Concrete Structural Elements
Materials 2020, 13(16), 3527; https://doi.org/10.3390/ma13163527 - 10 Aug 2020
Cited by 5 | Viewed by 815
Abstract
This paper shows how 2D digital image correlation (2D DIC) and region-based convolutional neural network (R-CNN) can be combined for image-based automated monitoring and assessment of surface crack development of concrete structural elements during laboratory quasi-static tests. In the presented approach, the 2D [...] Read more.
This paper shows how 2D digital image correlation (2D DIC) and region-based convolutional neural network (R-CNN) can be combined for image-based automated monitoring and assessment of surface crack development of concrete structural elements during laboratory quasi-static tests. In the presented approach, the 2D DIC-based monitoring enables estimation of deformation fields on the surface of the concrete element and measurements of crack width. Moreover, the R-CNN model provides unmanned simultaneous detection and localization of multiple cracks in the images. The results show that the automatic monitoring and evaluation of crack development in concrete structural elements is possible with high accuracy and reliability. Full article
(This article belongs to the Special Issue Non-Destructive Testing of Structures)
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Article
Use of Time-Frequency Representation of Magnetic Barkhausen Noise for Evaluation of Easy Magnetization Axis of Grain-Oriented Steel
Materials 2020, 13(15), 3390; https://doi.org/10.3390/ma13153390 - 31 Jul 2020
Cited by 2 | Viewed by 686
Abstract
The paper presents a new approach to non-destructive evaluation of easy/hard magnetization axis in grain-oriented SiFe electrical steels based on the Barkhausen phenomenon and its time-frequency (TF) characteristics. Anisotropy in steels is influenced by a number of factors that formulate the [...] Read more.
The paper presents a new approach to non-destructive evaluation of easy/hard magnetization axis in grain-oriented SiFe electrical steels based on the Barkhausen phenomenon and its time-frequency (TF) characteristics. Anisotropy in steels is influenced by a number of factors that formulate the global relationship and affect the Barkhausen effect. Due to the observed high variability in the dynamics of magnetic Barkhausen noise (MBN) over time, obtained for various directions in grain-oriented steel, it becomes justified to conduct MBN signal analyses in the time-frequency domain. This representation allows not only global information from MBN signal over entire period to be expressed, but also detailed relationships between properties in time and in frequency to be observed as well. This creates the opportunity to supplement the information obtained. The main aspect considered in the work is to present a procedure that allows an assessment of the resultant angular characteristics in steel. For this purpose, a sample of a conventional grain-oriented SiFe sheet was used. Measurements were made for several angular settings towards the rolling and transverse directions. A data transformation procedure based on short-time Fourier transform (STFT) as well as quantitative analysis and synthesis of information contained in the TF space was presented. Angular characteristics of selected TF parameters were shown and discussed. In addition, an analysis of the repeatability of information obtained using the proposed procedure under various measurement conditions was carried out. The relationship between the selection of calculation parameters used during transformation and the repeatability of the obtained TF distributions were demonstrated. Then the selection of the final values of the calculation parameters was commented upon. Finally, the conclusions of the work carried out were discussed. Full article
(This article belongs to the Special Issue Non-Destructive Testing of Structures)
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Article
Nondestructive Damage Testing of Beam Structure Based on Vibration Response Signal Analysis
Materials 2020, 13(15), 3301; https://doi.org/10.3390/ma13153301 - 24 Jul 2020
Cited by 1 | Viewed by 511
Abstract
Nondestructive damage-testing technology based on vibration signal analysis makes full use of the response characteristics of wave and energy. With the advantages of wide bandwidths of response frequency and high sensitivity, the nondestructive testing technology based on vibration signal analysis has a superiority [...] Read more.
Nondestructive damage-testing technology based on vibration signal analysis makes full use of the response characteristics of wave and energy. With the advantages of wide bandwidths of response frequency and high sensitivity, the nondestructive testing technology based on vibration signal analysis has a superiority in the application for the detection and characterization of structural defects, and has become one of the important methods for the nondestructive testing of structural material defects and damage. This paper presents a novel method of detection localization and quantitative analysis for local damage in beam structures, based on the response analysis of vibration signals. A damage-detection and -identification algorithm based on a unscented Kalman filter (UKF) was designed, which greatly reduces the computational workload in the process of damage identification over that in conventional methods. The method presented in this paper has significances to widen the application scope of the nondestructive testing method, and increase the recognition efficiency and effectiveness of this kind of method in engineering. Full article
(This article belongs to the Special Issue Non-Destructive Testing of Structures)
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Article
Testing the Influence of the Material Bonding System on the Bond Strength of Large-Format Tiles Installed on Concrete Substrate under Mechanical Loading
Materials 2020, 13(14), 3200; https://doi.org/10.3390/ma13143200 - 17 Jul 2020
Cited by 1 | Viewed by 546
Abstract
The paper describes an experiment focusing on the way the material system influences the bond strength of large-format tiles installed on concrete substrate during mechanical loading under conditions that correspond to real-life application. This involves a controllable mechanical load applied over an area [...] Read more.
The paper describes an experiment focusing on the way the material system influences the bond strength of large-format tiles installed on concrete substrate during mechanical loading under conditions that correspond to real-life application. This involves a controllable mechanical load applied over an area of a test model while observing its condition using non-destructive methods (ultrasonic pulse velocity test, acoustic emission method, strain measurement, and acoustic tracing). The model consisted of a concrete slab onto which were mounted four different systems with large-format tiles with the dimensions of 3 m × 1 m. The combinations differed in the thickness of the tile, the adhesive, and whether or not a fabric membrane was included in the adhesive bed. The experiment showed that the loading caused no damage to the ceramic tile. All the detected failures took place in the adhesive layer or in the concrete slab. Full article
(This article belongs to the Special Issue Non-Destructive Testing of Structures)
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Article
The Recognition of the Micro-Events in Cement Composites and the Identification of the Destruction Process Using Acoustic Emission and Sound Spectrum
Materials 2020, 13(13), 2988; https://doi.org/10.3390/ma13132988 - 04 Jul 2020
Cited by 4 | Viewed by 563
Abstract
This paper presents the recognition of micro-events and their concentration in quasi-brittle cement composites and the identification of the destruction process based on acoustic emission and sound spectrum. The tests were conducted on a quasi-brittle composite of a cement paste reinforced with a [...] Read more.
This paper presents the recognition of micro-events and their concentration in quasi-brittle cement composites and the identification of the destruction process based on acoustic emission and sound spectrum. The tests were conducted on a quasi-brittle composite of a cement paste reinforced with a high volume of dispersed polypropylene fibers. The possibility of identifying the destruction process based on acoustic emission and sound spectrum was confirmed. This paper focused on the identification of micro-events using the 3D spectrum. It was shown that the identification of the concentration of micro-events precedes the occurrence of critical crack fcr, ending the Hooke’s law range. The ability to recognize this phenomenon with the use of the 3D spectrum makes it possible to predict the structure destruction process and subsequently to assess the structure destruction (micro and macro-cracks) and the reinforcement destruction (pull-off, breaking). It was confirmed that the three-dimensional spectrum provided additional information, enabling a better recognition of micro and macro-changes in the structure of the samples based on the analysis of sound intensity, amplitudes, and frequencies. Full article
(This article belongs to the Special Issue Non-Destructive Testing of Structures)
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Article
Identification of Stress States in Compressed Masonry Walls Using a Non-Destructive Technique (NDT)
Materials 2020, 13(12), 2852; https://doi.org/10.3390/ma13122852 - 25 Jun 2020
Cited by 5 | Viewed by 584
Abstract
The structure safety can be assessed, but only indirectly, by identifying material properties, geometry of structures, and values of loads. The complete and comprehensive assessment can be done only after determining internal forces acting inside structures. Ultrasonic extensometry using an acoustoelastic effect (AE) [...] Read more.
The structure safety can be assessed, but only indirectly, by identifying material properties, geometry of structures, and values of loads. The complete and comprehensive assessment can be done only after determining internal forces acting inside structures. Ultrasonic extensometry using an acoustoelastic effect (AE) is among the most common non-destructive techniques (NDT) of determining true stresses in structures. Theoretical bases of the method were described in the mid 20th century. They were founded on the correlation between ultrasonic waves and the value and direction of stresses. This method is commonly used to determine stresses mainly in homogeneous materials without any inherent internal defects. This method is rarely applied to porous or composite materials, such as concrete or rock due to a high dispersion of results. Autoclaved aerated concrete (AAC), characterized by high homogeneity and porosity, is the popular material in the construction sector, used to produce masonry units. The discussed tests involved the acoustoelastic effect to determine stresses in the masonry wall made of AAC. This paper presents a widely theoretical background for the AE method, and then describes the author’s own research on AAC divided into two stages. At first, the empirical relationships between compressive stress and velocity of longitudinal ultrasonic wave, including humidity, were determined. In stage II, nine masonry walls were tested in axial compression. Mean compressive stresses in the masonry wall determined with the proposed method were found to produce a satisfactory confidence level up to ca. 50% of failure stresses. Results were significantly understated for stresses of the order of 75% of failure stresses. Full article
(This article belongs to the Special Issue Non-Destructive Testing of Structures)
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Article
Integrated Application of GPR and Ultrasonic Testing in the Diagnostics of a Historical Floor
Materials 2020, 13(11), 2547; https://doi.org/10.3390/ma13112547 - 03 Jun 2020
Cited by 2 | Viewed by 814
Abstract
The paper presents the results of integrated ground penetrating radar (GPR) and ultrasonic testing (UT) measurements conducted on a historical floor in St. Nicholas’ Church, Gdańsk, Poland. The described inspection was the first stage of the technical state assessment of the building. The [...] Read more.
The paper presents the results of integrated ground penetrating radar (GPR) and ultrasonic testing (UT) measurements conducted on a historical floor in St. Nicholas’ Church, Gdańsk, Poland. The described inspection was the first stage of the technical state assessment of the building. The aim of the study was the detection of underfloor air gaps, which were observed in a few trial pits. The condition of the ground under the floor was determined by localizing other inclusions such as rubble, human remains, brick walls and pipes. To identify the phenomenon of electromagnetic and ultrasonic wave propagation within the air gap, laboratory tests were conducted on physical models consisting of two concrete slabs stacked on top of each other and gradually moved apart to simulate a slot of varying thickness. The conducted research was supported by the numerical models of electromagnetic wave propagation. The obtained results showed that the integration of the GPR and UT methods provided an effective imaging of the floor and the area under it. Ultrasonic testing was proved to be a good technique for identifying air voids, while the GPR method allowed detecting concentrated anomalies and determining the degree of ground homogeneity under the floor. Full article
(This article belongs to the Special Issue Non-Destructive Testing of Structures)
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Article
Detection and Imaging of Debonding in Adhesive Joints of Concrete Beams Strengthened with Steel Plates Using Guided Waves and Weighted Root Mean Square
Materials 2020, 13(9), 2167; https://doi.org/10.3390/ma13092167 - 08 May 2020
Cited by 4 | Viewed by 864
Abstract
Strengthening of engineering structures is an important issue, especially for elements subjected to variable loads. In the case of concrete beams or slabs, one of the most popular approaches assumes mounting an external reinforcement in the form of steel or composite elements by [...] Read more.
Strengthening of engineering structures is an important issue, especially for elements subjected to variable loads. In the case of concrete beams or slabs, one of the most popular approaches assumes mounting an external reinforcement in the form of steel or composite elements by structural adhesives. A significant disadvantage of adhesive joints is the lack of access to the adhesive film for visual condition assessment, thus, there is a need for non-destructive diagnostics of these kinds of connections. The aim of this paper was the identification and visualization of defects in adhesive joints between concrete beams and steel plates using the guided wave propagation technique. The initial theoretical and numerical analyses were performed. The experimental wave field was excited and measured by the scanning laser Doppler vibrometry. The collected signals were processed by the weighted root mean square (WRMS) calculation. As a result, 2-D damage maps were obtained. The numerical simulations were performed to corroborate the experimental results. The results showed that the guided waves could be successfully applied in non-destructive diagnostics of adhesive joints between concrete and steel elements. However, the quality of damage visualizations strongly depended on the location of excitation. Full article
(This article belongs to the Special Issue Non-Destructive Testing of Structures)
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Article
Evaluation of Ferromagnetic Steel Hardness Based on an Analysis of the Barkhausen Noise Number of Events
Materials 2020, 13(9), 2059; https://doi.org/10.3390/ma13092059 - 29 Apr 2020
Cited by 4 | Viewed by 732
Abstract
Measurements are carried out of the Barkhausen noise (BN) and hardness on specimens where changes in hardness were obtained due to strain hardening (S235 and DC01 steels) and due to thermochemical treatment (AMS 6414 steel). A method is presented of processing the recorded [...] Read more.
Measurements are carried out of the Barkhausen noise (BN) and hardness on specimens where changes in hardness were obtained due to strain hardening (S235 and DC01 steels) and due to thermochemical treatment (AMS 6414 steel). A method is presented of processing the recorded BN signal to extract diagnostic information. The BN number of events is selected as the signal characteristic property to develop relevant correlations. A new methodology is presented for the development of correlations between the Barkhausen noise number of events and hardness. A possibility is indicated of developing correlations with a high R2 determination coefficient. The method limitations are specified. Full article
(This article belongs to the Special Issue Non-Destructive Testing of Structures)
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Article
FEM-Based Wave Propagation Modelling for SHM: Certain Numerical Issues in 1D Structures
Materials 2020, 13(9), 2051; https://doi.org/10.3390/ma13092051 - 28 Apr 2020
Cited by 1 | Viewed by 613
Abstract
The numerical modelling of structural elements is an important aspect of modern diagnostic systems. However, the process of numerical implementation requires advanced levels of consideration of multiple aspects. Important issues of that process are the positive and negative aspects of the methods applied. [...] Read more.
The numerical modelling of structural elements is an important aspect of modern diagnostic systems. However, the process of numerical implementation requires advanced levels of consideration of multiple aspects. Important issues of that process are the positive and negative aspects of the methods applied. Therefore the aim of this article is to familiarise the reader with the most important aspects related to the process of numerical modelling of one-dimensional problems related to the phenomena of the propagation of elastic waves and their application for damage detection purposes. Full article
(This article belongs to the Special Issue Non-Destructive Testing of Structures)
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Article
Comparison of Non-Destructive Techniques for Technological Bridge Deflection Testing
Materials 2020, 13(8), 1908; https://doi.org/10.3390/ma13081908 - 18 Apr 2020
Cited by 8 | Viewed by 868
Abstract
This paper presents a comparison and assessment of usefulness of various measuring techniques (terrestrial laser scanning (TLS), tachymetry, photogrammetry) applied to establish the behavior of a suspension bridge under different load scenarios. The applied techniques were examined on the bridge with a 165 [...] Read more.
This paper presents a comparison and assessment of usefulness of various measuring techniques (terrestrial laser scanning (TLS), tachymetry, photogrammetry) applied to establish the behavior of a suspension bridge under different load scenarios. The applied techniques were examined on the bridge with a 165 m span. The tested structure works as the technological bridge for a belt conveyor linking a lime mine and cement plant. The testing range consisted of conducting the non-contact measuring of the bridge and cable displacements under dynamic loads (during the belt conveyor movement—normal service loads) and static loads (while stopped). Tachymetric surveys were carried out using a precise total station (to obtain the reference data). A Canon 750D digital camera was applied in the photogrammetry technique. FARO Focus 3D and Trimble TX8 scanners were employed for the TLS measuring. The obtained results are especially important for bridge inspectors and managers who can use the non-contact measurements of serviced structures. Full article
(This article belongs to the Special Issue Non-Destructive Testing of Structures)
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Article
Methodology for Controlling the Technological Process of Executing Floors Made of Cement-Based Materials
Materials 2020, 13(4), 948; https://doi.org/10.3390/ma13040948 - 20 Feb 2020
Cited by 2 | Viewed by 736
Abstract
The article presents original complex methodology for the effective control of the entire process of executing floors made of cement-based materials. This methodology has been lacking in literature so far. The methodology was developed on the basis of many years of the authors’ [...] Read more.
The article presents original complex methodology for the effective control of the entire process of executing floors made of cement-based materials. This methodology has been lacking in literature so far. The methodology was developed on the basis of many years of the authors’ experience, which was acquired when diagnosing the technical condition of such floors. The methodology was preceded by a synthetic summary of the most important technological and technical requirements for floors made of cement-based materials. It was also enriched with a discussion of the problem documented by sample research results showing the state that may be the result of disregarding and not performing the necessary control activities. Full article
(This article belongs to the Special Issue Non-Destructive Testing of Structures)
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Article
The Use of Dijkstra’s Algorithm in Assessing the Correctness of Imaging Brittle Damage in Concrete Beams by Means of Ultrasonic Transmission Tomography
Materials 2020, 13(3), 551; https://doi.org/10.3390/ma13030551 - 23 Jan 2020
Cited by 7 | Viewed by 1669
Abstract
The accuracy of transmission ultrasonic tomography for the detection of brittle damage in concrete beams can be effectively supported by the graph theory and, in particular, by Dijkstra’s algorithm. It allows determining real paths of the fastest ultrasonic wave propagation in concrete containing [...] Read more.
The accuracy of transmission ultrasonic tomography for the detection of brittle damage in concrete beams can be effectively supported by the graph theory and, in particular, by Dijkstra’s algorithm. It allows determining real paths of the fastest ultrasonic wave propagation in concrete containing localized elastically degraded zones at any stage of their evolution. This work confronts this type of approach with results that can be obtained from non-local isotropic damage mechanics. On this basis, the authors developed a method of reducing errors in tomographic reconstruction of longitudinal wave velocity maps which are caused by using the simplifying assumptions of straightness of the fastest wave propagation paths. The method is based on the appropriate elongation of measured propagation times of the wave transmitted between opposite sending-receiving transducers if the actual propagation paths deviate from straight lines. Thanks to this, the mathematical apparatus used typically in the tomography, in which the straightness of the fastest paths is assumed, can be still used. The work considers also the aspect of using fictitious wave sending-receiving points in ultrasonic tomography for which wave propagation times are calculated by interpolation of measured ones. The considerations are supported by experimental research conducted on laboratory reinforced concrete (RC) beams in the test of three-point bending and a prefabricated damaged RC beam. Full article
(This article belongs to the Special Issue Non-Destructive Testing of Structures)
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Article
Influence of Crack Size on Stress Evaluation of Ferromagnetic Low Alloy Steel with Metal Magnetic Memory Technology
Materials 2019, 12(24), 4028; https://doi.org/10.3390/ma12244028 - 04 Dec 2019
Cited by 5 | Viewed by 741
Abstract
Based on the magneto-mechanical effect, the influence of crack size on stress evaluated with metal magnetic memory (MMM) technology was discussed in this paper. Based on equivalent theory, the regular rectangular grooves, with different widths and depths, were precut in the surface of [...] Read more.
Based on the magneto-mechanical effect, the influence of crack size on stress evaluated with metal magnetic memory (MMM) technology was discussed in this paper. Based on equivalent theory, the regular rectangular grooves, with different widths and depths, were precut in the surface of an experimental sample for simulating surface crack, and a three dimensional electrically controlled displacement system was used to collect the Hp(y) signal of the sample under different stresses, and the fracture morphology was observed by using scanning electron microscopy (SEM). The results show that the influence of detection line on Hp(y) signal can be ignored; as stress increases, the Hp(y) signal turns counterclockwise around zero-crossing point and its mutation, corresponding to the location of groove, becomes distinct gradually. When groove depth is constant, the magnetic intensity gradient changes in the form of quadratic polynomial as groove width increases, and when the groove width is the same, the magnetic intensity gradient is a linear function of groove depth. When stress reaches the yield strength of the material, the magnetic intensity gradient decreases gradually as stress increases further, and the orientation of magnetic domain is seen as the main reason for that result. At last, the experimental results are discussed based on the piezomagnetic effect and leakage magnetic field theory of finite depth slit model, and the change of magnetic domain orientation is considered to be the main reason. Full article
(This article belongs to the Special Issue Non-Destructive Testing of Structures)
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Article
Detection of Delamination with Various Width-to-depth Ratios in Concrete Bridge Deck Using Passive IRT: Limits and Applicability
Materials 2019, 12(23), 3996; https://doi.org/10.3390/ma12233996 - 02 Dec 2019
Cited by 6 | Viewed by 953
Abstract
In bridge structures, concrete decks have a higher risk of damage than other components owing to the direct impact of traffic. This study aims to develop a comprehensive system for bridge inspection using passive infrared thermography (IRT). Experiments were conducted on a concrete [...] Read more.
In bridge structures, concrete decks have a higher risk of damage than other components owing to the direct impact of traffic. This study aims to develop a comprehensive system for bridge inspection using passive infrared thermography (IRT). Experiments were conducted on a concrete specimen (assumed as the surface of the bridge deck) embedded artificial delaminations with different width-to-depth ratios (WTDRs). Both professional handheld IR camera (H-IRC) and a UAV mounted with an IR camera (UAV-IRC) were employed simultaneously to capture the surface temperature of the structure. The present work indicates that the passive IRT technique with an H-IRC can be used to detect delaminations located at depths of 4 cm or less from the structure surface if the WTDRs are not lesser than 1.9 for daytime and 2.5 for nighttime when testing on a sunny day. In addition, the larger the WTDR, the higher the temperature difference can be produced, thus delaminations could be observed more clearly. Furthermore, our study suggests that the concrete bridge deck inspection using passive IRT can produce appropriate results if the inspection is performed from 10:00 to 15:00 or from 19:30 to approximately 2:00 on a sunny day. Good agreement between the results obtained from tests using H-IRC and UAV-IRC was observed, which validates the application of UAV-IRC in real structure inspection. Full article
(This article belongs to the Special Issue Non-Destructive Testing of Structures)
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Article
Determination of Thermophysical Parameters Involved in The Numerical Model to Predict the Temperature Field of Cast-In-Place Concrete Bridge Deck
Materials 2019, 12(19), 3089; https://doi.org/10.3390/ma12193089 - 22 Sep 2019
Cited by 6 | Viewed by 932
Abstract
The paper deals with a concept of a practical computation method to simulate the temperature distribution in an extradosed bridge deck. The main goal of the study is to develop a feasible model of hardening of concrete consistent with in-situ measurement capabilities. The [...] Read more.
The paper deals with a concept of a practical computation method to simulate the temperature distribution in an extradosed bridge deck. The main goal of the study is to develop a feasible model of hardening of concrete consistent with in-situ measurement capabilities. The presented investigations include laboratory tests of high performance concrete, measurements of temperature evolution in the bridge deck and above all, numerical simulations of temperature field in a concrete box bridge girder. A thermal conductivity equation in the author’s program, using finite difference method has been solved. New approach for identification of the model parameters and boundary conditions (heat transfer coefficients) has been proposed. The numerical results are verified by means of a wide set of experimental tests carried out on three stages of the extradosed bridge studies. A high agreement between the concrete temperature distribution in the time and space domain was obtained. The temperature history of concrete hardening, supplemented with maturity method equations, made it possible to estimate an early-age compressive strength of the cast-in-place concrete. The proposed solution could be applied in a Structural Health Monitoring system for concrete objects. Full article
(This article belongs to the Special Issue Non-Destructive Testing of Structures)
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Article
On the Influence of Capillary-Based Structural Health Monitoring on Fatigue Crack Initiation and Propagation in Straight Lugs
Materials 2019, 12(18), 2965; https://doi.org/10.3390/ma12182965 - 12 Sep 2019
Cited by 2 | Viewed by 807
Abstract
This paper addresses the influence on the fatigue life induced by the implementation of a capillary-based structural health monitoring methodology, patented under the name eSHM. It consists in integrating structurally small and pressurized capillaries into the component, so that when a fatigue crack [...] Read more.
This paper addresses the influence on the fatigue life induced by the implementation of a capillary-based structural health monitoring methodology, patented under the name eSHM. It consists in integrating structurally small and pressurized capillaries into the component, so that when a fatigue crack breaches the capillary network, it results in a leak flow to the open atmosphere and loss of pressure in the galleries which is detected by a pressure sensor. The novelty of the proposed system resides in the opportunity to locate the capillary according to the designer’s need, as one resorts to additive manufacturing for the part production. However, the presence of these galleries in highly stressed regions raises concerns about crack initiation at the capillary itself and accelerated fatigue crack growth. This paper aims at the quantification of the influence the eSHM has on the fatigue behavior of the component and the determination whether this influence is significant or not. To that purpose, numerical simulations on a straight lug component, using the finite elements and eXtended Finite Elements Methods (XFEM), are performed. Various capillary sizes and shapes are assessed, so as to enable a general conclusion on the impact of the eSHM methodology in straight lugs. Full article
(This article belongs to the Special Issue Non-Destructive Testing of Structures)
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Review

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Review
Evaluation of Cracking Patterns in Cement Composites—From Basics to Advances: A Review
Materials 2020, 13(11), 2490; https://doi.org/10.3390/ma13112490 - 29 May 2020
Cited by 5 | Viewed by 886
Abstract
The structure and the development degree of a cracking pattern has a key impact on the durability of cement composites. This literature review focuses on the four most important aspects related to the evaluation of the surface cracking patterns, i.e., the process of [...] Read more.
The structure and the development degree of a cracking pattern has a key impact on the durability of cement composites. This literature review focuses on the four most important aspects related to the evaluation of the surface cracking patterns, i.e., the process of formation, propagation and evolution of cracks into a branched system of cracks from the point of view of the fracture mechanics; the detection techniques of the cracking patterns on the surface of cement composites, where the tools of computer image analysis are the most used; parameters which can quantify the development degree and morphology of the cracks system; and also the influence of a cracking pattern on the functional features of cement composites. The studies described so far indicate the necessity of continuous development of this research area, because the knowledge of key relationships between the cracking patterns and functional properties of a cement composite is necessary to estimate the degree of material degradation. Researchers agree that the works carried out in the field of evaluation of the cracking patterns, to a large extent, contributes to the development of non-destructive testing methods in the field of cement composites technology. Full article
(This article belongs to the Special Issue Non-Destructive Testing of Structures)
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