Crack Analysis Research Articles

Analysis of Geometric Characteristics of Cracks and Delamination in Aerated Concrete Products Using Convolutional Neural Networks

Currently, artificial intelligence (AI) technologies are becoming a strategic vector for the development of companies in the construction sector. The introduction of “smart solutions” at all stages of the life cycle of building materials, products and structures is observed everywhere. Among the variety of applications of AI methods, a special place is occupied by the development of the theory and technology of creating artificial systems that process information from images obtained during construction monitoring of the structural state of objects. This paper discusses the process of developing an innovative method for analyzing the presence of cracks that arose after applying a load and delamination as a result of the technological process, followed by estimating the length of cracks and delamination using convolutional neural networks (CNN) when assessing the condition of aerated concrete products. The application of four models of convolutional neural networks in solving a problem in the field of construction flaw detection using computer vision is shown; the models are based on the U-Net and LinkNet architecture. These solutions are able to detect changes in the structure of the material, which may indicate the presence of a defect. The developed intelligent models make it possible to segment cracks and delamination and calculate their lengths using the author’s SCALE technique. It was found that the best segmentation quality was shown by a model based on the LinkNet architecture with static augmentation: precision = 0.73, recall = 0.80, F1 = 0.73 and IoU = 0.84. The use of the considered algorithms for segmentation and analysis of cracks and delamination in aerated concrete products using various convolutional neural network architectures makes it possible to improve the quality management process in the production of building materials, products and structures.

Failure Analysis of Electronic Current Transformer Air Chamber Basin Insulator Cracking in a 330 kV Substation

In operation, the combined electrical appliances in the substation leak, and the insulation basin breaks when the old insulation basin is replaced. By using the methods of macroscopic inspection, penetration detection, material analysis, and scanning electron microscopy, the failure analysis of the broken basin insulator of the combined electric apparatus is complete, and the process of crack generation and expansion is analyzed. The analysis results show that the reason for the fracture of the basin-type insulator is uneven force during fastening or disassembling, subjected to shear and bending stress. The crack source starts at the stress concentration part, that is, the root of the groove of the inner ring seal ring, and continues to expand, resulting in the final fracture of the basin-type insulator. The next step is to strengthen the daily control of the transportation process and installation process of the basin insulator.

Crack Analysis of Textile Reinforced Concrete Using Automated Crack Evaluation via Digital Image Correlation

Detecting and measuring cracks during laboratory experiments to characterize material behavior is an important task in building materials research. In this context, the evaluation of crack distribution is emphasized, including crack widths. Contact-free, optical 2D/3D-measuring Digital Image Correlation systems are used to analyze the full-field deformation of the surface. To examine the parameters affecting crack analysis through this measurement mode, a parameter study was conducted analyzing carbon textile-reinforced concrete tensile strength tests. For this purpose, facet size, facet overlap, and the threshold for crack identification based on major strain calculations in the evaluation were varied. The novelty lies in the in-depth exploration of these parameters to enhance crack analysis accuracy. To facilitate this, an automated crack evaluation tool (ACE) was developed and validated through tensile tests. The results of this paper provide evidence of the key parameters that influence crack analysis in textile reinforced concrete and contribute valuable guidance on optimum setting parameters.

Mechanics and Crack Analysis of Irida Graphene Bilayer Composite: A Molecular Dynamics Study

In this paper, we conducted molecular dynamics simulations to investigate the mechanical properties of double-layer and monolayer irida graphene (IG) structures and the influence of cracks on them. IG, a new two-dimensional material comprising fused rings of 3-6-8 carbon atoms, exhibits exceptional electrical and thermal conductivity, alongside robust structural stability. We found the fracture stress of the irida graphene structure on graphene sheet exceeds that of the structure comprising solely irida graphene. Additionally, the fracture stress of bilayer graphene significantly surpasses that of bilayer irida graphene. We performed crack analysis in both IG and graphene and observed that perpendicular cracks aligned with the tensile direction result in decreased fracture stress as the crack length increases. Moreover, we found that larger angles in relation to the tensile direction lead to reduced fracture stress. Across all structures, 75° demonstrated the lowest stress and strain. These results offer valuable implications for utilizing bilayer and monolayer IG in the development of advanced nanoscale electronic devices.

Automatic road crack detection and analysis system based on deep feature fusion and edge structure extraction

ABSTRACT In order to solve the problem that the traditional crack image segmentation method cannot accurately extract the edge structure of road cracks, a flexible crack detection and identification system are provided. Firstly, a road crack dataset is built by processing the acquired images using the sliding window technique. A model called R2-AENet is proposed for training and testing. The model structure uses the recurrent residual convolutional neural network (RRCNN) to improve the convolutional structure and drive the accumulation of fracture features. The model decoder combines the attention-guided filtering module and the edge residuals module (ERB) better to extract the edge features of the feature map. As a result, it improves the crack segmentation performance. Finally, the research results are validated on the upgraded software platform. The experimental results demonstrate that the R2-AENet model achieves better segmentation results compared to the popular deep learning algorithm models. Evidently, the model achieves accuracy and recall of 0.982 and 0.849 on the collected dataset. Besides, the area under the curve (AUC) metric value can reach 0.992. In addition, the detection results in different data sets perform well, verifying that the model has exceptional robustness and can be applied to various environmental road inspection and maintenance projects.

Analysis of the Effect of Ultra-Fine Cement on the Microscopic Pore Structure of Cement Soil in a Peat Soil Environment

Treating peat soil foundations around Dianchi Lake and Erhai Lake in Yunnan is a complex problem in practical engineering projects. Peat soil solely reinforced with ordinary cement (OPC) does not satisfy demand. This study aims to solidify soil to achieve better mechanical properties. The preparation of peat soil incorporates a humic acid (HA) reagent into cohesive soil, and cement and ultra-fine cement (UFC) are mixed by stirring to prepare cement soil samples. They are then immersed in fulvic acid (FA) solution to simulate cement soil in the actual environment. X-ray diffraction (XRD), mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM), and pores and cracks analysis system (PCAS) tests are used to study the impact of the UFC on the microscopic pore structure of cement soil in a peat soil environment. The unconfined compressive strength (UCS) test is used for verification. The microscopic test results indicate that incorporating UFC enhances the specimen’s micropore structure. The XRD test results show the presence of C–S–H, C–A–S–H, and C–A–H. SEM and PCAS tests show that the UFC proportion increases by between 0% and 10%, and the percentage reduction in the macropore volume is the largest, at 38.84%. When the UFC admixture is 30%, the cumulative reduction in the percentage of macropore volume reaches 71.55%. The MIP test results show that the cumulative volume greater than 10 µm in pore size decreases from 7.68% to 0.17% with an increase in the UFC proportion. The UCS test results show that the maximum strength growth of cement soil is 12.99% when the UFC admixture is 0–10%. Incorporating UFC to form a compound curing agent solves the problem of the traditional reinforcement treatment of peat soil foundation being undesirable and decreases the amount of cement. This study provides practical guidance for reducing carbon emissions in actual projects.

Quantification of tiny damage variation in asphalt mixture during the low-temperature thermal cycle

The performance evaluation of asphalt materials during low-temperature thermal cycles remains a challenge, particularly in quantifying the early tiny damage development and recovery processes. To address this issue, a high-sensitivity nonlinear ultrasonic method - the second harmonic generation (SHG) technique in the form of Rayleigh surface waves, is proposed to investigate these behaviors in asphalt mixture. The decrease in thermal contraction value and stiffness modulus with cycles verifies the damage behavior at the macro level. Turning points in crack length, crack density, and nonlinear parameter during the thermal cycle indicate the generation of cracks from − 20 ℃ to − 30 ℃ during the cooling process. The decrease of crack length and crack density in the heating phase demonstrates the recovery of asphalt. The nonlinear ultrasonic parameter β'(c) caused by crack is successfully separated from the total nonlinear parameter β', and the recovery index (RI)is defined to quantify the recovery behavior. Both of them are highly consistent with crack length and crack density. While the sensitivity index (SI) of nonlinear parameter is hundreds or thousands of times greater than other measurements of damage development. Furthermore, a qualitative correlation between the nonlinear parameters and plastic strain has been established. This breakthrough widens the scope of studying low-temperature weak damage in asphalt mixtures, moving beyond the confines of crack analysis.

Analysis of liquid–vapor mixed migration mechanism in unsaturated soil based on the effect of temperature on soil microstructure

Moisture migration in unsaturated soils is a result of the interaction between temperature and soil microstructure. In order to reveal the mechanism of moisture increase of subgrade soils under diurnal cycle conditions, a series of macro and microscopic tests were carried out on the unsaturated silty clay and sand soil, including liquid–vapor mixed migration tests simulating a one-dimensional subgrade, environmental scanning electron microscope (ESEM), and matrix suction test. Then, the soil microstructure in microscopic images was investigated using the particle (pores) and cracks analysis system (PACS). Next, the relationship between the thermal effects of the soil–water characteristic curve (SWCC) and changes in soil microstructure was analyzed. Finally, the change mechanism of liquid–vapor mixed migration based on the change in soil microstructural under thermal effects was analyzed. The results showed under the diurnal cycle, both the silty clay and sand soil columns appeared in the phenomenon of a “diurnal cycle of water vapor migration”, which led to moisture accumulation at the top of the soil layer. In silty clay soil column, moisture was primarily driven by water vapor pressure and migrated upwards. Additionally, moisture redistribution led to changes in soil microstructure, which in turn influenced the process of moisture migration. The moisture content in the upper soil layer increased making both inter-aggregate and intra-aggregate pores decrease. The moisture content in the lower soil later decreased, leading to the water-holding capacity of the lower soil layer to increase. So, the moisture migration gradually decreased at night. In the sand soil column, moisture migration was mainly driven by gravity potential and migrated downwards. Moisture redistribution made inter-aggregate pore and matrix suction of the upper soil layer increase, leading to an increase in moisture migration at night.

Analysis of three-dimensional cracks horizontally placed in transversely isotropic FGMs under interior compressive stresses

This paper develops the dual boundary element method (DBEM) using a new fundamental singular solution. This new solution is the elastic fields of transversely isotropic multilayered materials of infinite extent under point concentrated loads. The discretization technique is utilized to approximate arbitrary variations of functionally graded materials (FGMs) with transverse isotropy in a graded direction. The proposed DBEM is used to analyze the three-dimensional crack problems in FGM halfspaces. The penny-shaped and elliptical cracks are horizontally placed on the interface between the FGM layer and homogeneous halfspace and are subjected to uniform compressive stresses on crack surfaces. The stress intensity factors are provided to understand the fracture behaviors of transversely isotropic FGMs. An influential factor is defined to describe the influence of the anisotropy of the FGMs on stress intensity factors. Results show that the anisotropy and heterogeneity of materials exert an obvious influence on the fracture properties of crack problems.

Integrating Crack Causal Augmentation Framework and Dynamic Binary Threshold for imbalanced crack instance segmentation

Crack analysis is a crucial component of structural health monitoring. A fundamental aspect of this is the identification and quantification of individual crack instances through crack instance segmentation. Due to the visually linear/curvilinear structure of the cracks, data imbalance problems inevitably arise in the instance segmentation task. To address this, a Crack Causal Augmentation Framework (CCAF) which incorporates morphological dilation and erosion is designed to enhance the representation of cracks within the training images. Furthermore, it has been observed that crack data is highly susceptible to variations in threshold during binarization, to address this issue, Dynamic Binary Threshold (DBT) branch has been implemented to enhance the segmentation accuracy by performing a regression task using spatial features in the segmentation network to determine the optimal binary threshold at the image level. Experimental results demonstrate that the implementation of the CCAF in conjunction with the DBT branch results in a synergistic enhancement of performance. We establish the efficacy of our proposed methods through evaluations on four crack datasets with varying sources and distributions, including a dataset with an extremely low density of crack pixels, where other prevalent crack instance segmentation techniques have been inadequate.

Correlation analysis of longitudinal cracks and vertical deformation within asphalt pavement of cold regions

The asphalt pavement longitudinal crack is a common distress in cold regions, resulting from uneven deformation of the subgrade. Analysis of the correlation law between uneven deformation and crack distress is of positive significance for understanding the mechanism of crack initiation, and putting forward treatment measures. In view of the complexity of longitudinal crack inducement and road surface deformation, the grey relational method was used to analyze this relationship. Through long-term monitoring of the vertical deformation data of typical road sections, the vertical deformation law of the pavement surface and its deformation characteristics under the action of temperature field are analyzed. Parameters such as vertical relative deformation, vertical relative deformation rate and vertical differential deformation VDSr were constructed to describe vertical deformation characteristics. Typical distribution characteristics of longitudinal fractures and their length and distribution characteristics are also described. The grey correlation analysis theory was utilized to analyze the relationship between deformation characteristics of sections, cross sections and monitoring points and longitudinal crack characteristics (length and location). The analysis reveals a linear positive correlation or a high correlation between several indicators. This study can provide a deeper understanding of the occurrence and development mechanism of longitudinal cracks in asphalt pavement of cold areas, and give references for the research of road engineering structure, materials and distress prevention.

Stress Corrosion Cracking Analysis of a Hot Blast Stove Shell with an Internal Combustion Chamber

The stress corrosion cracking during the operation of the internal combustion hot blast stove was analysed. The computational fluid dynamics and finite element analysis models were established to analyse the temperature, stress and other variables related to the condensation of the water and acids. The corrosion characteristics of condensation of acid and the stress corrosion cracking of the metallic shell of the hot blast stove during the operation were predicted by applying the fluid temperature and mapping it to the solid temperature. The stress corrosion cracking surface mobility mechanism was adopted and modified with a weight concept to consider the effect of the acid condensation and its concentration. The regions that have higher crack propagation rates were analysed. The influence of the increase in the blast temperature on the crack propagation rate was studied with the increase in the blast temperature by 45 K and 90 K from the reference blast temperature. The maximum temperature of the refractory linings was 1847 K in the on-gas period, and the maximum change in the shell temperature was 5.2 K when the blast temperature was increased by 90 K. The maximum crack propagation rate for the reference blast temperature was evaluated as 7.61×10−7 m/s. The maximum value of the crack propagation rate was increased by 16.7% when the blast temperature increased by 90 K. The conical region was found to have higher crack propagation rates, which means that the conical region should be the region of interest for managing the internal combustion hot blast stoves.

Methodology for simulating the elastoplastic behavior in crack propagation problems using dual formulations of the boundary element method

Due to the application of cyclic loads, the existing crack length in a structure increases with time, resulting in greater stress concentration around the crack tip and therefore causing an increase in propagation velocity and a decrease in residual strength of the structure which, at a given time, becomes so low that the structure can no longer support the service loads. This paper presents a new approach to evaluate two-dimensional elastoplastic models in a crack propagation scenario, based on the boundary element method and its dual formulations. The methodology adopted consists of two stages: firstly, the simulation of the elastoplastic behavior, which considers the process of initial stresses and allows the treatment of several flow criteria, without taking into account the incompressibility of inelastic deformations. In this step, the domain integral due to non-homogeneous terms in the plastification region is transformed into a boundary integral by the Dual Reciprocity Method (DRM) using the polyharmonic splines functions due to its local behavior and, from the plastic calculus, the J-Integral is used to compute the SIF's. The second stage aims to simulate, in an incremental way, the crack propagation path using homemade software for crack modeling and analysis based on ElastoPlastic Fracture Mechanics (EPFM) and the Dual Boundary Element Method (DBEM). To validate the adopted methodology, as well as correctly simulate the mechanical behavior of cracks in the plastic regime of the material, three 2D models with straight and inclined cracks are used. Initially, the von Mises criterion for perfectly plastic materials is used and the numerical results compared with classic models from the literature, showing the effectiveness of the program in crack treatment and in the prediction of the propagation path, as well as the non-linear algorithm in the region plastification using the DRM.

An adaptive crack inspection method for building surface based on BIM, UAV and edge computing

Unmanned aerial vehicle (UAV) and building information modeling (BIM) have been applied to inspect building surfaces to improve efficiency and reduce labor costs. However, most of the current research focus on the inspection mode of “first collect and then identify” with limited intelligence. Therefore, this study proposes a “global-local” adaptive inspection method for building surfaces by integrating BIM, UAV (with multifunction camera), and edge computing, enabling real-time synchronization of crack data collection and analysis. First, the building surface area to be inspected is extracted from BIM to generate global inspection points using the selected camera's field of view (FOV) and considering coordinates transformation between BIM and reality. Then, A star algorithm integrating with genetic algorithm (GA) is used to optimize the global flight path based on generated inspection points. Finally, the coordinates of the inspection points based on BIM are converted into real-world coordinates, and the flight parameters such as the flight yaw angle (FYA) and the gimbal yaw angle (GYA) are calculated to generate the inspection mission. During global inspection, a local adaptive inspection is proposed for each FOV through real-time local crack identification and flight replanning using edge computing and zoom camera. In addition, multiple battery supply points are automatically added considering the endurance of the UAV. A real building has been used to validate the proposed “global-local” adaptive inspection method. The experiment results show that the inspection time has been significantly reduced compared with the traditional method, and the crack identification of building surfaces can be implemented with high efficiency, precision, quality, and low cost.

A review of existing solidification crack tests and analysis of their transferability to additive manufacturing

A review of existing solidification crack tests and analysis of their transferability to additive manufacturing

Application of digital image processing to mortar crack analysis

Image analysis techniques can be used to detect and interpret the degradation processes that a material undergoes and to help identify the causes and mechanisms of degradation. Structures and morphological changes are also analysed to establish hypotheses about physical changes. Together with complementary analytical techniques, chemical and mineralogical changes can be evaluated.The methodological process consists of a sequential simplification of the initial micrograph: segmentation of the image, cleaning and isolation of the crack from associated elements, and crack skeletonisation. This method allows the previous image to be processed, thus successfully isolating the microcracks. It is also valid for their quantification.

Post-Earthquake Reconnaissance of a Dam with Stabilizing Fill using Drone Photogrammetry

Post-earthquake reconnaissance is an important process for assessing the safety of massive structures. Dams are critical structures that require evaluation following an earthquake, as dam failure can lead to significant damage to the surrounding area. This paper presents drone (unmanned aerial vehicle) photogrammetry-based reconnaissance of the Angat Dam (Philippines), which has stabilizing fill, following the M 6.1 Luzon earthquake in April 2019. The author presents the results of visual inspection, drone digital mapping, and seismically induced deformation monitoring, as well as a general interpretation of dam safety. Analysis of the instrumentation data did not indicate that any significant changes in crest settlement, piezometric head, or seepage rate resulted from the earthquake. However, seismically induced longitudinal cracking along the dam crest was observed in the drone photogrammetry. The digital surface model, orthoimage, and as-built GIS geometry characterizations generated using the drone photogrammetry facilitated the geospatial analysis of seismic cracking and deformation. It is found that the uplift deformation was caused by counteracting effects between the existing dam body and its stabilizing fill. It is concluded that the results obtained using drone digital mapping are a valuable reference for future deformation monitoring using regular mapping methods in a 3D geospatial digital model.

Analysis of multiple parallel cracks in a functionally graded magneto-electro-elastic plane using boundary collocation method

Analysis of multiple parallel cracks in a functionally graded magneto-electro-elastic plane using boundary collocation method

Experimental analysis and modeling of subsurface cracks with random propagation for ceramic material on rolling contact fatigue

During the degradation of critical rotating components using ceramic materials, due to the uncertainty of the failure generation mechanism, the high nonlinearity of failure evolution and the diversity of failure modes, the unpredictability of sudden failure triggered by random propagation of subsurface cracks poses a great challenge to the operation and maintenance. Based on the finite element model reconstructed from fatigue tests, an early failure evolution model for ceramic bearings considering random propagation of subsurface cracks is constructed in this paper. Throughout the work, the position coordinates of critical nodes characterizing the degree of crack propagation (α, β, γ) are introduced to visualize the influence of propagation on the finite element of crack front during the whole rolling contact process, whose errors (ɛ) are stabilized at 10%. Then Monte Carlo Simulation is used to generate the randomness events of crack propagation, which satisfies the uncertainty characteristics of early failure initiation and propagation under actual working conditions. The results show that the first deflection shows strong randomness. Afterwards, the main cracks move away from the surface in mixed fracture mode, and finally form abrupt spall after several deflections. The proposed model not only reveals the sudden failure mechanism of ceramic bearing under uncertain crack propagation, but also effectively evaluates performance degradation of critical rotating components using ceramic materials.

Flexural behavior of high-strength steel bar reinforced UHPC beams with considering restrained shrinkage

Despite the excellent mechanical properties of ultra-high performance concrete (UHPC), UHPC beams with a conventional reinforcement ratio consistently demonstrate limited ductility. Therefore, this study aims to enhance the ductility of reinforced UHPC beams by regulating the tensile interaction between steel fibers and reinforcement. Six UHPC beams with varying fiber volume fractions and reinforcement ratios were tested under flexure. The effect of restrained shrinkage on flexural behavior was emphatically investigated. A cracked section analysis was also implemented to predict cracking behaviors of UHPC beams and was verified by experimental results. The test results revealed an increase in the ductility of UHPC beams with an increasing reinforcement ratio, while a decrease was observed with an increasing fiber volume fraction. The contribution of UHPC tensile capacity decreased significantly with the increase in the reinforcement ratio because of the restrained shrinkage. The stiffness and crack control capacity of reinforced UHPC beams reaches a plateau when the sum of reinforcement ratio and fiber volume fraction exceeds 3.1%. Increasing the fiber content is more effective than increasing the reinforcement ratio in limiting crack development, whereas the converse is true for improving the flexural capacity.