Transverse Cracks Research Articles

Inclined crack identification in bidirectional FG beams on an elastic foundation using the h-version of the finite element method

This article examines the impact of inclined transverse cracking on the natural frequency of Euler-Bernoulli-model imperfect FG beams on an elastic foundation, taking into account the pinned-pinned and clamped-clamped boundary conditions. The equations are diffused using the classic finite element method (h-version). Material properties are considered to vary in both directions of the beam; width and thickness, using the power-law formula. The approximate porosity model is adopted with a uniform distribution. Cracked element stiffness is determined by reducing the cross-section of a bi-directional FG beam. The numerical results are compared with those of previous convergence studies for dimensionless fundamental frequencies. Case studies were carried out to evaluate the effect of the porosity values, the crack depth, the crack location, slope angle, and the Winkler-elastic foundation parameters on the first three natural frequencies of a beam with different support conditions and material gradient. In addition, the results demonstrated that the two-way distribution function plays an important role in the convergence of frequencies.

Failure Mechanism of Thermal Barrier Coatings on Nozzle Guide Vanes Fabricated from Nickel-Based Single-Crystal Superalloy under Gas Thermal Shock Conditions

The objective of this study was to investigate the early failure behavior of thermal barrier coatings on single-crystal nozzle guide vanes under gas thermal shock conditions. The microstructure and mechanical properties of the thermal barrier coating before and after the gas thermal shock tests were analyzed using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and microhardness testing. The results indicate the presence of a mixed layer containing Ni, Cr, Al, Zr, and O at the base of the ceramic layer, and reveal failure behavior in the thermal barrier coating. The analysis suggests that the incomplete formation of the thermal growth oxide layer between the ceramic layer and the bonding layer, before the deposition of the YSZ ceramic layer, led to the easy diffusion of elements from the bonding layer into the root of the ceramic layer during the gas thermal shock process, resulting in the formation of a mixed layer. In the test environment, significant thermal stress was generated in the mixed layer, leading to transverse cracks and ultimately causing early failure of the thermal barrier coating. Consequently, the “incomplete initial TGO layer” model is proposed.

DEM simulation of wave-generated river ice cover breakup

A numerical model, DEMRICE, coupling a discrete element model with a finite element shallow water hydrodynamic model, is developed to study ice cover breakup by water waves in river channels. The ice cover is modeled by bonded dilated polyhedral elements that can break when the stress between the elements exceeds a critical bond strength. The model is applied to simulate wave-ice cover interaction, transverse crack propagation, and fragmentation of the cracked ice cover in a straight rectangular channel. The influence of varying wave characteristics and ice properties, such as wave height, wavelength, wave slope, ice thickness, and ice flexure strength, on crack propagation and cover fracture is examined. The analysis showed that the cover uplifting is the main cause of the ice cover fracture. The propagation speed of the cracks along the cover is mainly influenced by the wave speed, wave characteristics, and ice properties.

Analysis on crack propagation of CRTS III slab ballastless track under temperature loads and freeze–thaw deterioration

In seasonal frozen region, the Chinese Rail Track System (CRTS) III slab track is subject to temperature loads and freeze–thaw deterioration, which may lead to further expansion of microcracks in track slabs. Mechanical parameters of track structure materials after freeze–thaw cycles are obtained through the experimental tests in this study. A finite element model of CRTS III slab track on subgrade section is then established by ABAQUS. Based on fracture mechanics theory, the types of cracks generated in track slabs under temperature loads and freeze–thaw deterioration, and crack expansion law are analyzed by using extended finite element method. The results show that under temperature loads, the expanded cracks in track slab are mainly Mode Ⅰ - Opening mode. There is the possibility of expansion for transverse cracks with larger size on the upper surface of track slab under negative temperature gradient load. Vertical capillary cracks at the location where track slab is bonded to self-compacting concrete are more likely to expand. Freeze-thaw deterioration will reduce the difference between the SIFs of cracks and fracture toughness of track slab material, which has a certain promotion effect on crack expansion.

Asphalt Pavement Transverse Cracking Detection Based on Vehicle Dynamic Response

Transverse cracking is thought of as the typical distress of asphalt pavements. A faster detection technique can provide pavement performance information for maintenance administrations. This paper proposes a novel vehicle-vibration-based method for transverse cracking detection. A theoretical model of a vehicle-cracked pavement vibration system was constructed using the d’Alembert principle. A testing system installed with a vibration sensor was put in and applied to a testing road. Then, parameter optimization of the Short-time Fourier transform (STFT) was conducted. Transverse cracking and normal sections were processed by the optimized STFT algorithm, generating two ideal indicators. The maximum power spectral density and the relative power spectral density, which were extracted from 3D time–frequency maps, performed well. It was found that the power spectral density caused by transverse cracks was above 100 dB/Hz. The power spectral density at normal sections was below 80 dB/Hz. The distribution of the power spectral density for the cracked sections is more discrete than for normal sections. The classification model based on the above two indicators had an accuracy, true positive rate, and false positive rate of 94.96%, 92.86%, and 4.80%, respectively. The proposed vehicle-vibration-based method is capable of accurately detecting pavement transverse cracking.

Different effects of interfacial properties on the tensile and compressive damage mechanisms of 3D woven composites: Multiscale damage model and numerical comparative study

A multiscale damage model is proposed based on a micro-mesoscale bridging model and a multiscale kinking model, which can predict the damage development processes of 3D woven composites (3DWCs) under different loading conditions using only few material parameters. At the microscale, the various mesoscopic damage modes of yarns, including tensile fiber breakage, compressive fiber kinking and transverse inter-fiber crack, can be simply divided into matrix- and fiber-dominated damage. Using this multiscale damage model, a numerical comparative study is conducted to investigate the effect of interfacial properties on the mechanical performances and damage mechanism of 3DWCs. The numerical results indicate that the interfacial properties exhibit different effects on the tensile and compressive strengths and damage mechanisms of 3DWCs. The interaction of different damage modes controls the overall trend of the tensile strength of 3DWCs. There is an optimum point for the tensile strength of 3DWCs at different interfacial fracture toughness. Beyond the optimum point, the tensile strength of 3DWCs is negatively correlated with interfacial properties. Unlike the tensile loading case, the better the interfacial properties, the later fiber kinking occurs, resulting in higher compressive strength of 3DWCs.

Bridge bottom crack detection and modeling based on faster R‐CNN and BIM

AbstractThe bridge bottom crack detection provides important state information for bridge disease control and safety assessment. This paper proposes a detection method based on deep learning Faster R‐CNN and BIM (Building Information Modeling). The UAV (Unmanned Aerial Vehicle) was used for close aerial photography to obtain high‐resolution crack images of the concrete surface at the bottom of a bridge. Through deep learning algorithms, a Faster R‐CNN model is trained and established for crack identifications. The crack identification accuracy rate and recall rate reach 92.03% and 96.54%, respectively. Crack images are mapped to a BIM model developed for the chosen bridge, and the box girder family with cracks and the three crack families of transverse cracks, longitudinal cracks and turtle cracks are established. The cracks are located and the visualization of the beam bridge with cracks was completed. In order to better assess the health condition of the bridge. The results show that the combination of UAV bridge crack detection and modelling solves the remote, visual and automated detection of cracks on the surface of bridge structures, which are difficult to reach manually, and has important scientific research and engineering application value.

Study of the Structural-Phase State of Hydroxyapatite Coatings Obtained by Detonation Spraying at Different O2/C2H2 Ratios

This work studies the influence of the composition of an acetylene–oxygen explosive O2/C2H2 mixture on the structure and properties of hydroxyapatite coatings obtained by detonation spraying. The molar ratios of O2/C2H2 were 2.61; 3.03 and 3.35; the explosive charge was between 73 and 77%. The results of X-ray phase analysis showed partial conversion of the hydroxyapatite (HA) phase to the tricalcium phosphate (α-TCP) phase and formation of the amorphous phase during detonation sputtering. The formation of a small amount of the α-TCP phase during detonation spraying of HA is obviously due to structural transformations occurring during the heating of the material by detonation products. In addition, very rapid cooling of molten particles leads to the formation of the amorphous phase. The study results of the microstructure of the cross sections of the formed coatings, conducted using scanning electron microscopy, indicate that an increase in the O2/C2H2 ratio leads to increased porosity in the coatings. Additionally, an increase in the explosive charge by 77% results in the appearance of transverse cracks in the coating.

A reliability-base method for thermal cracking prediction in asphalt concrete

This study focuses on understanding the impact of environmental factors that contribute to the deterioration and damage of Hot Mix Asphalt (HMA) pavements. One significant problem faced by HMA pavements is transverse (thermal) cracking, which refers to the formation of cracks perpendicular to the centerline of the pavement. Over the past few decades, researchers have put significant effort into analyzing and understanding how thermal cracking affects HMA pavements. Mechanistic-empirical models play a crucial role in this process, but they require a substantial amount of input data related to the pavement's structural and material properties. Obtaining this data can be done through various methods with different levels of quality, which affect the reliability of the pavement performance responses. The probabilistic base designs and specifications can consider the variation of input data and the impact of material and structural together with environmental parameters on pavement deterioration. In this project, transverse cracking, as one of the major asphalt concrete pavement cracking, particularly in the freezing areas, will be studied, and a reliability-based method will be introduced. To reach this goal, the long-term pavement performance (LTPP) database was used. A regression model from the key parameters of pavement material and structural properties and environmental and traffic indicators was generated. Then through the structural reliability method, the probability of overpassing of transverse cracking amount from the threshold for a pavement design was assessed.

Abnormal mechanical hysteresis behavior of Tyranno-ZMI SiC/SiC containing Ti3Si(Al)C2

This work studied the effect of tough phase Ti3Si(Al)C2 on the mechanical hysteresis behavior of SiC/SiC. Different from continuous fibers reinforced brittle ceramic matrix composites, the mechanical hysteresis behavior of SiC/SiC containing Ti3Si(Al)C2 shows some abnormal phenomena: as peak applied stress increases during cyclic loading-unloading-reloading tests, the thermal residual stress values exhibit highly dispersion and the thermal misfit relief strain shows abnormally slow growth. These abnormal phenomena are caused by the reduction of transvers cracks (perpendicular to loading fibers) and the generation of hoop cracks (parallel to loading fibers). The plastic deformations of Ti3Si(Al)C2 prevents the transverse cracking of modified matrix, while promoting the hoop cracking of SiC matrix prepared by chemical vapor infiltration (CVI-SiC). Hoop cracking occurs within the transition zone containing amorphous SiO2 layer and carbon layer in CVI-SiC matrix. The combination of weak transition zone and strong modified matrix finally leads to the occurrence of hoop cracking.

Roads are an important tool in l ANALYSIS DAMAGE PAVEMENT USING BINAMARGA METHOD ON LAMONGAN-GRESIK ROAD STA 45+200 - 47+200

Analysis of this research uses the Bina Marga method on flexible pavement. The field survey was conducted on Gresik-Lamongan National Road section. The purpose of the study was to determine the level of road damage, the type of road damage and the method of handling it using the BinaMarga method. Research was conducted using a visual survey, type of damage, level of damage, measurement of pavement surface damage, and a LHR (Average Daily Traffic) survey. The results obtained from this study are: Photole of 0. 08% with an area of 1.54 m², patches of 13.71% with an area of 262.51 m², Alligator Cracking by 41.00% with an area of 792.76 m², Rutting of 1.46% with an area of 27.92 m², Reflexor Cracking by 26.54% with an area of 509.20 m², Longitudinal & Tranverse Crack by 13.40% with an area of 256.62 m², Depression Grade of 1.75% with an area of 0.09 m², Polished Aggregate of 0. 17% with an area of 0.01 m² Routine Road Maintenance Practical Instructions, namely Asphalt (P2) The types of damage that are repaired using local asphalt are alligator cracks, box cracks, longitudinal and transverse cracks with width < 2 mm, and ravelling. Filling the hole (P5) Damage repaired by this method is box cracks, Aligator cracks with crack width > 2 mm and subsidence, and holes > 50 mm deep Leveling (P6) Damage that needs to be repaired by leveling is settlement/subsidence, holes with a depth of 10-50 cm, groove depth < 30 mm.

Anodik Polarizasyon ve Kayma Aşınmasının Gemi İnşa Alüminyum Alaşımı 5083'ün Çukurcuk Korozyonu Davranışına Etkisi

This study aimed to characterize the pitting corrosion and simultaneous wear-corrosion (tribocorrosion) mechanisms of shipbuilding aluminum alloy 5083 under sliding wear and different anodic polarization conditions in simulated seawater. A tribocorrosion experimental setup was provided for the study under a 3 N load and different anodic potentials in a 3.5% NaCl solution. In the study, many grooves, parallel scratches and transverse cracks were determined on the wear track surface due to the low hardness of the test material. Chloride ions played a decisive role in the corrosion and tribocorrosion behavior of AA 5083. The dissolution of AA5083 increased from open circuit potential to higher anodic potentials. A half-cube mechanism, similar to the pitting corrosion of pure aluminum, and an intergranular pitting corrosion mechanism were observed under high anodic potentials.

Fault Severity Estimation in Cracked Shafts by Integration of Phase Space Topology and Convolutional Neural Network

With the rapid advancement of industrial systems and the unavoidable complications and interconnectedness in systems, diagnostics of industrial machinery are achieving paramount importance. Accurate estimation of health condition of industrial machinery becomes more challenging due to the inherent nonlinearity, complexity, and uncertainty of the observations. Nonlinear dynamic analysis has proven to be a powerful tool for providing information about the health condition of a system that can be used for diagnostic applications. The current study particularly focuses on crack depth estimation using phase space analysis. Phase space provides a topological representation of the dynamics of the system and is highly informative about the health condition. The information suitable for diagnostics is employed by Convolutional Neural Networks, which are known to be powerful in extracting spatial information from maps. The proposed diagnostic method is evaluated on a Jeffcott rotor model with transverse crack in the rotating shaft to estimate the severity of the fault from the phase space topology as a case study.

Mechanical Characterization of Bi-Layer Environmental Barrier Coatings Under Tension and Bending Using Acoustic Emission and Digital Image Correlation

Abstract Fracture characteristics of bi-layer environmental barrier coatings (EBC) deposited on a woven ceramic matrix composite (CMC) substrate using air plasma spray processes were investigated under uni-axial tension and bend tests at room temperature. Health monitoring techniques such as acoustic emission (AE) and digital image correlation (DIC) were employed to better understand the cracking behavior of the coating and its progression. Post-test microscopy was performed to correlate the coating cracks with DIC and AE location. The results indicate that multiple transverse cracks first occurred in the coating, followed by substrate transverse cracks and additional coating cracks. DIC analysis was able to highlight the formation and location of these cracks. The fracture strength of the coating was estimated assuming the composite beam theory.

Damage detection in variable temperature conditions using artificial intelligence

When considering damage detection using the natural frequencies of structures, small frequency drops can indicate either the presence of cracks or a temperature change. This change can lead to additional stress affecting the modal parameters for specific structures, making it much harder to detect, locate, and evaluate damage accurately. The current research aims to describe a method for detecting transverse cracks in beams, considering temperature variations. The considered beam is fixed at both ends, thus inducing axial forces when the temperature is increased. The influence of temperature is considered using adjustment coefficients developed for each vibration mode. This coefficient can be used to accurately calculate the natural frequency for an intact or damaged beam. An analytical method for determining the natural frequencies caused by the changing temperature and the presence of a transverse crack is described and used to generate data for training a feedforward artificial neural network (ANN). The ANN’s capability of determining the position of transverse cracks in double-clamped beams subjected to small temperature changes is proven by creating numerical simulations with known crack positions and thermal conditions for testing the developed method.

Chloride-induced 3D non-uniform corrosion of steel in reinforced concrete considering mesoscale heterogeneities and early-age cracks

Considering that reinforced concrete structures typically work with cracks, this work aims to investigate the chloride-induced non-uniform corrosion of steel by proposing a five-phase cracked reinforced concrete model at mesoscale, including realistic aggregate, matrix, steel, early-age crack, and damage zone. A physically-based 3D mesoscale modeling approach is developed to accommodate all the phases by integrating gravity-driven compaction and vibration as in real casting procedures. This modeling approach is further developed to capture coupled mass transfer and electrochemical corrosion of steel, enabling simulations of non-uniform corrosion along both the circumferential and longitudinal directions of steel. The considerable variation in corrosion morphology due to aggregate distribution demonstrates the necessity of using 3D mesoscale models to predict steel corrosion. Early-age cracks accelerate the diffusion of corrosive agents, intensifying the corrosion of steel. Increasing the crack width, depth, and length all contribute to a higher dissolution thickness of the steel. With the same crack size, longitudinal cracks result in a larger average dissolution thickness of the steel. In addition, the maximum dissolution thickness of the steel is highly correlated with the degree of pitting corrosion, and in most instances, transverse cracks lead to a higher degree of pitting, causing a greater maximum dissolution thickness.

Fine‐grained crack segmentation for high‐resolution images via a multiscale cascaded network

AbstractHigh‐resolution (HR) crack images offer more detailed information for assessing structural conditions compared to low‐resolution (LR) images. This wealth of detail proves indispensable in bolstering the safety of unmanned aerial vehicle (UAV)‐based inspection procedures and elevating the precision of small crack segmentation. Nonetheless, achieving a balance between segmentation accuracy and GPU memory consumption poses a substantial challenge for deep learning models when processing HR crack images. To overcome this challenge, a novel “HR crack segmentation framework” (HRCSF) is proposed, specifically designed to meticulously segment crack images with resolutions exceeding 4K. First, a multiscale crack feature extraction network (MsCFEN) was proposed with the embedment of the strip pooling operation to enhance the representation of the transverse and longitudinal crack pixels from the complex backgrounds. Subsequently, two cascaded operations were tailored to MsCFEN, enabling a comprehensive refinement process that incorporates both global and local aspects. Furthermore, to fully leverage the potential of each proposed component in the refinement process, the complete architecture was trained using a loss function with embedded boundary optimization. Conclusively, a UAV‐based case study was conducted on a real bridge in Changsha, demonstrating HRCSF's practicability in segmenting HR crack images. The implementation of HRCSF allows the UAV to perform crack inspection effectively from a distance of 3 m away from the girder, resulting in a significant 50% reduction in inspection time compared to LR segmentation methods while maintaining high detection accuracy.

Identification of asphalt pavement transverse cracking based on 2D reconstruction of vehicle vibration signal and edge detection algorithm

Transverse cracking is related to asphalt pavement structural performance. However, the method for transverse cracks identification by vehicle vibration signal has hardly been applied because of an extremely low recognition accuracy. The study aims to precisely identify the pavement transverse cracks by vehicle vibration response. A two-dimensional reconstruction method that transformed the vehicle vibration signal into an image was proposed. Five edge detection operators were used to generate the features of vibration reconstruction images. Besides, this study combined two basic characteristics, Euler number, and total target area. Eight classification models based on the above two features were trained by the RUSBoost integrated classifier. The results showed that the classification model based on the Prewitt operator eight connected domain Euler number and the total target area performed excellently. The testing accuracy can reach 93.5%. The classification model presented in this study has an excellent effect on pavement transverse crack identification and feasibility.

Shear strength determining mechanism of a +/−45 laminate under tensile loading

The shear strength of a composite material is determined as a result of a complex damage and failure process, but the detailed progression has not been clearly elucidated. Here, the mechanism of determining the strength of a ±45 laminate under tensile loading is revealed from exquisitely designed experiments in conjunction with high-fidelity numerical simulation. Synchrotron radiation computed tomography is employed for extremely high-resolution images of damage status inside the composite just before its catastrophic failure. The ex situ observations discover the unique and consistent failure progression; one major matrix crack is initiated either in the +45 or −45 layer and delamination follows after the initial crack completely grows along both the fiber and transverse directions. After the delamination failure is triggered, remaining intact layers start to fail with multiple transverse matrix cracks. The failure of the intact layers is represented as a load drop in the global stress–strain curve. This sequential and interactive failure progression determines the shear strength of the ±45 laminate. The numerical analysis finds that the location of the initial matrix crack is dependent on the microstructure. Once the matrix crack is initiated, the numerical simulation exactly reproduces the experimentally observed failure process.

Numerical and experimental analysis of ultra-thin plies in carbon/epoxy cross-ply laminates subjected to bending after tensile cyclic loading

As a result of a fatigue testing campaign in cross-ply laminates with different thicknesses in the 90° ply block (conventional and ultra-thin), different cracking patterns were observed. While laminates with conventional 90° ply thickness show a damage pattern with transverse cracks in the 90° ply block and delaminations along the 0°/90° interface, laminates with ultra-thin plies show paths of debonds inside the ultra-thin 90° ply block both transverse and longitudinal to the loading direction. In order to see the influence that these different fatigue damage patterns could have on the mechanical behaviour of the laminates, static bending tests have been carried out after cyclic loading, and apparent flexural stiffness loss (concerning the pristine state) was measured. Numerical simulations of the bending test, including the cyclic damage pattern (and detailed non-linear frictionless contact conditions) were also carried out for a deeper understanding of the experimental evidence. Although the morphology of the fatigue damages encountered is different for the two studied 90° ply block thicknesses, their flexural behaviours are quite similar, in terms of apparent flexural stiffness loss, for both cross-ply laminates, independently of its 90° ply block thickness.