Search Results (1,251)

Crack detection and analysis are essential for maintaining the stability and longevity of infrastructure; however, traditional manual inspections or simple image processing techniques are inefficient. To address this, automated crack segmentation using deep learning is being actively researched. This study proposes a hybrid model combining U-Net and a Vision Transformer to enhance the accuracy of crack segmentation. The proposed model is based on U-Net’s encoder–decoder architecture and integrates a Convolutional Neural Network (CNN), which is strong in local feature extraction, with a Vision Transformer, which excels at capturing global features and long-range dependencies, to effectively learn complex crack patterns. Experimental results on the CrackSeg9k dataset show that the proposed model achieves a mean Intersection over Union (mIoU) of 0.7184, demonstrating superior segmentation performance compared to other models like the conventional U-Net and Attention U-Net. This indicates that the proposed hybrid approach successfully leverages both local and global features, proving its effectiveness in segmenting complex and irregular crack patterns. Full article

Polymer-based product usage in modern society is increasing day by day. Following usage, these inert products and hydrophobic materials contribute to environmental pollution, often accumulating as litter in ecosystems and contaminating water bodies. The rapid socio-economic development in the Kingdom of Saudi Arabia (KSA) has resulted in a significant increase in waste generation. This study was conducted on the utilization of recycled plastic waste (RPW) polymer along with commercial polymer (CP) for the modification of the local binder. The hot environmental conditions and increased traffic loading are the major reasons for the permanent deformation and thermal cracks on the pavements, which require improved and modified road performance materials. The Ministry of Transport and Logistical Support (MOTLS) in Saudi Arabia, along with other related agencies, spends a substantial amount of money each year on importing modifiers, including chemicals, hydrocarbons, and polymers, for modification purposes. This research was conducted to investigate and utilize available local recycled plastic materials. Comprehensive laboratory experiments were designed and carried out to enhance recycled plastic waste, including low-density polyethylene (rLDPE), high-density polyethylene (rHDPE), and polypropylene (rPP), combined with varying percentages of commercially available polymers such as Styrene-Butadiene-Styrene (SBS) and Polybilt (PB). The results indicated that incorporating recycled plastic waste expanded the binder’s susceptible temperature range from 64 °C to 70 °C, 76 °C, and 82 °C. The resistance to rutting was shown to have significantly improved by the dynamic shear rheometer (DSR) examination. Achieving the objectives of this research, combined with the intangible environmental benefits of utilizing plastic waste, provides a sustainable pavement development option that is also environmentally beneficial. Full article

Crack monitoring in concrete structures is essential to maintaining structural integrity. Therefore, this paper proposes a mobile ground robot equipped with a 2-DoF manipulator and stereo vision sensors for autonomous crack monitoring and mapping. To facilitate crack detection over large areas, a 2-DoF motorized manipulator providing linear and rotational motions, with a stereo vision sensor mounted on the end effector, was deployed. In combination with a manual rotation plate, this configuration enhances accessibility and expands the field of view for crack monitoring. Another stereo vision sensor, mounted at the front of the robot, was used to acquire point cloud data of the surrounding environment, enabling tasks such as SLAM (simultaneous localization and mapping), path planning and following, and obstacle avoidance. Cracks are detected and segmented using the deep learning algorithms YOLO (You Only Look Once) v6-s and SFNet (Semantic Flow Network), respectively. To enhance the performance of crack segmentation, synthetic image generation and preprocessing techniques, including cropping and scaling, were applied. The dimensions of cracks are calculated using point clouds filtered with the median absolute deviation method. To validate the performance of the proposed crack-monitoring and mapping method with the robot system, indoor experimental tests were performed. The experimental results confirmed that, in cases of divided imaging, the crack propagation direction was predicted, enabling robotic manipulation and division-point calculation. Subsequently, total crack length and width were calculated by combining reconstructed 3D point clouds from multiple frames, with a maximum relative error of 1%. Full article

This study investigates the shear strength of lotus-type unidirectional porous copper bonded to alumina substrates using the Direct Bonded Copper (DBC) process. Porous copper specimens with various porosities (38.7–50.9%) and pore sizes (150–800 $\mathsf{\mu }$m) were fabricated and joined to alumina discs. Shear testing revealed that both porosity and pore size significantly affect the interfacial strength. While higher porosity led to reduced shear strength, larger pore sizes enhanced the maximum shear strength owing to increased local contact areas and crack coalescence in the alumina substrate. Fractographic analysis using optical microscopy and SEM-EDS confirmed that failure mainly occurred in the alumina, with local fracture associated with pore distribution and size. To improve strength prediction, a modified model was proposed, reducing the error from 12.3% to 7.5% and increasing the coefficient of determination (R²) from 0.43 to 0.74. These findings highlight the necessity of considering both porosity and pore size when predicting the shear strength of porous copper/alumina DBC joints, and they provide important insights for optimizing metal structures in metal–ceramic bonding for high-performance applications. Full article

Red bricks serve as an important material for load-bearing or enclosing structures in traditional architecture and are widely used in construction projects both domestically and internationally. Fujian red bricks, due to geographical, trade, and immigration-related factors, have spread to Taiwan and various regions in Southeast Asia, giving rise to distinctive red brick architectural complexes. To further investigate the types of damage, such as cracking and missing bricks, that occur in traditional red brick buildings due to multiple factors, including climate and human activities, this study takes Fujian red brick buildings as its research subject. It employs the YOLOv12 rapid detection method to conduct technical support research on structural assessment, type detection, and damage localization of surface damage in red brick building materials. The experimental model was conducted through the following procedures: on-site photo collection, slice marking, creation of an image training set, establishment of an iterative model training, accuracy analysis, and experimental result verification. Based on this, the causes of damage types and corresponding countermeasures were analyzed. The objective of this study is to attempt to utilize computer vision image recognition technology to provide practical, automated detection and efficient identification methods for damage types in red brick building brick structures, particularly those involving physical and mechanical structural damage that severely threaten the overall structural safety of the building. This research model will reduce the complex manual processes typically involved, thereby improving work efficiency. This enables the development of customized intervention strategies with minimal impact and enhanced timeliness for the maintenance, repair, and preservation of red brick buildings, further advancing the practical application of intelligent protection for architectural heritage. Full article

Infrared thermography non-destructive testing technology has been widely used in the defect detection of composite structures due to its advantages, including non-contact operation, rapidity, low cost, and high precision. In this study, a laser-line scanning system combined with an infrared thermography was developed, along with a corresponding dynamic sequence image reconstruction method, enabling rapid localization of surface damages. Then, high-precision quantitative characterization of defect morphology in reconstructed images was achieved by integrating an edge gradient detection algorithm. The reconstruction method was validated through finite element simulations and experimental studies. The results demonstrated that the laser-line scanning thermography effectively enables both rapid localization of surface damages and precise quantitative characterization of their morphology. Experimental measurements of ceramic materials indicate that the relative error in detecting crack width is about 6% when the crack is perpendicular to the scanning direction, and the relative error gradually increases when the angle between the crack and the scanning direction decreases. Additionally, an alumina ceramic plate with micrometer-width cracks is inspected by the continuous laser-line scanning thermography. The morphology detection results are completely consistent with the actual morphology. However, limited by the spatial resolution of the thermal imager in the experiment, the quantitative identification of the crack width cannot be carried out. Finally, the proposed method is also effective for detecting surface damage of wrinkles in ceramic matrix composites. It can localize damage and quantify its geometric features with an average relative error of less than 3%, providing a new approach for health monitoring of large-scale ceramic matrix composite structures. Full article

Because of its specific nature, mining activity causes numerous negative impacts on the environment, both during the exploitation phase and after it has ended. An important source of income in the Jiu Valley is represented by the Lupeni Mining Exploitation. Like any mining activity, coal exploitation causes various negative effects on the environment. The subsidence phenomenon represents a significant issue associated with coal mining in the Jiu Valley. Underground extraction of mineral deposits induces displacement of the overburden strata. Such displacements result in ground subsidence and modifications of the surface topography. The larger the voids created following the exploitation of useful mineral deposits, the more they affect the surface of the land above the exploitation through sinking, displacement, deformation, and even cracks. Secondary deformations refer to post-mining surface movements induced by delayed rock mass adjustment, manifesting as ground collapse, localized subsoil failure, or uplift driven by groundwater rebound after drainage cessation. In this paper, we aim to study the subsidence phenomenon produced by coal mining at the Lupeni Mining Exploitation using the COMSOL simulation software and applying the Barcelona Basic Model (BBM) and Modified Cam-Clay (MCC) models. Following the simulation, the behavior of the rocks could be observed in order to improve prediction accuracy to support sustainable land management in post-mining areas. Full article

Ply Curving Termination (PCT) is an effective method to suppress stress concentration at composite ply drop-offs by locally curving the reinforcing fibers to reduce the stiffness. A previous study by the authors confirmed that PCT can suppress fatigue delamination failure in composite ply drop-off. However, the specimens used were external ply drop-offs without cover plies and did not reflect practical structural configurations. Following the basic study, this current study evaluated the fatigue damage suppression characteristic of PCT in practically relevant internal ply drop-offs with cover plies. Finite element analysis, fatigue testing, and detailed observation of the failure process using X-ray CT showed that PCT is effective in suppressing fatigue failure of internal ply drop-offs. In particular, delamination propagation from matrix cracks along the curving fibers, a weak point of PCT, is suppressed in the external ply drop-off. Finite element analysis indicated the importance of stress transfer from the cover ply to the ply drop-off, confirming that the fatigue damage suppression effect of PCT is enhanced in practical composite ply drop-off configurations. Full article

Under cyclic loading, fatigue limits Δσ_FL and fatigue crack growth (FCG) thresholds ΔΚ_th are usually examined using the S-N (or ε-N) and FCG da/dN-ΔK approaches, respectively. Historically, these two approaches are treated as a separate domain. This separation was due to the recognition that the nonuniform local stress field ahead of a crack differs significantly from the uniform stress field in a smooth specimen under axial fatigue loading. At present, there are no reliable approaches to analyzing these two regions in a unified way. In this paper, we first attempt to relate the experimental results of a cracked sample in the near-threshold region to the S-N fatigue limit of a smooth pull-push specimen. Then establish analytically the local stress intensity factor range ΔK at the process/damage zone ahead of the crack utilizing the local stress equal to Δσ_FL in a smooth specimen. Doing such an analysis, we can account the variations between the applied and the local stress ratios R (=min stress/max stress) for both cracked and smooth samples. The proposed relationship between ΔK_th and Δσ_FL would enable the development of a unified framework for fatigue analysis methods to predict damage evolution under low-stress in-service loading conditions. Full article

Submerged floating tunnel (SFT) may be subjected to sudden explosive loads such as internal vehicle explosions, terrorist attacks, and external explosions during operation. Based on the Arbitrary Lagrange–Euler (ALE) method, the locally truncated SFT model and fluid–structure interaction model of internal air and external water are established. Spherical explosives are used to simulate the destructive impact of internal explosions at different positions of the road inside the SFT and key positions at the bottom of the road. The results show that the peak accelerations at the monitoring points caused by the explosions of vehicles on the road rapidly decay within a range of three times the radius of the SFT, and circularly distributed damage appears on the explosion-facing side of the road surface. Longitudinal extensional damage occurs at the junction of the road surface and the SFT wall as well as the bottom supporting wall. Longitudinal cracks appear on the SFT wall. The peak accelerations at the monitoring points of the internal road caused by the concealed bomb at the bottom of the SFT rapidly decay within a range of twice the radius of the SFT, and the damage to the SFT is mainly concentrated on the road surface and the supporting wall. The most dangerous direction of external underwater explosion is determined to be directly below the SFT. When the scaled distance of the explosion is less than 0.543 m/kg^1/3, the accelerations at the monitoring points of the internal road show a single-peak trend with rapid rise and decay, and circumferential through-cracks appear on the SFT wall. The supporting wall connecting the SFT wall and the internal road transmits stress to the road, causing extensive damage. Full article

With global sustainable construction growth, fully recycled coarse aggregate concrete (RCAC)—eco-friendly for cutting construction waste and reducing natural aggregate over-exploitation—has poor durability in seasonally freezing saline-soil regions (e.g., Tumushuke, Xinjiang): freeze-thaw and salt ions (NaCl, Na₂SO₄) cause microcracking, faster performance decline, and shorter service life, limiting its use and requiring better salt freeze resistance. To address this, a field survey of Tumushuke’s saline soil was first conducted to determine local salt type and concentration, based on which a matching 12% NaCl + 4% Na₂SO₄ mixed salt solution was prepared. RCAC specimens modified with fly ash (FA), silica fume (SF), and polypropylene fiber (PPF) were then fabricated, cured under standard conditions (20 ± 2 °C, ≥95% relative humidity), and subjected to rapid freeze-thaw cycling in the salt solution. Multiple macro-performance and microstructural indicators (appearance, mass loss, relative dynamic elastic modulus (RDEM), porosity, microcracks, and corrosion products) were measured post-cycling. Results showed the mixed salt solution significantly exacerbated RCAC’s freeze-thaw damage, with degradation severity linked to cycle count and admixture dosage. The RCAC modified with 20% FA and 0.9% PPF exhibited optimal salt freeze resistance: after 125 cycles, its RDEM retention reached 75.98% (6.60% higher than the control), mass loss was only 0.28% (67.80% lower than the control), and its durability threshold (RDEM > 60%) extended to 200 cycles. Mechanistic analysis revealed two synergistic effects for improved performance: (1) FA optimized pore structure by filling capillaries, reducing space for pore water freezing and salt penetration; (2) PPF enhanced crack resistance by bridging microcracks, suppressing crack initiation/propagation from freeze-thaw expansion and salt crystallization. A “pore optimization–ion blocking–fiber crack resistance” triple synergistic protection model was proposed, which clarifies admixture-modified RCAC’s salt freeze damage mechanism and provides theoretical/technical guidance for its application in extreme seasonally freezing saline-soil environments. Full article

This study presents an integrated experimental and numerical investigation into the collapse characteristics of a cracked box girder subjected to bidirectional cyclic bending moments. An experimental test involving a box girder specimen with a prefabricated transverse crack on the deck panel is conducted under four-point bending to evaluate the influence of cracking on ultimate strength under cyclic loading. The findings are reported through load–displacement curves, strain measurements, and observations of both global and localised structural failure modes, demonstrating strong consistency with finite element simulations conducted using ABAQUS software (version 2022). The results reveal that cyclic loading prior to ultimate capacity induces negligible stiffness reduction in the box girder structure, consistent with the structural behaviour under monotonic loading. The initial failure mechanism is attributed to local buckling of the deck plate, subsequently followed by significant plastic deformation around the crack tips, ultimately leading to global collapse. Parametric studies are carried out to evaluate the influence of key variables on the girder’s residual strength, such as crack length, cyclic load amplitude and pattern. Full article

Pullout bond tests using specimens with an expansion-agent-filled pipe (EAFP) simulating the cracking due to rebar corrosion were conducted to evaluate the deterioration of bond behavior when the crack width is not uniformly distributed along the longitudinal direction. The primary specimens for the pullout test are designed with a bond length equal to 20 times the bar diameter. To investigate the distribution of bond stress along the rebar in detail, a bond analysis was performed using the local bond stress–slip model as a function of the induced crack width that is developed based on the pullout test of the specimens with a bond length of four times the rebar diameter. The EAFP simulation showed a tendency for larger crack widths at the free end, likely due to filling the expansion agent from the load-end side. From the results of the pullout bond test, as the induced crack width increases, the maximum bond stress decreases. The results of the bond analysis, assuming the five patterns of crack width distributions along the longitudinal direction, showed that the bond stress–slip curve is little affected by the difference in the crack width distribution. Within a bonded length up to 20 times the rebar diameter, the differences in crack width variations had little effect on the distribution of the local bond stress. It is possible to evaluate the bond behavior based on the average crack width. Full article

The stress corrosion cracking (SCC) susceptibility of 2195-T8 Al-Li alloy in N₂O₄ medium was evaluated using slow strain rate testing (SSRT). The electrochemical corrosion behavior and morphological evolution of the alloy under different conditions were further examined through potentiodynamic polarization measurements. The results indicate that with the increase in electrochemical corrosion rate, the corrosion morphology of the alloy extends from localized pitting and intergranular corrosion to severe exfoliation corrosion. In the N₂O₄ medium, the alloy exhibits significant susceptibility to SCC at tensile rates of ε ≥ 5 × 10⁻⁶ s⁻¹. However, when strained at ε = 10⁻⁶ s⁻¹, a sudden increase in I_SCC is observed accompanied by a transition to brittle intergranular fracture mediated by anodic dissolution. At the same stretch rate (ε = 10⁻⁶ s⁻¹), the susceptibility to SCC of the alloy in N₂O₄ medium increased with higher water content ω(H₂O). This trend is attributed to enhanced generation of HNO₃ and HNO₂, as well as increased diffusion of hydrogen—produced by the cathodic reaction—to the crack tip. The synergistic interaction between anodic dissolution and hydrogen embrittlement ultimately promotes the initiation and propagation of SCC in the alloy. Full article

Glass-ceramic optical components are extensively employed in advanced optical systems. The high-hardness and low-fracture toughness of glass-ceramics make it prone to cracks and subsurface damage during conventional cutting. The laser-assisted diamond cutting method can significantly improve the nano-cutting performance of glass-ceramics by locally heating and softening the material. However, its dynamic removal mechanisms remain unclear. The coupling mechanisms between the laser thermal field and the mechanical response of the material require further investigation. This study aims to reveal the dynamic removal mechanisms of glass-ceramics under laser-assisted nanoscale cutting conditions through numerical simulations and systematic experiments. It includes a systematic analysis of the effects of laser heating on chip morphology, temperature fields, stress fields, and cutting forces using a laser-assisted nano-cutting model. Additionally, through nanoscale taper cutting experiments, this study quantifies the enhancement effect of laser power on the critical depth of no observed surface cracks (NOSC). Finally, subsurface integrity results elucidate the mechanisms through which laser assistance inhibits crack propagation. The findings will provide theoretical support for optimizing laser-assisted cutting parameters and achieving high-quality machining of glass-ceramics. Full article