Search Results (198)

Bi₂Sr₂CaCu₂O_8+x (Bi2212) high-temperature superconductor exhibits broad application prospects in strong magnetic fields, superconducting magnets, and power transmission due to its exceptional electrical properties. However, during practical applications, Bi2212 superconducting round wires are prone to mechanical loading effects, leading to crack propagation and degradation of superconducting performance, which severely compromises their reliability and service life. To elucidate the damage mechanisms under mechanical loading and their impact on critical current, this study establishes a two-dimensional model with existing cracks based on phase field fracture theory, simulating crack propagation behaviors under varying conditions. The results demonstrate that crack nucleation and propagation paths are predominantly governed by stress concentration zones. The transition zone width of cracks is controlled by the phase field length scale parameter. By incorporating electric fields into the phase field model, coupled mechanical-electrical simulations reveal that post-crack penetration causes significant current shunting, resulting in a marked decline in current density. The research quantitatively explains the mechanism of critical current degradation in Bi2212 round wires under tensile strain from a mechanical perspective. Full article

Cracking in asphalt layers of rigid–flexible composite pavements under coupled ambient temperature fields and traffic loading represents a critical failure mode. Traditional models based on uniform temperature assumptions inadequately capture the crack propagation mechanisms. This study developed a thermo-mechanical coupling model that incorporates realistic temperature-modulus gradients to analyze the compressive-shear behavior and simulate crack propagation using the extended finite element method (XFEM) coupled with a modified Paris’ law. Key findings reveal that the asphalt layer exhibits a predominant compressive-shear stress state; increasing the base modulus from 10,000 MPa to 30,000 MPa reduces the maximum shear stress by 22.8% at the tire centerline and 8.6% at the edge; thermal stress predominantly drives crack initiation, whereas vehicle loading governs the propagation path; field validation via cored samples confirms inclined top-down cracking under thermo-mechanical coupling; and the fracture energy release rate (G_f) reaches a minimum of 155 J·m⁻² at 14:00, corresponding to a maximum fatigue life of 32,625 cycles, and peaks at 350 J·m⁻² at 01:00, resulting in a reduced life of 29,933 cycles—reflecting a 9.0% temperature-induced fatigue life variation. The proposed model, which integrates non-uniform temperature gradients, offers enhanced accuracy in capturing complex boundary conditions and stress states, providing a more reliable tool for durability design and assessment of composite pavements. Full article

A systematic study was conducted on the fatigue performance of Q500qENH weathering steel welded joints under low-temperature conditions of −40 °C in this paper. Low-temperature fatigue tests were conducted on V-groove butt joints and cross-shaped welded joints and S-N curves with a 95% reliability level were obtained. A comparative analysis with the Eurocode 3 reveals that low-temperature conditions lead to a regular increase in the design fatigue strength for both types of welded joints. Fracture surface morphology was examined using scanning electron microscopy, and combined with fracture characteristic analysis, the fatigue fracture mechanisms of welded joints under low-temperature conditions were elucidated. Based on linear elastic fracture mechanics theory, a numerical simulation approach was employed to investigate the fatigue crack propagation behavior of welded joints. The results indicate that introducing an elliptical surface initial crack with a semi-major axis length of 0.4 mm in the model effectively predicts the fatigue life and crack growth patterns of both joint types. A parametric analysis was conducted on key influencing factors, including the initial crack size, initial crack location, and initial crack angle. The results reveal that these factors exert varying degrees of influence on the fatigue life and crack propagation paths of welded joints. Among them, the position of the initial crack along the length direction of the fillet weld has the most significant impact on the fatigue life of cross-shaped welded joints. Full article

The ridged cutter, a highly representative non-planar PDC cutter known for its strong impact resistance and wear durability, has demonstrated significant effectiveness in enhancing the rate of penetration (ROP) in hard, highly abrasive, and interbedded soft–hard formations. Understanding the crack evolution is fundamental to revealing the rock-breaking mechanism of ridged PDC cutters. To date, studies on rock breaking with ridged cutters have largely focused on macroscopic experimental observations, lacking an in-depth understanding of the crack evolution characteristics during the rock fragmentation process. This study employs the Finite–Discrete Element Method (FDEM) to establish a three-dimensional numerical model for simulating the interaction between the ridged cutter and the rock. By analyzing crack propagation paths, stress distribution, and the stiffness degradation factor (SDEG), the initiation, propagation patterns, and sequence of cracks around the cutter are investigated. The results indicate the following outcomes: (1) The ridged cutter breaks rock mainly by tensioning and shearing, while the conventional planar cutter breaks the rock by shearing. (2) The rock-breaking process proceeds in three stages: compaction, micro-failure, and volumetric fragmentation. (3) Crack evolution around the cutter follows the rule of “tension-initiated and shear-propagation”; that is, tensile damage first generates at the front of the crack due to tensile stress concentration, whereas shear damage subsequently occurs at the rear under high shear stress. Finally, mixed tensile–shear macro-cracks are generated. (4) The spatial distribution of cracks exhibits strong regional heterogeneity. The zone ahead of the cutter contains mixed tensile–shear cracks, forming upward-concave cracks, horizontal cracks, and oblique cracks at 45°. The sub-cutter zone is dominated by tensile cracks; the zone on the flank side of the cutter consists of a radial stress field, accompanied by oblique 45° cracks. The synergistic evolution mechanism and distribution law of tensile–shear cracks revealed in this study elucidate the rock-breaking advantages of ridged cutters from a micro-crack perspective and provide a theoretical basis for optimizing non-planar cutter structures to achieve more efficient volumetric fracture. Full article

Accurate and efficient modeling of thermomechanical failure in critical structures under extreme conditions remains a great challenge. Traditional local methods struggle with discontinuities, such as fractures, while peridynamics (PD) is computationally intensive. This study presents a rapid prediction framework that combines sequential PD thermomechanical coupling simulations with a deep learning (DL) surrogate model. The framework adopts bond-based PD to solve the deformation field, accounting for thermal expansion, whereas the temperature field is handled using the peridynamic differential operator to address boundary effects and enhance transient accuracy. The validation results show that the PD thermomechanical coupling model achieved high accuracy. For example, the cooling simulation results of a 2D plate using PD and FEM show that the results had a global error in temperature and displacement of less than 0.7%. In the Al₂O₃ ceramic quenching simulations, the crack propagation path is accurately reproduced using the PD model, which matches the experimental data well. To improve the computational efficiency, the DL surrogate model was trained on a large dataset generated by PD simulations. The inputs include the crack geometries and loads, and the outputs are the predicted crack openings, average radial displacement/strain, and circumference change rates. The optimized deep neural network (DNN) consisted of two hidden layers, each with nine neurons. The DNN model predicted complex multi-output responses in approximately 0.5 s, about 1200 times faster than direct PD simulation, maintaining high accuracy. The PD-DL framework offers a new direction for assessing the thermomechanical damage and structural integrity in engineering applications. Full article

Concrete–fractured rock composites (CFRCs) are critical load-bearing systems in tunnels, dams, and other underground structures. Previous studies have not fully characterized how fracture geometry and confining pressure jointly influence crack propagation and failure modes. In this study, the particle flow discrete element method is employed to develop a heterogeneous concrete–fractured rock composite model in which the parallel bond model (PBM) is integrated with the smooth-joint model (SJM). The effects of fracture inclination (0–90°) and confining pressure (1–20 MPa) on the composite’s strength characteristics, crack propagation, and failure modes are systematically investigated. It is demonstrated that composite strength is markedly enhanced by confining pressure. Fracture inclination governs the evolution of the failure mode: as the inclination angle increases from 0° to 90°, overall composite strength increases. Confining pressure further modulates the failure path by altering the threshold for crack initiation. Specifically, under low confinement (<10 MPa), the shear-to-tensile crack ratio decreases with increasing dip angle, marking a transition from shear-dominated to tension-dominated mechanisms. At 20 MPa, the ratio remains relatively constant, with tensile failure being dominant. These findings establish a confining pressure–fracture geometry–failure framework for concrete–rock composites and suggest design strategies for deep tunnels, shallow structures, and inclination-specific reinforcement. Full article

This study presents a geomechanics-driven marine approach for optimizing well trajectories in fractured offshore reservoirs, with a focus on the X Block of the Zhujiangkou Basin. The method integrates in situ stress analysis and fracture prediction within a three-dimensional geomechanical modeling framework, tailored to the complex tectonic and sedimentary characteristics of offshore environments. Multi-source geological and engineering data—including core observations, borehole imaging, well logs, and marine seismic interpretation—are synthesized to reconstruct the subsurface stress field and assess fracture development along potential well paths. Key geomechanical parameters, such as principal stress magnitudes and orientations, rock mechanical properties, and fracture propagation tendencies, are quantitatively evaluated to identify fracture-prone zones and mitigate drilling risks. This methodology enables dynamic adjustment of well trajectories to avoid high-stress zones while maximizing contact with productive fracture networks. A case study from a structurally complex marine fractured reservoir demonstrates the practical applicability of this approach, offering valuable guidance for safe and efficient offshore drilling design in geomechanically sensitive environments. The results highlight the significance of incorporating marine geomechanical insights into trajectory planning for enhanced reservoir development. Full article

CoCrFeNiMn high entropy alloy (HEA) fabricated via laser-based powder bed fusion (PBF-LB/M) exhibits exceptional mechanical properties, including high strength, better ductility than titanium alloy, and superior corrosion resistance. This study simulates the intergranular fracture behavior of PBF-LB/M CoCrFeNiMn HEA under tensile loading by embedding cohesive elements with damage mechanisms into polycrystalline representative volume elements based on the crystal plasticity finite element method. The simulation results show good agreement with reported experimental stress–strain curves, demonstrating that the crystal plastic constitutive model combined with the cohesive constitutive model can accurately describe both the macroscopic response behavior and fracture failure behavior of the CoCrFeNiMn HEA. Furthermore, this work investigates the mechanical properties of the HEA in different tensile directions, the improvement of anisotropy through columnar-to-equiaxed grain transition, and the effect of texture strength on crack initiation and propagation. The results show that the polycrystalline CoCrFeNiMn HEA exhibits anisotropic mechanical properties: simulated yield strengths (YSs) are 436.9 MPa (in the scanning direction) and 484.7 MPa (in the building direction), tensile strengths (TSs) reach 639 MPa and 702.5 MPa, and elongations (ELs) are 10.6% and 21.8%, respectively. After equiaxed grain formation, the EL in the scanning direction increased from 10.6% to 17.2%, while the EL in the building direction decreased from 21.8% to 20.3%. Concurrently, the anisotropy coefficients of YS, TS, and EL decreased by 1.8%, 2.2%, and 36.1%, respectively. The cracks initiate at stress concentrations and subsequently propagate along grain boundaries until final fracture. Variations in texture strength significantly influence the crack initiation location and propagation path in the CoCrFeNiMn HEA. Full article

This paper presents an analysis of the influence of the termination geometry of an undercutting anchor drive bolt and the shape of the bottom of the anchor hole on the initiation and progression of failure processes in a rock medium. The study employed the finite element method (FEM) to model various bolt termination configurations, including cylindrical terminations with a 2 × 2 mm chamfer, a rounded termination with radius R, and a conical termination. The interaction of these bolt geometries with both cylindrical and conical hole bottoms was analyzed. The numerical simulations enabled the identification of stress concentration zones and crack propagation paths, which are critical to understanding the efficiency and mechanism of rock failure. The results indicate that the geometry of the bolt termination significantly influences stress distribution within the contact zone, as well as the extent and morphology of the resulting failure zone. Specifically, employing a cylindrical termination with a 2 × 2 mm chamfer in combination with a conical hole bottom promotes the development of deep fractures, which may lead to the detachment of larger rock fragments. This mechanism may be useful in the development of non-explosive rock fragmentation technologies. The findings provide a foundation for further optimization of anchor designs and the development of targeted excavation methods in mining and geotechnical engineering. Full article

In this work, the Al/Mg bimetals were prepared by traveling magnetic field (TMF)-assisted compound casting, and the effects of current intensity on the interfacial microstructure and mechanical properties of the Al/Mg bimetals were investigated. The results revealed that the Al/Mg bimetallic interface without the TMF consisted of an Al-Mg intermetallic compounds (IMCs) area (Al₃Mg₂ + Al₁₂Mg₁₇ + Mg₂Si particles) and Al-Mg eutectic area (Al₁₂Mg₁₇ + δ-Mg). There was no change in the interfacial phase compositions with the TMF, but the interface thickness initially decreased and then increased with the increase in the TMF current, and the distribution of Mg₂Si became more uniform, dendrites become smaller, and dendritic arms fragment. The shear strength improves from 17 MPa without the TMF to 27 MPa with the TMFed-60 A, which was increased by 58.8%. This enhancement occurs because cracks are deflected by uniformly distributed Mg₂Si particles and do not coalesce into main cracks, ultimately fracturing in the eutectic region, which increases the length of the crack propagation path and thereby improves the shear strength of the Al/Mg bimetals. Full article

Low-permeability oil reservoirs, due to their weak seepage capacity and high start-up pressure, have limited yield-increasing effects through conventional water injection development methods. High-pressure water injection can significantly change the seepage environment around the well and within the reservoir, expand the effective swept volume of injected water, and thereby greatly enhance the oil recovery rate of water flooding. However, there is still a relative lack of research on the mechanism of high-pressure water injection stimulation and its influencing factors. This paper systematically analyzes the effectiveness mechanism of high-pressure water injection technology in the exploitation of low-permeability reservoirs. The internal mechanism of high-pressure water injection for effective fluid drive and production increase is explained from the aspects of low-permeability reservoir seepage characteristics, capacity expansion and permeability enhancement by high-pressure water injection, and the dynamic induction of micro-fractures. Based on geological and engineering factors, the main factors affecting the efficiency enhancement of high-pressure water injection are studied, including formation deficit, reservoir heterogeneity, dominant channel development and fracturing stimulation measures, injection displacement and micro-fractures, etc. The results of numerical simulation showed the following: (1) formation depletion, reservoir heterogeneity, and the formation of dominant channels significantly affected the effect of water flooding development and (2) engineering factors such as the fracture direction of hydraulic fracturing, water injection rate, and the development of micro-fractures under high-pressure water injection directly determined the propagation path of reservoir pressure, the breakthrough speed of the water drive front, and the ultimate recovery factor. Therefore, during the actual development process, the construction design parameters of high-pressure water injection should be reasonably determined based on the geological reservoir conditions to maximize the oil production increase effect of high-pressure water injection. This study can successfully provide theoretical guidance and practical support for the development of low-permeability oil reservoirs. Full article

Deep coalbed methane (CBM) is challenging to develop due to considerable burial depth, high ground stress, and complex geological structures. However, modeling deep CBM in complex formations and setting reasonable simulation parameters to obtain reasonable results still needs exploration. This study presents a comprehensive equivalent finite element modeling method for deep CBM. The method is based on the cohesive element with pore pressure of the zero-thickness (CEPPZ) model to simulate hydraulic fracture propagation and characterize the effects of bedding interfaces and natural fractures. Taking Ordo’s deep CBM in China as an example, a comprehensive equivalent model for hydraulic fracturing was developed for the limestone layer–coal seam–mudstone layer. Then, the filtration parameters of the CEPPZ model and the permeability parameters of the deep CBM reservoir matrix were inverted and calibrated using on-site data from fracturing tests. Finally, the propagation path of hydraulic fractures was simulated under varying ground stress, construction parameters, and perforation positions. The results show that the hydraulic fractures are more likely to expand into layers with low minimum horizontal stress; the effect of a sizable fluid injection rate on the increase in hydraulic fracture length is noticeable; the improvement effect on fracture length and area gradually weakens with the increased fracturing fluid volume and viscosity; and when directional roof limestone/floor mudstone layer perforation is used, and the appropriate perforation location is selected, hydraulic fractures can communicate the coal seam to form a roof limestone/floor mudstone layer indirect fracturing. The results can guide the efficient development of deep CBM, improving the human society’s energy structure. Full article

This study conducts numerical analysis of fatigue crack propagation in deck-rib welded joints of orthotropic steel decks (OSDs) using linear elastic fracture mechanics. The stress intensity factor for central surface cracks under constant range bending stress is calculated, and single and multi-crack propagation are simulated by a numerical integration method. The research results show that deck geometry critically influences crack propagation behavior. Wider decks accelerate propagation of cracks after the crack depth exceeds half the deck thickness, thicker decks exhibit linearly faster propagation rates yet retain larger residual section to bear loads, and increased weld penetration reduces fatigue life. Initial defects rapidly converge to a preferred propagation path, stabilizing near $a_f/c_f\approx 0.1$ ($a_f$ is the failure crack depth and $c_f$ is the half surface crack length) regardless of initial aspect ratio. For multi-crack scenarios, defect density dominates merging, doubling density increases final cracks by 45%. Merged cracks adhere closely to the single-crack path, while total section loss escalates with defect density and deck thickness but remains stress range independent. The identified convergence preferred propagation path enables depth estimation from surface-length measurements during real bridge inspections. Full article

Supercritical carbon dioxide (Sc-CO₂) thermal shock fracturing emerges as an innovative rock fragmentation technology combining environmental sustainability with operational efficiency. This study establishes a thermo-hydro-mechanical coupled model to elucidate how in situ stress magnitude and anisotropy critically govern damage progression and fluid dynamics during Sc-CO₂ thermal shock fracturing. Key novel findings reveal the following: (1) The fracturing mechanism integrates transient hydrodynamic shock with quasi-static pressure loading, generating characteristic bimodal pressure curves where secondary peak amplification specifically indicates inhibited interwell fracture coalescence under anisotropic stress configurations. (2) Fracture paths undergo spatiotemporal reorientation—initial propagation aligns with in situ stress orientation, while subsequent growth follows thermal shock-induced principal stress trajectories. (3) Stress heterogeneity modulates fracture network complexity through confinement effects: elevated normal stresses perpendicular to fracture planes reduce pressure gradients (compared to isotropic conditions) and delay crack initiation, yet sustain higher pressure plateaus by constraining fracture connectivity despite fluid leakage. Numerical simulations systematically demonstrate that stress anisotropy plays a dual role—enhancing peak pressures while limiting fracture network development. This demonstrates the dual roles of the technology in enhancing environmental sustainability through waterless operations and reducing carbon footprint. Full article

Although through tied-arch bridges exhibit strong structural robustness, collapse incidents triggered by the progressive failure of hangers still occasionally occur. Given that such bridges are unlikely to collapse due to the damage of a single or multiple hangers under the serviceability limit state, this study focuses on the failure safety limit state. Using the Nanfang’ao Bridge with inclined hangers and the Liujiang Bridge with vertical hangers as case studies, this paper investigates the dynamic response and failure modes of the residual structures when single or multiple hangers fail and initiate progressive collapse of all hangers. The results demonstrate that the configuration of hangers significantly influences the distribution of structural importance coefficients and the load transmission paths. Under identical failure scenarios, the Nanfang’ao Bridge with inclined hangers remains stable after the failure of four hangers without experiencing progressive collapse, whereas the Liujiang Bridge with vertical hangers undergoes progressive failure following the loss of only three hangers, which indicates that inclined hanger configurations offer superior resistance to progressive collapse. Based on the aforementioned analysis, the LS-DYNA Simple–Johnson–Cook damage model was employed to simulate the collapse process. The extent of damage and ultimate failure modes of the two bridges differ significantly. In the case of the Nanfang’ao Bridge, following the progressive failure of the hangers, the bridge deck system lost lateral support, leading to excessive downward deflection. The deck subsequently fractured at the mid-span (1/2 position) and collapsed in an inverted “V” shape. This failure then propagated to the tie bar, inducing outward compression at the arch feet and tensile stress in the arch ribs. Stress concentration at the connection between the arch columns and arch rings ultimately triggered global collapse. For the Liujiang Bridge, failure initiated with localized concrete cracking, which propagated to reinforcing bar yielding, resulting in localized damage within the bridge deck system. These observations indicate that progressive stay cable failure serves as the common initial triggering mechanism for both bridges. However, differences in the structural configuration of the bridge deck systems, the geometry of the arch ribs, and the constraint effects of the tie bar result in distinct failure progression patterns and ultimate collapse behaviors between the two structures. Thereby, design recommendations are proposed for through tied-arch bridges, from the aspects of the hanger, arch rib, bridge deck system, and tie bar, to enhance the resistance to progressive collapse. Full article