ABSTRACT The propagation characteristics of explosive stress waves in rock masses are fundamentally influenced by the coupling conditions between the charge and the surrounding medium. This study systematically investigates the effect of annular cavity structures on one‐dimensional explosive stress wave propagation and rock fracture behavior through a custom‐built one‐dimensional loading experimental system. Eight groups of comparative tests were carried out with decoupling coefficients ranging from 0 to 0.875, and the time‐domain and frequency‐domain responses of rock specimens were obtained via ultra‐dynamic strain measurement, digital image correlation (DIC), and Hilbert–Huang transform (HHT). The results show that rock fracture patterns evolve through four stages with increasing decoupling coefficient, and a critical decoupling coefficient of 0.75 is identified, corresponding to the most significant asymmetric spalling effect. Frequency‐domain analysis indicates that the cavity structure acts as a mechanical filter, suppressing high‐frequency components (30–80 kHz) while enhancing low‐frequency energy (below 20 kHz), which transforms the loading regime from impulsive shock to combined impact‐quasi‐static gas expansion. This study establishes the correlation between spectral evolution and fracture mechanisms and provides theoretical support for the optimization of decoupled charge designs in rock blasting engineering.
ABSTRACT A microcomputed tomography (micro‐CT)‐based framework was developed to predict the fatigue life of selective laser melting (SLM) AlSi10Mg specimens with different porosity levels and defect morphologies. Because full‐specimen pore‐resolved finite element analysis (FEA) is computationally impractical, specimen‐specific regions of interest (ROIs) were extracted from experimentally identified fracture‐critical locations for fatigue simulations. Predicted fatigue lives were consistently conservative, with an average log‐scale deviation of 13.64%, while preserving the experimental fatigue‐life trend. Additional simulations between 140 and 9 MPa enabled the extraction of ROI‐specific FEA‐derived fatigue strength. Void volume fraction (VVF) exhibited inverse relationships with both predicted fatigue life and fatigue strength. Comparisons of ROIs with similar VVF showed that volume‐weighted average sphericity also affected fatigue performance, indicating that defect morphology contributes beyond porosity alone. The proposed framework provides a defect‐resolved and morphology‐sensitive basis for fatigue assessment and supports future digital‐twin–oriented prediction of additively manufactured AlSi10Mg components.
ABSTRACT Barbed sutures revolutionize surgical wound closure by eliminating knots and ensuring uniform stress distribution, yet barb cutting introduces inclined straight‐fronted edge cracks that compromise fracture resistance. This study addresses this critical limitation by developing an equivalent model of barbed sutures, incorporating key geometric features, and employing three‐dimensional finite element analysis with the contour integral method to compute mixed‐mode stress intensity factors (SIFs) along the crack front. We systematically investigate the interplay between cutting parameters—depth ratios and angles—and SIFs for Modes I, II, and III, revealing how deeper cuts and higher angles exacerbate crack propagation risks. Equivalent SIFs, derived from maximum tangential stress and maximum potential energy release rate criteria, pinpoint the crack front's midpoint as the most vulnerable site, with empirical equations enabling rapid predictions. These findings offer actionable insights for optimizing barb design to balance anchoring strength and fracture toughness, enhancing suture reliability in clinical settings and informing fracture mechanics in cylindrical structures. This work bridges biomedical engineering and fracture theory, providing theoretical support for the development of safer and more effective surgical tools.
ABSTRACT In this study, the dynamic response of titanium alloy (TC4)‐carbon fiber–reinforced plastic (CFRP) double‐riveted structures under various loads was investigated through experimental method. Complementary finite element analysis under different loading conditions is conducted to elucidate the evolution of stress distribution and elastic deformation within the joint. Specifically, fatigue tests were conducted at loading angles of 0°, 45°, and 90° to compare the dynamic response and evolution process of fretting damage at the contact interface, with simultaneous monitoring of temperature changes. The results demonstrate that fatigue testing process consists of two distinct stages. In the partial slip state under low loads, the temperature had slight fluctuations around 25°C, and the two plates did not fail. During the gross slip state under high loads, the temperature reached approximately 70°C, leading to fatigue failure of CFRP. Moreover, surface damage patterns were similar across angles, whereas 0° loading was subjected to greater excitation. At a load of 10 kN, the fatigue life under 0° loading exceeded 1 million cycles, and it was approximately 2000 times longer than that under 45° and 90° loadings. Hence, 0° loading was more favorable for double‐riveted structures, even though a period of complete slip appeared in the early fatigue stage under the 0° loading mode.
ABSTRACT This study explores the fatigue damage of concrete components in the CRTS III slab ballastless track under repeated high‐speed train loading. A stochastic damage‐based computational framework is developed and implemented in a finite element track model to simulate the evolution of concrete fatigue damage over a 100‐year design life. The fatigue damage evolution, corresponding mechanical responses, and fatigue life of the concrete track‐slab, self‐compacting concrete layer, and concrete base are evaluated. The results indicate that tensile fatigue damage initiates in the lower region of the self‐compacting concrete layer, while compressive fatigue damage is confined beneath the rail support platforms of the track‐slab. Despite progressive damage accumulation, structural stress and deformation are only slightly affected. The concentration zones of compressive fatigue damage highlight the track‐slab as the most critical component, with its fatigue life exceeding the 100‐year service period.
ABSTRACT Rigorous application of continuum damage mechanics (CDM) models coupled with crack propagation schemes can predict crack branching or zigzag trajectories near the crack tip, even when the macroscopic crack growth is straight. This arises from oscillations in the local damage field and is consistent with experimental observations of ductile tearing; however, it complicates finite element simulations. This study investigates this behavior through two crack propagation strategies in finite element simulations. The first, termed the Mesoscale Crack Advance (MCA) approach, explicitly tracks changes in crack trajectory based on the evolving local damage field. The second, termed the Process Zone Element (PZE) approach, represents damage and crack advance in an averaged sense over a material's characteristic length. Both approaches produce similar results. Despite its simplified formulation, the PZE approach captures the essential features of ductile crack propagation and provides a computationally efficient, practical alternative for simulating ductile crack growth and brittle fracture.
ABSTRACT Construction of civil engineering structures on clay soils in cold areas can cause structural fracture/damage due to settlements from freeze–thaw (F–T) cycles. This study investigates the effects of propylene fiber and nanosilica on the mechanical and microstructural properties of cement‐stabilized clay in F–T conditions. Various tests measured unconfined compressive strength (UCS), stress–strain behavior, energy absorption capacity ( E u ) representing the energy to fracture, secant modulus ( E 50 ), and volume change (Δ V ) of the samples. Ductility/toughness was assessed using E u , whereas Δ V was used to evaluate cracking potential. The findings show that optimal amounts of fiber (0.2%) and nanosilica (2%) improve strength, but adding more reduces it. As evidenced by E u , fiber addition boosts energy absorption due to increased strain. Physicochemical analysis indicates that fibers improve mechanical interlocking. Furthermore, nanoparticles enhance cement efficiency by boosting chemical reactions due to their large surface area and filling voids with cementitious gels.
ABSTRACT Planet bearings constitute critical components of planetary gear systems (PGS), comprising a cage and rollers. Rotating rollers preclude direct sliding between the planet gear and carrier, while the cage maintains roller spacing and ensures stable motions. Cage fracture is a typical failure under revolution–rotation coupled conditions, but the failure mechanism and vibration features are still unclear. To address this issue, this study first establishes a PGS dynamic model and a flexible cage model, revealing that reciprocating roller–cage impact constitutes the primary driver. Moreover, the evolution process of cage fracture is elucidated, encompassing high‐cycle fatigue crack initiation, low‐cycle fatigue propagation, and ultimate brittle fracture. Experimental results indicate that cage fracture induces significant elevations in RMS and standard deviation of time‐domain signals, accompanied by pronounced sideband modulation and noise floor elevation near the meshing frequency and its harmonics. This investigation provides guidance for the life prediction and detection of cage fracture.
ABSTRACT This study compares fatigue crack propagation and fracture mechanisms in Al 2024‐T3 and Al 7075‐T6 aerospace alloys repaired with bonded carbon/epoxy composite patches. Single‐edge notched tension specimens were tested under identical constant‐amplitude cyclic loading, and repair efficiency was assessed using fatigue life data, stress intensity factor analysis, and SEM fractography. Composite repair markedly extended fatigue life: Al 2024‐T3 increased from about 1.35 × 10 5 to 4.05 × 10 5 cycles, whereas Al 7075‐T6 increased from about 3.9 × 10 4 to 1.6 × 10 5 cycles. The patch reduced the crack‐driving force by nearly 70% at large crack lengths. Fractography showed ductile crack growth in Al 2024‐T3 and more localized, brittle‐like damage in Al 7075‐T6. Fatigue life improvement was governed by load transfer, crack shielding, and crack closure, confirming the effectiveness of bonded composite repair for aerospace aluminum structures.
ABSTRACT Predicting fatigue crack growth (FCG) is critical for structural safety and reliability, but it is severely challenged by inherent material uncertainties and the limitations of any single physical model. This study proposes a probabilistic FCG prediction method that integrates an improved particle filter (PF) and a Bayesian fusion for multiple FCG models. To alleviate post‐resampling particle impoverishment, a component‐wise modified Metropolis–Hastings (MMH) move algorithm is introduced as a particle rejuvenation step after resampling, which is designed to preserve particle diversity more effectively than the conventional resampling strategies. Furthermore, the Bayesian fusion dynamically weighs multiple FCG models (Paris–Erdogan, Kujawski, Forman, Nasgro), enabling mitigation of single‐model bias. The proposed method was applied on the FCG prediction of a group of compact‐tension (CT) specimens that have undergone experimental testing. Comparisons between the predicted and experimental results demonstrate that the proposed method provides more accurate FCG prediction in most of the CT specimens and the corresponding 95% confidence intervals (CIs) can encompass the measured crack paths.
ABSTRACT This paper investigates multiple embedded curved cracks in a functionally graded piezoelectric (FGP) strip. In order to compute Mode I/II stress intensity factors (SIFs) and electric displacement intensity factor (EDIF), distributed dislocation technique (DDT) is employed. It is assumed that the mechanical properties vary exponentially along the thickness of the strip. Through the application of Fourier transform integration, the formulation is reduced to a system of Cauchy‐type singular integral equations. These equations are then solved numerically to determine the dislocation density on the crack surfaces, which serve to calculate field intensity factors. The DDT represents an effective approach for solving plane crack problems with high precision. It performs effectively even with complex crack geometries and systems comprising multiple curved cracks. Hence, the analysis developed in this study enables the consideration of an FGP strip with any number of curved cracks. The results have been validated by comparison with analytical solutions in other available papers. Numerical results focusing on the influence of the geometry of curved cracks, nonhomogeneity parameters, thickness of the strip, and interaction between cracks on field intensity factors.
ABSTRACT This study aims to numerically investigate the mode I, II, and III fracture behaviors of additively manufactured degradable, bioplastic polylactic acid (PLA) lattice specimens. Numerical simulations were performed using the eXtended Finite Element Method (XFEM) based on the extracted PLA's mechanical and fracture material properties. The maximum principal stress and fracture energy power‐law criteria were utilized to simulate damage initiation and evolution in three‐dimensional (3D) numerical analyses. To consider the effects of build orientation, the transversely isotropic elasticity model (TIEM) was implemented. To facilitate the XFEM analyses, the equivalent solid material model (ESMM) technique was also utilized. The experimental load‐displacement responses of single‐edge notched bending specimens under the symmetric and asymmetric four‐point bending and mode III transverse shear cracked plate tests were conducted for comparison with the XFEM analyses in mode I, II, and III fracture, respectively. A common calibration factor, as well as the simultaneous utilization of the TIEM model, as well as the XFEM and ESMM techniques, reflected numerical results of acceptable accuracy compared to the experimental results; 5.3% (3.4%), 4.4% (5.8%), and 9.6% (5.4%) differences for the stiffness (peak load) of mode I, II, and III specimens, respectively.
ABSTRACT This study presents a data‐driven surrogate to the Gurson–Tvergaard–Needleman (GTN) fracture model, designed as an uncoupled formulation for computationally efficient prediction of ductile fracture initiation under high triaxiality in structural steels. Although the GTN model is widely used to simulate void nucleation, growth, and coalescence in metals, its coupled nature incurs significant computational overhead, limiting its applicability to finite element simulations of steel structures. To address this challenge, we propose a two‐stage artificial neural network (TS‐ANN) trained on 49,875 single‐element GTN simulations generated by varying six micromechanical parameters: initial void volume fraction, void nucleation volume fraction, nucleation strain, nucleation strain standard deviation, stress triaxiality, and void volume fraction at fracture. The TS‐ANN architecture decouples the material parameter mapping and stress‐state dependence into two subnetworks: Subnet‐1, a larger network evaluated once per analysis, and Subnet‐2, a compact network with only 25 parameters, evaluated at each integration point. The model achieves a mean absolute error of 0.00143 and predicts failure strain within 5% of GTN results for over 99% of the data points. When implemented in ABAQUS as an uncoupled fracture criterion, the proposed model predicts fracture displacement in ASTM A992 steel specimens with less than 5% deviation from GTN‐based results, while achieving a 35–95‐fold reduction in computational time. This approach enables accurate and scalable simulation of ductile fracture in structural‐scale systems.
ABSTRACT DH36/EH420 dissimilar‐steel welded joints (DSWJs) are increasingly used in lightweight marine structures, where fatigue performance is a critical concern. In this study, the fatigue behavior of DH36/EH420 DSWJs was systematically investigated by combining conventional stress‐life (S–N) testing with fracture‐mechanics‐based fatigue crack growth (FCG) analysis. For comparison, EH420‐EH420 welded joints (WJs) were also examined in the S–N tests. The results show that the DH36/EH420 DSWJs exhibited lower fatigue strength, with fatigue cracks preferentially initiating and final fracture occurring in the DH36 base metal (BM), consistent with the tensile fracture location. In contrast, FCG tests performed in five representative microregions showed that the highest crack growth rates occurred in the two heat‐affected zones (HAZs), followed by the DH36 BM, weld metal (WM), and EH420 BM. Microstructural characterization further supported the observed fatigue strength and crack growth trends. These findings indicate that, in the investigated DH36/EH420 DSWJs, the region controlling total fatigue life differs from the region most sensitive to long‐crack growth, corresponding mainly to the DH36 BM and the HAZs, respectively.
ABSTRACT To address the challenges of long testing durations, high specimen consumption, and limited prediction capability under small‐sample conditions in high‐cycle fatigue limit evaluation, a small‐sample fatigue limit prediction method based on prior data (P‐BaM) is proposed. The method constructs a mean prior S–N curve using historical tensile and fatigue data from similar materials. A simulated tensile point is introduced to establish the relationship between tensile properties and fatigue performance, and the prior S–N curve is sequentially updated using a limited number of high‐cycle fatigue failure data, enabling fatigue‐limit prediction and test‐strategy optimization. Prior databases were established for 42CrMo alloy steel, LY12 aluminum alloy, 304 stainless steel, and QT400 ductile cast iron, and the proposed method was validated through comparison with the Stromeyer model and a physics‐informed neural network (PINN) model. The results show that the stress at the simulated tensile point exhibits good stability and convergence with respect to tensile properties, providing an effective bridge between tensile and fatigue performance. For the investigated materials, fatigue‐limit prediction of 42CrMo alloy steel, 304 stainless steel, and QT400 ductile cast iron required only two to three fatigue specimens, while six to eight specimens were required for LY12 aluminum alloy to satisfy the stopping criterion and complete the prediction. The specimen requirement is substantially lower than that of conventional fatigue‐testing approaches. The proposed method enables rapid fatigue‐limit prediction using limited fatigue data and provides an effective approach for small‐sample fatigue assessment of similar metallic materials.
ABSTRACT 22MnB5 boron steel is widely used in hot‐stamped automotive structural components owing to its high strength and excellent crashworthiness. This study investigates the cyclic deformation behavior of cold‐rolled 22MnB5 steel under uniaxial low‐cycle fatigue at strain amplitudes of 0.4% and 0.6%, representative of cyclic loading during forming and service. The specimen tested at 0.4% exhibited initial cyclic softening followed by hardening, whereas the 0.6% specimen showed initial hardening, subsequent softening, and pronounced secondary hardening. Interrupted fatigue tests combined with EBSD and XRD established a direct correlation between strain amplitude–dependent cyclic response and the corresponding microstructure and texture evolution. Higher strain amplitudes resulted in greater intragranular deformation, reflected by increased grain average misorientation, while cube {100}<001> and copper {112}<111> texture components progressively increased with cycling. These findings provide mechanistic insights for optimizing forming strategies and improving the fatigue durability of hot‐stamped automotive components.
In many weldment applications, fatigue failures occur under multiaxial cyclic loadings. The current literature on multiaxial fatigue life prediction of welded joints is largely centered on weld toe failures considering simplified weld geometry and under constant amplitude loading conditions. The focus of this work is on application of crack initiation-based fatigue life estimation approaches to steel welded joints with partial weld penetration and preserved start/stop regions as realistic conditions in practice yet rarely studied. The experimental dataset used for validation includes single- and multi-channel axial and torsional load types with and without mean stress and phase shift effects under constant and variable amplitude conditions. Fatigue life estimation methods used include nominal stress, local strain, and critical plane approaches. To account for the notch stress concentration and gradient effects of the welded joint hotspot, the theory of critical distance was employed. The critical plane approach resulted in the highest accuracy, robustness, and conservatism of life predictions for the loading conditions considered with reasonable estimations of micro-crack plane orientations in the welded joints.
Conventionally fabricated duplex stainless steels (DSSs) are well-known for their good fatigue, corrosion, and combined fatigue/corrosion performance. In laser beam powder bed fusion (PBF-LB/M), their fabricability and tensile behavior are increasingly studied, though literature highlights process-induced defects and the need for heat treatment to transform the fully ferritic as-built microstructure into a duplex (ferrite/austenite) state. Heat treatment can tailor grain size and reduce defects. This work investigates the interplay between microstructure and defects in tensile and torsional high-cycle fatigue of PBF-LB/M DSS. Three microstructures are examined: fully ferritic, fine-grained 50/50 duplex, and coarse-grained 50/50 duplex, with comparison to a hot-isostatically pressed condition to assess defect effects. The austenite-free microstructure is highly defects-sensitive, whereas duplex structures show reduced sensitivity, particularly under torsion. Fine grains enhance fatigue strength in both loading modes. These findings demonstrate how additive manufacturing-enabled microstructural design mitigates defect-sensitivity and inform heat treatment strategies for improved fatigue performance.
Structural anisotropy has a significant impact on the fracturing of sedimentary rocks. However, many studies using asymmetric semicircular bending (ASCB) fail to examine the coupled effects of fracture modes, energy considerations, and three-dimensional (3D) surface characteristics. This study investigates Mode I, Mode II, and mixed-mode (I/II) fracturing in bedded sandstone at various orientations. The ASCB tests are integrated with high-resolution laser scanning to reconstruct 3D fracture surfaces, thereby quantifying anisotropy through directional roughness and fractal dimensions. An energy-based analysis is introduced to interpret fracture processes beyond peak-load criteria. The findings demonstrate systematic transitions from matrix-dominated cracking to bedding-controlled ruptures that reveal instabilities induced by tensile-shear interactions under mixed-mode (I/II) loading. By explicitly linking fracture modes, bedding orientations, energy partitioning, and 3D morphology, this framework enhances conventional ASCB analyses. It provides a comprehensive mechanistic foundation for predicting fractures and assessing the stability of bedded rock masses in geotechnical engineering.
