Crack Propagation Research Articles

Stability of Slope and Concrete Structure Under Cyclic Load Coupling and Its Application in Ecological Risk Prevention and Control

This paper focuses on the stability issues of geological and engineering structures and conducts research from two perspectives: the mechanism of slope landslides under micro-seismic action and the cyclic failure behavior of concrete materials. In terms of slope stability, through the combination of model tests and theories, the cumulative effect of circulating micro-seismic waves on the internal damage of slopes was revealed. This research finds that the coupling of micro-vibration stress and static stress significantly intensifies the stress concentration on the slope, promotes the development of potential sliding surfaces and the extension of joints, and provides a scientific basis for the prediction of landslide disasters. This helps protect mountain ecosystems and reduce soil erosion and vegetation destruction. The number of cyclic loads has a power function attenuation relationship with the compressive strength of concrete. After 1200 cycles, the strength drops to 20.5 MPa (loss rate 48.8%), and the number of cracks increases from 2.7 per mm3 to 34.7 per mm3 (an increase of 11.8 times). Damage evolution is divided into three stages: linear growth, accelerated expansion, and critical failure. The influence of load amplitude on the number of cracks shows a threshold effect. A high amplitude (>0.5 g) significantly stimulates the propagation of intergranular cracks in the mortar matrix, and the proportion of intergranular cracks increases from 12% to 65%. Grey correlation analysis shows that the number of cycles dominates the strength attenuation (correlation degree 0.87), and the load amplitude regulates the crack initiation efficiency more significantly (correlation degree 0.91). These research results can optimize the design of concrete structures, enhance the durability of the project, and indirectly reduce the resource consumption and environmental burden caused by structural damage. Both studies are supported by numerical simulation and experimental verification, providing theoretical support for disaster prevention and control and sustainable engineering practices and contributing to ecological environment risk management and the development of green building materials.

An innovative method to determine the stress-dependency of Poisson’s ratio of granitic rocks

Uniaxial Compressive test (UCS) results are essential in evaluation the values of Poisson’s ratio. However, according to the suggestion of the International Society for Rock Mechanics, Poisson’s ratio can be determined using three alternative methods: the secant, average and tangent. Applying these methods causes discrepancies in the results; according to our experiences, the differences can be threefold or more. This paper aims to study the process of changes of Poisson’s ratio for intact rock during loading from micro-crack initiation to failure stage. The objective of this theoretical investigation is to establish a straightforward mathematical formulation between σ/σc and intact rock’s Poisson’s ratio value. To outline these changes forty two granite rocks were investigated from Bátaapáti radioactive waste repository (Hungary) and the calculation was performed by using the new formula from the beginning of loading till failure stage at UCS test. In the laboratory test program, Poisson’s ratio derived from standard tests varies with momentary stress; it steadily increases as stress rises until reaching the stress level causing unstable crack propagation. Additionally, the Poisson’s rate follows a linear increase with stress, up to the point of unstable crack propagation stress. The research demonstrated that the proposed equations provide competent values for the root mean squared error value (ranging from 0 to 0.04), the mean absolute percentage error (ranging from 0.6% to 18%) and the mean absolute error (ranging from 0 to 0.04). Contrary to previous ideas, our results suggest that the Poisson’s ratio is not a constant for rigid rocks.

Heterogeneous TiC-based composite ceramics with high toughness

Abstract Electrically conductive carbide ceramics with high hardness and fracture toughness are promising for advanced applications. However, enhancing both electrical conductivity and fracture toughness simultaneous is challenging. This study reports the synthesis of (Ti0.2W0.2Ta0.2Hf0.2Mo0.2)C-diamond composites with varying densities using high-pressure and high-temperature (HPHT) method. The carbides are uniformly dispersed in a titanium carbide matrix, forming conductive channels that reduce resistivity to 4.6×10-7 Ω·m. These composite materials exhibit metallic conductivity with a superconducting transition at 8.5 K. Superconducting behavior may result from d-p orbital hybridization and electron-phonon coupling in transition metal carbides, such as TaC, Mo2C, and MoC. Optimizing intergranular bonding improves the fracture toughness without compromising hardness. The highest indentation toughness value is 10.1 ± 0.4 MPa·m1/2, a 130 % increase compare to pure TiC. Enhanced toughness arises from transgranular and intergranular fracture modes, multiple crack bridging, and large- angle crack deflection, which dissipate fracture energy and inhibit crack propagation. This study introduces a novel microstructure engineering strategy for carbide ceramics to achieve superior mechanical and electrical properties.

Effect of Heat on Physical, Structural, and Microscopic Properties of Sandstone

This research investigates the engineering properties of sandstone through tests performed prior to and following heat treatment. This study concentrated on evaluating the physical and mechanical properties, such as density, compressive strength, and wave velocities, in conjunction with the mineralogical, Cerchar hardness, and basic geochemical characteristics of the rock. Heat treatment was conducted at different temperatures (35 °C, 200 °C, 400 °C, 600 °C, and 800 °C), followed by analyses utilizing X-ray fluorescence (XRF), thin section analysis, and scanning electron microscopy (SEM) techniques. The results were analyzed to assess the influence of heat treatment on rock properties, utilizing Design Expert software for data evaluation. Numerical analysis with FLAC3D was conducted to validate the observed values at various temperature levels, further investigating the impact of the treatment on the engineering properties of sandstone. A significant finding was the reduction in strength, particularly correlated with a decrease in primary wave velocity, which is associated with an uneven distribution of strength within the rock. Increased temperature results in stress concentrations that facilitate crack formation, while variations in grain size significantly influence crack propagation. This study highlights the substantial influence of temperature on the compressive strength and general material properties of sandstone.

Mechanical Response Mechanism and Yield Characteristics of Coal Under Quasi-Static and Dynamic Loading

During deep mining engineering, coal bodies are subjected to complex geological stresses such as periodic roof pressure and blasting impacts, which may induce mechanical property deterioration and trigger severe rock burst accidents. This study systematically investigated the mechanical characteristics and failure mechanisms of coal under strain rates on two orders of magnitude through quasi-static cyclic loading–unloading experiments and split Hopkinson pressure bar (SHPB) tests, combined with acoustic emission (AE) localization and crack characteristic stress analysis. The research focused on the differential mechanical responses of coal-rock masses under distinct stress environments in deep mining. The results demonstrated that under quasi-static loading, the stress–strain curve exhibited four characteristic stages: compaction (I), linear elasticity (II), nonlinear crack propagation (III), and post-peak softening (IV). The peak strain displayed linear growth with increasing cycle, accompanied by a failure mode characterized by oblique shear failure that induced a transition from gradual to abrupt increases in the AE counts. In contrast, under the dynamic loading conditions, there was a bifurcated post-peak phase consisting of two unloading stages due to elastic rebound effects, with nonlinear growth of the peak strain and an interlaced failure pattern combining lateral tensile cracks and axial compressive fractures. The two loading conditions exhibited similar evolutionary trends in crack damage stress, though a slight reduction in stress occurred during the final dynamic loading phase due to accumulated damage. Notably, the crack closure stress under quasi-static loading followed a decrease–increase pattern with cycle progression, whereas the dynamic loading conditions presented the inverse increase–decrease tendency. These findings provide theoretical foundations for stability control in underground engineering and prevention of dynamic hazards.

Nucleation-percolation transition in desiccation cracking of clay.

Crack formation plays a critical role in both natural and engineered materials, influencing the structural integrity and failure of materials from soils to buildings. In this study, the clay desiccation cracking is observed to exhibit a transition of cracking mode from nucleation through avalanche to percolation. This cracking mode transition is dictated by the strain field disorder, which is deliberately regulated by changing the pore structure heterogeneity, with nucleation dominating at low disorder and percolation emerging at higher disorder levels. These transitions are captured by the fractal dimension of the sample-spanning crack, with ∼0.99 for nucleation, ∼1.72 for percolation, and values in between for avalanche, maintaining universality among the four types of clay. Additionally, the fractal dimension increases with strain field disorder in avalanche mode, which can be well captured by a logarithmic relation derived via the fractal tree model. Moreover, this logarithmic relation is universal among both the experimental data of the four types of clay and the numerical data of the classical fuse model. Our findings enhance the understanding of how material heterogeneity governs crack propagation, providing valuable insights for predicting and controlling fractures in natural and industrial processes.

Study on Influence of Grouting on Mechanical Characteristics and Stress Concentration in Hole-Containing Rock

Grouting technology is a pivotal methodology for enhancing the mechanical properties of defective surrounding rock masses in tunnel engineering. Through uniaxial compression tests on intact, hole-containing, and grouted marble specimens, the influence of cement grout filling on the mechanical behavior of marble containing holes was investigated. Based on the experimental results, discrete element method (DEM) models were established for the three types of specimens, revealing the mesoscopic crack propagation mechanisms and stress distribution in potential stress concentration zones during failure. The experimental results demonstrated that the implementation of cement grouting enhanced the strength properties of the specimens by 22.38%. In terms of failure modes, the failure mode of the grouted specimens was similar to that of the intact specimens, and the filling material transformed the failure mode from tensile to shear failure. Numerical simulations revealed differences in microcrack evolution: cracks in the hole-containing specimens initiated near the upper and lower ends of the holes, while cracks in the grouted specimens originated around the filling material, with both types propagating axially. Microcracks in the grouted specimens initiated earlier, but the majority of microcracks in both types developed after peak stress and were predominantly tensile. The stress concentration coefficients for the intact, grouted, and hole-containing specimens were approximately 0.84, 2.25, and 2.96, respectively. The grouted specimens shortened the duration and alleviated the degree of stress concentration in the defect zones. This study elucidates the grouting reinforcement mechanisms in defective tunnel surrounding rock through a multiscale approach, providing theoretical underpinnings for optimizing tunnel support systems and preventing engineering hazards including collapse and rockburst.

Conventional mentality and new findings in plate glass (Part 2)－Crack propagation and divergence phenomena in tempered glass－

In order to investigate fragmentation mechanism in thermally tempered glass, crack propagation and crack divergence were observed with high-speed photography using Cranz-Schardin type camera. Tempered glass of 3.5 mm and 10 mm thick and zone-tempered glass of 5 mm were used as specimens. In addition to the conventionally known bifurcation as crack divergence, branching type was also seen. Differences in propagation energy were seen between bifurcation and branching after at once divergence by Caustics method. Bifurcation and branching mechanism were explained using the concept of stress σ CR which was introduced for explanation crack connection phenomenon seen in zone-tempered glass. The new crack generated by two cracks colliding also existed, and its collision angle of the two cracks had a major influence on its formation by stress σ CR . Stress σ CR was not always explained by stress intense factor K 1 because it has characteristics of time dependance and not necessarily plastic deformation.

Polarization dependences of the laser in 4H-SiC wafer slicing.

This study focuses on the influence of the polarization of incident light in the laser slicing of 4H-SiC wafers. The structure of longitudinal damage within the material after laser modification was measured and analyzed. The impact of laser pulse energy on this structure was studied. Differences in longitudinal damage under different polarization states were compared. In addition, the effects of laser polarization on the modification of line width and lateral crack propagation were investigated. A vector diffraction model was established to analyze the propagation characteristics of beams with different polarization states during focusing. The results indicate that a linearly polarized beam perpendicular to the scanning direction offers superior modification efficacy compared to other directions of linear polarization and circular polarization. Azimuthally and radially polarized beams substantially decrease the length of longitudinal damage and reduce the difficulty of delamination. Compared to the linearly polarized beam perpendicular to the scanning direction, the azimuthally polarized beam reduces the longitudinal damage length by 49.3% and the delamination stress by 47.0%. In comparison, the radially polarized beam reduces the longitudinal damage length by 39.4% and the delamination stress by 53.8%.

In Silico Trials of Prosthetic Valves Replicate Methodologies for Evaluating the Fatigue Life of Artificial Leaflets to Expand Beyond In Vitro Tests and Conventional Clinical Trials.

Background: Fatigue failure of artificial leaflets significantly limits the durability of prosthetic valves. However, the costs and complexities associated with in vitro testing and conventional clinical trials to investigate the fatigue life of leaflets are progressively escalating. In silico trials offer an alternative solution and validation pathway. This study presents in silico trials of prosthetic valves, along with methodologies incorporating nonlinear behaviors to evaluate the fatigue life of artificial leaflets. Methods: Three virtual patient models were established based on in vitro test and clinical trial data, and virtual surgeries and physiological homeostasis maintenance simulations were performed. These simulations modeled the hemodynamics of three virtual patients following transcatheter valve therapy to predict the service life and crack propagation of leaflets based on the fatigue damage assessment. Results and Conclusions: Compared to traditional trials, in silico trials enable a broader and more rapid investigation into factors related to leaflet damage. The fatigue life of the leaflets in two virtual patients with good implantation morphology exceeded 400 million cycles, meeting the requirements, while the fatigue life of a virtual patient with a shape fold in the leaflet was only 440,000 cycles. The fatigue life of the leaflets varied considerably with different implant morphologies. Postoperative balloon dilation positively enhanced fatigue life. Importantly, in silico trials yielded insights that are difficult or impossible to uncover through conventional experiments, such as the increased susceptibility of leaflets to fatigue damage under compressive loading.

Grain-based modeling of crack propagation and stress evolution in marble under coupled thermo-mechanical condition

Grain-based modeling of crack propagation and stress evolution in marble under coupled thermo-mechanical condition

Bridging Overlapping 2D Coarse and Fine Meshes Within the Phase Field Fracture Method

ABSTRACTA framework is proposed to bridge coarse and fine meshes in a single simulation within the phase field method for fracture. Fine meshes are used in the vicinity of localized defects to accurately capture crack initiation, while coarse meshes are used away from initial defects and include only crack propagation paths. This reduces the prohibitive computational times associated with uniformly fine meshes over the entire domain, or with the use of complex adaptive meshes in the phase field method. The coupling between the two overlapping meshes is achieved using a variational formulation in which the energies of the models associated with the fine and coarse meshes are weighted in the superposition zone. Two situations are considered. The first includes the resolution of the phase field problem only in the fine mesh, while the coarse mesh is limited to the undamaged elastic problem. In the second situation, cracks can propagate in both the fine and coarse mesh. Variational formulations and associated finite element implementations are detailed. Numerical examples are presented, showing the potential of this approach to significantly reduce computational costs in the phase field method for cracking without affecting the accuracy.

A Nonequilibrium Thermodynamics‐Based Model to Predict Fatigue Failure in Particle‐Reinforced Metal Matrix Composites

ABSTRACTThe presented fatigue crack growth (FCG) life prediction model for particle‐reinforced metal matrix composites (MMCs) leverages nonequilibrium thermodynamics to characterize the life cycle of crack growth. The model uses an energy balance approach to evaluate FCG rates, focusing on the specific dissipated plastic energy per unit area within the cyclic plastic zone (CPZ), quantified as the area under the cyclic stress–strain curve. The model includes microstructural parameters through strengthening mechanisms, enhancing the model's accuracy. The closed‐form analytical solution shows strong alignment with the experimental data across various particle‐reinforced MMCs, thereby providing reliable FCG life predictions. The key microstructural parameters, including strain amplitude, hardening exponent, strength coefficient, and particle volume fraction, affect the fatigue life and crack propagation resistance. Polar plots of strain amplitude variations further provide insight into the crack propagation around the CPZ, highlighting the influence of microstructural parameters on crack growth.

Study on the surface effect and microscopic mechanism of four cracks emanating from a nanoscale lip-shaped orifice in one-dimensional hexagonal piezoelectric quasicrystals

Based on the complex potential theory and the Gurtin-Murdoch surface/interface elasticity theory, the crack propagation behavior and microfracture mechanism of a nanoscale lip-shaped orifice with four nano-cracks in an infinite one-dimensional (1D) hexagonal piezoelectric quasicrystal (PEQC) material with surface effect are investigated, which is subjected to far-field anti-plane mechanical loads and in-plane electrical loads. By using the analytic function conformal mapping technique, the analytical solutions of the electro-elastic field intensity factors and the energy release rate (ERR) at the crack tip are obtained for partially electrically permeable boundary conditions. The obtained solutions can be reduced to the existing results. Then numerical examples are used to analyze the effects of the geometrical parameters of defects, the crack length, mechanic loadings, electric loading, dielectric constant, and phonon-phason coupling coefficient on the mechanical behavior. The results show that the surface effect has a greater effect on the stress intensity factor than the electric field intensity factor at the nanometer scale. An increase in the length of the lip orifice and the length of the transverse crack at the orifice’s edge tends to accelerate crack growth. Conversely, an increase in the ratio of lip orifice height to crack length can delay crack growth. The research provides novel ideas and methodologies for studying the mechanical and electrical properties of materials at the nanoscale.

Enhanced real-time defect detection for ceramic bearing balls using advanced feature extraction and optimization

Abstract Ceramic bearing balls, characterized by brittleness and low crack propagation resistance, require rigorous quality control during manufacture to ensure reliability and durability. To address the limitations of conventional image-processing methods in detecting intricate and variable surface defects, this study proposes an improved YOLOv11-based defect detection method tailored for ceramic bearing balls. Leveraging its advanced feature extraction capabilities and innovative network architecture, YOLOv11 achieves an optimal balance between real-time performance and high detection accuracy. The proposed model, named cross-stage switchable layer aggregation with You Only Look Once (CSLA-YOLO), incorporates a novel feature extraction module combining a general efficient layer aggregation network with a reparameterization-based switchable cross-stage partial module. Additionally, an optimized loss function was developed to align with the unique characteristics of the ceramic ball defect dataset. The experimental results demonstrate that CSLA-YOLO surpasses the baseline YOLOv11 model, achieving a 1.9% increase in average precision (AP) at an intersection over union (IoU) threshold of 0.5 (mAP50), a 2.9% improvement in mean AP across IoU thresholds from 0.5 to 0.95 (mAP50–95), and a 2.5% boost in total precision. Moreover, CSLA-YOLO outperforms mainstream models such as YOLOv5 and YOLOv8 in performance. When integrated into a custom detection platform, CSLA-YOLO achieves a detection speed of 40 balls per minute while accurately identifying defects as small as 0.1 mm. These results demonstrate its ability to meet the high-precision, real-time detection requirements of ceramic ball manufacturers, offering a robust and efficient solution for high-quality production control.

Experimental Investigation on the Fracture Behavior of PET-Modified Engineered High-Ductility Concrete: Effects of PET Powder and Precursor Composition.

The utilization of polyethylene terephthalate (PET) powder as aggregate in the development of environmentally friendly high-ductility composites (P-EHDC) offers a promising pathway for advancing sustainable and high-performance concrete materials. Despite its potential, the fracture behavior of P-EHDC-particularly under the influence of alkali-activated precursors-remains insufficiently explored. In this study, the fracture performance of P-EHDC was evaluated by varying the precursor composition ratios (GGBS:FA = 4:6, 3:7, and 2:8) and PET powder replacement ratios (0%, 15%, 30%, and 45% by volume). Fracture modes, Mode I fracture energy (GF), and crack propagation behavior were analyzed using the J-integral method. All specimens exhibited ductile fracture characteristics, a clear contrast to the brittle failure observed in conventional concrete. The replacement of 15 vol% PET powder significantly increased GF in precursor systems with higher GGBS content (4:6 and 3:7), and 30 vol% was more effective in fly ash-rich systems (2:8). The J-integral method, which offers broader applicability compared to conventional methods such as the double-K fracture model, provided a more comprehensive understanding of the fracture behavior. The results showed that PET powder reduced the matrix fracture toughness, promoted matrix cracking, and weakened the fiber-bridging effect, leading to enhanced energy absorption via fiber pull-out. At low PET powder replacement ratios (e.g., 15 vol%), the cracking threshold of the matrix was not significantly reduced, while more fibers engaged during the crack instability stage to absorb fracture energy through pull-out. This behavior highlights the synergistic toughening effect between PET powder and fibers in the P-EHDC system. The effect became more pronounced when the PET content was below 45 vol% and the precursor matrix contained a higher proportion of GGBS, leading to enhanced ductility. This study introduces a novel approach to fracture behavior analysis in PET-modified alkali-activated composites and provides theoretical support for the toughening design of high-performance, low-carbon concrete materials.

Phase-field study of the effective fracture energy increase during dynamic crack propagation in disordered heterogeneous materials.

The propagation of a three-dimensional crack in a heterogeneous material is studied using a phase-field model. It is shown that, in the case of randomly distributed inclusions of soft material in a matrix, the nature of the distribution has little effect on the effective elastic properties. However, it significantly affects crack propagation. The less uniform distribution leads to higher thresholds for crack propagation.

Interlaminar fracture toughness in multi-directionally wet-wound fiber board: Cross-structure and parallel alignment

Fiber-reinforced products, renowned for their superior mechanical properties, find extensive applications in aerospace, transportation, and other fields. Single-filament wound (SFW) products suffer from uneven stress distribution due to fiber cross undulations within the same layer, limiting fiber strength utilization. In contrast, multi-filament wound (MFW) products exhibit a parallel arrangement of fibers, which helps avoid stress concentration and enhances impact resistance. Given that interlayer fracture is a critical failure mode affecting product performance, the interlayer performance and fracture mechanisms of MFW products were investigated in this study. A novel specimen preparation method was introduced, taking into account factors such as the winding process, tension control, and resin content. The fracture morphology of the specimen was analyzed to elucidate the relationship between fracture behavior and the winding structure, layer density, and specimen thickness. Results show that the fracture toughness of 5-mm-thick SFW specimens is 28.49% higher than that of MFW specimens. The interlayer pore defects have a greater impact on samples with lower single-layer fiber thickness, where a 20% reduction in single-layer fiber thickness results in a 22.3% decrease in the average strain energy release rate. Decreasing the specimen thickness increases flexibility, facilitating crack propagation along defect areas.

Fluorescence stress probing enhanced crack detection and quantification in ancient Chinese murals for deterioration mechanism analysis

Ancient Chinese murals are precious cultural heritage and vulnerable to structural defects like cracking and delamination, which severely impact their preservation. To address early damage detection and deepen mechanistic insights, this study applies fluorescence stress-sensing technology using mechanochromic 1,1,2,2-tetrakis(4-nitrophenyl)ethene (TPE-4N) coatings on laboratory mock-ups. Under UV light, microcracks (tens of microns) were visualized, quantified, and monitored via photographic analysis. Environmental aging tests revealed distinct defect patterns including failure within pigment layer (cracking) and interlayer debonding (cleavage, cupping, and lifting) with crack propagation rates quantitatively analyzed. Elevated adhesive concentrations and humidity variations exacerbated defects and influenced pigment layer failure modes due to the combined effects of pigment layer strength, interlayer bonding, and stress. Furthermore, crack-propagation dynamics in most samples exhibited three characteristic phases: induction, stable development, and saturation, underscoring the necessity for fatigue monitoring in cultural relic conservation to prevent sudden failure.

XFEM-Based Prediction of Damage in Steel Tee Reducers Subjected to Cyclic Bending

This study examines structural damage in an X52 Grade 8"×4" steel tee-reducer connection under internal pressure and cyclic bending moments. The specific loading orientation significantly affects structural response, visualized through hysteresis curves of bending moment versus angular displacement. Crack propagation analysis employs XFEM technique, with material behavior characterized using combined Ramberg-Osgood models integrated into ABAQUS. Results show the tee-reducer's cyclic response is strongly influenced by 60° oriented bending moments, displaying both symmetrical and asymmetrical patterns. Cracks initiate after a specific number of cycles, with propagation significance varying by bending moment orientation. This research contributes to improved pipeline integrity assessment methods.