Fracture Mechanics Research Articles

Peridynamics analysis of crack propagation in concrete considering random aggregate distribution

The mechanical properties and fracture behavior of concrete are controlled by aggregate characteristics, and the distribution of aggregates is uncertain. Traditional studies on concrete crack propagation mainly conduct deterministic analysis based on the position and size of the aggregates, rarely considering the uncertainty of aggregate distribution. Based on the Peridynamics (PD) theory, random distribution functions are introduced to describe the geometric characteristics and positional parameters of concrete aggregates. Simulating the effect of random distribution of aggregates on concrete crack propagation by presetting random aggregates. For the first time, the Boundary Damage Ratio (BDR) is proposed to quantitatively describe the influence of cement mortar and aggregate on crack propagation, revealing the influence rules of random aggregate parameters on concrete damage provides a new method for studying concrete crack propagation. The research results show that the size and position of aggregates determine the crack propagation path during concrete failure. The BDR can indicate the quality of the concrete grading and the intensity of the aggregate’s guiding effect on crack propagation. It was found that the aggregate size and the BDR follow a Weibull distribution; the larger the aggregate size, the smaller the shape parameter.

Multiscale Analysis of Corrosion Fatigue Crack Propagation Mechanism of High‐Strength Steel in Seawater Atmospheric Environment

ABSTRACTE690 high‐strength steel is widely used in ocean engineering due to its excellent properties. However, it is highly susceptible to fracture and failure under the coupled effects of corrosion and fatigue in marine environments. This paper investigates the corrosion fatigue fracture mechanisms through experimental and theoretical analyses. First, a series of corrosion fatigue tests on E690 steel specimens were conducted to study the crack propagation behavior, and the crack growth parameters were fitted using the Paris equation. Second, scanning electron microscopy was employed to analyze the corrosion fracture characteristics of the E690 steel specimens. Lastly, finite element analysis and molecular dynamics simulations were used to examine the crack propagation process and failure mechanisms from multiscales. The results show that under the influence of corrosion, dislocation accumulation at the crack tip leads to a plastic deformation mechanism dominated by dislocations during crack propagation. Furthermore, the combined effects of anodic dissolution and hydrogen embrittlement accelerate crack growth. In dry air conditions, loading frequency has no significant impact on the crack growth rate, whereas, in corrosive environments, the coupling of low frequency and corrosion shortens the corrosion fatigue life.

Mechanical Properties and Fracture Mechanisms of Nanocomposites of Metal and Graphene with Overlapping Edges.

The fracture mechanism and mechanical response of Ni/graphene nanocomposites under nanoindentation are investigated by molecular dynamics simulations. We analyze the effect of the overlapping area on the microstructural transition, HCP atomic fraction, dislocation density, load-displacement relationship, and stress distribution. It was found that the maximum indentation depth of embedded graphene has a nonlinear dependence relation with the overlapping area, and it becomes smaller at the overlapping width comparable to the indenter diameter. The graphene layer is able to hinder the expansion of the dislocation into the interior of the Ni matrix in the initial stage. The densities of HCP atoms and dislocations in the composite gradually increase with increasing indentation depth. The stress concentration tends to cause nucleation of dislocations below the indentation surface. When the graphene is ruptured, the elastic recovery to some extent occurs in the deformed substrate. This work sheds light on modifying the mechanical properties of metal/graphene composites by tuning the overlapping boundary of graphene.

Interplay between vacancy-induced hydrogen segregation and stress-induced vacancy redistribution causing embrittlement of alpha-iron

ABSTRACT This study proposes a novel mechanism of intergranular fracture in alpha-iron, focusing on the effects of trapped vacancies, H atoms, and their synergistic interplay under tensile strain. We present a methodology for the introduction of H into grain boundaries (GBs) resulting in a realistic distribution by considering H – H interactions. Accordingly, optimal H concentrations were determined under specific environmental conditions for GBs with and without vacancy-induced segregation under zero and 2% tensile strain, respectively. Subsequently, the reduction in cohesive energy at GBs was evaluated at the optimal H concentration under these conditions. In the case of H segregation without vacancies at zero applied strain, the reduction in the cohesive energy ranged approximately from 15% to 35% for all the GB configurations. Eventually, vacancy segregation increased H concentration at the GBs, defined as vacancy-induced H segregation. The vacancy-induced H segregation resulted in a 60%–117% increase in H concentration and a 70%–80% decrease in cohesive energy at a vacancy concentration of 7.491 / nm 2 under zero applied strain. The proposed vacancy-induced H-segregation mechanism explained the delayed fracture in steel. Furthermore, the effect of tensile strain on embrittlement was elucidated, with strain-induced vacancy redistribution and vacancy-induced H segregation synergistically promoting GB decohesion, resulting in a 73%–93% reduction in cohesive energy at the same vacancy concentration.

Evolution characteristics and mechanism of coal fracture under resonance excitation based on computed tomography scanning

AbstractThe resonance of coal reservoir induced by external excitation is a kind of environment‐friendly stimulation technology. In this work, an experimental system was established to carry out the coal resonance fracturing experiments, and the change trend of fracture structure was investigated by computed tomography scanning. The results showed that under the excitation of vibration within the resonance frequency band range, the coal fracture will gradually expand to failure. There are three forms of coal fracture expansion under the condition of resonant, which are the formation of slip zones in coal, the formation of fracture at phase interface and the formation of ‘void’. When the excitation frequency is constant, the natural frequency of coal decreases gradually with the expansion of fractures, resulting in the vibration frequency gradually deviating from the natural frequency of coal, and the fracture propagation behaviour of vibrating coal gradually changes from divergence to convergence.

Enhancing Carbon Fiber-Reinforced Polymers’ Performance and Reparability Through Core–Shell Rubber Modification and Patch Repair Techniques

Carbon fiber-reinforced polymers (CFRPs) are widely used in high-performance applications, but their inherent brittleness and susceptibility to impact damage remain critical challenges. This study investigated the effect of core–shell rubber (CSR) particles as impact modifiers on the mechanical properties of CFRPs and evaluated patch repair techniques for damaged CFRP panels. Mechanical tests, including flexural, tensile, short-beam, fracture toughness, and impact tests, were conducted on reference and CSR-modified specimens to assess their structural performance. The CSR-modified samples demonstrated significant improvements in energy absorption and fracture toughness, with a 50% increase in impact strength and up to 181% improvement in absorbed energy during Mode I fracture testing. However, slight reductions in flexural and tensile strengths were observed due to the softening effect of CSR particles. Fracture surface analysis revealed distinct failure mechanisms, with Scanning Electron Microscopy imaging showing consistent fiber pull-out behavior in tensile and flexural tests, but more stable delamination propagation in CSR-modified specimens during short-beam shear tests. Patch repair effectiveness was assessed through drop-weight impact tests on damaged panels repaired with patches containing CSRs of two thicknesses. Patches of equal thickness to the damaged panel successfully restored structural integrity and enhanced energy absorption by 37% compared with the reference samples, while thinner patches (as a suggestion to reduce production costs) failed to withstand impact loads effectively. Non-destructive testing (NDT) via ultrasonic C-scans confirmed reduced delamination and damage depth in CSR-modified repaired panels, validating the toughening effect of CSR particles. These findings demonstrate the potential of CSR-modified resins to improve CFRPs’ performance and provide effective repair solutions for extending the service life of damaged composite structures, rendering them especially suitable for applications demanding high damage tolerance and durability, including aerospace structures, automotive body panels, and energy-absorbing crash components.

Crankshaft high cycle bending fatigue test method based on the combined extended Kalman filtering algorithm and different failure criterion parameters.

In this paper, an accelerated bending fatigue test method for the crankshaft was proposed based on the combination of the extended Kalman filtering algorithm method (EKF) and different failure criterion parameters. First the intrinsic frequency of the system and the fatigue crack depth were chosen to be the failure criterion parameters based on the test regulation and the theory of fracture mechanics. Then the extended Kalman filtering method was adopted in predicting the remaining high cycle fatigue life of the crankshaft during the experiment process. Finally the predicted fatigue life was selected to replace the actual test results for the key fatigue property parameter analysis. Based on this research, the time duration of the test was reduced obviously without affecting the key analysis parameters obviously. In addition, compared with the intrinsic frequency of the system, the fatigue crack depth is more suitable to be selected as the failure criterion to provide more reasonable enhancing effect. The main conclusions draw from this paper can provide some theoretical guidance for the design and manufacturing process of the part.

Mixed-mode crack growth simulation in rock-like materials with the smoothing gradient-enhanced damage model associated with a novel equivalent strain

Accurately modeling mixed-mode crack propagation in rock-like materials remains challenging due to the complexity of the deformation states and mechanism of fracture throughout the loading history. The objective of this paper is to analyze the damage process in rock-like materials using an enhanced smeared damage model. The mixed-mode failure in rocks is captured using our recently developed smoothing gradient damage model in conjunction with a novel equivalent strain formulation, which is developed by combining both the bi-energy norm equivalent strain and the four-parameter equivalent strain. To validate the accuracy of the developed method, several commonly reported rock fracture examples are considered in which complex crack paths and responses are reproduced and compared with the available experimental data.

Effects of Temperature and Bimodal Microstructure on the Mechanical Properties and Fracture Mechanisms of High-Strength Al-Ni-Cu-Fe Alloy Fabricated through Laser Powder Bed Fusion

This study investigates the mechanical properties of an Al-Ni-Cu-Fe alloy fabricated using laser powder bed fusion (LPBF) technology, evaluated at temperatures ranging from room temperature to 300°C under various strain rates for potential aerospace and automotive applications. Aluminum alloys often face the challenges of maintaining high-temperature strength and stability, limiting their use in demanding environments. The results demonstrate that the LPBF Al-Ni-Cu-Fe alloy maintains strength above 300 MPa at standard strain rates and reaches up to 400 MPa at high strain rates at 300°C, indicating its suitability for lightweight, high-strength vehicles and thermal engineering systems. The high-temperature strengthening mechanisms are attributed to Al9FeNi submicron cellular eutectic walls that impede dislocation motion and precipitation strengthening from Al2Cu. Fracture analysis reveals that localized brittleness limits elongation to 3% at room temperature, with deformation distributed between coarse-grained (CG) and fine-grained (FG) regions. At elevated temperatures (300°C), partial homogenization of FG regions reduces melt pool constraints, promoting local deformation. Therefore, ductility increases significantly under high strain rates as the dispersed Al9FeNi phases become less effective in resisting instantaneous stresses, allowing deformation to overcome melt pool boundaries. At extreme strain rates during impact testing, twinning becomes the dominant deformation mechanism, contrasting with tensile testing. These findings confirm the potential of the LPBF Al-Ni-Cu-Fe alloy as a heat-resistant printed aluminum alloy for high-temperature applications and provide valuable insights into fracture mechanisms within the bimodal microstructure, guiding future alloy optimization.

The electrical discharge characteristics and ignition mechanism of coal mine roof fracture under stress

The electrical discharge characteristics and ignition mechanism of coal mine roof fracture under stress

Unraveling the fracture and failure mechanisms of molybdenum disulfide with various crystalline structures

Unraveling the fracture and failure mechanisms of molybdenum disulfide with various crystalline structures

Adaptive phase-field modeling of fracture propagation in layered media: Effects of mechanical property mismatches, layer thickness, and interface strength

Fracture propagation in layered media is investigated using an adaptive phase-field method. We focus on the interplay between cracks and interfaces, considering both perfectly and imperfectly bonded interfaces. For perfectly bonded interfaces, three-layer models are analyzed to study the effects of mechanical property mismatches, layer thickness, and confinement pressure on crack growth. Results reveal that critical energy release rate mismatch significantly influences the crack geometry, leading to single through-going fractures, middle layer fragmentation, or delamination. There is an inverse relationship between layer thickness and fragmentation, and between confinement pressure and delamination. For imperfectly bonded interfaces, a phase-field method incorporating an interface energy term is introduced and validated with benchmark examples. This model is used to study the combined effects of mechanical property mismatch and interface strength on crack growth. Our findings demonstrate that the interface strength strongly influences the dominant failure mechanism, with high strength favoring mechanical property mismatch-driven fracture and low strength leading to interfacial failure. Finally, the robustness of the proposed method is illustrated through a complex seven-layer model. This study provides valuable insights into the various factors influencing macroscopic failure mechanisms in layered materials.

Facies and mechanical stratigraphy control fracture intensity, topology and fractal dimension in folded turbidite sandstones, Northern Apennines, Italy

Fracture network intensity, topology and connectivity have been frequently analysed using circular scan windows, an efficient method for geometrical properties characterization, although affected by truncation and censoring. Many studies that use circular scans focus on the spatial variation of the geometrical properties in relation to tectonic structures such as faults and folds, and at the regional scale. A lower amount of information is available in the literature on the relations between depositional features, mechanical and petrophysical properties of facies, and the corresponding fracture network geometrical attributes. In this contribution, we focus on these relationships, which are fundamental controlling factors for predicting fracture geometry in the subsurface and for improving modelling in exploration, production and management of reservoirs for fluid exploitation and storage. We characterized these properties in 35 selected turbidite beds of the Marnoso-arenacea Fm., in the Northern Apennines of Italy, exposed along a 250 m-thick section. Moreover, we calculate the fractal dimensions of fracture networks through the box-counting method. Our data indicate that depositional facies control porosity and uniaxial compressive strength, as well as fracture intensity and fracture network topology. We show that fracture intensity is invariant and unrelated to the sandstone facies thickness in medium-grained turbidite beds. On the other hand, a strong control on fracture intensity in fine-grained turbidite beds is also exerted by the thickness of bounding claystone, which is higher when the bounding claystone is thicker. Moreover, we observe that the cross joint pattern and strike could be influenced by the depositional structures.

A fracture mechanics model for predicting tensile strength and fracture toughness of 3D printed engineered cementitious composites (3DP-ECC)

A fracture mechanics model for predicting tensile strength and fracture toughness of 3D printed engineered cementitious composites (3DP-ECC)

Effect of the deposition strategy and endogenous defect pattern on the plastic deformability and the fracture mechanism of 316L stainless steel obtained using material extrusion

Effect of the deposition strategy and endogenous defect pattern on the plastic deformability and the fracture mechanism of 316L stainless steel obtained using material extrusion

Application of equivalent distributed stress concept and modified cohesive zone model in elastic–plastic fracture mechanics analysis of surface cracks

Application of equivalent distributed stress concept and modified cohesive zone model in elastic–plastic fracture mechanics analysis of surface cracks

Experimental study on the dynamic direct tensile fracture mechanism of thermally damaged sandstone

Experimental study on the dynamic direct tensile fracture mechanism of thermally damaged sandstone

Research on the Fracture Mechanism of Bridge Piers Damaged by Jointed Rolling Stones

Research on the Fracture Mechanism of Bridge Piers Damaged by Jointed Rolling Stones

Extended physics-informed extreme learning machine for linear elastic fracture mechanics

Extended physics-informed extreme learning machine for linear elastic fracture mechanics

Experimental Research on the Propagation Mode of 3D Hollow Cracks and Material Strength Characteristics Under Hydro-Mechanical Coupling

The fracture evolution and the strength characteristics of a jointed rock mass under hydro-mechanical coupling are key issues that affect the safety and stability of underground engineering. In this study, a kind of transparent rock-like resin was adopted to investigate the crack initiation and propagation modes of the 3D flaw under hydro-mechanical coupling. The influences of the water pressure and the flaw dip angle on the fracture modes of the 3D flaw and the strength properties of the specimen were analyzed. The experiment results indicated that under the initiation and propagation modes, the 3D flaw presented two types of modes: the low-water-pressure type and the high-water-pressure type. The increase in the water pressure had a significant promoting effect on the crack initiation and propagation, which changed the overall failure mode of the specimen. With the increase in the flaw dip angle, the critical growth length of the wing crack decreased and the initiation moment of the fin-like crack showed a hysteretic tendency. The influences of the water pressure on the crack initiation stress and failure strength had thresholds. When lower than the threshold, the crack initiation stress increased slightly and the failure strength decreased gradually with the increase in the water pressure. Once the threshold was exceeded, both the crack initiation stress and the failure strength decreased significantly with the increase in the water pressure. With the increase in the flaw dip angle, both the crack initiation stress and the failure strength showed a first decreasing and then increasing tendency. The lowest crack initiation stress and the failure strength were found for the specimen containing the 45° flaw, while the highest were found for the specimen containing the 75° flaw. This study helps to deepen the understanding of the fracture mechanism of the engineering rock mass under hydro-mechanical coupling and has certain theoretical and applied value in engineering design and construction safety.