This study investigates the fracture behavior of bimaterials, specifically focusing on the Alumina/Silver interface under mechanical, thermal, and thermo-mechanical loading conditions. Through the analysis of Stress Intensity Factors (SIFs) across various crack lengths, temperatures, and along multiple regions and fronts of the crack, we provide valuable insights into the distribution and the nature of stresses, shedding light on how different loading conditions influence crack propagation. Our findings show that, under mechanical loading, the tensile mode SIF (KI) exhibits a straightforward relationship with applied stress, increasing with crack length. In contrast, under thermal loading, KI generally decreases on the surface as the temperature rises, while it increases within the interface, highlighting the complex interplay of thermal expansion and the mismatch of material properties. The thermo-mechanical case combines these effects, further amplifying the role of residual stresses from manufacturing processes and thermal stresses, significantly affecting SIFs and crack growth, especially in bimaterial interfaces. These results contribute to a deeper understanding of fracture mechanisms in hybrid materials.

The permanence and durability of mechanical and structural elements with discontinuities such as cracks and voids require the calculation of SIF (stress intensity factors) with reasonable fidelity. SIF is a crucial parameter that predicts crack growth and failure behavior by quantifying the stress field neighboring the crack tip. Therefore, understanding the sophisticated characteristics of the stress fields in the vicinity of discontinuity requires an effective way of calculating SIFs. Currently, there are numerous methods to calculate SIF, such as FVM (Finite Volume Method), FEM (Finite Element Method), BEM (Boundary Element Method), XFEM (Extended Finite Element Method), Phase field method and Meshfree methods. For an extended period, FEM is one of the leading methods in solving fracture mechanics problems. Though FEM is quite robust in dealing with several engineering problems, it has got its inherent drawbacks to deal with singular fields like discontinuities. Hence to reasonably capture moving discontinuities, finer meshes near the discontinuous field are required that demand more computation effort and time. To alleviate the above drawback of FEM, this study employed Extended Isogeometric Analysis (XIGA) to efficiently and effectively determine the SIFs in the case of fissured plates as benchmarking fissure problems. In this study SIFs in relation to crack length were examined for edge and center cracked plates and results were compared with the theoretical values.

Fatigue crack growth studies require models that accurately predict component life with low uncertainty. Despite the large number of proposed models, there is no clarity on their applicability, which justifies a comparative analysis between some of them. The dual boundary element method (DBEM) was applied for cracked bodies, whereby the stress intensity factors (SIF), the growth rate, and the number of cycles were computed. Three crack increment models were studied under constant amplitude fatigue loads: the Paris, the Klesnil-Lucas, and the Forman models. Results were validated with experimental literature and through the finite element method, indicating that each model represents a specific zone of the crack growth curve. Klesnil-Lucas model reproduces the region near the fracture threshold, Paris fits the controlled crack growth zone, whereas Forman’s model recreates the unstable fracture zone, i.e., when the stress intensity factor approaches the material’s fracture toughness. The J-integral with stress field decomposition gave errors below 0.8% for mode I. Results were similar for the propagation path and the number of cycles to those obtained with the finite element method, with errors of about 3% considering different K-effective approaches. Klesnil-Lucas accurately predicts the number of cycles with an error margin below 3%, considering the curved region in the growth rate at the propagation onset, while the Paris model becomes very conservative, predicting values up to 50% lower than experimental data. The Klesnil-Lukas model is advised for simulating the entire crack propagation.

Solution for a normally loaded infinite isotropic plate containing five cracks with coalesced yield zones is obtained using a complex variable method. Influence of coalesced yield zones on the load bearing capability of the infinite plate is analyzed. Analytical expressions for stress intensity factors, displacement components and crack opening displacement (COD) are obtained. Numerical study is carried out to determine the yield zone length, applied load ratio and COD. The numerical results are reported graphically between some important parameters.

The present work aims to investigate the effect of an edge crack on the stress concentration around the circular hole surrounded by Functionally Graded Material (FGM) in an infinite plate subjected to uniaxial tensile load. The numerical investigation has been carried out using Extended Finite Element Method (XFEM). Two cases have been analysed in this work, i.e. the whole plate made up of radial FGM and homogeneous material plate having radial FGM layer around the hole. Young’s modulus of FGM varies according to exponential and power law function. The relations of stress intensity factor (SIF) and stress concentration factor (SCF) with normalised crack length, Young’s modulus ratio, FGM layer thickness and power law index have been presented. It has been observed that the FGM layer case has low SCF around hole than FGM plate case in presence of an edge crack.

The corner point singularity of surface cracks by finite element method (FEM) has become a numerical concern decades ago. The literature showed that the stress intensity factors (SIFs) at the corner points were often excluded. Further, most SIFs were reported for larger ratios of the crack depth over cylinder diameter. This paper presents the SIFs (Modes I, II and III) of a semi-elliptical surface crack at a solid round bar under torsion. The tetrahedral and hexahedral elements were used in the finite element modelling. The effects of the loading mode and the crack aspect ratio on the corner point singularity were discussed. The tetrahedral meshing was generally observed to be more suitable for modelling relatively small surface cracks, particularly in respect to the corner point singularity. For all loading modes, the SIFs away from the corner points of using the tetrahedral meshing were found to have fairly good agreement with those by dual boundary element method (DBEM).

Fatigue crack growths of a corner crack emanating from a pinhole of a solid cylinder subjected to cyclic torsion loading were simulated using a Dual-Boundary Element Method (DBEM) based software. For a given crack aspect ratio a/c, larger Mode I stress intensity factor (SIF) was observed at a larger pinhole diameter. Any given initial crack aspect ratio a/c would evolve towards unity. The final evolving crack aspect ratio a/c was shown to be larger than 1. For the same given initial crack length a, a smaller crack depth c was found to result in a shorter fatigue life. A shorter fatigue life yielded a larger orientation angle of the crack growth path.

One of the specimens to investigate the mode-I fracture toughness of rock and geo-materials is semi-circular bend (SCB) specimen. In general, initial cracks in rock test specimens are produced in two shapes: straight-edge cracks and chevron notches. The ISRM suggested SCB specimen has straight shaped notch. However, use of V-shaped (or chevron) notch in the SCB specimen is preferred because of some technical difficulties associated with making a sharp crack or creating pre-crack to conduct the experimental tests. In this paper, the minimum dimensionless stress intensity factor of cracked chevron notched semi-circular bend (CCNSCB) specimen is determined using finite element analysis with ABAQUS software. An analytical method, (i.e. Bluhm’s slice synthesis method) is used to verify the results. It is shown that a good agreement exists between the numerical data and theoretical results.