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In this paper the frictional heating effect on the propagation of surface crack under Hertzian contact loading based on the fracture mechanics is investigated. For the theoretical analysis of this effect, we estimated stress intensity factor of surface crack -tip in shear mode under Hertzian contact sliding friction. Theoretical results showed those thermal loads (Th), Peclet number (Pe) and crack angle (β) are very important factors on the propagation of surface crack under Hertzian contact loading. When thermal load(Th) and Peclet number(Pe) are constant, maximum variable range of stress intensity factor, ΔKII, is located in the range of surface crack angle 130°~150°. Non-dimensional parameter T consisting of thermal load and peclet number for evaluating ceramic wear behavior is introduced.

We consider an elastic body with pre-existing crack which is subjected to external loadings. It is assumed that the constitutive relation is of power-law type (Ramberg/Osgood model). Several fracture criteria are based on the energy release rate, which is the derivative of the potential deformation energy with respect to the crack length. The goal of this paper is to derive the Griffith-formula and the Eshelby–Cherepanov–Rice integral for the energy release rate of this nonlinear model taking into account the actual regularity of the corresponding displacement and stress fields.

We consider crack propagation in brittle nonlinear elastic materials in the context of quasi-static evolutions of energetic type. Given a sequence of self-similar domains nΩ on which the imposed boundary conditions scale according to Bažant's law, we show, in agreement with several experimental data, that the corresponding sequence of evolutions converges (for n → ∞) to the evolution of a crack in a brittle linear-elastic material.

The girth welds of the steel connections in subsea pipelines are subjected to combined fatigue loading and static tensile loading in most of their service life. In this paper, both experimental and numerical studies are presented on the fatigue behavior of Carbon Fiber Reinforced Polymer (CFRP) composites repaired steel connections under combined loads. In the experimental program, each specimen is designed to be formed by two steel plates joined together by single-sided girth welds as a simplification of subsea pipelines, and reinforced by CFRP sheets on one side. The applied loads include a constant amplitude tensile cyclic load combined with a tensile static load, which is perpendicular to the cyclic load. The experimental results reveal that the superimposition of the tensile static load leads to a prolonged fatigue life. The effect gets more noticeable with increased tensile load. To further this study, an analytical model is developed on the basis of the Linear Elastic Fracture Mechanics (LEFM) method. It can be used to predict the fatigue lives efficiently. The comparisons with experimental results reveal that the analytical method is able to reasonably predict the fatigue crack growth life. Parametric studies are therefore performed using the proposed analytical model. The influence of CFRP layers, stress range and tensile static stress on the fatigue life was evaluated.

In this paper, a procedure based on the transfer matrix method for obtaining the exact solution to the equations of free vibration of damaged frame structures, considering the effects of axial extension, shear deformation, rotatory inertia, and all compliance components arising due to the presence of a crack, is presented. The crack is modeled by a rotational and/or translational spring based on the concept of linear elastic fracture mechanics. Only the in-plane motion of planar structures is considered. The formulation is validated through some examples existing in the literature. Additionally, the mode shapes and natural frequencies of a frame with pitched roof are provided. The variation of natural frequencies with respect to the crack location is presented. It is concluded that considering the axial compliance, and axial-bending coupling due to the presence of a crack results in different dynamic characteristics, which should be considered for problems where high precision is required, such as for the crack identification problems.

This paper presents the stress intensity factors for internal and edge cracks in multi-layer glass/epoxy plain weave fabric laminates subjected to uniaxial tension load at cryogenic temperatures. Cracks are considered to have occurred in the transverse fiber bundles. Finite element analysis of the limiting case when the cracks extend to the interfaces between two fiber bundles is carried out. Special singular elements containing the exact stress singularity are used to model the singular stress field near the crack tip. Numerical results for the stress intensity factor at cryogenic temperatures are displayed graphically and discussed in detail.

In this paper, we propose a Galerkin-based smoothed particle hydrodynamics (SPH) formulation with moving least-squares meshless approximation, applied to solid mechanics and large deformation. Our method is truly meshless and based on Lagrangian kernel formulation and stabilized nodal integration. The performance of the methodology proposed is tested through various simulations, demonstrating the attractive ability of particle methods to handle severe distortions and complex phenomena.

In this work, the natural neighbor radial point interpolation method (NNRPIM) is extended to the numeric analysis of crack propagation problems. Here, the advanced discretization meshless technique is combined with a linear elastic crack growth algorithm. The algorithm simulates the crack propagation by displacing iteratively the crack tip, which consequently requires a local remeshing. In each iteration, it is estimated the stress state in the crack tip and afterwards the direction of the crack propagation is obtained considering the maximum circumferential stress criterion.

The required local remeshing does not represent a numeric difficulty for the NNRPIM. The main advantage of the NNRPIM is its capability to fully discretize the problem domain using only an unstructured nodal distribution. Being a truly meshless method, the NNRPIM is able to define autonomously the nodal connectivity and the background integration mesh.

The classic NNRPIM formulation permits to enforce the nodal connectivity by means of two kind of influence-cells: first degree influence-cells or second degree influence-cells. This work investigates the influence of the nodal connectivity on the simulated crack propagation path. Thus, demanding benchmark crack propagation examples are studied and the obtained results are compared with reference solutions available in the literature.

The meshfree methods in computational mechanics have been actively proposed and increasingly developed in order to overcome some drawbacks in the conventional numerical methods. Over past three decades meshfree methods have found their way into many different application areas ranging from classical astronomical problems to solid mechanics analysis, fluid flow problems, vibration analysis, heat transfer and optimization to the numerical solution of all kind of (partial) differential equation problems. The present work is an effort to provide a comprehensive review of various Meshfree methods, their classification, underlying methodology, application area along with their advantages and limitations. Key contributions of mesh free techniques to the area of fracture mechanics have been discussed with applications of element free Galerkin method (EFGM) to fracture analysis as primary concern.

A convenient evaluation method is proposed for the debonding adhesive strength in terms of the intensity of singular stress field (ISSF) appearing at the end of interface. The same FEM mesh pattern is applied to unknown problems and reference problems. It is found that the ISSF is obtained accurately by focussing on the FEM stress at the adhesive corner. Then, the debonding condition can be expressed as a constant value of critical ISSF. The usefulness of the present solution is verified by comparing with the results of the conventional method.

The aim of the present paper was to explore the effect of initial lesions on the course of femoral head necrosis. A fracture mechanics model of the femoral head was developed and validated using the computed tomography (CT) scan images of a healthy volunteer and material mechanics test results of fresh femur samples. The dynamic development of stresses and fractures of the femoral head with various initial lesions were simulated under various loads. The results showed that the initial lesion of the femoral head spreads faster and collapses deeper as the load increases. The location of the initial lesion has a significant effect on the collapse of the femoral head. The lesions in the anterior and lateral areas of the femoral head are more likely to accelerate the collapse of the femoral head than the lesions in other areas. This study is helpful in predicting the collapse risk and guiding the daily activities of patients with femoral head necrosis. Additionally, this study helps doctors to make better decisions about treatment options.

The fatigue crack propagation analysis based on the SPH framework “SPH-Fatigue” is accelerated by using the single precision program on GPU. It is found that the single precision program slightly disorders the stress wave but doubles the computational speed. In addition, the computational results of the fatigue crack propagation by the single precision program show almost the same crack shapes as the experimental ones. Accordingly, it is concluded that the use of the single precision program is one of the choices to accelerate the SPH-Fatigue computation.

Poisson's ratio is an important factor for fracture of functionally graded materials (FGMs). It may have significant influence on fracture parameters (e.g. stress intensity factors and T-stress) for a crack in FGMs under mixed-mode loading conditions, while its effect on such parameters is negligible in homogeneous materials. For instance, when tension load is applied in the direction parallel to material gradation, the fracture parameters may show significant influence on the Poisson's ratio. This paper uses a new formulation, so-called non-equilibrium formulation, of the interaction integral method. It also presents a few numerical examples where Poisson's ratio is assumed either constant or linearly varying function, and Young's modulus is assumed to be exponential or hyperbolic-tangent function.

Ceramic foams made by replica techniques containing sharp-edged cavities, which are potential crack initiators and therefore have to be analyzed using fracture mechanical methods. The ceramic foams made of novel carbon bonded alumina are used as filters in metal melt filtration applications, where the filters are exposed to a thermal shock. During the casting process the filters experience a complex thermo-mechanical loading, which is difficult to measure. Modern numerical methods allow the simulation of such complex processes.

As a simplified foam structure an open Kelvin cell is used as a representative volume element. A three-dimensional finite element model containing realistic sharp-edged cavities and three-dimensional sub-models along these sharp edges are used to compute the transient temperature, stress and strain fields at the Kelvin foam. The sharp edges are evaluated using fracture mechanical methods like the $J$-integral technique.

The results of this study describe the influence of the pore size, relative density of the ceramic foam, the heat transfer and selected material parameters on the fracture mechanical behaviour.

A robust boundary element numerical scheme is presented to study crack-face frictional contact in cracked fiber reinforced composite materials. The dual boundary element method is considered for modeling fracture mechanics on these materials. The formulation is based on contact operators over the augmented Lagrangian to enforce contact constraints on the crack surface. Moreover, it considers a Halpin–Tsai macro model for fiber reinforced composite materials which makes it possible to take into account the influence of micromechanical aspects such as: the fibers’ orientation, the fiber’s aspect ratio or the fiber’s volume fraction, estimating the mechanical properties of these composite materials from the known values of the fiber and the matrix. After solving a crack face frictional contact benchmark problem, the capabilities of this methodology are illustrated by studying the influence of not only these micromechanical aspects but also crack face frictional contact conditions on a fractured carbon fiber-reinforced polymer under compression.

Lattice materials, such as honeycombs, are remarkable in their ability to combine high stiffness, strength and toughness at low density. In addition, the recent and pervasive development of additive manufacturing technologies makes it easier to produce these cellular materials and opens new possibilities to improve their properties by implementing small modifications to their microstructure. Such developments open new opportunities towards the design of new classes of architectured materials. For example, recent computational studies have shown that honeycombs with lattice density gradients have a fracture energy under tensile loading up to 50% higher than their uniform counterparts. The aim of this study is to provide experimental evidence for these promising numerical results. To achieve this, single-edge notched tension specimens, with a honeycomb lattice structures, were manufactured by stereolithography using a ductile polymer resin. The performances of three different honeycombs were compared: (i) a uniform sparse lattice, (ii) a uniform dense lattice, and (iii) a gradient lattice with alternating bands of sparse and dense lattices. The results indicated that specimens with a density gradient may achieve a work of fracture per unit volume that is up to 79% higher than that of a uniform lattice.

Human colon carcinoma (HCT-8) cells show a stable, metastasis-like phenotype (MLP) when cultured on appropriate soft substrates (21 ~ 47 kPa). Initially epithelial (E) in nature, the HCT-8 cells become rounded (R) and show a number of metastatic hallmarks after only seven days of culture on soft substrate (Tang et al., [2010] "Mechanical force affects expression of an in vitro metastasis-like phenotype in HCT-8 cells," Biophysical Journal99, 2460–2469; Tang et al., [2012a] "Attenuation of cell mechanosensitivity in colon cancer cells during in vitro metastasis," PlosONE7, e50443). Here, we studied the surface nonspecific adhesion of HCT-8 cells throughout the in vitro metastasis process. A novel bio-MEMS force sensor was used to measure the cell-probe nonspecific adhesion. The adhesion characteristics are analyzed using fracture mechanics theory. Our results indicate that the post-metastatic HCT-8 cells (dissociated R cells) display remarkably diminished surface adhesion and are potentially more invasive than original pre-metastatic HCT-8 cells (E cells). To the best of our knowledge, this is the first report of quantitative data showing the changes in cancer cell adhesion and other cellular mechanical properties during the expression of in vitro metastasis-like phenotype.

The main contribution of this paper is to propose an IGA formulation to model stationary cracks within orthotropic media by combination of XFEM enrichment functions and level set functions. For modeling cracks in solution field crack face and crack tips are considered separately and the control points that are related to each part are enriched with different approaches. The control points related with the crack face are enriched using the Heaviside enrichment functions. Level set functions are used to distinguish the control points correspond to crack tips and crack face. Stress intensity factors are employed to compare the results of XIGA with other methods. Several numerical examples considering crack inclination angle and material orientation axis are solved to verify the XIGA formulation. The results fairly conform to available methods, however less DOFs are used in XIGA.

In the present work, the Natural Neighbor Radial Point Interpolation Method (NNRPIM) is used to simulate the crack growth phenomenon in brittle materials. In order to discretize the problem domain, the NNRPIM only requires an unstructured nodal distribution. With the spatial information of the computational nodes, the NNRPIM is capable to automatically establish the nodal connectivity and to construct the interpolation functions. Additionally, using the natural neighbor geometrical concept, the NNRPIM is able to obtain, from the unstructured nodal distribution, the integration background mesh required to numerically integrate the integro-differential equations ruling the studied physical phenomenon. In this work, a crack opening path algorithm is adapted and combined with the NNRPIM. The developed algorithm is able to predict the crack growth by relocating iteratively the crack tip. The stress field in the vicinity of the crack tip is determined in each iteration and then, using the maximum circumferential stress criterion, the direction of the crack propagation is calculated. Here, the repositioning of the crack tip requires a local re-meshing. However, due to the flexibility of the natural neighbor concept, the local re-meshing do not represent a numerical difficulty. Additionally, in order to show the efficiency of the proposed approach, several demanding crack growth benchmark examples are solved.

The strain energy release rate $G$ is of prime importance in composite materials fracture mechanics. In order to experimentally and numerically evaluate this parameter in the case of quasi-isotropic and angle-ply (AP) woven-ply thermoplastic (TP) laminates, single edge notched (SEN) specimens have been subjected to monotonic tensile loading at $T>T_g$ when the toughness and the viscous behavior of the (TP) matrix are exacerbated. From the simulation standpoint, a particular attention was paid to the type of meshing as well as its refinement in the vicinity of the crack tip where the triaxiality rate leads to significant stress concentrations. For this purpose, a linear spectral viscoelastic and a generalized Norton-type viscoplastic models have been used. A comparison between two types of meshing (radiant and concentric) has been conducted. Both types of meshing allow us to define crowns in order to represent the surface of the integration ring around the crack tip. These crowns are necessary to evaluate the strain energy release rate $G_I$ in opening mode using $G_{\theta }$-integral computation. Both overstress and overstrain profiles near the crack tip were investigated and validated using theoretical stress fields derived from the linear elastic fracture mechanics (LEFM) framework and overstrain fields obtained from digital image correlation (DIC) to verify the model’s ability to provide accurate mechanical fields at singularity zones.