Computation of energy release rate for interfacial crack in orthotropic bimaterials

The interfacial crack in bimaterials is a very interesting problem for composite materials and which has received particular attention from several researchers. In this study, we will propose a numerical modeling of the interfacial crack between two orthotropic materials using a special mixed finite element. For the calculation of the energy release rate, a technique, based on the association of the present mixed finite element with the virtual crack extension method, was used. The numerical model proposed, in this work, was used to study a problem of interfacial crack in bimaterials. Two cases were treated: isotropic and orthotropic bimaterials. The results obtained, using the present element, were compared with the values of the analytical solution and other numerical models found in the literature.

Stress Intensity Factor Calculation by Smoothed Finite Element Method

Accuracy of stress intensity factor (SIF) determination by three types of smooth finite element method (namely, ES-FEM, NS-FEM and α-FEM) has been investigated. Two types of simple benchmark problems (uniaxial tension of the specimens with central and edge cracks) have been considered. SIF values were calculated by virtual crack extension and modified crack closure integral methods on almost uniform meshes. It has been shown that utilizing of ES-FEM and α-FEM significantly improves accuracy of the results compared with the traditional FEM.

Effective Methods to Determine Stress Intensity Factors for 2D and 3D Cracks

Increasing concern for crack assessment in the pipeline industry motivates analysis to quantify the crack driving force, with the linear-elastic fracture mechanics stress intensity factor, denoted K, viable for many vintage pipeline applications. This paper presents a brief review of numerical methods developed for calculating K via the finite element analysis (FEA) as a background to identify the “best” approaches for such purposes. The existing methods can be categorized into three groups: the displacement-based methods, the stress-based methods, and the energy-based methods. The first group involves the displacement extrapolation method, the quarter-point displacement method, and the displacement correction method. The second group involves the stress extrapolation method and the force method. The third group includes the J-integral method, the stiffness derivative method, the virtual crack extension method, the virtual crack closure technique (VCCT) and ABAQUS direct K output method. Based on the review, four methods were selected and evaluated for a central-cracked plate (CCP) specimen based on the FEA calculations via ABAQUS. The “best” methods are then applied in an analysis of K for through-wall cracks in a line pipe — important reference geometry for leak-versus-rupture analysis.