Chikayoshi Yatomi

Extension Characteristic of an Interface Crack between Dissimilar Isotropic Elastic Material with Various Modulus Ratios

Subject to an inclined load, we obtain the energy release rate for interface cracks in an isotropic elastic material with various modulus ratios. The energy release rate is calculated by the path independent E-integral using the finite element method with a singular element. In the finite element analysis, we impose avoiding the overlap of the extended crack, which may occur in the large angle kinking. Under the maximum energy release rate criterion, we examine the extension behavior of the interface cracks.

On the Examination of the Strong Discontinuity Analysis for a Kinking Discontinuous Surface.

The purpose of this paper is to examine the accuracy of the analysis of the strong discontinuity with a kinking discontinuous surface. We first examine the path independent J-integral and the E-integral formula for a damage model with a kinking cohesive region. As a result, we find that the strong discontinuity analysis based on the E-integral has a high accuracy in view of the energy release rate even when the discontinuous surface kinks.

On the Energy Release Rate of a Crack with a Parallel Interacting Crack.

In this paper, we investigate crack extension behaviors for a linear elastic body with a parallel interacting crack at the neighborhood of the main crack tip. We compute the energy release rate for all the crack tips at the onset of a main crack kinking : E integral is path independent even for a path containing a kinking crack tip and/or the interacting crack tips ; however, for such cases, the well-known J-integral is not path independent. As a result, assuming the isotropy of fracture toughness of the body and judging from the criterion based on the energy release rate, we find that there exist the relative positions of the interacting crack which promote or interrupt the straight extension of the main crack and which make the main crack jump to an extension of an interacting crack.

Numerical Analysis for the Energy Release Rate of Crack in Anisotropic Body under Combined Loadings.

For a crack in an anisotropic elastic body subjected to remote inclined load under a plane stress condition, the energy release rate at the onset of crack kinking is analyzed by numerical analysis. The analysis is based on the path-independent E-integral using the finite element method. The E-integral gives the energy release rate at the onset of crack kinking for hyperelastic bodies. The eight-noded and six-noded isoparametric finite elements are used and the integral paths lie along the sides of the finite element. The numerical integration of the E-integral formula can be evaluated directly by using the nodal forces and nodal displacements. After the path independency is examined in an isotropic elastic body subjected to the remote constant tension stress, it is shown that the results for inclined loads agree very well with the results by Wu (1978). For the anisotropic bodies, in the cases of different planes of symmetry, the energy release rate is computed first under the perpendicular loading to the carck surface and then under the inclined loading. For the former, the results agree well with the perturbation solutions by Gao and Chiu (1992). For the inclined load, the direction of the maximum energy release rate is more sensitive to the direction of loading than the direction of the plane of symmetry.