Papers by Keyword: Singular Stress Field

Abstract: In this study, the fatigue fracture criterion of the adhesively bonded joint is discussed. The singular stress field is formed at the interface end in the butt joint and causes the debonding fracture. The singular stress field is represented with the intensity of singular stress field (ISSF). The static debonding strength of the adhesively bonded joints is expressed with a constant value of critical ISSF. The rotating-bending fatigue tests are carried out on the butt joints of 15mm in diameter with four different adhesive thicknesses of 109 - 159μm, 209 - 265μm, 393 - 432μm and 754 - 841μm. The evaluation method by the ISSF is applied to the experimental results. It is found that the fatigue strength of the butt joint can be expressed with the constant value of critical ISSF.

Abstract: Extensive studies have been carried out to deal with the stress singularity of V-notch problems in linear elasticity theory. In fact, the plastic deformation consequentially arises in the notch tip region because of the high stress concentration. The solution of linear elasticity is not adequate to explain the fracture failure of V-notch structures. Because of the difficulties of the nonlinear analysis and the singularity behavior, few results are given for the plastic stress singularities of general V-notch structures. In this paper, the plane V-notch structures in a power law hardening materials are considered. The Von Mises yield criterion and the plasticity total theory are adopted when the materials arise in plastic status. Similar to methods used in the elastic analysis, the plastic stress field near V-notch tips is assumed as an asymptotic expansion with respect to the radial coordinate originating from the notch tip. The governing equations of plastic behavior of plane V-notch are transformed to eigenvalue problems of nonlinear ordinary differential equations (ODEs) contained by the stress singularity order and the associated eigenfunctions. Consequently all of the stress singularities who are less than zero and the associated eigenvectors are accurately determined for the plane V-notches with arbitrary opening angle.

Abstract: In previous studies, the elastic stress field near the crack tip was investigated by digital image correlation and the 2-D intelligent hybrid method. In this study, the 2-D nonlinear hybrid method was developed to analyze the elastic-plastic singular stress field near the crack tip from the displacement data obtained by digital image correlation. Then, the 2-D nonlinear hybrid method was carried out to evaluate stress, strain and J integral. The 3-D elastic-plastic finite element method was conducted on the same specimen as the experiment, and the validity of this approach was discussed from the comparison of the experiment and 3-D finite element method.