2-PARAMETER CHARACTERIZATION OF THE NEAR-TIP STRESS-FIELDS FOR A BI-MATERIAL ELASTIC-PLASTIC INTERFACE CRACK

A particular case of interface cracks is considered. The materials at each side of the interface are assumed to have different yield strengt h and plastic strain hardening exponent, while elastic properties are identical. The problem is considered to be a relevant idealization of a crack at the fusion line in a weldment. A systematic investigation o f the mismatch effect in this bi-material plane strain mode I dominati ng interface crack has been performed by finite strain finite element analyses. Results for loading causing small scale yielding at the crac k tip are described. It is concluded that the near-tip stress field in the forward sector can be separated, at least approximately, into two parts. The first part is characterized by the homogeneous small scale yielding field controlled by J for one of the interface materials, th e reference material. The second part which influences the absolute va lue of stresses at the crack tip and measures the deviation of the fie lds from the first part can be characterized by a mismatch constraint parameter M. Results have indicated that the second part is a very wea k function of distance from the crack tip in the forward sector, and t he angular distribution of the second part is only a function of the p lastic hardening property of the reference material.