A NUMERICAL-ANALYSIS OF TIME-DEPENDENT STRESS-FIELDS AHEAD OF STATIONARY INTERFACE CRACKS AT CREEP REGIME .2. INTERFACE CRACKS IN LAYERED MATERIALS

In this study, the behavior of stationary interface cracks in layered materials at creep regime in plane-strain condition and pure opening d ominated mode-I load state was studied numerically. Cracks located at the interfaces of the transitional layer between the elastic and creep ing sectors and cracks at the center of the transitional layer are con sidered. The role of the layer thickness on the evolution of the stres s fields at creep regime is also elucidated. The results indicate that both the location of the interface crack and the extent of the transi tional layer strongly influence the amplitude of the stress field (C) at steady-state in layered materials. Also, the time required to achi eve steady-state varies significantly with these parameters. The intro duction of a transitional layer to the interface of the elastic-creepi ng bimaterials significantly elevates the stress values ahead of the i nterface cracks under identical applied load levels at creep regime. D ue to large variation in the distribution of the stresses ahead of the crack tip, depending on which side of the transitional layer, the cre ep growth rates of such interface cracks will be significantly differe nt from each other at creep regime under identical loading for a given layered material. (C) 1997 Elsevier Science Ltd. All rights reserved.