A NUMERICAL-ANALYSIS OF TIME-DEPENDENT STRESS-FIELDS AHEAD OF STATIONARY INTERFACE CRACKS AT CREEP REGIME .1. INTERFACE CRACKS IN BIMATERIALS

In this study, the behavior of stationary interface cracks at creep re gime in plane-strain condition and pure crack opening dominated mode-I load state is investigated numerically. The bimaterials considered ar e elastic-creeping with power law and bimaterials having identical ela stic properties but creeping at different rates. The results indicate that the amplitude of the crack tip singularity is dominated by the fa ster creeping sector. Neither the elastic properties (hence the initia l elastic stress distribution) nor the creep properties of the slower creeping sector significantly affect the evolution of the C value for the interface cracks under identical applied loading condition. At st eady-state, the angular distribution of the stresses ahead of the inte rface cracks in the faster creeping sector resembles the HRR stress si ngularity that occurs ahead of the cracks in homogeneous materials at creep regime. However, the observed C values for the interface cracks were about half of that seen for the crack in the homogeneous case un der identical applied loading; and the occurrence of much larger radia l, shear and hydrostatic stress components at significant distances ah ead of the interface cracks was observed. On the other hand, the magni tudes of the normal stress component remained relatively the same for both crack types. Based on these observations, the possible growth rat e of the interface cracks due to creep damage is also discussed. (C) 1 997 Elsevier Science Ltd. All rights reserved.