Fatigue-induced grain coarsening and crack growth behavior in ultrafine-grained copper under different loading histories

Abstract

The crack growth direction in ultrafine-grained copper under constant stressing depends on the applied stress amplitude. The growth direction is perpendicular to the loading axis at low stresses and inclines at 45 degrees to the loading axis at high stresses. To clarify physical causes of such different behaviors at high and low stress amplitudes, two-step fatigue stress tests are conducted. The formation mechanisms of crack paths at high and low stress amplitudes and effect of pre-stressing on subsequent crack growth direction are discussed considering the morphological features of surface-damage formed under different cyclic-stress histories. (C) 2013 Elsevier Ltd. All rights reserved.