Fatigue-life prediction of SiC aluminum composite using a Weibull model

The feasibility of the acoustic emission technique in predicting the residu al fatigue life of 6061-T6 aluminum matrix composite reinforced with 15 vol .% SiC particulates (SiCp) is presented. Fatigue damages corresponding to 4 0, 60 and 80% of total fatigue life were induced at a cyclic stress amplitu de. The specimens with and without fatigue damage were subjected to tensile tests. The acoustic emission activities were monitored during tensile test s. The number of cumulative AE events increased exponentially with the incr ease in strain during tensile tests. This exponential increase occurred whe n the material was in the plastic regime and was attributed mainly to SiC p articulate/matrix interface decohesion. Cumulative events during post fatig ue tensile tests reduced with a decrease in the residual fatigue life. Base d on the high cycle fatigue damage accumulation model, a Weibull probabilit y distribution model is developed to explain the post fatigue AE activity o f specimens during tensile tests. Using the model, the residual fatigue lif e can be predicted by testing the specimen in tension and monitoring the AE events. In high cycle fatigue, it was observed that the residual tensile s trengths of the material did not change significantly with prior cyclic loa ding damages since the high cycle fatigue life was dominated by the crack i nitiation phase. (C) 1999 Elsevier Science Ltd. All rights reserved.