CUMULATIVE FATIGUE DAMAGE OF AA7075- T6 UNDER DIFFERENT SURFACE TREATMENTS

Abstract

ABSTRACT SP Peening (SP) and Ultrasonic Peening (UP) treatments with fatigue interaction were studied for 7075A-T6 Aluminum alloy under room temperature (RT) and stress ratio R = -1. Experimental mechanical properties and fatigue behavior of the above alloy were obtained for different conditions of SP & UP surface treatments. The fatigue endurance limit was increased by 3.46% for UIP and 8.57%for SP.The fatigue life were enhanced by 35% for UIT and 54% for SP. Constants fatigue behavior for the mentioned treatments have been also determined. constant as-received metal. Cumulative fatigue damage testing were carried out for two steps loading and it is observed that the fatigue life for LP and UP treated specimens were improved compared to the unpeened results. Two proposed cumulative non-linear models were presented one for SP and other for UP. The proposed models give a good correlation with the experimental fatigue lifetime. The proposed models gave better and conservative prediction of lifetime.