Strain Life of Shot Peening AA 2024-T4

Abstract

This research involved studying the effect of shot peening, by steel balls, on Low Cycle Fatigue (LCF) of aluminum alloy AA 2024-T4 at different peening times (5, 10, 15, 20 & 30 min). Shot peening helped to increase the tensile and yield strength (σ u , σ y) to reach the highest values at the time of 15 minutes and then declined. Strain hardening coefficient (n) increased to some extent, which recorded an indication of the possibility of continued cyclic hardening behavior of the alloy during LCF after the peening. LCF tests showed that un-peened AA 2024-T4 was more resistant especially at rates lower than 9x10 3 cycles, then for 15 minutes. shooting, a pronounced improvement in LCF life down to the number of cycle's equal to10 5 cycles. SEM showed that the size of dimples, length of secondary cracks and the voids increased for peened specimens were especially at high cyclic strains near the strains of σ u .