IMPROVEMENT OF FATIGUE LIFE OF AA 7075 USING LASER SHOCK PEENING (LSP) SURFACE TREATMENT TECHNIQUE

Abstract

In general, laser shock peening (LSP) technique is a surface treatment to increase the resistance of metals and alloys to fatigue failure. The aim of the present work is to study the improvement of fatigue life of AA-7075 at constant and variable load by using laser shock peening (LSP) technique with two energies, 250mj and 500mj, on the surface to be treated. The results show that the fatigue life has increased in different percentages at different constant stress amplitude loading. The average improvement in life factor was approximately (1.534) and (1.157) at constant amplitude stress in the range (0.3- 0.8σ_u) for specimens treated with laser shock peening (LSP) technique with 500mj and 250mj respectively. The experimental results of cumulative fatigue damage under variable amplitude stress tests which have been conducted into two-steps program: Low-High stress (156312MPa) and High-Low stress (312156MPa) have also showed improvements in life factor of 1.61 and 1.54 respectively for specimens treated with 500mj laser shock peening (LSP) compared with that of untreated specimens