Measurement of Residual Stress at Impact Pit of Aluminum Alloy by Micro Indentation Method

Defects on surface of metal structures (such as damage caused by impact or scraping) may seriously affect their fatigue life. The measurement of local residual stress at defects is of great significance to the assessment of initial crack fatigue life. The finite element (FE) method was used to simulate the processes of impact pit defects generation in aluminum alloy 2A12 and micro indentation experiments at typical points of the pit. Based on the FE simulation, the accuracy of the residual stress calculation at the defect using the Lee model was evaluated. The results show that the error of estimated value of residual stress at the bottom of the pit (in equiaxial condition approximately) is less than 6% compared with the standard value obtained from finite element simulation, and the error of estimation of the residual stress on the edge of the pit (in non-equiaxial condition) is close to 25%. By correcting the Lee model, the error of estimation on the pit edge is reduced to less than 8%.