Surface Yield Strength Gradient versus Residual Stress Relaxation of 7075 Aluminum Alloy
Different distributed residual stresses were introduced by quenching and two shot-peening treatments on 7075 aluminum alloy. The residual stress distributions and micro-hardness profiles in surface layers were measured. Pre-stress coefficient characterizing contribution of local residual stresses to local yield strength is introduced to analyze residual stress relaxation under cyclic loading. Load testing shows that re-distribution of residual stresses and proportional decrease of the pre-stress coefficient would occur in the non-uniform structural residual stresses introduced by quenching, while great stress relaxation and non-linear decrease of the pre-stress coefficient would occur in the uniform surface residual stresses introduced by shot-peening. Additionally, advantages of surface compressive residual stress and micro yield strength on anti-fatigue property and on restraining initiation and propagation of surface micro cracks should be considered in the usually conservative engineering design.
Guojun Zhang and Jessica Xu
Y. H. Hu et al., "Surface Yield Strength Gradient versus Residual Stress Relaxation of 7075 Aluminum Alloy", Advanced Materials Research, Vols. 160-162, pp. 241-246, 2011