Product life and damage tolerance can be significantly improved by modifying residual stresses in the near surface region. For instance, high compressive residual stresses can lead to a retardation of fatigue crack growth. Various mechanical surface treatment processes with different process characteristics are available to affect the residual stress state and can be used to increase the fatigue resistance of the product.
In this study, three promising residual stress engineering techniques namely laser shock peening (LSP), hammer peening (HAM) and deep rolling (DR) were applied to generate deep compressive residual stress fields in the aluminum alloy 7075-T6, see Figure 1. The aim of the study is to investigate the effects on microstructure and fatigue crack growth behaviour of the three different residual stress techniques using comparable residual stress profiles in terms of the compressive stress area under the curve (mm × MPa). Fatigue crack growth tests were carried out on C(T)100 specimens in accordance with ASTM E647. All the residual stress engineering techniques resulted in improved resistance to fatigue crack growth compared to the untreated base material. Based on microfractographic investigations, it was found that the crack
closure effect due to the presence of residual compressive stresses is mainly responsible for retardation of fatigue crack growth.