Abstract:

The relation of the fatigue behaviour to the residual stress and plastically deformed microstructure in the surface strain layer of high-strength aluminium alloys is investigated. It is shown that the stress and microstructure strengthenings are two factors improving the fatigue behaviour, moreover, the microstructure strengthening factor plays a main role in the improvement of the fatigue behaviour in the high alternating stress region of S-N curve, but the main contribution to the fatigue behaviour near the fatigue limit is made by the stress strengthening factor. There exists an optimum residual stress field induced by shot peening for a high-strength aluminium alloy, and the maximum compressive residual stress in the field is (σ_r)_op≈σ_s-σ_a.