A new computational methodology is proposed for fatigue life prediction of notched components subjected to variable amplitude multiaxial loading. In the proposed methodology, an estimation method of non‐proportionality factor (F) proposed by authors in the case of constant amplitude multiaxial loading is extended and applied to variable amplitude multiaxial loading by using Wang‐Brown's reversal counting approach. The pseudo stress correction method integrated with linear elastic finite element analysis is utilized to calculate the local elastic‐plastic stress and strain responses at the notch root. For whole local strain history, the plane with weight‐averaged maximum shear strain range is defined as the critical plane in this study. Based on the defined critical plane, a multiaxial fatigue damage model combined with Miner's linear cumulative damage law is used to predict fatigue life. The experimentally obtained fatigue data for 7050‐T7451 aluminium alloy notched shaft specimens under constant and variable amplitude multiaxial loadings are used to verify the proposed methodology and equivalent strain‐based methodology. The results show that the proposed methodology is superior to equivalent strain‐based methodology.

A B S T R A C T A healing method for fatigue damage was studied by laser shock peening (LSP) with excimer laser for polycrystalline copper film. It is found that work hardening due to LSP could be responsible for the improvement of residual fatigue lives for the damaged and undamaged specimens by LSP, and the hardening degree for the damaged specimen by LSP is obviously higher than that for the undamaged specimen by LSP. In this paper, two basic mechanisms were identified. One is the dissipated energy enhancement mechanism, which improves the fatigue life caused by laser shock stress, and the other is the healing mechanism, which leads to a further improvement. Based on the two mechanisms, a residual fatigue life prediction method is proposed by the view of energy consumption before and after LSP. The predicted lives by the proposed method agree well with the experimental results.Keywords laser shock peening; work hardening; dissipated energy enhancement mechanism; healing mechanism; life prediction.coefficient for the original specimen by LSP k D ¼ hardening coefficient for the damaged specimen by LSP m ¼ modified exponent of hardening degree N 0 ¼ fatigue life for original specimen N D ¼ consumed life of the damaged specimen N DEEM ¼ improved fatigue life caused by the extra plastic strain energy for the original specimen by LSP N D DEEM ¼ improved fatigue life caused by the extra plastic strain energy for the damaged specimen by LSP N LSP D¼0 ¼ fatigue life for the original specimen by LSP N HM ¼ pure healing life caused by HM N r ¼ residual life of the damaged specimen by LSP n′ ¼ cyclic hardening exponent of the material ΔW p0 ¼ plastic strain energy for the original specimen without LSP ΔW LSP;D p ¼ plastic strain energy for the damaged specimen with LSP ΔW LSP;D¼0 p ¼ plastic strain energy for the original specimen with LSP Δσ ¼ stress range Δε p ¼ plastic strain range Δε p0 ¼ plastic strain range of specimen without LSP Δε LSP p ¼ plastic strain range of specimen with LSP Δε LSP;D¼0 p ¼ plastic strain range of the original specimen with LSP Δε LSP;D p ¼ plastic strain range for the damaged specimen by LSP