Multiaxial notch fatigue life prediction based on pseudo stress correction and finite element analysis under variable amplitude loading

摘要

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. 1. Fatigue life prediction method is proposed for notched components under multiaxial variable amplitude loading. 2. Pseudo stress correction approach by FE analysis is extended to determine local stress-strain increments. 3. Non-proportionality factor estimation approach is proposed under multiaxial variable amplitude loading. 4. Critical plane damage model is incorporated into the proposed fatigue life prediction method.