Evaluation of fatigue strength on multiaxial notched specimenss considering failure probability

Abstract

Based on the von-Mises criterion, the influence of stress gradient and additional strengthening effects on fatigue life are considered and a fatigue life prediction method suitable for notched specimens is established combining with Weibull distribution. Firstly, the maximum shear strain amplitude is defined as the damage parameter to determine the location of the critical plane, which can reflect the mechanism of crack initiation and propagation. Secondly, the equivalent stress gradient factor on the critical plane is obtained and the stress gradient influence index is introduced to characterize the degree of influence of the stress gradient. Finally, considering the effects of stress gradient and non-proportional additional strengthening, a new fatigue life prediction method is proposed based on the von-Mises criterion and the Weibull distribution, which can be used to obtain the fatigue life of multiaxial notched specimens under different failure probabilities. In order to verify the reliability of the proposed model, the prediction life using the proposed method, the SWT model, FS model and Manson-Coffin equation are compared with the experimental life of five materials (GH4169, TC4, Al7050, EN8, C40), and the compared results show that the accuracy of the proposed method is higher than that of the other three methods under proportional and non-proportional loading. Meanwhile, the P-S-N curves of multiaxial notched specimens with different failure probabilities are given and analysed.