Notched Component Fatigue Life Prediction in Torsional Loading

Considering the situation that fatigue life prediction of notched component is an indispensable part in the process of design in engineering,it is necessary to find some ways to solve such problems effectively.The stress and strain state of notched specimen is more complex,compared with smooth specimen.As a result,some researchers take advantage of the finite element method to analyze the mechanical properties of these kind of specimens,they can get the stress and strain state at the dangerous point directly instead of using theoretical methods.At the same time,the equation of shear stress is fitted by analyzing stress distribution of the section of notch root.The integral of shear stress in the section is equal to the external load,and the true stress value of notch root is derived.Then,the fatigue damage evolution equation of notched specimens under torsional load is proposed based on the closed-form solution in this paper.Meanwhile,the nonlinear fatigue life prediction model of notched specimens under the torsional load is given by using the damage mechanics theory.The proposed model is validated by experimental data(30CrMnSiNi2A steel and 45#steel).The results show that the predicted life is not only close to the experimental results,but also tends to be safe.The fatigue life of notched specimen is predicted by using notch geometric parameters and material constants.The model has more concise calculation process,avoids complicated fatigue tests,and facilitates engineering application.