Predicting Fatigue Crack Initiation Lives Of Plate-Like Compenents By Using Damage Mechanics

Fatigue failure of metal component is an important factor relating to mechanical equipment and engineering structural use safety and cost economy in many engineerings. And the application of damage mechanics in fatigue analysis is becoming an important research direction owing to the urgency of engineering requirements and the complexity of fatigue problems.The fatigue failure process consists of two stages:fatigue crack initiation and crack propagation. It has certain difficulty in the use of traditional analysis method in analyzing crack initiation. Second, crack propagation, in which stage fracture mechanics method is mostly adopted at present. Comparatively speaking, the analysis of crack propagation stage is more mature and reasonable than that of crack initiation stage, therefore, the study on problem of crack initiation lives has certain significance.This paper mainly studies the establishment of energy principle and coupled system of fatigue crack initiation problem of plate-like component with large range damage conditions, then the closed form solution of prediction to crack initiation lives of plate-like components is derived based on the above achievements, and finally, a new system on the analysis to crack initiation lives of plate-like components is obtained.Applying virtual work principle, the closed form solution is obtained for evaluating crack initiation lives of a plate-like component under plane stress. Applying variational principles, fatigue crack initiation lives is evaluated for a plate-like component with large range damage. Coupled system is defined firstly, then zero different work principle, coupled potential energy principle and coupled complementary energy principle are established. Applying coupled potential energy principle, the closed form solution is obtained for evaluating crack initiation lives of a plate-like component under plane stress. As an application, fatigue crack initiation lives of the plate-like components is evaluated, the method is given for evaluating its fatigue crack initiation lives. Compared with the experimental data to predict the results more desirable, the use of this method predicts fatigue crack initiation lives of plate-like component with large range damage is feasible,and predicts fatigue crack initiation lives of different geometric shapes of plate-like components.