The Reliability Analysis for Pistons on Fracture Mechanics

The engine can be called the heart of a car and the piston may be considered the most important part of an engine. The piston endures cyclic heat and mechanical loads during work. Heat load was the major factor to cause ablation and heat crack of the piston head, and mechanical load was easy to bring crack at piston pin seat. In this study, mechanical fatigue experiments for one type of piston are performed, and the FEA static and dynamic analysis are carried out by using software ANSYS to obtained the cranny origin position and stress range value of the dangerous part of the piston, respectively. The critical crack length is analyzed based on the fatigue theory; the stress intensity factors (SIF) are computed, and the expression of the shape geometry factor of the piston is obtained according to the least squares method. An estimated formula of the fatigue life is developed by amending the Paris formula on the basis of studying the fatigue behavior of pistons and the fatigue theory The fatigue life of the piston is calculated using these parameters and the Amending Paris formula. Finally, the validity of the estimated formula is verified by the experiments.