Dynamic Numerical Simulation And Damage Telerence Design Of Torsion Bar Under Random Load

Design of machine component is commonly depending on experience or static state theory. But it's well known that the component is generally working under dynamical load. And throw great number of practices we can find that most invalidity of components is arose by fatigue. So this thesis will use dynamic FEM (finite element method) to investigate the dynamic response of torsion bar under random dynamic load. Base on the result of simulation the thesis will give the damage tolerance design and the calculation of fatigue life. At later, it will discuss all of result of front.To solve problem of dynamic FEM, it will use the direct integral calculus method of NEWMARK to give the displacement and stress solution vs. time of nodes and elements at the place where fatigue always occurs. It will discuss the choice of element and the found of the simulation model. Then give the simulation of the torsion bar working in one of circumstances.In damage tolerance design of the torsion bar, we gave the method to enumerate remaining intension of the torsion bar. Numerical model of crack's spread based on Paris formula would be given. As example, it would enumerate the torsion bar's checking periods after the two of the three factors of the damage tolerance design been confirmed. A new numerical method would be used to solve the problem of enumerate of surface I type crack's stress intensity factors, then the feasibility of vising Irwin's approximate arithmetic of surface I type crack's in engineering would be discussed.The method base on S-N course would be used to enumerate the fatigue life of the torsion bar. And the relationship between different factors would be discussed. Base on the result of all enumerate the two method would be discussed.