The Numerical Simulation Of Mandrel Fatigue Total Life And Crack Growth

Ring rolling is one of the advanced and highly efficient manufacturing technologies which have many characteristics such as low cost, saving forming force, high quality of product, improving productivity, and increasing utilization ratio of energy and material. Generally it is used to produce seamless ring, for example bearing ring, gear ring and so on. The technology of Ring Rolling is employed broadly in many industrial domains. As a mould of Ring rolling, cold ring-rolling mandrel which subjected to alternating load, friction and pressing is prone to fatigue failure; it is also one of the most frequent and commonest inactivation parts in monotype bearing ring and other Ring rolling process. Its occupation ration is about 50%-90% in all inactivation styles. The service life of cold ring-rolling mandrel has a direct influence on the efficiency and the cost of products.On the view of fatigue failure phenomenon of the cold ring-rolling mandrel, S-N curve approach which is based on S-N curves and Miner liner accumulation dandification law and liner elastic fracture mechanics method which is based on Paris crack growth law are studied in the paper separately to solve effectively the problem of computer numerical simulation of cold ring-rolling mandrel of fatigue total life and crack growth.The mechanical analysis of mandrel in the course of cold ring-rolling process has been done and the finite element analysis model of mandrel has been created. The stress distribution and the dangerous points on the surface of mandrel have been obtained with the method of static's analysis in MSC. Nastran/Patran softwares. The states of stress distribution on the surface have been improved in the way of optimum design.Based on the result of finite element analysis above, generally S-N curve of W6Mo5Cr4V2 steel has been created in the way of mandrel total life simulation with the MSC. Fatigue which is the professional software of fatigue.The results of total life and the positions of minimal life in the fore and after of simulation have been compared. The relationships between fatigue total life and various factors such as loading scale coefficient, the way of machining, and the method of surface treatment, performances of material have been analysised. The error and its origin between simulation result and actual situation have been declarated.This paper has researched the estimating techniques of service life in the course of fatigue crack growth based on the elemental theory of liner elastic fracture mechanics. The da/dN curve of W6Mo5Cr4V2 steel, standard crack specimens graph and flexible curve have been created in the way of mandrel crack growth simulation with the MSC.Fatigue which is the professional software of fatigue. Critical dimension of crack growth, stress cycle index in this course, speed rate of growth and the relational curve between the length of crack and cycle index have been obtained. The relational curves between the speed rate of crack growth and the performances of material such as ultimate tensile strength and elastic ration have been studied. At last, two kinds of experimental methods have been given to supervise the fatigue crack on the mandrel surface which has supplied the experimental foundation to research the fatigue crack growth.