Dynamic Characteristics Research On The Valve Of Electromagnetic Impactor

Electromagnetic impactor is a kind of impact machines which impact force is produced by the electromagnetic force. And it can be used to rebuild old cities, demolish concrete, construct roadbed, taking slag down and so on. The impact process of impact machines is accomplished in a very short time, which can produce tremendous impact force, and the process is very complex which will be with big deformation and big torsion, even with plastic deformation. In engineering project, the valve of electromagnetic impactor is destroyed easily, so the analysis and research of the stress and strain of the valve becomes very important in both theoretical and realistic engineering fields in impact process.In this thesis, the author develops the research on the question of the valve impact of electromagnetic impactor in the following fields:Firstly, the basic theory of impact dynamics and finite element are summarized systematically, and the general analysis way and solve process of the impact dynamic are carried out, which will be the theoretical base for numerical simulation. The non-linear finite methods, Lagrange, is introduced, the basic equation of impact dynamics are summed up and the basic algorithm of contact impact is summarized; then the resolved of the valve impact is received basic equation of impact dynamics with finite element methods.The impact system of electromagnetic impactor is considered as the research subject, and its finite element model is established.Secondly, putting the valve of electromagnetic impactor as a research object, and testing the acceleration of the valve and having the finite element simulation to the acceleration of the valve. Then comparing the two results and finding out difference of the two results, and the results indicated that the error of the result of testing and the result of finite element simulation are relatively smaller, and the error is within the accredited range. This shows that the simulation of the impact system of the electromagnetic impactor using LS-DYNA soft is reasonable; At the same time, It is proved that using finite element simulation to solve impact problems is feasible.Finally, the author do research for the valve of the electromagnetic impactor in three typical working project, and analysis the strength and energy transfer to the valve of the electromagnetic impactor when the valve impacts the elasticity body, the rigid body and the elasticity rod, and get the stress ruler of the valve. the stress value of the center of the valve is higher than fringe, the end of the valve have high press stress value, but the draw stress value of the end of the vale is low; The middle part of valve not only have high press stress value but also high draw stress value, so the impact face fatigue damage of the valve and fatigue fracture of the valve will be come out. Those analyses will have helps to improve the quality of the valve and design the valve of the electromagnetic impactor. Lastly, taking the elasticity rod impacted as an example, the ruler of energy transfer efficiency of the valve is analysed, and finding that when the stiffness of the work increase, the energy transfer efficiency of the valve will be drop.