Research On Metal Behavior In Cold Extrusion Forming Of Internal Thread

With the rapid development of science and technology,internal threads are increasingly applied to various kinds of advanced manufacturing production,especially in the aerospace industry.The traditional internal thread processing methods mainly use cutting process,this method will cut metal fiber,and it affects the quality of internally threaded connection.But cold extrusion forming of internal thread is a kind of processing method without chipping.It based on metal plastic flow theory.Compared with cutting process,the tensile strength and anti-fatigue performance of the thread have been highly improved.In this thesis,combined simulation with experiments to intensively research on the flow behavior of metal in extrusion process of internal thread.The research contents of this paper are as follows:(1)The theoretical basis of internal thread cold extrusion forming was introduced.,and analyzed internal thread in the process of extrusion and the force states of metal materials,and also found out the main factors that affect the metal flow.Illustrate the design method of extrusion tap,parameter calculation.(2)The rigid-plastic finite element model of the extrusion tapping is established.Through the definition of material property,load movement way of the extrusion taps,boundary value problem setting,terminate relationship setting and so on.Finite element model which meet the process requirement was established.(3)Using plastic forming software—DEFORM-3D to simulate the extrusion process of internal thread.Through the point of tracking method of tooth to analyze the metal flow behavior form on X,Y,Z direction.Draw the track point coordinate changes before and after the extrusion and tracking the change of displacement and velocity curve.(4)Drawing the line chart about metal maximum displacement,height of tooth shape and tooth curve of saturation with different bottom hole diameter.Then analyzed the influence of the bottom hole diameter on them.(5)With extrusion tapping tests,compared the experiment results with simulation results and analyzed them.The last conclusion is that the metal flow law and the simulation results are basically identical.