Research On Finite Element Simulation Of Four-roll Planetary Rolling Process Of Copper Tubes

A new process for seamless tube production called Seamless Tube Process (STP) comes into our horizon. The key equipment is a four—roll planetary rolling mill, which is also called Kocks Reduction Mill (KRM). The structure and operation principle of four-roll planetary rolling mill is similar to the three-roll planetary rolling mill. Compared four-roll planetary rolling with three-roll planetary rolling, the rolling speed is faster and the deformation of tube is more uniform, higher efficiency and better quality will be gained as a result.Research on four-roll planetary rolling process of copper tube is still in its initial stage. The flow mechanism of the material,the deformation and temperature field of the tube need to be studied. With the aid of the commercial nonlinear finite element software Msc.Marc, a visible numeric simulation and analysis of the four-roll planetary rolling process of TP2 pure copper tube is carried out in this thesis, which provides an effective way to explore the four-roll planetary rolling process of copper tubes.Establishment of a reasonable and effective finite element model of four-roll planetary rolling process of copper tube is the key step of FE simulation. First, Kinematics modelling of the rolling process is performed and the speed of roller is calculated to set reasonable rolling parameters based on a full understanding of the structure and working principle of the four-roll planetary rolling mill. Then through the Gleeble compression test, stresses of TP2 pure copper at different temperatures and strain rates are obtained, which provides an accurate material model for the FE simulation. Reasonable initial condition,boundary conditons and setting of these conditions in the software are given in this thesis. The finite element model of four-roll planetary rolling process of TP2 pure copper tube is established at last through several adjustments and tests of the model parameters.The characteristic of deformation and the material flow mechanism during the rolling process are obtained through the analysis of simulation. The material flows both in the circumferential and axial directions. The deformation rule of the cross-section of the copper tube is: the original shape is a circle, then turns to be a quadrangle and finially a circle again. Compared with the three-roll planetary rolling process, the bending stress of the tube decreases greatly during the four-roll planetary rolling process, reducing the possibility of the generation of cracks. The calculation methods of internal heat resources including the plastic deformation heat and the friction heat and the reasonable heat boundary models are put forward in this thesis. Then a temperature forecast theoretical system of the four-roll planetary rolling process is built. The temperature field is obtained through the analysis of simulation.Influence of process parameters, such as roller rotational speed, coefficient of fiction and roller profile, upon the rolling process is analyzed. Exit speed of tube can be increased by changing the roller profile, increasing roller rotational speed or friction.