Thermo-mechanical Coupled FEM Simulation Analysis Of Magnesium Alloystrip

Magnesium alloy strips and sheets are being widely used in aviation,aerospace,automotive industry,3C and many other fields. the research on making-technology of which has been the focus in whole word. Generally the alloy strips and sheets are produced by rolling method. If we could accurately calculate and match every technics parameter in the rolling process the deforming efficiency and quality of the sheets will be greatly improved. The strip hot rolling process is a complex problem that many variables interact each other, and also a nonlinear analysis which includes material nonlinear analysis, geometrical nonlinear Analysis,contactile nonlinear analysis and the like, both of them bring great hardship to the research. In recent years, with extensive application of simulation software and the increasing maturity of calculation technology,the thermo-mechanical coupled method has been introduced into software program to apply it to analyse the problem of sheet hot rolling .In magnesium alloy strip hot rolling process, it is important to accurately calculate Distribution of temperature field and stress field in strip for designing rolling technology parameters. In fact, during the process temperature field and Stress field influence each other. In order to study and analysis this process, elastic-plastic finite element model was developed based on experiment equipment technology by MSC. Marc software. All process of magnesium alloy AZ31 sheet hot rolling are simulated by choosing the advanced thermo-mechanical coupled method. The simulated result detailed analysis was made too. The main contents are as following:1. Based on the basic principle of nonlinear finite element method, comprehensively considering the Similarity of stress and strain distribution in large deformation of rolling piece process, finite element equations that is used to describe the position of large deformable body position in reference system, was established. Finding out that Updated Lagrangian description of equation is more general than Total Lagrangian description, Therefore, the updated Lagrangian description method is used for this set of model parameters2. Based on heat transfer equation and theories of elastic-plastic large deformation, considering mechanical equilibrium equations and energy balance equation, a thermo-mechanical coupled mathematics model was established. Obtained at beginning of each time step, obtain the current displacement increment amendments domain V and boundary S, and the Solution Principles between the incremental steps within Force balance and Energy balance. Comprehensive comparison of several methods for solving was made, proved the Newton-Raphson to be best, and a method best convergence criterion chosen to check convergence of the displacement.3. According to constitutive equation of magnesium alloy AZ31 at high temperature, relying on interface program provided by Marc, using FORTRAN language to compile subroutine of the flow stress, for secondary development to the software. Magnesium alloy AZ31 of material models with change law of high-temperature flow stress is obtained.4. The rolling force and torque in rolling process was simulated. Compared with the experiment results the simulation was almost the same as the experiment results, and verified its accuracy. Also found that two-dimensional model simulation results was more accurate than calculation of three-dimensional simulation results ,and it saved a lot of computing time and computing resources.5. Based on 3-D and 2-D model, temperature field, temperature gradient, equivalent plastic strain, equivalent plastic strain rate and equivalent plastic stress field in rolling process were simulated. The distribution law of these parameters along the thickness and width, on the surface and in the core, was systematically and Comprehensively analysed. Overall temperature gradient near contact surface area is larger, but away from the area the result is smaller. deformation rate distribution at rolling region is consistent with the theoretical equations. Equivalent plastic stress distribution law along the thickness direction in according to rolling theory; along the width direction, the stress is smaller and more uniform distribution at center, the stress situation at edge is more complicated. Along the thickness direction, from surface to center the equivalent plastic strain is decreasing gradually; along the width direction, from center to edge strain increasing.6. The effect of different technological parameters on rolling force, temperature field and Spread was studied. the Similarity of rolling force, temperature field and spread under different operating conditions was summarized. The result indicate that initial temperature and reduction rate have obvious influence on rolling force. As the reduction rate largen, the rolling fore is increasing. At high temperature rolling times, different rolling speed corresponds to a deformation resistance, following rolling speed increasing, the rolling force is becoming bigger, at the same time deformation resistance of material is harder. With friction coefficient increasing rolling force is becoming bigger, but the range is small. To spread, following reduction rate increasing, the spread is increasing. When B1= L, B2=.L, and between [B1,B2] interval, with plate width increasing the spread is becoming bigger. Under other conditions remain unchanged, with roller radius the spread also becomes big, and there is similar law between the spread and friction coefficient.