Papers by Author: Quan Lin Jin

Abstract: A hybrid global optimization method combining the Real-coded genetic algorithm and some classical local optimization methods is constructed and applied to develop a special program for parameter identification. Finally, the parameter identification for both 26Cr2Ni4MoV steel and AZ31D magnesium alloy is carried out by using the program. A comparison of deformation test and numerical simulation shows that the parameter identification and the obtained two sets of material parameters are all available.

Abstract: The microstructure evolution and mechanical properties of magnesium alloy AZ31D processed by equal channel angular extrusion(ECAE) are studied. The processing temperature and the passes of extrusion are important factors to affect the microstructure and mechanical properties of the magnesium alloy during ECAE. In this paper, ECAE was performed at the temperature from 523 to 673K. The ductility increased through the grain refinement after the ECAE because the recrystallization took place and high angle grain boundary formed. The elongation of magnesium alloys AZ31D was improved after the ECAE. The maximum elongation-to-failure of magnesium alloys AZ31D processed by ECAE for 4 passes at 573K and strain rate of 0.5 10−4 s−1 × was 350%.

Abstract: A numerical simulation of superplastic backward extrusion of a magnesium alloy part is presented in this paper. In fact, the simulated superplastic forming is not a pure superplastic forming because of the billet with coarse cylindrical grains. The forming may become a pure superplastic forming only after dynamic recrystallization and grain refinement appear and the grain boundary sliding has been the main deformation mechanism. In order to simulate the special forming process, a constitutive relation considering dynamic recrystallization and the multiform deform mechanism and the parameter identification of the constitutive relattion are studied. The program for simulation is able to predict the grain refinement and the transform between different deformation mechanisms. Finally the calculated results on the grain size and dynamic rerystallization are presented. A comparison between the calculated and the experimental results shows there is a good agreement between calculated results and experimental results.

Abstract: Dynamic recrystallization, on which grain size of the final forging depends mainly, is one of the most important microstructure evolution processes in moderate-to-low stacking fault energy metals. In this paper, the process of dynamic recrystallization is simulated by numerical method. The paper first gives a visco-plastic model considering dynamic recrystallization in detail; secondly gives the applied finite element formulation and compiles an finite element program in Visual Fortran 6.5 based on the updated Lagrangian formulation rigid-plastic finite element; thirdly the material parameters are identified through inverse analysis, based on the compiled finite element program and the developed global optimization method; at last, the compiled finite element program is applied to simulate the microstructure evolution caused by dynamic recrystallization, the calculated result agrees with the experimental result relatively well.

Abstract: An experimental study on superplastic forming behaviors and microstructure characters of commercial magnesium alloy sheet AZ31B is presented in this paper. The main experimental results show that the commercial magnesium alloy AZ31B sheet has superplastic capability. For the received sheet without any pre-processing, the maximum elongation is 295%. The dynamic recrystallization and grain refinement can be found, In the case of temperature <350°C, and the grain growth appears if temperature ≥ 350°C. The superplastic behaviors can be improved by controlling the dynamic recrystallization and grain refinement. Some experimental results of free superplastic bulging are presented in this paper. The results show that influence of temperature on forming capability is much less than the influences of temperature on elongation. In addition, the maximum principle strain

Abstract: An experimental study on superplastic forming of a front fender of 5182 aluminum alloy is presented in this paper. Based on the shape characters of the front fender and the material experimental results, dies, heater and temperature controller for superplastic forming of the fender are designed and manufactured. The SPF results show the designed processing and dies are reasonable and feasible.