Stress analysis and optimization of combined die structure with two stress rings were performed.Using thermoelastic deformation,the contact pressure at the interfaces between layers was calculated.Then,theoretical exp...Stress analysis and optimization of combined die structure with two stress rings were performed.Using thermoelastic deformation,the contact pressure at the interfaces between layers was calculated.Then,theoretical expressions of stress distribution for the combined die were derived.The thermal-mechanical effect under working conditions was considered.To verify the theoretical expressions,simulation work was performed.Optimization of die design was carried out by defining radius ratio and shrink fit coefficient as optimization variables.The objective was to minimize the effective circumferential stress at the inner surface of the die insert,under the constraint that the maximum equivalent stress values of die insert and stress rings did not exceed their respective yield stresses.The Kriging model was used to describe the influence of shrink fit and die dimensions on the objective function and the maximum equivalent stress.Using a genetic algorithm,optimum parameters were found with a minimum circumferential stress of 442.9 MPa under a working stress of 1800 MPa.Further analysis of five selected optimal results was carried out,and the specific design parameters of these combined dies are different under the same level of circumferential stress,and the combined die is overdesigned if the thermal effect is ignored.展开更多
In order to study the influence of die combination on continuous variable cross-section direct extrusion (CVCDE) in the extrusion process, the accumulative strain formula is derived, and it can be known that the ext...In order to study the influence of die combination on continuous variable cross-section direct extrusion (CVCDE) in the extrusion process, the accumulative strain formula is derived, and it can be known that the extrusion ratio of various stages directly determines the size of corresponding stage strain by formula. In this paper, as an example of the two interim dies, three die combinations of different angles and extrusion ratio are designed. Aviation magnesium alloy ZM6 is studied, and the results show that dynamic recrystallization is even more complete when continuous shear deformation occurs, so that the refinement and homogenization of microstructure are obtained. By the use of different die combinations, the accumulative strain increases under the conditions of same total extrusion ratio. Thus, the refined crystalline strengthening effect of extrusion deformation can be further analyzed. Due to the dead-zone defects, the actual accumulative strain decreases significantly and the effect of microstructure and performance improvements also decreases with it. Therefore, the optimal design of die combination is the key to the process and product of CVCDE, which provides a scientific basis for the development of severe plastic deformation.展开更多
基金the National Natural Science Foundation of China(No.51475294)。
文摘Stress analysis and optimization of combined die structure with two stress rings were performed.Using thermoelastic deformation,the contact pressure at the interfaces between layers was calculated.Then,theoretical expressions of stress distribution for the combined die were derived.The thermal-mechanical effect under working conditions was considered.To verify the theoretical expressions,simulation work was performed.Optimization of die design was carried out by defining radius ratio and shrink fit coefficient as optimization variables.The objective was to minimize the effective circumferential stress at the inner surface of the die insert,under the constraint that the maximum equivalent stress values of die insert and stress rings did not exceed their respective yield stresses.The Kriging model was used to describe the influence of shrink fit and die dimensions on the objective function and the maximum equivalent stress.Using a genetic algorithm,optimum parameters were found with a minimum circumferential stress of 442.9 MPa under a working stress of 1800 MPa.Further analysis of five selected optimal results was carried out,and the specific design parameters of these combined dies are different under the same level of circumferential stress,and the combined die is overdesigned if the thermal effect is ignored.
基金financially supported by the National Natural Science Foundation of China(No.51205094)
文摘In order to study the influence of die combination on continuous variable cross-section direct extrusion (CVCDE) in the extrusion process, the accumulative strain formula is derived, and it can be known that the extrusion ratio of various stages directly determines the size of corresponding stage strain by formula. In this paper, as an example of the two interim dies, three die combinations of different angles and extrusion ratio are designed. Aviation magnesium alloy ZM6 is studied, and the results show that dynamic recrystallization is even more complete when continuous shear deformation occurs, so that the refinement and homogenization of microstructure are obtained. By the use of different die combinations, the accumulative strain increases under the conditions of same total extrusion ratio. Thus, the refined crystalline strengthening effect of extrusion deformation can be further analyzed. Due to the dead-zone defects, the actual accumulative strain decreases significantly and the effect of microstructure and performance improvements also decreases with it. Therefore, the optimal design of die combination is the key to the process and product of CVCDE, which provides a scientific basis for the development of severe plastic deformation.