Study On The Deformation Characteristics Of Thick Inver 36 Alloy Sheet And Development Of Die Surface Partitioning Software

Because of its low expansion,Invar 36 alloy is extensively applied in many areas and plays an irreplaceable role,such as precision instruments,aerospace,precision die,especially in the application of the large size composite parts die.However,because of its specificity in mechanical properties and physical properties,and the lack of research on deformation characteristics in elevated temperature and bending springback,the application of the Invar 36 alloy has been greatly limited.Besides,the partitioning preform is deemed as the key technology in manufacturing of large size Invar 36 alloy die,and there are still some technical difficulties.In this thesis,under the support of lateral university-enterprise cooperation projects with Shanghai aircraft manufacturing co.,Ltd,the deformation characteristics at elevated temperatures and the springback bahavior of Invar 36 alloy were studied systematically,and based on CATIA secondary development,the software for die surface partitioning was developed.Tensile experiment was used to study the influence of temperature and strain rate on mechanical properties of Invar36.The microstructure variations were also studied through OM,XRD.The experiment results show that Invar 36 alloy is an isotropic material,and maintains single-phase of austenite in the temperature range from ambient to 900?.The strength decreases with the increasing of temperature while the elongation first increases and then reduces.The peak value appears at 600?,and at higher temperature the flow stress shows a high strain rate sensitivity.Three-point bending tests were used to study the minimum bending radius and the influence of sheet thickness and forming temperature on bending springback behavior of Invar 36 alloy.The results shows the springback decreases with the increase of sheet thickness and forming temperature.The forming temperature has a prominent effect on inhibiting springback.When forming temperature is elevated from ambient to 800?,the springback value decreased by 87%.Based on Mises yield criterion and isotropic hardening model,the springback behavior of Invar 36 alloy was simulated by Ls-Dyna,which shows a high conformity with the experiment results.This finite element model can effectively predict the springback of thick Invar 36 alloy sheet.Based on CATIA advanced development,a human-computer interaction software were developed in view of the die surface partition preform process.The software takes die surface characteristics,material properties,press parameters and welding technology into account.Necessary steps of partition preforming are integrated into the software,which can help programmers save design time,improve design efficiency greatly,and provide a support for Invar alloy mold manufacturing.