Numerical Simulation Study On Hydraulic Bulging Process Of AZ31B Magnesium Alloy Sheet

AZ31B magnesium alloy has the advantages of stable performance,low density and environmental protection,so it has a broad application prospect.However,it has the problems of poor plasticity at room temperature and easy cracking under high stress state.The products processed by hydraulic bulging technology have high adaptability,low cost and high quality,which provide technical support for improving forming limit of magnesium alloy.In this paper,the process of AZ31B magnesium alloy slab was studied by hydraulic bulging technology with flexible processing characteristics.The main research contents are as follows:(1)Through tensile test,hardness test and Erichsen cupping test,the performance parameters of AZ31B magnesium alloy slab are determined as follows: tensile strength parallel to the rolling direction is 227 Mpa,yield strength is 175 Mpa,hardness is 71.12 HV.(2)Based on AZ31B magnesium alloy,a finite element model for the hydroforming process of aerospace pedal was established.The stress nephogram,strain nephogram and wall thickness nephogram of parts are analyzed,and the variation rules of stress,strain and wall thickness of sheet metal in the process of hydraulic bulging are explored.The results show that with the increase of bulging time,the maximum stress area of the part is gradually transferred from the drawing side and the fillet of the flange area to the top of the part;the blank material transfer gradually diffuses from the die fillet to the side wall,and finally the thinning rate reaches the maximum value of 18%.(3)Through the numerical simulation experiment,the influence of the liquid chamber pressure,blank holder force,blank holder gap and blank shape on the forming quality of aerospace pedal was explored,and the optimal process parameters were obtained.The results show that when the liquid chamber pressure is 15 Mpa,the blank holder force is 130 kN,and the blank holder gap is 1.15 mm,the aerospace pedal with uniform wall thickness and good forming quality can be obtained by using Dynaform blank layout.(4)In order to explore the influence of different blank shapes on the forming quality of aerospace pedal,the numerical simulation of six different blank shapes was carried out,and the boundary variation law of different blank shapes and the material flow velocity in different regions were comprehensively analyzed.The results show that the reason of wrinkling of blank side wall during bulging is that the speed of corner and fillet is lower than that of straight edge.