Research On Springback Control And Surface Compensation Of Stamping Of Aluminum Alloy Engine Hood Outer Panel

Application of aluminum alloy on the autobody can effectively reduce the weight of the autobody,improve fuel economy and cruising range.However,aluminum alloy has poor ductility at room temperature,and the springback phenomenon caused by the elastic recovery and uneven stress distribution of the sheet after stamping is more serious than that of low-carbon steel.Compared with cracking and wrinkling,springback of stamping is more difficult to control and is an important issue in practical production and academic research.Springback of stamping has a great influence on the subsequent body assembly and the appearance quality of the vehicle,and it is also one of the major concerns in the field of vehicle body manufacturing.This paper takes the aluminum alloy engine cover outer panel as the research object,and focuses on mold design,forming process and profile compensation to study the influence law of various factors on the springback after forming and solve measures,mainly carry out the following works:(1)The effects of the shape of the drawing die on the stamping springback of the aluminum alloy engine cover outer panel are studied,and the shape of the die that minimizes the springback after trimming is determined.According to the mold design criteria and combined with the aluminum alloy forming characteristics,the stamping direction,press surface distance,concave/convex fillet radius and draft angle 4 mold shape design variables and their scope are determined,the maximum springback amount after trimming of the aluminum alloy engine cover outer panel is used as the evaluation index,and the orthogonal test design is performed.The range analysis and analysis of variance of the test results are carried out to obtain the contribution ratio,significance and influencing laws of each shape parameter of mold about the springback after trimming,the optimal mold solution that minimizes the maximum springback after trimming is predicted and is verified.Then,by analyzing the drawing forming results of the optimal mold scheme,the curvature radius of the rear end of the mold is further increased,so that the formability of the drawing process is better,leaving enough room for subsequent process parameter optimization.(2)The effects of drawing process parameters on the stamping springback of the aluminum alloy engine cover outer panel are studied,and the process parameters that minimize the springback after trimming are determined.Based on the optimal die design,the forming limit diagram and thickness distribution diagram for the trial forming with integral drawbeads are analyzed to segment the drawbeads.The thinning distribution of each part is targeted as evenly as possible.Cracking,wrinkling and lack of forming are the constraints,the orthogonality test design and its analysis are carried out to study the relationship between the resistances of various drawbeads so that the relationship between the resistances of the drawbeads is determined.Then the range of variation of sheet thickness,friction coefficient,mold clearance,drawbead coefficient,virtual stamping speed and blank holder force are determined.Adopting the maximum springback amount after trimming as the evaluation index and orthogonal test design is carried out to analyze the influence of various forming process parameters on the stamping springback of the aluminum alloy engine cover outer panel,the optimal combination of process parameters are obtained to minimize the springback without any cracking,risk of cracking,wrinkling or lack of forming.(3)The effect of compensation factor on the surface compensation effect of stamping springback of the aluminum alloy engine cover outer panel is studied,and the compensation scheme that makes the final part deviation meetting the tolerance is determined.Based on the optimal mold shape and the optimal forming process parameter,a non-linear inverse compensation method is used to compensate the stamping springback of the aluminum alloy engine cover outer panel.The effect of compensation factor on the compensation effect is studied,and the optimal compensation program is determined so that the deviation of the part shape after springback and the designed part shape meets the tolerance requirement.