The Research And Application Of The Grid Local Refinement Method In The Sheet Metal Forming Numerical Simulation

The spring-back is the most difficult problems in sheet metal stamping defects,using the finite element numerical simulation techniques to predict and control the rebound is an effective way.In order to solve the problem of accuracy and efficiency, the way of local refinement of the initial sheet is feasible, but there is a problem to adapt the way of local refinement, as it’s difficult to obtain the refinement of the region and,to ensure the quality of the grid divided in a different scheme which is meeting the requirements of the spring-back accuracy.This paper presents a method based on the grid mapping method to achieve the local refinement grid, through the comparative analysis of different meshing program, as well as the validation studies of the experimental data, shows that the effectiveness of the method.On this basis,studies the spring-back compensation under the process control, it’s further proving the superiority of the method in engineering applications.The research of local refinement grid method based on grid mapping method,the main tasks include the following three aspects:Firstly,according to the guidelines of the mold radius of curvature, studies the formation process of local refinement areas in the parts of the fillet region and flowing through the mold curvature larger parts of the region.Proposes the identification method of regional boundaries of local refinement which is using the projection line of the contour of the workpiece features expand the line in the plane and the mold parting line on the flat blanks from the perspective of engineering applications.Secondly,in order to quickly obtain the boundary line of the local refinement region,proposes grid mapping method based on one-step, that projects the discrete point of the desired contour of the workpiece features onto the grid model of the simulation results,and then uses mapping relationship between the unit and node to calculate the coordinates of the projection point on the blank grid model, by curve fitting, gets the characteristic contour of the workpiece on the flat blanks which is the boundary line of the refinement region.Thirdly,for certain parts spring-back characteristics,analyzes the principle and law of the grid size affecting the spring-back,designs meshing program,proposes the strategy of mesh refinement in the direction of the spring-back cross-section,the results shows that it’s more advantages in accuracy and efficiency.For the uncertainty of the spring-back prediction accuracy in the spring-back control process, proposes the spring-back compensation method based on the method of technology control,which is on the basis of grid local refinement,that analyses the law of the control of technology parameters on the spring-back,calculates the compensation benchmark surface,in the follow-up control,by changing the technology parameters within the constraints to achieve precise control of the spring-back,adapts Design of Experimental,Response surface model,and Genetic Algorithms optimization strategies to determine the optimal solution of the standard compensate surface.