Prediction and assessment of skid line formation during deep drawing of sheet metal components by using FEM simulation

Abstract

The subjective perception of the quality of sheet metal components mainly depends on geometric characteristics and surface structure. Additionally, particular attention must be paid in this context to avoiding surface defects such as skid lines during the sheet metal forming process. For this reason, current research activities focus on predicting such surface defects as precisely as possible in the early development stages of sheet metal components by using FEM simulation. However, the modelling approaches available today do not yet provide an adequate basis for such a numerical prediction regarding the appearance of surface defects of sheet metal components such as car body outer skin panels, especially of skid lines. Consequently, the research work reported about in this paper concentrates on the development of an empirical methodology for predicting and quantifying the formation of skid lines during deep-drawing processes by using FEM simulation. For this purpose, an experimental tool was developed to produce different skid line formations by using various process parameters and thus to investigate process-influencing factors on the example of the steel sheet material DC06. In principle, the investigations carried out showed that the punch radius and the blank holder force indeed do represent crucial influencing factors for the formation of skid lines. Finally, the results obtained were used to develop a forming simulation criterion, which allows predicting skid lines formations based on calculated strain state variables such as major strain, thinning and unbending strain.

Experimental Study and Simulation-Based Criterion for Stamping Skid Line

“…The values of r 0 , r 45 , r 90 , r n , and ∆r of the sheet metal can be obtained by using Formulas ( 8)- (10), and the obtained results are shown in the table.…”

“…They proposed the methods to solve skid lines in different stages, such as the modeling design, the stamping process, and die development, which provided a reference for solving skid lines. Cyron et al [10,11] pointed out the inaccuracy of the skid line criteria in commercial software. They used a V-shaped die to conduct experiments on a stamping machine, used an optical strain gauge to measure the dynamic strain on the surface of the test piece, and examined the microscopic topography and roughness of the surface of the test piece after stamping.…”