Expert drawbead models for sectional FEM analysis of sheet metal forming processes

Expert drawbead models which embody the drawing characteristics of the drawbead suitable for a finite element analysis of sheet metal forming processes are developed. The mathematical models of basic drawbeads such as circular drawbeads, stepped drawbeads, and squared drawbeads, of which the dimensions and processes are various, are first derived using bending theory and the belt–pulley equation. Next, experiments for finding the drawing characteristics of the drawbeads are performed. Based on the mathematical models, the expert models are then developed employing a linear multiple regression method by which the deviation of the drawing characteristics between the drawing test and the mathematical model is minimized. For the expert models of combined drawbeads such as double-circular drawbeads, double-stepped drawbeads, circular-and-stepped drawbead, etc., those for the basic drawbeads are combined. Finally, to verify the expert models developed, the drawbead restraining force and bead-exit pre-strain calculated by the expert models of the double-circular drawbead and the circular-and-stepped drawbead are compared with those of experiments. The predictions of the expert models agree well with the experimental measurements.