An Innovative Approach to Sheet Metal Forming Simulation for Higher Accuracy, Using 3D Solid Elements in Simufact.forming

The most common issues in sheet metal stamping are progression design, transfer design, thickness control, wrinkling, thinning, tearing, spring-back and die-wear. An innovative methodology has been developed to analyze these aspects using a non-linear finite element approach with 3D Solid elements instead of the more traditional Shell elements. This leads to the most accurate result, and allows a fully transparent implementation in the metal forming simulation package Simufact.forming. The method takes 3D STL-data or CAD data as input, and fully automatically creates a 3D Solid mesh that is optimized for sheet metal forming, using a ‘21⁄2 D sheet mesher’. During the simulation, the mesh is constantly updated to enable tracking of the large deformations. Parallel processing further reduces the CPU times. INTRODUCTION For many years, the implicit Finite Element method using 3D Solid Elements has been successfully applied to many bulk forming processes, in particular cold heading and hot forging. An example for each is given in figure 1 and 2. A recent development in meshing technology extends the applicability of this method to sheet metal forming. A typical example is shown in Figure 3. Figure 1: Bulk Forming Example – Cold Heading Figure 2: Bulk Forming Example – Hot Forging Figure 3: Sheet Metal Forming In this paper we will summarize the typical modeling steps for a Sheet Metal forming simulation. These steps are demonstrated by means of a relatively simple example. After this, more complex simulation results will be given. MULTI-STATION PROCESS DEFINITION A simulation session always starts with the selection of the type of metal forming process to be modeled. A special dialog guides the user with this choice. Based on the choice, a tree structure will be created with placeholders for the dies, work-piece and all process parameters. A progression design to be evaluated is always defined by a sequence of 3D die models, created in a 3D CAD system. The die models of each station are imported directly from the CAD files, and organized in a tree structure, as shown in figure 4. Each station has its own collapsible tree-structure with place holders for the dies and other process parameters. Figure 4: Typical Tree Structure for Multi-Station Process PRESS A press can be defined manually by assigning characteristic parameters. For instance, a Hydraulic press definition is shown in figure 5. Figure 5: Hydraulic Press Definition The Hydraulic Press is drag/dropped into the process tree, and the appropriate die assigned to it, as shown in Figure 4. SPRINGS Often, one or more dies are supported by springs, which can be either released or pre-loaded. The spring is defined as shown in Figure 5. Figure 5: Spring Definition The spring is then drag/dropped on the appropriate die in the process tree, as shown in Figure 4.