The Non-Linear Forming Limit Diagram
Welcome to 2009! It’s a new year so let’s talk about something that might be new to even those who have seen and used simulation many times previously. The Forming Limit Diagram (FLD) is the fundamental tool which is used to judge whether a formed sheet metal part is predicted to fail or pass, when analyzing simulation results. The “standard” FLD assumes a linear strain path, however, strain paths are not always linear in reality.
Non-linear strain paths usually begin occurring in secondary and subsequent forming operations, especially when the material is formed in the reverse or opposite direction. Therefore, if only a linear FLD is considered in a multi stage sheet metal forming simulation, it is possible that a non-linear failure mode may be overlooked. Therefore, non-linear FLD analysis is required in many cases before a sheet metal forming simulation can be given a “pass”. StampingSimulation.com uses AutoForm Incremental and non-linear FLD analysis is an integral part of this software. [Left: Standard Linear FLD. Right: Non-linear FLD showing additional failure mode]