Failure Analysis of Cold Forging Dies Using FEA

The FEA package DEFORM enabled an entire cold forging process to be simulated, while simultaneously predicting all the necessary stress strain states in both die and workpiece. The cold forging process analyzed was the method used to "trim" a hexagonal shape on the head of a fastener. DEFORM utilizes a fracture criteria, which deletes elements once they have exceeded a specified damage value. This criterion was used to predict fracture within the workpiece. The relationship between the die geometry and its final stopping distance, the consequent induced stresses and the energy required to shear off this excess material was investigated. Authors: Conor MacCormack, John Monaghan, Trinity College, Dublin, Ireland.