2.2 Prediction of Trimmed Edge Stretching Performance Objectives Understand the mechanism of edge stretching failure Develop and establish a methodology to predict the trimmed edge performance To determine and validate the edge stretching limit (ESL) To identify the factors affecting the edge stretching limit Technical Benefits Provide a tool to predict edge cracking in forming feasibility studies, to assess the effectiveness of the counter-measures used to avoid edge cracking and to assess the edge forming severity in the field. The ESL can also be used to measure the effectiveness in various shearing/trimming processes, optimal shearing/trimming tools setup, material microstructural optimizations, etc. UNH - 28 October 2016 Sheet Metal Forming

2.2 Prediction of Trimmed Edge Stretching Performance Technical Obstacles: High edge stretching limit requirement Beyond material capability Poor design UNH - 28 October 2016 Sheet Metal Forming

2.2 Prediction of Trimmed Edge Stretching Performance Technical Obstacles: Poor edges Worn tools Wrong die clearance Continuity of geometry change Sharp corners UNH - 28 October 2016 Sheet Metal Forming

2.2 Prediction of Trimmed Edge Stretching Performance Edge Cracking Mechanism Edge stretching performance affected by both base material and blanking or trimming processes and their setups Damages introduced during blanking or trimming cause the edge failure below the forming limit No consistent correlation has been found between edge shear face properties (roll over, burnish, fracture , burr) and the ESL Severity of edge damage has been found to correlate with strain hardening in the shear affected zone UNH - 28 October 2016 Sheet Metal Forming

2.2 Prediction of Trimmed Edge Stretching Performance Implementations and Discussions Edge Stretching Limit Test Method? Factors affecting the ESL: Material Side? Tool and Process Side? How to improve the ESL? Edge Damage Characterization and Index? UNH - 28 October 2016 Sheet Metal Forming