Paper Title
Validation of a Numerical Prediction Method for Forming Limit Bands of Rolled Steel Sheets With Variability in Material Properties

Abstract
This study validates a numerical prediction method for forming limit strain bands in 1 mm thick cold-rolled steel sheets. The proposed method combines the Marciniak-Kuczynski model with the first-order reliability method, incorporating statistical data on plastic material properties, including the work hardening index (n-value), orientation-dependent yield stress, and Lankford coefficient (r-value). Forming limit bands were numerically predicted for several linear strain paths. To evaluate the accuracy of these predictions, Nakazima stretching tests were performed on multiple specimens fabricated from the same batch of steel sheets to capture the variability in forming limit strain. A comparison between the predicted and experimentally measured forming limit bands demonstrates the reliability of the proposed numerical approach. These findings contribute to improving the precision of forming limit predictions for rolled steel sheets with inherent material property variations, enabling enhanced accuracy in industrial forming processes. Keywords - First-Order Reliability Method, Forming Limit Strain, Material Variability, Sheet Forming, Stretching Test