Predictive analysis of wrinkling in shrink flanging using conventional versus incremental forming

Abstract

This work presents an experimental and numerical investigation of shrink flanging using Conventional Press Forming (CPF) and Single Point Incremental Forming (SPIF). Tests were carried out on aluminium AA2024-T3 sheets to identify failure modes, process windows, and formability limits under compressive loading. Finite Element simulations were developed for both processes, focusing on the evolution of in-plane stresses at the flange edge. A stress-based wrinkling criterion is stablished, and a process window is defined as a function of flange geometry. Results show that SPIF enhances formability and delays wrinkling compared to CPF. However, while CPF exhibits earlier wrinkling, certain cases allow wrinkle ironing, improving the final surface quality. A numerical criterion is introduced to detect wrinkling based on strain differences between the inner and outer surfaces of the sheet, enabling consistent identification of the wrinkling onset across geometries. A stress-based analysis reveals that the critical compressive stress required to initiate wrinkling is significantly lower in CPF and strongly dependent on flange length. Conversely, SPIF maintains a nearly constant wrinkling limit. Based on these findings, a process window was developed to support the selection of the most suitable forming strategy.