Formability limits by fracture in square tubes and L-section profiles

IDMEC, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal

^* Corresponding author: ines.matias.almeida@tecnico.ulisboa.pt

Abstract

This paper presents an innovative methodology to determine the formability limits of thin-walled tubes with square cross-sections and L-section profiles. These geometries are studied for the first time in this context, providing a pioneering insight into their fracture behaviour. The methodology considered utilizes digital image correlation (DIC) and thickness measurements at the crack location and enables the extraction of strain loading paths and the determination of fracture limit strains. Several experimental formability tests were conducted under various forming conditions, capturing a wide range of strain paths leading to fracture. This allowed the experimental determination of the fracture forming line (FFL) and inplane shear fracture forming line (SFFL) for these geometries, and its representation in principal strain space. The results highlight the critical importance of geometry-specific fracture characterization for the optimization of industrial tube-forming processes. By providing a comprehensive understanding of formability limits in these novel geometries, this study offers a valuable tool for researchers and engineers aiming to enhance the reliability and efficiency of forming processes in automotive, aerospace, and other applications.