Formability Limits in Square Tubes and L-Section Profiles

Understanding the formability limits of thin-walled tubes with square cross-sections and L-section profiles is crucial for improving manufacturing efficiency and ensuring structural reliability in industries such as automotive and aerospace. Unlike the usually studied circular tubes, square tubes and L-section profiles geometries present unique deformation and fracture behaviours that require specific analysis. To address this gap, this research establishes a novel methodology combining digital image correlation (DIC) with a time-dependent approach and precise thickness measurements, enabling accurate strain measurements essential to the onset of necking and fracture strain identification. Two experimental tests under different forming conditions allowed capturing a distinct range of strain paths leading to failure. This approach allowed the determination of the forming limit points associated with necking and the fracture forming lines associated with crack opening by tension (mode I) and by in-plane shear (mode II). The findings highlight the strong influence of geometry on the fracture mechanisms and provide valuable data for optimizing tube-forming processes for square tubes and L-section profiles, ultimately enhancing the design and performance of lightweight structural components.