On the formability limits of thin-walled tube inversion using different die fillet radii. (November 2019)

• Record Type: Journal Article
• Authors: Magrinho, J.P.; Centeno, G.; Silva, M.B.; Vallellano, C.; Martins, P.A.F.
• Is Part Of: Thin-walled structures. Volume 144(2019)
• Publication Date: 2019-11
• Subjects: Thin-walled tubes -- External inversion -- Formability limits -- Experimentation -- Finite element method; Thin-walled structures -- Periodicals; 690.1
• DOI: 10.1016/j.tws.2019.106328
• Languages: English
• ISSNs: 0263-8231

Abstract

Abstract: This paper is focused on the external thin-walled tube inversion using different die fillet radii and is aimed at analysing its formability limits by local buckling, necking and fracture in principal strain space. The investigation draws from a methodology that was recently developed by the authors for general tube forming and focuses on the specificities that characterize its application to the deformation conditions of external tube inversion. Strain loading paths and formability limits at the onset of buckling, necking and fracture are determined by combination of experimental strain analysis with digital image correlation (DIC), thickness measurements, force-displacement evolutions and finite element modelling. Results show the paramount importance of the curling radius on the formability limits of external tube inversion. This information is relevant for designing energy absorbers based on external tube inversion and the novelty of the paper stems from the use of experimental techniques commonly employed in metal forming to the analysis of formability and failure in typical deformation modes of energy absorbers. Highlights: Methodology to determine the formability limits by buckling, necking and fracture in external thin-walled tube inversion. Utilization of principal strain space to plot the strains from digital image correlation and wall thickness measurements. Combined analysis of strain and force-displacement evolutions to determine the onset of necking. Discussion on the flexibility of changing the curling radius to design customized energy absorbers.