Parametric study of piercing force and surface quality in elastomer-assisted tube piercing

Piercing metal tubes is essential for creating openings in multi-port industrial fittings. Conventional piercing techniques often struggle to provide satisfactory edge quality, leading to challenges such as needing pre-drilling, limitations to circular shapes, and edge bulging. While fluid-assisted piercing has been explored, it introduces complexities such as sealing difficulties and expensive tooling. This study examines elastomeric-assisted piercing of aluminum tubes using experimental and numerical methods to address these limitations. Using Abaqus, the process was modeled with the Mooney-Rivlin framework to capture the elastomeric tool's incompressible behavior, while the Gurson-Tvergaard-Needleman (GTN) model predicted ductile failure. Experiments involved piercing 12 mm diameter holes in seamless 6061 aluminum alloy tubes (thicknesses: 1 mm, 1.4 mm, and 1.8 mm) with polyurethane tools of 50 and 85 Shore A hardness, covering 8 distinct test conditions (with and without a counter punch). Final piercing forces were observed to range between 28.78 kN and 61.93 kN. The Finite Element model, utilizing the GTN damage criterion, predicted these forces with an average error of less than 5.5%. The investigation focused on how tube thickness, tool hardness, and maximum process force influence outcomes. Findings demonstrate that with appropriate selection of process parameters-such as material type, geometry, tube thickness, and tool hardness-elastomeric piercing is feasible and yields high-quality cut surfaces. This approach demonstrates that elastomeric piercing, when tailored to material and geometric parameters, offers a practical solution for achieving high-quality cuts, circumventing the drawbacks of conventional and fluid-based techniques.