In-plane torsion test – Analysis and design of the clamps

The objective of the paper is to analyze the fundamental influence of the tool design on the in-plane torsion test in order to create a common basis for carrying out tests that enable the characterization of comparable material parameters between various test setups. The clamps have a major influence on the process limits wrinkling and slippage of the in-plane torsion test. The size and the surface structure of the clamping on the process limit of slipping and wrinkling is investigated. Results show that a ring-shaped clamping surface can transmit up to 50% more torque at the same clamping force compared to a full-circle clamping surface. Investigations show that torque transmission through plain clamping surfaces is not possible for thin sheets (t = 0.5 to 3.0 mm). In order to enable torque transmission in spite of this, the structuring of the clamping surface is necessary. Therefore, radial serrations are well suited, to ensure a homogenous torque transmission over the circumference. An analytical approach was developed and numerically validated, that can determine the indentation depth, the maximum transmittable torque and the necessary clamping force for radial serrations. The geometrical and material specific influence on the process boundary of wrinkling was analyzed and a material independent recommendation for the geometrical shape of the clamps was proposed. This publication is an extended version of the paper “In-Plane Torsion Test—Analysis of the Tool Design”, which was published in the Proceedings of the 14th International Conference on the Technology of Plasticity—Current Trends in the Technology of Plasticity (ISBN 978–3-031–41022-2).