Torsion test twist a material or test component to a specified degree, with a specified force, or until the material fails in torsion. The twisting force of a torsion test is applied to the test sample by anchoring one end so that it cannot move or rotate and applying a moment to the other end so that the sample is rotated about its axis. The rotating moment may also be applied to both ends of the sample but the ends must be rotated in opposite directions. The forces and mechanics found in this test are similar to those found in a piece of string that has one end held in a hand and the other end twisted by the other.
A torsion test can be conducted on most materials to determine the torsional properties of the material. These properties include but are not limited to:
- Modulus of elasticity in shear
- Yield shear strength
- Ultimate shear strength
- Modulus of rupture in shear
Why Perform a Torsion Test?
Many products and components are subjected to torsional forces during their operation. Products such as biomedical catheter tubing, switches, fasteners, and automotive steering columns are just a few devices subject to such torsional stresses. By testing these products in torsion, manufacturers are able to simulate real life service conditions, check product quality, verify designs, and ensure proper manufacturing techniques.
Types of Torsion Tests
Torsion tests can be performed by applying only a rotational motion or by applying both axial (tension or compression) and torsional forces. Types of torsion testing vary from product to product but can usually be classified as failure, proof, or product operation testing.
Torsion Only: Applying only torsional loads to the test specimen.
Axial-Torsion: Applying both axial (tension or compression) and torsional forces to the test specimen.
Failure Testing: Twisting the product, component, or specimen until failure. Failure can be classified as either a physical break or a kink/defect in the specimen.
Proof Testing: Applying a torsional load and holding this torque load for a fixed amount of time.
Operational Testing: Testing complete assemblies or products such as bottle caps, switches, dial pens, or steering columns to verify that the product performs as expected under torsion loads.