Torsion Test Equipment

Torsion testers

The torsion test is a mechanical test method used to examine the deformation of a specimen through a twisting/rotating motion.

Torsion, in its simplest form, is the action of twisting. Many everyday materials, components, component assemblies, and end-user products used in various industries are designed with the primary purpose of supporting this direction of movement. Products include screws, springs, syringe components, wire, tubing, and many more.

In the world of materials testing, we use torsion testers to simulate this twisting motion and help manufacturers determine important material properties, including:

Maximum torque

The maximum torque (twisting force) value that can be applied before specimen failure. Once the maximum torque is found on a screw or bolt, for example, a safety factor can be calculated and built into the torque strength specifications of that product.

Torsional strength

The ultimate strength of a specimen, and the maximum torsional stress that a specimen that is subjected to a torsional load can withstand before failure.

Torsional shear stress

Shear stress that acts on a transverse cross section of the specimen due to torsional motion. Torsional loading creates uneven stress distribution over the cross section of the specimen, ranging from zero in the center to maximum torsional shear stress at the edge of the specimen.

Modulus of elasticity in shear

Elastic shear stiffness defined as the ratio of shear stress to shear strain. When comparing identical products, the higher the modulus of elasticity of the material, the greater the stiffness. The greater the stiffness or rigidity of a structure, the more force is required to cause deformation.

Breaking angle of the specimen

The breaking angle provides a measure of the ductility of a material when undergoing a torsional moment. According to ASTM F543-13, for example, a medical bone screw with a greater breaking angle may provide an earlier tactile warning to the surgeon that it is reaching its maximum torsional strength.

Depending on your torsion test application, torsion testing machines can be set up to run on material specimens up to the point of failure or based on a defined torque and duration. They can also be run on finished product assemblies, such as pharmaceutical pen injectors or screw caps to determine proper function of the device.