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.

Our torsion testing machines and torsion drives cover a wide range of torsion tests and can be adapted to your specific applications.

• TorsionLine
  Torsion testing machine with horizontal torsion axis, maintenance-free AC servo drive and torque range from 20 Nm to 500 Nm or 1,000 Nm to 2,000 Nm for single-axis torsion tests.
• zwickiLine
  Equipped with either a 2 Nm or 20 Nm torsion drive for test loads up to 5 kN for axial tests and axial torsion tests (tensile or compression combined with torsion)
• AllroundLine
  Table-top or floor-standing machine equipped with a 200 Nm or 2,000 Nm torsion drive for test loads up to 250 kN for axial tests and axial torsion testing (tensile or compression combined with torsion)
• Torsion drives
  Modular torsion drives with torques from 2 Nm to 2,000 Nm for easy retrofitting of your existing zwickiLine or AllroundLine materials testing machine.

• ASTM A938-18 – Standard Test Method for Torsion Testing of Wire
  Wire is twisted at a defined speed and the number of total turns to fracture is determined. If the number of turns is satisfactory, the specimen is considered to have passed the test.
• ASTM F543-13 – Standard Specification and Test Methods for Metallic Medical Bone Screws
  This standard applies to metallic bone screws that are implanted into bone. The torsional strength is tested to ensure that the screw does not break during insertion or removal. Properties measured include the torsional yield strength, maximum torque, and the breaking angle under standard conditions.
• ISO 7800 – Metallic materials – Wire – Simple torsion test
  Used to determine the ability of metallic wire with a diameter or characteristic dimension from 0.1 mm to 14 mm to undergo plastic deformation during simple torsion in one direction. The test is run until the specimen breaks or until a specified number of turns is reached.
• ISO 7206-8 – Implants for surgery – Partial and total hip joint prostheses – Part 8:Endurance performance of stemmed femoral components with application of torsion
  Femoral components are tested in their ready-for-use condition and may not fracture during the specified number of cycles and test load, as specified by the standard.