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What is Torsion Testing?

Torsion testing is a form of mechanical evaluation that assesses materials or devices while under angular displacement-induced stress. This method can be categorized into two distinct approaches:

  • Testing Raw Materials: Evaluating materials like metal wires or plastic tubing to determine properties such as shear strength and modulus.

  • Functional Testing of Finished Products: Subjecting finished products like screws, pharmaceutical bottles, and sheathed cables to torsional stress.

Purpose of Torsion Testing​

Performing torsion tests serves various purposes:

  • Material Optimization: Engineers seeking to enhance products often examine the materials used. For instance, in vehicle drive trains, metals endure complex loading, primarily torsion. Engineers aiming for fuel efficiency might alter the driveshaft material to reduce vehicle weight, a process facilitated by torsion testing.

  • Quality Assurance for Finished Products: Numerous products, including biomedical tubing, switches, and fasteners, encounter torsional forces in daily use. Torsional testing aids manufacturers in simulating real-life conditions, ensuring product quality, verifying designs, and refining manufacturing techniques.

Types of Torsion Tests​

Torsion tests encompass various methodologies based on the type of loading and intended outcomes:

  • Torsion Only: Applying solely torsional loads to the test specimen.

  • Axial-Torsion: Applying both axial (tension or compression) and torsional forces.

  • Failure Testing: Subjecting the product, component, or specimen to twisting until failure, categorized as physical breakage or the formation of a kink/defect.

  • Proof Testing: Applying a torsional load and sustaining this torque for a fixed duration.

  • Functional Testing: Assessing complete assemblies or products like bottle caps, switches, dial pens, or steering columns under torsion loads to ensure expected performance.

Torsion Testing Equipment​

Torsion testing utilizes varied systems based on specific applications. Labs may opt for dedicated torsion-only systems like Instron's MT MicroTorsion Series or adapt existing universal testing machines with fixtures like Torsion Add-On 3.0 for biaxial testing. Functional testing of finished products is often conducted using dynamic fatigue systems like Instron's Electropuls.