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What is Tensile Testing?

   

Tensile Testing is a form of tension testing and is a destructive engineering and materials science test whereby controlled tension is applied to a sample until it fully fails.

This is one of the most common mechanical testing techniques. It is used to find out how strong a material is and also how much it can be stretched before it breaks. This test method is used to determine yield strength, ultimate tensile strength, ductility, strain hardening characteristics, Young's modulus and Poisson's ratio.

If you have any questions or need help, email us to get expert advice:

contactus@twi.co.uk


Test Properties

Yield Strength

The yield strength is the point at which plastic deformation occurs under stress. This is determined during testing over a measured gauge length via the use of devices known as extensometers. The devices may be either be mechanical clip on or video where non-contact is a limitation, e.g. elevated temperature testing.

Ultimate Tensile Strength (UTS)

The UTS is the maximum stress that a specimen is exposed to during testing. This may differ from the specimen's strength when breaking depending on if it is brittle, ductile or has properties of both. These material properties can change depending on environment, for example in extreme hot or cold conditions.

Ductility

Ductility relates to the elongation of a tensile test. The percentage of elongation is calculated by the maximum gage length divided by the original gage length. It is commonly described 

Strain Hardening

How much it harderns with plastic defremation.

Modulus of Elasticity

The modulus of elasticity also known as Young's modulus measures the stiffness of a specimen whereby the material will return to its original condition once the load has been removed. Once the material has been stretched to the point where it no longer returns to its original length and permanent deformation is shown, Hooke's Law no longer applies. This is known as the elastic or proportonal limit (also the yield strength).

Poisson's Ratio

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Tensile Specimen Preparation

Tensile test specimens are prepared in a variety of ways depending on the test specifications. The most commonly used specifications are BS EN ISO 6892-1 and ASTM E8M. Most specimens use either a round or square standard cross section with two shoulders and a reduced section gauge length in between. The shoulders allow the specimen to be gripped while the gauge length shows the deformation and failure in the elastic region as it is stretched under load. The reduced cross section gauge length of specific dimensions assists with accurate calculation of engineering stress via load over area calculation.

Why is Tensile Testing Performed?

Tensile testing provides details of the tensile mechanical properties of a material. These properties can be plotted on a graph as a stress/ strain curve to show details such as the point at which the material failed as well as providing details of properties such as the modulus of elasticity, strain and yield strength.  

Tensile testing has a variety of uses, including:

  • Selecting materials for an application
  • Predicting how a material will perform under different forces
  • Determining whether the requirements of a specification, contract or standard are met
  • Demonstrating proof of concept for a new product
  • Proving characteristics for a proposed patent
  • Providing standard quality assurance data for scientific and engineering functions
  • Comparing technical data for different material options
  • Material testing to provide evidence for use in legal proceedings

Find out more information

What are the Advantages of using Tensile Testing?

Flaws in equipment can prove costly and dangerous to the manufacturer and end user of a product. Tensile testing can greatly reduce this danger by determining the engineering stress and other properties of a material or part.

Tensile testing also gives designers and manufacturers data on new materials and their properties so they can determine qualities for future use.

Types of Tension Testing

Other types of tension testing can include:

  • Proof Test where a fixed load is applied to a structure and then removed before the structure enters service. This applied to mooring chains and introduces some permanent deformation and increases the strength.
  • Pressure Test is applied to any equipment that will be under pressure. The level of pressure applied is more than normally experienced.

Tensile Testing Services

Tensile testing is one of the services offered by The Test House at TWI.

Find out more about our mechanical testing services

 

For more information about Tensile Testing please email:


contactus@twi.co.uk