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.
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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.