page_title: Tensile testing
section_title: Tensile specimen
hierarchical_section_title: Tensile testing / Tensile specimen
caption_attribution_description: Tensile test of an AlMgSi alloy. This is a ductile fracture type, as seen by the local necking and the cup and cone fracture surfaces.
context_page_description: Tensile testing, also known as tension testing, is a fundamental materials science and engineering test in which a sample is subjected to a controlled tension until failure. Properties that are directly measured via a tensile test are ultimate tensile strength, breaking strength, maximum elongation and reduction in area. From these measurements the following properties can also be determined: Young's modulus, Poisson's ratio, yield strength, and strain-hardening characteristics. Uniaxial tensile testing is the most commonly used for obtaining the mechanical characteristics of isotropic materials. Some materials use biaxial tensile testing. The main difference between these testing machines being how load is applied on the materials.
context_section_description: The preparation of test specimens depends on the purposes of testing and on the governing test method or specification.  A tensile specimens is usually a standardized sample cross-section. It has two shoulders and a gage (section) in between. The shoulders are large so they can be readily gripped, whereas the gauge section has a smaller cross-section so that the deformation and failure can occur in this area.
  The shoulders of the test specimen can be manufactured in various ways to mate to various grips in the testing machine (see the image below). Each system has advantages and disadvantages; for example, shoulders designed for serrated grips are easy and cheap to manufacture, but the alignment of the specimen is dependent on the skill of the technician. On the other hand, a pinned grip assures good alignment. Threaded shoulders and grips also assure good alignment, but the technician must know to thread each shoulder into the grip at least one diameter's length, otherwise the threads can strip before the specimen fractures.
  In large castings and forgings it is common to add extra material, which is designed to be removed from the casting so that test specimens can be made from it. These specimens may not be exact representation of the whole workpiece because the grain structure may be different throughout. In smaller workpieces or when critical parts of the casting must be tested, a workpiece may be sacrificed to make the test specimens. For workpieces that are machined from bar stock, the test specimen can be made from the same piece as the bar stock.
  The repeatability of a testing machine can be found by using special test specimens meticulously made to be as similar as possible.
  A standard specimen is prepared in a round or a square section along the gauge length, depending on the standard used. Both ends of the
  specimens should have sufficient length and a surface condition such that they are firmly gripped
  during testing. The initial gauge length Lo is standardized (in several countries) and varies with the
  diameter (Do) or the cross-sectional area (Ao) of the specimen as listed
  The following tables gives examples of test specimen dimensions and tolerances per standard ASTM E8.
caption: An aluminium alloy tensile specimen, after testing. It has broken, and the surface where it broke can be inspected.
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