Tensile Testing of Plastics   ASTM D 638: Standard Test Method for Tensile Tests of Plastics ISO 527-2: Determination of tensile properties - for moulding and extrusion plastics     Testing the properties of plastics can be done in many different test methods but the most widely used test method is the tensile test. Plastics are some of the most widely used materials in todays world and it is critical to test the tensile strength, elongation, yield point, modulus of elasticity etc.    The ASTM D638 and ISO 527-2 are two different standards that use the standard dogbone or dumb bell shapes for testing on a Universal Testing Machine. Both standards lay out the size and shapes and also gauge lengths of the standardized dumb-bell shapes to be used for tensile testing. Althought similar in its testing methods and specimen shapes it is to be noted that these two standards are not considered equivilents as they do have points that are different from one another.    Standard shapes and dimensions for ASTM D638   Standard shapes for ISO 527-2   Samples are prepared via moulding, machining or press.  Both the ASTM D 638 and ISO 527-2 are often used with an external extensometer to accurately measure the elongation of the specimen. These extensometers are used to measure the deformation from original gauge length during the test in real time to analyze the elongation properties - This is critical in many measurements. Video: Tensile testing of plastic with extensometer   Plastic dog bone/dumb bell shape with extensometer and wedge action tensile grips   When calculating and measuring the tensile properties of plastics it is critical to measure the thickness, width and often the gauge length properly with the appropriate mesaurement devices. These measurements are used by the testing software to measure the cross sectional area which is then in turn used for other calculations such as stress typically expressed in Mpa, kPa, Psi etc. The gauge length is critical in determining the elongation or strain of the specimen being testing.    Some calculation options on Salt_UTM software