ASTM D638

Tensile testing of plastics per ASTM D638 is a widely used and extremely important test method. By simply measuring the force required to pull a test specimen to its breaking point, several material properties can be determined. This data enables both product design engineers and quality managers to accurately predict the performance of their products in end-use applications. This information is critical for developing new products, ensuring compliance to industry or government standards, improving manufacturing and reducing production costs.

 

Sometimes referred to as pull testing, these tests require “dumbbell” or “dogbone” shaped test specimens to be placed in the grips of a universal testing machine and subjected to controlled tension until they fail. Test speed is determined by the material specification and an extensometer is used to measure specimen parameters. The resulting tensile test data reveals essential material properties such as ultimate tensile strength, yield strength, elongation and reduction in area. This information also allows calculations of Young’s modulus and Poisson’s ratio. ASTM D638 is very similar to ISO 527-2, with one key exception being analysis of the non-linear portion of a material’s stress-strain curve. For materials which have little or no linear region, the variation between ASTM and ISO can be significant. Due to the viscoelastic nature of plastics, these tests are often performed with temperature chambers to simulate end-use environments.

 

Solutions for ASTM D638 typically include these types of components:

 

Both the premium MTS Criterion® and the economical MTS Exceed® universal testing machines are ideal for tensile testing of plastics per ASTM D638. These test systems come in a variety of force capacities and frame styles, ranging from 1-column tabletops to larger 2-column floor-standing models. The 30kN and 100kN models also have dual-zone test spaces to reduce set-up times if you frequently change test requirements. And as an alternative to a new load frame, you can modernize the software and controls of your old test system with an MTS ReNew™ Upgrade.