Tensile Testing
From standardized tensile testing to custom dynamic tensile testing at various temperatures, Standard Mechanics provides a one-stop-shop for your tensile testing needs. Let us know if you have a tensile testing need for your project. Our engineers can help you determine the test that best suites your application.
Tensile Testing Data
Tensile testing provides material properties critical to engineering applications such as
- Young’s Modulus
- Yield Strength
- Ultimate Tensile Strength
- Ductility
Engineering vs True Stress and Strain
Tensile results for materials are often reported in two ways: True Stress vs True Strain or Engineering Stress vs Engineering Strain.
True stress vs strain results account for a changing cross sectional area during testing. Since this area decreases in tensile tests, the true stresses are higher than the engineering stresses.
Converting between the engineering stress and strain found from testing to true stress and strain can be done with two formulas.
Engineering stress and strain to true stress and strain conversions.
Strain Measurement Methods
Strain is a unitless value that scales displacement to a predetermined length. In tensile testing, engineering strain is computed using a gage length and the displacement of either side of this span. The most common method of acquiring displacement and strain data is via an extensometer, which can (at lower speeds) provide a closed loop control system where a user can input a strain rate for the tensile test to be run at. The type of extensometer needed varies but can depend on the size of specimen, specimen material, conditions of test, or testing standards.
Clip-on Extensometer
One of the simplest extensometers is a clip-on extensometer. These extensometers have two sharp knife edges that attach directly onto the specimen on either side of the gage section usually via clips. As the specimen is pulled apart, the knife edges of the extensometer are spread apart, and the strain is computed from the amount of separation.
Non-Contact Extensometer
A second type of extensometer is a non-contact or optical extensometer. These can be used when the tests require temperatures that are too hot or too cold for a regular extensometer. Some of these extensometers require a certain type of reflective material to be placed on the specimen which the optics can track. Others do not have this targeted requirement.
Digital Image Correlation
At higher speed tests, the traditional contact and non-contact extensometers are limited in their ability to measure strain. At these speeds, high speed cameras are used to capture images of the test at speeds up to 5,000,000 frames per second. These images can then be post-processed to measure the strain on the specimen during the test. This process is called digital image correlation (DIC).
More Questions?
Interested in learning how these tests could work for you? Contact Standard Mechanics today to learn more about our tensile testing abilities, and how they could impact your companies engineering and product design decisions.
