What is a Tensile Test?

There are few more fundamental mechanical tests than a tensile test on a product, component, or material. When a specimen is loaded in tension, it is subjected to forces that pull it apart and are applied to opposite faces along the same axis. These tests are easy to set up and carry out, and they provide a wealth of information on the examined substance. In contrast to compression tests, tensile tests aim to break down the material rather than compress it.

What’s the Point of a Tensile Test?

The mechanical properties of isotropic materials are often obtained through tensile testing. The results of tensile tests, along with those of compression and flexural bend tests, provide crucial data for describing the properties of materials. Specifications for materials include testing properties to help engineers choose the best materials for their projects. They are employed in the evaluation of novel materials and methods.

Testing the Limits of Tensile Strength

The tensile strength of a material is a primary consideration for product developers and manufacturers. The maximum allowable stress during stretching or pulling is known as the ultimate tensile strength (UTS) of a material. The load cell on the testing machine measures the applied force, and the controller program calculates the stress. The ultimate tension strength (UTS) of a test sample is determined by dividing the peak tension force by the sample’s cross sectional area. Common material tests include tensile testing, in which the material is stretched under controlled conditions until it cracks. Whether the material is ductile, brittle, or both will determine how the tensile strength compares to the specimen’s strength at break. The ultimate tensile strength of ductile materials is often greater than that of brittle ones, while in the case of brittle materials, it is near the yield point.

Ultimate tensile strength, breaking strength, maximum elongation, and area reduction are all properties that can be directly determined with a tensile strength test. A tensile test, with the engineering stress recorded, can reveal the material’s ultimate tensile strength. The ultimate tensile strength is represented by the stress at the peak of the stress-displacement curve.

When simply ultimate tensile strength is being tested, less complex apparatus can be used.

Law of Hooke

In most circumstances, a linear relationship may be seen between the applied force and the elongation of the specimen during the first part of the test. A constant “Hooke’s Law” governs the slope of the line in this region, describing the relationship between stress and strain. The angle at which this line slopes is known as Young’s Modulus.

Yield Strength & Tensile Modulus

Young’s Modulus is most frequently known as the tensile modulus when used for tensile testing. The modulus is a linear-only measure of the elastic stiffness of the sample under test. When the tensile load is taken off the sample, it will go back to where it was before the load was applied. Permanent or plastic deformation happens as the load increases and the curve becomes nonlinear, contradicting Hooke’s Law. The material’s yield strength, also called its proof strength, is reached when a sample is permanently stretched above its elastic limit. The elastic limit, tensile strength, yield point, yield strength, elongation, and Young’s modulus are typical components of a set of tensile test data or results. 

By adding a strain sensor (e.g., an extensometer) and the proper software to the ultimate tensile strength testing apparatus, the same apparatus may also measure modulus and yield strength.

Uses for Tensile Testing

The tensile strength, yield strength, ductility, and other qualities of a material can be evaluated with a tensile test. You need to know if the materials you choose for your final product or prototype will hold up in the real world. Understanding the material’s strength can help you avoid employing something that won’t hold up well under pressure by warning you when you’re approaching the material’s breaking point. A tensile test can help you choose the most durable fabrics, metal alloys, paper pulp, and other raw materials.

Video 01: Tensile Test