What Is Tension Testing?
Also known as a tensile test, tension testing is one of the most basic, quick and cost-effective ways to find how a material will react under tension when forces are applied. This mechanical test is considered as reliable because it’s standardized and produces easily determinable results.
Tension Tested Material Goes Through This Process
The science behind it is also very straightforward. When you pull on a material, you can determine how strong it is and how much it elongates. A sample is subjected to controlled tension until it breaks. When it does, you’ll know how elastic the material is and the maximum force it can endure before it gives.
Tension testing is often used for quality control, to select a material to use for specific projects and to predict how different materials react when subjected to normal forces.
Properties Measured in Tension Testing
- Poisson’s Ratio
This measures the Poisson Effect or how much the material contracts transverse to the direction of the stretching. Akin to a rubber band, you can notice parts of material being tested thinning as you stretch it.
- Young’s Modulus
It’s the measure of how stiff a solid material is.
- Yield Strength
It’s a material property that points to the amount go stress applied for a material to begin deforming. At this point, any deformation that happens to a material will be irreversible.
- Work Hardening
This property focuses on how much a material strengthens after deformation. A lot of polymers and non-brittle metals are hardened this way. It can be either good or bad, depending on when it happens and what the purpose of the metal is.
What You Need
To start the test, a sample of a material should be obtained. It must have two shoulders — where the material will be gripped — and a gage — the section in between that will be observed for signs of deformation. The stretching, thinning and breaking will happen in the gage.
The machine you need to test the samples is called the universal testing machine. It has two crossheads, one is used to apply tension and the other is adjusted for the length. This machine comes in two types, a hydraulic powered machine, and electromagnetically powered one. Whichever kind you use, it must have the following capabilities to accurately test the specimen: force capacity, precision, speed, and accuracy.
Once you have these, the test can begin. All you have to do is put the material sample in the machine and gradually extend it until it breaks.