What is a compression test?
Compression tests, along with tensile and bending tests, are one of the most basic types of mechanical testing. Compression tests are used to measure the behavior of materials under crushing loads, usually on test strips (usually either cubic or cylindrical) using a universal tester compression disc or a dedicated jig. It is carried out by applying compression pressure. As part of the test, different material properties are computed and shown as a stress-strain diagram. It is used to determine qualities such as elastic limits, proportional limits, yield points, yield strengths, and, for some materials, compressive strengths.
The compression test is performed with a universal testing machine. From 0.02 N to 2,000 kN, these compression testing machines are available in a range of sizes and load capabilities. Higher load applications require floor-standing frames like those in Instron’s Industrial series, however, the majority of low-stress tests are carried out on desktop testers like those in the 6800 series.
The universal material tester must be equipped with test software and accessories such as application compression discs and extensometers. The type of material you are testing will determine the type of accessories you will need. In addition, any material can be tested by changing the jig with one device as long as it is within the load capacity range of the testing machine.
The purpose of a compression test
At many phases of the manufacturing process, compression testing equipment enables producers to evaluate the reliability and security of materials, components, and products. It is expected to be used in a variety of applications, from strength tests for automobile windshields to durability tests for concrete beams used in construction. Materials with high tensile strength tend to have low compressive strength (although this is not always the case). Similarly, materials with high compressive strength tend to have low tensile strength.
Compression tests are frequently performed on finished goods, in contrast to tensile testing, which is carried out to ascertain the tensile characteristics of a specific material. Commonplace products that require compressive strength testing, such as tennis and golf balls, water canisters, protective containers, plastic pipes, and furniture, are tested. For example, an engineer wants to save plastic by making a thin water bottle. However, the water bottle must be strong enough to be packed and transported on a pallet. Compression testing allows engineers to adjust the balance between product strength and material savings.
Industry-specific testing requirements
Compression testing of various materials is covered by a number of ASTM and ISO standards. For instance, the polyurethane foam indentation deformation standard ASTM D3574 is followed by the mattress, car, and furniture industries. This test determines the foam’s initial softness by measuring the force applied when it is crushed to 25% of its original thickness. The strength of bearing capacity is measured by measuring the force when compressed to 65% of the original thickness. Automotive seat engineers specify the foam indentation deformation value required for the final product, test several times per shift at the manufacturing site, and all manufactured seats have the same feel in terms of softness and support.