What is Compression Testing?
Compression testing is a fundamental type of mechanical testing that is used to determine a material’s behavior under applied crushing loads. Compression tests are typically conducted by applying compressive pressure to a test specimen (usually of either a cuboid or cylindrical geometry) using platens or specialized fixtures on an electromechanical or universal testing machine. During the test, various properties of the material are calculated and plotted as a stress-strain diagram which is used to determine qualities such as elastic limit, proportional limit, yield point, yield strength, and, for some materials, compressive strength.
Why Perform a Compression Test?
Compression testing allows manufacturers to assess the integrity and safety of materials, components, and products during several phases of the manufacturing process. The potential applications can vary from strength testing of a car windshield to endurance testing of concrete beams used in construction. Materials that exhibit high tensile strength tend to (but do not always!) exhibit low compressive strength. Likewise, materials high in compressive strength tend to exhibit low tensile strength. Therefore, compression testing is often used on brittle materials such as concrete, metals, plastics, ceramics, composites, and corrugated materials like cardboard. These materials are often used in a load-bearing capacity where their integrity under compressive forces is critical.
Ultimate Compressive Strength
The ultimate compressive strength of a material is the value of compressive stress reached when the material fails completely. When brittle materials reach their ultimate compressive strength they are crushed, and the load drops drastically. Materials with higher ductility, (most plastics) do not rupture, but instead continue deforming until the load is no longer being applied to the specimen, but rather between the two compression platens. In these cases, compressive strength can be reported as specific deformations such as 1%, 5%, or 10% of the test specimen's original height.
Applicable Testing Standards