Fracture strength is generally tested in three “pure” forms, with the interpretation of the crossovers between these loading scenarios being a complex design process issue. Listed below are the most common tests:
- Tensile Test:In a typical tensile test scenario, a standardized “necked” (not notched) “dog bone” of the material is loaded axially, in pure tension. This scenario evaluates the material’s response to simplified/pure tension and informs about elastic and plastic phases, ultimate tensile strength (UTS), and elongation at break. UTS represents the fracture load stress for the sample.
- Compression Test:Compression testing loads a standardized test block axially, with pure compressive force, which tends to shorten the sample in the compressive axis and bulge the sides, making a complex load scenario. The material’s ability to resist compression is a critical piece of design knowledge and provides compressive strength and compression modulus.
- Impact Test:Impact testing informs as to the material’s ability to resist sudden, dynamic loading, such as that induced by a falling weight or a swinging pendulum. The test involves striking a notched or unnotched sample with a high-velocity impactor, and the energy absorbed or the extent of fracture is measured. This test provides fracture-related properties such as impact strength and toughness.
