Fracture toughness tests measure a material’s ability to resist the growth or propagation of a pre-existing flaw. The flaw or defect may be in the form of a fatigue crack, void, or any other inconsistency in the test material. Fracture toughness tests are performed by machining a test sample with a pre-existing crack and then cyclically applying a load to each side of the crack so that it experiences forces that cause it to grow. The cyclic load is applied until the sample’s crack grows. The number of cycles to fracture is recorded and used to determine the material’s fracture growth characteristics.
Fracture toughness is the stress that causes a pre-existing crack or flaw to grow or propagate. It is an important material property in the manufacturing industry, since the presence of flaws is not completely avoidable. The stress intensity factor, which is a function of the flaw size, geometry, and loading, is used to determine a material’s fracture toughness. A material’s stress intensity factor and fracture toughness are related to one another in the same manner that stress and tensile stress are related to each other.