Fracture refers to the positive and tangential separation of several atomic spacings under the action of external forces. Fracture is a complex phenomenon of materials or parts. There are different fracture forms in different mechanical, physical and chemical environments. For example, mechanical parts will undergo fatigue fracture under cyclic stress, creep fracture will occur under high temperature and long-lasting stress, and stress corrosion or corrosion fatigue will occur under corrosive environment. In practical engineering applications, it is often based on engineering components or mechanical parts. The macroscopic morphological characteristics of the fracture are divided into ductile fracture and brittle fracture. Or according to the nature of the load, it is divided into one-time fracture and fatigue fracture.
1. Ductile fracture toughness fracture is the occurrence of fracture after toughness deformation before the strength limit, most of which is transgranular fracture. That is, the crack is cut through the grain and generally occurs under the action of shear stress, also known as shear fracture. .
2, brittle fracture brittle fracture generally occurs before the stress reaches the yield strength, no or only a small amount of plastic deformation. Most of the sudden expansion occurs along the grain boundary, also known as grain boundary fracture, the fracture is crystalline, smooth and bright, said It is a cleavage surface, so this fracture is also called cleavage fracture. Low temperature, high strain rate, stress concentration, coarse grain and brittle materials are all favorable for cleavage, and the crack growth rate is fast, which often causes serious damage accident.
3, one load break once trimming break is a static stretch, static compression, static torsion, static bending or a shock under a shock.
4. Fatigue Fatigue Fatigue fracture is a repeated loading fracture, that is, the phenomenon of fracture occurs after repeated stress or energy load cycle. It is estimated that the fatigue fracture failure of mechanical failure failure accounts for about 80%.