论金属的断裂(国外英文资料).docVIP

论金属的断裂(国外英文资料) Material mechanics performance homework Discuss the fracture of the metal Molding class two When the stress reaches the fracture strength of the material, the metal is in addition to the load. Fracture is the process of crack occurrence and development. The three main forms of failure of mechanical parts are wear, corrosion and breakage. The damage is greatest. A broken classification According to the amount of plastic deformation of the metal material before the fracture, it can be divided into toughness fracture and brittle fracture. Toughness fracture: a large plastic deformation before fracture, and a dark grey fibrous fracture. Brittle fracture: there is no obvious plastic deformation before the rupture, and the fracture is smooth and bright. The significant difference between the toughness fracture and brittle fracture is that the crack diffusion is different. Characteristic of ductile fracture is a fracture occurs before obvious macroscopic plastic deformation and brittle fracture basically does not occur plastic deformation before fracture, is a kind of sudden rupture, there is no obvious symptoms, and very dangerous. The malleable fracture and brittle fracture are relative concepts, and under the actual load, different materials may be brittle fracture; The same material is different because of temperature, stress, environment and so on. In general, a small amount of plastic deformation is produced before the brittle fracture, and the reduction rate of the cross sectional specimen is less than 5% for brittle fracture. More than 5% is a malleable fracture. Visible, ductile and brittle metal material is based on a certain amount of plastic deformation under the condition of rules, with the change of the conditions, the material of ductile and brittle behavior will change. The fracture mechanism can be divided into two categories: cleavage and shear fracture. Cleavage fracture is the metal material under certain conditions, such as body centere