机械工程材料（Mechanical engineering material）.docVIP

机械工程材料（Mechanical engineering material） Chapter 1 mechanical properties of metal 1. The performance of metal materials includes performance and process performance. 2. Mechanical properties refer to the characteristics of the metal under the action of external forces. The commonly used indexes include strength, hardness, plasticity, toughness and fatigue strength. 3. Strength refers to the ability of metal materials to resist plastic deformation and fracture. Common strength indicators are: elastic limit sigma e, yield sigma s, tensile strength sigma b 5. Plasticity refers to the ability of metal materials to produce plastic deformation before fracture. The commonly used indexes have the elongation rate and the reduction of cross section Hardness is the ability of materials to resist local plastic deformation, indentation or scratches. Hardness is a measure of metal hardness. The hardness of the material is measured by hardness test. 7. Hardness test methods include: 1 brinell hardness (HBW hard alloy steel ball, HBS quenching steel ball) 2 rockwell hardness HR 3 vickers hardness HV The larger the impact, the better the materials toughness. The crystal structure and crystallization of the metal 1. Single crystal has anisotropic and polycrystal has isotropic. 2. The common lattice types include: the body centered cubic lattice of the center of the body and the lattice of the six squares. 3. Crystal defects include: 1. Defect of points; defect of surface. 4. Point defect is a defect that is small in length, width and height. The most common point defect is lattice vacancy and interstitial atom. 5. Line defect refers to the defect of the present distribution in the crystal, the most common defect is the dislocation of various types. 6. Surface defect is the defect of the surface distribution in the crystal, and the common defect is the grain boundary and the subgra