资料工程课后习题(国外英文资料).docVIP

材料工程课后习题(国外英文资料) ? BaoShen lattice effect: refers to the metal materials by the preloaded produce a small amount of plastic deformation, a higher load, then specified residual elongation stress increases, the reverse load, reduce the imagination of specified residual elongation ? What is the modulus of elasticity of a metal? Why is it an unsensitive mechanical name? Answer: the elastic modulus of metal mainly depends on the nature of metallic bonding and bonding force between the atoms, and the material composition and organization of its impact is not big, so it is a performance index is not sensitive to the organisation, which is the main characteristic of elastic modulus on performance. The composition of the material and the organization will have a significant effect on the strength of the material, such as the yield strength and tensile strength, but not the stiffness of the material. The difference between a flexible fracture and a brittle fracture. Why is brittle fracture more dangerous? ? Ductile fracture: is the fracture before the fracture that has obvious macroscopic plastic deformation? Features:? The fracture surface is usually parallel to the maximum shear stress and the main stress is 45 degrees. ? The fracture is fibroid (microcrack expansion and connection), gray color (weak reflecting ability). ? Break three elements:? The ratios of the three regions of the fiber area, the radiation area, and the shear lip were related to the strength of the material. ? Good plastic, heavy radiation; ? The plastic difference, the radiation becomes thinner and even disappears. ?? ? Brittle fracture: before the fracture, there is no plastic deformation, sudden break. ? Features:? The fracture surface is perpendicular to the positive stress, and the fracture is smooth and smooth, radiating or crystallized. ? Note: brittle fracture also produces microplastic deformation. ? The reduction rate of the section is less than 5%, which is brittle fracture and more than 5% i