课程名称︰材料科学导论 课程性质︰选 课程教师︰吕宗昕 开课学院：化工 开课系所︰工 考试日期（年月日）︰2011 6 21 考试时限（分钟）：2hr 是否需发放奖励金：yes （如未明确表示，则不予发放） 试题 : 1.please state the physical meaning of the following terms: (a)fatigue (b)stress raiser (c)creep (d)Frenkel defect (e)Fermi level 2.(a)a polystyrene component must not fail when a tensile stress of 1.5 MPa is applied. determine the max. allowable surface crack length if the surface energy of polystyrene is 0.7 J/m^2. assume a modulus of elasticity of 2.5GPa (b)some aircraft component is fabricate ed from an aluminum alloy that has a plane strain fracture toughness of 40MPa√m. It has been determined that fracture results at a stress of 270MPa when the max. internal crack length is 3mm. for the same component and alloy, will fracture occur at a stress level of 310MPa when the maximum internal crack length is 2.2 mm? please calculate the question and explain the reason 3.(a)calculate the minimum cation-to -anion radius ratio for a coordination number of 4. (b) draw the crystal structure for NaCl and BaTiO3. 4.(a)calculate the e and hole concentrations at 50度C. the eletrical conductivity at 50度C is 10.5e-4 (sigma-m)^-1 , and the electron and hole mobilities are 0.18 and 0.064(m^2/V-s e=1.6e-19 (b) when 3e15 m^-3 phosphorus is doped in silicon, calculate the coductivity at 50度C 5.a parallel-plane capacitor has an area of 9e-4 m^2 and a plate-separation of 5e-4m. the applied voltage is 20V. the polarization of the inserted material is 6e-7C/m^2. calculate the dielectric constant of the material, the capacitance of the capacitor, the stored charge on each plate, and the dielctric displacement. --

※ 发信站: 批踢踢实业坊(ptt.cc) ◆ From: 140.112.54.15