中北大学材料科学与工程基础试题及答案

中北大学2009-2010 学年第 一 学期末考试试题（B卷） 材料科学与工程基础 使用班级： 07030141~2, 07030241~2，07030341~2，07030441~2，07030541~4 总分 一、选择（10分，每题0.5分） 得分 1. 11. 2. 12. 3. 13. 4. 14. 5. 15. 6. 16. 7. 17. 8. 18. 9. 19. 10. 20. 1. The thermal behavior of solids can be represented in terms of .

A: thermal conductivity B: electrical conductivity

C: dielectric constant D: elastic modulus 2. The stimulus of magnetic properties is . A: load B: force C: electric field D: magnetic field

3. are utilized as a radial steel reinforcement in automobile tires, in filament-wound rocket casings, and in wire-wound high-pressure hoses.

A: Fibers B: Wires C: Particles D: Whiskers

4. For BCC structure, a total of atoms are assigned to a given unit cell. A: four B: two C: six D: eight 5. Atomic packing factor of FCC structure is . A: 0.68 B: 0.34 C: 0.74 D: 0.56 6. test is nondestructive. A: Tensile B: Hardness C: Compressive D: Shear 7. is A2B3 type crystal structures. A: α-Al2O3 B: ZrO2 C:MgO D: CsI 8. Hydrocarbons are composed of hydrogen and carbon. The intramolecular bonds are . A: metallic B: ionic C: covalent D: van der Waals 9. With increasing temperature, E diminishes for all materials but some of the materials. A: plastic B: rubber C: ceramic D: metal 10. A load produces a contraction and negative linear strain.

A: Compressive B: Shear C: Torsional D: Tensile 11. Elastic modulus may be thought of as . A: toughness B: stiffness C: hardness D: strength 12. is based on the number fraction of molecules within the various size ranges. A: Number-average molecular weight B:ar weight C: Z-average molecular weight D: Viscosity-average molecular weight 13. has the fluorite structure crystal structure. A: CsBr B: CsI C: ZrO2 D:MgO 14. is the pulling of a metal piece through a die having a tapered bore by meansof a tensile force that is applied on the exit side. A: Drawing B: Extrusion C: Casting D: Rolling 15. The corresponds to the temperature at which the viscosity is 1012 Pa·s. A: melting point B: working point C: softening point D: annealing point Weight-average molecul

16. Condensation polymerization is used in the synthesis of .

A: phenolformaldehyde B: polyvinyl chloride C: polyethylene D: polystyrene

17. Index of and are representative optical properties.

A: load; force B: heat capacity; thermal conductivity

C: modulus; strength D: refraction; reflectivity 18. consist of a metal as the matrix, with fibers as the reinforcement medium.

A: Polymer-matrix composites B: Metal-matrix composites C: Ceramic-matrix composites D: Carbon–carbon composites 19. The stress at fracture using this flexure test is known as the .

A: yielding strength B: tensile strength C: flexural strength D: shear strength

20. For polymers, the yield point is taken as a maximum on the curve; the stress at this maximum is the yield strength. Tensile strength is the stress at which fracture occurs. A: metal B: ceramic C: composite D: plastic

得分

二、名词解释（20分，每题4分） 1.Crystal

2.Thermoplastics

3. Annealing Processes 4.Specific volume 5.Homopolymer

三、简答题（30分，1，2，3必做题，每题7分，4，5，6得分 选做题，选择其中之一， 9分） 4. Sketch mer structures for the following polymers: 5. Why Study Composites? 四、计算题（40分，每题10分） 得分 1. Consider a cylindrical titanium wire 3.0 mm in diameter and 2.5×10mm long. Calculate its elongation when a load of 500 N is applied. Assume that the deformation is totally elastic. 42. Copper has a FCC crystal structure, an atomic radius of 0.128 nm, and an atomic weight of 64.85 g/mol. (1) Compute its density; (2) the atomic packing factor.

(3) A cylindrical specimen of some alloy 8 mm in diameter is stressed elastically in

tension. A force of 15,700 N produces a reduction in specimen diameter of 5×10 mm. Compute

-3

Poisson’s ratio for this material if its modulus of elasticity is 140 GPa.

(4) Below, molecular weight data for a polypropylene material are tabulated. Compute

(a) the number-average molecular weight, (b) the weight-average molecular weight, (c) the number-average degree of polymerization, and (d) the weight-average degree of polymerization.

Molecular Weight xi wi Range (g/mol ) 5000-10000 10000-15000 15000-20000 20000-25000 25000-30000 3000040000

0.05 0.16 0.24 0.28 0.20 0.07 0.02 0.10 0.20 0.30 0.27 0.11

(3) A cylindrical specimen of some alloy 8 mm in diameter is stressed elastically in

tension. A force of 15,700 N produces a reduction in specimen diameter of 5×10 mm. Compute

-3

Poisson’s ratio for this material if its modulus of elasticity is 140 GPa.

(4) Below, molecular weight data for a polypropylene material are tabulated. Compute

(a) the number-average molecular weight, (b) the weight-average molecular weight, (c) the number-average degree of polymerization, and (d) the weight-average degree of polymerization.

Molecular Weight xi wi Range (g/mol ) 5000-10000 10000-15000 15000-20000 20000-25000 25000-30000 3000040000

0.05 0.16 0.24 0.28 0.20 0.07 0.02 0.10 0.20 0.30 0.27 0.11

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