《材料科学与工程基础》英文习题及思考题及答案,本人从网上狂搜,兄弟们姐妹们狂下啊,不要辜负我的劳动啊!!!!

8.19 (a) From the plot of yield strength versus (grain diameter)_1/2 for a 70 Cu–30 Zn

cartridge brass, Figure 8.15, determine values for the constants _0 and ky in Equation 8.5.

(b) Now predict the yield strength of this alloy when the average grain diameter is 1.0 _ 10_3 mm.

8.20. The lower yield point for an iron that has an average grain diameter of 5 _ 10_2

mm is 135 MPa . At a grain diameter of 8 _ 10_3 mm, the yield point increases to 260MPa. At what grain diameter will the lower yield point be 205 Mpa ?

8.24 (a)

Show, for a tensile test, that

if there is no change in specimen volume during the deformation process (i.e., A0

l0 _Ad ld).

(b) Using the result of part a, compute the percent cold work experienced by naval brass (the stress–strain behavior of which is shown in Figure 7.12) when a stress of 400 MPa is applied.

8.25 Two previously undeformed cylindrical specimens of an alloy are to be strain

hardened by reducing their cross-sectional areas (while maintaining their circular cross sections). For one specimen, the initial and deformed radii are 16 mm and 11 mm, respectively. The second specimen, with an initial radius of 12 mm, must have the same deformed hardness as the first specimen; compute the second specimen’s radius after deformation.

8.26 Two previously undeformed specimens of the same metal are to be plastically

deformed by reducing their cross-sectional areas. One has a circular cross section, and the other is rectangular is to remain as such. Their original and deformed dimensions are as follows:

Which of these specimens will be the hardest after plastic deformation, and why?

8.27 A cylindrical specimen of cold-worked copper has a ductility (%EL) of 25%. If

its coldworked radius is 10 mm (0.40 in.), what was its radius before

deformation?

8.28 (a) What is the approximate ductility (%EL) of a brass that has a yield strength

of 275 MPa ?

(b) What is the approximate Brinell hardness of a 1040 steel having a yield strength of 690 MPa?

8.41 In your own words, describe the mechanisms by which semicrystalline polymers

(a) elasticallydeform and (b) plastically deform, and (c) by which elastomers elastically deform.

8.42 Briefly explain how each of the following influences the tensile modulus of a

semicrystallinepolymer and why:

(a) molecular weight;

(b) degree of crystallinity;

(c) deformation by drawing;

(d) annealing of an undeformed material;

(e) annealing of a drawn material.

8.43* Briefly explain how each of the following influences the tensile or yield

strength of a semicrystalline polymer and why: