《材料科学与工程基础》英文影印版习题及思考(11)

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nor an elongation of more than 0.9 mm when the applied load is 24,500 N,

which of the four metals or alloys listed below are possible candidates?

7.25 Figure 7.33 shows the tensile engineering stress–strain behavior for a steel alloy.

(a) What is the modulus of elasticity?

(b) What is the proportional limit?

(c) What is the yield strength at a strain offset of 0.002?

(d) What is the tensile strength?

7.27 A load of 44,500 N is applied to a cylindrical specimen of steel (displaying the

stress–strain behavior shown in Figure 7.33) that has a cross-sectional diameter of 10 mm .

(a) Will the specimen experience elastic or plastic deformation? Why?

(b) If the original specimen length is 500 mm), how much will it increase in

length when t his load is applied?

7.29 A cylindrical specimen of aluminum

having a diameter of 12.8 mm and a gauge

length of 50.800 mm is pulled in tension. Use

the load–elongation characteristics tabulated

below to complete problems a through f.

(a) Plot the data as engineering stress

versus

engineering strain.

(b) Compute the modulus of elasticity.

(c) Determine the yield strength at a

strain

offset of 0.002.

(d) Determine the tensile strength of this

alloy.

(e) What is the approximate ductility, in percent elongation?

(f ) Compute the modulus of resilience.

7.35 (a) Make a schematic plot showing the tensile true stress–strain behavior for a

typical metal alloy.

(b) Superimpose on this plot a schematic curve for the compressive true

stress–strain behavior for the same alloy. Explain any difference between this curve and the one in part a.

(c) Now superimpose a schematic curve for the compressive engineering

stress–strain behavior for this same alloy, and explain any difference between this curve and the one in part b.

7.39 A tensile test is performed on a metal specimen, and it is found that a true plastic

strain of 0.20 is produced when a true stress of 575 MPa is applied; for the same metal, the value of K in Equation 7.19 is 860 MPa. Calculate the true strain that

results from the application of a true stress of 600 Mpa.