Fundamentals of Materials Science and Engineering: An Integrated Approach, 3e

GTBL042-09 GTBL042-Callister-v3 October 4, 2007 11:53

2nd Revised Pages

338 • Chapter 9 / Failure

DESIGN PROBLEMS

Principles of Fracture Mechanics

9.D1 (a)For the thin-walled spherical tank dis-

cussed in Design Example 9.1, on the

basis of critical crack size criterion [as

addressed in part (a)], rank the follow-

ing polymers from longest to shortest

critical crack length: nylon 6,6 (50%

relative humidity), polycarbonate, poly

(ethylene terephthalate), and poly(methyl

methacrylate). Comment on the magni-

tude range of the computed values used

in the ranking relative to those tabulated

for metal alloys as provided in Table 9.3.

For these computations, use data con-

tained in Tables B.4 and B.5 in Appen-

dix B.

(b)Now rank these same four polymers rel-

ative to maximum allowable pressure

according to the leak-before-break crite-

rion, as described in the (b) portion of De-

sign Example 9.1. As above, comment on

these values in relation to those for the

metal alloys that are tabulated in Table

9.4.

Data Extrapolation Methods

9.D2Consider an S-590 iron component (Figure

9.39) that is subjected to a stress of 55 MPa

(8000 psi). At what temperature will the rup-

ture lifetime be 200 h?

9.D3Consider an 18-8 Mo stainless steel compo-

nent (Figure 9.42) that is exposed to a temper-

ature of 650◦C (923 K). What is the maximum

allowable stress level for a rupture lifetime of

1 year? 15 years?

Stress (10

3 psi)

103 T(20 + log tr)(°R–h)

103 T(20 + log tr)(K–h)

25 30 35 40 45

12 16 20 24 28

50

Stress (MPa)

10

100

10

100

1

Figure 9.42 Logarithm stress

versus the Larson–Miller

parameter for an 18-8 Mo

stainless steel. (From F. R. Larson

and J. Miller,Trans. ASME, 74 ,

765, 1952. Reprinted by

permission of ASME.)