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

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

2nd Revised Pages

330 • Chapter 9 / Failure

Stress (10

3 psi)

Stress (MPa)

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

100

10

1

1000

100

10

Figure 9.39 Logarithm stress

versus the Larson–Miller

parameter for an S-590 iron.

(From F. R. Larson and J.

Miller,Trans. ASME, 74 , 765,

1952. Reprinted by
      permission of ASME.)

rupture tests at temperatures in excess of those required, for shorter time periods,

and at a comparable stress level, and then making a suitable extrapolation to the in-

service condition. A commonly used extrapolation procedure employs the Larson–

Miller parameter, defined as

T(C+logtr) (9.22)

The Larson-Miller

parameter—in terms

of temperature and

rupture lifetime whereCis a constant (usually on the order of 20), forTin Kelvin and the rupture

lifetimetrin hours. The rupture lifetime of a given material measured at some specific

stress level will vary with temperature such that this parameter remains constant. Or,

the data may be plotted as the logarithm of stress versus the Larson–Miller parameter,

as shown in Figure 9.39. Utilization of this technique is demonstrated in the following

design example.

DESIGN EXAMPLE 9.2

Rupture Lifetime Prediction

Using the Larson–Miller data for S-590 iron shown in Figure 9.39, predict the time

to rupture for a component that is subjected to a stress of 140 MPa (20,000 psi) at

800 ◦C (1073 K).

Solution

From Figure 9.39, at 140 MPa (20,000 psi) the value of the Larson–Miller param-

eter is 24.0× 103 , forTin K andtrin h; therefore,

24. 0 × 103 =T(20+logtr)

=1073(20+logtr)