larson-miller parameterfor material of example of

Question

Larson-Miller parameter:

For material of example of calculate life in hours at temperature of 900oC, and at σ = 20 MPa.

Solution

Larson-Miller parameter is given by

m = T (ln t + 85.75)

Use  T = 900 + 273 = 1173 K

But        m = 16.75 × 10⁴

From Example 1.7 at σ = 20 MPa

∴          1173 (ln t + 85.75) = 16.75 × 10⁴

∴          ln t =(16.75 × 10⁴ /1173 )- 85.75

                    = 142.8 - 85.75 = 57.05

∴          t = 5.95 × 10²⁴  hours