Larson Miller relationship

The Larson-Miller relationship enables thermally activated processes in materials , especially creep failure , to be universally described using a time-temperature equivalence approach. It can also be used to reduce the hardness of hardened steel parts during tempering ( see also: Hollomon-Jaffe parameters ).

The Larson Miller parameter

${\displaystyle LMP=T\cdot (log(t)+C)}$

measures the "thermal load" that acts on the material at constant temperature T (in Kelvin ) over time t (in hours). The experimentally determined material constant C for iron , nickel and cobalt-based materials is 20. The temperature consequently has a much stronger influence than the time.

The formula was drawn up by JH Holloman and LC Jaffe in the 1940s and used a few years later by FR Larson and J. Miller to describe the creep behavior of steels. It is used today due to extensive experimental investigations of creep and fracture processes and the like. a. to predict the service life of turbine blades in aircraft turbines .

literature

• JH Holloman, LC Jaffe (1945): Time-Temperature Relations in Tempering Steel . Trans. AIME, Iron and Steel Division 162, pp. 223-249.
• FR Larson, J. Miller (1952): A Time-Temperature Relationship for Rupture and Creep Stresses . Trans. ASME 74, pp. 765-775.