Larson-Miller Parameter (LMP)
Definition
A temperature-time combination parameter T(C + log t_r) used to correlate and predict rupture life across different temperature-stress combinations for a given alloy.
- Field
- Creep and elevated-temperature failure analysis
- Formula components
- Temperature, constant C, log of rupture time
- Purpose
- Correlate rupture life across stress-temperature combinations
- Application
- Predicting long-term creep life from short-term test data
Common questions
Why is the Larson-Miller parameter useful in failure investigations?+
It lets an investigator extrapolate a component's expected rupture life at its actual service temperature and stress from accelerated laboratory tests run at higher temperatures, without waiting years for a real-time test to fail.
What does a component's actual failure time versus its LMP-predicted life indicate?+
A failure well before the predicted life points to an additional degradation mechanism, overload, material defect, or overheating event beyond normal creep, prompting closer metallurgical examination of the fracture surface.
Related terms
- Creep
- Time-dependent plastic deformation of a material under sustained stress at elevated temperature, occurring at stress levels below the conventional yield strength.
- Grain-Boundary Sliding
- Relative motion of adjacent grains along their shared boundary, a key deformation mechanism at elevated temperature that opens voids at triple points...
- Hot Corrosion
- Accelerated degradation of a superalloy or coated turbine component by molten sulfate or vanadate deposits that flux and dissolve the protective oxide...
- Minimum Creep Rate
- The steady-state strain rate during secondary creep, the single most important material parameter for structural life assessment under creep conditions.
- Reheat Cracking
- Intergranular cracking in the heat-affected zone of welds in certain alloy steels during post-weld heat treatment or early elevated-temperature service, caused by...