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National Advisory Committee for Aeronautics, Technical Notes - Generalized Master Curves for Creep and Rupture

The similarity of Larson—Miller master curves for rupture life and
minimum creep rate is shown for aluminum, two aluminum alloys, two steels,
and two high-temperature high-strength alloys. In addition, the similar-
ity of master curves for rupture life and for 0.2- and 0.5-percent creep
strain is shown for the aluminum alloys. The approximate invariance of
the product of rupture life and the minimum creep rate is shown for these
materials. With equivalent parameters derived on the basis of this invar—
iance, the master curves for the various applications are generalized
essentially to a single curve in the high-temperature region for each
material. The minimum creep rate and the 0.2- and 0.5-percent creep
strain can be determined from the master curve for rupture by this method
for the materials investigated.

Since the introduction of the Iarson-Miller time-temperature and
rate—temperature parameters for rupture and creep in 1952 (ref. 1), the
practice of summarizing rupture and creep data by means of master curves
has been widely used. In addition to the'Larson—Miller parameters, other
empirical and semiempirical parameters have been proposed (refs. 2 to 5).
With these parameters and master curves, predictions of rupture life and
creep can often'be made from limited data. A critical evaluation of these
time—compensated parameters is given in reference 6; the advantages and
shortcomings of the method are covered therein.

In reviewing published master curves (refs. 1 and 5) for rupture
life, for minimum creep rate, and for creep strain, employing the Larson-
Miller parameters, a marked similarity of the master curves for a given
material is evident in most instances. This similarity suggests that
the curves are related and that it should be possible to predict one
curve from another or to generalize the results so that a single master
curve will cover the various applications.