A PHENOMENOLOGICAL THEORY FOR THE TRANSIENT CREEP OF METALS AT ELEVATED TEMPERATURES
The phenomenological theory previously proposed in NACA Technical Note 4000 for the behavior of metals at elevated temperatures was modified to yield transient creep curves by assuming that the metal consists of two phases, each with its own elasticity and viscosity. The extended theory satisfies the basic requiremerts for a theory of transient creep at elevated tcmperatures: that thc transient creep be closely connected with the subsequert steady creep, and that the apparent exponent of the time in the transient region be permitted wide variations betwecn 0 and 1. From this theory it is possible to construct nondimensional creep curves which extend continuously from the transient region into the steady-state region. The eorresponding family of creep curves for any metal may be obtained from the nondimcnsional family by use of appropriate constants. The constants required are those obtained from steady creep measurements, together with two additional constants which represent the difference between the phases. The transient creep curves resulting from this theory are compared wtth the experimental curves for pure aluminum, gamma iron, lead, and 7075-T6 aluminum alloy; good agreement is found. (auth)
- Research Organization:
- Langley Aeronautical Lab., Langley Field, Va.
- NSA Number:
- NSA-13-013535
- OSTI ID:
- 4259765
- Report Number(s):
- NACA-TN-4396
- Country of Publication:
- United States
- Language:
- English
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