Strainrange Partitioning provides unifying framework for characterizing high-temperature, low-cycle, creep-fatigue properties of metals and alloys. Method offers distinct advantage to designers of immediately providing reliable upper and lower bounds on cyclic life for any type of inelastic strain cycle that may be encountered in service

Halford, G. R.

Hirschbere, M. H.

Manson, S. S.

English

NASA Technical Reports Server

December 1973
	 B73-10314 
NASA TECH BRIEF 
Lewis Research Center
	
_4V 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Creep-Fatigue Analysis by Strainrange Partitioning 
.
Strainrange Partitioning is a method for predicting the 
life of structural materials. It is used to analyze and 
predict the onset of low-cycle fatigue failure of metals and 
alloys in structures operating in extreme high-temperature 
environments. Using the approach, a designer can deter-
mine, in advance of service, just how many loading 
applications can be imposed on a part without having it 
fail. A designer can assess the severity of any complex or 
simple service loading cycle and thereby arrive at the most 
efficient design for resisting cyclic failures for the particu-
lar problem at hand. Strainrange Partitioning provides a 
unifying framework for characterizing high-temperature, 
low-cycle, creep-fatigue properties of metals and alloys. 
Systems such as heat engines, combustors, power 
generators, and heat exchangers are susceptible to failures 
due to the interaction of creep and fatigue at high 
temperatures. Current methods of avoiding or anticipating 
these failures are expensive, time consuming and may even 
be unreliable. For these reasons, designers and manu-
facturers are seeking methods of life prediction that are 
less expensive, simpler, and more accurate. Strainrange 
Partitioning offers these very advantages. This approach 
has been demonstrated to be fundamental, versatile, and 
reliable. Yet the approach is simple in concept and is easy 
to apply. To date, this method has been applied to 
laboratory specimen test results on approximately 15 
different alloys with a high degree of success. Strainrange 
Partitioning has been able to encompass the numerous 
anomolies in creep-fatigue behavior that have been re-
ported in the literature. The method also offers the 
distinct advantage to designers of immediately providing 
reliable upper and lower bounds on cyclic life for any 
type of inelastic strain cycle that may be encountered in 
service. Consequently, the Strainrange Partitioning 
approach will be used in the design of high temperature, 
high performance systems, and will be incorporated into 
design handbooks and codes.
Notes: 
1. Further information is available in the following 
reports: 
NASA TM-X-67838 (N71-27945), Creep-Fatigue 
Analysis by Strain-Range Partitioning 
NASA TM-X-68023 (N72-18916), Temperature 
Effects on the Strainrange Partitioning Approach 
for Creep-Fatigue Analysis 
NASA TM-X-68171 (N73-15923), The Challenge 
to Unify Treatment of High-Temperature Fatigue --
A Partisan Proposal Based on Strainrange Parti-
tioning 
Copies may be obtained at cost from: 
Aerospace Research Applications Center 
Indiana University 
400 East Seventh Street 
Bloomington, Indiana 47401 
Telephone: 812.337-7833 
Reference: B73-10314 
2. Specific technical questions may be directed to: 
Technology Utilization Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Reference: B73-10314 
Patent Status: 
NASA has decided not to apply for a patent. 
Source: S.S. Manson, G.R. Halford, 
and M.H. Hirschberg
Lewis Research Center 
(LEW.12072) 
0-
Category 04 
This document was prepared under the sponsorship of the National
	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States
	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States
	 will be free from privately owned rights.
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Creep-fatigue analysis by Strainrange Partitioning

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