NTRS - NASA Technical Reports Server

Back to Results
Statistical summaries of fatigue data for design purposesTwo methods are discussed for constructing a design curve on the safe side of fatigue data. Both the tolerance interval and equivalent prediction interval (EPI) concepts provide such a curve while accounting for both the distribution of the estimators in small samples and the data scatter. The EPI is also useful as a mechanism for providing necessary statistics on S-N data for a full reliability analysis which includes uncertainty in all fatigue design factors. Examples of statistical analyses of the general strain life relationship are presented. The tolerance limit and EPI techniques for defining a design curve are demonstrated. Examples usng WASPALOY B and RQC-100 data demonstrate that a reliability model could be constructed by considering the fatigue strength and fatigue ductility coefficients as two independent random variables. A technique given for establishing the fatigue strength for high cycle lives relies on an extrapolation technique and also accounts for "runners." A reliability model or design value can be specified.
Document ID
Acquisition Source
Legacy CDMS
Document Type
Contractor Report (CR)
Wirsching, P. H.
(Arizona Univ. Tucson, AZ, United States)
Date Acquired
September 4, 2013
Publication Date
July 1, 1983
Publication Information
Publisher: NASA
Subject Category
Structural Mechanics
Report/Patent Number
NAS 1.26:3697
Accession Number
Funding Number(s)
PROJECT: RTOP 505-33-72
Distribution Limits
Work of the US Gov. Public Use Permitted.
No Preview Available