Fatigue-crack growth behavior in the superelastic and shape-memory alloy nitinol |
| |
Authors: | A L McKelvey R O Ritchie |
| |
Affiliation: | (1) Materials Science Department, Ford Research Laboratory, 48121-2053 Dearborn, MI;(2) Department of Materials Science and Engineering, University of California, 94720-1760 Berkeley, CA |
| |
Abstract: | This article presents a study of fatigue-crack propagation behavior in Nitinol a 50Ni-50Ti (at. pct) superelastic/shape-memory
alloy, with particular emphasis on the effect of the stress-induced martensitic transformation on crack-growth resistance.
Specifically, fatigue-crack growth was characterized in stable austenite (at 120°C), superelastic austenite (at 37°C), and
martensite (at—65°C and—196°C). In general, fatigue-crack growth resistance was found to increase with decreasing temperature,
such that fatigue thresholds were higher and crack-growth rates slower in martensite compared to stable austenite and superelastic
austenite. Of note was the observation that the stress-induced transformation of the superelastic austenite structure, which
occurs readily at 37°C during uniaxial tensile testing, could be suppressed during fatigue-crack propagation by the tensile
hydrostatic stress state ahead of a crack tip in plane strain; this effect, however, was not seen in thinner specimens, where
the constraint was relaxed due to prevailing plane-stress conditions.
A.L. McKELVEY, formerly Graduate Student, Department of Materials Science and Mineral Engineering, University of California |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|