ISSN: 1945-7553
CODEN: JTEVAB
Page Count: 12

Fatigue Threshold Regime of a Low Alloy Ferritic Steel under Closure-Free Testing Conditions: Part II—Hysteresis in Near-Threshold Fatigue Crack Propagation: An Experimental Assessment

Vaidya, WV
Metallurgist, Institut für Werkstofforschung, GKSS-Forschungszentrum Geesthacht GmbH, Geesthacht,

(Received 14 May 1991; accepted 10 October 1991)

Abstract

Near-threshold fatigue crack propagation behavior of a high strength steel was investigated in laboratory air under closurefrec testing conditions at R = 0.7 (= R_cff) and at two different K-gradients. Depending on the criterion assumed, the threshold value differed; the criterion of non-propagation gave a lower threshold value than that assumed by the propagation criterion. Nevertheless. the subsequent propagation following a load increase was discontinuous in both cases, and da/dN versus ΔK curves obtained on the some specimen during the K-decreasing and the K-increasing test were not necessarily identical in the threshold regime. This behavior, hysteresis, is analyzed mainly from the experimental viewpoint, and it is shown that hysteresis is not an artifact.

Keywords:
compliance, data analysis, experimental aspects, fatigue crack propagation, ferritic steel, hysteresis, microstructural observations, threshold regime, transient effects

Paper ID: JTE11710J
DOI: 10.1520/JTE11710J
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