Title

HIGH TEMPERATURE ELASTIC‐PLASTIC SMALL CRACK GROWTH BEHAVIOR IN A NICKEL‐BASE SUPERALLOY

Document Type

Article

Date of Original Version

1-1-1994

Abstract

Abstract— An experimental study of the elastic‐plastic fatigue behavior of small surface cracks in Alloy 718 at 650°C was conducted under conditions of total strain control. During cycling, the crack growth was continuously monitored using a direct current potential drop technique while the influence of crack closure was monitored using a laser interferometry technique measuring the crack mouth opening displacement. The crack tip plastic zone size was also measured using a post‐test delta phase decoration technique. Results show that the growth rates of the small cracks correlate well with long crack LEFM data when using an appropriate elastic‐plastic driving force parameter. The anomalous crack growth rates observed in some experiments were found to be experimental transients dominated by the crack initiation fracture and do not represent an intrinsic behavior of Alloy 718. No contribution to the anomalous small crack growth could be attributed to either crack closure or enhanced crack tip plasticity. Copyright © 1994, Wiley Blackwell. All rights reserved

Publication Title

Fatigue & Fracture of Engineering Materials & Structures

Volume

17

Issue

5

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