SEDL / STP / STP833-EB / STP32580S

On the Use of Compliance for Determining Crack Length in the Inelastic Range

Nicholas, T
Materials Research Engineer, AFWAL Materials Laboratory, (MLLN) Wright-Patterson Air Force Base, Ohio

Ashbaugh, NE
Research Engineers, University of Dayton Research Institute, Dayton, Ohio

Weerasooriya, T
Research Engineers, University of Dayton Research Institute, Dayton, Ohio

Pages: 17    Published: Jan 1984

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Abstract

Compliance measurements were made during creep and fatigue crack growth to establish crack length. During various tests some of the data from several nickel-base superalloys demonstrated a lack of a one-to-one correspondence between crack length and compliance. In particular, decreases in compliance were observed when going from fatigue to creep and when going from low frequency to higher frequency fatigue cycling. On the other hand, no anomalous behavior was observed in ductile copper when loaded to high K values and subsequently unloaded. It is concluded that a probable cause of the anomalous compliance values during transient loading conditions is due to a complex three-dimensional stress state which may be additionally influenced by environmental factors.