SEDL / STP / STP995V1-EB / STP26768S

Evaluation of the Ct Parameter for Characterizing Creep Crack Growth Rate in the Transient Regime

Bassani, JL
Associate professor, University of Pennsylvania, Philadelphia, PA

Hawk, DE
Graduate research assistantresearch,

Saxena, A
Professor, Schools of Materials Engineering,,

Pages: 20    Published: Jan 1988

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Abstract

An in-depth evaluation of the Ct parameter, which has been proposed for characterizing the creep crack growth behavior under small-scale-creep (transient) to extensive creep conditions, is conducted. The evaluation includes a thorough examination of the assumptions made in the definition of Ct, an experimental evaluation, and a finite-element analysis of a compact specimen used in an actual creep crack growth experiment.

The experimental correlations between da/dt and Ct are extremely encouraging. Ct is interpreted as the stress-power (or energy rate) release rate during crack extension. Under extensive creep conditions, Ct therefore equals C^*, which is given in terms of a path-independent integral as well as the stress-power release rate. Under small-scale creep, Ct is shown to characterize the rate of growth of the creep zone. More finite-element analyses and experiments under highly transient conditions are recommended for completing the understanding of the creep crack growth behavior in this regime.