SEDL / STP / STP631-EB / STP35544S

Determination of R-Curves for Structural Materials Using Nonlinear Mechanics Methods

McCabe, DE
Senior engineer, Westinghouse Electric Corporation, Research and Development, Pittsburgh, Pa.

Pages: 22    Published: Jan 1977

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Abstract

The crack line wedge loaded method of test, originally intended for R-curve determination of ultrahigh strength sheet materials is now being used to evaluate the toughness of low-strength, high-toughness steels. The testing technique and equipment used is described in detail. Use is made of an elastic return slope concept on specimens under dominant plastic conditions to determine the extent of slowstable crack extension. A crack-tip opening displacement (CTOD) approach, incorporating plastic hinge modeling, is used to determine KR values. Also, a JR approximation technique is introduced for comparison to KR determined by the CTOD approach. R-curves typical of structural grades of steel are presented and examples of instability condition predictions are cited.