SEDL / STP / STP527-EB / STP34705S

R-Curve Determination Using a Crack-Line-Wedge-Loaded (CLWL) Specimen

McCabe, DE
Senior research metallurgist and principal research associate, Research and Technology Center, Armco Steel Corp., Middletown, Ohio

Heyer, RH
Senior research metallurgist and principal research associate, Research and Technology Center, Armco Steel Corp., Middletown, Ohio

Pages: 19    Published: Jan 1973

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Abstract

A procedure is described for determining crack-growth-resistance curves, R-curves, using crack-line-wedge-loaded (CLWL) specimens. In testing high-strength sheets, a compliance procedure has been used to determine the applied load, and the effective crack length is taken as the visible crack length plus the Irwin plastic zone correction. For lower strength, higher toughness sheets and light plates, the effective crack length is determined by a double compliance technique. For these materials the ry = 1/2π × (K/σ^YS)² plastic zone radius was found to overcorrect the crack length.

Currently a plastic hinge model is being investigated as a means of extending R-curve determinations well into the plastic deformation range.

A comparison of R-curves determined by CLWL specimens and by center-cracked tension specimens of high-strength sheets shows quite good agreement. There is little information of this type on the tougher materials. Present work is directed at R-curve determinations on low-alloy, high-toughness light-plate material.