SEDL / STP / STP1171-EB / STP18029S

An Experimental Study to Determine the Limits of CTOD Controlled Crack Growth

Gordon, JR
Manager, Edison Welding Institute, Columbus, OH

Jones, RL
Head, United Kingdom Admiralty Research Establishment, Poole, Dorset

Challenger, NV
Research engineer, The Welding Institute, Cambridge,

Pages: 19    Published: Jan 1993

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Abstract

This paper presents the results of an experimental program to study size and geometry effects in CTOD R-curves. The results were obtained from room temperature unloading compliance R-curve tests on different-sized single-edge-notch-bend (SENB) specimens made from Ti-3Al-2.5V alloy, HY100 steel, and nickel-aluminum-bronze (NAB). The crack growth resistance was measured in terms of conventional CTOD, δ⁰ (i.e., as defined in BS 5762), CTOD corrected for crack growth, δ^R, and CTOD derived using a double clip gage arrangement, δ^dc. It was found that all the CTOD R-curves exhibited upswings after crack extensions corresponding to approximately 15% of the initial uncracked ligament. Based on the results obtained in this study, it is postulated that the crack growth limit for CTOD controlled crack growth in R-curves is 15% of the initial uncracked ligament. This condition alone, however, is not sufficient to guarantee size/geometry independent results. It is also necessary to have the same level of specimen constraint.