SYMPOSIA PAPER Published: 01 January 1973
STP49646S

Experimental Verification of Lower Bound KIc

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A method is described for obtaining lower bound KIc values, using compact specimens. The specimens are tested at temperatures for which valid KIc values cannot be obtained according to recommended specimen size requirements (ASTM Test for Plain-Strain Fracture Toughness of Metallic Materials (E 399-72)). This concept has been proposed by Witt and is called the “Equivalent Energy Method.” The procedure can be summarized as follows: 1. Select any point of the linear portion of the load-deflection curve (Point B). Measure the area under the load-deflection curve up to maximum load and divide this area by the area up to Point B. Call the ratio of areas b. 2. Using the load at Point B as PB calculate KBd as follows: KBd=b2PBbd(2bd)1/2ƒ(aw) If the specimen meets the ASTM E 399-72 size requirements, KBd, as calculated above, represents the fracture toughness KIc. Experimental verifications of the Equivalent Energy Concept are also presented. The results show that lower bound fracture toughness values can be obtained with compact specimens, utilizing the method as proposed by Witt. At a given temperature, the lower bound values obtained increase with increasing specimen thickness.

Author Information

Buchalet, C.
Westinghouse Electric Corp., Pittsburgh, Pa.
Mager, T., R.
Westinghouse Electric Corp., Pittsburgh, Pa.
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Details
Developed by Committee: E08
Pages: 281–296
DOI: 10.1520/STP49646S
ISBN-EB: 978-0-8031-8151-9
ISBN-13: 978-0-8031-6660-8