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Experimental Verification of Lower Bound Values Utilizing the Equivalent Energy Concept
A method is described for obtaining lower bound values, using compact specimens. The specimens are tested at temperatures for which valid 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 calculate as follows: If the specimen meets the ASTM E 399-72 size requirements, , as calculated above, represents the fracture toughness . 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.
fracture properties, pressure vessels, temperature, nuclear reactors, safety
Senior engineer, Westinghouse Electric Corp., Pittsburgh, Pa.
Mager, T. R.
Fellow engineer, Westinghouse Electric Corp., Pittsburgh, Pa.