SEDL / STP / STP668-EB / STP35841S

Minimum Specimen Size for the Application of Linear-Elastic Fracture Mechanics

Munz, D
Division head, Deutsche Forschungs- und Versuchsanstalt fur Luft- und Raumfahrt, Cologne, FR

Pages: 20    Published: Jan 1979

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Abstract

The minimum thickness and the minimum ligaent width for the determination of plane-strain fracture toughness with linear-elastic methods can be considerably smaller than given by the ASTM Test for Plane-Strain Fracture Toughness of Metallic Materials (E 399-74). For the ligament width, the factor 2.5 in the size requirement equation can be replaced at least by 1, possibly by 0.4. The size dependence of KQ determined with the 5 percent secant method is due to plasticity at the crack tip and to the existence of a rising plane-strain crack growth resistance curve. With a variable secant, adjusted to the specimen width, it is possible to determine size-independent fracture toughness values.