DETERMINATION OF KIC SPECIMENS WITH A SHARP HERRINGBONE NOTCH

The determination of fracture toughness K//I//c is extensively used for research purposes and in testing the product quality. These tests are relatively labor consuming and take long, which calls for a search of simpler ways of testing for determining K//I//c. A further improvement of methods for determining fracture toughness is associated with the use of specimens with herringbone notches (SHN) of various shapes. Testing is substantially simplified by the fact that the natural crack is initiated at the tip of a sharp herringbone notch in the initial stage of static loading (eccentric tension or bending) before its critical value is reached. In this paper the authors describe an investigation of the effect of the specimen dimensions on its yielding for the purpose of choosing the geometrical parameters of the specimen which ensure the constancy of the size 1/b(dc/da).