Experimental Observation of Crack Velocity and Crack Front Shape Effects in Double-Torsion Fracture Mechanics Tests

The double-torsion test configuration has been used to obtain crack growth information for a variety of materials. Recently critical reviews have suggested that certain assumptions used in the interpretation of double-torsion data are of questionable validity.

This paper presents experimental data for crack growth in glass specimens loaded in the double-torsion test configuration. The constant displacement rate technique was used to propagate cracks and velocity was measured continuously by superimposing a tuned-frequency sonic signal during cracking. The crack velocity profile as a function of position along the crack front was determined. The crack velocity at the tensile surface was measured as a function of crack length at constant load and the crack front shape was observed for various crack lengths.