J. Am. Ceram. Soc.,85
Controlled Precracking of Fracture Mechanics
Specimens Using Contact Stresses
Atsushi Hashimoto* and Desiderio Kovar, Materials Science and Engineering Program
and Department of Mechanical Engineering,
A simple method is proposed for introducing precracks into thin plate, fracture mechanics specimens, i.e. compact tension and double cantilever specimens, using standard testing equipment and without performing complicated machining operations on the specimens. The surface of the sample is first scored to a known length using a scribe and the specimen is then compressed between polymer blocks. Mismatch between the elastic properties of the polymer and specimen results in an in-plane tensile stress in the vicinity of the scratch that causes a crack to initiate from the scratch and propagate through the specimen thickness. Provided that certain conditions are met, the crack arrests without significant growth beyond the initial scratch length. The result is a straight, through-thickness precrack of controllable length. Fracture toughness measurements made on glass specimens precracked using the proposed method are in good agreement with literature values for this material.