ON STABLE FRACTURES IN A UNIAXIAL STRESS FIELD.
NEW MEXICO UNIV ALBUQUERQUE BUREAU OF ENGINEERING RESEARCH
Pagination or Media Count:
The purpose of this investigation was to produce a stable fracture which satisfied the Irwin-Griffith postulation and to measure the critical strain field in the neighborhood of the fracture tip. By the energy method, four guidelines of experience was obtained. 1 A constant displacement end condition for the plate must be enforced. 2 Fracture must be initiated at low total plate displacement. 3 The plate width should be sufficient to sustain a stable fracture length of the order of 1.0 inch without significant edge effect. Various perturbative effects resulting from the application of the birefringent coating technique to this problem were investigated. The coating thickness and reinforcing effects were compensated by a correction factor. The difficulty of simultaneous fracture of base metal and coating was avoided by applying the coating after fracture. The strain measurement by the birefringent coating method was successfully carried out for the fractured plates. The experimental stress intensity functions were obtained for a number of stable fracture lengths. In general, the experimental data were in agreement with the Inglis solution for large values of isochromatic radius r sub m, but the data were more closely approximated by the Williams solution for small values of r sub m. The experimental stress divergence rate rwas found to be proportional to r sub m to the minus .38 power as compared to the analytical result of r sub m to the minus .50 power.