Using A533, Grade B, Class 1 low-alloy steel (HSST plate 04), a number of standard tests were performed in the laboratory, all at 50°F. Material characterization was established in terms of tension tests on specimens taken from the longitudinal and tranverse directions, and the stress-strain curves were virtually identical. Fracture toughness data were obtained from 36 compact tension specimens of the standard ASTM configuration, ranging in thickness from 0.4 to 4 in. J-integral and equivalent energy approaches were used to interpret fracture toughness from the test data. In spite of the wide range of specimen size, and even though no specimen met ASTM validity requirements, the toughness data were highly consistent.
The tension data were used as the basis for a series of elastic-plastic finite element analyses of a center-cracked plate, under conditions of plane stress and plane strain. In addition to the usual stress and deformation field results, the analyses provided information which include load-deflection curves for a specific gage length, values of the J-integral, and total energy in the specimen. Three center-cracked plate specimens were fabricated from the same block of material as that used in the characterization texts, and were tested in the laboratory (at 50°F) under conditions simulated by the analyses.
Using the fracture toughness data from the compact tension tests in conjunction with the analytical values of J and total energy, preliminary fracture predictions were made for the center-cracked plates. Predictions based on the J-integral and equivalent energy approaches were consistent, but actual specimen performance was considerably tougher. Apparent reasons for the difference between predicted and actual behavior include incompleteness of the analytical model, inability to observe onset of slow crack growth, and less than fully plane strain constraint in the test specimens.