Volume 16, Issue 2 (March 1988)
Evaluation of Published Data on Ductile Initiation Fracture Toughness of Low-Alloy Structural Steels
Published data on ductile initiation fracture toughness, namely J-integral (Ji) and crack tip opening displacement (δi), of high-strength low-alloy steels with 275 MPa (40 ksi) minimum yield strength have been compiled along with material and testing parameters. Yield strength (σy) has been chosen as the main parameter for evaluating the compiled data. The compiled Ji and δi data showed a large range of variation at a given strength level. In an attempt to identify the testing parameters that contribute to this variation, the compiled data have been classified into four categories: (1) valid-standard, (2) valid-nonstandard, (3) invalid-standard, and (4) invalid-nonstandard. The critical review of sorted data has revealed that (1) microstructure, (2) testing method, and (3) validity contribute to both the scatter and the behavior of Ji values as a function of yield strength. The differences observed in the behavior of various sets of data are discussed considering the physical process of ductile crack initiation at the crack tip. The correlation between Ji and δi was investigated using linear regression analysis. The slope of the Ji/σy versus δi plot was found to be in the range 1.7 to 2.0.