Summary

Notch tensile tests have been carried out on six grades of a high-strength martensitic steel at different hardness levels to investigate the effects of stress triaxiality at the net section and uniaxial tensile properties on fracture behavior. Cylindrical V-notched specimens were used in these tests with the notch-root radius, rho, ranging from 0.03-1.4 mm, and with the value of the net-to-gross diameter ratio being 0.6. The notch strength ratio (NSR) was found to attain its maximum value at rho = 0.38 mm. The test results were used successfully for screening the fracture toughness behavior of the martensitic steel by extrapolating the corresponding rho-NSR curve to rho = 0.0. Further, finite element computation of the average stress triaxiality factor ((eta;) over bar) enabled the development of a model more accurate than that reported in the literature for estimating NSR for a ductile material as a function of (eta;) over bar and its uniaxial tensile properties