The authors performed some studies on the results of surface-notched double tension tests which were carried out on 50kgf/mm^2-class high-tensile ship hull steel, carbon steel for low-temperature pressure vessels of JIS specification, and 9% Ni steel, with the following results. (1) Arresting the brittle crack propagation upon reaching about 0.5 to 0.7W (W: specimen width) in the temperature-gradient surface-notched double tension test produced the same crack propagation-arrest characteristics as in the temperature-gradient double tension test hitherto carried out without the surface notch. (2) The surface-notched double tension test was found to be highly effective in evaluating the brittle crack propagation-arrest characteristics of high-toughness steels like 9% Ni steel.
