抄録
In the previous study, the present authors have theoretically derived the equation of σm=φ⋅KIC⋅Smf1/2 for the fracture of general hard materials, where σm is the flexural strength, g is the shape factor which can be theoretically expressed as V-1/2⋅ψ, V is the volume of the stressed portion of the specimen and φ is the factor which is constant for the same hard materials, KIC is the fracture toughness and Smf is the total macroscopic area of fracture surface. In this study, the σm, the number of fragments (Nf), Smf and KIC were measured for three kinds of specimens of WC-l0mass%Co low carbon two phase cemented carbide which have different cross sections and spans, in order to investigate whether the effect of V (240, 360, 640mm3) on the gradient of σm-Smf1/2 regression line is in accordance with one theoretically deduced from the equation.
The results obtained were as follows; (1) Both Nf and Smr increased with increasing σm irrespective of V. (2) Both Nf and Smf at a given σm were larger for larger cross section and larger span, i.e., larger V. (3) A strong linear correlation was held between σm and Smf1/2 irrespective of V. (4) The ratio of the gradients of the σm-Smf1/2 regression lines for each two kinds of specimens coincided well with those of V-1/2⋅KIC or V-1/2 as theoretically expected, indicating that the above equation is valid and the value of φ is nearly the same, irrespective of V.
