Abstract
The heights of bending fracture surface of WC-10mass%Co cemented carbide were measured by using OM (optical microscope) and AFM (atomic force microscope) in order to estimate the one-dimensional roughness of the surface (RO and RA, respectively) and then the microscopic fracture surface area (Sif) and Sif/Smf term in our proposed equation of σm= ?? KICSmf1/2 (Smf ; macroscopic fracture surface area of one test piece, σm ; flexural strength, ?? ; shape factor including the ratio of Sif or true fracture surface area (Sif) to Smf, KIC; fracture toughness). Next, the value of γ+P (formation energy of fracture surface, γ; specific surface energy, P; specific plastic deformation work) in the prior equation of Vσm2/18E=(γ+P)Sif+Ek (V; volume of specimen, on which stress operates, E; Young's modulus, Ek; kinetic energy of flying fragments) was evaluated The results obtained were as follows;
1)The RO and RA were 1.27 and 1.43, respectively, and thus, ?? and Sif/Smf were calculated to be 317mm2 and 3.30, respectively.
2)The value of γ+P was estimated to be 6.7×10-4J/mm2.
3)The physical rationality of the equation of σm= ?? KICSmf1/2 should be examined furthermore by investigating the correctness of this value of γ+P or Sif and also the dissipatoin energy by vibration accompanied by crack propagation.
