where and are components depending on the elastic and plastic deformations, respectively.
Experiment was conducted by using steels with various sizes of microstructures were produced by laboratory
scale vacuum melting and rolling. The ferrite grain sizes and cementite particle thickness was measured bycombinations of a SEM observation, an EBSD analysis and an image analysis. Tensile tests using circumferential
notched round bar specimens were then conducted. Distributions of cementite particle crack lengths were measured for various strain and stress conditions. A nucleation of cementite cracking should be quantitated basedon a stochastic framework because of its
uncertainties such as distribution, shape, orientation and so on. The measured distributions of cementite particle thickness and crack length were approximated by introducing a distribution function considering upper limit. Eventually, the probability of nucleation of cementite cracking
was formulated as a function of cementite particle thickness and the internal stress of the cementite particle