Prediction of Crack Constant in Smooth Materials

Summary

A formula $\Delta \;{\text{K}}_{\text{th}} = \Delta \;\sigma _{\text{e}} \sqrt {\pi a_0 {\text{Y}}\left( a \right)}$ is deduced in this paper based on the energy transfer relations in the materials under cyclic stresses. From this formula, a crack constant which exists in smooth materials can be predicted.

In the formula, both the threshold stress intensity factor Δ K_th and the fatigue limit Δ σ_e are the constants for given material in given condition, a_o is also a constant for given material in given condition. The dimension of a_o is a length. The above formula may be deduced from crack initialing process and a_o can be called as a crack constant in the smooth materials.