Methods for the construction of the diagrams of fatigue crack-growth rate of materials

We study different parameters used for the construction of the diagrams of fatigue crack-growth rate of materials in the force, deformation, and energy approaches and tested for 08kp low-strength steel and 60 high-strength steel. The applicability of the dependences known from the literature for the evaluation of the crack-tip opening displacement and local strain energy at the crack tip is analyzed. It is shown that the range of local strains Δε* and the total range of dissipation of local energy in a loading cycle ΔW _t * specify the fatigue crack-growth rate in the material and that the da / dN−Δε* and da / dN−ΔW _t * diagrams are more sensitive to the structural and mechanical characteristics of the materials than the ordinary da / dN−ΔK diagrams. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 43, No. 4, pp. 31–41, July–August, 2007.