Determination of Fatigue Resistance Characteristics Based on High-Frequency Testing Results Considering Structural and Operational Factors

Abstract

The experimental investigations of the fatigue resistance of various metallic materials were conducted loading in the range of frequencies from a few Hz to 10 kHz with account of the material structure, test temperature, load ratio and availability of stress concentrators. It is shown that the influence of the most process, structural and operational factors on the values of endurance limits manifests itself identically at both low and high loading frequencies. This implies that the main mechanisms of fatigue damage accumulation intrinsic to the particular material remain independent of loading frequency, while deformation rate affects the value of inelastic strains and, consequently, the degree of plastic strain accumulated during a cycle and endurance limit values. The equation is proposed, which describes the material state at the instant of time preceding the fatigue crack growth initiation with account of the cyclic loading frequency as a factor controlling the damage accumulation rate. An experimental verification of the obtained equation showed that difference between the calculated and experimental data on the fatigue resistance is, as a rule, within the experimental data scattering, which confirms the sustainability of the model. The proposed model provides the base for the prediction of the fatigue resistance characteristics, including at large number of cycles, at various frequencies based on high-frequency test results.