Interrelation and kinetics of matersals fatigue damage under "soft" and "rigid" loading modes https://doi.org/10.33108/visnyk_tntu2017.04.035
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Abstract
In the article the calculating estimation of fatigue damage and plasto-elastic stress-strain state (SSS) kinetics of steels under the “rigid” cyclic loading modes using the ultimate exhaustion of cyclic plasticity (UECP) model is presented. To do this the previously developed method of fatigue damage summation, which
allows to calculate the kinetics of fatigue damage under irregular cyclic loading, was used. The difference in the accumulation of fatigue damage and the kinetics of elastic-plastic SSS for two “rigid” cyclic loading modes (total and inelastic strains control loadings) are shown on the example of two materials: cyclically hardening steel 45 and cyclically softening steel 1Х2М. Besides, calculations with help of the UECP model show, that for the materials with cyclic inelastic strain instability during cyclic loading fatigue damage summation rate is significantly different as compared with the same obtained by the linear summation hypothesis. The results
presented can be used for calculating lifetime estimation of structural elements operating under “rigid” loading modes with a higher accuracy as compared with the use of both stabilized values of inelastic strains and well-known fatigue damage summation hypotheses. This is due to the fact, that the proposed calculative UECP model describes the difference in fatigue damage accumulation under variable cyclic load amplitudes for the materials with different kinetics of inelastic strains. In its turn, it makes possible to substantiate theoretically the necessity of taking into account the inelastic strain kinetics peculiarities under the “rigid” loading modes and to describe the difference and nonlinear nature of fatigue damage accumulation under these loading modes for the specified groups of materials.
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