Continuous damage parameter calculation under thermo-mechanical random loading

The paper presents a method on how the mean stress effect on fatigue damage can be taken into account under an arbitrary low cycle thermo-mechanical loading. From known stress, elastoplastic strain and temperature histories the cycle amplitudes and cycle mean values are extracted and the damage parameter is computed. In contrast to the existing methods the proposed method enables continuous damage parameter computation without the need of waiting for the cycles to close. The limitations of the standardized damage parameters are thus surpassed. The damage parameters derived initially for closed and isothermal cycles assuming that the elastoplastic stress–strain response follows the Masing and memory rules can now be used to take the mean stress effect into account under an arbitrary low cycle thermo-mechanical loading. The method includes:
• stress and elastoplastic strain history transformation into the corresponding amplitude and mean values;
• stress and elastoplastic strain amplitude and mean value transformation into the damage parameter amplitude history;
• damage parameter amplitude history transformation into the damage parameter history.

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