Two time domain models for fatigue life prediction under multiaxial random vibrations

Two time domain models for fatigue life prediction under multiaxial random vibrations are developed on the basis of the critical plane approach. Firstly, the stress power spectral density matrix of each node at the notch root of the test specimen is obtained by the random vibration analysis with finite element method, and the stress time-histories are generated from the stress power spectral density matrix by the time domain randomization approach. Then, the fatigue life of each node is predicted based on the damage on the critical plane, where the cumulative damage value is the greatest. The minimum fatigue life of all nodes at the notch root is considered as the fatigue life of the test specimen. Finally, the proposed models are validated by the multiaxial random vibration fatigue test with the 6061-T4 aluminum alloy. The results show that the predicted fatigue lives and predicted crack orientation angles are in good agreement with the experimental fatigue lives and experimentally observed crack orientation angles, respectively.