Scientia Iranica
Volume:30 Issue: 4, Jul-Aug 2023

In this study, a new model has been developed for fretting fatigue crack initiation life prediction based on the slip amplitude as a macroscopic feature of the contact interfaces. The main difference between the presented model and many other fretting fatigue life prediction models is the focus on the fretting specific characteristics. In this model, a damage parameter is combined with a damage severity factor to obtain a new fretting fatigue crack initiation life prediction parameter. To investigate the accuracy of this new parameter, a series of fretting fatigue tests have been conducted. Also, crack initiation life data from the literature were added to enhance parameter accuracy investigation. It is shown that the effective slip amplitude is an unbiased geometric-independent parameter in fretting fatigue crack initiation life prediction. Also, comparing prediction results from the effective slip amplitude with those of Smith-Watson-Topper and Ruiz parameters showed that the new parameter can outperform available fretting fatigue life prediction parameters.

In the present study, an accurate model is used for analyzing an asymmetric shaft with misalignment and under unbalance forces in rotating coordinates verified by developing an experimental test.The asymmetric rotor modeled by the Timoshenko beam theory is coupled to a motor.The differential equations of motion are discretized by Rayleigh-Ritz method and derived from Hamilton's principle. Thereafter, According to the results, a frequency range is detected in which,resonance and instability will occur. The dynamic behavior of the rotor is investigated near the boundary of the instability region. Various parameters, including unbalanced and misalignment induced forces, and the dimensions of the cross-section of the shaft are taken into account.Finally,vibration responses of the system and their Fast Fourier Transform (FFT) are presented graphically to determine the frequencies of the harmonic responses. It is concluded that the asymmetry of the shaft and misalignment fault severely affect the dynamic response of the rotor.Moreover, the accuracy of the results is increased by applying the Timoshenko beam theory.By developing an experimental test for the rotor system connected to an electric motor with misalignment fault, verifying this model has been done.The experimental results obviously obtained the unstable operating area as acquired by the differential equations of motion.