Contribución al estudio del comportamiento dinámico de engranajes planetarios en el estado no estacionario en la presencia de fallos
Contribution to the study of the dynamic behavior of planetary gears in nonstationary regimes in presence of defects
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ABSTRACT: The present PhD study is focused on analyzing the dynamic behavior of planetary gear transmissions in non-stationary conditions in presence of defects. The strategy of this thesis is based on building a numerical model which is referred to a test bench composed of a test planetary gear set mounted back to back with reaction gear set which allow the power recirculation.
First of all, modal analysis techniques were studied to characterize the dynamic behavior of the system. a comparative study between three modal analysis techniques was carried out in order to determine the modal properties in different running condition. Stabilization diagram and Modal assurance criterion were used to estimate the obtained modes. Experimental and numerical modes of each technique were compared and discussed. In addition, the effect of load and meshing stiffness variation on the modal parameters were highlighted.
The study of the dynamic behavior of the model corresponding to the test bench was performed initially in stationary conditions where the speed and the torque are constant. Modulation sidebands are highlighted through numerical simulations issued from a three-dimensional model and experimental measurements. Influence of the gravity of carrier on the dynamic response were also investigated taking into account the interaction between meshing gears, the weight of the planet carrier systems. Then, the dynamic behavior under non-stationary excitations such as the variable load, variable speed and run up regimes was investigated. Time frequency analysis was developed to characterize frequency of vibration signals issued from non-stationary operating conditions. Numerical results obtained by the Short Time Fourier Transform are validated through vibration measurements on test bench during operation under these conditions. However, a non linear model of the model taking into account the Hertzian stiffness was developed and studied in non stationary regime presented by the variable load and run up regime.
Finally, the dynamic response of the system in presence of two kinds of defect was analyzed and discussed in stationary and non stationary regimes. Order tracking method was used to identify the defects in run up and variable loading condition for the simulated and experimental determined signals.