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UBC Theses and Dissertations

Stick-slip friction and rotational vibration under large contact areas and uneven distributed loads Baleri, Mudlagiri


The proposed research is aimed at the analysis of stick-slip frictional phenomenon when large contact areas are involved and, due to the physical structure of the system, high uneven contact loads are generated. The study will look at both mechanistic and tribological aspects of the problem. The main objective of the research is to achieve a better understanding of the phenomenon based on experimental observations and to develop a mathematical representation under realistic conditions. A non-linear finite element model has been developed using ANSYS to obtain an understanding of the contact pressure distribution at the interface of contact of large surfaces due to the applied loads. A mathematical model of this distribution has been derived based on the results of the ANSYS solution. The friction torque acting at the contact surface has then been estimated by integrating elemental friction torque over the entire plate area. The LuGre friction model for the localized contacts has been extended for large contact areas using an integration approach. The simulations have been carried out using Simulink to understand the dynamic behavior of the integrated LuGre model as well as to assess the effect of various system parameters on the stick-slip vibrations. A test rig has been designed and fabricated to re-construct the realistic situations that occur in large robots and excavators for example. The instrumentation, signal processing, data acquisition and analysis have subsequently been carried out. The experiments have been conducted to investigate the effect of various parameters such as total load, loading configuration, speed, and spring stiffness on the stick-slip vibrations. The simulations using proposed integrated LuGre model are found to be in good agreement with the experimental results. The experiments have revealed that with all other parameters being same, the stick-slip vibrations are more likely to occur under concentrated loading as compared to distributed loading for the same total load.

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