On Contact Mechanisms and Mechanical Transmission Performance

Abstract: This thesis consists of four papers, which treat the modelling of a spur gear set and a disc brake, and the interaction between the machine elements. Features of the performance are studied in relation to the initial stated assumptions. Initially, a method for analysing the influence of profile errors upon load-sharing capabilities and mesh stiffness of spur gears was proposed. The contacts between mating gear teeth were identified in the deformed state. In addition, artificial neural networks were employed for system identification. The discussion was focused upon the dependency between the contact ratio and the load in addition to the influence of profile and pitch errors. Experimental data validated the reliability of the approach. Following, a non-linear damping model for shaft torsional vibration studies was proposed and experimentally validated. The experiments showed that the internal shaft damping was highly non-linear. The damping tended to be not only stiffness related but also noticeably depended on the type of material. Friction induced noise due to the interaction of the mating teeth of a spur gear set was studied. For the shaft bearings, a non-linear damping model based upon the coefficient of restitution describing the interaction between the rolling elements and the inner- and outer race of the bearing was proposed. The non-linear support bearing model created a relation between the bearing stiffness in the path of contact of the mating teeth and the movement of the gears perpendicular to the path of contact. The presence of friction had its greatest effect upon the bearing force in the path of contact of the mating gear teeth at low angular velocities, and at mesh frequencies close to the natural frequency of the vibration perpendicular to the path of contact. Finally, the influence of the interaction between the disc of a floating disc brake assembly and connecting members was studied. In the initial process of the experimental research, high drag torque was acquired without applying force to the pads. The spline profile and the nave width were proven to have little effect upon drag, whilst the position on which the caliper was mounted had a considerable influence. Both the analytical study and the experimental measurements showed a strong correlation between the caliper position and the drag torque.

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