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Hydrodynamic Lubrication is the culmination of over 20 years close, collaborative work by the five authors and discusses the practical use of the formalization of low pressure lubrication. The work concentrates on the developments to journal and thrust bearings and includes subjects such as: • the dynamic behaviour of plain and tilting-pads • the thermal aspects • the positive and negative effects of non-cyclindricity and shape defects resulting from manufacturing or operation • the effects of inertia • the appearance of Taylor's vortices and of turbulence and their repercussions. The book contains an abundance of test results objectively compared with theoretical conclusions and a chapter on "technical considerations" to ensure that draft mechanisms will work satisfactorily under the imposed conditions. Hydrodynamic Lubrication is an essential reference book for future and practising engineers who want to put hydrodynamic and hydrostatic journal bearings and thrust bearings into operation under conditions of total safety.
A fourbar linkage test-bed has been designed, built, and instrumented to measure the effects of dynamic balancing, vibration isolation and system stiffness on the dynamic forces and torques generated at the pivot bearings and on the ground plane. The system was initially designed and modelled using the Aries solids modelling package, the ADAMS dynamic simulation package, program Dynafour, and ANSYS finite element analysis software. The theoretical dynamic forces and accelerations at particular points on the links were calculated in advance, based on the system kinematics and the mass properties of all moving members as defined by the Aries solids modeller. The device was built using accurate NC machining equipment. The finished assembly is instrumented with piezoelectric accelerometers and force transducers. The design allows three bivalent modalities of operation, unbalanced/dynamically balanced, stiff/compliant torque coupling, stiff/compliant motor mounts, all of which may be intermixed in various combinations. The assembly was run under all combinations of modalities and the dynamic forces and accelerations measured and transformed to the frequency domain. The results were subjected to an analysis of variance and compared to those of the theoretical model. The differences were statistically significant in all but a few cases. As expected, the compliances and clearances in the physical model created significantly larger dynamic accelerations, torques and forces on the bearings than was predicted theoretically by a rigid dynamic model. These increased forces will affect bearing and journal wear. This paper reports on the details of this experimental/theoretical study and draws some conclusions relevant to making design decisions applicable to similar mechanical devices. Work is continuing on the theoretical modelling of the system's nonlinearities as well as on measurement of the effects of bearing clearances on the vibration and modal behavior of the physical system.
The effect of internal clearance on radially loaded deepgroove ball and cylindrical roller bearing load distribution and fatigue life was determined for four clearance groups defined in the bearing standards. The analysis was extended to negative clearance (interference) conditions to produce a curve of life factor versus internal clearance. Rolling-element loads can be optimized and bearing life maximized for a small negative operating clearance. Life declines gradually with positive clearance and rapidly with increasing negative clearance. Relationships were found between bearing life and internal clearance as a function of ball or roller diameter, adjusted for load. Results are presented as life factors for radially loaded bearings independent of bearing size or applied load. In addition, a modified Stribeck Equation is presented that relates the maximum rolling-element load to internal bearing clearance.