Thermo-mechanical Modeling of Angular Contact Ball-Bearings in High Speed Machine Tool Spindles

Zahedi, Ali | 2009

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 39121 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Movahhedy, Mohammad Reza
  7. Abstract:
  8. Machining in its general concept forms the major part of manufacturing processes regarding time and cost. Therefore any progress in machining techniques would be well beneficial. High speed machining is one of the recent concepts in machining technology which has attracted much attention and effort. But high speed spindles as the main part of high speed machines, have been notorious for their lack of reliability and sudden failure which originates mostly from thermal problems. In order to ensure reliable operation of spindles it is necessary to predict thermo-mechanical behavior of machine-tool spindles. The major sources of heat in a spindle are angular contact ball bearings (the most commonly used types of bearings in machine tools), friction force of environment air and rotor/stator in motorized spindles. Heat generation in angular contact ball bearings occurs by three important phenomena: Load related, Viscosity related and Spin related heat generation. It is impossible to establish an analytical model for thermal behavior of a spindle-bearing system without analyzing it mechanically, since the mechanical and thermal characteristics of the system have mutual effects on each other. In this research a thermal-mechanical model is presented for the dynamic response of high speed spindles. Compatible mechanical models for bearing and spindle are coupled with their thermal counterparts. Mechanical model consists of arbitrary loading conditions such as high speed loading, external loads, initial/thermal preload, etc. Thermal model includes heat generation, heat transfer and heat removal within bearings and spindle shaft and housing. Spindle housing and shaft are treated as timoshenko beam elements with 6 Degrees of freedom (3 linear displacements 2 rotational displacements and 1 Temperature). Bearings are modeled as two node elements with 5 displacements and a thermal load component at each node. Thermal and structural mutual interactions of both spindle shaft/housing and bearings are characterized through thermal expansion and rate of heat generation/transfer. Components are combined to form a Finite Element model for thermo-mechanical analysis of spindle-bearing systems
  9. Keywords:
  10. Angular Contact Ball Bearing ; Dynamic Response ; High Speed Spindle ; Thermally Induced Preload ; Coupled Thermo-Mechanical Behaviour

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