Dynamic Model of a Planetary Gearbox considering Sun Gear Crack with Effects of Clearance for Carrier, Planet and Sun Gear Bearings

  • Author / Creator
    Chen, Xianhua
  • Planetary gearbox systems are widely used in many heavy machineries such as mining machines, wind turbines, and automobiles. Although well designed, planetary gearboxes may suffer various failure modes, such as sun-gear tooth crack, due to the harsh working environment such as high torque. Gear tooth crack can affect the vibration responses of planetary gearboxes. Furthermore, bearings in planetary gearboxes have clearance, which can also affect the vibration responses.
    Dynamic modeling is often used to simulate the vibration responses of planetary gearboxes. Many researchers have studied the effects of different levels of sun-gear tooth crack on the planetary gear set. Considerable literatures focused on bearing clearance in a planetary gearbox. However, very few studies considered sun-gear tooth crack and bearing clearance together to analyse their combined effect on vibration characteristics of planetary gearboxes.
    According to the real planetary gear set located in the Reliability Research Lab at the University of Alberta, this thesis simulates the planetary gearbox through dynamic modeling with sun-gear tooth crack and bearing clearance to discuss their comprehensive effects. This thesis assumes that, the crack width is unchanging as the length increases, and the bearing clearance is a constant. As a result, four key works in this thesis are listed as follows:
    (1) The planetary gearbox focused in this thesis has three kinds of bearings, including sun-gear, planet-gear, and carrier bearings, because the ring gear is fixed. Furthermore, 8 cases for the combinations of bearing clearance are discussed in this thesis.
    (2) The sun-gear crack level considered ranges from 0% to 50%, with an increment of 0.5%. The tooth crack can reduce the mesh stiffness. The impulse caused by the tooth crack can be found in the time domain, and the magnitude of gear mesh frequency is decreased as the tooth crack grows.
    (3) Three kinds of bearing clearances are considered. It is found that the planet-gear bearing clearance increases by 1.6% of the highest value of the displacement sum for the planetary gearbox, which means that the planet-gear bearing clearance could be neglected. However, the effects of carrier and sun-gear bearing clearances cannot be ignored, because the differences can be obviously found in both the time and the frequency domains after considering carrier or sun-gear bearing clearance.
    The simulation results have revealed that if the bearing clearance is much smaller than the displacement of its corresponding gear, the clearance does not affect much the dynamic response of this gear. Otherwise, the clearance can increase the displacement of its corresponding gear and also change the dynamic response of other gears. In conclusion, researchers may choose to focus only on the clearance which is bigger than the displacement of its corresponding gear in simulations.

  • Subjects / Keywords
  • Graduation date
    Fall 2020
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
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