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Master thesis: Influence of Speed and Eccentricity Dependent Bearing Stiffness and Damping on Rotor Vibration

Aircraft engine rotors are supported by rolling element bearings, usually ball and roller bearings.
External damping is provided to rotors through Squeeze Film Dampers (SFD). Moreover, test-rigs
usually employ journal bearings for the driving motor. These three machine elements are in principle
nonlinear with rotor displacement. However, linearization points can be identified, since they usually
work in a linear area. Additionally, linearization helps for the parameter studies in the early design
stages. Their linearization results in speed and bearing eccentricity dependent stiffness and damping
values. In this work, the influence of speed and eccentricity dependent stiffness and damping on the
rotor vibration is to be investigated. The main tasks are listed in the following:

TASKS

  • Introduction to the in-house rotor dynamic software of MTU & MSC Nastran
  • Introduction to the rolling element bearing, squeeze film damper and journal bearing tool of MTU
  • Literature review regarding linearization of nonlinear bearings
  • Identification of necessary steps for linearization of all three machine elements
  • Design and automatization of the complete linearization process
  • Comparison of the results with literature
  • Implementation of bearings with speed and/or eccentricity dependent stiffness and damping coefficients for a simple rotor in MTU’s in-house tool for Eigenfrequency and frequency response analyses
  • Implementation of the above in MSC Nastran and comparison with MTU’s in-house Tool
  • Implementation of the above for a real engine
  • Comparison of the results with those using constant coefficients
  • Identification of eccentricity dependent bearing coefficients for usage in Eigenfrequency analyses by using frequency response results and derivation of a pattern for normal unbalance cases
  • Documentation of the results

REQUIREMENTS

  • Studies in Mechanical, Aerospace Engineering, or comparable with very good grades. Students (m/f/d) in the areas of Applied (Techno-)Mathematics or Physics are also welcome
  • Independent and strong intrinsic motivation
  • Knowledge of Python or comparable programming language and very good knowledge of FEM. Knowledge of FE Software packages (NASTRAN, CalculiX, Abaqus) is an advantage
  • Fluent in English, fluent in German is an advantage

OUR OFFER

  • Insights into practical work in aviation as an innovative, high-tech industry
  • Exciting jobs that carry responsibility and are performed in an atmosphere of team spirit
  • A personally assigned contact and individual support services
  • Flexible working hours and compensatory time off
  • Networking opportunities

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