Drivetrains are a major source of vibration, noise and system failures. Accordingly, a significant amount of time and effort is being invested developing simulation methods in order to better understand and avoid potentially damaging vibrations, even before prototypes are created for testing. The first step in simulating any drivetrain is creating suitable virtual models to investigate particular phenomena. Too much model detail leads to long computation times and difficulties in interpreting results, while too little may fail to include desired effects. Because the various levels of detail available in multi-body simulation (MBS) are practically limitless, a significant amount of attention must be given in order to choose the appropriate modeling elements. In the simplest form an entire drivetrain can be modeled as several rigid masses connected with torsional springs, which is justifiable for fundamental concept analyses. For other analyses, full three dimensional modeling with complex components may be necessary. Higher frequency analyses may even necessitate the inclusion of material bending for achieving accurate results. The various available elements for modeling specific components must be well understood in order that appropriate choices are made. Modeling requirements for the elements commonly used in the simulation of drivetrains will be discussed. For example: bearings, gearwheels, universal and constant velocity joints, frequency and amplitude dependent mounts, flexible components (e.g. shafts and gearbox housings), etc. Once virtual models are available, various analysis methods are applied in order to aid designers in identifying and quantifying potentially damaging vibrations. Again the application and limitation of these methods must be well understood in order to generate meaningful results. The following methods will be compared and discussed: resonance analysis, linear system analysis, run-up Fast Fourier Transformation analysis, order analysis, transfer path analysis and durability analysis. These drivetrain modeling techniques and analysis methods are not limited to any specific field of engineering, but can be applied to an extensive range of engineering disciplines. Analyses applied to virtual models out of the automotive and wind turbine sectors will be shown.
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