NVH Validation of a Dual Clutch Transmission for Clonk

Examensarbete för masterexamen
Master Thesis
Sound and vibration (MPSOV), MSc
Yilmaz, Emrah
Xiong, Shaohai
A transmission housing is built like a big "bell" that is made to keep shafts and gears in place and keep them lubricated under operating loads. Being a big aluminum chunk with thin walls could attain some interesting sound and vibration properties. To reduce tonal noise and vibrations generated under operating loads is high priority for today’s automotive manufacturers. The cars that use combustion engine usually mask most of the transmission noise, and the driver is not particularly affected. However, the electric engines are very silent which results in the driver mostly hearing different transmission noises like gear whine, rattling, clonk, shifting noise and bearing noise. This thesis is aimed to investigate sound and vibration properties of clonk in a dual clutch transmission. To simplify the complex clonk phenomena that happens in an actual DCT, a simplified impulse force is used as an input force to evaluate vibration and sound properties. Using five different simulation methods with four different software, the DCT finite element model is analyzed to calculate sound and vibrations generated from the impulse load. The objective of simulation is to get a good understanding of the transmission NVH behaviour under transient loads within operating frequency range so that countermeasures can be applied to reduce or dampen the resonance peaks. Measurements in the form of impact measurements have been performed in the anechoic chamber at the Applied Acoustics division of Chalmers University of Technology. The test setup contains impact measurement equipment with two accelerometers and two microphones. The measurement data acquired from the equipment has been used to validate and correlate with the simulation results, so that simulation methods are validated for sound and vibration properties. In conclusion, the simulation results differ in the high frequency range while keeping close correlation in the lower frequencies (around 1 kHz), this can be the consequence of the hammer impact force and location of excitation in the measurement is not possible to excite all high frequencies, thus, the data used to compare at the high frequency range are insuffcient. For future work, the validated FE models can be used for locating the most radiated surfaces on the transmission under operating loads, and the transmission housing can be improved by making the radiated surface stiffer or make use of damping layers.
Building Futures , Akustik , Building Futures , Acoustics
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