The Impact of Rib Geometry for Electric Drive Units on the Radiated Sound
Ladda ner
Typ
Examensarbete för masterexamen
Master's Thesis
Master's Thesis
Program
Mobility engineering (MPMOB), MSc
Publicerad
2024
Författare
Malm, Oskar
Wurzinger, Jakob
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
In recent years, the automotive industry has been moving towards electrification of
vehicles. One of the most essential parts of electric vehicles are the electric drive
units or EDUs, which convert electrical energy into mechanical energy that drive the
wheels. An EDU typically consists of several parts, such as an electric motor, gearbox,
and differential, which are encapsulated in an aluminum housing. The housing
has ribs, that can increase the stiffness or casting quality of the housing. These
design requirements are to fulfill the crash safety requirements, as well as noise,
vibration, and harshness (NVH) requirements in terms of structure born noise. The
combination of these requirements, can result in ribs which has be observed to in
some cases, produce unwanted airborne sound.
To investigate how the rib geometry affect the sound radiated from ribs, a number
geometry of variations was performed on four different base models. This includes
curvature of the outer edge, dimensions (area), angles, etc. These variations were
then simulated by meshing the CAD models in ANSA, calculating the nodal displacement
of the surface nodes in NASTRAN using a velocity boundary condition,
and mapping the displacements to the air using an acoustic mesh in Actran. The
simulations were performed for frequencies between 100 Hz and 6 kHz. Finally, the
radiated power, radiation efficiency, and mean square velocity was saved from the
simulations and analyzed for each geometrical variation.
The first bending mode was found to have a large impact on the radiated sound and
has a strong connection to the bending stiffness of the rib. The peak mean square
velocity always occurs at the first bending mode however, the radiation efficiency
does not show any general pattern and is therefore difficult to predict. From the
simulations, it could be concluded that the area of the rib has the largest impact on
the radiated power, which is a clear indication to design as small ribs as possible.
It could also be shown that for some ribs, it is beneficial in terms of reducing the
radiated power, to add a small curvature to the outer edge. A relationship between
the dimensions of the ribs and the thickness of the rib was also found, where some
thickness increases or decreases the radiated power for ribs with same dimensions.
Finally, two adjacent ribs can interact to increase the radiated power significantly
for some distances or angle between the ribs.
Beskrivning
Ämne/nyckelord
Acoustic simulations , Actran , Electric driveline , Electric drive unit , Radiation efficiency , Ribbed structures , Structural vibrations and sound radiation