The Noise Vibration and Harshness (NVH) characteristics and requirements of vehicles are changing as the automotive manufacturers turn their focus from developing and producing cars propelled by internal combustion engines (ICE) to electrified vehicles. This new strategic orientation enables them to offer products that are more efficient and environmentally friendly. Although electric powertrains have many advantages compared to their established predecessors they also bring new challenges that increase the difficulty of matching the high quality requirements of premium car producers especially regarding NVH.
Electric motors are one of the most important sources of vibrations in electric vehicles. In order to address the new challenges in developing powertrains that match the acoustic comfort expectations of the customers and also shape the development process as efficiently as possible, car manufacturers use numerical simulation methods to identify NVH problems as early in the design process as possible. Numerically describing the dynamic properties of electric motor components such as the stator or rotor is proving to be especially difficult as they contain heterogeneous parts that have viscoelastic orthotropic or transverse isotropic stiffness and damping properties.
In this work, using a dynamic Representative Volume Element (RVE), the homogenized frequency dependent stiffness and damping properties of a stator core are determined. Furthermore, two approaches used in order to model the damping properties of these laminate structures are presented. The presented methods deal with different ways to model damping by modal and complex stiffness approaches. The numerical results are compared to experimental data obtained by means of experimental modal analysis and the applied modeling approaches are validated.
Finally, a model order reduction method is applied to the finite element model in order to further reduce its size. The classic Component Mode Synthesis (CMS) reduction method is enhanced with the possibility of modeling transverse isotropic damping properties. The new approach is validated by comparing it to the full numerical model.