MS23.2 - Vibro-Acoustics

Efforts to create lightweight automotive components often result in structures that are more flexible. The use of lightweight gearbox housings for mass-reduction introduces the challenge of an increased dynamic response of the thin housing panels, resulting in higher structure-borne noise. The sound radiation from such lightweight housings can be mitigated using some stiffening measures on the flexible panels. The focus of this paper is to study the stiffening effect of a hexagonal rib pattern on the dynamic response of a gearbox housing. In a Finite Element Method (FEM) study, a simplified model of a gearbox housing is evaluated for its modal properties and equivalent radiated power (ERP) response to bearing-seat excitations. The gearbox housing model is then treated with a hexagonal rib pattern and changes to the modal behaviour and the ERP response are investigated.

The present work is aimed to propose a multi-parameter feedback control method combined with couple stress elasticity to model piezoelectric micro plate coupled systems. The proposed methodology can be used to design controllers for tuning vibration and wave propagation properties of micro scale plates based on coupled piezoelectric sensors and actuators. Specifically, we use a three-parameter relationship that describes the voltage gain within the sensor-to-actuator circuit involving multiple dependence based on mass, damping and stiffness. Consequently, effect of these parameters can be simulated either independently or collectively so as to obtain the optimal control strategy with respect to the required vibroacoustic properties. Meanwhile, since micro plates are involved, the inherent microstructure effects must be accounted for. Hence, the modified couple stress elasto-dynamics is applied and the micro plate model is discretised with a four-node quadrilateral non-conforming element that offers nodal compatibility with high-order theories of elasticity. Based on the proposed numerical methodology, we investigated the feedback control parametrisation for a reference micro plate coupled system which presents significant microstructure effects. Our analysis allowed characterisation of the three control parameters based on their individual effects, and revealed that their combined effect cannot be predicted by considering direct superposition of their individual behaviours. Therefore, the proposed computational methodology provides a convenient solution for the choice and parametrisation of the feedback controller leading to tunable band gap properties of micro scale plate structures.

Sandwich structures are encountered in numerous applications ranging from automotive and aerospace industry, to bridge construction. However, the design of these structures is a cumbersome task due to two reasons. Firstly, the performance of the sandwich configurations is both dependent on the acoustic and structural transmission path in the core, leading to a coupled vibro-acoustic problem. Secondly, the structures must comply with contradicting mass, noise and stiffness requirements. More specifically, the sandwich configurations need to be as light as possible to comply with strict environmental regulations, while they need to achieve good vibro-acoustic performance to obey restrictive noise regulations. On top of that, a restriction on the static stiffness performance of the structures is present in most applications. To facilitate this multi-functional and multi-physical design problem, optimization routines are important enablers. While extensive research is executed on the material and (structural) size optimization of both the panels and the core of the sandwich configuration, the systematic topological design of the vibro-acoustic core is yet to be explored. Therefore, in this work, a topology optimization framework is presented for the design of sandwich configuration cores to achieve extraordinary performance characteristics while considering the vibro-acoustic coupling in the core during the optimization. More specifically, the design domain of the optimization consists of a unit cell which is infinitely repeated in the in-plane direction. This design domain is optimized to maximize the corresponding sound transmission loss of the infinite periodic structure while the mass and structural stiffness are constrained with user-defined inputs. Novel cores are presented while the trade-off between the different conflicting requirements is investigated.