Modelling of the vibrational behavior of housing plates filled with fibrous material

Abstract: Silencers are used in vehicles to reduce the noise in the engine system. However,silencers themselves may produce break-out noise due to the interactionwith the exhaust gas ow and structure. In this Master thesis project, thenumerical simulation of vibrational behavior of housing plates of silencers isdeveloped.The housing plate is composed of two steel plates and a brous materiallayer. Measurement results show that the brous material has good dampingeect to decrease the vibration and radiated sound of steel plates. Steel platesare connected by spot welding. Modeling of spot welds can improve themodal assurance criterion between simulation and measurements. Interfacedamping is introduced into the simulation models to simulate the contacteect between two steel plates so that the simulated amplitude can have agood agreement with measurement result.Several numerical models of brous material are investigated. The Mikimodel is not chosen for the nal result due to the limit of range of frequencies.The rigid frame model can simulate the sound absorption but is unfeasible forthe simulation of vibration. The limp frame model can simulate the vibrationof light glass wool but cannot simulate the vibration of heavy glass wool.Finally, the Biot-Allard model which is a poro-elastic model is investigatedfor the nal result. The simulation results show good agreement with themeasurement result.