Development of CAE Methodology to Predict Rattle (BSR) Inside Passenger Cabin

With overall development in acoustic properties of materials and electric vehicles set to replace conventional IC engine vehicles, Squeak and rattle are fast becoming area of interest for automotive manufacturers. Squeak and rattle are unwanted noises in vehicle cabin. Till now to eliminate squeak and rattle, conventional find and fix approach has been used. With increasing competition among automobile manufacturers and effort to reduce the development time for a vehicle, it has become necessary to find S&R at initial stages of development. In this investigation an effort has been made to develop the process which can predict the rattle occurrence in the initial phase of development without actually going for physical test setup. A test fixture along with sample plates of polypropylene is mounted on shaker machine and test is conducted on vibration shaker machine. A initial gap of 2 mm is maintained between the two sample plates. For test input excitation of 0.8*G and sine sweep of 0-65 Hz has been used. From test, Acceleration Vs Time data is plotted. Fast Fourier Transform is applied to convert time domain data into frequency domain. Modal frequency response analysis is conducted using Optistruct as a solver and its Acceleration Vs Frequency data is plotted. Acceleration Vs Frequency data for test and simulation is compared for validation purpose. Using simulation Displacement Vs frequency data has been plotted. Peak displacement is compared with the predefined gap between the plates. It is assumed that if this displacement is greater than the predefined gap rattle is deemed to occur. This method is developed for small prototype and could be used for real parts where rattle may occur.