Substructuring Approach in Interior Noise Refinement of a Vehicle

Increase in the customers' sensitivity for acceptable vibration and noise in a vehicle has prompted automobile majors to address NVH issues during design stage. This paper presents the efficient use of computational FE models for prediction and optimization of Utility Vehicle incab noise during product development process. Isolation by powertrain mounts and body mounts plays a very significant role in incab noise and tactile vibration characteristics of a vehicle. Simulations can help in optimization of stiffness of powertrain mounts and body mounts. This will significantly reduce time and cost associated with physical refinement during later stages of the product development cycle when prototypes are available. But larger numbers of degrees of freedom in full vehicle FE model is a hurdle in terms of solution time and hence slow iterations. To overcome this, substructuring method is followed, allowing focus on the connection between different subsystems and substantial reduction in solution time due to FRF/modal representation of the large size subsystems. This approach does not require solving full FE models for quick isolation optimization iterations. FE model of full vehicle assembly is built and incab noise is predicted using measured powertrain excitations as input forces applied at powertrain mounting brackets. Substructuring technique is used for representation of individual subsystems of full vehicle assembly. Transfer Path Analysis is used to find dominant paths contributing to incab noise. Further optimization to improve incab noise is done based on the TPA results. This study also helped in understanding the individual contribution of input excitation forces, isolation and structural resonances in structure-borne incab noise.