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In this paper, a 1-D refined driveline model in AMESIM was built up, for a P2.5 topology PHEV. The model includes detailed engine, damper, dual clutch transmission, differential, motor, half-shaft, wheel, body, suspension, powertrain mounting and powertrain rigid body, The objective of the simulation is to predict torsional vibration induced vehicle NVH response under different driving scenarios. Firstly, the torsional vibration modes were predicted, and the critical modes were identified. This enabled a good understanding of modal alignment, identification of countermeasures and provide feedback to other engineering teams in the early stages of vehicle development.

As a common means for reducing vibration and noise for automobiles, damping material is usually employed in the vehicle body, typically on the floor, the dashboard and the top roof. With the growing demand of fuel economy, light weighting, as well as NVH comfort, the optimization of the damping pads has become a topic of increasing importance. In numerical simulation, the traditional methods generally make use of the modal strain energy of the metal sheet as the main indicator for making layout choice for the damping pads. These methods are generally not able to take into account the specific location and amplitude of the structural-borne excitations, e.g. road noise or engine excitation. Therefore the optimization is not performed according the vehicle’s real working condition. Furthermore, the traditional methods do not depend on the accurate properties of the damping material. In this paper, a novel optimization method based on energy analysis is presented.

The Statistical Energy Analysis (SEA) method has been shown to be a powerful predictive tool of structural-acoustic design. However, there are many difficulties when the method is applied to an engine structure. It is because 1) the engine structure is so complicated that both the internal and coupling loss factors have to be determined in situ by measurements and 2) the general matrix inversion to calculate the loss factors, with the power injection method, can not simply be used as it produces many negative and unreliable results. The problems are attacked with several new approaches, which include using the equivalent mass, the selective geometric averaging, the consistency and reciprocity relationships, the back estimation technique and the coupling damping. Finally, an experimental validation is done. It shows that the obtained SEA model generally can predict the vibration tendency of the engine structure when damping and isolation treatments are applied.