Derivation of the Force Interaction within Strongly Coupled Systems - Application to Diesel Engine Oil Pumps 2011-01-1531

Due to the increasing focus on noise and vibration for future vehicles, there is a need for a clear definition of the requirements between vehicle manufacturers and auxiliary suppliers. Auxiliary characterisations are also needed as input for structure-borne numerical prediction models. Strongly coupled systems are amongst the most difficult structure-borne noise issues, as the transmitted forces and powers are strongly dependent upon the mobilities of both the vibration source and receiver. The so-called “blocked forces” can be used as intrinsic source descriptions. The challenge is then to design auxiliary test benches perfectly rigid in the frequency range of interest. The current paper is based on the French research program MACOVAM dedicated to the vibro-acoustic characterisation of oil pumps for truck engines. An original test bench was designed to measure quasi-blocked forces over the [150 Hz-2800 Hz] frequency range. Several methods aimed at determining internal forces were tested and compared in terms of practical implementation and result accuracy. An inverse method was found to be the most correlated with direct measurements of internal forces, and easier to implement in case of multiple connections. A specific post-treatment takes the test bench assembly mobilities into account in order to derive blocked forces. Finally, a validated numerical methodology is proposed for the prediction of structure-borne noise induced by the auxiliaries. The application on diesel engine oil pumps will be carried out from test bench numerical validation up to engine response computation using measured forces.