Effect of engine mount stiffness on joint integrity and durability of mounts.

Powertrain mounts location and stiffness in vehicle plays very important role in improving vehicle noise and vibration which is caused by engine firing forces and road disturbances. Once locations are finalized based on initial calculation and packaging, then it is very much critical to play with mount stiffness to achieve required NVH level in vehicle. This paper describes the effect of mount stiffness on the bolted joint integrity. Stiffness fine tuning is done to improve vehicle level NVH and various iteration are done with change in stiffness values of A, B and C mounts. When stiffness specs are finalized it is recommended to do aquire road load data on the finalized stiffness mount and check for bolted joint integrity since load signature is varying significantly on mount w.r.t stiffness change. If we change mount stiffness value from 128N/mm to 98N/mm then loads on that particular mount is getting increased from 4500N to 6500N in one of the track testing. This paper clearly indicates that how loads are getting changed w.r.t stiffness change and what is the implication of load change on the surrounding components and how risk can be mitigated by fine tuning mount location and stiffness values.