Application of Blocked Force Methodology to an Electrified Beam Axle from a Medium-Duty Truck in Vehicle and in a Dynamometer Test Cell

The recent addition of fully electric powertrains to propulsion system options has increased the relevance of sound and vibration from electric motors and gearboxes. Electrified beam axles require different metrics from conventional beam axles for noise and vibration because they have multiple sources of vibration energy, including an electric motor and a reduction gearbox. Improved metrics are also driven by the stiff suspension connections and lack of significant isolation compared to electric drive units. Blocked force is a good candidate because it can completely characterize the vibration energy transmitted into a receiver and is especially useful because it is theoretically independent of the vehicle-side structure. While the blocked force methodology is not new, its application to beam axles is relatively unexplored in the literature. This paper demonstrates a case study of blocked force measurement of an electrified beam axle with a leaf spring suspension. The axle was tested both in vehicle and in a hemianechoic axle test cell. Measurement setup, including the selection of interface, instrumentation, and impact locations, is discussed. Comparisons between the blocked forces measured in vehicle and in dyno are made. Several key learnings, opportunities for measurement improvement, and ideas for future work are also addressed.