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This paper describes the development and testing of a Dynamic Vibration Absorber to reduce frame beaming vibration in a highway tractor. Frame beaming occurs when the first vertical bending mode of the frame is excited by road or wheel-end inputs. It is primarily a problem for driver comfort. Up until now, few options were available to resolve this problem. The paper will review the phenomenon, design factors affecting a vehicle's sensitivity to frame beaming, and the principles of Dynamic Vibration Absorbers (AKA Tuned Mass Dampers). Finally, the paper will describe simulation and testing that led to the development of an effective vibration absorber as a field fix.

Analysis of commercial vehicles presents some special challenges: Many variations of the basic configuration exist. A complete model of a vehicle could easily have over 500,000 degrees of freedom. Response is desired for multiple road types, speeds, or other excitations. To reduce model complexity, Kenworth assembles Finite Element models of complete vehicle from a library of substructures and subassemblies. Substructures are reduced representations of components that retain the global mass and stiffness properties. To simulate multiple excitation cases quickly, a frequency domain approach is used. Frequency response functions generated by the FE model are combined with measured road auto- and cross-spectra. The response is weighted for human sensitivity per ISO 2631-1. Tuning of parameters such as stiffness or damping is performed quickly using system synthesis.