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The procedure for selecting a flexible coupling to suppress driveline torsional vibration from the engine of an off-highway vehicle or stationary industrial unit with a remotely mounted driven unit is widely studied and documented. However, the successful selection of a torsionally flexible coupling in an off-highway vehicle or stationary industrial unit to suppress engine vibration can create new vibration and performance problems in the driveline and driven unit. This paper presents the unintended consequences of utilizing a torsionally flexible coupling, provides descriptive solutions to the unintended consequences and methods to avoid them.

A phenomenon exists in diesel or compression ignition engine powertrains with torsionally flexible couplings where the powertrain sometimes cannot accelerate through a torsional resonance such as during engine start-up. This phenomenon is sometimes referred to as resonance stall, resonance hang-up, or a jackhammer start. The current theory is that the hysteretic damping of an elastomeric coupling is dissipating input energy from the engine, thereby prohibiting the system from accelerating through the resonance. This theory comes about because the elastomeric coupling, with its hysteretic damping, heats up during resonance and is obviously dissipating energy. By conducting a theoretical study of the energy balances of vibration for a powertrain model and by carefully considering field observations, this paper will show that energy dissipated by the torsionally flexible coupling does not come at the expense of the mean or working torque that was input by the engine.

Abrasive blasting and chemical etching processes are often performed on titanium substrates to improve the adhesion performance of paints, coatings, and adhesives. Abrasive blasting and chemical etching processes alter the physical metallurgy of surfaces so they can produce varied and uncertain effects on the fatigue life of the substrate. The fatigue life of titanium subjected to various blasting intensities and etching has been determined and statistically analyzed. The results of this work indicate that, for titanium alloys, increased aluminum oxide abrasive blasting intensities decrease fatigue life and that chemical etching also decreases fatigue life.

This work presents theory for a passive vibration isolation component for which the effective stiffness changes with the frequency of steady-state operation. The effective stiffness can be passively adjusted, or tuned, to be a minimum at a particular frequency, thereby reducing transmitted vibratory forces at or near that frequency. The new suspension component offers performance similar to a lowly-damped, long-inertia-track hydraulic mount but with fewer components and with no fluid. Prototypes of the new suspension component have been built and tested. The results demonstrate that the new suspension component isolates vibratory forces for a relatively wide frequency range.