| Belts are used in automobiles to transmit power from the crankshaft to various accessories on the vehicle, such as the water pump and alternator. These systems, known as front-end accessory drives (FEAD), use a single, wide serpentine belt and a spring-loaded tensioner. FEAD systems are known to exhibit complex dynamic behavior that is attributed to variations in the belt tension and the coupling between spans. In this work, the coupled response and stability of belts is investigated.; The coupling between spans is considered by investigating the free response of multi-span axially moving string and beam joined by an elastic constraint. For certain constraints and system parameters, the string and beam models have similar response characteristics. The beam, however, is shown to exhibit a mode delocalization phenomena, which does not occur in the string model. A wave analysis is performed to identify and explain the observed coupled behavior.; The forced vibration of the nonlinear, coupled transverse and longitudinal motions of an axially moving strip are also presented. In the presence of a 3:1 internal resonance, the transverse modes show two types of unstable motion, one associated with a jump phenomena and the other being quasi-periodic motion. For the transverse/longitudinal vibration with internal resonance, the quasi-periodic motions no longer exist. The affect of the longitudinal motion on the transverse response is also shown to be significant.; The coupled, nonlinear, parametrically excited axially moving strip is also studied. The response of the transverse modes and the transverse/longitudinal system show similar trends. The quantitative difference between the two curves is independent of the amplitude of the tension fluctuations. The parametrically excited transverse/torsional motion shows large response amplitudes for the transverse modes while the torsional motion is highly modulated with small response amplitudes.; An automotive FEAD test stand is used to measure both the transverse and torsional motions of the belt under parametric excitation due to tension fluctuations. Coupled transverse and torsional motion occur, each exhibiting large amplitude responses over a range of speeds. Results for the tensioner reveal that the twisting motion of the belt, even when large, has little affect on the tensioner. |
