Development of a new model for the prediction of automotive serpentine belt life

Automotive front-end accessory belt drive systems employ multi-ribbed serpentine belt and are subjected to crankshaft torque fluctuation, component loading and dynamic environments, which will affect the fatigue life of the belt. The onset of catastrophic belt failure occurs in accessory drive systems when the rubber cracks/or internal cords loose their resilience and become brittle. This limits the durability performance of automotive front-end accessory belt drives.;To simulate the stress state between the V-ribbed belt/pulley, two-dimensional and three dimensional finite element models were built in order to study the stress distribution in the ribs of the belt. The results obtained from the finite element (FE) belt model correlates well with the measured strain results which therefore validates the FE belt model and the stresses due to belt pre-tension, power transmission, bending and radial compression are computed using the correlated finite element model.;The fatigue index, b, and the fatigue strength coefficient, 6f, are estimated empirically for the serpentine belt via experimental results. The validity of belt fatigue model is confirmed via additional experimental results obtained from a variety of different accessory drive configuration using different loading profiles. Finally, actual vehicle measured data is used to predict the belt life using this belt fatigue model.;Dynamic analysis of a serpentine belt drive system with friction type automatic tensioner is performed and a closed form analytical solution is found for the first time for the sinusoidal input.;A new fatigue life model for predicting accessory belt lives subjected to various loading is developed in this study. The stress-life approach is employed to create the belt life equation where serpentine belt rib stresses are used as the damage parameter. The multi axial state of stress in the belt rib tip is related to an equivalent uniaxial stress by employing the Sines method and the total mean stresses are derived using the individual mean and the fluctuating stresses as in Sines method.;A sampling technique is employed to obtain discrete simulated load distribution for the components and the belt life distribution is predicted using this method.