Static and dynamic analysis of machine drivelines

Fluctuating torque in machine drivelines, which can lead to fatigue failures of driveline components, is caused as much by resonances in the driveline system as by variation in external loading. Drivelines include non-linearities such as backlash and friction, which affect behaviour.Simple mathematical models based on spring, backlash and friction elements have been developed to describe the static torque/deflection behaviour. Experimental measurements on the complete driveline of a mower-conditioner and on its driveline components were used to validate the models.Analysis of torque recorded during field work suggested that a linear dynamic model would be suitable for this machine. A four degree-of-freedom model was developed using classical vibration theory. This model predicted accurately the natural frequencies and mode shapes of the mower-conditioner driveline under sinusoidal excitation from a servo-hydraulic actuator in the laboratory. Frequencies of peak power spectral density of torque during field work were predicted quite well by the model, but with less accuracy than the laboratory test results. Better estimates are needed of stiffness under continuous rotation in the presence of non-linearities.