RESEARCH METHODOLOGY AND CHARACTERISTICS OF NORMAL NONLINEAR RESONANT OSCILLATIONS OF THE SYSTEM ” SPRUNG AND UNSPRUNG PARTS OF WHEELED VEHICLES”

Abstract

The authors have discussed the method applicable for the system of sprung-unsprung parts of the vehicle, carrying out vertical oscillations under nonlinear elastic force interactions, which allow evaluating the influence of the elastic characteristics of tires, the suspension system, and road irregularities on the determining parameters of the oscilla-tions of the sprung-unsprung parts. What’s obtained: a) the analytical dependence of natural oscillation frequencies on the system amplitudes and parameters; b) the relationship between the levels of amplitude of the sprung and unsprung parts oscillations, at which an internal resonance occurs; c) the condition for occurrence of the resonance in case of the motor vehicle movement along the road, which is described by the ordered system of inequalities; d) the ratios that set the main parameters of vibrations of the sprung and unsprung parts in case of the resonant and non-resonant vibrations. It is shown that a larger value of the oscillation amplitude of the sprung part corresponds to a larger value of the natural frequency in a suspension system with a progressive law of changes in the elasticity of shock absorbers, and the opposite is true when a regressive law; speaking of shock absorbers and elastic tires with their progressive or regressive power characteristics, a larger value of the oscillation amplitude of the unsprung part corresponds to a larger value of the oscil-lation amplitude of the sprung part, when an internal resonance is possible; for regressive power characteristics of tires and progressive power characteristics of shock absorbers – vice versa; the resonance value of the oscillation amplitude of the unsprung part is higher for the lower speeds of movement with regressive power characteristics of the tires and, on the contrary, – for the progressive power characteristics of tires; the amplitude of the transition through the resonance of the unsprung part takes a larger value for elastic tires with a smaller value of their static deformation and a slower transition to resonance. Keywords: sprung and unsprung parts of the wheeled vehicle, natural frequencies of oscillations, resonant oscillations, internal resonance of the unsprung and sprung parts of the wheeled vehicle.