Research On Dynamics Of Heavy Vehicle And Road Surface Interaction

ABSTRACT:Nowdays high speed and heavy load are two kinds of main developing trends in highway transportation. Thus vehicle ride comfort, handling stability, safety and road early damage have caused widespread concern. Although researchers have already been aware of the effect of dynamic load on road damage, its role is limited to static load on the basis of experience amendment in actual pavement design. Thereofore the research on vehicle and road surface interaction has important theoretical meaning and engineering application value in optimizing heavy vehicle structure, improving service performance and service life of road.The main goal of this work is to research dynamics of interaction between heavy vehicle and road and to investigate road's early damage by modeling, theoretical analysis, numerical simulation and experimental test. The main research work of this present dissertation is summarized as follows:Firstly, both shock absorber and leaf spring are key components of heavy vehicle suspension. The damping and stiffness characteristics have an important influence on vehicle ride comfort and road friendliness. The damping characteristics of shock absorber are tested under sinusoidal and random displacement excitation. The forve-velocity curves are obtained under different frequencies and different amplitudes. The stiffness curves of leaf springs are obtained through cascaded loading and unloading. Based on testing results, the nonlinear dynamic models of shock absorber and leaf springs are established, respectively.Secondly, two kinds of dynamics models of independent and integral balanced suspension models are proposed. The sprung mass acceleration and the tire dynamic forces for two kinds of balanced suspension and traditional quarter-vehicle model are compared in frequency and time domain, respectively. It is concluded that quarter-vehicle model could be used to evaluate the ride comfort of vehicle, but it indeed has some limitations in evaluating vehicle road friendliness. The sprung mass acceleration and road damage coefficients for balanced suspension are also analyzed under different vehicle design and running parameters.Thirdly, a tri-axle vehicle model with balanced suspension is modeled by considering the nonlinearity of shock absorber and leaf springs. Furthermore, a vehicle-tire-road coupling model is proposed by combing the enveloping FRC (Flexible Roller Contact) tire model and tri-axle vehicle model. The presented mathematic model could restore the interacting process of vehicle-tire-road system. It is expected that these works could supply a new idea for vehicle-road interaction research.Finally, a rigid-flexible coupling model of a heavy vehicle is built based on multi-body dynamics theory. The geometric parameters of the vehicle system, the nonlinear characteristics of shock absorber, the flexibility of leaf springs and the stochastic road surface are precisely described. The dynamic vehicle model is validated by testing data. According to the design of experiment (DOE) method, an orthogonal optimization program for valid vehicle model is presented to study the effect of vehicle parameters on ride comfort and road friendliness. After several virtual experiments and range analysis, the most important influencing factor and its range are screened out. Then a matching scheme is formed to make ride comfort and road friendliness optimization.