Sensitivity of a vehicle ride to the suspension bushing characteristics
Jorge Ambrósio
The Journal of Mechanical Science and Technology, vol. 23, no. 4, pp.1075-1082, 2009
Abstract : The sensitivity of the ride characteristics of a road vehicle to the mechanical characteristics of the bushings used in
its suspension is discussed here. First, the development and computational implementation, on a multibody dynamics
environment, of a constitutive relation to model bushing elements associated with mechanical joints is presented. Bushings
are made of a rubber type of material, which presents a nonlinear and viscoelastic relationship between the forces
and moments and their corresponding displacements and rotations. Suitable bushing models for vehicle multibody
models must be accurate and computationally efficient, leading to more reliable models. The bushing is modeled in a
multibody code as an arrangement of springs that penalize the motion between the bodies connected. In the methodology
proposed here, a finite element model of the bushing is developed in the framework of a finite element (FE) code
to obtain the curves of displacement/rotation versus force/moment for different loading cases. The basic ingredients of
the multibody model are the same vectors and points relations used to define kinematic constraints in any multibody
formulation. Spherical, cylindrical and revolute bushing joints are developed and implemented in this work, since the
methodology is demonstrated through the ride over bumps, at different speeds, of two multibody models of a road
vehicle: one with perfect kinematic joints, for the suspension sub-systems; the other with bushing joints, riding. Then,
sensitivities of different vehicle kinematic responses to the characteristics of the bushings used in the suspension are
evaluated, by using numerical sensitivities. Based on the sensitivity analysis, indications on how to modify the vehicle
response by modifying the bushing characteristics are drawn.
Keyword : Elastometer models; Kinematic joint modeling; Multibody dynamics; Sensitivity analysis; Vehicle dynamics |