| Summary: | This project has been sponsored by QinetiQ Limited (QinetiQ); whose aim it is to
model the dynamics of a prototype high-speed military tracked vehicle. Specifically
their objective is to describe the mechanism by which force inputs are transmitted
from the ground to the vehicle’s hull.
Many track running gear components are steel and can be modelled as simple lumped
masses or as linear springs without internal damping. These present no difficulty to
the modeller. However tracked vehicle running gear also has nonlinear components
that require more detailed descriptions. Models for two rubber components, the road
wheel tyre and track link bush, and a model for the suspensions rotary damper, are
developed here. These three components all have highly nonlinear dynamic responses.
Rubber component nonlinearities are caused by the materials nonlinear elastic and
viscoelastic characteristics. Stiffness is amplitude dependent and the material exhibits
a significant amount of internal damping, which is predominantly Coulombic in
nature but also relaxes overtime. In this work, a novel method for measuring the
elastic and viscoelastic response of Carbon Black Filled Natural Rubber components
has been devised and a ‘general purpose’ mathematical model developed that
describes the materials response and is suited to use in multibody dynamic analysis
software.
The vehicle’s suspension rotary damper model describes three viscous flow regimes
(laminar, turbulent and pressure relief), as a continuous curved response that relates
angular velocity to damping torque. Hysteresis due to the compression of entrapped
gas, compliance of the dampers structure and compression of damper oil is described by a single non-parametric equation. Friction is considered negligible and is omitted
from the model.
All components are modelled using MSC.ADAMS TM multibody dynamic analysis
software. The models are shown to be easily implemented and computationally
robust. QinetiQ’s requirement for ‘practical’ track running gear component models
has been met.
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