In a mechanism (or an agglomeration of closely packed granules), impact
between a pair of bodies induces reactions at points of contact with other
bodies; these reactions prevent overlap or physical interference.
Previously impact on a system of interconnected bodies has been analyzed as
either a sequence of separate collisions or a set of simultaneous
collisions. In general neither of these assumptions gives an accurate
representation of the dynamic behaviour of multi-body systems. Rather, it
is necessary to model the compliance of each contact and consider the
contact forces which develop since it is these forces which prevent
interpenetration. When applied to impact on multi-body systems such as
mechanisms, the impulse-momentum methods used in rigid body dynamics give
but one limit of the range of response - a range that depends on the
distribution of local compliance at each contact between bodies in the
system. An accurate analysis of multi-body system response to impact
generally requires consideration of the time-dependent contact forces in a
wave of reaction that propagates away from the initial site of impact.
