Page 238 - The Combined Finite-Discrete Element Method

COMBINED FINITE-DISCRETE ELEMENT SYSTEMS 221

y

Direction of
contact force
x
Figure 6.3 Edge to edge contact.

v
A
Figure 6.4 Initial conditions.

Figure 6.5 Motion sequence before the loss of symmetry.

Figure 6.6 Rounding error influence on resolution of contact impact.

Figure 6.7 Motion sequence after the loss of symmetry.

However, the further motion sequence shown in Figure 6.6 clearly shows corner to
corner contact. In the left-hand side of the figure, the bottom triangle has gone under the
impacting triangle. In the right-hand side of the figure, the impacting triangle has just
missed the bottom triangle.
This slight difference in resolution of contact-impact due to the rounding error has
finally resulted in the complete loss of symmetry, as shown in Figure 6.7.
A large multibody system is actually permanently in some sort of bifurcation. Thus,
rounding errors or small differences in initial conditions can influence the behaviour of