Modal analysis tire model: Straight ribbed tread
wheel's centerpoint while allowing the tire to freely
rotate about its axis due to friction, simulating a
The ribbed tread tire model is also a modal analy-
towed wheel. The contact is frictionless during the
sis tire model. Construction is similar to the smooth
loading process, and friction is added during the roll-
tread model, with the carcass composed of four-node
ing step. Variations of the analysis include a static or
reduced-integration shell elements and the treadcap
dynamic analysis procedure during rolling and
constructed of linear, hybrid continuum elements
changes in the convergence controls.
with constant pressure. The major difference is the
The towing phase of the dynamic analysis is bro-
four grooves across the width of the tire created by
ken into two steps. The first is to accelerate the tire
omitting sections of the tread continuum elements
from rest to 1 m/s at a constant acceleration of 1 m/s2
(Fig. 44). The wheel is represented by one mass ele-
ment and one rotary inertia element located at the
for one second (traversing 500 mm). The second step
centerpoint. Details for the smooth and ribbed tread
continues to roll the tire at a constant velocity of 1
models are given in Table 9.
m/s for two more seconds (2000 mm). For all cases
The analysis is completed in eleven steps, com-
the analyses converge for a while but eventually
prising inflation, bead seating, lowering to the road
reach a point where the tire stops moving by taking
surface, and vertical loading. The loading occurs in
increasingly smaller time steps due to convergence
eight steps of alternating loose and tight convergence
difficulties. The problem occurs when the shell is
control. Inflation is handled similarly. The creation
subjected to simultaneous distortion and rotation as
and seating of the bead are accomplished using multi-
the rotation angle approaches 360. This is a bug in
point constraints on the first five rings of nodes clos-
the ABAQUS shell element that will be corrected in
est to the wheel rim. An additional step translates the
future versions (Bug Report v58_2449).
Figure 44. Modal analysis tire model with ribbed tread.
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