Using the Soft-Soil tire model

Using the Soft-Soil tire model
Elastic-plastic tire-soil contact
13
*
R
f0
1
h
f
h
R 0
0
(27)
Elastic and Plastic deformation
Depending on the soil properties one part of the deformation is elastic and the remaining part is nonirreversible
(plastic deformation). The elastic deformation is calculated with by the soil stiffness C s at the
maximum normal stress max :
(
he
C
m
s
)
(28)
Multi-pass effect
When a tire has passed a certain spot of soil, a second tire will experience different soil properties when
rolling over that spot due to the plastic deformation of the soil by the first tire.
Therefore this Soft Soil tire model stores the elastic and plastic deformation of each tire as a function of
the contact point x,y coordinates. When a tire passes a point with plastic deformation caused by a
previous tire, the normal pressure calculation will account for the plastic deformation history.
Figure 10 explains the mechanism applied in this tire model [8]:
Assume two tires rolling after each other over the same spot of soil. The first tire will have a total
deformation h 1 existing of a plastic part h p1 and an elastic part h e1 . When a second tire passes the same
spot, the soil will first have an elastic deformation from A to B (= h e1 ) and then continue to follow the
normal pressure characteristic to point C. The plastic deformation of the second tire h p2 will be equal to
the total deformation h 2 subtracted with the elastic deformation h e2 .