NOMENCLATURE
a
arclength in contact with snow
c
cohesion
c′
apparent cohesion
d
DruckerPrager material cohesion
e
void ratio
E
Young's modulus
E1
tread longitudinal shell modulus
E2
tread lateral shell modulus
Fc
cap failure surface for compactivedilatant failure
Ffoam
foam model failure surface
Fs
shear failure surface
Ft
transitional failure surface
g
flow potential surface for crushable foam model
Gs
flow potential shear surface
Gc
flow potential cap surface
G
shear modulus defining recoverable shear strains
h
snow depth
i
slip
I
moment of inertia
Ii
invariants of normal stress
j
relative slip distance between the wheel and the terrain
Ji
invariants of deviatoric or shear stress
k
constant in equation defining friction as a function of slip distance (eq 26)
K
flow stress ratio (related to shape of yield surface in deviatoric plane)
K0
coefficient of earth pressure
l
beam length
M
slope of the critical state line in the effective stress plane
ncl
normal compression line
csl
critical state line
p
mean (total) normal stress
p′
mean effective normal stress
pa
defines the evolution of the hardening and softening of the cap (location of Drucker
Prager cap along the mean pressure axis)
pb
hydrostatic compression yield stress (DruckerPrager model)
pc
hydrostatic compression strength (foam model)
pc|0
initial value of hydrostatic compressive stress (foam model)
pmax
maximum contact pressure
pt
hydrostatic tensile yield stress
pel
elastic tensile limit
t
q
deviatoric stress
r
tire radius
R
cap eccentricity parameter (controlling the shape of the cap)
Rs
motion resistance force
component of stress deviation (σi p)
si
t
stress deviator parameter, t = q when R = 1
tbeam
thickness of the beam
T
temperature
u
pore water pressure
v
specific volume
vw
wheel speed
vi
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