  Simple homogeneous shear flows of frictionless, deformable particles are
studied by particle simulations at large shear rates and for differently soft,
deformable particles. The particle stiffness sets a time-scale that can be used
to scale the physical quantities; thus the dimensionless shear rate, i.e. the
inertial number (inversely proportional to pressure), can alternatively be
expressed as inversely proportional to the square root of the particle
stiffness. Asymptotic scaling relations for the field variables pressure, shear
stress and granular temperature are inferred from simulations in both fluid and
solid regimes, corresponding to unjammed and jammed conditions. Then the limit
cases are merged to unique constitutive relations that cover also the
transition zone in proximity of jamming. By exploiting the diverging behavior
of the scaling laws at the jamming density, we arrive at continuous and
differentiable phenomenological constitutive relations for the stresses and the
granular temperature as functions of the volume fraction, shear rate, particle
stiffness and distance from jamming. In contrast to steady shear flows of hard
particles the (shear) stress ratio does not collapse as a function of the
inertial number, indicating the need for an additional control parameter. In
the range of particle stiffnesses investigated, in the solid regime, only the
pressure is rate independent, whereas the shear stress exhibits a slight shear
rate- and stiffness-dependency.
