steinberg-lund
rho0 reference density g0 ya initial shear modulus, athermal flow stress a b pressure and temperature dependence of shear modulus beta n eps0 ystarmax work hardening gamma0 amelt tm0 melt t0 reference temperature (usually 300 K) c1 c2 Tact yp rate-dependence ytmin minimum yt, e.g. 1.0e-8