By means of dynamic Monte Carlo simulation of bulk lattice polymers in Couette shear flow

it was demonstrated that in addition to velocity gradient the constant driving forces acting as the activation aspect of shear stresses can also raise polymer deformation. Moreover

enhancing driving forces in a flow without any velocity gradient can reproduce non-Newtonian fluid behaviors of long-chain polymers. The simulations of Poiseuille shear flow with a gradient of shear stresses show that

the velocity gradient dominates small deformation in the flow layers of low shear stresses

while the shear stress dominates large deformation in the flow layers of high shear stresses. This result implies that the stress-induced deformation could be mainly responsible for the occurrence of non-Newtonian fluid behaviors of real polymers at high shear rates.