Kovrov State Technological Academy, Russia

Liquid is considered as a molecular system, consist of two structures: ordered elements - elementary cells and unordered array of molecules, between which is installed dynamic balance. At time of existence of separate molecule in the cell (time of settled lives) much more time of findings of molecule in randomly condition. Force, acting on the molecule in the cell, at the shift its for positions of balance, is defined on the base of potential Lennard-Jons with averaging on quick fluctuations of molecules of cell near the position of balance and on possible angular displacements. At presence of small, for a time of settled lives, shift between layers dependency between force acting on the molecule and value of its displacing from the position of balance is taken single-line. Under greater velocity gradients this condition is broken and force acting on the molecule reaches limiting values.

These concepts allow to define a shift viscosity factor through the factor of springiness shift of liquid, time of settled lives of molecule and average distance between liquid layer; to motivate existence of limiting tangent efforts at the shift in simple liquids and define their value, as well as condition of achievement of limiting tangent efforts.