Does pure shear stress exist?

Does pure shear stress exist?

1. Frictional force applied on a surface:

  A frictional force is often taken to be a horizontal resistance offered by the surface on a interacting surface. let us observe that frictional force arises only when there is unevenness in the contacting surfaces and a horizontal force is along with normal force is applied on the contact surface.  Thus, it is essentially the  sum of all horizontal components of normal contact forces between the uneven boundaries in the horizontal direction of motion of the surfaces in contact.

2. Shear force inside a solid body and atomic structure of matter: 

The atomic structure of a material is typically in the form of a truss and it complexity depends arrangement of atoms of a material. Size of atoms are almost that of the center to center distance between atoms.

Let us imagine a solid mass comprising of repetitions of several such above units. A pure shear essentially requires one layer of atoms to be completely in plane with another layer. This process requires fusing of two atoms or significant change in the crystalline structure both of which are not observed in any mechanical process. It is highly prohibited however small dimensions of the atoms may be. 

3. Viscous drag of a moving fluid on a solid surface:

Fluids have the property of creating inter molecular bonds upon contact with other compatible molecules. This is why fluids can be broken into segments and combined easily, unlike solids when broken cannot be combined easily. These inter molecular bonds are stronger in viscous fluids compared to non viscous fluids. When viscous fluids come in contact with the solid surface, fluid molecules adjoining the surface make a bond with the solid molecules of the surface. It is also evident that the bonds formed between solids and viscous fluid molecules are stronger the bonds between fluid molecules. 

Using the arguments above about the atomic theory of matter, we can derive the similar conclusions here too.

Conclusions:

 A pure shear force on a plane never exist and a plane can only carry at the most a inclined traction force. That means if a pure shear force has to exists, its magnitude must be zero. This can reason out  why layers of non-viscous fluids like water can be assumed to slip of off without any resistance.