Good day!

Would you be so kind helps me understand physical meaning of "shear stress", and "shear strain?"

Mihail

A shear stress, denoted (tau), is defined as a stress which is applied parallel or tangential to a face of a material, as opposed to a normal stress which is applied perpendicularly. In other words, considering that weight is a force, hanging something from a wall creates a shear stress on the wall, since the weight of the object is acting parallel to the wall, as opposed to hanging something from the ceiling which creates a normal stress on the ceiling, since the weight is acting perpendicular to the ceiling.

Shear strain is a strain that acts parallel to the surface of a material that it is acting on. Normal strain, in contrast, acts perpendicular to the surface. There are two ways to interpret shear strain: the average shear strain and the engineering shear strain. The variable used to denote average shear strain is while denotes engineering shear strain.

Consider an infinitesimal rectangle in the xy plane subject to shear strain. The rectangle becomes a parallelogram where is the displacement from the y axis in the x direction and is the displacement from the x axis in the y direction. The average shear strain is

[edit] Definition of engineering shear strain

where

is the angle before deformation and is the angle at that same point after deformation. Therefore describes the total deformation.

Dear Charles!

Thank you for so perfect explanation!

Maybe you can tell me meaning of "shear flow" and "shear layer".

Mihail.

Shear flow is:-

in a solid body, the gradient of a shear stress force through the body; in a fluid, it is the flow induced by such a force gradient - see Viscosity for a fuller treatment.

Shearing layers is a concept coined by architect Frank Duffy which was later elaborated by Stewart Brand in his book How Buildings Learn: What Happens After They're Built (Brand, 1994), and refers to buildings as composed of several layers of change.

thanks a lot!

Merry Christmas and a happy new year!