# Shear stress acting on an element

1. Oct 14, 2016

1. The problem statement, all variables and given/known data
When an element of material is subjected to pure shear stress , equlibrium requires that equal shear stress must be developed on four faces of an element .

2. Relevant equations

3. The attempt at a solution
I cant understand the statement . I assume the 'element ' is cubic ... When the element is subjected to pure shear stress , equal shear stress must be developed on all six surfaces of element , right ?

2. Oct 15, 2016

Pure shear stress involves only four planes; e.g., a shear stress $\tau_{xy}$ implies that there is traction on the planes with positive- and negative-facing normal vectors in the $x$ and $y$ directions. There's no normal or shear force applied to the remaining two planes (in this case, the planes with positive- and negative-facing normal vectors in the $z$ direction).