where:

Txy is shear StressStress is defined as a level of force applied on a sample with a well-defined cross section. (Stress = force/area). Samples having a circular or rectangular cross section can be compressed or stretched. Elastic materials like rubber can be stretched up to 5 to 10 times their original length.stress*
F is the acting force
A is the area on which the force is applied
ϒxy is shear strain
Δx is the displacement of the body
L is the original length

*Txy is an “out-of-diagonal” component of the 3-dimensional shear tensor describing the active component of stress applied in the x direction causing a deformation gamma in the xy direction of the sample.