#### Bempel

I have problems with the "Engineering Shear Strain" formulas from the following web site :

http://www.efunda.com/formulae/solid_mechanics/mat_mechanics/strain.cfm

I agree with the formulas and the graph on the left, but I don't with it on the right. On the left graph du/dy and dv/dx are separated. On the right graph (total shear strain) dv/dx and du/dy are put together on the x-axis. One can't simply add the deformation u along the y-axis to the deformation v along the x-axis. One can't change d(something)/dx by d(something)/dy or say its the same. Could anyone give me some explanation on this?

Note that there are some errors on the graphs with x's and y's exchanged.

Could anyone please help me on this? I am working on the subject and I want to understand. If you know some references of literature would be appreciated to

Best regards

Stephane