Nevertheless, the calculated shear stress according to equation 4 is only suitable for the
evaluation of the stresses in the elastic range. The plastic stress obtained from the shear stress-shear
strain curve is therefore larger than the real stress. Furthermore, in the case that there is a large
amount of plastic deformation involved, the length of the specimen is considerably changed, which
can result in the superposition of the longitudinal stresses on the torsional shear stresses.