# A cubical element is subjected to the following state of stress.

${\sigma}_{x}=100MPa,\phantom{\rule{0ex}{0ex}}{\sigma}_{y}=20MPa,\phantom{\rule{0ex}{0ex}}{\sigma}_{z}=-40MPa,\phantom{\rule{0ex}{0ex}}{\tau}_{xy}={\tau}_{yz}={\tau}_{zx}=0$

Assuming the material to be homogeneous and isotropic, determine the principal shear strains and the octahedral shear strain, If $E=2\times {10}^{5}MPa$ and v= 0.25