are positive in tension and shear stresses  are positive when they tend to produce counterclockwise rotation of the material

Angle  is between the x-axis and the normal to the section

b.)These equations are valid for any material, whether it behaves linearly or nonlinearly, elastically or inelastically.

a)      Maximum Normal and Shear Stresses

i)        The maximum normal Stress occurs at  and is 

ii)       and the largest negative value when