A material is subjected to two mutually perpendicular direct stresses of 80 MN/mZ tensile and 50 MN/mZ compressive, together with a shear stress of 30 MN/mZ. The shear couple acting on planes carrying the 80 MN/m2 stress is clockwise in effect. Calculate:
magnitude and nature of the principal stresses;
magnitude of the maximum shear stresses in the plane of the given stress system;
direction of the planes on which these stresses act.