Show that the variation in flow stress for tensile testpieces lying in the 1 - 2 plane with their axes inclined at 0ta the 1- direction is given by when a is defined from eq(l 1.4b). Hence show that...

Show that the variation in flow stress for tensile testpieces lying in the 1 - 2 plane with their axes inclined at 0ta the 1- direction is given by

when a is defined from eq(l 1.4b). Hence show that the condition for a maximum or minimum yield stress is given by