A single crystal of a metal is oriented for a tensile test such that its slip plane normal makes an angle of 64.9° with the tensile axis. Three possible slip directions make angles of 30°, 48°, and 78° with the same tensile axis.
(a) Which of these three slip directions is most favored?
(b) If plastic deformation begins at a tensile stress of 1.1 MPa (159.5 psi), determine the critical resolved shear stress for this metal.