[a] Give a definition for the following: (i) Shear stress. (ii) Stress concentration factor in torsion. [b] Sketch annotated idealised stress-strain diagrams for: (i) Strain-hardening material. (ii) Elastic-perfectly plastic material. [c] A stepped shaft shown in Fig Q2.1 has d =40mm and D=60 mm and loaded with torques T=1100Nm. If the allowable shear stress at the stress concentration is 120MPa, what is the smallest radius Rmin that may be used for the fillet