4. From the torsion test graph, determine the following (write the equations used and show your solution on the graph): a. The Max. Shear Stress- (5 points) b. Shear Stress at Proportional Limit (use .2% shear strain and show your answer on the graph too)- c. Modulus of Rigidity= d. If the shaft diameter is 12 mm, what is the maximum torque? 140 120 100 Torsion Stress, M Pa 80 60 40 20 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 Shear Strain (%) Fig. 3. Torsion stress and shear strain diagram