Practice Exercises: Q1 If the principal stresses at a point in an elastic material are 120 MN/m², tensile; 180 MN/m², tensile and 75 MN/m², compressive, find the stress at the limit of proportionality expected in a simple tensile test assuming: Maximum shear stress theory Maximum shear strain energy theory Maximum principal strain theory. Ans: (225; 230.9 & 166.8 MN/m²) Q2 A horizontal shaft of 75 mm diameter projects from a bearing, and in addition to the torque transmitted, the shaft carries a vertical load of 8 kN at 300mm from the bearing. If the safe stress for the material as determined in a simple test is 135 MN/m², Find the safe torque to which the shaft may be subjected using the criterion of the maximum shearing stress. Ans: (6.3 kNm.) Other practice exercises are in the Theories of Elastic Failure hand out (Self assessment exercise No. 1). Attempt Q1 to Q3.