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Question 1 (20 Marks Total) a) Two strain gauges are placed on the centre of a steel plate (E = 200GN/m² and v= 0.3) at 30° to the known directions of the Principal Stresses. The measured values of strain in these gauges were 455 ue and -32 ue respectively. Calculate: 1) Maximum and Minimum Principal Strains at the point (using Mohr's Strain circle) (5 marks) 2) Maximum and Minimum Principal Stress at the point (assume plane stress) (3 marks) 3) Calculate the Von Mises Equivalent Stress at the point where the strain gauge is attached to the plate. If oy for steel is 400MN/m2, will yielding occur at this point? (3 marks) 4) If the Fracture Toughness (Kic) of the steel plate is 50MPavm, calculate the length of the maximum allowable crack perpendicular to the maximum Principal Stress (Assume a small crack in an infinitely wide plate)? (3 marks) b) A steel bolt of 0.004m² cross sectional area is subjected to a static tensile mean load of 168kN. What value of reversed fatigue load will produce failure in 10' cycles? The yield strength is 344MN/m² and the stress to produce failure at 10' cycles at zero mean stress is 276MN/m² (6 Marks)