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Please prioritize answering part (b) - calculations required
Gas turbine engine components can be subdivided into three categories based on their criticality. (a) Provide an example of a component from each category. Use these to briefly describe the difference between the three categories. [8 marks] (b) On integration of the of the Paris crack growth relationship, it can be shown that the number of cycles required to grow a crack from size ao to a1 (the crack propagation life) is: 1 N = ao (CAomym) 2 m – a, (2-7) m where C and m are constants from the Paris expression, Ao is the applied stress range and Y is the geometry factor. A single full component test on a fan disc has shown that the life to first crack is 45030 cycles. Unavoidably, some of the components could contain defects. Using both the single life to first crack test, fracture mechanics and the material / in service data supplied below establish a lifing methodology for the disc. Describe how the method would operate in practice and justify the decisions you take. Assume a scatter factor of 4 for the full component test. Service / Material data for the disc: K1c = 56 MN m-3/2 Y = 2.3 Ag = 390 MN/m2 NDT threshold, ao = 0.3mm m = 2.9 C = 1.42 x 10-11 (MN, m units) [17 marks]