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A critical component for an experimental aircraft is made from a high strength aluminium alloy. The component can be represented as a simple thin flat plate which must withstand a maximum working tensile stress of 400 MPa. During flight trials, the component is unexpectedly subjected to slight pitting corrosion, which in turn induces surface cracks at the edges of the component. If Ge and Young's modulus for the component material are 6300 Jm? and 7.2 x 1010 Pa respectively, what is the critical crack length for fast fracture? If routine non-destructive testing can only detect cracks and other flaws that are greater than 1 mm in size, comment on the safety of the component, based on your result for critical crack length.
K. (from given E and Ge values) = 2.1298 x 107 Nm 3/2 :. a (from Kc and oc) = 0.902 mm