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A flat steel plate of 20 mm width and 4 mm thickness has a 4 mm diameter centre hole drilled through its thickness, as shown in Figure 4. The ultimate tensile strength is 1200 MPa and the surface finish is machined. (a) If the plate is simply supported and subjected to a fully reversed bending load, F =300 N, at its mid-span as shown by Figure 4( a) , estimate the factor of safety with respect to eventual fatigue failure. (10 Marks) (b) If the plate is subjected to a constant axial load, P=5kN, and a fully reversed bending load, F=300 N, at its mid-span as shown by Figure 4(b), estimate the factor of safety with respect to eventual fatigue failure. (10 Marks) (Total 20 Marks) Figure 4: Flat steel plate containing a central hole under load (all units are given in mm).