An aluminium plate surface coated with a brittle Al2O3 at 420C using sputter coating techniques to protect the surface from cyclic failure. Find out the fatigue life of the coated aluminium surface at 20C subjected to 200 MPa cyclic stresses. The property of Al & Al2O3 is given in the following table. [10] Property Elastic Modulus, GPa Poisson's ratio Thermal expansion coefficient, m/mK Lattice Parameter (at 420C), nm True facture strain True fracture strength, MPa Fatigue ductility exponent Fatigue strength exponent Al 70 0.35 21 x 10-6 0.5185 1 400 - 0.5 - 0.05 AlO3 360 0.10 1 x 10-6 0.5145 2.86 x 10-3 1080 1 -0.1