#1.During take-off, the wing of the airplane is actually subjected to a cyclic stress range of 150 MPa at a stress ratio of 0.1. Estimate the mean stress intensity factor, and the initial stress intensity range that are applied to the wing during take-off. You may assume that the estimated initial crack length is 4 mm. Sketch a single fatigue cycle (stress intensity factor versus time) for a cyclic frequency of 10 Hz.