4. A through crack in a thick plate has the initial length of a0=10mm. The crack growth is approximately described by the Paris law with A=5.51012m/ cycle and m=2.5, when K is expressed in MPam. The plate is subjected to the cyclic load with a random distribution of cycles. In every 500 cycles there are approximately 80 cycles with max=180MPa,220 cycles with max=120MPa,140 cycles with max=90MPa and page 2 of 3 MAAE 4102 Engineering Materials: Strength nd Fracture A. Artemev 60 cycles with max=50MPa. All cycles have the stress ratio R=0.1 Estimate the number of cycles to failure. Material properties are: Young's Modulus, E=210GPa, Poisson's ratio, v=0.33, yield strength ys=390MPa, ultimate tensile strength, UTS =485MPa, and KIc=95MPam. Assume that KI=a/2