Problem 3 (33 points) A wide plate has a center crack with initial length a; = 0.01 m. The fatigue crack growth rate is given by the Paris equation: da dN = C(AK) = C(F AS ) m where m = 2, C = 9.0 10-11 m/[MPam]/cycle and da is in units of m/cycle dN . The geometry factor F can be approximated as F = 1. In a lab test, the plate is subjected to a 30-cycle repeating sequence of loading. Each of the 30-cycle sequence consists of: 10 cycles with (Smax=200 MPa and Smint = 0 MPa), followed by 8 cycles with (Smax2=170 MPa and Smin2 = 0 MPa), followed by 12 cycles with (Smax3 = 110 MPa and Smin3 = 0 MPa)) This loading sequence repeats and repeats, until the testing is stopped at the instant when the cycle count has reached N = 300,000 cycles. Determine the crack size a when the testing is stopped. AS