A high-strength pressure vessel steel (HY130) has a yield strength (Y.S.) of 1,460 MPa and a KIC of 98 MPa m1/2. Calculate the size of a surface crack that will lead to catastrophic failure at an applied stress of
(a) 1/2 Y.S. and
(b) 2/3 Y.S. (Y = 1) (See Example 8.2)