The sheet of width W = 0.5 m and thickness b = 15 mm contains a quartercircular crack of radius a. The sheet is loaded in tension, and the stress intensity factor is  as long as a/b a/W P cycles...

The sheet of width
W
= 0.5 m and thickness
b
= 15 mm contains a quartercircular crack of radius a. The sheet is loaded in tension, and the stress intensity factor is
 as long as
a/b
<>a/W
<>P
cycles between 0 and 3 MN. The fracture toughness of the material is 30 MPa‐m^1/2, and its Paris law constants are
A
= 3E‐11 and
n
= 3.7, where crack growth rate is in meters per cycle and stress intensity factor is in MPa‐m^1/2. Determine how many cycles it will take the sheet to fail if the initial crack radius is 0.5 mm and the crack maintains its quarter-circular shape until failure.