Fracture toughness of material of plate:
A large thin plate carrying a crack of 70 mm at its centre is subjected to fluctuating stress cycle perpendicular to crack. smax = 70 MPa and smin = 30 MPa. The fracture toughness of material of plate is 1500 MPa .
, where a = half crack length.
The stress at which fracture will occur issmax = 70 N/mm2.
i.e ac = (1500 /(70´1.7726)2= 146.14mm