The steel plate shown has a central 40 mm crack which is normal to the direction of the applied load (P) of 217 kN. Material tests indicate that its Mode 1 Fracture Toughness is 25 MPa/vm. The thickness of the plate is 15 mm. Determine the critical length in mm of the crack. 60 mm m1 40 mm Plate thickness, t = 15 mm P