An iron bar with the dimensions shown below is being used as a structural support member, underwater in the presence of HCl. Corrosion occurs only on the top surface (marked T in the figure below), and the corrosion current measured on this surface is 1.58 × 10^–2 amperes. This structural member is inspected periodically using ultrasound, and the smallest internal crack that can cause failure is 6 mm (you may assume there are no surface cracks). The fracture toughness of the iron is 41 MPa-m½. The tensile force applied to this member is 1,750 kN in the direction shown in the figure. How long can this member remain in service before it needs to be replaced (i.e., before it fails due to fast fracture)?

50 cm .T 10 cm F 5 cm