need help on problems 2 and 3

2. A plate of width 1.5 m and length 3.0 m is required to support a tensile force in the 2.8-m direction of 5.0 MN. Inspection procedures will detect only through-thickness edge cracks larger than 2.7 mm. The two Ti-6AL-4V alloys in Table 5-1 are being considered for this application, for which the safety factor must be 1.4 and minimum weight is important. Which alloy should be used? 3. A steel ship deck plate is 20 mm thick and 10 m wide. It is loaded with a nominal uniaxial tensile stress of 40 MPa. It is operated below its ductile-to-brittle transition temperature with Kic equal to 25.3 MPa If a 50-mm-long central transverse crack is present, estimate the tensile stress at which catastrophic failure will occur. Compare this stress with the yield strength of 220 MPa for this steel