(1) (a) An AISI 4340 steel plate has a widthWof 30 cm and has a central crack 2aof 3 mm. The plate is under a uniform stress. This steel has aKIcvalue of 50 MPa m1/2. Find the maximum stress for this crack length.

(b) If the operating stress is 1,500 MPa, compute the maximum crack size that the steel may have without failure

(2) The strength of alumina is approximatelyE/15, where Eis the Young's modulus of alumina, equal to 380 GPa. Use the Griffith equation in the planestrain form to estimate the critical size of defect corresponding to fracture of alumina

(3) An Al2O3 specimen is being pulled in tension. The specimen contains flaws having a size of 100m. If the surface energy of Al2O3 is 0.8 J/m2, what is the fracture stress? Use Griffith's criterion.E=380 GPa

(4) Machining of SiC produced surface flaws of a semielliptical geometry. The flaws that were generated have dimensionsa= 1 mm, widthw= 100 mm, andc= 5 mm, and the thickness of the specimen isB=20 mm. Calculate the maximum stress that the specimen can withstand in tension.KIc= 4 MPa m1/2