Answer Happy

Question 1 (a) A structure component in the shape of a flat plate 12.6 mm thick is to be fabricated from a metal alloy for which the yield strength and plane strain fracture toughness values are 350 MPa and 32.9 MPa √m, respectively; for this particular geometry, the value of Y is 1.75. Assuming a design stress of one half of the yield strength, is it possible to compute the critical length of a surface flaw? If so, determine its length; if this is not possible from the given data, then explain why. (8 marks) (b) A specimen of a ceramic material having a fracture strength of 30 GPa is pulled in tension with a stress of 900 MPa. Will the specimen fail if its "most severe flaw" is an internal crack that has a length of 0.30 mm and a tip radius of curvature of 5x10 mm? Why or why not? (Hint: Assume that the specimen is much bigger than the crack in size.) (8 marks) (c) Following fracture of a steel bar tested in tension and having an initial gauge length of 2 in and diameter of 0.505 in, the final gauge length and diameter are found to be 2.48 in and 0.3 in, respectively. Calculate the percentage elongation, percentage reduction in area and true fracture strain. (9 marks)