(a) A bar 200 mm long and having a square cross section 15 mm on an edge is pulled in tension with a load of 98,000 N and experiences an elongation of 0.10 mm. Assuming that the deformation is entirely linear elastic, calculate the elastic modulus.
(b) If a metal sample has oy = 148 MPa; 0o = 28 MPa; and Ky = 0.55 MPa m1/2,calculate:
(i) the average grain diameter
(ii) the yield strength of a sample with half the average grain diameter
(c) A sheet of steel 1.5 mm thick has nitrogen atmospheres on both sides at 1200°C and is permitted to achieve a steady-state diffusion condition. The diffusion coefficient for nitrogen in steel at this temperature is 6x10-11 m/s, and the diffusion flux is found to be 1.2x10-7 kg/m2.s. Also, it is known that the concentration of nitrogen in the steel at the high-pressure surface is 4 kg/m3. How far into the sheet from this high-pressure side will the concentration be 2.0 kg/m3?
(d) Rank the following materials, gold, polyethylene and alumina in order of increasing thermal conductivity. Justify your answer.
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