Two nickel cups are to be made 100 mm in diameter and 50 mm in height with a floor and wall thickness of 10 mm using two different processes. In the first process, the wall and floor of the cup are to be cut from a 40 mm long, 100 mm diameter tube and 100 mm diameter disk of 10 mm thick plate stock. The wall and floor are then welded together. In the second process, the cup is to be machined from a 100 mm diameter 50 mm long piece of bar stock. (a) Given a welding joint thickness of 3 mm, how much work would be required to melt the weld nugget (see Table 30.2)? (b) Using an average of the range given in Table 21.2, how much work would be required to machine away the inside of the cup? Neglect the work required to create the bar stock and to cut it into the specified tube, disk, and bar shapes.

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Table 30.2 Approximate Specific Energies Required to Melt a Unit Volume of Commonly Welded Metals. Material Aluminum and its alloys Cast irons Copper Bronze (90Cu-10Sn) Magnesium Nickel Steels Stainless steels Titanium Specific energy, u J/mm BTU/n3 2.9 41 7.8 112 6.1 87 4.2 59 2.9 42 9.8 142 9.1-10.3 128-146 9.3-9.6 133-137 14.3 204 Table 30.2 Approximate Specific Energies Required to Melt a Unit Volume of Commonly Welded Metals. Material Aluminum and its alloys Cast irons Copper Bronze (90Cu-10Sn) Magnesium Nickel Steels Stainless steels Titanium Specific energy, u J/mm BTU/n3 2.9 41 7.8 112 6.1 87 4.2 59 2.9 42 9.8 142 9.1-10.3 128-146 9.3-9.6 133-137 14.3 204