Concept explainers
2-21 to 2-23 A 1-in-diameter rod. 3 ft long, of unknown material is found in a machine shop. A variety of inexpensive nondestructive tests are readily available to help determine the material, as described below:
- (a) Visual inspection.
- (b) Scratch test: Scratch the surface with a file; observe color of underlying material and depth of scratch.
- (c) Check if it is attracted to a magnet.
- (d) Measure weight (±0.05 Ibf).
- (e) Inexpensive bending deflection test: Clamp one end in a vise, leaving 24 in cantilevered. Apply a force of 100 Ibf (±1 lbf). Measure deflection of the free end (within ± 1/32 in).
- (f) Brinell hardness test.
Choose which tests you would actually perform, and in what sequence, to minimize time and cost, but to determine the material with a reasonable level of confidence. The table below provides results that would be available to you if you choose to perform a given lest. Explain your process, and include any calculations. You may assume the material is one listed in Table A-5. If it is carbon steel, try to determine an approximate specification from Table A-20.
Test | Results if test were made | ||
Prob. 2-21 | Prob. 2-22 | Prob. 2-23 | |
(a) | Dark gray, rough surface finish, moderate scale | Silvery gray, smooth surface finish, slightly tarnished | Reddish-brown, tarnished, smooth surface finish |
(b) | Metallic gray, moderate scratch | Silvery gray, deep scratch | Shiny brassy color, deep scratch |
(c) | Magnetic | Not magnetic | Not magnetic |
(d) | W = 7.95 Ibf | W = 2.90 Ibf | W = 9.00 Ibf |
(e) | δ = 5/16 in | δ = 7/8 in | δ = 17/32 in |
(f) | HB = 200 | HB = 95 | HB = 70 |
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