Question 2.21: A 1-in-diameter rod, 3 ft long, of unknown material is found...

First, try to find the broad category of material (such as in Table A-5). Visual, magnetic, and scratch tests are fast and inexpensive, so should all be done. Results from these three would favor steel, cast iron, or maybe a less common ferrous material. The expectation would likely be hot-rolled steel. If it is desired to confirm this, either a weight or bending test could be done to check density or modulus of elasticity. The weight test is faster. From the measured weight of 7.95 \mathrm{lbf}, the unit weight is determined to be

which agrees well with the unit weight of 0.282 \mathrm{lbf} / \mathrm{in}^{3} reported in Table A-5 for carbon steel. Nickel steel and stainless steel have similar unit weights, but surface finish and darker coloring do not favor their selection. To select a likely specification from TableA-20, perform a Brinell hardness test, then use Eq. (2-21) to estimate an ultimate strength of S_{u}=0.5 H_{B}=0.5(200)=100 \mathrm{kpsi}. Assuming the material is hot-rolled due to the rough surface finish, appropriate choices from Table A-20 would be one of the higher carbon steels, such as hot-rolled AISI 1050,1060 , or 1080 .

Eq. (2-21),

2.22

First, try to find the broad category of material (such as in Table A-5). Visual, magnetic, and scratch tests are fast and inexpensive, so should all be done. Results from these three favor a softer, non-ferrous material like aluminum. If it is desired to confirm this, either a weight or bending test could be done to check density or modulus of elasticity. The weight test is faster. From the measured weight of 2.90 \mathrm{lbf}, the unit weight is determined to be

which agrees reasonably well with the unit weight of 0.098 \mathrm{lbf} / \mathrm{in}^{3} reported in Table A-5 for aluminum. No other materials come close to this unit weight, so the material is likely aluminum.  .

2.23

First, try to find the broad category of material (such as in Table A-5). Visual, magnetic, and scratch tests are fast and inexpensive, so should all be done. Results from these three favor a softer, non-ferrous copper-based material such as copper, brass, or bronze. To further distinguish the material, either a weight or bending test could be done to check density or modulus of elasticity. The weight test is faster. From the measured weight of 9 \mathrm{lbf}, the unit weight is determined to be

which agrees reasonably well with the unit weight of 0.322 \mathrm{lbf} / \mathrm{in}^{3} reported in Table A-5 for copper. Brass is not far off \left(0.309 \mathrm{lbf} / \mathrm{in}^{3}\right), so the deflection test could be used to gain additional insight. From the measured deflection and utilizing the deflection equation for an end-loaded cantilever beam from Table A-9, Young’s modulus is determined to be

which agrees better with the modulus for copper (17.2 Mpsi) than with brass (15.4 Mpsi). The conclusion is that the material is likely copper.

Table A–20