Engineering Materials Properties Overview for Lab Experiments

1. Properties of Engineering Materials

2. Overview • Purpose of lab is to familiarize you with basic properties of common engineering materials • Density, Young’s modulus, thermal conductivity, coefficient of expansion, modulus of torsion • Do simple experiments to find these properties • Also become familiar with the physical properties of some common optical materials used in the IR

3. Young’s modulus Use bars of material set on simple end supports Measure central deflection as a function of applied load Use physical dimensions of bars to calculate Young’s modulus using Beam equation Cantilever beam configuration also work!

4. Young’s modulus (2) • Use Instron machine and find Stress-Strain curve • Actual measurement is force-displacement curve • Use specimen geometry and convert measured force-displacement to stress-strain

5. Young’s modulus (2)

6. Density • Measure physical dimensions of bars • Calculate volume • Measure mass on an electronic scale • Density = mass/unit volume • Measure a drop of water, small piece of paper • Get a feel for how sensitive the scale is

7. Thermal properties • Get a feel for the thermal properties of materials • Widely varying set of conductivities, expansions • Measure the nominal length of Copper, Aluminum and steel tube • Measure the temperature using thermocouple and thermometer • Measure the elongation • Find CTE and compare to the reference value

8. Thermal properties

9. Optical materials Sapphire Al2O3, .14 – 6.5 um, very hard, low expanson, tough CaF2, .13 – 12 um, moderately soft, expansion like Al, good UV mat’l Silicon 1.2 – 15 um, reasonably hard, quite plastic and strong, brittle Germanium 1.8 – 23 um, similar to Silicon but not as tough, n = 4 ZnSe .5 – 22 um, reasonably easy to use but somewhat soft ZnS .5 – 14 um, similar to ZnSe but cheaper, maybe a little less durable

10. May do modulus of torsion • Measure oscillation of torsion pendulum