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