Properties of Engineering Materials
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
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
Density
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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
Thermal properties
• Get a feel for the thermal properties of materials
• Widely varying set of conductivities, expansions
• Use heat gun and thermocouples
Displacement Indicator
Heat Gun
V Block
Sample
Test Plate
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
May do modulus of torsion
• Measure oscillation of torsion pendulum