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Material properties

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Precision balance. Two ball spherometer. Thermocouples ... Place two ball spherometer on top of sample. Why use this method of measuring deflection? ... – PowerPoint PPT presentation

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Title: Material properties


1
Material properties
2
Overview
  • Purpose to give a feel for some common
    materials used in opto-mechanics
  • Density
  • Structural
  • Hardness
  • Thermal
  • Also to introduce some useful instruments
  • Precision balance
  • Two ball spherometer
  • Thermocouples
  • Instron hardness tester

3
Density
  • Measure volume of samples
  • How accurately relative to how well mass is
    measured?
  • Measure mass
  • Use precision balance
  • First zero balance
  • Set sample on carefully
  • Remove with same care
  • What volume corresponds to the smallest mass
    measureable?
  • Will contamination effect your measurement?

4
Structural properties
  • We are not well set up for this instrument was
    late
  • Support sample across two rolls
  • Place strap around middle, connect to scale
  • Place two ball spherometer on top of sample
  • Why use this method of measuring deflection?
  • Jack up table to load sample
  • Record deflection versus load
  • Calculate Youngs modulus

5
Thermal properties
  • Coefficient of thermal expansion
  • Approximate but can see relative differences
  • Thermal conductivity
  • Change T by known amount and plot ?T at end
  • Do answers relate to how warm material feels?
  • Heat capacity
  • How much does heat source cool as sample warms

6
Hardness
  • Have new hardness tester
  • Uses 1/16 carbide ball
  • Forces ball into material being tested
  • Measures depth of penetration d at certain force
    f
  • Hardness is df with various scaling factors
  • Get instruction before using machine
  • Make sure sample is clean, both sides
  • Fits anvil well
  • Contamination will affect answer

7
Spring Wires
  • Idea - familiarity with the flexibility of
    different materials
  • Also idea of permanent deformation
  • Flex to failure
  • With shape memory wire see how it behaves
  • Use heat gun
  • In vibration lab well look at torsion of wires

8
IR Optical Materials
  • Calcium fluoride - transparent in visible
  • Thermally sensitive, brittle, softer than most
    glasses
  • Silicon opaque in visible xparent 2-5 µm
  • Index about 3.0 so what is its reflectivity
  • Germanium opaque in visible, xparent at 10 µm
  • Index about 3.5
  • Sapphire Al2O3 very hard, low CTE
  • ZnSe yellowish, some visible transmission, soft
  • Moderate index, reasonably tough

9
Examples of good O-M practice
  • Adhesive mirror mounting
  • Kinematic mounting and adjustment
  • Flexure features including flex pivots
  • Low stress adjustments
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