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6 Special Methods

6 Special Methods. 6.1 Microwave Techniques 6.2 Dielectric Measurements 6.3 Thermoelectric Measurements. 6.1 Microwave Techniques. Frequency [Hz]. 4. 6. 8. 10. 12. 14. 16. 18. 20. 22. 24. 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. Wavelength [m]. 4. 2. 0. -2.

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6 Special Methods

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  1. 6 Special Methods 6.1 Microwave Techniques 6.2 Dielectric Measurements 6.3 Thermoelectric Measurements

  2. 6.1 Microwave Techniques

  3. Frequency [Hz] 4 6 8 10 12 14 16 18 20 22 24 10 10 10 10 10 10 10 10 10 10 10 Wavelength [m] 4 2 0 -2 -4 -6 -8 -10 -12 -14 -16 10 10 10 10 10 10 10 10 10 10 10 typical lattice constant Energy [eV] -10 -8 -6 -4 -2 0 2 4 6 8 10 10 10 10 10 10 10 10 10 10 10 10 g rays cosmic rays visible microwave light IR light UV light X-rays radio frequency Electromagnetic Spectrum

  4. Plane waves: Electromagnetic Waves in dielectrics: in conductors:

  5. y Reflection/Transmission between Dielectrics I dielectric II dielectric incident x reflected transmitted strong penetration  perceivable reflection

  6. y Reflection from Conductors I dielectric II conductor incident x transmitted “diffuse” wave reflected negligible penetration  almost perfect reflection with phase reversal

  7. circulator detector detector detector oscillator isolator detector horn antenna specimen oscillator isolator horn antenna specimen reflection (monostatic radar, pulse-echo) Far-Field Measurement Configurations transmission (bistatic radar, pitch-catch) scattering (bistatic radar, pitch-catch) oscillator isolator horn antenna specimen

  8. circulator oscillator isolator detector open-ended waveguide specimen stand-off distance coating foam core adhesive substrate corrosion damage skin laminate air backing Near-Field Inspection

  9. [mm] 60 40 20 0 0 20 40 60 [mm] Microwave Image of Rust Under Paint (Qaddoumi et al., 1997) 40 mm  40 mm area of rust on a steel plate 24 GHz, 12.5 mm standoff distance, 0.267 mm of paint

  10. circulator oscillator isolator detector modulator open-ended waveguide specimen stand-off distance infrared camera lock-in amplifier glass fiber-reinforced polymer plates (50  75 mm2) (Diener, 1995) Lock-in Thermography microwave raster scan lock-in thermography (phase image) bonding defects 150-µm-thick delamination

  11. 6.2 Dielectric Measurements

  12. E electric field H magnetic field D electric flux density B magnetic flux density J electric current density σ electric conductivity ε electric permittivity µ magnetic permeability complex electric permittivity ω angular frequency t time Maxwell's Equations: Fundamentals Harmonic solution:

  13. +Q +Q -Q -Q E E Fe Fe Electric Polarization dipole formation dipole rotation P electric polarization pe electric dipole moment V volume χeelectric susceptibility ε0 permittivity of free space

  14. I Q A E l Capacitance conducting dielectric lossy dielectric ideal dielectric

  15. ionic + dipolar atomic resonance electronic resonance ε’ Electric Permittivity [a. u.] ε’’ 103 106 109 1012 1015 1018 frequency [Hz] + + + _ _ _ _ Complex Electric Permittivity

  16. basic sensor Rg buffer Rg Im Im 1 Vm Vm   Vg Vm parallel plate electrodes Capacitive Probes sensor with guard electrodes Vg stray field electrodes

  17. Auto-Balancing Bridge device under test H L Rref Rg Im Im “virtual” ground _ + Vg high-gain operational amplifier vector voltmeter vector voltmeter

  18. uncoated uncoated 10 40 coated coated . 30 1 . Capacitance [pF] Conductance [μS] 0.1 20 0.01 10 0.001 0 0.1 1 10 100 0.1 1 10 100 Frequency [kHz] Frequency [kHz] conductive cloth for electric shielding Woven Composite

  19. 50 103 2.5 2.5 102 2.0 2.0 40 1.5 30 101 1.5 Water Uptake [%] Thickness Variation [%] 20 100 1.0 1.0 0.5 10-1 0.5 10 0.0 10-2 0 0.0 0 10 20 30 40 50 60 70 80 0 0.5 1.0 1.5 2.0 2.5 Time1/2 [hr1/2] Water Uptake [%] 5,350 hr 5,350 hr 1,590 hr 1,590 hr 1,007 hr 1,007 hr 580 hr 580 hr 122 hr 122 hr Relative Permittivity Dielectric Loss intact intact 10-1 10-1 100 100 101 101 102 102 103 103 104 104 105 105 106 106 107 107 108 108 109 109 Frequency [Hz] Frequency [Hz] Pethrick et al., 2002 Adhesively Bonded Composite

  20. 6.3 Thermoelectric Measurements

  21. A JA I T2 T1 JB B hB open-circuit Seebeck effect: JA = 0 A hA VS T2 T1 JB = 0 B T0 T0 hB _ V + Seebeck, Peltier, and Thomson effect: coupled electric and thermal flux Thermoelectric Effect J electric current density h thermal flux density σ electric conductivity (T = 0) κ thermal conductivity (V = 0) V voltage T temperature S thermoelectric power closed-circuit Seebeck effect: hA

  22. 30 W (tungsten) 20 Mo (molybdenum) 10 Ag (silver) 0 Cu (copper) Thermoelectric Power [µV/K] -10 Au (gold) -20 Pt (platinum) -30 Pd (palladium) -40 0 500 1000 1500 Temperature [K] Absolute Thermoelectric Power

  23. _ + V reference electrodes (B) electrical heating ~ ~ “cold” junction “hot” junction specimen (A) open-circuit Seebeck effect Contact Thermoelectric Tester Primary Effect: chemical composition Secondary Effects: anisotropy, texture fatigue, cold work, plasticity, residual stress, etc.

  24. 273 K 293 K 83 K 4.2 K 20 0 Thermoelectric Power [µV/K] -20 50 Electric Resistivity [µΩ cm] 40 -40 30 -60 20 Ag Content [%] 10 Ag Content [%] 0 0 0 20 20 40 40 60 60 80 80 100 100 palladium-silver binary alloy (Rudnitskii, 1956) TEP versus Chemical Composition

  25. hexagonal single crystal Zinc, relative to basal plane (Rowe and Schroeder, 1970) 3 perpendicular 2 1 Thermoelectric Power [µV/K] 0 parallel -1 -2 -3 0 50 100 150 200 250 300 Temperature [K] TEP Anisotropy

  26. -4.8 20 before annealing gold tip reference copper tip reference -4.9 15 Thermoelectric Power [µV/°C] 10 Difference in TEP [%] -5.0 5 after annealing -5.1 0 0 30 60 90 120 150 180 80 60 40 80 60 40 Azimuthal Angle [deg] Cold-rolling reduction [%] before annealing after annealing 50 µm cold-worked polycrystalline material Ti-6Al-4V, relative to cold work direction (Carreon and Medina, 2006) TEP versus Texture

  27. magnetometer specimen heat thermoelectric current closed-circuit Seebeck effect Noncontacting Thermoelectric Tester •  relative to surrounding intact material •  no artificial interface •  penetrating (with substantial depth) •  noncontact (with substantial lift-off)

  28. milled pressed plastic zone before annealing after annealing TEP is independent of size and shape Material Effects versus Geometry C11000 copper diameter 0.375” T  0.5 C/cm 2 mm lift-off distance 3”  3” scanning dimension 18 nT peak magnetic flux

  29. 25 before relaxation relaxation at 235 ºC relaxation at 275 ºC 20 relaxation at 315 °C 2nd relaxation at 315 °C 3rd relaxation at 460 °C 15 recrystallization at 600 °C Magnetic Signature [nT] 10 5 0 0 2A 4A 6A 8A 10A 12A 14A 16A Almen Peening Intensity shot-peened C11000 copper Residual Stress Characterization

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