UT Testing-Section 2 Physics of Ultrasound

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Content: Section 2: Physics of Ultrasound 2.0: Ultrasound Formula 2.1: Wave Propagation 2.2: Modes of Sound Wave Propagation 2.3: Sound Propagation in Elastic Materials 2.4: Properties of Acoustic Plane Wave 2.5: Wavelength and Defect Detection 2.6: Attenuation of Sound Waves 2.7: Acoustic Impedance 2.8: Reflection and Transmission Coefficients (Pressure) 2.9: Refraction and Snell's Law 2.10: Mode Conversion 2.11: Signal-to-Noise Ratio 2.12: The Sound Fields- Dead / Fresnel & Fraunhofer Zones 2.13: Inverse Square Rule/ Inverse Rule 2.14: Resonance 2.15 Measurement of Sound 2.16 Practice Makes Perfect
Page 1: Section 2: Physics of Ultrasound
Page 5 and 6: Ultrasonic Formula
Page 7: Parameters of Ultrasonic Waves
Page 10 and 11: Acoustic Spectrum
Page 12 and 13: Acoustic Spectrum
Page 14 and 15: Acoustic Wave - Node and Anti-Node
Page 16 and 17: Q151 A point, line or surface of a
Page 18 and 19: 2.2.2 Propagation & Polarization Ve
Page 20 and 21: Longitudinal and shear waves- Defin
Page 22 and 23: Longitudinal and shear waves
Page 24 and 25: In longitudinal waves, the oscillat
Page 26: Longitudinal Wave
Page 29 and 30: Shear waves vibrate particles at ri
Page 31: In the transverse or shear wave, th
Page 34 and 35: 2.2.5 Rayleigh Characteristics Rayl
Page 36 and 37: Rayleigh waves
Page 38 and 39: Surface (or Rayleigh) waves travel
Page 40 and 41: The major axis of the ellipse is pe
Page 42 and 43: Surface wave or Rayleigh wave are f
Page 44 and 45: Surface wave - Following Contour Su
Page 46 and 47: Rayleigh Wave http://web.ics.purdue
Page 48 and 49: Love Wave
Page 50 and 51: At this depth, wave energy is about
Page 52 and 53:
Q: Which of the following modes of
Page 54 and 55:
Since the 1990s, the understanding
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Plate or Lamb waves are the most co
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Plate wave or Lamb wave are formed
Page 60 and 61:
When guided in layers they are refe
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Symmetrical = extensional mode Asym
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Other Reading: Lamb Wave Lamb waves
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Fig. 4 Diagram of the basic pattern
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2.2.7 Dispersive Wave: Wave modes s
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Plate or Lamb waves are generated a
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2.3: Sound Propagation in Elastic M
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Spring model- A mass on a spring ha
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Elastic Model
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Elastic Model / Longitudinal Wave
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Elastic Model / Shear Wave
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Since the mass m and the spring con
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Elastic constant → spring constan
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Q163 Acoustic velocity of materials
Page 88 and 89:
When calculating the velocity of a
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It must also be mentioned that the
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Longitudinal Wave Velocity: V L The
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2.4: Properties of Acoustic Plane W
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http://www.ndt-ed.org/EducationReso
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Java don’t work? Uninstalled →
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Java don’t work? http://jingyan.b
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Java don’t work? http://jingyan.b
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The velocities sound waves The velo
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2.5: Wavelength and Defect Detectio
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Keywords: • Discontinuity must be
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Keywords: • Coarse grains →Lowe
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Coarse grains →Lower frequency to
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Keywords: • Higher the frequency,
Page 116 and 117:
2.5.3 Further Reading Detectability
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Determining cross sectional area us
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“Sonic pulse volume” and S/N (d
Page 123 and 124:
2.6: Attenuation of Sound Waves 2.6
Page 125 and 126:
Absorption: Sound attenuations are
Page 127 and 128:
Anisotropic Columnar Grains with di
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The amplitude change of a decaying
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Attenuation is generally proportion
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Amplitude at distance Z where: Wher
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2.6.2 Factors Affecting Attenuation
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2.6.4 Further Reading on Attenuatio
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Q168: Heat conduction, viscous fric
Page 142 and 143:
2.7: Acoustic Impedance Acoustic im
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Sound travels through materials und
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Reflection/Transmission Energy as a
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Q2.8: The acoustic impedance of mat
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When the acoustic impedances of the
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Reflection Coefficient:
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Using the above applet, note that t
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Incident Wave other than Normal? -
Page 158 and 159:
Q: The figure above shown the parti
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For example: The dB loss on transmi
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Q6: For an ultrasonic beam with nor
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Refraction and Snell's Law When an
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Refraction takes place at an interf
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Snell's Law describes the relations
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Snell Law http://www.ndt-ed.org/Edu
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When a longitudinal wave moves from
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Refraction and mode conversion occu
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For example, calculate the first cr
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Snell Law: 1 st / 2 nd Critical Ang
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Q. Both longitudinal and shear wave
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Typical angle beam assemblies make
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Depth & Skip
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Second Critical Angle The second cr
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2.10: Mode Conversion When sound tr
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In the previous section, it was poi
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Snell's Law
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Reflections
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V S1 V S2
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Snell Law- 1 st & 2 nd Critical Ang
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Transverse wave can be introduced i
Page 211 and 212:
Calculate the offset for following
Page 213 and 214:
Refraction and mode conversion at n
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Refraction and mode conversion at n
Page 217 and 218:
Q1. From the above figures, if the
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Q: On Calculation: Incident angle=
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Q1. If you were requested to design
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2.11: Signal-to-Noise Ratio In a pr
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The following formula relates some
Page 227 and 228:
Rather than go into the details of
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Determining cross sectional area us
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“Sonic pulse volume” and S/N (d
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Pulse Length
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2.12: The Sound Fields 2.12.1 Wave
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When waves interact, they superimpo
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UT Transducer http://www.fhwa.dot.g
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UT Transducer
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Wave Interaction Complete in-phase
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With an ultrasonic transducer, the
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29. It is possible for a discontinu
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2.12.2 Variations in sound intensit
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The sound wave exit from a transduc
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The Near Field (Fresnel) and the Fa
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Amplitude ← Near Field Effect: Be
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Near field (near zone) or Fresnel z
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Near/ Far Fields http://miac.unibas
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where α is the radius of the trans
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The curvature and the area over whi
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Fresnel & Fraunhofer Zone
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Fresnel & Fraunhofer Zone http://st
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Q4: A transducer has a near field i
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2.12.4 Dead Zone In ultrasonic test
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Dead Zone -The initial pulse is a t
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Dead Zone Illustration http://www.n
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Q: On an A-scan display, the “dea
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2.13: Inverse Square Rule/ Inverse
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Small Reflector, a reflector smalle
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2.14: Resonance Another form wave i
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Thickness of Crystal at Fundamental
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Resonance UT Testing- The diagram b
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From the natural frequencies it is
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Q: The formula used to determine th
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2.15 Measurement of Sound
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Ultrasonic Formula - Signal Amplitu
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where: delta X is the difference in
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From this table it can be seen that
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However, the power or intensity of
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Revising the table to reflect the r
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Sound Levels- Relative dB
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“Absolute" Sound Levels Sound pre
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dB meter 97.3dB against standards s
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Exercise: Find the absolute sound l
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Practice: dB
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Example Calculation 2 If the intens
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What is the absolute rock concert s
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Practice Makes Perfect 28. An advan
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学习总是开心事
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UT Testing-Section 2 Physics of Ultrasound

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