UT Testing-Section 2 Physics of Ultrasound

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It must also be mentioned that the subscript ij attached to C (C ij ) in the above equation is used to indicate the directionality of the elastic constants with respect to the wave type and direction of wave travel. In isotropic materials, the elastic constants are the same for all directions within the material. However, most materials are anisotropic and the elastic constants differ with each direction. For example, in a piece of rolled aluminum plate, the grains are elongated in one direction and compressed in the others and the elastic constants for the longitudinal direction are different than those for the transverse or short transverse directions. V longitudinal V transverse
Examples of approximate compressional sound velocities in materials are: Aluminum - 0.632 cm/microsecond 1020 steel - 0.589 cm/microsecond Cast iron - 0.480 cm/microsecond. Examples of approximate shear sound velocities in materials are: Aluminum - 0.313 cm/microsecond 1020 steel - 0.324 cm/microsecond Cast iron - 0.240 cm/microsecond. When comparing compressional and shear velocities, it can be noted that shear velocity is approximately one half that of compressional velocity. The sound velocities for a variety of materials can be found in the ultrasonic properties tables in the general resources section of this site.
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Section 2: Physics of Ultrasound
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2.0: Ultrasound Formula http://www.
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Ultrasonic Formula
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2.1: Wave Propagation Ultrasonic te
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Acoustic Spectrum
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Acoustic Wave - Node and Anti-Node
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http://hyperphysics.phy-astr.gsu.ed
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2.2: Modes of Sound Wave Propagatio
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Longitudinal and shear waves
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Longitudinal and shear waves
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2.2.3 Longitudinal Wave Also Knows
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Longitudinal wave: Longitudinal wav
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2.2.4 Shear waves (S-Waves) In air,
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Shear waves
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Q10: For a shear wave travelling fr
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Rayleigh waves are a type of surfac
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Q29: The longitudinal wave incident
Page 39 and 40: The major axis of the ellipse is pe
Page 41 and 42: Surface wave
Page 43 and 44: Surface wave has the ability to fol
Page 45 and 46: Surface wave - One wavelength deep
Page 47 and 48: Love Wave http://web.ics.purdue.edu
Page 49 and 50: Other Reading: Rayleigh Waves Surfa
Page 51 and 52: Q110: What kind of wave mode travel
Page 53 and 54: 2.2.6 Lamb Wave: Lamb waves propaga
Page 55 and 56: Types of Wave New! • Plate wave-
Page 57 and 58: Plate or Lamb waves are similar to
Page 59 and 60: With Lamb waves, a number of modes
Page 61 and 62: Symmetrical = extensional mode Asym
Page 63 and 64: Symmetrical = extensional mode
Page 65 and 66: The form is determined by whether t
Page 67 and 68: Q1: The wave mode that has multiple
Page 69 and 70: Dispersion refers to the fact that
Page 71 and 72: Thickness Limitation: One can not g
Page 73 and 74: Spring model- A mass on a spring ha
Page 75 and 76: In terms of the spring model, Hooke
Page 77 and 78: Elastic Model / Longitudinal Wave
Page 79 and 80: Elastic Model / Shear Wave
Page 81 and 82: The Speed of Sound Hooke's Law, whe
Page 83 and 84: What properties of material affect
Page 85 and 86: Where V is the speed of sound, C is
Page 87 and 88: Q50: The principle attributes that
Page 89: E/N/G
Page 93 and 94: Shear Wave Velocity: V S The veloci
Page 95 and 96: The applet below shows a longitudin
Page 97 and 98: http://www.ndt-ed.org/EducationReso
Page 99 and 100: Java don’t work? http://jingyan.b
Page 101 and 102: Java don’t work? http://jingyan.b
Page 103 and 104: As can be noted by the equation, a
Page 105 and 106: The two velocities of sound are lin
Page 107 and 108: Sensitivity and resolution are two
Page 109 and 110: 2.5.2 Grain Size & Frequency Select
Page 111 and 112: Since more things in a material are
Page 113 and 114: Detectability variable: • pulse l
Page 115 and 116: Q7: When a material grain size is o
Page 117: Pulse Length: A sound pulse traveli
Page 120 and 121: Determining cross sectional area us
Page 122 and 123: Pulse volume rule-of-thumb: Competi
Page 124 and 125: When sound travels through a medium
Page 126 and 127: Scattering: Grain Size and Wave Fre
Page 128 and 129: Spreading/ Scattering / adsorption
Page 130 and 131: The units of the attenuation value
Page 132 and 133: Attenuation can be determined by ev
Page 134 and 135: A o Ut A
Page 137 and 138: 2.6.3 Frequency selection There is
Page 139 and 140: Q94: In general, which of the follo
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Q7: When the material grain size is
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Transmission & Reflection Animation
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The following applet can be used to
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Reflection/Transmission Energy as a
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2.8: Reflection and Transmission Co
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Since the amount of reflected energ
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Note that the reflection and transm
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If reflection and transmission at i
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Incident Wave other than Normal? -
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Further Reading (Olympus Technical
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Further Reading: Reflection & Trans
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2.9: Refraction and Snell's Law
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V s1 Only If this medium support sh
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http://www.ni.com/white-paper/3368/
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Note that in the diagram, there is
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Snell Law
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Snell Law
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Example: Snell’s Law L-wave and S
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Snell Law: First critical angle
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Q155 Which of the following can occ
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Q: When angle beam contact testing
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Snell Law: http://techcorr.com/serv
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More on Snell Law Like light, when
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http://www.ndtcalc.com/calculators.
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Mode Conversion http://www.ndt-ed.o
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Snell's Law holds true for shear wa
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In the applet below, the shear (tra
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Creep wave
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Beyond the first critical angle, on
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Note that the applet defaults to co
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Offset of Normal probe above circul
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Refraction and mode conversion at n
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Q118: At the water-steel interface,
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Q72. In a water immersion test, ult
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Q53. The term used to determined th
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The absolute noise level and the ab
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Sound Volume: Area x pulse length M
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Acoustic Volume: w x w y ∆t
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Determining cross sectional area us
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4. Decreases in materials with high
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Pulse Length Affect Resolution
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Transducer cut-out http://ichun-che
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UT Transducer
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UT Transducer- Surface creep wave t
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UT Transducer
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When the origins of the two interac
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However, as stated previously, soun
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Q5: Acoustic pressure along the bea
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Of course, there are more than two
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2.12.3 Fresnel & Fraunhofer Zone Fr
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The Near Field (Fresnel)- Wave Inte
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Fresnel / Fraunhofer Zone
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Near field (near zone) or Fresnel z
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Near/ Far Fields
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where D is the diameter of the tran
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Fresnel & Fraunhofer Zone 10dB, K-0
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Fresnel & Fraunhofer Zone
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Q: Where does beam divergence occur
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Q160 Beam divergence is a function
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Dead Zone - The interval following
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Dead Zone -The initial pulse is a t
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Dead Zone http://www.ni.com/white-p
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Q36: To eliminate the decrease in s
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Large Reflector Inverse Rule
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Small Reflector Inverse Square Rule
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Fundamental Frequency The lowest re
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Transducers Piezoelectric Thickness
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Application Case#1: The specimen's
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Application Case#2: Electromagnetic
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Q7: The resonance frequency of 2cm
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dB is a measures of ratio of 2 valu
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The Decibel The equation used to de
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Why is the dB unit used? Use of dB
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Use of the dB in Sound Measurements
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Since transducers and microphones p
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Sound Levels- Relative
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Practice:
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“Absolute" Sound Levels Whenever
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Absolute: The standard reference so
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Exercise: ANSWER Find the absolute
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Relative dB: Example Calculation 1
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Example Calculation 3 Consider the
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2.16 Practice Makes Perfect
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Q104: If an ultrasonic wave is tran
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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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