Section 2: Physics of Ultrasound

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Q2.8: The acoustic impedance of material used to determined: A. Angle of refraction at the interface B. Attenuation of material C. Relative amount of sound energy coupled through and reflected at an interface D. Beam spread within the material
2.8: Reflection and Transmission Coefficients (Pressure) Ultrasonic waves are reflected at boundaries where there is a difference in acoustic impedances (Z) of the materials on each side of the boundary. (See preceding page for more information on acoustic impedance.) This difference in Z is commonly referred to as the impedance mismatch. The greater the impedance mismatch, the greater the percentage of energy that will be reflected at the interface or boundary between one medium and another. The fraction of the incident wave intensity that is reflected can be derived because particle velocity and local particle pressures must be continuous across the boundary.
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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
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The major axis of the ellipse is pe
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Surface wave
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Surface wave has the ability to fol
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Surface wave - One wavelength deep
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Love Wave http://web.ics.purdue.edu
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Other Reading: Rayleigh Waves Surfa
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Q110: What kind of wave mode travel
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2.2.6 Lamb Wave: Lamb waves propaga
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Types of Wave New! • Plate wave-
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Plate or Lamb waves are similar to
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With Lamb waves, a number of modes
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Symmetrical = extensional mode Asym
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Symmetrical = extensional mode
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The form is determined by whether t
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Q1: The wave mode that has multiple
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Dispersion refers to the fact that
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Thickness Limitation: One can not g
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Spring model- A mass on a spring ha
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In terms of the spring model, Hooke
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Elastic Model / Longitudinal Wave
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Elastic Model / Shear Wave
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The Speed of Sound Hooke's Law, whe
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What properties of material affect
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Where V is the speed of sound, C is
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Q50: The principle attributes that
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E/N/G
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Examples of approximate compression
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Shear Wave Velocity: V S The veloci
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The applet below shows a longitudin
Page 97 and 98: http://www.ndt-ed.org/EducationReso
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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
Page 141 and 142: Q7: When the material grain size is
Page 143 and 144: Transmission & Reflection Animation
Page 145 and 146: The following applet can be used to
Page 147: Reflection/Transmission Energy as a
Page 151 and 152: Since the amount of reflected energ
Page 153 and 154: Note that the reflection and transm
Page 155 and 156: If reflection and transmission at i
Page 157 and 158: Incident Wave other than Normal? -
Page 159 and 160: Further Reading (Olympus Technical
Page 161 and 162: Further Reading: Reflection & Trans
Page 163 and 164: 2.9: Refraction and Snell's Law
Page 165: V s1 Only If this medium support sh
Page 168 and 169: http://www.ni.com/white-paper/3368/
Page 172 and 173: Note that in the diagram, there is
Page 174 and 175: Snell Law
Page 176 and 177: Snell Law
Page 178 and 179: Example: Snell’s Law L-wave and S
Page 180 and 181: Snell Law: First critical angle
Page 182 and 183: Q155 Which of the following can occ
Page 184: Q: When angle beam contact testing
Page 192 and 193: Snell Law: http://techcorr.com/serv
Page 194 and 195: More on Snell Law Like light, when
Page 196 and 197: 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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Section 2: Physics of Ultrasound

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