Section 2: Physics of Ultrasound

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Example: Snell’s Law L-wave and S-wave refraction angles are calculated using Snell’s law. You also can use this law to determine the first critical angle for any combination of materials. Where: Ɵ 2 ° = angle of the refracted beam in the UUT Ɵ 1 ° = incident angle from normal of beam in the wedge or liquid V 1 = velocity of incident beam in the liquid or wedge V 2 = velocity of refracted beam in the UUT
For example, calculate the first critical angle for a transducer on a plastic wedge that is examining aluminum. V 1 = 0.267 cm/µs (for L-waves in plastic) V 2 = 0.625 cm/µs (for L-waves in aluminum) Ɵ 2 ° = 90 degree (angle of L-wave for first critical angle) Ɵ 1 ° = unknown The plastic wedge must have a minimum angle of 25.29 ° to transmit only S- waves into the UUT. When the S-wave angle of refraction is greater than 90°, all ultrasonic energy is reflected by the UUT.
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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
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http://www.ndt-ed.org/EducationReso
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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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As can be noted by the equation, a
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The two velocities of sound are lin
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Sensitivity and resolution are two
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2.5.2 Grain Size & Frequency Select
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Since more things in a material are
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Detectability variable: • pulse l
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Q7: When a material grain size is o
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Pulse Length: A sound pulse traveli
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Determining cross sectional area us
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Pulse volume rule-of-thumb: Competi
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When sound travels through a medium
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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 and 148: Reflection/Transmission Energy as a
Page 149 and 150: 2.8: Reflection and Transmission Co
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 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.
Page 198 and 199: Mode Conversion http://www.ndt-ed.o
Page 200 and 201: Snell's Law holds true for shear wa
Page 202 and 203: In the applet below, the shear (tra
Page 204 and 205: Creep wave
Page 206 and 207: Beyond the first critical angle, on
Page 208 and 209: Note that the applet defaults to co
Page 210 and 211: Offset of Normal probe above circul
Page 212 and 213: Refraction and mode conversion at n
Page 218 and 219: Q118: At the water-steel interface,
Page 220 and 221: Q72. In a water immersion test, ult
Page 222 and 223: Q53. The term used to determined th
Page 224 and 225: The absolute noise level and the ab
Page 226 and 227: 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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