UT Testing-Section 2 Physics of Ultrasound

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Refraction takes place at an interface due to the different velocities of the acoustic waves within the two materials. The velocity of sound in each material is determined by the material properties (elastic modulus and density) for that material. In the animation below, a series of plane waves are shown traveling in one material and entering a second material that has a higher acoustic velocity. Therefore, when the wave encounters the interface between these two materials, the portion of the wave in the second material is moving faster than the portion of the wave in the first material. It can be seen that this causes the wave to bend. http://www.ndt-ed.org/EducationResources/CommunityCollege/Ultrasonics/Graphics/Flash/waveRefraction.swf
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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
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 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 169: Snell's Law describes the relations
Page 173 and 174: Snell Law http://www.ndt-ed.org/Edu
Page 175 and 176: When a longitudinal wave moves from
Page 177 and 178: Refraction and mode conversion occu
Page 179 and 180: For example, calculate the first cr
Page 181 and 182: Snell Law: 1 st / 2 nd Critical Ang
Page 183 and 184: Q. Both longitudinal and shear wave
Page 191 and 192: Typical angle beam assemblies make
Page 193 and 194: Depth & Skip
Page 195 and 196: Second Critical Angle The second cr
Page 197 and 198: 2.10: Mode Conversion When sound tr
Page 199 and 200: In the previous section, it was poi
Page 201 and 202: Snell's Law
Page 203 and 204: Reflections
Page 205 and 206: V S1 V S2
Page 207 and 208: Snell Law- 1 st & 2 nd Critical Ang
Page 209 and 210: 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
Page 215 and 216: Refraction and mode conversion at n
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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
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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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