UT Testing-Section 2 Physics of Ultrasound

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Surface (or Rayleigh) waves travel the surface of a relatively thick solid material penetrating to a depth of one wavelength. Surface waves combine both (1) a longitudinal and (2) transverse motion to create an elliptic orbit motion as shown in the image and animation below. http://www.ndt-ed.org/EducationResources/CommunityCollege/Ultrasonics/Graphics/Flash/rayleigh.swf
The major axis of the ellipse is perpendicular to the surface of the solid. As the depth of an individual atom from the surface increases the width of its elliptical motion decreases. Surface waves are generated when a longitudinal wave intersects a surface near the second critical angle and they travel at a velocity between .87 and .95 of a shear wave. Rayleigh waves are useful because they are very sensitive to surface defects (and other surface features) and they follow the surface around curves. Because of this, Rayleigh waves can be used to inspect areas that other waves might have difficulty reaching. Wave velocity: • Longitudinal wave velocity =1v, • The velocity of shear waves through a material is approximately half that of the longitudinal waves, (≈0.5v) • Surface waves are generated when a longitudinal wave intersects a surface near the second critical angle and they travel at a velocity between .87 and .95 of a shear wave. ≈(0.87~0.95)x0.5v
Page 1: Section 2: Physics of Ultrasound
Page 4 and 5: 2.0: Ultrasound Formula http://www.
Page 6 and 7: Ultrasonic Formula
Page 9 and 10: 2.1: Wave Propagation Ultrasonic te
Page 11 and 12: Acoustic Spectrum
Page 13 and 14: Acoustic Wave - Node and Anti-Node
Page 15 and 16: http://hyperphysics.phy-astr.gsu.ed
Page 17 and 18: 2.2: Modes of Sound Wave Propagatio
Page 19 and 20: Longitudinal and shear waves
Page 21 and 22: Longitudinal and shear waves
Page 23 and 24: 2.2.3 Longitudinal Wave Also Knows
Page 25 and 26: Longitudinal wave: Longitudinal wav
Page 28 and 29: 2.2.4 Shear waves (S-Waves) In air,
Page 30 and 31: Shear waves
Page 33 and 34: Q10: For a shear wave travelling fr
Page 35 and 36: Rayleigh waves are a type of surfac
Page 37: Q29: The longitudinal wave incident
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
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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
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Spreading/ Scattering / adsorption
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The units of the attenuation value
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Attenuation can be determined by ev
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A o Ut A
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2.6.3 Frequency selection There is
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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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