NDTE 3101 sound beam zones.pptx - ULTRASONIC TRAINING PRESENTED BY DICK ALGERA Course NDTE 3101 Durham College PROBE CHARACTERISTICS SOUND BEAM ZONES

NDTE 3101 sound beam zones.pptx - ULTRASONIC TRAINING...

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ULTRASONIC TRAINING PRESENTED BY DICK ALGERA Course NDTE 3101 Durham College
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PROBE CHARACTERISTICS SOUND BEAM ZONES DIVERGENCE REFLECTION REFRACTION
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Sound Beam Zones Components of the Beam The beam is comprised of the Dead Zone , Near Zone (Fresnel) and the Far Zone (Fraunhoffer). Dead zone : directly in front of the probe, no response from a reflector because it cannot be resolved from the main bang. Dead zone = Velocity x Pulse length/2
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Sound Beam Zones Near Zone : a zone of irregular sound pressure. Each component of the crystal produces a small pulse which combines with the others to produce an irregular sound field. Reflectors in the near zone may appear as multiple indications or its amplitude will vary greatly as the probe is moved slightly or the amplitude may not reflect how bad the indication is. Near zone length defined by N=D 2 F/4V
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Sound Beam Zones Far Zone: characterized by a smooth regular sound pressure. Starts immediately behind the near zone with maximum sound pressure measured along the center axis of the beam and decreases to zero due to beam spread .
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SOUND BEAM ZONES Near Zone N Far Zone N=D 2 /4 l D=2r \ N=(2r) 2 /4 l = 4r 2 /4 l = r 2 /l Also l =V/F \ N=D 2 F/4V
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SOUND BEAM ZONES Near Zone N Far Zone N=D 2 /4 l=12 2 /4(1.18)=144/4(1.18) = 30 mm v = 5900m/s f = 5 MHz D = 12mm l = V/F = 5900/5x10 6 = 0.00118m = 1.18mm
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  • Fall '16
  • Wavelength, Microphone, Near Field, Probe Design

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