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ut1 ut1 Presentation Transcript

  • Ultrasonic Testing Part 1 TWI
  • Ultrasonic Testing NDT Training & Certification
  • Course Layout
    • Duration : 9.5 Days (Mon – Fri)
    • Start : 8:30 am
    • Coffee Break : 10:00 – 10:30 am
    • Lunch : 12:30 – 1:30 pm
    • Tea Break : 3:00 – 3:30 pm
    • Day End : 5:00 pm
    • Course Objective: To train and prepare participants to obtain required skill and knowledge in Ultrasonic Testing and to meet the examination schemes requirements.
  • NDT
    • Most common NDT methods:
    Penetrant Testing (PT) Magnetic Particle Testing (MT) Eddy Current Testing (ET) Radiographic Testing (RT) Ultrasonic Testing (UT) Mainly used for surface testing Mainly used for Internal Testing
  • NDT
    • Which method is the best ?
    • Depends on many factors and conditions
  • Basic Principles of Ultrasonic Testing
    • To understand and appreciate the capability and limitation of UT
  • Basic Principles of Ultrasonic Testing Sound is transmitted in the material to be tested The sound reflected back to the probe is displayed on the Flaw Detector
  • Basic Principles of Ultrasonic Testing The distance the sound traveled can be displayed on the Flaw Detector The screen can be calibrated to give accurate readings of the distance Bottom / Backwall Signal from the backwall
  •  
  • Basic Principles of Ultrasonic Testing The presence of a Defect in the material shows up on the screen of the flaw detector with a less distance than the bottom of the material Defect The BWE signal Defect signal
  • The depth of the defect can be read with reference to the marker on the screen 60 mm 0 10 20 30 40 50 60
  • Thickness / depth measurement A A B B C C The THINNER the material the less distance the sound travel The closer the reflector to the surface, the signal will be more to the left of the screen The thickness is read from the screen 68 46 30
  • Ultrasonic Testing Principles of Sound
  • Sound
    • Wavelength :
    • The distance required to complete a cycle
      • Measured in Meter or mm
    • Frequency :
    • The number of cycles per unit time
      • Measured in Hertz (Hz) or Cycles per second (cps)
    • Velocity :
    • How quick the sound travels
    • Distance per unit time
      • Measured in meter / second (m / sec)
  • Properties of a sound wave
    • Sound cannot travel in vacuum
    • Sound energy to be transmitted / transferred from one particle to another
    SOLID LIQUID GAS
  • Velocity
    • The velocity of sound in a particular material is CONSTANT
    • It is the product of DENSITY and ELASTICITY of the material
    • It will NOT change if frequency changes
    • Only the wavelength changes
    • Examples:
    • V Compression in steel : 5960 m/s
    • V Compression in water : 1470 m/s
    • V Compression in air : 330 m/s
    STEEL WATER AIR 5 M Hz
  • Velocity 4 times What is the velocity difference in steel compared with in water? If the frequency remain constant, in what material does sound has the highest velocity, steel, water, or air? Steel If the frequency remain constant, in what material does sound has the shortest wavelength, steel, water, or air? Air Remember the formula  = v / f
  • DRUM BEAT Low Frequency Sound 40 Hz Glass High Frequency 5 K Hz ULTRASONIC TESTING Very High Frequency 5 M Hz
  • Ultrasonic
    • Sound : mechanical vibration
    What is Ultrasonic? Very High Frequency sound – above 20 KHz 20,000 cps
  • Acoustic Spectrum 0 10 100 1K 10K 100K 1M 10M 100m Sonic / Audible Human 16Hz - 20kHz Ultrasonic > 20kHz = 20,000Hz Ultrasonic Testing 0.5MHz - 50MHz Ultrasonic : Sound with frequency above 20 KHz
  • Frequency
    • Frequency : Number of cycles per second
    1 second 1 cycle per 1 second = 1 Hertz 18 cycle per 1 second = 18 Hertz 3 cycle per 1 second = 3 Hertz THE HIGHER THE FREQUENCY THE SMALLER THE WAVELENGTH 1 second 1 second
  • Frequency
    • 1 Hz = 1 cycle per second
    • 1 Kilohertz = 1 KHz = 1000Hz
    • 1 Megahertz = 1 MHz = 1000 000Hz
    20 KHz = 20 000 Hz 5 M Hz = 5 000 000 Hz
  • Sound waves are the vibration of particles in solids, liquids or gases. Particles vibrate about a mean position. One cycle Displacement The distance taken to complete one cycle wavelength  wavelength Wavelength Wavelength is the distance required to complete a cycle.
  • Velocity Frequency Wavelength
  • Frequency & Wavelength 1 M Hz 5 M Hz 10 M Hz 25 M Hz Which probe has the smallest wavelength? SMALLEST LONGEST Which probe has the longest wavelength?  = v / f F  F 
  • Wavelength is a function of frequency and velocity. 5MHz compression wave probe in steel Therefore: or or f V   V   f V  f 
    • Which of the following compressional probe has the highest sensitivity?
    • 1 MHz
    • 2 MHz
    • 5 MHz
    • 10 MHz
    10 MHz
  • Wavelength and frequency
    • The higher the frequency the smaller the wavelength
    • The smaller the wavelength the higher the sensitivity
    • Sensitivity : The smallest detectable flaw by the system or technique
    • In UT the smallest detectable flaw is ½  (half the wavelength)
  • The Sound Beam
    • Dead Zone
    • Near Zone or Fresnel Zone
    • Far Zone or Fraunhofer Zone
  • The Sound Beam NZ FZ Main Beam Distance Intensity varies Exponential Decay
  • Main Lobe Side Lobes Near Zone Main Beam The main beam or the centre beam has the highest intensity of sound energy Any reflector hit by the main beam will reflect the high amount of energy The side lobes has multi minute main beams Two identical defects may give different amplitudes of signals
  • Sound Beam
    • Near Zone
    • Thickness measurement
    • Detection of defects
    • Sizing of large defects only
    • Far Zone
    • Thickness measurement
    • Defect detection
    • Sizing of all defects
    Near zone length as small as possible
  • Near Zone
  • Near Zone
    • What is the near zone length of a 5MHz compression probe with a crystal diameter of 10mm in steel?
  • Near Zone
    • The bigger the diameter the bigger the near zone
    • The higher the frequency the bigger the near zone
    • The lower the velocity the bigger the near zone
    Should large diameter crystal probes have a high or low frequency?
  • Which of the above probes has the longest Near Zone ? 1 M Hz 5 M Hz 1 M Hz 5 M Hz
  • Near Zone
    • The bigger the diameter the bigger the near zone
    • The higher the frequency the bigger the near zone
    • The lower the velocity the bigger the near zone
    Should large diameter crystal probes have a high or low frequency?
  • Beam Spread
    • In the far zone sound pulses spread out as they move away from the crystal
      / 2
  • Beam Spread Edge,K=1.22 20dB,K=1.08 6dB,K=0.56 Beam axis or Main Beam
  • Beam Spread
    • The bigger the diameter the smaller the beam spread
    • The higher the frequency the smaller the beam spread
    Which has the larger beam spread, a compression or a shear wave probe?
  • Beam Spread
    • What is the beam spread of a 10mm,5MHz compression wave probe in steel?
  • Which of the above probes has the Largest Beam Spread ? 1 M Hz 5 M Hz 1 M Hz 5 M Hz
  • Beam Spread
    • The bigger the diameter the smaller the beam spread
    • The higher the frequency the smaller the beam spread
    Which has the larger beam spread, a compression or a shear wave probe?
  • Testing close to side walls