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Ultrasonic Testing Part 4 TWI
Ultrasonic Testing <ul><li>Sensitivity </li></ul><ul><li>Defect sizing </li></ul><ul><li>Scanning procedures </li></ul>
Sensitivity <ul><li>The ability of an ultrasonic system to find the smallest specified defect at the maximum testing range...
Methods of Setting Sensitivity <ul><li>Smallest defect at maximum test range </li></ul><ul><li>Back wall echo </li></ul><u...
Artificial / actual defect Example: The defect echo is set to FSH (Full Screen Height)
Sizing  Methods <ul><li>6 dB Drop </li></ul><ul><li>For sizing large planar reflectors only </li></ul><ul><li>Signal / ech...
6 dB Drop BWE Defect The back wall echo reduced as some part of the beam now striking the defect The echo of the defect ha...
6 dB Drop Now the whole beam is on the defect Defect Back wall echo is now may be reduced or disappeared Plan View
6 dB Drop BWE Defect The probe is moved back until the echo is reduced by half of it’s original height At this point the p...
Sizing Method <ul><li>Maximum Amplitude Technique </li></ul><ul><li>For sizing multifaceted defect – eg. crack </li></ul><...
Maximum Amplitude The whole probe beam is on the on the defect At this point, multipoint of the defect reflect the sound t...
Maximum Amplitude Multifaceted defect : crack The probe is moved out of the defect, the signal disappeared If the edge of ...
Maximum Amplitude The probe is to be moved to the other end of the defect The signals will flactuate as the beam hits the ...
Equalization Technique At this point the whole beam is on the back wall BWE At this point the whole beam is on the defect ...
20 dB Drop Defect BWE When the main beam is on the defect the defect signal is at it maximum If the probe is moved and the...
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Ut P4

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Transcript of "Ut P4"

  1. 1. Ultrasonic Testing Part 4 TWI
  2. 2. Ultrasonic Testing <ul><li>Sensitivity </li></ul><ul><li>Defect sizing </li></ul><ul><li>Scanning procedures </li></ul>
  3. 3. Sensitivity <ul><li>The ability of an ultrasonic system to find the smallest specified defect at the maximum testing range </li></ul><ul><li>Depends upon </li></ul><ul><li>Probe and flaw detector combination </li></ul><ul><li>Material properties </li></ul><ul><li>Probe frequency </li></ul><ul><li>Signal to noise ratio </li></ul>
  4. 4. Methods of Setting Sensitivity <ul><li>Smallest defect at maximum test range </li></ul><ul><li>Back wall echo </li></ul><ul><li>Disc equivalent </li></ul><ul><li>Grass levels </li></ul><ul><li>Notches </li></ul><ul><li>Side Drilled Holes, DAC Curves </li></ul>
  5. 5. Artificial / actual defect Example: The defect echo is set to FSH (Full Screen Height)
  6. 6. Sizing Methods <ul><li>6 dB Drop </li></ul><ul><li>For sizing large planar reflectors only </li></ul><ul><li>Signal / echo reduced to half the height </li></ul><ul><li>Example: </li></ul><ul><ul><li>100% to 50% </li></ul></ul><ul><ul><li>80% to 40% </li></ul></ul><ul><ul><li>70% to 35% </li></ul></ul><ul><ul><li>20% to 10% </li></ul></ul><ul><ul><li>Centre of probe marked representing the edge of defect. </li></ul></ul>
  7. 7. 6 dB Drop BWE Defect The back wall echo reduced as some part of the beam now striking the defect The echo of the defect has NOT yet maximise as the whole beam Not yet striking the defect Plan View
  8. 8. 6 dB Drop Now the whole beam is on the defect Defect Back wall echo is now may be reduced or disappeared Plan View
  9. 9. 6 dB Drop BWE Defect The probe is moved back until the echo is reduced by half of it’s original height At this point the probe centre beam is directly on the edge of the defect The probe is then removed and the centre is marked, and repeat to size the whole defect Plan View
  10. 10. Sizing Method <ul><li>Maximum Amplitude Technique </li></ul><ul><li>For sizing multifaceted defect – eg. crack </li></ul><ul><li>Not very accurate </li></ul><ul><li>Small probe movement </li></ul>
  11. 11. Maximum Amplitude The whole probe beam is on the on the defect At this point, multipoint of the defect reflect the sound to the probe The echo (signal) show as a few peaks Multifaceted defect : crack
  12. 12. Maximum Amplitude Multifaceted defect : crack The probe is moved out of the defect, the signal disappeared If the edge of the beam strike the edge of the defect, a very small echo appears If the probe is moved into the defect, the signals height increase At this point the MAIN BEAM is directly at the edge of the defect One of the peak maximised
  13. 13. Maximum Amplitude The probe is to be moved to the other end of the defect The signals will flactuate as the beam hits the different faces of the defects The probe is moved back into the defect and to observe a peak of the signal maximises Mark the point under the centre of the probe which indicates the edge of the defect The length of the defect is measured Length Remember: The peak which maximised does not have to be the tallest or the first one
  14. 14. Equalization Technique At this point the whole beam is on the back wall BWE At this point the whole beam is on the defect The BWE is at it maximum The Defect echo is at it maximum Defect At the edge of the defect, half of the beam is on the defect, and another half is on the back wall The defect echo is at equal height as the back wall The point is marked as the edge of defect The equalization technique can ONLY be used if the defect is halfway the thickness
  15. 15. 20 dB Drop Defect BWE When the main beam is on the defect the defect signal is at it maximum If the probe is moved and the signal is observed until it is reduced to 10% (20dB Drop), the edge of the beam is on the edge of the defect 10% Using the pre-constructed Beam profile and a plotting card, the defect maybe sized Repeat the above at the other side of the defect 20 dB Beam profile
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