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Ultrasonic Testing

Ultrasonic Testing. دانشگاه آزادواحداهواز دانشکده فنی ومهندسی. Shokoh manesh asghar & Hammori amin supervisor : Dr Moeinifar. Introduction to Nondestructive Testing. Six Most Common NDT Methods. Visual Liquid Penetrant Magnetic Ultrasonic Eddy Current X-ray.

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Ultrasonic Testing

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  1. Ultrasonic Testing دانشگاه آزادواحداهواز دانشکده فنی ومهندسی Shokohmaneshasghar & Hammoriamin supervisor: Dr Moeinifar

  2. Introduction to Nondestructive Testing

  3. Six Most Common NDT Methods • Visual • Liquid Penetrant • Magnetic • Ultrasonic • Eddy Current • X-ray

  4. آزمون فرا صوتي Ultrasonic Test

  5. آزمون‌هاي فرا صوتي كاربرد بسيار گسترده‌اي در تعيين نقص‌هاي دروني مواد دارند. • از اين روش مي‌توان براي تعيين ترك‌هاي زير سطحي نيز استفاده كرد. • آزمون‌هاي فرا صوتي علاوه بر بازرسي قطعات تكميل شده براي بازرسي كنترل كيفيت مراحل مختلف توليد قطعاتي همچون ورقهاي نورد شده نيز بكار مي‌روند. • مباني آزمون فرا صوتي از ايجاد موج‌هاي صوتي توسط يك ضربان سنج استخراج شده است. • روش مدرن بكار گرفته شده امروزي، التراسونيك ناميده مي‌شود كه علت اين نامگذاري كلمه Sona مي‌باشد كه در لاتين به معني صوت است.

  6. سرعت موج : • در حالت كلي هر چه محيط مادي فشرده‌تر باشد، سرعت حركت موج صوتي در آن بيشتر است. بنابراين سرعت حركت امواج صوتي در جامدات بيشتر از سيالات مي‌باشد.

  7. 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)

  8. Wavelength Velocity Frequency

  9. Sound Waves Sound waves are the vibration of particles in solids liquids or gases Particles vibrate about a mean position In order to vibrate they require mass and resistance to change One cycle

  10. Sound cannot travel in vacuum Sound energy to be transmitted / transferred from one particle to another SOLID LIQUID GAS Properties of a sound wave

  11. 5 M Hz STEEL WATER AIR 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

  12. ساختمان پروب : • چندين نوع پروب فرستنده وجود دارد، اما همه انواع آنها داراي كريستالي است كه مستقيماً يا از طريق پوشش محافظ با ماده مورد آزمايش در تماس است. • جنس بلور معمولاً از كوارتز طبيعي، تيتانات باريم، نيوبات سرب و سولفات ليتيم مي‌باشد. ولتاژ پله‌اي كوتاه مدتي به كريستال اعمال مي‌شود. • پروب‌ها ممكن است قائم يا زاويه‌دار باشند.

  13. پروب‌هاي زاويه‌دار : • پروب‌هاي زاويه‌دار براي فرستادن موج‌هاي برشي يا موج‌هاي ريلي به درون قطعه تحت بازرسي طراحي شده‌اند. • ساختمان كلي پروب زاويه‌اي همانند پروب عمودي است با اين تفاوت كه بلور در قطعه پرسپكسي جاسازي شده است. • موج طولي بازگشتي كه در فصل مشترك پرسپكسي - فلز توليد مي‌شود، ممكن است به كريستال برگردد و علائم گمراه كننده‌اي به وجود آورد. براي جلوگيري از اين كار ماده جذب كننده‌اي همچون لاستيك در پروب جاسازي مي‌شود. روش ديگر اين است كه قطعه پرسپكس به گونه‌اي شكل داده شود كه موج برگشتي چندين بار بازتاب شود و انرژي خود را از دست بدهد و از آنجا كه ضريب جذب پرسپكس بالا است، اين امكان وجود خواهد داشت.

  14. پروبهای قائم امواج را با زاویه صفر درجه و به صورت عمود وارد قطعه میکنند .

  15. Sound Waveforms Sound travels in different waveforms in different conditions • Compression wave • Shear wave • Surface wave • Lamb wave

  16. Compression / Longitudinal • Vibration and propagation in the same direction / parallel • Travel in solids, liquids and gases Particle vibration Propagation

  17. Shear / Transverse • Vibration at right angles / perpendicular to direction of propagation • Travel in solids only • Velocity  1/2 compression (same material) Particle vibration Propagation

  18. Frequency 0.5MHz 1 MHz 2MHz 4MHz 6MHZ Compression 11.8 5.9 2.95 1.48 0.98 Compression v Shear • Shear • 6.5 • 3.2 • 1.6 • 0.8 • 0.54 The smaller the wavelength the better the sensitivity

  19. Sound travelling through a material • Velocity varies according to the material • Compression waves • Steel 5960m/sec • Water 1470m/sec • Air 344m/sec • Copper 4700m/sec • Shear waves • Steel 3245m/sec • Water NA • Air NA • Copper 2330m/sec

  20. Surface Wave • Elliptical vibration • Velocity 8% less than shear • Penetrate one wavelength deep Easily dampened by heavy grease or wet finger Follows curves but reflected by sharp corners or surface cracks

  21. SYMETRIC ASSYMETRIC Lamb / Plate Wave • Produced by the manipulation of surface waves and others • Used mainly to test very thin materials / plates • Velocity varies with plate thickness and frequencies

  22. Ultrasonic • Sound : mechanical vibration What is Ultrasonic? Very High Frequency sound – above 20 KHz 20,000 cps

  23. Acoustic Spectrum Sonic / Audible Human 16Hz - 20kHz Ultrasonic > 20kHz = 20,000Hz 0 10 100 1K 10K 100K 1M 10M 100m Ultrasonic Testing 0.5MHz - 50MHz Ultrasonic : Sound with frequency above 20 KHz

  24. 1 second 1 second Frequency • Frequency : Number of cycles per second 1 second 1 cycle per 1 second = 1 Hertz 3 cycle per 1 second = 3 Hertz 18 cycle per 1 second = 18 Hertz THE HIGHER THE FREQUENCY THE SMALLER THE WAVELENGTH

  25. Pg 21 Frequency • 1 Hz = 1 cycle per second • 1 Kilohertz = 1 KHz = 1000Hz • 1 Megahertz = 1 MHz = 1000 000Hz 20 000 Hz 20 KHz = 5 M Hz = 5 000 000 Hz

  26. defect echo Back wall echo initial pulse Material Thk Ultrasonic Inspection defect 0 10 20 30 40 50 Compression Probe CRT Display

  27. 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 Signal from the backwall Bottom / Backwall

  28. The BWE signal Defect signal 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

  29. 0 10 20 30 40 50 60 60 mm The depth of the defect can be read with reference to the marker on the screen

  30. Thickness / depth measurement The closer the reflector to the surface, the signal will be more to the left of the screen B A C 30 46 68 The thickness is read from the screen The THINNER the material the less distance the sound travel C B A

  31. Ultrasonic Inspection initial pulse defect echo Surface distance defect sound path 0 10 20 30 40 50 Angle Probe CRT Display

  32. The Sound Beam • Dead Zone • Near Zone or Fresnel Zone • Far Zone or Fraunhofer Zone

  33. Intensity varies Exponential Decay Distance The Sound Beam FZ NZ Main Beam

  34. The side lobes has multi minute main beams Two identical defects may give different amplitudes of signals Near Zone Side Lobes 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 Main Lobe Main Beam

  35. Near Zone Thickness measurement Detection of defects Sizing of large defects only Far Zone Thickness measurement Defect detection Sizing of all defects 2 D N = 4l Sound Beam Near zone length as small as possible balanced against acceptable minimum detectable defect size

  36. Near Zone

  37. Near Zone • What is the near zone length of a 5MHz compression probe with a crystal diameter of 10mm in steel?

  38. 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

  39. 1 M Hz 5 M Hz 1 M Hz 5 M Hz Which of the above probes has the longest Near Zone ?

  40. Beam Spread • In the far zone sound pulses spread out as they move away from the crystal /2 

  41. Beam axis or Main Beam Beam Spread Edge,K=1.22 20dB,K=1.08 6dB,K=0.56

  42. Beam Spread • What is the beam spread of a 10mm,5MHz compression wave probe in steel?

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