L35 phased array ultrasound & time of flight diffraction
- 1. M.KARTHIKEYAN ASSISTANT PROFESSOR DEPARTMENT OF MECHANICAL ENGINEERING AAA COLLEGE OF ENGINEERING & TECHNOLOGY, SIVAKASI karthikeyan@aaacet.ac.in ME8097 NON DESTRUCTIVE TESTING AND EVALUATION
- 2. UNIT IV ULTRASONIC TESTING (UT) AND ACOUSTIC EMISSION (AE) 1. Ultrasonic Testing-Principle, 2. Transducers, 3. Transmission and pulse-echo method, 4. Straight beam and angle beam, 5. Instrumentation, 6. Data representation, A/Scan, B-scan, C-scan. 7. Phased Array Ultrasound, Time of Flight Diffraction. 8. Acoustic Emission Technique – Principle, 9. AE parameters, Applications
- 5. Phased array ultrasonic testing (PAUT) probes are composed of several piezoelectric crystals that can transmit/receive independently at different times. This technique can be used to inspect more complex geometries that are difficult and much slower to inspect with single probes.
- 7. ADVANTAGES PAUT can be conducted more quickly than other forms of UT, often within a fraction of a second. It can easily be used for repeat scans because it has a high degree of repeatability. By emitting beams of multiple different angles sequentially, PAUT is able to create detailed and accurate cross-sections of a part. It is able to sweep the beam without moving the probe.
- 8. APPLICATIONS Phased array is widely used for nondestructive testing (NDT) in several industrial sectors, such as construction, pipelines, and power generation. Phased arrays are used to detect and image defects including cracks, voids, and pits caused by corrosion.
- 9. They are used to measure material and coating thickness and to detect changes in material properties. Another common application is to assess the quality of welds and rivets. Phased arrays are also used to inspect joints and interfaces
- 10. TIME OF FLIGHT DIFFRACTION
- 12. A pair of ultrasonic probes is placed on opposite sides of the weld or tested item. One of the probes acts as a transmitter and sends out an ultrasonic pulse that is picked up by the other probe which is the receiver. With an undamaged item, the signals picked up by the receiver probe are from two waves – one wave that travels along the surface (lateral wave) and one that reflects off the far wall (back wall reflection). If there is a flaw, such as crack, there is a diffraction of the ultrasound pulse from the tips of the crack. By measuring the time of flight of the pulse, the depth of the crack can be calculated by trigonometry.
- 13. Time of flight diffraction is an advanced non-destructive testing method used for weld inspection. Time of flight diffraction (TOFD) is one of the most reliable non- destructive testing methods. This ultrasonic method is used in a diverse range of industries including petrochemical, chemical, oil and gas, power generation and fabrication.
- 14. ADVANTAGES Can take place during production work No radiation with this method Inspection data is recorded and can be stored digitally for future reference Inspection results are immediately available Quick inspection method Sensitivity to all weld flaw types including cracks, slag and lack of fusion Accurate sizing of defects
- 15. Polymer probes are compared to conventional ceramic probes are: a) more noisy b) less noisy MCQ - 1
- 16. Ultrasonic NDT at elevated temperatures is a) only possible when the probe is cooled down to less than 60 �C with water or air b) not possible c) possible with special probes up to 800 �C surface temperature MCQ - 2
- 17. The most efficient sound receiver of the piezoelectric material listed is: 1. lithium sulfate, 2. quartz, 3. barium titanate, 4. silver oxide) MCQ - 3
- 18. The most efficient sound transmitter of the piezoelectric material is: 1. lithium sulfate, 2. quartz, 3. barium titanate, 4. silver oxide MCQ - 4
- 19. Acoustic impedance is a material's: (a) (Density)/(velocity) (b) (Density) × (velocity) (c) Refractive index (d) (Density)/(refractive index) MCQ - 5