1. ME6019:Non destructive testing and materials Unit 1 - Overview of NDT

2. 2 v 1.2 Session Meta Data AuthorK.S.VIJAY SEKAR Reviewer Version Number1.2 Release Date12.04.2018

3. 3 v 1.2 Revision History Revision DateDetailsVersion no. 12 April 20181.New SSN template applied1.2

4. 4 v 1.2 Session Objectives NDT Versus Mechanical testing Overview of the Non Destructive Testing Methods for the detection of manufacturing defects as well as material characterization Relative merits and limitations Various physical characteristics of materials and their applications in NDT Visual inspection – Unaided and aided.

5. 5 v 1.2 Session Outcomes At the end of this session, participants will be able to –Know what NDT is –Know the various NDT methods –Understand their merits and demerits –Know visual inspection techniques

6. 6 v 1.2 Agenda NDT Versus Mechanical testing Overview of the Non Destructive Testing Methods for the detection of manufacturing defects as well as material characterization Relative merits and limitations Various physical characteristics of materials and their applications in NDT Visual inspection – Unaided and aided.

7. 7 v 1.2 NDT vs Mechanical Testing Nondestructive testing and evaluation is the process of inspecting, testing, evaluating materials for defects and discontinuities, or differences in material characteristics without destroying the function or the application of the part or component. The tested components can be reused again. Mechanical testing is used to determine the physical properties of materials such as impact resistance, ductility, yield and ultimate tensile strength, fracture toughness and fatigue strength. The tested components cannot be reused again.

8. 8 v 1.2 Agenda NDT Versus Mechanical testing Overview of the Non Destructive Testing Methods for the detection of manufacturing defects as well as material characterization Relative merits and limitations Various physical characteristics of materials and their applications in NDT Visual inspection – Unaided and aided.

9. 9 v 1.2 Overview of NDT methods The various NDT techniques are 1.Visual inspection 2.Liquid penetrant testing 3.Magnetic particle testing 4.Thermography 5.Eddy current testing 6.Ultrasonic testing 7.Acoustic emission testing 8.Radiography

10. 10 v 1.2 Visual inspection The earliest method of NDT is visual inspection. By visual inspection through naked eye or through a microscope, important details can be collected on the inspected part. Such results would be useful for future analysis and help decide on the type of NDT to be used for future analysis. Visual inspection can be used for identyfying – cracks on surface, surface deposits, scaling, erosion, discoloration, mechanical damage and missing parts.

11. 11 v 1.2 Liquid penetrant testing A penetrant solution is applied to the surface of a pre cleaned component. The penetrant solution is pulled onto surface-breaking defects by capillary action. The excess penetrant is wiped off the surface. A developer (dry or aqueous) is applied to pull the trapped penetrant back to the surface where it is spread out and indicates the presence of defects. The indication is much easier to see than the actual defect using naked eyes or UV light.

12. 12 v 1.2 Magnetic particle testing In MPT a magnetic field is created in a ferromagnetic material. The magnetic lines of force travel through the ferromagnetic material, exit and re-enter at the poles. Material defects such as crack or voids cannot support all the flux, and will push some of the flux outside of the component. These magnetic particles will be distributed over the surface of the component and will be attracted to areas of flux leakage and produce a visible indication.

13. 13 v 1.2 Thermography In the Thermography method a form of heating or cooling is induced to the part. The movement and distribution of the temperature profile across the part surface is measured. The evidence of cracks or material changes is detected based on the thermal images where even infra red changes can be picked up.

14. 14 v 1.2 Eddy current testing In the ECT method, an alternating current is passed through a coil producing a magnetic field. When this coil is placed near a conductive material, the changing magnetic field induces a secondary current in the material. Such secondary currents called eddy currents travel in closed loops. These eddy currents produce their own magnetic field that can be measured and are used to detect flaws. They are also used to characterize conductivity, and permeability.

15. 15 v 1.2 Ultrasonic testing In UT, a high frequency sound wave is sent into the part using a transducer probe. The travelling sound waves are received by the same transducer or a second transducer. The amount of sound energy transmitted or received and the time the energy is received is analyzed to determine the presence of sub surface cracks and inner flaws. Any changes in material thickness and material properties can also be identified using UT.

16. 16 v 1.2 Acoustic emission testing In AET, minute Acoustic emission signals are detected by growing discontinuities in the part / material under a stimulus such as pressure, stress and temperature. An in depth analysis of these AE signals provide information regarding the location & detection of these discontinuities and also help establish the soundness of the structural integrity.

17. 17 v 1.2 Radiography Radiography uses X-rays and Gamma rays for detection. These X-rays/Gamma rays are used to produce images of objects using film or other detectors that are sensitive to radiation. The part / test object is placed between the radiation source and detector. The thickness and the density of the material that X- rays/Gamma rays must penetrate affects the amount of radiation reaching the detector. This variation in radiation produces an image on the detector that helps detect internal cracks.

18. 18 v 1.2 Agenda NDT Versus Mechanical testing Overview of the Non Destructive Testing Methods for the detection of manufacturing defects as well as material characterization Relative merits and limitations Various physical characteristics of materials and their applications in NDT Visual inspection – Unaided and aided.

19. 19 v 1.2 LPT - Relative merits and limitations Merits: Large areas can be inspected fast, at low cost. Parts with complex geometry can be easily inspected. Test results are evident directly on the surface of the part providing a visual image of the crack or discontinuity. Capital cost is minimal. Limitations: Can detect only surface cracks/defects. Surface preparation is preeminent to cleanse any contaminants which masquerade as defects. The test needs a smooth and nonporous surface. Post cleaning is a must to remove applied chemicals. Multiple operations needed under controlled conditions. Need to handle chemicals carefully.

20. 20 v 1.2 MPT - Relative merits and limitations Merits: Large areas of complex parts can be inspected. Can detect surface and subsurface DEFECTS. Surface preparation is less IMPORTANT than in penetrant method. Test results are produced directly on the surface of the part. Capital costs are low. Limitations: Only ferromagnetic materials can be tested. Alignment of magnetic field and defect is critical to results. Large currents are needed for very large parts. Requires a smooth surface. Sensitivity can be affected by Paint/nonmagnetic coatings. Demagnetization is a must.

21. 21 v 1.2 Thermography - Relative merits and limitations Merits: Thermography finds application in the monitoring of temperature, in boilers, mufflers, reaction towers, refining furnaces, ducts and piping, detection of corrosion in oil tank shell and measurement of oil levels etc., It can be operated directly or in remotely. Can be used to detect a wide range of temperatures. Limitations: Thermal mapping has to be done for trouble shooting. High capital cost.

22. 22 v 1.2 ECT - Relative merits and limitations Merits: ECT can detect surface and closer to surface defects. The test probe need not touch the part. Little part cleaning/ preparation is required. Limitations: Only conductive materials can be inspected. Ferromagnetic materials require special treatment to address magnetic permeability issues. Depth of penetration is limited. Flaws that lie parallel to the probe or coil winding direction can go undetected. Operator Skill and training required is more than other techniques. Surface finish/roughness may affect test results.

23. 23 v 1.2 Ultrasonic testing - Relative merits and limitations Merits: Depth of penetration is superior to other methods. Only one sided access is required. Provides thickness information. Little part preparation/cleaning is required. Limitations: Touch probes/couplants need accessible surfaces. Skill and training required is more than other techniques. Surface finish/ roughness may affect results. Thin parts may be difficult to inspect. Planar defects, parallel to the sound wave may go undetected. Reference standards needed.

24. 24 v 1.2 AET - Relative merits and limitations Merits: Inspection can be done during proof testing/ on-line monitoring of pressure vessels and pipelines. Can detect leakages. The quality can be evaluated during fabrication phase. Monitoring underground ducts/ pipe lines. On-line weld area monitoring. Limitations: Skill and training required is more than other techniques. Surface finish/roughness can affect with inspection. Thin parts may be difficult to inspect.

25. 25 v 1.2 Radiography - Relative merits and limitations Merits: Can be used to inspect all material types. Can detect surface/ subsurface defects. Can inspect complex shapes and multi-layered structures. LITTLE part preparation/cleaning is required. Limitations: Extensive operator training and skill is required. Access to both sides of the structure is required. Orientation of the beam to non-volumetric defects is crucial. Field inspection of large areas can be time consuming. Higher capital costs. Care must be taken for radiation hazard for personnel.

26. 26 v 1.2 Agenda NDT Versus Mechanical testing Overview of the Non Destructive Testing Methods for the detection of manufacturing defects as well as material characterization Relative merits and limitations Various physical characteristics of materials and their applications in NDT Visual inspection – Unaided and aided.

27. 27 v 1.2 Various physical characteristics of materials and their applications in NDT VT - Used for detecting surface deposits, scaling, erosion, discoloration, mechanical damage, missing parts. LPT - Used to identify cracks, porosity, on the surface of a material and have enough volume to trap and hold the penetrant material. MPT - Used to inspect ferromagnetic materials for defects that result in a transition in the magnetic permeability of a material. MPT can detect surface and near surface defects such as cracks and tears, porosity, forging laps, voids.

28. 28 v 1.2 Various physical characteristics of materials and their applications in NDT UT - Used to locate surface/ subsurface defects in many materials including metals, plastics, and wood. It is also used to measure the thickness of materials and characterize material properties based on sound velocity and attenuation. AET – Used for inspection during proof testing and on- line monitoring of pressure vessels, pipelines. Can be used for leakage detection. Quality control during fabrication. Monitoring Underground pipe lines and On- line weld monitoring.

29. 29 v 1.2 Various physical characteristics of materials and their applications in NDT ECT - Used to detect surface and near-surface flaws in conductive metals only. It is also used to sort materials based on electrical conductivity and magnetic permeability, and measures the thickness of thin sheets of metal/ nonconductive coatings. Radiography - Used to inspect any material for surface and subsurface defects. X-rays can also be used to locates and measures internal features, confirm the location of hidden parts in an assembly, and to measure thickness of materials.

30. 30 v 1.2 Agenda NDT Versus Mechanical testing Overview of the Non Destructive Testing Methods for the detection of manufacturing defects as well as material characterization Relative merits and limitations Various physical characteristics of materials and their applications in NDT Visual inspection – Unaided and aided.

31. 31 v 1.2 Visual Inspection Non-destructive type testing Simple,Easy, Quick, Low cost Initial methods for testing Examination with naked eye Illumination of test sample Use of equipment's for inspection

32. 32 v 1.2 Visual inspection techniques Microscope Borescope Endoscope Flexi scope Telescope Holography

33. 33 v 1.2 Microscope A microscope is an instrument used to see objects that are small for the naked eyes. Microscopy is the science of investigating small objects using such an instrument. The first to be invented was the optical microscope which uses light to image the part. Other major types of microscopes are the transmission electron microscope and the scanning electron microscope.

34. 34 v 1.2 Types of microscopes Source: Bresser.com Source: Great scopes.com LCD Type Parts of a microscope

35. 35 v 1.2 Borescope A borescope is an optical device consisting of a rigid or flexible tube with an eyepiece on one end, an objective lens on the other linked together by a relay optical system. The optical system is surrounded by fibers used for illumination of the object. An internal image of the object is formed by the objective lens and magnified by the eyepiece.

36. 36 v 1.2 Types of Borescope Source: Wikipedia Source: Net zero tools Video type Conventional type

37. 37 v 1.2 Endoscope Endoscopy refers to looking inside the anatomy of a part using an endoscope. Endoscopes are inserted directly into the PART. Endoscope can also be used as a borescope in situations where direct line of-sight observation is not possible.

38. 38 v 1.2 Types of Endoscope Source: India mart Source https://www.reichelt.com Wireless type Conventional medical type

39. 39 v 1.2 Flexi scope Flexi-Scope A simple to use microscope which connects easily to any USB port. It can capture high quality images at magnifications of up to 200x; It has a flexible gooseneck Bright, adjustable, LED lighting Easy to use software Compatible with latest OS. Data measurement software.

40. 40 v 1.2 Types of Flexi scope Source: Rutland Inc Source https://www.schoelly.de Multiple heads type Camera type

41. 41 v 1.2 Telescope A telescope is an instrument that helps in the observation of remote objects through electromagnetic radiation. The first known practical telescopes were created using glass lenses. Used in terrestrial applications and astronomy. The reflecting telescope used mirrors. Telescope refers to a wide range of instruments detecting different regions of the electromagnetic spectrum.

42. 42 v 1.2 Types of Telescope Source: Explore scientific Source: Wikipedia commons Refractive type Conventional type

43. 43 v 1.2 Holography Holography is a technique which enables three-dimensional images to be made. Uses laser, interference, diffraction, light intensity recording and suitable illumination of the recording. The image changes as the position and orientation of the viewing system changes in exactly the same way as if the object were still present, thus making the image appear 3D.

44. 44 v 1.2 Holography Source: Semesters.in

45. 45 v 1.2 Summary NDT Versus Mechanical testing Overview of the Non Destructive Testing Methods for the detection of manufacturing defects as well as material characterization Relative merits and limitations Various physical characteristics of materials and their applications in NDT Visual inspection – Unaided and aided.

46. 46 v 1.2 Test your understanding What is the basis for choosing an NDT method for a particular application? (U) Mention two differences between liquid penetrant testing and magnetic particle inspection. (U) Sketch the principle of holography? (R) What is the principle of eddy current testing?(R) Mention two differences between radiography and Thermography method. (U)

47. 47 v 1.2 References Baldev Raj, T.Jayakumar, M.Thavasimuthu “Practical Non-Destructive Testing”, Narosa Publishing House, 2009.