2. Mechanical - D Group - 8 Enrollment Numbers :- 1.140020119597 2.140020119598 3.140020119599 4.140020119600 5.140020119601 Guided By:- H.N. JOSHI

3. Definition A wide group of analysis techniques used in science and industry to evaluate the properties of a material, component or system without causing damage. Nondestructive examination (NDE) Nondestructive inspection (NDI) Nondestructive evaluation (NDE)

4. Application Areas Aerospace engineering Mechanical engineering Electrical engineering Civil engineering Systems engineering Medicines

5. 5 Methods of NDT Visual Liquid Penetrant Magnetic Particle Eddy Current Ultrasonic X-ray Microwave Acoustic Emission Thermography Laser Interferometry Replication Flux Leakage Acoustic Microscopy Magnetic Measurements Tap Testing

6. 1.NDT increases the safety and reliability of the product during operation. 2.It decreases the cost of the product by reducing scrap and conserving materials, labor and energy. 3.It enhances the reputation of the manufacturer as a producer of quality goods. All of the above factors boost the sales of the product which bring more economical benefits for the manufacturer. 4.NDT is also used widely for routine or periodic determination of quality of the plants and structures during service. 5.This not only increases the safety of operation but also eliminates any forced shut down of the plants. Importance of NDT 6

7. 7 Six Most Common NDT Methods 1. Visual Testing (VT) 2. Dye Penetrant Testing (DPT) 3. Magnetic Particle Testing (MPT) 4. Ultrasonic Testing (UT) 5. Eddy Current Testing (ECT) 6. Radiography Testing (RT)

8. Visual Testing Visual testing is the most basic and common inspection method involves in using of human eyes to look for defects. But now it is done by the use special tools such as video scopes, magnifying glasses, mirrors, or borescopes to gain access and more closely inspect the subject area. 8 Visual Testing Equipments: Mirrors (especially small, angled mirrors), Magnifying glasses, Microscopes (optical and electron), Borescopes and fiber optic borescopes, Closed circuit television (CCTV) systems, Videoscope.

9. Visual Testing Equipments 9 Fig: Advanced Videoscope Fig: Videoscope Fig: Magnifying glass Fig: Borescopes Fig. Microscope

10. Ultrasonic Testing This technique is used for the detection of internal surface (particularly distant surface) defects in sound conducting materials. In this method high frequency sound waves are introduced into a material and they are reflected back from surface and flaws. Reflected sound energy is displayed versus time, and inspector can visualize a cross section of the specimen showing the depth of features. 10

11. A typical UT system consists of several functional units, such as the pulser/receiver, piezoelectric transducer, and display devices. A pulser/receiver is an electronic device that can produce high voltage electrical pulses. Driven by the pulser, the transducer generates high frequency ultrasonic energy. The sound energy is introduced and propagates through the materials in the form of waves. When there is a discontinuity (such as a crack) in the wave path, part of the energy will be reflected back from the flaw surface. The reflected wave signal is transformed into an electrical signal by the piezoelectrical transducer and is displayed on a screen. Basic Principle of Ultrasonic Testing 11

12. Basic Principle of Ultrasonic Testing In the figure below, the reflected signal strength is displayed versus the time from signal generation, when a echo was received. Signal travel time can be directly related to the distance. From the signal, information about the reflector location, size, orientation and other features can sometimes be gained. 12 0246810 crack echo back surface echo initial pulse Oscilloscope, or flaw detector screen plate crack Piezoelectric Transducer

13. A transducer is a device that converts energy from one form to another. Presently, piezoelectric material is commonly used as a basic component of transducers. A piezoelectric element is a crystal which delivers a voltage when mechanical force is applied between its faces, and it deforms mechanically when voltage is applied between its faces. Because of these characteristics piezoelectric element is capable of acting as both a sensing and a transmitting element. Piezoelectric transducers have been conventionally used to convert electric signals into sound wave, or to convert sound wave into electric signals. 13

14. Piezoelectric Transducer 14 Signal wire Piezoelectric element case

15. Advantages of Ultrasonic Testing  Thickness and lengths up to 30 ft can be tested.  Position, size and type of defect can be determined.  Instant test results.  Portable.  Capable of being fully automated.  Access to only one side necessary. 15

16. Limitations of Ultrasonic Testing  The operator can decide whether the test piece is defective or not while the test is in progress.  Considerable degree of skill necessary to obtain the fullest information from the test.  Very thin sections can prove difficult. 16

17. 17 Crack Detection Crack detection is one of the primary uses of eddy current inspection. Cracks cause a disruption in the circular flow patterns of the eddy currents and weaken their strength. This change in strength at the crack location can be detected. Magnetic Field From Test Coil Magnetic Field From Eddy Currents Eddy Currents Crack

18. Two methods of receiving the ultrasound waveform: Reflection Through Transmission

19. Principle: LEFT: A probe sends a sound wave into a test material. There are two indications, one from the initial pulse of the probe, and the second due to the back wall echo. RIGHT: A defect creates a third indication and simultaneously reduces the amplitude of the back wall indication. The depth of the defect is determined by the ratio D/E p.

20. Magnetic particle inspection Part is magnetized. Presence of a surface or subsurface discontinuity in the material allows the magnetic flux to leak, since air cannot support as much magnetic field per unit volume as metals. Ferrous iron particles are then applied to the part. Particles will build up at the area of leakage and form what is known as an indication.

21. Dye Penetrant Inspection Penetrant may be applied to the test component by dipping, spraying, or brushing After adequate penetration time, the excess penetrant is removed, a developer is applied. Developer helps to draw penetrant out of the flaw where an invisible indication becomes visible to the inspector

22. 1.Section of material with a surface-breaking crack that is not visible to the naked eye. 2.Penetrant is applied to the surface. 3.Excess penetrant is removed. 4.Developer is applied, rendering the crack visible.

23. Dye Penetrant Testing of a Boiler 23 At first the surface of the material that is to be tested is cleaned by a liquid. The liquid is called cleaner. Then a liquid with high surface wetting characteristics is applied to the surface of the part and allowed time to seep into surface breaking defects. This liquid is called penetrant.

24. Then another liquid is applied to pull the trapped penetrant out the defect and spread it on the surface where it can be seen. This liquid is called deveoper. 24 Dye Penetrant Testing of a Boiler Two surface cracks After Dye Penetrant Testing there are two surface cracks are Detected.

25. Radiographic Testing Short wavelength electromagnetic radiation (high energy photons) to penetrate various materials. The amount of radiation emerging from the opposite side of the material can be detected and measured

27. Form of results from Radiographic Testing Tube exhibiting no cracking Tube exhibiting light cracking Tube exhibiting moderate cracking Tube exhibiting severe cracking

28. Corrosion detection in pipelines

29. 29 Advantages of Dye Penetrant Testing  This method has high sensitivity to small surface discontinuities.  Large areas and large volumes of parts/materials can be inspected rapidly and at low cost.  Indications are produced directly on the surface of the part and constitute a visual representation of the flaw.  Aerosol spray can make penetrant materials very portable.  Penetrant materials and associated equipments are relatively inexpensive.

30. Limitations of Dye Penetrant Testing 30  Only surface breaking defects can be detected.  Precleaning is critical since contaminants can mask defects.  The inspector must have direct access to the surface being inspected.  Surface finish and roughness can affect inspection sensitivity.  Post cleaning of acceptable parts or materials is required.  Chemical handling and proper disposal is required.

31. Eddy-Current Testing Uses electromagnetic induction to detect flaws in conductive materials.

32. Variations in the phase and magnitude of these eddy currents can be monitored using a second 'receiver' coil, or by measuring changes to the current flowing in the primary 'excitation' coil. Variations in the electrical conductivity or magnetic permeability of the test object, or the presence of any flaws, will cause a change in eddy current and a corresponding change in the phase and amplitude of the measured current.

33. NDT TechniqueNature of defect Ultrasonic TestingSub-surface, interstitial Magnetic Particle Inspection Surface and slightly subsurface discontinuities in ferroelectric materials Dye Penetrant Inspection Surface-breaking defects in all non-porous materials Radiographic TestingSurface, Sub-surface defects Eddy-Current TestingSurface, Sub-surface defects (depending on conductivity)

34. Conclusion NDT techniques provide cost-effective and reliable analysis under realistic conditions. Each NDT technique has certain capabilities and limitations and often more than one technique is used to cover various parts. Increasing availability of robotic scanners improve the speed of testing large surfaces, hence minimizing the testing time.