Non Destructive Testing methods
- 1. TOPIC: Non Destructive Testing (NDT) PRESENTED BY: Mr. Ruturajsinh Gurav
- 2. Contents • Introduction of NDT • Objectives of NDT • Advantages and Disadvantages of NDT • Types of NDT Methods
- 3. Introduction • NDT has been defined as testing, inspecting or examine the specimen or component without destroyed the material. • Nondestructive testing(NDT), also known as nondestructive examination(NDE) and nondestructive inspection(NDI). • In NDT without loading the specimen to failure we can measure strength of material. • Here the material is not destroyed and will be used after the test. • Now days this method has become a part of quality control process. • This method helps us to investigate crack depth, micro-cracks, strength etc.
- 4. • NDT may be divided into two general groups: I. The first group consists of tests used to locate defects. In this group there are various simple methods of examination such as visual examination, radiography, magnetic, electrical, ultrasonic techniques. II. The second group of NDT consists of those used for determining the dimensional, the physical or mechanical characteristics of a material or part.
- 5. Objectives of NDT • To detect internal or surface flaws; • To avoid failure, prevent accidents and save human life; • To evaluate the physical and mechanical properties of material; • To maintain uniform quality level; • To find out whether the material is suitable for the required purpose; • To check whether proper heat treatment is given to an alloy or a metal;
- 6. Advantages & Disadvantages of NDT Advantages of NDT: • The equipment are easy to handle • Specimen can be re-used • Used on all shapes and forms; castings, weld, electronic assemblies, aerospace, marine and automobile components • Defect can be detected without damaging the component • Method are quick and accurate Disadvantages of NDT: • NDT instruments are very expensive • Defects difficult to find depth of flaw not indicated • Only surface breaking defects can be detected • Surface finish and roughness can affect inspection sensitivity
- 7. Types of NDT method A. Visual inspection B. Liquid penetrant method C. Radiography Testing D. Ultrasonic Testing method E. Magnetic particle method F. Eddy Current (electrical) method
- 8. LIQUID PENETRATION TESTING(LPT): • Liquid penetrant test, also called Dye penetrant test, is a widely applied and low-cost inspection method used to locate surface-breaking defects in all non-porous materials (metals, plastic, or ceramics). • Penetrant may be applied to all non ferrous materials, but for the inspection of ferrous components magnetic-particle inspection is preferred for its subsurface detection capability. • LPT is used to detect casting and forging defects, cracks, and leaks in new product.
- 9. Procedure: • LPT is based upon capillary action, where low surface tension fluid penetrates into clean and dry surface-breaking discontinuities. • Penetrant may be applied to the test component by dipping, spraying, or brushing. • After penetration time has been allowed(5 to 10 minutes), the excess penetrant is removed, a developer is applied. • The developer help to draw penetrant out of the flaw where a visible indication becomes visible to the inspector.
- 11. Dye penetration testing kit
- 12. Advantages Disadvantages Simple to use Surface breaking defect only Inexpensive Surface preparation critical Quick result Post cleaning required More sensitive Little indication of depth Low operator skill Can be used on any non- porous material
- 13. Radiographic Testing: • Radiographic testing is a nondestructive testing method of inspecting materials for hidden flaws by using the ability of short wavelength electromagnetic radiation to penetrate various material. • Either an X-ray machine can be used as a source of photons. • Electromagnetic wavelength less than about 10 nanometers. • X-ray radiography is used in inspecting casting for defects such as blow holes, cracks, shrinkage cavities and slag inclusions. • These defects are of special importance in components designed to withstand high temperatures and pressures employed in power plants, chemical and pressure vessels.
- 14. Working principles: • X-rays are produced in a Coolidge tube when fast-moving electrons strike; a target material; a part of their kinetic energy is converted into X-rays. • The portion of the casting where defects are suspected, is exposed to X- rays. • A cassette containing an X-ray film is placed behind and in contact with the casting perpendicular to the rays. • X-ray penetrate the casting and thus affect the X-ray film. • Since most of the defects like blow holes, porosites, cracks, etc.
- 18. Ultrasonic Testing Method: • Ultrasonic testing, very short ultrasonic pulse-waves with center frequencies ranging from 0.1-15 MHz and occasionally up to 50 MHz are launched into materials to detect internal flaws. • The technique is also commonly used to determine the thickness of the test object. • Ultrasonic testing is often to performed on steel and other metals and alloys, though it can also be used on concrete, wood and composite. • This method used in many industries including aerospace, automotive and other transportation sectors.
- 19. Working principles: • In this system two probes is attached one is transmission probe and another is receiving probe. • Here the transmission probe is placed in contact with the test piece and the receiving probe is placed on the opposite side of the material. • Transmission 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. • 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.
- 20. • 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 transducer and is displayed on a screen. • In the fig. the reflected signal strength is displayed versus the time from signal generation to when a echo was received. Signal travel time can be directly related to the distance that the signal traveled. From the signal, information about the reflector location, size, orientation and other features can sometimes be gained.
- 22. Advantages Disadvantages Rapid result Trained and skilled operator required Sub-surface detection Good surface finish Safe & portable Difficulty on detecting volumetric defect Can detect planer defect Couplant may contaminate Capable to measuring the depth of defects No permanent record
- 23. Magnetic Particle Testing: • Magnetic particle testing is based on the principle that ferromagnetic materials such as iron, steel, nickel and cobalt alloys, • When magnetized will have distorted magnetic fields in the vicinity of material defects.(fig.) • Surface and subsurface flaws, such as cracks and inclusions, can produce magnetic anomalies that can be mapped with the aid of magnetic particles on the specimen surface. • Magnetic particle testing is relatively simple and easy technique, which can reveal defects such as quenching cracks, thermal cracks, seams, laps, grinding cracks, overlaps, fatigue cracks etc.
- 24. Process: • Magnetic particle inspection process consist of magnetizing the component part such as casting, applying magnetic particles on the component and locating the defects. • Continuous method: In this method, the current inducing the magnetic flux in the workpiece to be inspected is allowed to flow while power is applied. The component is placed between two contacts of solid copper clamp. The induced magnetic field runs in the transverse direction, producing condition favourable to the detection of longitudinally disposed cracks. • And also this test is done by Residual & Circular magnetization method.
- 26. Advantages Disadvantages Simple to use Surface or subsurface detection only Inexpensive Magnetic materials only Rapid results No indication of defects depth Little surface preparation required Only suitable for linear defects More sensitive than visual inspection Detection is required in two direction
- 27. Eddy current testing: • The eddy current testing is based on the principle that when an alternating current carrying conductor coil is brought up near a metallic/conductive specimen. • Eddy currents are introduced in the specimen due to electromagnetic inductions. • This eddy currents produce their own magnetic field, which opposes the field of the current carrying coil thereby increasing its resistance. • This coil resistance is measured to determine discontinuities and flaws present in the material. • Whenever, any flaw comes under the current carrying coil, the local eddy current varies in the specimen, this in turn changes the resistance of the coil which actuates a flash light and the position of the flaw can be detected. • This method not used widely.
- 29. Advantages Disadvantages Overall wall-loss and local defects can be detected Only on thin or slightly permeable materials High sensitivity to small defects Gradual defects could be under classified Accurate sizing of defects possible Only basic cleaning of the tubes required
- 30. THANK YOU