NON DESTRUCTIVE TESTING A PRESENTATION OVER NON DESTRUCTIVE TESTING Prepared by :- ANUJ SHARMA 4th year Mechanical engg.

Non Destructive Testing Nondestructive testing (NDT) has been defined as comprising those test methods used to examine an object, material or system without impairing its future usefulness. Used for 100% checking of material in a production quality control system.

Characteristics of NDT Applied directly to the product Tested parts are not damaged Various tests can be performed on the same product Specimen preparation not required Can be performed on parts that are in service Low time consumption Low labour cost

NDT Methods Visual Inspection Liquid penetrant method Ultrasonic Inspection Radiography methods Eddy current testing Magnetic particle testing

1 Visual Inspection Most basic and common inspection method. Tools include fiberscope, borescopes, magnifying glasses and mirrors. Portable video inspection unit with zoom allows inspection of large tanks and vessels, railroad tank cars, sewer lines. Robotic crawlers permit observation in hazardous or tight areas, such as air ducts, reactors, pipelines.

2. Liquid Penetrant Method This method is frequently used for the detection of surface breaking flaws in non- ferromagnetic materials. A liquid with high surface wetting characteristics is applied to the surface of the part and allowed time to seep into surface breaking defects. The excess liquid is removed from the surface of the part. A developer (powder) is applied to pull the trapped penetrant out the defect and spread it on the surface where it can be seen. Visual inspection is the final step in the process. The penetrant used is often loaded with a fluorescent dye and the inspection is done under UV light to increase test sensitivity.

Liquid Penetrant Method

3. Ultrasonic Flaw Detection This technique is used for the detection of internal and surface defects in sound conducting materials. High frequency sound waves are introduced into a material and they are reflected back from surfaces or flaws. Whenever there is a change in the medium, the ultrasonic waves are reflected. Thus, from the intensity of the reflected echoes, the flaws are detected without destroying the material.

Principle & Block Diagram of UT

4. X-Ray Radiography X-rays are passed through the specimen under inspection and it is differentially absorbed by the specimen. The transmitted x-rays are received by the photographic film and the film is developed. The dark and light shadows reveal the defects present in the specimen and hence the defects are defected.

Inspection through Radiography X-ray film

5. Eddy Current & Electro-Magnetic Methods Eddy current technique are for the detection of surface or subsurface flaws, conductivity measurement and coating thickness measurement. In Eddy current testing, a coil carrying AC current is placed closed to the component surface. When the eddy current flows through the metal the crack is detected as the change in Impedance.

Inspection through Eddy Current

6. Magnetic Particle Crack Detection This method is suitable for the detection of surface and near surface discontinuities in magnetic material, mainly ferritie steel and iron. The part is magnetized. Finely milled iron particles coated with a dye pigment are then applied to the specimen. This indication can be visually detected under proper lighting conditions.

Inspection through Magnetic Particle Crack Detection

Uses of NDT To detect internal or surface flaws To measure the dimensions of materials To determine the materials’ structure To evaluate the physical and mechanical properties of materials To avoid failures, prevent accidents and save human life; To make a profit for the user To ensure customer satisfaction and maintain the manufacturer's reputation To aid in better product design To control manufacturing processes To lower manufacturing costs To maintain uniform quality level

Area of Application Mechanical Engineering Aerospace Engineering Civil Engineering Electrical Engineering Industrial & Manufacturing Engineering Systems Engineering Medicine Forensics Art

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