Que5.13. List the colorful destructive and non-destructive styles of testing welded joints. Explain the working of color penetrant testing styles. Answer Types of Testing Destructive testings Non destructive testings Tensile test Bend test Impact test Neck- break test Hardness test Etch test Testing of Welded Joints glamorous flyspeck examination Fluorescent penetrant Stethoscopic test Visual examination Ultrasonic examination Eddy current testing X-ray and- shaft radiography Dye Penetrant Testing 1. It’s a non destructive type testing to descry excrescencies that are open to the face like cracks, seams, stages, lack of bond, porosity, cold wave shuts,etc. 2. In color penetrant test, the explosively coloured red penetrant liquid has a property of percolating into face excrescencies when applied on precautionary or impermeable face. 3. The working way of color penetrant tests are as follows Access drawing Applying inventor check 5.13.1. originally clean the face of the element with a piece of cloth to make it free of dust and dirt. ii. Use a soft line encounter to clean the face of the element from scale, rust, makeup,etc. iii. To remove oil painting and grease from the face spot the cleanser. iv. Now spot the color penetrant adequately to cover the area that has to be tested. Allow eventually( 3 to 5 twinkles) for color to access into the cracks. v. The redundant penetrant on the face must be wiped off by using a shaft gravestone. vi. Again spot the face with the cleaner to remove the remnants of the red color. vii. Spray a chemical( known as inventor) unevenly on the face. This will give a thin indeed subcaste over the face to be audited. This subcaste absorbs the penetrant from the cracks and red spots or lines appear on the face to give a visible suggestion of the excrescencies. viii. The crack if any will be indicated with the red color absorbed by the white spongy. 4. For color penetrant test Que5.14. bandy the principle and working of ultrasonic examinations. Also describe its advantages, limitations and operations. Answer Principle and Working of Ultrasonic examinations 1. Ultrasonic swells are generally generated by the piezoelectric effect and quartz demitasse is used for this purpose. 2. When a high frequence AC current is impressed across the faces of the quartz demitasse, the demitasse will expand during the first half of the cycle and contracts in the coming half cycle and produced a mechanical vibration in the quartz demitasse. 3. The job face that’s to be audited is made fairly smooth by machine or by other processes) so that ultrasonic swells can be efficiently transmitted from the inquiry into the job and indeed small blights can be detected duly. 4. In ultrasonic examination separate examinations, one for transmitting the swells and other to admit them after passage through the welded jobs are used. 5. Before transmitting ultrasonic swells, an oil painting film is handed between the inquiry and job face to insure proper contact between them and better transmission of swells from the inquiry into the face of the object to be tested. 6. For operation, ultrasonic surge is introduced into the essence and the time interval between transmission of the gregarious and event of the incoming signals is measured with a cathode shaft oscilloscope( CRO). 7. Time base of CRO is acclimated similar that the full range of the trace represents the section being examined. 8. As the surge is transferred from the transmitter inquiry, it strikes the upper face of the job and makes a sharp( peak) or pip( echo) at the left hand side of the CRO screen. 9. If job is disfigurement free also this surge will strike the nethermost face of the same, gets reflected and indicated by a pip towards the right hand end of the CRO screen. 10. still, utmost of If a disfigurement is present in between the top and nethermost shells. the ray striking this disfigurement will get reflected from the disfigurement, reach the receiver inquiry and indicate a pip( echo) on the CRO screen before the pip given by the swells striking the far end of the job and returning. 11. The distance of the disfigurement from the face where transmitter inquiry is applied can be determined with the help of a time distance scale in the form of a square surge constantly shown on CRO. Advantages of Ultrasonic examinations 1. This system is presto, dependable NDT. It’s more sensitive to detect excrescencies within the metallic objects than radiography. 2. About0.1 of the distance from the inquiry can be detected for the presence of disfigurement. 3. It involves low cost and high speed of operation. 4. The perceptivity of ultrasonic excrescence discovery is extremely high, being at a outside when using swells of loftiest frequence. Limitations of Ultrasonic examinations 1. Testing face of the job must be base, smooth and clean. 2. professed and trained driver is needed. 3. It can not examine the complex shape or configuration. Applications of Ultrasonic examinations 1. For examining large weldments, castings and forgings for internally disfigurement free portion before carrying out precious machining operations. 2. For examining the moving strips or plates to insure their consistence. 3. For examining fatigue cracks in wheel legs and locomotive axles. 4. For examining rails for bolt- hole breaks. Que5.15. Explain the destructive and non destructive testing. What are the advantages of each? Answer Destructive Testing 1. In destructive testing cargo is applied on the welded joint. 2. distortion takes place on removing the cargo, endless distortion takes place inside the weld instance, means instance is no longer for use. Advantages 1. These tests give the factual data of tensile strength, impact strength, hardness, bend test,etc. 2. These types of tests can be used on all essence. Non Destructive Testing( NDT) 1. It’s also another system of testing welded object to find out the parcels or blights in the weldment. 2. In non destructive testing cargo is applied on welded instance, no endless distortion takes place on removing the cargo, means weld object can be further used. 3. With the help of NDT we can find out the several unnoticeable subsurface blights, it makes weld element more dependable and safe. 4. Although NDT don’t give direct dimension of mechanical parcels but they’re extremely useful in revealing blights in factors that could vitiate their performance when they’re under cargo. Advantages 1. These types of tests bear low original cost. 2. These tests give the correct bitsy structure of object without destroying it. 3. These tests are fast and easy to handle. Que5.17. What’s hardness testing? Explain any bone
system. Answer Hardness Testing 1. Hardness is the mechanical parcels of material. 2. It’s deduced by destructive testing and occasionally it’s attained by a non destructive testing device. 3. During hardness testing face of material deforms slightly. 4. There are several styles available as given below Rockwell hardness test, ii. Brinell hardness test, iii. Vicker hardness test, and iv. Knoop test. Rockwell Hardness Test 1. The Rockwell hardness test is extensively used because of its speed and freedom from particular crimes. 2. This test requires much lower penetrators( sword balls as well as cone- shaped diamond penetrators) and loads that used on Brinell hardness tester. 3. There are two scales on a Rockwell testing machine, B- scale and C- scale. 4. While performing the Rockwell hardness test the following procedure is used i. The test piece is placed on the machine’s test table. ii. The test piece is raised by turning the hand wheel, till it just touches the indenter and the needle on the machine dial reads zero. This indicates that a minor cargo of 10 kg has been applied on the test sample by the machine and ensures that the instance is seated duly. iii. After that a major cargo of 100 kg( for B- scale) or 150 kg( for C- scale) is applied by pressing the coil handed for this purpose. iv. The depth of the indentation is recorded automatically by means of a dial scale. The reading is identified with arbitrary hardness figures. Que5.18. Write a short note on wear and tear test. Also write down the colorful types of wear and tear. Answer Wear Test 1. Wear test is carried out to prognosticate the wear and tear performance and to probe the wear and tear medium. 2. It’s performed to estimate the wear and tear property of a material so as to determine whether the material is acceptable for a specific wear and tear operation. 3. It could be done at colorful situations similar as laboratory test, element simulation test and in- service test. 4. An outfit used for wear and tear testing is nominated as wear and tear tester, tribotester or tribometer. 5. A wear and tear tester will always involve two factors loaded against and fairly moving with each other. The movement can be driven by a motor or by an electromagnetic device. Types of Wear 1. tenacious wear and tear, 2. Abrasive wear and tear, 3. face fatigue, 4. Erosive wear and tear, and 5. erosion and oxidation wear and tear.
