Casting Questions and Answers – Non Destructive Testing

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This set of Casting, Forming and Welding Multiple Choice Questions & Answers (MCQs) focuses on “Non destructive Testing”.

1. In non-destructive testing, sound test used is a very fine and accurate method of detecting flaws in the castings.
a) True
b) False
View Answer

Answer: b
Explanation: Sound test is a very rough test to indicate any flaws or discontinuities in the casting. The casting is suspended by suitable support and tapping is done at the surface of the casting with a hammer that makes a variation in the tone which indicates the existence of flaws. This method does not indicate the exact location and extent of the discontinuity in the casting.
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2. Impact test for detection of defects in the casting is the most crude and unreliable method of non-destructive testing.
a) True
b) False
View Answer

Answer: a
Explanation: In the impact test, the casting is subjected to a blow by the help of a hammer of known weight, which basically strikes or falls on the surface of the casting. Defective castings fail due to the impact of the blow, but this method is very crude and unreliable to the material or casting which is inspected.

3. Which of the following methods of NDT requires leak proofing of casting before inspection?
a) Impact test
b) Visual inspection
c) Sound test
d) Pressure test
View Answer

Answer: d
Explanation: Pressure test used on castings required to be leak proof. In this method, all the openings of the casting are closed and then gas with high pressure is introduced in it. If the casting is having a porosity or another defect, then it can be detected by leaking of gas in the water when the casting is submerged into the water.
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4. Which of the following types of rays is used in radiography for the inspection of castings?
a) X- rays
b) Infrared rays
c) Ultraviolet rays
d) Visible rays
View Answer

Answer: a
Explanation: Radiography uses X-rays, these rays penetrate through the castings and makes a shadow picture on a film which is placed behind the material. These rays have a very short wave length of the order of 0.001 Angstrom. And sometimes gamma rays are also used for the inspection of castings.

5. In radiography, the penetration of rays is much easier with the less density of metal or casting.
a) True
b) False
View Answer

Answer: a
Explanation: The ability of rays to penetrate through the metal mainly depends on the density of metal and they can penetrate more easily where less density of metal is present and it leads to the formation of shadow picture on the film. And any defects in the casting can easily be identified from the shadow picture.
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6. In penetrant testing of NDT, a liquid is penetrated into the cracks of metal by the application of pressure.
a) True
b) False
View Answer

Answer: b
Explanation: Penetrant testing method is generally used for detecting very small surface cracks and it has an advantage over the magnetic particle method that it can be used for any material. A penetrant liquid is used which is drawn into the cracks or voids by means of capillary action. In this method, there is no requirement of pressure.

7. Which of the following methods of inspection uses high frequency of sound waves for the detection of flaws in the castings?
a) Penetrant test
b) Radiography
c) Pressure test
d) Ultrasonic inspection
View Answer

Answer: d
Explanation: Ultrasonic inspection is used to detect defects like cracks and porosity within the interior of the casting or material. This method uses reflection and transmission of high frequency sound waves, which are much higher than the audible range and then these waves are made pass through the casting for inspection.
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8. In ultrasonic inspection, a signal processing technique is used for the accurate indication of porosity in the castings.
a) True
b) False
View Answer

Answer: a
Explanation: A signal processing technique is used for accurately verifying the presence of porosity and also to determine the size and volume fraction. This is mainly done by measuring the changes in frequency by using a broad band transducer, in which the front and the back surface signals of the casting are acquired and digitized.

9. Which of the following terms changes in the eddy current testing method for the detection of defects in the castings?
a) Resistance
b) Impedance
c) Conductivity
d) Capacitance
View Answer

Answer: b
Explanation: In the method of eddy current testing, the impedance of a coil is changes and the coil is brought close to a conductive material which indicates the eddy current induced by the coil and thereby indicates various properties and also the defects of the casting. This method can be used effectively with both ferromagnetic and non-ferromagnetic materials.
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10. There are no restrictions in the eddy current testing method; it can detect defects up to high depth in the castings.
a) True
b) False
View Answer

Answer: b
Explanation: Eddy current inspection is generally restricted to the depth less than 6mm, that’s why it is not as sensitive to small open defects of high depth as liquid penetrant testing (LPT) or magnetic particle inspection (MPI). But it can replace LPT method for detection of surface connected discontinuities.

11. Eddy current testing method can also be used for the evaluation of heat damage to the metal alloys.
a) True
b) False
View Answer

Answer: a
Explanation: Eddy current conductivity testing method is commonly used to assess heat damage of various heat treatable alloys. In order to have a quantitative assessment of heat damaged material, the establishment of conductivity, hardness and strength, a (CHS) relationship is required for each alloy.

12. Acoustic emission testing method is basically employed for the detection of surface discontinuities on the castings.
a) True
b) False
View Answer

Answer: b
Explanation: Acoustic emission testing method, in which solid materials emit sound or acoustic emission when they are stressed mechanically or thermally to the point where deformation or fracturing occurs. This creates elastic waves which can be analyzed by an acoustic emission test system to monitor the condition of the material or casting under stress.

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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn | Youtube | Instagram | Facebook | Twitter