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Chapter 29. Nondestructive Examination. Purposes of Nondestructive Examination • Types of Nondestructive Examination.
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Chapter 29 Nondestructive Examination Purposes of Nondestructive Examination • Types of Nondestructive Examination
All NDE systems involve an energy source, a modification of the energy source by the test specimen, a detection system, an indication and recording system, and an interpretation system.
Borescopesare used to visually inspect difficult-to-reach areas.
PT is used most effectively on nonporous metals, ceramics, glasses, and polymers.
In MT, iron powder accumulates at the leak of the magnetic field, which is caused by a discontinuity in the material.
Discontinuities are most easily detected by MT when they are oriented 90° to the magnetic field.
Pulse-echo, straight-beam UT uses a single transducer to send and receive the ultrasonic waves straight into the test specimen.
Immersion UT uses a focused beam that helps eliminate the front surface dead zone in the test specimen.
Phased-array UT uses a probe consisting of many transducers, which can provide a visual image of a part and its discontinuities.
RTforms a shadowlike image of a test specimen’s internal structure on photographic film.
An ET probe induces eddy currents in the test specimen, which are used to detect interior flaws.
The most common eddy current detection system in ET instruments is a simple bridge circuit.
AE testing records the sound emitted from a specimen’s discontinuities as they are enlarged from stress.
During an AE test, specimens with larger discontinuities fail under less applied load than those with smaller discontinuities.
A number of leak testing methods are available for industrial applications.
A vacuum box creates a small vacuum environment on one side of a tank, which causes air to bubble at the location of any leaks.