Ultrasonic testing

From Wikipedia, the free encyclopedia

In ultrasonic testing, ultrasonic very short pulse-waves of frequencies ranging from 0.5-15 MHz and occasionally up to 50 MHz are used to detect flaws or characterize materials. It is also commonly used to determine the thickness of the test object - monitoring pipework corrosion being a good example.

Ultrasonic Inspection is often performed on steel and other metals, though it can be used on concrete and other materials. It is a form of non-destructive testing used in many industries including aerospace, automotive and other transportation sectors.

1 How it works
2 Advantages
3 Disadvantages
4 See also
5 External links

[edit] How it works

In ultrasonic testing, a handheld transducer connected to a diagnostic machine is passed over the object being tested. The transducer sends pulsewaves into the surface of the object, returning the "sound" back to the device whenever an imperfection is detected. The screen on the diagnostic machine will show these results in the form of amplitude, and pulse readings, as well as the time it takes for the waves to return to the transducer.

[edit] Advantages

Superior penetrating power, which allows the detection of flaws deep in the part.
High sensitivity, permitting the detection of extremely small flaws.
Only one surface need to be accessible.
Greater accuracy than other nondestructive methods in determining the depth of internal flaws and the thickness of parts with parallel surfaces.
Some capability of estimating the size, orientation, shape and nature of defects.
Nonhazardous to operations or to nearby personnel and has no effect on equipment and materials in the vicinity.
Capable of portable or highly automated operation.

[edit] Disadvantages

Manual operation requires careful attention by experienced technicians
Extensive technical knowledge is required for the development of inspection procedures.
Parts that are rough, irregular in shape, very small or thin, or not homogeneous are difficult to inspect.
Couplants are needed to provide effective transfer of ultrasonic wave energy between transducers and parts being inspected.
Inspected items must be water resistant, when using water based couplants that do not contain rust inhibitors.
Ultrasonic testing cannot be used as an exploritory technique as the shape of the test specimen must be known to properly interpret the output data.