Techshore Inspection Services-Kochi-official blog of Techshore Kerala: TECHSHORE INSPECTION SERVICES : NDT : ULTRASONIC TESTING

This method utilizes the highest level of frequency sound waves to conduct tests on the test materials and also to determine the specifications of the defects inside using sound energy, to conduct examinations and make measurements. Ultrasonic inspection can be used for defect analysis, and measure the defect specification and representation of a material of its inner properties, and more. The working principle can be easily understood by observing the schematic diagram below.

A common UT inspection kit consists of many units, some of which are a pulse transmitter or receiver, transducer/probe, and a cathode ray tube display. The pulse transmitter or receiver is an electronic device which is capable of producing high electric energy which is responsible for the equipment to produce the sound energy as well as to receive the reflected energy. Guided by the pulser, the transducer generates high frequency ultrasonic energy. The sound energy is subjected inside the test material, where the sound sound energy is being passed in the form of a sound wave with a crust and thrust. When there is a irregularity (such as a crack) in the sound wave path, a portion of the energy will be bounced back from the irregular surface.

The sound wave which enters into the specimen hits any interface and reflects back .these reflected energy is to be shown in the display. It cant be shown unless its being transformed into a electric energy, this part of action is done by the transducer. In the diagram below, the energy of the reflected sound is displayed from the time which the sound energy is generated to which it is being received. Time taken by the sound can be determined by the distance travelled by the energy. The received energy signal gives us details about the angle at which the defect is positioned, the type of defect, depth ,surface distance, and also beam path of a defect identified

Ultrasonic Inspection is a very useful and capable of doing many things. Advantage to be noted for this method are as follows

It is sensitive to both surface and subsurface discontinuities.
The depth of penetration for flaw detection or measurement is superior to other NDT methods.
Only single-sided access is needed when the pulse-echo technique is used.
It is highly accurate and specific in determining position of a reflector and estimating its size and shape.
Minimal part preparation is required.
Electronic equipment provides instantaneous results.
Detailed images can be produced with automated systems.
It has other uses, such as thickness measurement apart from flaw detection.

Each method in NDT has its own limitations. some of the disadvantage or limitations can be enlisted as follows

It normally requires a coupling medium to promote the transfer of sound energy into the test specimen.
Materials that are rough in surface making the probe contact difficult, irregular of shape, very small in size, not homogeneous or exceptionally thin are difficult to inspect.
Metals like Cast iron and other coarse grained materials are not usually subjected to this test as they transmit a very weak energy through them which is directly related to high signal noise ratio
Linear defects which is aligned parallel to the sound wave may go un notified.
Standards references are required for calibrating the equipment and the characterization of a defect

The above introduction provides a simplified introduction to the NDT method of ultrasonic testing. However, to effectively perform an inspection using ultrasonic sound wave, much more about the method needs to be known.

Wednesday, January 4, 2017

TECHSHORE INSPECTION SERVICES : NDT : ULTRASONIC TESTING

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