Reflection sound method

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The reflection sound method , also ultrasonic reflection sound method, is a test method . It is divided into:

Basically, both methods work with a transmitter / receiver head that sends and receives longitudinal waves. When the wave enters the material from the angle probe, a wave transformation occurs. A transverse wave is used for testing. The speeds of sound for both waveforms in the material are different. The longitudinal wave is always faster.

With both methods, a short sound pulse is sent into the material. The impulse is either reflected and gets back to the head or is lost. The distance to the point of reflection can be determined by the transit time of the signal during reflection. The angular position of a discontinuity cannot be determined here either. The reflective behavior or expansion of the discontinuities does. In order to introduce the sound into the test object , the ultrasonic probe must be coupled with a sound-conducting coupling medium. In large-scale testing, water is cheap and environmentally friendly. Individual tests by hand are often coupled with wallpaper paste, coupling paste / gel or oil dissolved in water .

Perpendicular sound method

With the perpendicular sound method, longitudinal waves are radiated vertically into the test object. In most cases, one can expect an echo from the back wall of the test object (which is why it is sometimes called the pulse echo method), the back wall echo. Usually the sound strength of the back wall echo is set to 80% of the display height. With this you can be sure that you will get a sufficiently strong echo from every detectable discrepancy . For testing, the transducer is moved evenly over the surface of the test piece and attention is paid to echoes.

Inclined sound method

In the oblique sound method, too, a longitudinal wave is entered into the test object via a coupling agent. When the sound wave passes into the test object, sound reflection, sound wave refraction and wave transformation take place. The angle at the head is chosen in such a way that all waves except the transformed wave run or exit the test object. The transformed wave is used as a transverse wave for testing. A crack starting from the surface is normally sought . You either look for a crack on the opposite side of the test object, which creates a 90 ° cube-corner mirror with the surface , or - after a reflection on the opposite side - an identical crack on your own surface.