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  foton@fotonndt.com   0232 376 92 01

Ultrasonic Testing (UT)

   Ultrasonic Testing (UT) is a nondestructive testing (NDT) method that utilizes sound waves to detect cracks and defects in parts and materials. It can also be used to determine a material’s thickness, such as measuring the wall thickness of a pipe. 

Scientific Explanation
  The high-frequency sound waves sent into the material are reflected if they strike an obstacle on the audio path. Depending on the angle of impact, the reflected signal may or may not come to the receiving probe.
The reflected signal reaching the receiving probe generates an echo indication on the screen of the ultrasonic inspection device. The coordinates of the reflector in the inspection part can be calculated according to the position of the echo. Also the height of the echo gives an idea about the magnitude of the reflector. It may also be possible to comment on the type of reflector by looking at the shape of the echo signal.
Application Areas
  Metallic or non-metallic materials can be used for the detection of expected volumetric errors and crack-type surface defects.

Limitations
If the sound velocity and sound attenuation of the inspection piece show regionally strong changes, the correct assessment is difficult. Examination of materials with too much sound attenuation due to large grain structure or absorption can sometimes be impossible. Specially designed probes should be used for hot inspection surfaces. A sufficiently wide surface should be prepared for the examination. The surface condition directly affects the inspection parameters. Examination of thin parts is relatively difficult. It is not possible to detect planar discontinuities located parallel to the sound beam axis.Usually reference standard blocks are needed.
Inspection
  High frequency sound waves are produced by a piezoelectric crystal in a piece called a probe. The frequency range used in ultrasonic examination of metallic materials can be between 500 kHz and 10 MHz. The appropriate frequency is determined according to the micro-structure characteristics of the inspection piece. When the probe is brought into contact with the inspection surface, a suitable contact fluid (oil, grease, water, etc.) should be used to allow sound waves to penetrate into the material. 

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