Ultrasonic Examination

Ultrasonic testing is an NDT method performed with high frequency sound waves. The sound frequency range that the human ear can detect is 16-20.000 Hz, and most ultrasonic tests are performed at frequencies between 0.5-20 MHz. In this method, sound waves produced by a sound source (usually a piezoelectric crystal) propagate through the material, giving various information about the material. This information can be obtained from the loss of energy (attenuation) of the waves in the material, their speed of movement, their reflection from interfaces or faults (pulse-echo), or the way they transition to the opposite surface (transmission). From the reflected or transmitted sound energy, evaluations can be made about errors or material properties.

The amount of reflected sound energy depends on the surface structure of the reflector and the metallurgical nature of the material. Almost full reflection occurs at metal-gas interfaces, and partial reflection occurs at metal-liquid or metal-solid interfaces. Ultrasonic testing has much greater penetrating power than radiography and allows to locate and size very small defects. From the location and amplitudes of the sound reflections (echoes) observed on the screen of an ultrasonic device, it is possible to determine the locations and sizes of the errors. Optimum reflection is obtained when the errors are perpendicular to the sound beam.


Ultrasonic inspection is used in the detection of internal discontinuities of forged and cast materials, welding inspection of welded productions, rolled sheet, profile, etc. It is frequently used in lamination controls of products, wall thickness measurements of pipelines, storage and pressure tanks, flat products, and building profiles. The technique, place, time and quality levels to be applied are decided by our Level-3 experts in line with customer demands.

Advantage...

 

  • Access from only one side of the material is sufficient.
  • It can be used on many kinds of materials.
  • It is the most suitable method for the detection of planar internal discontinuities.
  • It is quite portable.
  • It has high penetrating ability.
  • Results can be reached instantly.
  • It can be adapted to automatic systems.

Disadvantage...

 

  • Rough surfaces and coarse grained structures (eg Cast Iron) can cause problems.
  • Surface preparation is required.
  • Reference standards and calibration are required.
  • Signals can be difficult to interpret.
  • A high degree of operator experience and reliability is required.