Beam characterization of immersion probe on solid inclusions and an infinite plane

Before making an ultrasonic inspection with a given probe, it is important to characterize the beam in order to :

  • verify proper functioning of the probe,
  • determine its useful zone
  • and ensure reproducibility of the measurements.

The characterization of the probe's beam can be performed by measuring the echoes of reference reflectors (Side Drilled Holes or Flat-Bottom Holes (FBH)) placed at different depths in a calibration specimen.

In the case of immersion probes, another method for characterizing the radiated ultrasonic field involves mapping the echo of a small solid target placed in water. It is then possible to plot the axial and transverse profiles of the acoustic beam and to determine its characteristics: near field limit, dimension of the focal length and focal spot. Furthermore, the central frequency of the transducer and its bandwidth can be determined from the spectrum of the echo of a reference reflector placed in water (infinite plan reflector, for example) far from the probe.

It is important that CIVA correctly predicts :

  • the echoes of SDHs and FBHs which are placed in a steel component
  • the echoes of steel inclusions
  • the echoes of an infinite plan placed in water.

Previous experimental characterization studies dealt with SDHs and FBHs. This study consists in evaluating the predictions of calculation models available in CIVA for inclusions and infinite plan in immersion.

To do so, experimental cartographies of the acoustic beam of immersion probes realised for steel inclusions and an infinite plan in water were compared with the predictions of CIVA with different calculation models (SOV model, Separation Of Variables, with or without plane wave approximation and the specular model).

Inclusions of different diameters were used in order to :

  • study the effect of diameter on the measurements of the probe's beam characteristics
  • identify the boundaries of the various models for echoes calculation of an inclusion into water.

The experimental  beam characteristic (near field limit, the focal spot size and focal length) and the experimental characteristics of the probe signal (central frequency and bandwidth) were compared to those of the simulations.

The validation has been carried out with

A summary of essential information about the SOV, Specular and complete SOV model is available HERE