Guided Wave Testing with CIVA

Simulation capabilities for Guided waves include the propagation of ultrasonic beams in planar and tubular waveguides and their interaction with a flaw.

 

Probes

A wide range of UT probes, standard and advanced designs can be handled:

  • Contact (with or without wedge)
  • Single element or phased-array probes (see Phased Arrays section) or EMAT probes (involves a coupling with CIVA ET)
  • Encircling or encircled probes for pipe inspection
  • Different types of solicitations (shear or longitudinal vibration)
  • Different configurations (Pulse-Echo, Pitch-Catch transmission or Pitch-Catch reflection)

 

Example of transducers: contact probe and encircled arrays

 

Specimens

Planar structures and pipe-like structures (with possibly some discontinuities) are considered for guiding waves by CIVA. The specimen may be homogeneous or heterogeneous, taking into account a coating for example. Each medium should be isotropic and linear attenuation laws may be considered for L-waves and T-waves. This is also possible to account for pipes filled with fluid or to compute modes and beams on parts having 2D CAD cross section, such as rails:

 

 
Geometries taken into account by CIVA

 

Phased-Arrays Settings

CIVA allows defining delay laws on different kinds of probes: linear arrays on plates, encircling or matrix arrays on pipes:

  • Independent definition of emitting or receiving elements
  • Variable aperture at emission or reception, for size or position

 

Phased-array probe accounted for by CIVA

 

In the case of pipes, CIVA GWT allows the user to compute delay laws in order to focus on a given point of the pipe, as long as the excitation frequency is lower than the cut-off frequency of mode L(0,3).

 

Visualization of delay laws in CIVA GWT

 

Flaws

Simulation takes into account a flaw perpendicular to the waveguide, rectangular on a plate, sectorial on a pipe, and determines its interaction with the incident guided beam.

 

CIVA GWT flaws

 

In CIVA GWT, 2D geometrical discontinuities, such as a weld, a groove, a transition (varying diameter) or a junction between straight parts, can be handled for echoes prediction. One or several axisymmetrical flaws can then be accounted for in this discontinuity.

 

Examples of geometrical changes, with and without flaws

 

CIVA GWT is also able to compute defect responses from 2D CAD specimens with planar or volumetric flaws through a 3D computation zone.

 

3D computation zone on a 2D CAD specimen

 

Results

Modes computation

A first module computes the dispersion curves associated to the specimen in a given frequency range.
Modal displacements and constraints are computed for each mode at each frequency of the frequencies range.

  • Application: selection of the working frequency range and visualization of the properties of the modes selected for the testing

 

Dispersion curves in CIVA GWT

 

 

Field computation

A second module allows simulating the ultrasonic beam radiated in different cross-sections of the specimen. The modal repartition of the emitted energy is displayed versus the frequency in the bandwidth of the probe. The displacement and constraints are determined in a time range, which allows visualization of the transit of the different waves at each cross-section or the verification of the focusing allowed by a delay law.

  • Application: design of specific probes dedicated to Guided Waves inspection, optimization of the ability for a sensor to select a given mode, or verification of the focusing allowed by a given delay law

 

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Beam computations in CIVA GWT: left: railway track, center and right: beam focusing and corresponding delay law visualization

 

 

Defect response

This module simulates the beam/flaw interaction (or beam/geometrical discontinuity) and predicts the amplitude, waveform and time of flight of the different types of echoes: incident, reflected and mode converted. On a weld, a preview helps the user to estimate the reflection coefficient of the first torsional mode on the weld, depending on the excitation frequency.

  • Application: simulation of a complete Guided Waves testing

 

Configuration and A-scan from CIVA GWT
 
 
A-scan obtained on a flawed 2D CAD (railway track)

 

On a weld, a preview helps the user to estimate the reflection coefficient of the first torsional mode on the weld, depending on the excitation frequency.