9 data processing of tofd files

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Advanced Analysis Using TomoView > Working with the TOFD Manager Component > Performing DataProcessing of TOFD Files

Performing Data Processing of TOFD Files

Although the functionality and mathematical correctness of all processing algorithms have been

thoroughly checked and validated, no guarantees in terms of flaw detection and sizing performances can

be given. The performance enhancement provided by a processing algorithm is definitely related to the

specificity of each application, and is therefore the responsibility of the user.

Lateral Wave Synchronization

This section describes how to synchronize the lateral wave of a TOFD group.

Calibrate the TOFD group prior to applying the lateral wave synchronization algorithm.

To synchronize the lateral wave of a TOFD group

1. Open a data file (.rdt).

2. Select the Side (B) view on which you want the lateral wave synchronization to be applied.

3. In the Side (B) view, position the reference (red) cursor to select a reference A-scan in an unflawed

zone (see Figure: Selection of a reference A-scan).

4. In the Side (B) view, position the ultrasonic reference cursor and the ultrasonic measurement (blue)

cursor on either side of the lateral wave signal (see Figure: Selection of a reference A-scan).

Appropriate setting of the cursors determines the result of the operation.

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Figure: Selection of a reference A-scan

By default, the lateral wave synchronization is applied to the Complete visible image , but

alternatively, the Slice between Ref. and Meas. cursors option can be selected if appropriate for the

considered TOFD data.

Figure: TOFD data after lateral wave synchronization

Lateral Wave Removal

This section describes how to remove the lateral wave of a TOFD group.

In order to obtain usable results from the lateral wave removal algorithm, it is mandatory to apply the

algorithm to previously synchronized data.

To remove the lateral wave of a TOFD group

5. In the TOFD Manager dialog box, in the Lateral Wave Processing group box, click Set Reference.

6. Click LW Synchronization.

7. In the menu, select View > Contents and display the newly created LWS. The lateral wave is now

synchronized (see Figure: TOFD data after lateral wave synchronization).

1. In the menu, select View > Content and display the lateral wave synchronized data.

2. In the Side (B) view, position the scan reference (red) cursor to select a reference A-scan in an

unflawed zone (see Figure: Selection of reference A-scan). If the selection of the reference A-scan is

correctly performed prior to the lateral wave synchronization, this operation does not need to be

repeated.3. In the Side (B) view, position the ultrasonic reference cursor (red) and the ultrasonic measurement

cursor (blue) on either side of the lateral wave (see Figure: Selection of reference A-scan). If the lateral

wave signal shows a lot of variation, it is important to position the cursors at least around the first




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Figure: Selection of reference A-scan

By default, the lateral wave removal is applied to the Complete visible image , but alternatively the

Slice between Ref. and Meas. cursors option can be selected if appropriate for the considered TOFD

data.

oscillation of the lateral signal.

4. In the TOFD Manager dialog box, in the Lateral wave processing group box, click Set Reference.

5. Click LW Removal.

6. In the menu, select View > Contents and display the newly created LWR. The lateral wave is now

removed (see Figure: TOFD data after lateral wave removal).




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Figure: TOFD data after lateral wave removal

SAFT Processing

The synthetic aperture focusing technique (SAFT) is a computer enhanced imaging technique for thedetection and characterization of discontinuities. The technique takes advantage of the nonlinear phase

shift of a reflection as a discontinuity is linearly scanned. Improved lateral resolution and a higher signal-

to-noise ratio are achieved by using this phase shift, mathematically simulating the focusing of an

ultrasonic lens that is focused on every point in an inspected part.

The SAFT algorithm can be applied either to raw TOFD data or to processed TOFD data. It is the

responsibility of the data analyst to select the best combination for a given application.

To apply the SAFT algorithm

1. Select the Side (B) view on which you want to apply the SAFT algorithm.

2. In this Side (B) view, perform the following procedure in order to select the adequate aperture to be

used for the SAFT algorithm:

a) Zoom in on a zone of interest containing a punctual TOFD indication (see Figure: Definition of the

aperture), showing the typical parabolic shape.

b) Position the reference and measurement cursors on either side of the flight-time minimum of the

indication, so that the indication remains clearly visible at the selected scan axis positions; the

SAFT algorithm tends to smoothen out and eventually erase indications if too large an aperture is

used.




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Figure: Definition of the aperture

3. The SAFT aperture as defined by the positions of the cursors is displayed in the TOFD Manager dialog

box, in the Focalization process group box.

4. In the TOFD Manager dialog box, in the Focalization process group box, click SAFT.

5. In the menu, select View > Contents and display the newly created SAFT. The SAFT algorithm has

been applied (see Figure: Overview of a SAFT ultrasonic image)




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Figure: Overview of a SAFT ultrasonic image

As the SAFT algorithm involves averaging, which might tend to smoothen out high amplitudes, the

use of a higher Software Gain value could be helpful to optimize the visualization of the processed

data.


9 data processing of tofd files

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