Preliminary Study on the Application of Ultrasonic Phased Array Inspection Technology in the Welding Seam Inspection of Wind Turbine Tower

2.
One set of ultrasonic phased array equipment, one set of TOFD flaw detection equipment, one set of DR flaw detection equipment, one set of ADT automatic analysis, one set of automatic scanner, one tape measure, one marker pen
.

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Experimental steps of ultrasonic phased array:

1.
Using 5MHZ, 16-chip phased array probes, placed on the left and right sides of the weld respectively;

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The wedge adopts a central incident angle of 55 degrees;

3.
The focus law adopts sector scanning, the detection angle is 40°~70°, the number of chips is 16 without focusing, the probe is offset by 22mm from the center of the weld, and the scanning speed is 118mm/S
.

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3, Ultrasonic phased array experiment results:

1.
The test results are shown in Figure 1~Figure 4
.

Figure 1: The probe is placed on the left side of the weld (referred to as PA1)

Figure 2: The probe is placed on the right side of the weld (referred to as PA2)

2.
After magnifying the local position detected in Figure 1 and Figure 2, the direction of the defect can be clearly seen, showing a continuous strip, and PA1 and PA2 can find the defect
.

Figure 3: Magnified view of defects detected by PA1

Figure 4: Magnified view of defects detected by PA2

In order to ensure the credibility of the data, the ADT automatic analysis software is used to fuse the PA1 and PA2 data together.
The results of the analysis data list are as follows:

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4, TOFD test results:

This TOFD test uses a 7.
5MHZ probe, a 70-degree wedge, and PCS=112mm
.

Figure 5: TOFD inspection complete image

Considering the contrast with ultrasonic phased array detection, the image of TOFD detection is enlarged
.

Figure 6: TOFD partial enlarged image

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5.
DR experiment results:

Considering the contrast with ultrasonic phased array detection, the image of DR detection is enlarged
.
See Figure 7~9
.

Figure 7: DR partial enlarged image

Figure 8: DR partial enlarged image

Figure 9: DR partial enlarged image

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2 Description of test results

1.
Defect description:

The length of the weld defect, the reflected wave amplitude, and the height of the weld are all exceeding the standard, and the nature of the defect is that there is no fusion between layers; the length of the defect is less than 10mm
.

2.
Reason analysis:

(1) The welding speed of the welder is too fast, and the welding slag does not completely rise to the surface of the molten iron before it cools and solidifies;

(2) After each layer is welded, the slag is not clean;

(3) The problem of the welder's welding technique resulted in the incomplete fusion of the groove between the layers
.

3.
Comparison of three detection methods:

(1) Detection speed efficiency: Ultrasonic phased array and TOFD take more time than DR in the early parameter setting, and the on-site detection efficiency is higher than DR;

(2) Imageability: TOFD is poor in the direction of defects, and DR needs to be improved in terms of fog.
The ultrasonic phased array can clearly see the continuous direction of defects from the B and C scans;

(3) Quantitative and qualitative: TOFD's judgment of its own height is superior to ultrasonic phased array and DR
.
Ultrasonic phased array and DR are superior to TOFD in judging the length of defects
.
The ultrasonic phased array is superior to DR and TOFD for determining the position of the weld where the defect is located
.
Qualitatively, ultrasonic phased array is superior to DR and TOFD
.

4.
Problems found in testing and solutions:

(1) The ultrasonic phased array adopts the pulse echo method, and the repeatability experiment is very different.
The defect DB value of each scan is different.
The author found that the main reason is that the scan offset is different during walking
.

Solution: Use an electric scanner, which can also be used in the operation and maintenance of the welding seam of the wind turbine tower.
In the experiment, it is found that after the electric scanner is used, the horizontal and vertical walking error can be controlled within ±1mm
.
It can solve the problem of scanning offset
.

(2) It is often difficult to make quantitative judgments on defects
.
Definition of A-scan view and B-scan view, and selection of measurement cursors and references
.

Solution: Use the manufacturer's ADT automatic analysis software, which can well assist in analysis and judgment
.

(3) For judging the height of the defect, the -6dB method is often used to measure on the S-scan, and the measurement result is often larger than the actual one
.

Solution: tofd can detect the height of the defect itself well
.
A splitter is used to separate two from the ultrasonic phased array channel for TOFD detection
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Thus, TOFD and ultrasonic phased array are loaded on the scanner together for one-time detection
.

Three, the end

The wind power tower tube bears a large unit load and wind load during operation ^{[ 3 ]}
.
Tower down accidents warn us from time to time
.
The quality of the weld seam is a link that cannot be ignored
.

Ultrasonic phased array adopts multiple wafers and multiple angles, which has great advantages in terms of defect orientation and quantification
.
Participating in and developing the application of ultrasonic phased array technology in wind power operation and maintenance has great prospects
.

references

[1] Olympus PAUT training materials p 4

[2] Ultrasonic Phased Array Inspection Application National Defense Science and Industry April 2010 P3

[3] The application of TOFD detection technology in the welding seam detection of wind turbine towers Shandong Electric Power Technology P4