CN101441198A - Ultrasonic wave detection method of wind tunnel body structure butt-jointed seam - Google Patents

Abstract

A method for ultrasonic detection of butt welding joint of wind tunnel body, comprises designing hand specimen according to the structure of fusion-welded T-shaped welding joint of the wind tunnel fore-chamber ring connection flange and calibrating the ultrasonic detector; selecting appropriate probe and detection process; detecting by tip diffraction wave method, and verifying by 6dB method and tip maximum echo method; analyzing verified tip reflection wave and tip maximum echo, identifying diffraction echo, and qualitatively and quantitatively analyzing the internal defects of the butt welding joint. By using the invention, the qualitative and quantitative analysis for the welding defects of the fusion-welded T-shaped welding joint of the wind tunnel fore-chamber ring connection flange can be realized, and positioning accuracy for plane position of the detected defect can reach +/-2mm, and the positioning accuracy of vertical position can reach +/-2mm.

Description

A Method for Ultrasonic Testing of Butt Welds in Wind Tunnel Structures

technical field

The invention relates to the defect detection of a butt weld seam of a wind tunnel body structure used for aerospace system tests, and belongs to the field of ultrasonic detection.

Background technique

At present, ray and ultrasonic testing techniques are mainly used for the detection of internal defects of butt welds of steel full fusion welding at home and abroad. During the production process, the T-shaped welded joint of the annular connection flange of the wind tunnel can be detected by radiographic method, but due to the influence of the structure, 100% coverage cannot be achieved, and there is a certain blind area; The full fusion welded T-shaped welded joint of the circular connecting flange in the front chamber of the wind tunnel cannot be inspected due to structural and environmental restrictions. Ultrasonic testing technology is used for the specific situation of the full fusion welded T-shaped welded joint of the annular connection flange in the front chamber of the wind tunnel. However, this type of structure is shown in Figure 1, and the detectable surface is small and small, and there is no testing process for similar structures. For reference, the use of ultrasonic testing technology to detect its internal defects cannot be quantitatively analyzed, and the positioning is not accurate.

There are three methods for ultrasonic detection of the height of the defect itself:

①6dB method: Taking the maximum echo at the end as the starting point, move the sound beam to deviate from the edge of the defect until the echo height decreases by 6dB, and then measure the height of the defect itself according to the position of the probe incident point, the angle of the sound beam, and the length of the sound path;

② End point diffraction wave method: the height of the defect itself is determined by the delay time difference between the diffraction echoes at the two ends of the defect;

③Maximum echo at the end of the ultrasonic method: take the peak echo at both ends of the defect as the base point, and measure the height of the defect itself according to the position of the incident point, sound path, and refraction angle.

Welding defects of steel full fusion welded butt joints mainly include pores, slag inclusions (points, strips), incomplete penetration, incomplete fusion, and cracks. Generally, pores and slag inclusions are classified as volume defects; lack of penetration is classified as linear defects; lack of fusion and cracks are classified as planar defects.

Theoretical Waveforms of Welding Defects in Steel Full Fusion Welded Butt Joints

①Theoretical echo characteristics of volume defects (including pores with smooth surface and slag inclusions with irregular surface)

As shown in Figure 3, the echo amplitude is small, and the echo heights are basically the same when scanning in different directions and angles. When scanning back and forth, left and right, the dynamic waveforms of the echoes are essentially the same, with a highest point and a smooth decline, as shown in Figure 4.

② Theoretical echo characteristics of linear flaws (not penetrated):

When scanning back and forth, the echoes show the echo characteristics of volume defects; when scanning left and right, there are two or more high points, as shown in Figure 5, with a clear indication of the length. When rotating and scanning around, the echo height drops rapidly on both sides of the direction perpendicular to the defect plane, as shown in Figure 6.

③Theoretical echo characteristics of planar defects (such as cracks, planar unfused)

When scanning left and right, front and back, the dynamic waveform of the echo is similar to a linear defect or a volume defect. When rotating and scanning around a defect with a smooth surface, the echo height drops rapidly on both sides perpendicular to the defect plane as shown in Figure 4. When performing a rotating scan on a rough surface defect, the staggered amplitude of the dynamic waveform is shown in Figure 7, which is similar to a volumetric defect; while performing a circular scan, the height of the echo on both sides in the direction perpendicular to the defect plane The changes are irregular, and usually the echo amplitude changes greatly, as shown in Figure 8.

④Theoretical echo characteristics of dense defects (cracks, pores, slag inclusions, etc. exist more or at the same time)

When scanning left and right, the echo waveform is shown in Figure 9, and the envelope formed during scanning is shown in Figure 10.

Contents of the invention

The technical problem of the present invention is: to overcome the deficiencies of the prior art, and to provide an ultrasonic detection method capable of quantitatively and qualitatively analyzing the weld seam defects of the butt joint of the wind tunnel body structure.

The technical solution of the present invention is: a method for ultrasonic testing of seam welds in a wind tunnel body structure, characterized in that it is realized by the following steps:

According to the shape, thickness, size and welding structure of the full fusion welded T-shaped welded joint of the annular connection flange in the front chamber of the wind tunnel, artificial samples are made, and the ultrasonic detector is calibrated using the artificial samples;

(2) Select the probe and detection process according to the thickness and detectable surface of the T-shaped welded joint that needs to be detected;

(3) Determine the quantitative line, evaluation line and waste judgment line for judging the defect of the full fusion welded T-shaped welded joint of the annular connection flange of the front chamber of the wind tunnel;

(4) Utilize the probe and detection process selected in step (2), and use the end-point diffraction wave method to perform ultrasonic detection on the defects of the full fusion welded T-shaped welded joint of the annular connection flange in the wind tunnel antechamber;

(5) Use the 6dB method and the maximum echo method at the end to verify the defect of the T-shaped welded joint of the ring connection flange in the antechamber of the wind tunnel detected in step (4);

(6) Compare the end point reflection wave, end maximum echo and end point diffraction echo obtained in steps (4) and (5) with the theoretical waveform diagram, and combine the quantitative line, evaluation line and waste judgment line determined in step (3) The internal defects of the butt weld of the wind tunnel structure are judged.

In the step (2), a single crystal straight probe is selected directly above the weld seam of the full fusion welded T-shaped welded joint of the annular connection flange in the antechamber of the wind tunnel, and a single crystal angle probe is selected on the side of the weld seam.

The diameter of the frequency chip of the single crystal straight probe is not greater than 14mm, and the single crystal straight probe scans the weld seam and the heat-affected zone during detection.

The horizontal deviation angle of the probe sound beam axis of the single crystal angle probe is not more than 2°. During the detection, the single crystal angle probe needs to perform a zigzag scan perpendicular to the weld on both sides of the weld, and the distance between each movement is not more than Wafer diameter, rotate 10°~15° during the moving process.

For the single crystal angle probe, when the detection thickness is 15-20mm, the angle of the single crystal angle probe is 60°-72°, the K value is K2.0-K3.0, the detection thickness is 20-30mm, and the angle of the single crystal angle probe is 56°～68°, K value is K1.5～K2.5, and K is the parameter of single crystal angle probe.

Determination of quantitative line, evaluation line and waste line in described step (3): single-crystal oblique probe, the curve gain 5dB that the CSK-IIIA test block that ultrasonic tester measurement tester carries produces is the waste line of judgment, the produced The curve attenuation of 3dB is the quantitative line, and the resulting curve attenuation of 9dB is the evaluation line; single crystal straight probe, the evaluation line is φ2mm flat bottom hole, the quantitative line is φ3mm flat bottom hole, and the waste line is φ4mm flat bottom hole.

Compared with the prior art, the present invention has beneficial effects as follows:

(1) The process determined by the present invention when measuring the T-type welded joint of the annular connecting flange of the wind tunnel can realize the positioning of the welding defects of the T-shaped welded joint of the annular connecting flange of the wind tunnel, quantitative analysis;

(2) The present invention calibrates the ultrasonic detector by making artificial samples, so that the ultrasonic detector can more accurately reflect the real situation of the butt joint weld in the actual side test;

(3) The plane position positioning accuracy of defects detected by the present invention can reach ±2mm, and the vertical position positioning accuracy can reach ±2mm.

Description of drawings

Fig. 1 is the structural diagram of the T-type welded joint of the full fusion welding of the annular connection flange of the wind tunnel antechamber of the present invention;

Fig. 2 is artificial sample structural diagram of the present invention;

Fig. 3 is the theoretical echo characteristic diagram of the volume defect of the weld;

Figure 4 is a theoretical dynamic waveform diagram of the formation of volumetric defects when the probe is moved;

Figure 5 is a theoretical dynamic waveform diagram of the formation of linear defects when moving the probe left and right;

Figure 6 is a theoretical dynamic waveform diagram of the formation of linear defects during rotating and surrounding scanning;

Figure 7 is a theoretical echo characteristic diagram of a planar defect in a weld;

Figure 8 is a theoretical dynamic waveform diagram of the formation of planar defects when the probe is moved;

Figure 9 is a characteristic map of the theoretical echo of dense defects;

Figure 10 is a theoretical dynamic waveform diagram of dense defect formation when the probe is moved;

Fig. 11 is a schematic diagram of the detection surface of the T-shaped welded joint of the annular connection flange of the antechamber of the wind tunnel in the present invention;

Fig. 12 is a process flow diagram of the present invention;

Figure 13 is the actual detection volume defect waveform;

Figure 14 is a dynamic waveform diagram of the actual detection of volumetric defects;

Figure 15 is the actual detection of linear defect waveforms;

Figure 16 is a dynamic waveform diagram of the actual detection of linear defects;

Figure 17 is the actually detected dense defect waveform;

Figure 18 is a dynamic waveform diagram of dense defects during the actual detection of moving probes;

Figure 19 is the actual detection area defect waveform;

Fig. 20 is a dynamic waveform diagram of area defects during the actual detection of the moving probe.

Detailed ways

During ultrasonic testing, spatter, welding scars, welding slag, scale, etc. should be removed within the moving area of the probes on both sides of the weld, and the surface roughness should meet the testing requirements, generally Ra≤6.3μm. Use A-type pulse reflection ultrasonic detector, its working frequency range is 1~5MHz, the horizontal linearity error is not more than 1%, and the vertical linearity error is not more than 5%. Coupling agent can choose chemical paste, machine oil, glycerin.

The process flow of the present invention is as shown in Figure 12,

1. According to the structural and geometrical conditions of the fully fusion-welded T-shaped welded joints of the annular connection flange in the wind tunnel antechamber, artificial samples are made. The actual situation; the artificial sample is shown in Figure 2, the material is 20 ^# steel, and the thickness is 30-35mm. The artificial sample simulates the structure of the actual joint, and the detection of the artificial sample can restore the detection of the actual wind tunnel welded joint, which is used to adjust the horizontal linearity and vertical linearity of the ultrasonic equipment.

2. Select the appropriate probe and detection process according to the thickness and detectable surface of the T-shaped welded joint that needs to be detected, and determine the quantitative line, evaluation line and waste judgment line.

A single crystal straight probe is used directly above the weld seam of the full fusion welded T-shaped welded joint of the annular connection flange in the front chamber of the wind tunnel. The frequency chip diameter of the single crystal straight probe is not greater than 14mm. Scan the area. A single-crystal angled probe is selected on the side of the weld. The horizontal deviation angle of the sound beam axis of the single-crystal angled probe is not more than 2°, and there should be no obvious double peaks in the vertical direction of the main sound beam. The K value of the probe should be selected in accordance with: the detection thickness is 15mm ~ 20mm, the selected probe angle is 60° ~ 72° (K2.0 ~ K3.0); the detection thickness is 20 ~ 30mm, the selected probe angle is 68° ~ 56° ( K2.5～K1.5), K is the probe parameter. When testing with an angled probe, the probe needs to perform a zigzag scan perpendicular to the weld on both sides of the weld. The distance between each movement is not greater than the diameter of the chip, and at the same time, it rotates 10° to 15° during the movement.

When using an inclined probe for detection, the sensitivity of the distance-amplitude curve should be determined according to Table 1; when using a straight probe for detection, the sensitivity of the distance-amplitude curve should be determined according to Table 2.

Table 1 Sensitivity of angle probe distance-amplitude curve

Test block type Rating line quantitative line Waste line CSK-IIIA φ1×6-9dB φ1×6-3dB φ1×6+5dB

Among them, the judgment line is also called the scan line. When the curve that appears in the ultrasonic testing process is higher than the judgment line, the inspector is reminded that there may be defects here. If it does not exceed the quantitative line, it means that the weld is qualified; the quantitative line determines the equivalent of the detection curve. If the detection curve exceeds the quantitative line but does not exceed the waste judgment line, the length of the defect must be detected along the direction of the weld. If the length of the defect exceeds the specified value, It is determined that the weld exceeds the standard and is unqualified; if the detection curve exceeds the waste judgment line, it is directly determined that the weld exceeds the standard and is unqualified.

Table 2 Sensitivity of straight probe distance-amplitude curve

Rating line quantitative line Waste line φ2mm flat bottom hole φ3mm flat bottom hole φ4mm flat bottom hole

When using a straight probe for detection, use the large flat bottom of the workpiece to adjust the sensitivity, adjust the gain of the instrument so that the echo height of the bottom surface is 80% of the screen of the ultrasonic tester, record the value of the gain Δ ₁ , and when the defect echo is found, the defect echo Adjust to 80% of the screen of the ultrasonic tester, record the gain value Δ ₂ at this time, calculate the value of Df according to the formula (1), and compare it with the data in Table 2 to judge whether the defect exceeds the standard.

${\mathrm{<span\; class="notranslate">\; \&Delta;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 20</span>}\mathrm{<span\; class="notranslate">\; lg</span>}\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&lambda;X</span>}}{\mathrm{<span\; class="notranslate">\; \&pi;</span>}{{\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 10</span>}\mathrm{<span\; class="notranslate">\; lg</span>}\frac{\mathrm{<span\; class="notranslate">\; x</span>}}{{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

Among them, λ=c/f, X is the defect depth, X _B is the workpiece thickness, c is the longitudinal wave sound velocity, f is the probe frequency, and Df is the defect equivalent.

The value of Df is less than the φ2mm specified by the judgment line, indicating that the weld is qualified; if Df is greater than the judgment line, it reminds the inspectors that there may be defects here. If Df does not exceed the quantitative line φ3mm, it indicates that the weld is qualified; if Df exceeds the quantitative line If it does not exceed the waste judgment line φ4mm, it is necessary to detect the length of the defect along the direction of the weld. If the length of the defect exceeds the specified value, it is judged that the weld exceeds the standard and is unqualified; if Df exceeds the waste judgment line, it is directly determined that the weld exceeds the standard.

For the detection of T-shaped welded joints of the annular connection flange in the front chamber of the wind tunnel, the possibility of detecting various defects should be considered when selecting the detection surface and probes, and parallel scanning along the direction of the weld seam after the weld reinforcement is ground , on both sides of the weld, use basic methods such as front-to-back, left-right, corner, and surround to scan and make the sound beam as perpendicular as possible to the main defects in the welded joint structure.

3. Use the end-point diffraction wave method to conduct ultrasonic detection on the defects of the T-shaped welded joints of the annular connection flanges in the wind tunnel; when measuring, first find the defect echo, and then move the probe to scan the center of the sound beam to detect the defect The upper endpoint reflected echo or the lower endpoint reflected echo. Move the probe back and forth. At this time, the upper endpoint diffraction wave (instrument display depth is H1) or the lower endpoint diffraction wave (instrument display depth is H2) can be observed on the oscilloscope screen immediately before the upper endpoint reflected wave or after the lower endpoint reflected wave. ). The distance ΔH=H2-H1 between the upper endpoint diffracted wave and the lower endpoint diffracted wave is the height of the defect itself.

4. Detection example:

1) Use an angle probe with a K2 frequency of 2.5MHz to detect a workpiece with a thickness of 30mm from the detection surface 1, as shown in position 2 in Figure 11. When using front-to-back and left-right scanning, the echo waveform is shown in Figure 13, and the envelope formed during the scanning is shown in Figure 14, which can be judged as a volume defect. The instrument shows that the depth of the defect is 15mm, which exceeds the waste judgment line It is an excess defect.

2) Use an angle probe with a K2 frequency of 2.5MHz to detect a workpiece with a thickness of 30mm from the detection surface 2, as shown in position 3 in Figure 11. When using front-to-back and left-right scanning, the echo waveform is shown in Figure 15, and the envelope formed during scanning is shown in Figure 16, which can be judged as a linear defect. The instrument shows that the depth of the defect is 12mm, and the length is 25mm. The waste line is judged to be a defect exceeding the standard.

3) Use an angle probe with a K2 frequency of 2.5MHz to detect a workpiece with a thickness of 30mm from the detection surface 2, as shown in position 2 in Figure 11. When using front-to-back and left-right scanning, the echo waveform is shown in Figure 17, and the envelope formed during the scanning is shown in Figure 18, which can be judged as dense defects. The instrument shows that the depth of the defect is 20mm, and the length is 40mm. Exceeding the waste judgment line is an exceeding standard defect.

4) Use a straight probe with a diameter of 14mm and a frequency of 2.5MHz to detect a workpiece with a thickness of 30mm from the detection surface 1, as shown in position 1 in Figure 11. When using left and right scanning, the echo waveform is shown in Figure 19, and the envelope formed during scanning is shown in Figure 20, which can be judged as an area-type defect. The depth of the defect displayed by the instrument is 23mm, calculated according to formula (1) The obtained defect equivalent Df is 4.5mm, exceeding the waste judgment line is an exceeding standard defect.

Parts not described in detail in the present invention belong to the common knowledge of those skilled in the art.

Claims (7)

1. A method for ultrasonic detection of a wind tunnel body structure butt weld, characterized in that it is realized through the following steps: (1) According to the shape, thickness, size and welding structure of the full fusion welded T-shaped welded joint of the annular connection flange in the front chamber of the wind tunnel, make artificial samples, and use artificial samples to calibrate the ultrasonic detector; (2) Select the probe and detection process according to the thickness and detectable surface of the T-shaped welded joint that needs to be detected; (3) Determine the quantitative line, evaluation line and waste judgment line for judging the defect of the full fusion welded T-shaped welded joint of the annular connection flange of the front chamber of the wind tunnel; (4) Utilize the probe and detection process selected in step (2), and use the end-point diffraction wave method to perform ultrasonic detection on the defects of the full fusion welded T-shaped welded joint of the annular connection flange in the wind tunnel antechamber; (5) Use the 6dB method and the maximum echo method at the end to verify the defect of the T-shaped welded joint of the ring connection flange in the antechamber of the wind tunnel detected in step (4); (6) Compare the end point reflection wave, end maximum echo and end point diffraction echo obtained in steps (4) and (5) with the theoretical waveform diagram, and combine the quantitative line, evaluation line and waste judgment line determined in step (3) The internal defects of the butt weld of the wind tunnel structure are judged. 2. The method for ultrasonic detection of seam welds in wind tunnel body structure according to claim 1, characterized in that: said step (2) fully melts the T-shaped welded joint of the annular connection flange in the antechamber of the wind tunnel A single crystal straight probe is used directly above the weld, and a single crystal oblique probe is used on the side of the weld. 3. The method for ultrasonic testing of seam welds in a wind tunnel structure according to claim 2, characterized in that: the diameter of the frequency chip of the single crystal straight probe is not greater than 14 mm, and the single crystal straight probe is in the welding position during detection. Seam and heat-affected zone scanning. 4. The method for ultrasonic testing of seam welds in a wind tunnel structure according to claim 2, characterized in that: the horizontal deviation angle of the probe sound beam axis of the single crystal angle probe is not greater than 2°, and when testing The single crystal angle probe needs to perform a zigzag scan perpendicular to the weld on both sides of the weld, the distance of each movement is not greater than the diameter of the wafer, and it is rotated by 10° to 15° during the movement. 5. The method for ultrasonic detection of butt joint welds in wind tunnel structures according to claim 2 or 4, characterized in that: the single crystal angled probe, when the detection thickness is 15-20 mm, the angle of the single crystal angled probe 60°～72°, K value is K2.0～K3.0, detection thickness is 20～30mm, angle of single crystal oblique probe is 56°～68°, K value is K1.5～K2.5, K is Single crystal angle probe parameters. 6. The method for ultrasonic testing of seam welds in a wind tunnel body structure according to claim 1, characterized in that: the determination of the quantitative line, the evaluation line and the waste judgment line in the step (3): single crystal oblique Probe, ultrasonic tester measurement tester's built-in CSK-IIIA test block, the curve gain of 5dB is the judgment line, the curve attenuation of 3dB is the quantitative line, and the curve attenuation of 9dB is the evaluation line; single crystal straight probe, evaluation The line is a φ2mm flat-bottomed hole, the quantitative line is a φ3mm flat-bottomed hole, and the waste line is a φ4mm flat-bottomed hole. 7. The method for ultrasonic testing of seam welds in wind tunnel structures according to claim 1, characterized in that: the artificial sample in the step (1) is made of steel and has a thickness of 30-35 mm.

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