An ultrasonic testing device and method for composite material circular tubes

Abstract

This invention belongs to the field of nondestructive testing technology, and particularly relates to an ultrasonic testing device and method for composite material circular tubes. A support mechanism is located at the bottom of a water tank. The left and right sides of the support mechanism are connected to a first clamp and a second clamp via rotating shafts. The first clamp has an axial through-hole, within which a reflector clamp is installed. The reflector is fixed by the second clamp and the reflector clamp. The reflector is fitted inside the composite material circular tube. The composite material circular tube with the reflector is submerged in water. An X-axis scanning bridge is installed above the water tank along the axial direction of the composite material circular tube. A Z-axis scanning bridge is installed vertically on the X-axis scanning bridge. The Z-axis scanning bridge can move along the X-axis scanning bridge. A probe is installed at the lower end of the Z-axis scanning bridge, submerged in water. Ultrasonic waves are emitted from the probe towards the composite material circular tube, reflected by the reflector, and then passed back through the composite material circular tube to be received by the probe.

Description

Technical Field

[0001] This invention belongs to the field of nondestructive testing technology, and particularly relates to an ultrasonic testing device and method for composite material circular tubes. Background Technology

[0002] Composite laminated cylindrical tube products require inspection for defects such as delamination, inclusions, and porosity, as well as porosity evaluation, and often involve multiple layers. Conventional ultrasonic testing techniques are inefficient and cannot accurately assess porosity.

[0003] Existing methods include manual contact methods, but achieving good coupling is difficult and therefore unsuitable for porosity evaluation. Conventional pulse-echo C-scan detection has a detection blind zone, easily leading to missed detections. For flat specimens, reflector methods are often used to determine the attenuation coefficient of composite materials or for defect imaging detection, such as the attenuation coefficient determination method used in DOI:10.11973 / wsjc201811011, "Factors Affecting the Attenuation Coefficient of Ultrasonic Testing of Porosity in Composite Materials." However, there is still no effective automated defect imaging detection method for tubular composite products. Summary of the Invention

[0004] The purpose of this invention is to provide an ultrasonic testing device and method for composite material circular tubes, enabling porosity evaluation and automated defect imaging detection of tubular laminated structures.

[0005] Technical solution:

[0006] An ultrasonic testing device for composite material circular tubes includes: a support mechanism, an X / Y / Z axis scanning bridge, a probe, a cylinder, a first clamp, a second clamp, a reflector clamp, and a reflector.

[0007] The support mechanism is located at the bottom of the pool. A cylinder is located on the left side of the support mechanism, and the cylinder is connected to a second clamp via a rotating shaft. The second clamp is conical. The right side of the support mechanism is connected to a first clamp via a rotating shaft.

[0008] The first chuck has an axial through hole inside, and a reflector chuck is installed in the through hole; a reflector retaining spring is connected between the through hole inside the first chuck and the reflector chuck, and the reflector chuck extends and retracts axially under the action of the reflector retaining spring; both the first chuck and the reflector chuck are conical.

[0009] One end of the composite material tube and the reflector tube are fitted onto the second clamp, and the other end is fitted onto the first clamp and the reflector tube clamp, respectively. The cylinder drives the second clamp to move, thereby clamping the composite material tube and the reflector tube. The reflector tube is fitted inside the composite material tube.

[0010] A composite material cylindrical tube fitted with a reflector is submerged in water;

[0011] An X-axis scanning bridge is installed above the water tank along the axial direction of the composite material circular tube; a Y-axis scanning bridge is installed on the X-axis scanning bridge along the horizontal and vertical directions; a Z-axis scanning bridge is installed on the Y-axis scanning bridge along the vertical direction; the Z-axis scanning bridge can move along the X-axis and Y-axis scanning bridges.

[0012] A probe is installed at the lower end of the Z-axis scanning bridge. The probe is immersed in water and emits ultrasonic waves into the composite material tube. The reflected ultrasonic waves are then received by the probe after being reflected by the reflector tube.

[0013] Furthermore, the device also includes: a motor and a synchronous belt;

[0014] The motor is located at one end of the X-axis scanning bridge; the motor drives the chuck to rotate via a synchronous belt, thereby driving the composite material tube to rotate.

[0015] An ultrasonic testing method for composite material circular tubes, the method being implemented using the aforementioned device, and the method comprising the following steps:

[0016] Step 1: Clamp the reflector tube, adjust the level of the support mechanism, and adjust the parallelism between the reflector tube busbar and the X-axis scanning bridge;

[0017] Step 2: Use a focusing probe to scan the reflector tube 100%, adjust the gain of the ultrasonic instrument so that the echo amplitude from the reflector tube is 80% of the full scale on the screen, and record the gain at this point as 2A. 反 ;

[0018] Step 3: Place the reflector tube inside the composite material tube and clamp the composite material tube and reflector tube together; scan the composite material tube to find the thinnest area of ​​the composite material tube where the maximum secondary penetration reflection echo is found, and adjust the gain of the ultrasonic instrument so that the amplitude of the maximum secondary penetration reflection echo is 80% of the full scale of the screen. Record the gain at this point as 2A. 管 And calculate 2Ai, 2Ai = 2A 管 -2A 反 ;

[0019] Step 4: Repeat steps 2 and 3 for all composite material tubes to be tested, and take the minimum value among all 2Ai as the zero porosity benchmark value of the thinnest part of the composite material tube, denoted as 2Amin;

[0020] Step 5: Calculate the ultrasonic attenuation 2A corresponding to the acceptance standard for the porosity of the thinnest part of the composite material circular tube. 验 ;

[0021] Step Six: Set the ultrasonic instrument gain to 2A. 反 +2Ai+|2A 验As a scanning sensitivity, the C-scan color palette is set to 5 levels of grayscale display; 100%-80% grayscale is black, 80%-60% is dark gray, 60%-40% is gray, 40%-20% is light gray, and 20%-0% is white.

[0022] Using the pre-set sensitivity and color palette, C-scan imaging was performed on all the composite material cylindrical tubes to be inspected.

[0023] Furthermore, in step one, the process of adjusting the level of the support mechanism is as follows:

[0024] Adjust the lifting limit screws on the left and right sides of the support mechanism to adjust the position of the probe in the X and Y axis directions. The Y axis, X axis, and Z axis form a right-hand coordinate system that is perpendicular to the paper. Obtain the maximum reflection signal at both ends of the reflector. If the water path of the maximum reflection signal at both ends of the reflector is equal, it is considered that the support mechanism has been adjusted to be level. Otherwise, continue to adjust the lifting limit screws.

[0025] Furthermore, in step one, the parallelism adjustment process between the reflector busbar and the X-axis scanning bridge is as follows:

[0026] The support mechanism is equipped with front and rear limiting screws at both ends. The probe is moved along the Y direction at one end of the reflector tube to find the maximum echo, and then the probe is moved along the X axis at the position of the maximum echo. The reflected echo is continuously observed. If the amplitude of the reflected echo is inconsistent, the busbar of the reflector tube is not parallel to the X-axis scanning bridge. The other end of the support mechanism is adjusted back and forth until the amplitude of the reflected echo is consistent.

[0027] Furthermore, in step five, the ultrasonic attenuation is 2A. 验 The calculation formula is as follows:

[0028] 2A 验 (dB)=40(N-1)log(1-S / S0)

[0029] Where N = the equivalent number of carbon cloth layers N = n1 × F1 + n2 × F2;

[0030] n1 = number of bidirectional fabrics, n2 = number of unidirectional fabrics;

[0031] F1 = bidirectional distribution factor, F2 = unidirectional distribution factor;

[0032] S / S0—Porosity (%) allowed by acceptance criteria.

[0033] Furthermore, in step six, the ultrasonic attenuation corresponding to black is less than [2A]. 验 [], [] indicates integers, and the dark gray area corresponds to the ultrasonic attenuation range of [2A]. 验 2A 验-2.5dB); the gray area corresponds to the ultrasonic attenuation range of [2A]. 验 -2.5dB, 2A 验 -6dB); the light gray color corresponds to the ultrasonic attenuation range of [2A]. 验 -6dB, 2A 验 -12dB); the white area corresponds to an ultrasonic attenuation range greater than or equal to 2A. 验 -12dB;

[0034] The porosity range corresponding to different layups is calculated based on the ultrasonic attenuation range corresponding to the five gray levels.

[0035] Furthermore, in step six, the set C-scan color palette is used to scan all the composite material tubes to be inspected; the porosity of the composite material tubes is judged according to the gray level corresponding to the scanning result; and the degree and size of the porosity non-compliance are judged according to the gray level.

[0036] Furthermore, step six also includes: if the porosity qualification standard corresponding to a certain layup method is included in the porosity range corresponding to a certain gray level, then the ultrasonic instrument gain is readjusted and scanning imaging is performed so that the porosity qualification standard corresponding to the corresponding layup method is located at the boundary line between the porosity ranges corresponding to the two gray levels.

[0037] The advantages of this invention are:

[0038] This invention employs a point-focusing probe with a small beam diameter (approximately 1 mm), enabling the detection of small internal defects (3 mm). The water immersion reflector detection method effectively improves coupling performance, is unaffected by ply variations, has no blind spots, and allows for automated imaging detection, simultaneously evaluating defects and porosity. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of an ultrasonic testing device for composite material circular tubes.

[0040] Figure 2 This is a diagram illustrating sensitivity adjustment;

[0041] The components include: 1. Motor; 2. Synchronous belt; 3. Support mechanism; 4. X-axis scanning bridge; 5. Z-axis scanning bridge; 6. Probe; 7. Clamp one; 8. Reflector circlip; 9. Reflector clamp; 10. Circlip fixing screw; 11. Reflector; 12. Composite material round tube; 13. Clamp two; 14. Cylinder. Detailed Implementation

[0042] An ultrasonic testing device for composite material cylindrical tubes utilizes a technique of inserting a stainless steel reflector tube into the composite material cylindrical tube to achieve product testing. A rotating R-axis is added to a water immersion testing system with X, Y, and Z-axis scanning bridges. The probe is fixed above the water tank at the end of the Z-axis of the scanning bridge. 100% coverage scanning of the product is achieved through either horizontal linear scanning along the X-axis, stepping scanning along the R-axis, or a spiral scanning method with linear movement along the X-axis and high-speed rotation along the R-axis. A clamping fixture is placed at the bottom of the water tank. The clamping fixture consists of a support mechanism and two chucks (one and two). The support mechanism allows for height adjustment and X-axis scanning parallelism adjustment of the chucks via limiting screws on the clamping plate. Both chucks are conical, and the reflector tube and composite cylindrical tube are concentrically clamped through contact between the corresponding conical surfaces of the chucks. Chuck one is connected to the rotating shaft motor via a synchronous belt and is the driving shaft. The reflector tube chuck is internally connected to chuck one via a retaining spring and fixing screws. Chuck two is the driven shaft, connected to a cylinder, and can be clamped horizontally using a lever. During testing, the composite material cylindrical tube with a reflector tube is immersed in water and clamped by clamps one and two. The ultrasonic probe emits ultrasonic waves into the composite material cylindrical tube, which are reflected by the reflector tube and then pass through the composite material cylindrical tube again to be received by the probe. The reflected signal from the reflector tube can be used to detect and evaluate the internal defects and porosity of different ply parts of the composite material cylindrical tube.

[0043] An ultrasonic testing method for composite material circular tubes, the specific steps of which are as follows:

[0044] 1. Before the initial test, the support mechanism needs to be preliminarily adjusted, including adjusting the height of the chuck and the parallelism of the X-axis scanning direction. The height of the chuck is adjusted using the lifting limit screw of the support mechanism, and the water level of the reflector tube is observed to determine if the adjustment is appropriate. The reflector tube is clamped in the water tank, and the position of the scanning arm on the X and Y axes is adjusted to obtain the maximum reflection signal at both ends of the reflector tube. The difference in water level at both ends of the reflector tube is read using software, and the limit screw is repeatedly adjusted until the probe on the scanning arm has a consistent water level when scanning along the X-axis.

[0045] Similarly, the parallelism of the X-axis scanning direction is adjusted by the front and rear limit screws on the support mechanism. The maximum echo is found in the Y direction at one end of the reflector tube. When moving along the X-axis, the change of the echo of the reflector tube is observed. If the amplitude change is large, it means that the generatrix of the reflector tube is not parallel to the X-axis scanning direction. The clamping platform needs to be adjusted back and forth until a uniform reflected wave height is obtained on the reflector tube when the scanning arm moves along the X-axis.

[0046] 2. Using a focusing probe, select an appropriate water path to perform a 100% scan of the reflector tube. Adjust the echo amplitude of the reflector tube to 80% of the full scale on the fluorescent screen and record the gain (2A) at this point. 反This is the baseline for testing. The reflector tube needs to be straightened and meet certain surface finish requirements. Set the scanning distance, scanning speed, spacing, etc., and begin scanning. The resulting reflector tube image amplitude must be uniform and consistent.

[0047] 3. Insert the reflector tube 11 into the composite material test tube 12 and clamp it on the fixture. Adjust the detection range and delay, align the leading edge of the primary interface wave of the tube to the 1st-2nd division of the horizontal scale on the fluorescent screen, and adjust the reflector tube echo to the 5th-8th division on the fluorescent screen. Set the interface tracking gate 1 to track the primary interface echo S1, and the gate 2 to monitor the reflector tube echo B. 反 ,like Figure 2 As shown on the left. Composite laminated circular tubes typically have multiple layup locations. Based on the pre-known tube layup structure, the positions of the R and X axes are manually controlled using scanning software. The highest reflective tube echo is located in the thinnest region. The gain is adjusted so that the highest reflective tube echo reaches 80% of the vertical scale on the fluorescent screen, and the gain of 2A is recorded at this point. 管 Calculate 2A 管 -2A 反 =2Ai.

[0048] 4. When testing each composite cylindrical tube, follow steps 2 and 3 to adjust and obtain the minimum value of 2Ai. This minimum value is used as the benchmark value to approximate the zero porosity of the thinnest part of the cylindrical tube and is denoted as 2Amin. Subsequent tests should compare 2Ai and 2Amin. Generally, when the material and process remain unchanged, 2Ai will be greater than 2Amin. If a new minimum value is found, 2Amin should be revised promptly.

[0049] 5. Calculate the ultrasonic attenuation corresponding to the allowable porosity acceptance standard for the thinnest part of the product using the following formula:

[0050] 2A 验 (dB)=40(N-1)log(1-S / S0)

[0051] N = Equivalent number of carbon cloth layers N = n1 × F1 + n2 × F2

[0052] n1 = number of bidirectional fabrics, n2 = number of unidirectional fabrics

[0053] F1 = bidirectional fabric factor, F2 = unidirectional fabric factor

[0054] S / S0—Acceptable porosity (%) according to acceptance criteria

[0055] 6. Set the instrument's scanning sensitivity to 2A. 反 +2Ai+|2A 验Edit the color palette, perform appropriate graded imaging detection, and calculate the porosity of the corresponding layers in each area. If excessive porosity is found, recalculate 2A based on the number of layers. 验 Repeat steps 5 and 6 to perform imaging scans, and the size of the defects exceeding the standard can be obtained through image analysis software.

[0056] 7. Perform a 100% coverage scan of the circular tube using appropriate scanning distance, speed, and spacing, and then evaluate the results. The 100% coverage scan of the circular tube can be completed using X-axis scanning, rotary axis stepping, or a helical scanning method with linear X-axis movement and high-speed R-axis rotation.

[0057] Example 1:

[0058] Taking the testing process of a carbon fiber composite circular tube as an example, the tube has a diameter of approximately φ66mm. A φ40×1 stainless steel reflective tube is made. The thinnest part consists of 2 layers of bidirectional fabric and 9 layers of unidirectional fabric, while the thickest part consists of 3 layers of bidirectional fabric and 15 layers of unidirectional fabric. The intermediate thickness consists of 2 layers of bidirectional fabric and 12 layers of unidirectional fabric.

[0059] 1. Complete the horizontal adjustment of the support fixture and the parallelism of the busbar.

[0060] 2. Adjust the gain of the ultrasonic instrument so that the echo height on the surface of the reflector tube corresponds exactly to a gray level of ≥80% on the computer's color palette. Record the gain reading as 2A. 反 .

[0061] 3. For the composite material tube under inspection on the outer casing of the reflector tube, scan the thinnest 11 layers to find the maximum reflected echo from secondary penetration, and adjust the gain so that the height of the reflected echo corresponds exactly to the computer amplitude ≥ 80%. Record the gain reading as 2A. 管 Calculate 2A 管 -2A 反 =2Ai.

[0062] 4. When receiving each composite tube, perform the operation and adjustment according to steps 1 and 2 to obtain the minimum value of 2Ai, which is taken as the reference value to approach the porosity of 0% in the 11th layer of the tube, and recorded as 2Amin. The test showed that the attenuation value of the zero porosity corresponding to this part was 9dB.

[0063] When 2Ai ≥ 9dB, take 2A0 = 9dB;

[0064] When 2Ai < 9dB, take 2A0 = 2A min.

[0065] 5. Set the C-scan color palette to 5 levels of grayscale display: 100%-80% is black, 80%-60% is dark gray (2.5dB attenuation), 60%-40% is gray (3.5dB attenuation), 40%-20% is light gray (6dB attenuation), and 20%-0% is white. The setting method for other levels is similar. The corresponding relationships are as follows:

[0066] grayscale Ultrasonic amplitude quantization Ultrasonic attenuation corresponding to quantization amplitude black ≥80％ ≥0dB Dark gray 60％～80％ 0 to -2.5 dB grey 40％～60％ -2.5 to -6 dB Light gray 20％～40％ -6 to -12 dB White 0％～20％ ≥-12dB

[0067] 6. The porosity acceptance standard for this product is 10%. Substituting the equivalent number of layers in the 11-layer section into the formula, we get: 2A 验 (dB)=40(N-1)log(1-S / S0)=40(12-1)log(1-0.1)=[-20.133]dB=-20dB; Adjust the gain to 2A 反 +2A0+20dB is used as the scanning sensitivity.

[0068] The porosity corresponding to 20dB ultrasonic attenuation is S / S0 = 10. 2A / 40(N-1) =10 -20 / 40(12-1) =9.94%. Other ultrasonic attenuation values ​​can be calculated using the same formula to determine the corresponding porosity, and a porosity evaluation table for this product can be developed.

[0069] The scanning sensitivity is 2A. 反 +2A0+20dB Porosity Assessment Table

[0070]

[0071] 7. After performing a 100% scan of the composite material cylindrical tube using appropriate scanning speed and step size, analyze the C-scan image. If no white areas appear, the tube meets the acceptance criteria. If white areas appear in the 17th layer area, increase the sensitivity and scan again, and re-evaluate according to the table below:

[0072] The scanning sensitivity is 2A. 反 +2A0+24dB Porosity Assessment Table

[0073]

[0074]

Claims

1. An ultrasonic testing method for composite material circular tubes, characterized in that: The method includes the following steps: Step 1: Clamp the reflector tube, adjust the level of the support mechanism, and adjust the parallelism between the reflector tube busbar and the X-axis scanning bridge; Step 2: Use a focusing probe to scan the reflector tube at 100% range. Adjust the gain of the ultrasonic instrument so that the echo amplitude from the reflector tube is 80% of the full-scale display on the screen. Record the gain at this point as 2A. 反 ; Step 3: Place the reflector tube inside the composite material tube and clamp the composite material tube and reflector tube together; scan the composite material tube to find the thinnest area of ​​the composite material tube where the maximum secondary penetration reflection echo is found, and adjust the gain of the ultrasonic instrument so that the amplitude of the maximum secondary penetration reflection echo is 80% of the full scale of the screen. Record the gain at this point as 2A. 管 And calculate 2Ai, 2Ai=2A 管 -2A 反 ; Step 4: Repeat steps 2 and 3 for all composite material tubes to be tested, and take the minimum value among all 2Ai as the zero porosity benchmark value of the thinnest part of the composite material tube, denoted as 2Amin; Step 5: Calculate the ultrasonic attenuation 2A corresponding to the acceptance standard for the porosity of the thinnest part of the composite material circular tube. 验 The formula is as follows: 2A 验 (dB)=40(N-1)log(1-S / S0) Where N = the equivalent number of carbon cloth layers N = n1 × F1 + n2 × F2; n1 = number of bidirectional fabrics, n2 = number of unidirectional fabrics; F1 = bidirectional fabric coefficient, F2 = unidirectional fabric coefficient; S / S0—Porosity (%) allowed by acceptance criteria; Step Six: Set the ultrasonic instrument gain to 2A. 反 +2Ai+|2A 验 As a scanning sensitivity, the C-scan color palette is set to 5 levels of grayscale display; 100%-80% grayscale is black, 80%-60% is dark gray, 60%-40% is gray, 40%-20% is light gray, and 20%-0% is white. Using the pre-set sensitivity and color palette, C-scan imaging was performed on all the composite material cylindrical tubes to be inspected.

2. The method according to claim 1, characterized in that: In step one, the process of adjusting the level of the support mechanism is as follows: Adjust the lifting limit screws on the left and right sides of the support mechanism to adjust the position of the probe in the X and Y axis directions. The Y axis, X axis, and Z axis form a right-hand coordinate system that is perpendicular to the paper. Obtain the maximum reflection signal at both ends of the reflector. If the water path of the maximum reflection signal at both ends of the reflector is equal, it is considered that the support mechanism has been adjusted to be level. Otherwise, continue to adjust the lifting limit screws.

3. The method according to claim 1, characterized in that: In step one, the parallelism adjustment process between the reflector busbar and the X-axis scanning bridge is as follows: The support mechanism is equipped with front and rear limiting screws at both ends. The probe is moved along the Y direction at one end of the reflector tube to find the maximum echo, and then the probe is moved along the X axis at the position of the maximum echo. The reflected echo is continuously observed. If the amplitude of the reflected echo is inconsistent, the busbar of the reflector tube is not parallel to the X-axis scanning bridge. The other end of the support mechanism is adjusted back and forth until the amplitude of the reflected echo is consistent.

4. The method according to claim 3, characterized in that: In step six, the ultrasonic attenuation corresponding to black is less than [2A]. 验 [], [] indicates integers, and the dark gray area corresponds to the ultrasonic attenuation range of [2A]. 验 2A 验 -2.5dB); the gray area corresponds to the ultrasonic attenuation range of [2A]. 验 -2.5dB, 2A 验 -6dB); the light gray color corresponds to the ultrasonic attenuation range of [2A]. 验 -6dB, 2A 验 -12dB); the white area corresponds to an ultrasonic attenuation range greater than or equal to 2A. 验 -12dB; The porosity range corresponding to different layups is calculated based on the ultrasonic attenuation range corresponding to the five gray levels.

5. The method according to claim 4, characterized in that: In step six, the pre-set C-scan color palette is used to scan all the composite material tubes to be inspected; the porosity of the composite material tubes is judged according to the gray level corresponding to the scanning results; and the degree and size of the porosity non-compliance are judged according to the gray level.

6. The method according to claim 5, characterized in that: Step six further includes: if the porosity qualification standard corresponding to a certain layup method is included in the porosity range corresponding to a certain gray level, then the ultrasonic instrument gain is readjusted and scanning imaging is performed so that the porosity qualification standard corresponding to the corresponding layup method is located at the boundary line between the porosity ranges corresponding to the two gray levels.

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