A method for detecting defects in a weld of an annular pipe structure

Abstract

This disclosure relates to a method for detecting defects in welds in annular cylindrical structures. The method is applicable to a weld defect detection system. The system includes a component to be inspected, an excitation unit, and a receiving unit. The component to be inspected includes an annular cylindrical structure, the shape of which is an arc obtained by cutting the annular cylindrical structure with a plane perpendicular to the axis of the annular tube. The weld is located on the annular cylindrical structure, and the angle between its extension direction and the axis of the annular tube is less than or equal to 90°. Multiple vibration elements in the excitation unit are sequentially arranged along the circumference of the component to be inspected on its outer surface. The receiving unit includes at least one receiving sensor. The method includes: controlling the vibration of each vibration element to generate an ultrasonic excitation signal inside the component to be inspected, thereby generating a T(0,1) mode ultrasonic guided wave in the component; acquiring the vibration signal collected by the receiving sensor; and determining the location of the weld defect in the component based on the vibration signal. This method can be used for defect detection in the casing of a liquid rocket engine turbopump.

Description

Technical Field

[0001] This disclosure relates to the field of nondestructive testing technology, and in particular to a method for detecting defects in welds in annular pipe structures. Background Technology

[0002] Liquid rocket engines have advantages such as long operating time, high specific impulse, and easy thrust control, and are widely used in launch vehicles and spacecraft. The working principle of a liquid rocket engine is to convert the chemical energy of its liquid propellant into heat energy in the combustion chamber, and then convert the heat energy into the kinetic energy of the high-speed ejected gas in the nozzle, generating reaction thrust.

[0003] In liquid rocket engines, the task of pressurizing and pumping liquid rocket fuel, including liquid hydrogen and liquid oxygen, into the engine combustion chamber is generally undertaken by a pump-pressurized liquid propellant supply system. The turbopump is a key component of this system, needing to pump liquid rocket fuel in harsh environments characterized by high temperature, high pressure, and strong vibration. As rocket engine technology continues to advance towards higher thrust and longer lifespan, the loads that turbopumps must withstand are increasing, further increasing the likelihood of turbopump damage.

[0004] As a future direction for aerospace technology development, reusable rockets have become the development goal of the next generation of rocket technology. In reusable rockets, the rocket engine is a crucial recoverable component. After recovery, key components need to be inspected, including the turbopump casing of the rocket engine.

[0005] Rocket engine turbopump housings are typically made from high-strength, high-density steel castings or machined titanium alloys. Due to the complex structure of the turbopump housing, traditional manufacturing methods are difficult to achieve integrated manufacturing, and the turbopump housing has very high requirements for its own sealing performance. Therefore, welding has become the main connection method for turbopump housings.

[0006] Because critical rocket engine components, including turbopumps, operate repeatedly and for extended periods in harsh environments, fatigue can occur at the weld seams, easily leading to damage cracks. These cracks can affect rocket engine performance. Therefore, in addition to the need for post-recovery inspection of turbopumps, real-time non-destructive monitoring of critical rocket engine components such as turbopumps is particularly important.

[0007] Due to the small area, irregular shape, and curvature of the weld seam area on the turbopump casing of liquid rocket engines, defect detection using existing inspection methods presents significant challenges for this unique and complex structure. Therefore, non-destructive testing / inspection of the circumferential weld seam on the turbopump casing of liquid rocket engines is a pressing issue that needs to be addressed. Summary of the Invention

[0008] In order to solve the above-mentioned technical problems, or at least partially solve the above-mentioned technical problems, this disclosure provides a method for detecting defects in welds in annular pipe structures.

[0009] This disclosure provides a method for detecting defects in welds in annular circular tube structures.

[0010] The defect detection method for welds in annular tube structures is applicable to weld defect detection systems.

[0011] The weld defect detection system includes a workpiece to be inspected, an excitation unit, and a receiving unit.

[0012] The component to be tested includes an annular tube structure, and the shape obtained by cutting the annular tube structure with a plane perpendicular to the axis of the annular tube is an arc; the weld is located on the annular tube structure, and the angle between the extension direction of the weld and the axis of the annular tube is less than or equal to 90°.

[0013] The excitation unit includes multiple vibration elements, which are arranged sequentially on the outer surface of the test piece along the circumference of the test piece, and the plane determined by the positions of the multiple vibration elements is perpendicular to the axial direction of the annular tube; the receiving unit includes at least one receiving sensor, which is disposed on the outer surface of the test piece.

[0014] The defect detection method for welds in annular pipe structures includes:

[0015] The vibration of each of the vibration elements is controlled to generate an ultrasonic excitation signal inside the test piece, thereby generating a T(0,1) mode ultrasonic guided wave in the test piece.

[0016] Acquire the vibration signal collected by the receiving sensor;

[0017] Based on the vibration signal, the location of the weld defect in the part to be inspected is determined.

[0018] The technical solution provided in this disclosure has the following advantages compared with the prior art:

[0019] First, it aims to achieve non-destructive testing of weld defects in the casing of liquid rocket engine turbopumps.

[0020] The weld seam of the turbopump casing of a liquid rocket engine is annular, and the two sides of the parent structure are not flat, exhibiting a certain angle, resulting in a narrow weld seam area. The technical solution provided in this application avoids the problem of being unable to use ultrasonic bulk wave detection under the constraint of a small weld seam area because both the excitation and receiving units are arranged on the annular circular tube structure, rather than in the weld seam area. It also avoids the installation difficulties of the ultrasonic guided wave excitation transducer in ultrasonic guided wave detection methods for ultrasonic weld seam characteristics caused by the complex, unexposed curved surface of the weld seam. Furthermore, it avoids the problem of needing to excite an acoustic mode whose energy is confined to the weld seam and propagates stably.

[0021] Second, it enables precise positioning of cracks extending in any direction within the weld and connection area.

[0022] The technical solution provided in this application can effectively locate both transverse and longitudinal cracks. Since any extension direction can be decomposed into angular components along the 0° direction and along the 90° direction, the technical solution provided in this application can effectively detect cracks in any extension direction from 0° to 90°.

[0023] Third, it requires no fine adjustments and has low requirements for the surface shape of the annular pipe weld.

[0024] Because the T(0,1) ultrasonic guided wave interacts with the weld during propagation, it carries defect information in the reflected echo. By analyzing the vibration signal collected by the receiving sensor, the weld crack information of the workpiece under test can be obtained. This method is a rapid detection method that can cover the entire weld. Compared with ultrasonic bulk wave detection, ultrasonic guided wave detection greatly reduces repetitive operations and improves detection efficiency. When using the technical solution provided in this application for weld defect detection, it is not necessary to make additional adjustments to the transducer for cases where the parent body on both sides of the annular pipe weld is not flat and the weld area is narrow. Only the excitation and reception method needs to be changed to excite the annular pipe guided wave for detection. It can detect the operating status of the turbopump under various working conditions.

[0025] Fourth, it is easy to operate and can adapt to various testing needs.

[0026] The essence of the above technical solution is to control the vibration of each vibration element after the excitation unit and receiving unit are deployed on the part to be inspected; automatically acquire the vibration signals collected by the receiving sensor; and determine the location of the weld defect in the part to be inspected based on the vibration signals. Before inspecting weld defects, it does not require pretreatment such as disassembly, shearing, or liquid penetration of the part to be inspected. Its operation is simple and can adapt to various safety inspection needs, such as periodic inspection and real-time monitoring, greatly contributing to the realization of reusable rockets and "smart rockets".

[0027] The technical solution provided in this application will not damage the test piece during the weld defect detection process, nor will it require personnel to have professional background knowledge of film reading, and will not endanger the health of the personnel. Attached Figure Description

[0028] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure.

[0029] To more clearly illustrate the technical solutions in the embodiments of this disclosure or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a three-dimensional structural diagram of an annular tube structure provided in an embodiment of the present disclosure;

[0031] Figure 2 This is a top view of another annular tube structure provided in an embodiment of the present disclosure;

[0032] Figure 3 For the pair along A1-A2 Figure 2 Cross-sectional view;

[0033] Figure 4 A partial three-dimensional structural schematic diagram of a liquid rocket engine turbopump housing provided for an embodiment of this disclosure;

[0034] Figure 5 For the pair along B1-B2 Figure 4 Cross-sectional view;

[0035] Figure 6 In order to be in Figure 4 A schematic diagram showing the arrangement of excitation and receiving units in the component to be tested;

[0036] Figure 7 A flowchart illustrating a method for detecting defects in welds in an annular tube structure, provided as an embodiment of this disclosure;

[0037] Figure 8 and Figure 9 A dispersion curve diagram of an annular tube structure provided in this application;

[0038] Figure 10 In order to be in Figure 4 Another schematic diagram showing the excitation unit and receiving unit arranged in the component to be tested;

[0039] Figure 11The images show the ultrasonic excitation signal from the control group and the signal processing results obtained after performing Hilbert transform and outer envelope fitting on the ultrasonic excitation signal.

[0040] Figure 12 The images show the reflected echo signals from Experiment 1 and the signal processing results obtained after applying Hilbert transform and outer envelope fitting to the reflected echo signals.

[0041] Figure 13 The image shows the reflected echo signal from Experiment 2, and the signal processing results obtained after performing Hilbert transform and outer envelope fitting on the reflected echo signal. Detailed Implementation

[0042] To better understand the above-mentioned objectives, features, and advantages of this disclosure, the solutions disclosed herein will be further described below. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0043] Numerous specific details are set forth in the following description in order to provide a full understanding of this disclosure, but this disclosure may also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only some, and not all, of the embodiments of this disclosure.

[0044] Existing methods for detecting weld defects include radiographic testing, penetrant testing, ultrasonic volume wave testing, and ultrasonic guided wave testing of weld characteristics.

[0045] The principle of radiographic inspection is to project X-rays onto the weld. If a defect exists at a certain location in the weld, the intensity of the X-rays transmitted through that location will be higher than the intensity of the X-rays transmitted through a defect-free location. Radiographic inspection requires personnel to have basic knowledge of interpreting radiographs, and the radiation used during the inspection process may pose a health hazard to the personnel.

[0046] Penetrant testing is a detection method based on capillary action. It requires penetrant to seep into the defect, followed by the application of a developer to reveal the defect's morphology. However, the use of penetrant and developer can corrode and damage the part being tested.

[0047] Ultrasonic bulk wave testing utilizes the numerous properties of ultrasonic waves (such as reflection and diffraction) to determine the presence of internal and surface defects by observing the propagation changes of ultrasonic waves within the test piece. Ultrasonic bulk wave testing requires point-by-point scanning along the weld area, which is labor-intensive and prone to missed defects. The weld seam of a liquid rocket engine turbopump casing resembles a fillet weld, but because the weld seam is annular and the two sides of the parent structure are not flat, forming an angle with the weld area, the turbopump casing weld seam is more complex. This characteristic, on the one hand, severely limits the transducer placement space during ultrasonic bulk wave testing, making it difficult to achieve point-by-point scanning only at the weld seam; on the other hand, signal excitation and reception by the transducer are difficult in a confined and curved space, resulting in poor signal stability and significant impact of external interference on the testing results.

[0048] Ultrasonic guided wave testing of weld characteristics involves arranging an excitation transducer array on the weld cross-section to generate ultrasonic guided waves localized within the weld area. Ultrasonic guided wave testing of weld characteristics is only suitable when the weld cross-section of the component under test is exposed. Liquid rocket engine turbopump casings do not have exposed weld cross-sections, making it impossible to arrange an excitation transducer array.

[0049] In view of this, the defect detection method for welds in annular pipe structures provided in this disclosure is applicable to weld defect detection systems. The weld defect detection system includes a component to be inspected, an excitation unit, and a receiving unit. The component to be inspected includes an annular pipe structure, and the shape obtained by cutting the annular pipe structure with a plane perpendicular to the axial direction of the annular pipe is an arc. The weld is located on the annular pipe structure, and the angle between the extension direction of the weld and the axial direction of the annular pipe is less than or equal to 90°. The excitation unit includes multiple vibration elements, which are sequentially arranged along the circumference of the component to be inspected on the outer surface of the component, and the plane determined by the positions of the multiple vibration elements is perpendicular to the axial direction of the annular pipe. The receiving unit includes at least one receiving sensor, which is disposed on the outer surface of the component to be inspected.

[0050] The arc obtained by cutting the annular tube structure with a plane perpendicular to the axis of the tube can be a complete arc or an incomplete arc. Optionally, the circumferential angle of the arc is θ, where 180°≤θ≤360°. Further, optionally, 180°≤θ<360°.

[0051] Figure 1 This is a three-dimensional structural diagram of an annular tube structure provided in an embodiment of this disclosure. See also... Figure 1 The annular tube structure is perpendicular to the axial direction of the annular tube. The shape S obtained by the plane is a circular arc; the extension direction of the weld is parallel to the axial direction of the annular pipe. Consistent (i.e., the angle between them is 0°). In Figure 1 In this annular circular tube structure, the tube axis M (the direction of the tube axis is relative to the axial direction of the annular tube) is... The curve (consistent with the shape) is a specific example of this application and not a limitation thereof. Furthermore, the axis of the annular circular tube structure can also be bent into a closed shape, such as a circle.

[0052] For example, Figure 2 This is a top view of another annular tube structure provided in an embodiment of this disclosure. Figure 3 For the pair along A1-A2 Figure 2 A cross-sectional view. The axis of the annular circular tube structure is bent into a circle.

[0053] In practice, weld seams can be detected in any part of the annular tube structure as defined in this application.

[0054] Figure 4 This is a partial three-dimensional structural diagram of a liquid rocket engine turbopump housing provided in an embodiment of the present disclosure. Figure 5 For the pair along B1-B2 Figure 4 Cross-sectional view. See also Figure 4 and Figure 5 The liquid rocket engine turbopump housing includes a gas collecting pipe D and a housing structure E. The hollow section of the gas collecting pipe D serves to transport fuel gas or oxidizer gas from the liquid engine. The shape S obtained by cutting the gas collecting pipe D with a plane perpendicular to the axial direction of the annular pipe is an arc. The pipe axis of the gas collecting pipe D is bent into a circle. The gas collecting pipe D and the housing structure E are welded together, with two welds, C1 and C2, between them. Both welds are annular. The gas collecting pipe D satisfies the aforementioned annular pipe structure; therefore, the liquid rocket engine turbopump housing can be used as a test component. The defect detection method for welds in annular pipe structures provided in this application can be used to detect weld defects in the liquid rocket engine turbopump housing.

[0055] Figure 6 In order to be in Figure 4 A schematic diagram showing the arrangement of excitation and receiving units in the device under test. (See also...) Figure 6 The excitation unit includes six vibration elements 11, which are arranged sequentially on the outer surface of the workpiece under test along the circumference of the annular tube structure, and plane a is perpendicular to the axial direction of the annular tube. All vibration elements 11 are located on plane a. The receiving unit includes a receiving sensor 21, which is disposed on the outer surface of the workpiece under test.

[0056] For ease of explanation, the overall principle of the present invention will be explained first:

[0057] Excitation by an excitation unit can generate ultrasonic guided waves within a waveguide structure (in this application, waveguide structure refers to a ring-shaped circular tube structure), which can then propagate along the waveguide structure. During propagation within the waveguide structure, the ultrasonic guided waves interact with weld defects, causing the signal acquired by the receiving sensor to carry information related to these weld defects. By processing the signal acquired by the receiving sensor and analyzing its relevant characteristic quantities, weld defect information can be obtained.

[0058] Figure 7 A flowchart illustrating a method for detecting defects in welds in an annular circular tube structure, provided as an embodiment of this disclosure. See also... Figure 7 The defect detection method for welds in annular pipe structures includes:

[0059] S110. Control the vibration of each vibration element to form an ultrasonic excitation signal inside the test piece, thereby generating a T(0,1) mode ultrasonic guided wave in the test piece.

[0060] S120: Acquire the vibration signal collected by the receiving sensor.

[0061] S130. Based on the vibration signal, determine the location of the weld defect in the part to be inspected.

[0062] During the propagation of ultrasonic guided waves of different modes along a waveguide structure, dispersion may or may not occur. Dispersion refers to the separation of frequency components of an ultrasonic guided wave as it passes through the structure. In practice, the presence of dispersion can be determined by the changes in phase velocity and group velocity. Phase velocity describes the velocity of each frequency component. When different frequency components combine, the velocity of the superimposed wave packet is called the group velocity. The changes in phase velocity and group velocity are related to the frequency-thickness product of the structure (also known as the frequency-thickness product), and can be described by a dispersion curve.

[0063] If, during the propagation of an ultrasonic guided wave along a waveguide structure, the propagation speed remains constant, the phase velocity and group velocity are the same, and the propagation speed does not change with the thickness of the ultrasonic guided wave structure, then this mode is non-dispersive. This ultrasonic guided wave mode is suitable for locating defects in ultrasonic guided wave structures.

[0064] Figure 8 and Figure 9 The dispersion curve diagram of an annular tube structure provided in this application. Figure 8 and Figure 9 This is derived from a semi-analytical calculation model based on the axial propagation of torsional wave modes in a ring-shaped circular tube structure. Figure 8 and Figure 9It can be seen that, when the excitation frequency f is appropriately selected, the T(0,1) mode of the torsional wave is a non-dispersive ultrasonic guided wave. This mode has a constant propagation speed and low attenuation in a homogeneous medium, making it suitable for locating weld defects. Therefore, this application utilizes the T(0,1) mode ultrasonic guided wave to detect weld defects in a test piece including an annular cylindrical structure.

[0065] In practice, to generate T(0,1) mode ultrasonic guided waves in the test piece, two approaches can be taken:

[0066] On the one hand, the excitation frequency f is determined based on the cutoff frequency of the T(0,n) mode (n>1, n is an integer), so that the excitation frequency f is less than the cutoff frequency of the T(0,n) mode (n>1, n is an integer). The reason for this setting is that for any ultrasonic waveguide structure, the higher-order modes in the T(0,n) mode group (n>1) have cutoff frequencies. When the excitation frequency is higher than the cutoff frequency of the higher-order modes, the higher-order modes will be generated sequentially, thus forming a dispersion phenomenon.

[0067] On the other hand, multiple vibration elements are arranged on the outer surface of the annular tube structure by selecting an appropriate arrangement method, and the vibration elements are provided with tangential excitation to avoid the generation of other modes.

[0068] Optionally, if the circumferential angle of the arc intercepted by the test piece by a plane perpendicular to the axial direction of the ring tube is θ, the ultrasonic guided wave wavelength of the T(0,1) mode is λ; 180°≤θ≤360°.

[0069] The spacing d between two adjacent vibrating elements satisfies:

[0070]

[0071] For example, if the circumferential angle of the arc obtained by the gas collecting pipe D in the casing of a liquid rocket engine turbopump, which is cut by a plane perpendicular to the axial direction of the annular pipe, is θ = 225°, and the wavelength of the ultrasonic guided wave in T(0,1) mode is λ = 28 mm, then according to equation (1), d ≤ 44.8 mm. In this case, the excitation unit can be set to include 6 vibration elements. The minimum distance between any two adjacent vibration elements on the outer surface of the annular pipe structure is 38 mm, and at this time, the circumferential angle of the line connecting any two adjacent vibration elements on the outer surface of the annular pipe structure is θ = 45°.

[0072] By setting the spacing d between two adjacent vibrating elements to satisfy equation (1), it is beneficial to generate T(0,1) mode ultrasonic guided waves in the test piece.

[0073] Furthermore, during weld defect detection, each vibration element can be configured to vibrate tangentially around its respective location. For example, in... Figure 6In the diagram, the vibration direction of each vibrating element is indicated by a double-headed arrow. This facilitates the generation of T(0,1) mode ultrasonic guided waves in the device under test.

[0074] In practice, there are various specific implementation methods for S130, and this application does not limit them. For example, the specific implementation steps of S130 include: determining the time difference between the ultrasonic excitation signal and the defect reflection echo signal arriving at the receiving sensor setting position based on the vibration signal; obtaining the group velocity of the T(0,1) mode ultrasonic guided wave propagating in the workpiece under test; and determining the position of the weld defect in the workpiece under test based on the time difference and the group velocity.

[0075] In this context, the group velocity of the T(0,1) mode ultrasonic guided wave propagating in the test piece is equal to the ratio of the propagation distance to the time required for the same ultrasonic excitation signal (with the same excitation frequency) to propagate in one cycle onto a standard part. The standard part is a defect-free part with the same structure as the test piece. When determining the group velocity, it is necessary to ensure that the excitation unit's position relative to the test piece is consistent with its position relative to the standard part, and that the receiving unit's position relative to the test piece is consistent with its position relative to the standard part. In practice, the group velocity of the T(0,1) mode ultrasonic guided wave propagating in the test piece can be obtained based on simulation.

[0076] There are various methods for determining the time difference between the arrival of the ultrasonic excitation signal and the defect reflection echo signal at the receiving sensor's location based on the vibration signal, and this application does not limit this method. For example, a Hilbert transform is performed on the vibration signal to obtain the transform result; the outer envelope fitting line of the transform result is determined; based on the outer envelope fitting line, the arrival times of the ultrasonic excitation signal and the defect reflection echo signal at the receiving sensor's location are determined; and based on these arrival times, the time difference between the ultrasonic excitation signal and the defect reflection echo signal at the receiving sensor's location is determined. This approach provides a simple and easy-to-implement method for determining the time difference, and the time difference determined by this method is relatively accurate.

[0077] Furthermore, determining the location of the weld defect in the workpiece based on the time difference and group velocity can include: determining that the weld defect is located on the side of the receiving sensor away from the plane determined by the positions of multiple vibration elements, and that the distance x of the weld defect from the plane where the receiving unit is located satisfies:

[0078]

[0079] Where Δt is the time difference and v is the group velocity.

[0080] The following is a specific example to illustrate:

[0081] For example, see Figure 6 Multiple vibration elements 11 are located on surface a, and a receiving sensor 21 is located on surface b. Surfaces a and b do not coincide. Defect 31 is located on surface c. Surfaces a, b, and c are all perpendicular to the axial direction of the annular tube structure. Figure 6 The propagation directions of the ultrasonic excitation signal and the defect reflection echo signal in the test piece are shown using unidirectional arrows. (See also...) Figure 6 After controlling the vibration of each vibrating element, an ultrasonic excitation signal P is generated inside the workpiece under test. The ultrasonic excitation signal P propagates simultaneously from surface a to both sides of surface a. Part of the ultrasonic excitation signal P reaches surface b and is collected by the receiving sensor 21 set in surface b. The ultrasonic excitation signal P passing through surface b continues to propagate, reaches surface c, and is reflected by the defect 31 at surface c, forming a defect reflection echo signal Q. The defect reflection echo signal Q propagates towards surface b. When the defect reflection echo signal Q reaches surface b, it is collected by the receiving sensor 21 set in surface b. By performing Hilbert transform and outer envelope fitting on the vibration signal collected by the receiving sensor, the time difference Δt between the ultrasonic excitation signal and the defect reflection echo signal reaching the receiving sensor can be calculated. If the group velocity is v, the distance from the weld defect to the receiving unit's set plane (i.e., surface b) is... The distance from the weld defect to the plane (i.e., plane a) of the excitation unit is x + x0. Where x0 is the distance between plane a and plane b.

[0082] In this application, the distance from a point (such as a weld defect) to a surface refers to the distance that the point needs to travel along the axial direction of the annular pipe to reach that surface, and the point must remain on the outer surface of the annular pipe structure throughout the movement. The distance between surfaces refers to the distance traveled by any point on the moved surface that is also on the outer surface of the annular pipe structure during the entire movement process of moving one surface to coincide with another surface.

[0083] It should be noted that, with Figure 6 The configuration is as follows: the area between surface a and surface b is a detection blind zone. This means that if a weld defect is located between surfaces a and b, the peaks of the excitation signal and the reflected echo signal from the defect overlap and cannot be separated. Therefore, processing the vibration signal cannot determine the time difference between the arrival of the ultrasonic excitation signal and the reflected echo signal from the defect at the receiving sensor's location.

[0084] In practice, the location of weld defects is often unknown before the receiving sensors are deployed. It's possible that the weld defect might be located in a detection blind zone after the sensors are installed. Therefore, in actual weld defect detection, multiple receiving units can be deployed, each with a different plane (perpendicular to the annular pipe axis). Alternatively, by analyzing vibration signals and identifying a suspected weld defect in a detection blind zone, the receiving sensor's position can be moved until the defect can be located.

[0085] In another embodiment, the vibration element may optionally be multiplexed as a receiving sensor. For example, Figure 10 In order to be in Figure 4 Another schematic diagram showing the installation of excitation and receiving units in the device under test. See [link to schematic diagram]. Figure 10 Surface a coincides with surface b, and at least one vibration element in surface a is reused as a receiving sensor. The distance from the weld defect to the receiving unit's mounting plane (i.e., surface b) and the distance from the weld defect to the excitation unit's mounting plane (i.e., surface a) are the same, both being...

[0086] By reusing vibration elements as receiving sensors, we can eliminate detection blind spots and reduce the number of sensors that need to be deployed on the outer surface of the workpiece, thereby reducing detection costs.

[0087] In practice, weld defects mainly manifest as weld cracks. A transverse crack is defined as a crack perpendicular to the weld's extension direction, while a longitudinal crack is defined as a crack parallel to the weld's extension direction. The angle of a weld crack in any extension direction can be decomposed into components along the 0° and 90° directions. Therefore, if the technical solution provided in this application can locate transverse and longitudinal cracks, it means that the technical solution provided in this application can locate cracks in any extension direction, and its detection results are effective.

[0088] The finite element method (FEM) was used to test the ability of the technical solution provided in this application to locate transverse and longitudinal cracks. Test piece 1, test piece 2, and a standard part were constructed. The standard part, test piece 1, and test piece 2 have identical structures, differing only in that test piece 1 simulates the case with a longitudinal crack, and the distance between the longitudinal crack and the receiving sensor mounting plane b (or vibration element mounting plane a) is 0.1891 m. Test piece 2 simulates the case with a transverse crack, and the distance between the transverse crack and the receiving sensor mounting plane b (or vibration element mounting plane a) is 0.1778 m. The standard part simulates the case without cracks. The size of the longitudinal crack in test piece 1 is the same as the size of the transverse crack in test piece 2.

[0089] Assuming the relative positions of the test piece 1, the excitation unit, and the receiving unit are set as follows, the relative positions of the test piece 2, the excitation unit, and the receiving unit, and the relative positions of the standard part, the excitation unit, and the receiving unit are also set as follows. Figure 10 As shown.

[0090] Part 1, Part 2, and the standard part are all gas collecting pipe shells in a turbopump structure, with a wall thickness of 3mm and a radius of 28mm. The gas collecting pipe is welded to the shell structure, with a weld width of 5mm and the weld area protruding 1mm above the base material (i.e., between the gas collecting pipe and the shell). Part 1, Part 2, and the standard part are all made of structural steel with a density of 7932kg / m³. 3 The elastic modulus is 217 GPa and the Poisson's ratio is 0.28. Tests show that the ultrasonic guided wave mode group velocity at T(0,1) is v = 3097 m / s.

[0091] The weld defect detection system including part 1 to be tested is referred to as experimental group 1, the weld defect detection system including part 2 to be tested is referred to as experimental group 2, and the weld defect detection system including part 1 to be tested is referred to as control group.

[0092] For experimental groups 1, 2, and the control group, the vibration of each vibrating element was controlled to generate T(0,1) mode ultrasonic guided waves in test piece 1, test piece 2, and the standard piece, respectively. Vibration signals were collected using the receiving sensors in experimental groups 1, 2, and the control group, and Hilbert transform and outer envelope fitting were performed on the collected vibration signals. The results are as follows: Figures 11-13 As shown. Among them, Figure 11 The data represents the ultrasonic excitation signal in the control group and the signal processing results obtained after applying Hilbert transform and outer envelope fitting to the ultrasonic excitation signal. Figure 12 The image shows the reflected echo signal from Experiment 1 and the signal processing results obtained after applying Hilbert transform and outer envelope fitting to the reflected echo signal. Figure 13 This section presents the reflected echo signal from Experimental Group 2 and the signal processing results obtained after applying Hilbert transform and outer envelope fitting to the reflected echo signal. It should be noted that for Experimental Groups 1 and 2, processing the vibration signals acquired by the receiving sensor yields both ultrasonic excitation and reflected echo signals. For the control group, processing the vibration signals acquired by the receiving sensor yields an ultrasonic excitation signal, but no reflected echo signal. Furthermore, the ultrasonic excitation signals from Experimental Groups 1, 2, and the control group are identical (same amplitude, same peak arrival time). For ease of understanding, after obtaining... Figure 12 and Figure 13 During the process, the ultrasonic excitation signal was filtered out.

[0093] contrast Figure 11 and Figure 12 For longitudinal cracks, after applying Hilbert transform and outer envelope fitting to the vibration signal, the peak arrival time of the excitation signal was found to be 2.476e-5 s, and the peak arrival time of the defect reflection echo signal was 0.0001503 s, with Δt = 1.2554e-04 s, corresponding to a distance of... Error 0.0053m, relative error 2.8%.

[0094] contrast Figure 11 and Figure 13 For transverse cracks, after performing Hilbert transform and outer envelope fitting on the vibration signal, the peak arrival time of the excitation signal was obtained as 2.476e-5s, the peak arrival time of the defect reflection signal was 0.0001409s, Δt = 1.1614e-04s, and the corresponding distance... Error 0.0021m, relative error 1.2%.

[0095] The above results demonstrate that the technical solution provided in this application can locate transverse and longitudinal cracks, meaning that the technical solution provided in this application can locate cracks in any direction of extension, and its detection results are effective.

[0096] contrast Figure 12 and Figure 13 The amplitude of the reflected echo signal from transverse cracks is higher than that from longitudinal cracks. This indicates that, relative to the two defect types, this method has higher sensitivity for detecting transverse cracks. Optionally, if it is necessary to improve the detection sensitivity for longitudinal cracks, other ultrasonic guided wave modes can be used for excitation.

[0097] It should be noted that research shows that the larger the defect size, the stronger the defect reflection signal. This means that the defect is easier to detect.

[0098] Based on the above technical solutions, optionally, the shortest distance from at least one receiving sensor to the weld is less than or equal to a set distance threshold. This can enhance the defect reflection echo signal, making the time when the defect reflection echo signal arrives at the set position of the receiving sensor more accurate, thereby making the defect location result more accurate.

[0099] The beneficial effects of the above technical solution include:

[0100] First, it aims to achieve non-destructive testing of weld defects in the casing of liquid rocket engine turbopumps.

[0101] The weld seam of the turbopump casing of a liquid rocket engine is annular, and the two sides of the parent structure are not flat, exhibiting a certain angle, resulting in a narrow weld seam area. The technical solution provided in this application avoids the problem of being unable to use ultrasonic bulk wave detection under the constraint of a small weld seam area because both the excitation unit and the receiving unit are arranged on the annular circular tube structure, rather than in the weld seam area. It also avoids the installation difficulties of the ultrasonic guided wave excitation transducer in ultrasonic guided wave detection methods for ultrasonic weld seam characteristics caused by the complex, unexposed curved surface of the weld seam. Furthermore, it avoids the problem of needing to excite an acoustic mode whose energy is confined to the weld seam and propagates stably.

[0102] Second, it enables precise positioning of cracks extending in any direction within the weld and connection area.

[0103] The technical solution provided in this application can effectively locate both transverse and longitudinal cracks. Since any extension direction can be decomposed into angular components along the 0° direction and along the 90° direction, the technical solution provided in this application can effectively detect cracks in any extension direction from 0° to 90°.

[0104] Third, it requires no fine adjustments and has low requirements for the surface shape of the annular pipe weld.

[0105] Because the T(0,1) ultrasonic guided wave interacts with the weld during propagation, it carries defect information in the reflected echo. By analyzing the vibration signal collected by the receiving sensor, the weld crack information of the workpiece under test can be obtained. This method is a rapid detection method that can cover the entire weld. Compared with ultrasonic bulk wave detection, ultrasonic guided wave detection greatly reduces repetitive operations and improves detection efficiency. When using the technical solution provided in this application for weld defect detection, it is not necessary to make additional adjustments to the transducer for cases where the parent body on both sides of the annular pipe weld is not flat and the weld area is narrow. Only the excitation and reception method needs to be changed to excite the annular pipe guided wave for detection. It can detect the operating status of the turbopump under various working conditions.

[0106] Fourth, it is easy to operate and can adapt to various testing needs.

[0107] The essence of the above technical solution is to control the vibration of each vibration element after the excitation unit and receiving unit are deployed on the part to be inspected; automatically acquire the vibration signals collected by the receiving sensor; and determine the location of the weld defect in the part to be inspected based on the vibration signals. Before inspecting weld defects, it does not require pretreatment such as disassembly, shearing, or liquid penetration of the part to be inspected. Its operation is simple and can adapt to various safety inspection needs, such as periodic inspection and real-time monitoring, greatly contributing to the realization of reusable rockets and "smart rockets".

[0108] The technical solution provided in this application will not damage the test piece during the weld defect detection process, nor will it require personnel to have professional background knowledge of film reading, and will not endanger the health of the personnel.

[0109] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

[0110] The above description is merely a specific embodiment of this disclosure, enabling those skilled in the art to understand or implement it. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this disclosure. Therefore, this disclosure is not to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for detecting defects in welds in annular pipe structures, characterized in that, The method for detecting defects in welds in annular tube structures is applicable to weld defect detection systems. The weld defect detection system includes a workpiece to be inspected, an excitation unit, and a receiving unit. The component to be tested includes an annular tube structure, and the shape obtained by cutting the annular tube structure with a plane perpendicular to the axis of the annular tube is an arc; the weld is located on the annular tube structure, and the angle between the extension direction of the weld and the axis of the annular tube is less than or equal to 90°. The excitation unit includes multiple vibration elements, which are arranged sequentially on the outer surface of the test piece along the circumference of the test piece, and the plane determined by the positions of the multiple vibration elements is perpendicular to the axial direction of the annular tube; the receiving unit includes at least one receiving sensor, which is disposed on the outer surface of the test piece. The defect detection method for welds in annular pipe structures includes: The vibration of each of the vibration elements is controlled to generate an ultrasonic excitation signal inside the test piece, thereby generating a T(0,1) mode ultrasonic guided wave in the test piece. Acquire the vibration signal collected by the receiving sensor; Based on the vibration signal, the location of the weld defect in the part to be inspected is determined; The step of controlling the vibration of each of the vibration elements to generate an ultrasonic excitation signal inside the test piece, thereby generating a T(0,1) mode ultrasonic guided wave in the test piece, includes: During the weld defect detection process, each of the aforementioned vibration elements vibrates circumferentially along its respective set position; The method further includes: If the circumferential angle of the arc intercepted by the test piece by a plane perpendicular to the axial direction of the annulus is... The wavelength of the ultrasonic guided wave in T(0,1) mode is ; Spacing between two adjacent vibrating elements satisfy: 。 2. The method according to claim 1, characterized in that, The vibration element is reused as the receiving sensor.

3. The method according to claim 1, characterized in that, Determining the location of weld defects in the workpiece under inspection based on the vibration signal includes: Based on the vibration signal, determine the time difference between the ultrasonic excitation signal and the defect reflection echo signal arriving at the location of the receiving sensor; Obtain the group velocity of the T(0,1) mode ultrasonic guided wave propagating in the test piece; Based on the time difference and the group velocity, the location of the weld defect in the part to be inspected is determined.

4. The method according to claim 3, characterized in that, The determination of the time difference between the arrival of the ultrasonic excitation signal and the defect reflection echo signal at the location of the receiving sensor based on the vibration signal includes: Perform a Hilbert transform on the vibration signal to obtain the transform result; Determine the outer envelope fitting line of the transformation result; Based on the outer envelope fitting line, the time when the ultrasonic excitation signal arrives at the location of the receiving sensor and the time when the defect reflection echo signal arrives at the location of the receiving sensor are determined. Based on the time it takes for the ultrasonic excitation signal to reach the location of the receiving sensor, and the time it takes for the defect reflection echo signal to reach the location of the receiving sensor, the time difference between the arrival of the ultrasonic excitation signal and the defect reflection echo signal at the location of the receiving sensor is determined.

5. The method according to claim 3, characterized in that, Determining the location of the weld defect in the workpiece under inspection based on the time difference and the group velocity includes: The weld defect is determined to be located on the side of the receiving sensor away from the plane defined by the positions of the plurality of vibration elements, and the distance between the weld defect and the plane on which the receiving unit is located is determined. satisfy: in, The time difference is... Let be the group velocity.

6. The method according to claim 1, characterized in that, At least one receiving sensor has a minimum distance from the weld that is less than or equal to a set distance threshold.

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