A positioning scale and method for determining catheter strain gauge placement

Abstract

The application discloses a positioning ruler and method for determining the sticking position of a strain gauge of a duct, and belongs to the field of mechanical tests of a space aircraft engine duct structure. The positioning ruler comprises a hoop and a clamping rod. The hoop is composed of two symmetrical half-cylindrical shell bodies which are hinged at one end side edge. The two shell bodies can be opened and closed along the hinge. After being closed, the two shell bodies form a cylindrical cavity for accommodating the measured duct. Four groups of line drawing grooves with the same structure are uniformly distributed in the circumferential direction of the hoop. Each group of line drawing grooves is parallel to the central axis of the hoop. The two ends of each group of line drawing grooves are provided with pin holes. The shaft center of the pin hole is located on the center line of each group of line drawing grooves. The clamping rod is a flat straight rod. A pin is arranged on the bottom surface of one end of the clamping rod. The clamping rod is rotationally connected with the hoop by embedding the pin into the pin hole. The bottom surface of the clamping rod is flatly clamped on the adjacent curved sections of the duct by adjusting the fitting angle of the hoop and the duct. The positioning of the hoop is completed. Then, the line drawing in the line drawing groove can mark the sticking position of the strain gauge on the duct.

Description

Technical Field

[0001] This invention belongs to the field of mechanical testing of aerospace vehicles and engine duct structures. Specifically, it relates to a positioning ruler and method for determining the bonding position of strain gauges in ducts. During stress testing of duct structures, the bonding position of strain gauges can be determined quickly and accurately. Background Technology

[0002] The duct system is an important channel for power transmission and energy transfer in aircraft and engines. Under the combined effects of pump supply pressure and flight vibration environment, the duct often suffers fatigue failure due to excessive stress. Therefore, stress monitoring of the duct is an important part of duct testing.

[0003] Strain gauges are the most commonly used sensors for monitoring the stress in conduits. Currently, the requirements for strain gauge placement are: in areas of high stress near the constraint end (e.g., pipe joints, nozzles, clamps, etc.), typically a section about 4-7 mm from the constraint end is selected. Two axial strain gauges are then placed at this section along the pipe axis, with the two gauges spaced 90° apart circumferentially. However, in actual engineering and testing, due to the lack of precise positioning devices, the placement of strain gauges is often done manually by visual inspection, resulting in significant randomness, inaccurate angle spacing, and angular deviations. This leads to inaccurate test results, and may even prevent the determination of the true stress in the pipe.

[0004] Studies have shown that the mode shapes of constrained bent ducts are both in-plane (the plane formed after the duct is bent) and out-of-plane (perpendicular to the bending surface of the duct) modes. Therefore, the placement of strain gauges requires accurate identification of their in-plane and out-of-plane orientations. During stress testing, accurate strain gauge placement methods can obtain the location of the maximum stress point and the principal mode shape at the corresponding frequency. Furthermore, aircraft and engines often contain hundreds of duct systems, making testing and analysis extremely demanding. Therefore, it is essential to develop a device capable of rapidly determining the in-plane and out-of-plane orientations of complex duct systems and the placement of sensors.

[0005] In summary, a positioning ruler is needed in the stress testing of conduit systems to help experimenters accurately and efficiently determine the bonding positions of sensors such as strain gauges. Summary of the Invention

[0006] The technical problem to be solved:

[0007] To overcome the shortcomings of existing technologies, this invention provides a positioning ruler and method for determining the bonding position of strain gauges in a conduit. The positioning ruler includes a clamp and a mounting rod. The clamp consists of two semi-cylindrical shell structures hinged and fitted to the outer surface of the conduit, with its end face close to the constraint end face of the conduit. The clamp is provided with a marking groove and a first pin hole. One end of the mounting rod is rotatably connected to the first pin hole. By adjusting the fitting angle between the clamp and the conduit, the bottom surface of the mounting rod is made to rest flat on the adjacent curved section of the conduit to achieve clamp positioning. The bonding position of the strain gauge can be determined by marking a line in the marking groove.

[0008] This invention solves the problem of inaccurate test results caused by the inaccurate positioning of strain gauges by manual visual inspection during existing guide tube stress testing.

[0009] The technical solution of the present invention is: a positioning ruler for determining the bonding position of the strain gauge of the conduit, including a sleeve 1 and a connecting rod 2. The sleeve 1 includes a left half shell 4 and a right half shell 5. The left half shell 4 and the right half shell 5 are symmetrical semi-cylindrical shells. The left half shell 4 and the right half shell 5 are hinged at one side of their respective ends, and the other side of their respective ends can be opened and closed along the hinge. The left half shell 4 and the right half shell 5 are joined together to form a cylindrical cavity for accommodating the conduit 12 to be tested.

[0010] The sleeve 1 is provided with multiple sets of marking grooves 8 with the same structure around its circumference. Each set of marking grooves 8 is arranged parallel to the central axis of the sleeve 1. The marking groove 8 is a through groove with a rectangular cross-section. Each set of marking grooves 8 has a first pin hole 9 at both ends. The axis of the first pin hole 9 is located at the center line of each set of marking grooves 8.

[0011] The connecting rod 2 is a flat straight rod, and a first pin 10 is provided at the center of the bottom surface of one end. The connecting rod 2 is rotatably connected to the sleeve 1 by the first pin 10 being inserted into the first pin hole 9.

[0012] A further technical solution of the present invention is as follows: there are 4 groups of the marking grooves 8. The 4 groups of marking grooves 8 are evenly distributed around the circumference of the hoop 1, avoiding the hinge end and the opening end of the hoop 1, and are symmetrically arranged on the left half shell 4 and the right half shell 5. The distance between each group of marking grooves 8 and the edges of both ends of the hoop 1 is the same. There are 2 marking grooves in each group, and there is a certain distance between the two marking grooves in each group.

[0013] A further technical solution of the present invention is: one side of the left half shell 4 and the right half shell 5 is hinged by a hinge 6, and the other side is provided with a pinch handle 7 for opening and closing the left half shell 4 and the right half shell 5 around the hinge. The two pinch handles 7 are completely symmetrically attached after being pinched.

[0014] A further technical solution of the present invention is: a recessed platform is provided at the other end of the connecting rod 2, the recessed platform is opposite to the bottom surface of the connecting rod 2, and a second pin hole 11 is provided at the center of the recessed platform, the axis of the second pin hole 11 and the axis of the first pin 10 are located on the central axis of the connecting rod 2.

[0015] A further technical solution of the present invention is as follows: the connecting rod 2 further includes an extension rod 3, the extension rod 3 having the same cross-sectional dimensions as the connecting rod 2, and the extension rod 3 being used to extend the connecting rod 2; the two ends of the extension rod 3 are provided with concave platforms in opposite directions, a second pin 18 is provided at the center of the concave surface of one end of the concave platform, and a third pin hole 19 is provided at the center of the concave platform of the other end of the concave platform, the axes of the second pin 18 and the third pin hole 19 being located on the central axis of the extension rod 3; the second pin 18 is embedded in the second pin hole 11 of the connecting rod 2, and the concave platform at the second pin 18 of the extension rod 3 matches the concave platform at the second pin hole 11 of the connecting rod 2, so that the bottom surface of the connecting rod 2 and the bottom surface of the extension rod 3 are on the same plane.

[0016] A further technical solution of the present invention is that the materials of the support pole 2 and the extension pole 3 are hard metal materials.

[0017] A method for determining the bonding position of a strain gauge in a conduit using the aforementioned positioning ruler comprises the following steps:

[0018] Step 1: Install clamp 1: Open the left half shell 4 and right half shell 5 of clamp 1 along the hinge 6 and fit it onto the straight pipe section of the test conduit 12. Pinch the pinch handles 7 of the left half shell 4 and right half shell 5 symmetrically to make clamp 1 fit against the straight pipe section of the test conduit 12, and press one end face of clamp 1 against the end face of the constraint end 13 of the test conduit 12.

[0019] Step 2, Positioning of Hoop 1: Insert the first pin 10 at one end of the connecting rod 2 into the first pin hole 9 of the hoop 1, and rotate to adjust the contact angle between the hoop 1 and the straight section of the guide tube 12 to be tested, so that the bottom surface of the connecting rod 2 rests flat on the adjacent curved section 14; at this time, the center axis of the connecting rod 2 and the center line of the marking groove 8 where the first pin hole 9 of the connecting rod 2 is inserted determine the in-plane of the curved guide tube section to be tested, and the positioning of the hoop 1 is completed;

[0020] Step 3: Draw lines: Use a drawing pen to draw lines in each set of drawing grooves 8, remove the positioning ruler, and leave 4 sets of 8 drawn positioning lines 15 on the straight pipe section of the test guide tube 12, thereby determining the pasting position of the strain gauge 16.

[0021] Step 4: Attach the strain gauge 16: Take two strain gauges 16, attach one to the in-plane positioning line 15 and the other to the out-of-plane positioning line 15; when attaching, attach the strain gauge 16 between the two positioning lines 15 in the same group, with the central axis of the strain gauge 16 coinciding with the two positioning lines 15.

[0022] Beneficial effects

[0023] The beneficial effects of this invention are as follows: The positioning ruler and method for determining the bonding position of strain gauges in a conduit, as described in this invention, include a clamp and a mounting rod. The clamp is composed of two semi-cylindrical thin shells hinged together. The clamp is fitted to the outer surface of the conduit, with its end face close to the constraint end face of the conduit. The clamp is provided with a marking groove and a first pin hole. One end of the mounting rod is rotatably connected to the first pin hole of the clamp through a first pin. By adjusting the fitting angle between the clamp and the conduit, the bottom surface of the mounting rod rests flat on the adjacent curved section of the conduit being tested, thereby determining the in-plane and out-of-plane directions of the conduit being tested and completing the positioning of the clamp. The bonding position of the strain gauge can be determined and marked by drawing a line in the marking groove of the positioned clamp.

[0024] To address the problem of inaccurate test results caused by the randomness and reliance on experience in the placement of strain gauges during catheter stress testing in existing technologies, the positioning ruler and method for determining the placement of catheter strain gauges described in this invention can help testers accurately locate the placement of catheter strain gauges, with the following beneficial effects:

[0025] 1. Simply place the clamp of the positioning ruler tightly against the constraint end to easily achieve the positioning requirement of the strain gauge on the guide tube being 4-7mm away from the constraint end.

[0026] 2. The present invention is simple and easy to operate. It uses the plane formed by the center line of the corresponding marking groove on the sleeve and the center axis of the connecting rod to determine the in-plane and out-of-plane directions of the curved guide tube. At the same time, two positioning lines are drawn at each of the four sets of marking grooves at 90° intervals along the circumference of the guide tube section. When attaching the strain gauge, the center line of the strain gauge is aligned with the two positioning lines to achieve accurate positioning of the strain gauge attachment position, which helps to accurately obtain the in-plane and out-of-plane strain data of the curved guide tube.

[0027] 3. The positioning ruler of the present invention has strong versatility. It can be applied to conduits of different diameters by simply replacing the left and right half shells with different radii of curvature. That is, the radii of curvature of the left and right half shells are equal to the outer radius r of the conduit to be measured. Other dimensions on the clamp remain unchanged. Therefore, the positioning ruler of the present invention has universality and uniformity, and a set of tools can be made for different pipe diameters.

[0028] 4. The positioning ruler described in this invention is flexible in use, wherein the clamp has a symmetrical structure to adapt to the constraint end in any spatial position (e.g., near pipe joints, flat pipe nozzles, clamps, bends, etc.). Moreover, the mounting rod can be flexibly embedded in the first pin holes at both ends of any set of marking grooves spaced 90° apart on the clamp, which can meet the requirements for determining the position of strain gauges at different types of constraint ends.

[0029] 5. In this invention, the support rod can be extended. When the support rod is insufficient in length, multiple extension rods are used to extend it, determining the strain gauge attachment position in the case of long curved pipes. The connection between the clamp, support rod, and extension rod is simple and detachable, ensuring that the positioning ruler is suitable for strain gauge positioning of conduits in the narrow space of aircraft, and has the versatility to be used for both long and short pipes. At the same time, the overall size of the positioning ruler can be controlled within a small range, making it easy to package and carry.

[0030] 6. The positioning ruler described in this invention can also be used to position the bonding location of the accelerometer on the guide tube. The operation method is the same as that described in this invention. Simply move the clamp from the constraint end to the position where the accelerometer is to be bonded (generally, choose the position with larger amplitude, not the constraint end), and replace the strain gauge with the accelerometer (or the sensor's connecting base). Attached Figure Description

[0031] Figure 1 This is a structural diagram of the positioning ruler of the present invention;

[0032] Figure 2 This is a front view of the hoop of the present invention;

[0033] Figure 3 This is an axial schematic diagram of the clamp of the present invention;

[0034] Figure 4 This is a structural diagram of the support pole of the present invention;

[0035] Figure 5 This is a schematic diagram of the positioning method of the positioning ruler of the present invention;

[0036] Figure 6 This is a schematic diagram showing the marked lines and strain gauge attachment positions on the conduit of the present invention.

[0037] Figure 7 This is a structural diagram of the extension rod of the present invention;

[0038] Figure 8 A schematic diagram of the positioning method of the positioning ruler with extension rod described in the invention;

[0039] Figure 9 This is a schematic diagram illustrating the strain gauge attachment requirements during conduit testing.

[0040] Figure 10 This is a schematic diagram showing the in-plane and out-of-plane views;

[0041] Figure 11 This is a schematic diagram of a complex conduit with arbitrary bends and the required patch placement.

[0042] Figure 12 for Figure 11 A schematic diagram of the positioning method using the positioning ruler of this invention at point A;

[0043] Figure 13 for Figure 11 A schematic diagram of the positioning method using the positioning ruler of this invention at point B;

[0044] Figure 14 for Figure 11 A schematic diagram of the positioning method using the positioning ruler of this invention at point C;

[0045] Figure 15 for Figure 11 A schematic diagram of the positioning method using the positioning ruler of this invention at point D;

[0046] Figure 16 for Figure 11 A schematic diagram of the positioning method using the positioning ruler of this invention at point E;

[0047] Figure 17 for Figure 11 A schematic diagram of the positioning method using the positioning ruler of this invention at point F;

[0048] Figure 18 This is a schematic diagram of the connection between the support pole and the clamp.

[0049] Figure 19 for Figure 18 BB section view.

[0050] Explanation of reference numerals in the attached drawings: 1. Hoop 2. Connecting rod 3. Extension rod 4. Left half shell 5. Right half shell 7. Kneading handle 8. Marking groove 9. First pin hole 10. First pin 11. Second pin hole 12. Tested guide tube 13. Constraint end 14. Adjacent bending section 15. Positioning line 16. Strain gauge 17. Strain gauge lead wire 18. Second pin 19. Third pin hole. Detailed Implementation

[0051] The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the invention, and should not be construed as limiting the invention.

[0052] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0053] See Figure 9 The general method for attaching strain gauge 16 to the conduit is as follows: Figure 9 As shown, the strain test area was selected near the constraint end, approximately 4–7 mm from the end face of the constraint end, at the conduit. Two strain gauges were attached along the axial direction of the tested conduit 12. Figure 9 Along the x-direction, two strain gauges 16 are attached at 90° intervals along the outer surface of the pipe. Figure 9 The Oxy plane represents the in-plane orientation of the tested conduit 12, while the Oyz plane, perpendicular to it, represents the out-of-plane orientation. In engineering practice, the placement of strain gauges is often determined visually, which introduces significant randomness and inconsistency, leading to deviations in test results. The positioning ruler described in this invention effectively solves this problem.

[0054] See Figure 10 "In-plane" refers to the plane formed after the conduit is bent, while "out-of-plane" refers to the direction perpendicular to the bending plane.

[0055] This invention provides a positioning ruler for determining the bonding position of strain gauges in a conduit. In the stress test of the conduit, using this positioning ruler can ensure that the measuring point is 4-7 mm away from the constraint end, and at the same time, the two strain gauges are accurately 90° apart in the circumferential direction of the conduit. It can accurately identify the out-of-plane and in-plane orientation of any bent conduit, ensuring the accuracy of the test results.

[0056] See Figure 1 , Figure 2 , Figure 5 The positioning ruler for determining the bonding position of a strain gauge in a conduit, as described in this invention, includes a clamp 1, a connecting rod 2, and an extension rod 3. The clamp 1 is formed by hinged left half-shell 4 and right half-shell 5. Specifically, the left half-shell 4 and right half-shell 5 are symmetrical semi-cylindrical thin-film shells. The left half-shell 4 and right half-shell 5 are hinged at one side by a hinge 6, and each side is provided with a pinch handle 7. The pinch handle 7 is used to open and close the left half-shell 4 and right half-shell 5 around the hinge 6. The pinch handles 7 on the left half-shell 4 and right half-shell 5 are symmetrically arranged, and after pinching, they are completely symmetrically attached to avoid axial angular misalignment between the left half-shell 4 and right half-shell 5. The radius of curvature of the left half-shell 4 and right half-shell 5 is equal to the outer diameter of the conduit 12 being tested. The two half-shells are joined to form a cylindrical cavity to accommodate the conduit 12 being tested. When the two pinch handles 7 located on the left half-shell 4 and right half-shell 5 are symmetrically pinched, the clamp 1 is attached to the outer surface of the conduit 12 being tested.

[0057] See Figure 2 , Figure 3 The hinge 6 and the two kneading handles 7 are located on the η-η axis, which forms an angle of 45° with the circumferential axis of the tested conduit 12 in the 0°-180° and 90°-270° directions. This is located in the left half-shell 4 and the right half-shell 5. Figure 3Each of the four positions shown (0°, 90°, 180°, and 270°) has a set of marking grooves 8. Each set of marking grooves 8 consists of two marking grooves 8 spaced 3mm apart. Each set of marking grooves 8 is located on the same center line and parallel to the central axis of the sleeve 1. Specifically, the marking groove 8 is a through straight groove with a rectangular cross-section, and its dimensions are 3mm × 0.5mm. The distance between each set of marking grooves 8 and the edges of both ends of the sleeve 1 is designed to be 4mm. Each end of each set of marking grooves 8 has a first pin hole 9, and the axis of the first pin hole 9 is located on the center line of each set of marking grooves 8.

[0058] See Figure 4 , Figure 1 , Figure 18 , Figure 19 The connecting rod 2 is a flat, straight rod. A cylindrical boss-shaped first pin 10 is fixed at the center of the bottom surface of one end of the connecting rod 2. The first pin 10 on the connecting rod 2 is inserted into any one of the eight first pin holes 9 at four angles (0°, 90°, 180°, and 270°) on the clamp 1, rotatably connecting the connecting rod 2 to the clamp 1. The other end of the connecting rod 2 has a recess facing away from the bottom surface of the connecting rod 2. A second pin hole 11 is located at the center of the recess for connecting the extension rod 3. The axis of the second pin hole 11 and the axis of the first pin 10 are located on the central axis γ-γ of the connecting rod. For ease of carrying, the length of the connecting rod should not be too long, generally 50–200 mm is suitable. Considering the limited space for aircraft piping layout, the length of the connecting rod is selected as 50 mm.

[0059] See Figure 7 , Figure 8 The extension rod 3 is used to extend the connecting rod 2. For a long test conduit 12, if the distance between the constraint end 13 and the adjacent curved section 14 is far, for example, greater than 50mm, the length of the connecting rod 2 is insufficient to reach the adjacent curved section 14 of the test conduit 12, and the extension rod 3 is required. The extension rod 3 is also a flat straight rod. The cross-sectional dimensions of the extension rod 3 and the connecting rod 2 are the same. Both ends of the extension rod 3 are provided with a concave platform. The two concave platforms of the extension rod 3 are in opposite directions. A cylindrical second pin 18 is provided at the center of the concave surface of one end of the concave platform, and a third pin hole 19 is provided at the center of the concave platform of the other end. The axes of the second pin 18 and the third pin hole 19 are located on the central axis of the extension rod 3. The second pin 18 is embedded in the second pin hole 11 of the connecting rod 2. The concave platform at the second pin 18 of the extension rod 3 matches the concave platform at the second pin hole 11 of the connecting rod 2, so that the bottom surface of the connecting rod 2 and the bottom surface of the extension rod 3 are on the same plane.

[0060] See Figure 5 , Figure 6 , Figure 8 The method for determining the bonding position of the strain gauge in the conduit using the positioning ruler described in this invention comprises the following steps:

[0061] Step 1: Install clamp 1: Open the left half shell 4 and right half shell 5 of clamp 1 along the hinge 6 and fit it onto the straight pipe section of the test conduit 12. Pinch the pinch handles 7 of the left half shell 4 and right half shell 5 symmetrically to make clamp 1 fit against the straight pipe section of the test conduit 12, and press one end face of clamp 1 against the end face of the constraint end 13 of the test conduit 12.

[0062] Step 2, Positioning of Hoop 1: Insert the first pin 10 at one end of the connecting rod 2 into the first pin hole 9 of the hoop 1. Rotate the hoop 1 to adjust its contact angle with the straight section of the conduit 12 under test, so that the bottom surface of the connecting rod 2 can be placed flat on the adjacent curved section 14 of the conduit 12 under test. At this time, the central axis γ-γ of the connecting rod 2 and the center line α-α of the marking groove 8 where the first pin hole 9 of the first pin 10 on the connecting rod 2 is inserted determine a plane, that is, the plane of the curved conduit under test, and also the out-of-plane direction of the curved conduit under test. The positioning of the hoop 1 is completed. When the distance between the constraint end 13 and the adjacent curved section 14 is far, connect the extension rod 3 to the connecting rod 2. The bottom edges of the two are still kept in the same plane. The bottom edges of the extension rod formed in this way are coplanar. Place the bottom surface of the extension rod 3 flat on the adjacent curved section 14 of the conduit under test, and the positioning of the hoop 1 is completed. Considering that the extension pole 2 will undergo flexible deformation after being extended, the extension pole 2 and the extension pole 3 are made of rigid metal material to ensure the rigidity of the detachable connection.

[0063] In this invention, the connecting rod 2 and extension rod 3 sometimes need to extend into the narrow piping space of the aircraft, and neither should be too long. Therefore, this invention makes both detachable. Furthermore, when the positioning ruler cannot reach the adjacent bend 14, the extension rod 3 can be extended further; that is, the third pin hole 19 on the extension rod 3 can be connected to the second pin 18 on another extension rod. Repeated overlapping increases the total extension length of the connecting rod 2 and extension rod 3. Generally, two extension rods 3 are sufficient to reach the adjacent bend duct within a 200mm distance, which is sufficient for strain gauge positioning in mechanical testing of general-sized ducts in aircraft.

[0064] Step 3: Drawing lines: After positioning, use a non-destructive drawing pen on the surface of the test tube 12 to draw straight lines in the drawing groove 8 at four angles. Remove the positioning ruler, and leave 4 sets of 8 positioning lines 15 around the straight section of the test tube 12. Each set has 2 positioning lines 15, thus determining the bonding position of the strain gauge 16.

[0065] Step 4: Attaching Strain Gauges 16: Take two strain gauges 16, attach one to the in-plane positioning line 15 and the other to the out-of-plane positioning line 15. Specifically, attach the strain gauge 16 between the two positioning lines 15 in the same set, ensuring that the central axis of the strain gauge 16 coincides with both positioning lines 15. This ensures that the strain gauge 16 is positioned 4–7 mm from the constraint end, and that the two strain gauges 16 are 90° apart circumferentially along the tested conduit 12, and that the strain gauges 16 are positioned in both the in-plane and out-of-plane orientations of this curved conduit.

[0066] Description of the embodiments of the present invention:

[0067] In this invention, considering operability and line drawing function, the thickness of the sleeve 1 should not be too thick. At the same time, considering that the first pin hole 9 on the sleeve 1 should have the function of pin insertion, the thickness of the sleeve 1 should not be too thin. In this embodiment of the invention, the thickness of the sleeve 1 is more suitable to be 1mm.

[0068] The width of the marking groove 8 in this invention needs to be such that a regular pencil or marker can pass through the groove and draw a straight line on the pipe surface. However, it should not be too wide, as this would affect the accuracy of the marking, such as making the line too thick or causing the angle of the line to be off. A width of 0.5mm to 1mm is appropriate, and 0.5mm is used in this embodiment. Regarding the length of the marking groove 8, considering that a significant straight line segment should be drawn to facilitate the alignment of the center line of the strain gauge 16, it should not be too short. However, if it is too long, the clamp 1 will be too wide and cannot be used for pipes with smaller straight line segments. The straight line segment of aviation pipes is generally greater than 16mm, so this is the minimum standard. In this embodiment, the length of the marking groove 8 is 3mm.

[0069] For the interval length between two marked grooves 8 at the same angular position, it is necessary to consider that the strain gauges used for aircraft pipeline strain testing are generally between 1AA and 3AA, where the length and width dimensions of the 1AA strain gauge are 5.5×1.8mm and the length and width dimensions of the 3AA strain gauge are 6.9×3.6mm. The two positioning lines 15 (3mm in length) drawn by each set of marked grooves 8 should be able to cover the length range of the strain gauge 16. Therefore, the interval length of the marked grooves 8 is 1 to 3mm, and in this embodiment of the invention, it is taken as 3mm.

[0070] The present invention designs the distance between the marking groove 8 of the positioning ruler and the edge of the sleeve 1 to be 4mm. By tightly attaching the sleeve of the positioning ruler to the constraint end, the patch section positioning at 4mm from the constraint end can be easily achieved.

[0071] The left half-shell 4 and right half-shell 5 of the clamp 1 are symmetrically designed, with one end hinged for rotating the two half-shells to open the clamp 1 and fit it onto the tested conduit 12. It is important to note that the hinged structure should not affect the seamless fit between the left and right half-shells and the pipeline. In this invention, the hinge 6 is designed at the intersection of the tangents at 0° and 90° on the pipe cross-section. Figure 3As shown, the other end is a pinch handle 7, which is used for closing the left and right half shells after they are opened. The pinch handle 7 is symmetrical in size, which makes it easy to confirm that the two handles are completely symmetrically attached after pinching. At this time, there is no axial angle misalignment between the left half shell 4 and the right half shell 5.

[0072] After the left half shell 4 and the right half shell 5 are attached together, they enclose a complete circular pipe section. At the four positions of 0°, 90°, 180° and 270° of the circular pipe section, two etched grooves 8 are cut out along the axial direction at the corresponding four positions of the attached left and right half shells. The center lines of the two etched grooves 8 at each angle coincide and the same size.

[0073] For the test tube 12 with different diameters, it is only necessary to design the curvature radius of the left half shell 4 and the right half shell 5 to be equal to the outer diameter of the test tube 12, while keeping other dimensions unchanged. In this way, a complete set of positioning rulers with different diameters can be prepared according to the common pipe diameters of aviation high-pressure pipes, which are generally in the range of 6mm to 32mm.

[0074] Each set of marking grooves 8 on the sleeve 1 has a circular first pin hole 9 at both ends. The axis of the first pin hole 9 should be on the center line of the marking groove 8. The first pin hole 9 should not be too small, as it would be difficult to insert the connecting rod 2. In this embodiment of the invention, the diameter of the first pin hole 9 is 2mm. The first pin 10 at one end of the connecting rod 2 is inserted into the first pin hole 9, so that the connecting rod 2 can rotate 360° around the first pin hole 9 without obstruction.

[0075] The support rod 2 is a flat, straight rod with a smooth bottom surface. The length of the support rod 2 should not be too long, as this would make it difficult to access and operate in confined spaces or densely packed pipe systems. In this embodiment, the support rod length is designed to be 50mm, and the width should not be too narrow, as this would make operation difficult. Considering that the pipe diameter is in the range of 6mm to 32mm, and to facilitate a significant tangent between the support rod 2 and the pipe surface, the width of the support rod 2 in this embodiment is set to 6mm.

[0076] When using the positioning ruler of this invention, the first pin 10 of the connecting rod 2 is inserted into the first pin hole 9 on the clamp 1, and the angle of the clamp 1 is adjusted so that the bottom surface of the connecting rod 2 rests flat on the adjacent curved section 14 of the guide tube 12 being measured. Due to the two straight lines (see...) Figure 5The center line α-α of the groove 8 and the axis γ-γ of the connecting rod 2 can define a plane, that is, determine the in-plane and out-of-plane directions of the curved section of the pipeline. The clamp 1 completes the positioning in the out-of-plane direction. For the long test conduit 12, the connecting rod 2 cannot reach the adjacent curved section 14 of the pipeline. At this time, the length of the connecting rod 2 is insufficient, and it needs to be extended. The extension method is to connect the extension rod 3 to the connecting rod 2. One end of the connecting rod 2 is connected to the clamp 1, and the other end is made with a concave platform and a second pin hole 11. The second pin hole 11 can be connected to the second pin 18 on the extension rod 3 to increase the total length of the connecting rod 2. After mating, the bottom edge of the connecting rod 2 and the extension rod 3 are in the same plane. Then, the bottom surface of the extended connecting rod 2 is laid flat on the adjacent curved section 14 of the pipeline to complete the positioning of the clamp 1.

[0077] Example 1: Specific application example of the present invention, see [link / reference] Figure 11 Taking a complex, arbitrarily curved pipeline as an example, points A, B, C, D, E, and F in the diagram represent the required locations for the strain gauge 16. The method for positioning the strain gauge 16 at these six locations follows the steps described above. Figures 12-17 As shown, the positioning ruler of the present invention can accurately position the strain gauge 16 at various constraint ends, clamps, tee joints, bends and other high stress areas of any pipeline, and has high engineering promotion value.

[0078] The positioning ruler described in this invention has high positioning efficiency and simple positioning operation. It can also be extended to the positioning of strain gauges and acceleration sensors for other conduits with different diameters and layouts. It has versatility, simple structure, small size, and is easy to disassemble and carry.

[0079] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A positioning ruler for determining the bonding position of strain gauges in conduits, characterized in that: Includes a clamp (1) and a connecting rod (2). The clamp (1) includes a left half shell (4) and a right half shell (5). The left half shell (4) and the right half shell (5) are symmetrical semi-cylindrical shells. The left half shell (4) and the right half shell (5) are hinged at one end side, and the other end side can open and close along the hinge. The left half shell (4) and the right half shell (5) are joined together to form a cylindrical cavity for accommodating the test tube (12). The sleeve (1) is provided with multiple sets of marking grooves (8) with the same structure in the circumferential direction. Each set of marking grooves (8) is arranged parallel to the central axis of the sleeve (1). The marking groove (8) is a through groove with a rectangular cross-section. Each set of marking grooves (8) has a first pin hole (9) at both ends. The axis of the first pin hole (9) is located at the center line of each set of marking grooves (8). The connecting rod (2) is a flat straight rod, and a first pin (10) is provided at the center of the bottom surface of one end. The connecting rod (2) is rotatably connected to the sleeve (1) by inserting the first pin (10) into the first pin hole (9).

2. The positioning ruler for determining the bonding position of the strain gauge in the conduit according to claim 1, characterized in that: There are 4 groups of line grooves (8). The 4 groups of line grooves (8) are evenly distributed around the circumference of the hoop (1) and are symmetrically arranged on the left half shell (4) and the right half shell (5). The distance between each group of line grooves (8) and the two edges of the hoop (1) is the same. There are 2 line grooves (8) in each group. The two line grooves (8) in each group are spaced a certain distance apart.

3. The positioning ruler for determining the bonding position of the strain gauge in the conduit according to claim 1, characterized in that: The left half shell (4) and the right half shell (5) are hinged at one end by a hinge (6), and the other end is provided with a pinch handle (7) for opening and closing the left half shell (4) and the right half shell (5) around the hinge. The two pinch handles (7) fit together completely symmetrically after being pinched.

4. The positioning ruler for determining the bonding position of the strain gauge in the conduit according to claim 1, characterized in that: The other end of the connecting rod (2) is provided with a recessed platform, which faces away from the bottom surface of the connecting rod (2). A second pin hole (11) is provided at the center of the recessed platform. The axis of the second pin hole (11) and the axis of the first pin (10) are located on the central axis of the connecting rod (2).

5. The positioning ruler for determining the bonding position of the strain gauge in the conduit according to claim 4, characterized in that: The connecting rod (2) also includes an extension rod (3), which has the same cross-sectional dimensions as the connecting rod (2). The extension rod (3) is used to extend the connecting rod (2). The two ends of the extension rod (3) are provided with concave platforms in opposite directions. A second pin (18) is provided at the center of the concave surface of one end of the concave platform, and a third pin hole (19) is provided at the center of the concave platform of the other end. The axes of the second pin (18) and the third pin hole (19) are located on the central axis of the extension rod (3). The second pin (18) is embedded in the second pin hole (11) of the connecting rod (2). The concave platform at the second pin (18) of the extension rod (3) matches the concave platform at the second pin hole (11) of the connecting rod (2), so that the bottom surface of the connecting rod (2) and the bottom surface of the extension rod (3) are on the same plane.

6. The positioning ruler for determining the bonding position of the strain gauge in the conduit according to claim 5, characterized in that: The connecting rod (2) and extension rod (3) are made of hard metal.

7. A method for determining the bonding position of a strain gauge in a conduit using the positioning ruler according to any one of claims 1-6, characterized in that: The steps are as follows: Step 1: Install the clamp (1): Open the left half shell (4) and right half shell (5) of the clamp (1) along the hinge (6) and fit it onto the straight pipe section of the test conduit (12). Pinch the pinch handles (7) of the left half shell (4) and right half shell (5) symmetrically to make the clamp (1) fit against the straight pipe section of the test conduit (12), and press one end face of the clamp (1) against the end face of the constraint end (13) of the test conduit (12). Step 2, positioning of the clamp (1): Insert the first pin (10) at one end of the connecting rod (2) into the first pin hole (9) of the clamp (1), rotate and adjust the fitting angle between the clamp (1) and the straight section of the test guide (12) so that the bottom surface of the connecting rod (2) rests flat on the adjacent curved section (14); at this time, the center axis of the connecting rod (2) and the center line of the marking groove (8) where the first pin hole (9) of the connecting rod (2) is inserted determine the in-plane of the section of the test curved guide, and the positioning of the clamp (1) is completed; Step 3: Draw lines: Use a drawing pen to draw lines in each set of drawing grooves (8), remove the positioning ruler, and leave 4 sets of a total of 8 positioning lines (15) on the straight pipe section of the test guide (12) to determine the pasting position of the strain gauge (16); the drawn positioning lines (15) include the positioning lines (15) located in the plane and the positioning lines (15) located out of the plane. The in-plane refers to the plane formed after the guide is bent, and the out-of-plane refers to the direction perpendicular to the bending surface; Step 4: Attach the strain gauge (16): Take two strain gauges (16), attach one to the in-plane positioning line (15) and the other to the out-of-plane positioning line (15); when attaching, attach the strain gauge (16) between the two positioning lines (15) in the same set, and make sure that the central axis of the strain gauge (16) coincides with the two positioning lines (15).

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