Optimization Method for Connection Reliability of Flared Tube Joints

Abstract

The present invention relates to the field of fastening connections in the automotive industry, and discloses an optimization method for the connection reliability of a flared tube joint, which includes the following steps: fabricate a measurement sensor, and circumferentially paste resistance strain gauges on its inner wall; apply different magnitudes of axial compressive loads F through the indenter of a tensile testing machine, convert the change in the resistance R of the resistance strain gauges into a change in voltage V through a strain gauge, and obtain the F-V relationship expression; cut off the tapered end of the finished tube joint and replace it with the measurement sensor, connect each component by simulating the actual assembly conditions, tighten the nut to the tightening torque T, record the voltage reading V, and obtain the relationship expression between the connection axial clamping force F1 and the test torque T. Combine the sealing test results of the connection body at different torques to establish a quantitative relationship among the tightening torque of the flared tube joint, the connection axial clamping force, and the connection reliability. The optimization method for the connection reliability of the flared tube joint of the present invention realizes the measurement of the connection axial clamping force of the tube joint, has a simple structure, and is convenient to implement.

Description

Technical Field

[0001] The present invention relates to the technical field of fastening connections in the automotive industry, and particularly to an optimization method for the connection reliability of flared pipe joints. Background Art

[0002] Flared pipe joints are widely used in the automotive industry in pipeline systems where liquids or gases are used as transmission media and the pressure is relatively low, serving the functions of pipeline connection and sealing. They mainly rely on the axial clamping force generated when tightening the nut to make the flared surface at the end of the steel pipe fit tightly with the conical surfaces of the joint body and the nut to achieve sealing. Examples of related connection structures are as Figure 3 shown.

[0003] To achieve good sealing effects and improve connection reliability, the mainstream technical solutions in the industry mainly include:

[0004] 1. Optimize the dimensional machining accuracy and geometric tolerances of connection components;

[0005] 2. Increase the nut tightening torque;

[0006] 3. Tightening quality control strategies based on the axial clamping force of the connection body.

[0007] Generally speaking, Solution 1 can be combined with Solution 2 or Solution 3 for adoption.

[0008] However, the mainstream technical solutions in the industry for improving the connection reliability of flared pipe joints all have objective disadvantages or difficulties.

[0009] 1. The dimensional machining accuracy and geometric tolerances of components are closely related to the process capabilities and product inspection capabilities of their production lines. For example, Patent CN 206056474 U provides a detection device for the conical surface angle and intersection diameter of a pipe joint, but it can only solve the problem of product size screening, and limited by factors such as the performance of production and inspection equipment and cost control, the actual improvement effect of this solution is limited.

[0010] 2. The increase in nut tightening torque depends on the accurate acquisition of the tightening torque - axial clamping force relationship. Due to the closed nature of the connection structure and the absence of a structure similar to the bearing surface of a bolt or nut, it is actually difficult to measure the above relationship, and the method of finite element simulation has insufficient accuracy and cannot verify the simulation results. Therefore, connection failure problems frequently occur due to insufficient or excessive tightening during actual application.

[0011] 3. According to the theory of threaded connection, the key to ensuring connection reliability lies in achieving the design requirements for the axial clamping force of the connected body after tightening. Therefore, the tightening quality control strategy based on the axial clamping force of the connected body is currently the most effective solution theoretically. The basis for implementing this solution lies in the accurate measurement of the axial clamping force of the flared tube joint connection. However, the closed nature of the connection structure has led to the slow development of relevant measurement technologies, greatly limiting the application of this solution. Patent CN 105865665 A provides a method and device for measuring the axial clamping force of a flared tube joint. In the solution described in this patent, piezoelectric ceramic chips are pre-set outside the tube joint nut. The piezoelectric ceramic chips generate acoustic wave signals based on voltage signals, and the change in the nut length is converted from the time difference of receiving different acoustic wave signals before and after nut tightening. Then, the axial clamping force is obtained from the pre-acquired elastic coefficient. The above patent solution can perform real-time measurement of the axial clamping force of the connected body, but has the following deficiencies: 1. The change in the nut length before and after tightening is extremely small, and indirectly converting the length change from the time difference of acoustic wave signals increases the measurement error; 2. The dedicated detection equipment results in a relatively high application threshold. Summary of the Invention

[0012] The object of the present invention is to address the deficiencies of the above technologies and provide an optimization method for the connection reliability of a flared tube joint, which can achieve the measurement of the axial clamping force of the tube joint connection, with a simple structure and easy to implement.

[0013] To achieve the above object, the optimization method for the connection reliability of a flared tube joint designed by the present invention includes the following steps:

[0014] A) Fabricate a measurement sensor: Machine a measurement sensor that simulates the tapered end of the tube joint, and circumferentially paste several resistance strain gauges on its inner wall.

[0015] B) Calibrate the measurement sensor: Apply different magnitudes of axial compressive loads F through the indenter of a tensile testing machine, and convert the change in the resistance R of the resistance strain gauges in the measurement sensor into a change in voltage V through a strain gauge to obtain the F-V relationship expression.

[0016] C) Measurement: Cut off the tapered end of the finished tube joint and replace it with the measurement sensor. Connect all components under simulated actual assembly conditions, tighten the nut to the tightening torque T, record the voltage reading V, calculate the connection axial clamping force F1 at this time according to the F-V expression, and then obtain the relationship expression between the connection axial clamping force F1 and the test torque T.

[0017] D) Connection reliability optimization strategy: According to the relationship expression between the connection axial clamping force F1 and the tightening torque T obtained in step C), combined with the test results of the connection body sealability at different torques, establish a quantitative relationship between the tightening torque of the flared tube joint, the connection axial clamping force, and the connection reliability.

[0018] Preferably, in the step A), the measuring sensor is reusable.

[0019] Preferably, in the step A), the taper angle and surface roughness of the measuring sensor are consistent with the technical requirements of the pipe joint.

[0020] Preferably, in the step A), the inner wall of the measuring sensor is bright and clean, and the surface roughness Ra ≤ 1.6.

[0021] Preferably, in the step A), the material of the measuring sensor is low alloy steel treated by modulation to obtain good mechanical properties and avoid obvious plastic deformation during the tightening process.

[0022] Preferably, in the step A), the outer diameter of the measuring sensor is smaller than the minor diameter of the pipe joint thread, and its length is reduced as much as possible without affecting subsequent measurements to prevent interference problems during the tightening process of the thread pair.

[0023] Preferably, in the step A), the sensitive grid of the resistance strain gauge is parallel to the axis of the measuring sensor so that it can reflect the axial force condition. The resistance strain gauge has good stability, and the strain limit is not less than the maximum strain of the measuring sensor.

[0024] Preferably, in the step B), no eccentric load should occur during the process of the axial compressive load applied by the indenter of the tensile testing machine. To ensure the measurement accuracy and sensitivity, the resistance strain gauges are formed into a half-bridge wiring structure.

[0025] Preferably, in the step C), the surface treatment of the finished pipe joint should be carried out after cutting the tapered end to avoid large changes in its surface state.

[0026] Preferably, in the step C), for the tightening tool used, its torque measurement accuracy should be consistent with the actual assembly conditions of the production line.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] 1. Utilizing the special connection structure of the flared pipe joint, a special dedicated sensor is designed to realize the measurement of the axial clamping force of the pipe joint connection;

[0029] 2. Developing a method for establishing the quantitative relationship between the tightening torque, axial clamping force and sealing performance of the flared pipe joint connection;

[0030] 3. The scheme is easy to implement, has less equipment investment, high result reliability, can realize the measurement of the axial clamping force of various flared pipe joint connections, and has a wide application prospect in aspects such as connection structure design, assembly process formulation, and connection reliability research, and has significant social benefits. Brief Description of the Drawings

[0031] Figure 1 It is a schematic flow chart of the method for optimizing the connection reliability of the flared pipe joint of the present invention;

[0032] Figure 2 It is a schematic installation diagram of the measurement sensor used in the present invention;

[0033] Figure 3 It is a schematic installation diagram of the flared surface at the end of the steel pipe and the joint body and nut in the prior art.

[0034] The reference numerals of each component in the figure are as follows:

[0035] Pipe joint 1, nut 2, measurement sensor 3, flared steel pipe 4. Detailed Embodiment

[0036] Next, the technical solution of the present invention will be clearly and completely described in conjunction with the drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0037] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0038] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "installation", "connection", "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0039] Embodiment 1

[0040] As Figure 1 shown, a method for optimizing the connection reliability of a flared pipe joint includes the following steps:

[0041] A) Fabricate the measurement sensor 3: Machine the measurement sensor 3 that simulates the tapered end of the pipe fitting 1, and paste several resistance strain gauges circumferentially on its inner wall;

[0042] B) Calibrate the measurement sensor 3: Apply axial compressive loads F of different magnitudes through the indenter of the tensile testing machine, and convert the change in resistance R of the resistance strain gauges in the measurement sensor 3 into a change in voltage V through a strain gauge to obtain the F-V relationship expression;

[0043] C) Measurement: Cut off the tapered end of the finished pipe fitting 1 and replace it with the measurement sensor 3. As Figure 2 shown, connect all components under simulated actual assembly conditions, install them on the flared steel pipe 4, tighten the nut 2 to the tightening torque T, record the voltage reading V, calculate the connection axial clamping force F1 at this time according to the F-V expression, and then obtain the relationship expression between the connection axial clamping force F1 and the test torque T;

[0044] D) Connection reliability optimization strategy: According to the relationship expression between the connection axial clamping force F1 and the tightening torque T obtained in step C), combined with the connection body sealing test results at different torques, establish a quantitative relationship between the tightening torque of the flared pipe fitting, the connection axial clamping force, and the connection reliability.

[0045] Example 2

[0046] A method for optimizing the connection reliability of a flared pipe fitting includes the following steps:

[0047] A) Fabricate the measurement sensor 3: Machine the measurement sensor 3 that simulates the tapered end of the pipe fitting 1, and paste several resistance strain gauges circumferentially on its inner wall. The measurement sensor 3 can be reused;

[0048] B) Calibrate the measurement sensor 3: Apply axial compressive loads F of different magnitudes through the indenter of the tensile testing machine, and convert the change in resistance R of the resistance strain gauges in the measurement sensor 3 into a change in voltage V through a strain gauge to obtain the F-V relationship expression;

[0049] C) Measurement: Cut off the tapered end of the finished pipe fitting 1 and replace it with the measurement sensor 3. Connect all components under simulated actual assembly conditions, tighten the nut 2 to the tightening torque T, record the voltage reading V, calculate the connection axial clamping force F1 at this time according to the F-V expression, and then obtain the relationship expression between the connection axial clamping force F1 and the test torque T;

[0050] D) Connection reliability optimization strategy: According to the relationship expression between the connection axial clamping force F1 and the tightening torque T obtained in step C), combined with the connection body sealing test results at different torques, establish a quantitative relationship between the tightening torque of the flared pipe fitting, the connection axial clamping force, and the connection reliability.

[0051] Example 3

[0052] An optimization method for the connection reliability of a flared pipe joint includes the following steps:

[0053] A) Fabricate the measurement sensor 3: Machine the measurement sensor 3 that simulates the tapered end of the pipe joint 1, and paste several resistance strain gauges circumferentially on its inner wall. The measurement sensor 3 can be reused. The taper angle and surface roughness of the measurement sensor 3 are consistent with the technical requirements of the pipe joint 1. The inner wall of the measurement sensor 3 is bright and clean, and the surface roughness Ra ≤ 1.6;

[0054] B) Calibrate the measurement sensor 3: Apply different magnitudes of axial compressive loads F through the indenter of a tensile testing machine, and convert the change in the resistance R of the resistance strain gauges in the measurement sensor 3 into a change in voltage V through a strain gauge to obtain the F-V relationship expression;

[0055] C) Measurement: Cut off the tapered end of the finished pipe joint 1 and replace it with the measurement sensor 3. Connect all components under simulated actual assembly conditions, tighten the nut 2 to the tightening torque T, record the voltage reading V, calculate the connection axial clamping force F1 at this time according to the F-V expression, and then obtain the relationship expression between the connection axial clamping force F1 and the test torque T;

[0056] D) Connection reliability optimization strategy: According to the relationship expression between the connection axial clamping force F1 and the tightening torque T obtained in step C), combined with the test results of the connection body sealing performance at different torques, establish a quantitative relationship between the tightening torque of the flared pipe joint, the connection axial clamping force, and the connection reliability.

[0057] Example 4

[0058] An optimization method for the connection reliability of a flared pipe joint includes the following steps:

[0059] A) Fabricate the measurement sensor 3: Machine the measurement sensor 3 that simulates the tapered end of the pipe joint 1, and paste several resistance strain gauges circumferentially on its inner wall. The measurement sensor 3 can be reused. The taper angle and surface roughness of the measurement sensor 3 are consistent with the technical requirements of the pipe joint 1. The inner wall of the measurement sensor 3 is bright and clean, and the surface roughness Ra ≤ 1.6. The material of the measurement sensor 3 is low alloy steel with quenching and tempering treatment. The outer diameter of the measurement sensor 3 is smaller than the minor diameter of the thread of the pipe joint 1, and its length is reduced as much as possible without affecting subsequent measurements to prevent interference problems during the tightening process of the thread pair;

[0060] B) Calibrate the measurement sensor 3: Apply different magnitudes of axial compressive loads F through the indenter of a tensile testing machine, and convert the change in the resistance R of the resistance strain gauges in the measurement sensor 3 into a change in voltage V through a strain gauge to obtain the F-V relationship expression;

[0061] C) Measurement: Cut off the tapered end of the finished fitting 1, replace it with the measurement sensor 3, connect all components under simulated actual assembly conditions, tighten the nut 2 to the tightening torque T, record the voltage reading V, calculate the connection axial clamping force F1 at this time according to the F-V expression, and then obtain the relationship expression between the connection axial clamping force F1 and the test torque T;

[0062] D) Connection reliability optimization strategy: According to the relationship expression between the connection axial clamping force F1 and the tightening torque T obtained in step C), combined with the connection body sealability test results at different torques, establish a quantitative relationship between the tightening torque of the flared fitting, the connection axial clamping force, and the connection reliability.

[0063] Example 5

[0064] A method for optimizing the connection reliability of a flared fitting includes the following steps:

[0065] A) Fabricate the measurement sensor 3: Machine the measurement sensor 3 that simulates the tapered end of the fitting 1, and paste several resistance strain gauges circumferentially on its inner wall. The measurement sensor 3 can be reused. The tapered angle and surface roughness of the measurement sensor 3 are consistent with the technical requirements of the fitting 1. The inner wall of the measurement sensor 3 is bright and clean, with a surface roughness Ra ≤ 1.6. The material of the measurement sensor 3 is low alloy steel with tempering treatment. The outer diameter of the measurement sensor 3 is smaller than the minor diameter of the thread of the fitting 1, and its length is reduced as much as possible without affecting subsequent measurements to prevent interference problems during the tightening process of the thread pair. The sensitive grid of the resistance strain gauge is parallel to the axis of the measurement sensor 3;

[0066] B) Calibrate the measurement sensor 3: Apply different magnitudes of axial compressive loads F through the indenter of the tensile testing machine, convert the change in the resistance R of the resistance strain gauges in the measurement sensor 3 into a change in voltage V through the strain gauge, and obtain the F-V relationship expression;

[0067] C) Measurement: Cut off the tapered end of the finished fitting 1, replace it with the measurement sensor 3, connect all components under simulated actual assembly conditions, tighten the nut 2 to the tightening torque T, record the voltage reading V, calculate the connection axial clamping force F1 at this time according to the F-V expression, and then obtain the relationship expression between the connection axial clamping force F1 and the test torque T;

[0068] D) Connection reliability optimization strategy: According to the relationship expression between the connection axial clamping force F1 and the tightening torque T obtained in step C), combined with the connection body sealability test results at different torques, establish a quantitative relationship between the tightening torque of the flared fitting, the connection axial clamping force, and the connection reliability.

[0069] Example 6

[0070] An optimization method for the connection reliability of a flared pipe joint, comprising the following steps:

[0071] A) Fabricate the measurement sensor 3: Machine the measurement sensor 3 that simulates the tapered end of the pipe joint 1, and paste several resistance strain gauges circumferentially on its inner wall. The measurement sensor 3 can be reused. The taper angle and surface roughness of the measurement sensor 3 are consistent with the technical requirements of the pipe joint 1. The inner wall of the measurement sensor 3 is bright and clean, with a surface roughness Ra ≤ 1.6. The material of the measurement sensor 3 is low alloy steel with tempering treatment. The outer diameter of the measurement sensor 3 is smaller than the minor diameter of the thread of the pipe joint 1, and its length is minimized as much as possible without affecting subsequent measurements to prevent interference problems during the tightening process of the thread pair. The sensitive grid of the resistance strain gauge is parallel to the axis of the measurement sensor 3. The resistance strain gauge has good stability, and the strain limit is not less than the maximum strain of the measurement sensor 3;

[0072] B) Calibrate the measurement sensor 3: Apply different magnitudes of axial compressive loads F through the indenter of the tensile testing machine, and convert the change in resistance R of the resistance strain gauges in the measurement sensor 3 into a change in voltage V through a strain gauge to obtain the F-V relationship expression;

[0073] C) Measurement: Cut off the tapered end of the finished pipe joint 1 and replace it with the measurement sensor 3. Connect all components by simulating the actual assembly conditions, tighten the nut 2 to the tightening torque T, record the voltage reading V, calculate the connection axial clamping force F1 at this time according to the F-V expression, and then obtain the relationship expression between the connection axial clamping force F1 and the test torque T;

[0074] D) Connection reliability optimization strategy: According to the relationship expression between the connection axial clamping force F1 and the tightening torque T obtained in step C), combined with the test results of the connection body sealing performance at different torques, establish a quantitative relationship among the tightening torque of the flared pipe joint, the connection axial clamping force, and the connection reliability.

[0075] Example 7

[0076] An optimization method for the connection reliability of a flared pipe joint, comprising the following steps:

[0077] A) Fabricating the measurement sensor 3: Machine the measurement sensor 3 at the tapered end of the simulated pipe joint 1, and paste several resistance strain gauges circumferentially on its inner wall. The measurement sensor 3 can be reused. The taper angle and surface roughness of the measurement sensor 3 are consistent with the technical requirements of the pipe joint 1. The inner wall of the measurement sensor 3 is bright and clean, with a surface roughness Ra ≤ 1.6. The material of the measurement sensor 3 is low alloy steel with quenching and tempering treatment. The outer diameter of the measurement sensor 3 is smaller than the minor diameter of the thread of the pipe joint 1, and its length is minimized as much as possible without affecting subsequent measurements to prevent interference problems during the tightening process of the thread pair. The sensitive grid of the resistance strain gauge is parallel to the axis of the measurement sensor 3. The resistance strain gauge has good stability, and the strain limit is not less than the maximum strain of the measurement sensor 3;

[0078] B) Calibrating the measurement sensor 3: Apply different magnitudes of axial compressive loads F through the indenter of the tensile testing machine, convert the change in resistance R of the resistance strain gauges in the measurement sensor 3 into a change in voltage V through a strain gauge, and obtain the F-V relationship expression. During the process of applying the axial compressive load by the indenter of the tensile testing machine, no eccentric loading should occur. To ensure measurement accuracy and sensitivity, form a half-bridge wiring structure for the resistance strain gauges;

[0079] C) Measuring: Cut off the tapered end of the finished pipe joint 1 and replace it with the measurement sensor 3. Connect all components under simulated actual assembly conditions, tighten the nut 2 to the tightening torque T, record the voltage reading V, and calculate the connection axial clamping force F1 at this time according to the F-V expression, and then obtain the relationship expression between the connection axial clamping force F1 and the test torque T;

[0080] D) Connection reliability optimization strategy: According to the relationship expression between the connection axial clamping force F1 and the tightening torque T obtained in step C), combined with the test results of the connection body sealing performance at different torques, establish a quantitative relationship between the tightening torque of the flared pipe joint, the connection axial clamping force, and the connection reliability.

[0081] Example 8

[0082] An optimization method for the connection reliability of a flared pipe joint, comprising the following steps:

[0083] A) Fabricate the measurement sensor 3: Machine the measurement sensor 3 for the tapered end of the analog pipe joint 1, and paste several resistance strain gauges circumferentially on its inner wall. The measurement sensor 3 can be reused. The taper angle and surface roughness of the measurement sensor 3 are consistent with the technical requirements of the pipe joint 1. The inner wall of the measurement sensor 3 is bright and clean, with a surface roughness Ra ≤ 1.6. The material of the measurement sensor 3 is low alloy steel with quenching and tempering treatment. The outer diameter of the measurement sensor 3 is smaller than the minor diameter of the thread of the pipe joint 1, and its length is reduced as much as possible without affecting subsequent measurements to prevent interference problems during the tightening process of the thread pair. The sensitive grid of the resistance strain gauge is parallel to the axis of the measurement sensor 3. The resistance strain gauge has good stability, and the strain limit is not less than the maximum strain of the measurement sensor 3;

[0084] B) Calibrate the measurement sensor 3: Apply axial compressive loads F of different magnitudes through the indenter of the tensile testing machine. Convert the change in resistance R of the resistance strain gauges in the measurement sensor 3 into a change in voltage V through a strain gauge to obtain the F-V relationship expression. There should be no off-axis loading during the process of applying the axial compressive load by the indenter of the tensile testing machine. To ensure measurement accuracy and sensitivity, form a half-bridge wiring structure for the resistance strain gauges;

[0085] C) Measurement: Cut off the tapered end of the finished pipe joint 1 and replace it with the measurement sensor 3. Connect all components by simulating the actual assembly conditions, tighten the nut 2 to the tightening torque T, record the voltage reading V, calculate the connection axial clamping force F1 at this time according to the F-V expression, and then obtain the relationship expression between the connection axial clamping force F1 - test torque T. The surface treatment of the finished pipe joint 1 should be carried out after cutting off the tapered end. For the tightening tool used, its torque measurement accuracy should be consistent with the actual assembly conditions of the production line;

[0086] D) Connection reliability optimization strategy: According to the relationship expression between the connection axial clamping force F1 - tightening torque T obtained in step C), combined with the test results of the connection body sealing performance at different torques, establish a quantitative relationship between the tightening torque of the flared pipe joint, the connection axial clamping force, and the connection reliability.

[0087] Taking specific test data as an example:

[0088] A method for optimizing the connection reliability of a flared pipe joint includes the following steps:

[0089] A) Fabrication of the measurement sensor 3: Machine the measurement sensor 3 at the tapered end of the simulated pipe joint 1, and paste 4 resistance strain gauges circumferentially on its inner wall, numbered A, B, C, and D. The measurement sensor 3 can be reused. The taper angle and surface roughness of the measurement sensor 3 are consistent with the technical requirements of the pipe joint 1. The inner wall of the measurement sensor 3 is bright and clean, with a surface roughness Ra ≤ 1.6. The material of the measurement sensor 3 is low alloy steel with quenching and tempering treatment. The outer diameter of the measurement sensor 3 is smaller than the minor diameter of the thread of the pipe joint 1, and its length is minimized as much as possible without affecting subsequent measurements to prevent interference during the tightening process of the thread pair. The sensitive grid of the resistance strain gauge is parallel to the axis of the measurement sensor 3. The resistance strain gauge has good stability, and the strain limit is not less than the maximum strain of the measurement sensor 3;

[0090] B) Calibration of the measurement sensor 3: Apply different magnitudes of axial compressive loads F through the indenter of the tensile testing machine. Convert the change in resistance R of the resistance strain gauges in the measurement sensor 3 into a change in voltage V through a strain gauge to obtain the F-V relationship expression. No eccentric loading should occur during the process of applying the axial compressive load by the indenter of the tensile testing machine. To ensure measurement accuracy and sensitivity, form a half-bridge wiring structure for the resistance strain gauges. The calibration results are shown in Table 1:

[0091] Table 1. Calibration results of the measurement sensor 3

[0092] Strain gauge number F-V relationship <![CDATA[Fitness R 2 > A F = 0.0181V 0.9769 B F = 0.0294V 0.9986 C F = 0.0173V 0.9189 D F = 0.0297V 0.9980

[0093] Note: In the F-V relationship expression, the unit of F is kN, and the unit of V is mV;

[0094] C) Measurement: Cut off the tapered end of the finished pipe joint 1 and replace it with the measurement sensor 3. Connect all components under simulated actual assembly conditions, tighten the nut 2 to the tightening torque T, record the voltage reading V, calculate the connection axial clamping force F1 at this time according to the F-V expression, and then obtain the relationship expression between the connection axial clamping force F1 and the test torque T. The surface treatment of the finished pipe joint 1 should be carried out after cutting off the tapered end. The torque measurement accuracy of the tightening tool used should be consistent with the actual assembly conditions of the production line. In this embodiment, there are 5 sample parts. The axial clamping forces of the 1# - 5# sample parts when the surface of the connection thread pair of the pipe joint 1 is not coated are shown in Table 2:

[0095] Table 2. Axial clamping forces of the 1# - 5# sample parts when the surface of the connection thread pair of the pipe joint is not coated

[0096]

[0097]

[0098] Note: Under each test torque condition, the axial clamping force takes the average value of the calculation results of the A, B, C, and D resistance strain gauges;

[0099] When the surface of the pipe joint connection thread pair is coated, the axial clamping forces of Specimens 1# to 5# are shown in Table 3 as follows:

[0100] Table 3. Axial clamping forces of Specimens 1# to 5# when the surface of the pipe joint connection thread pair is coated

[0101]

[0102] Note: Under each test torque condition, the axial clamping force is the average value of the calculation results of strain gauges A, B, C, and D.

[0103] D) Connection reliability optimization strategy: According to the relational expression of the connection axial clamping force F1 - tightening torque T obtained in step C), combined with the test results of the connection body sealing performance at different torques, establish the quantitative relationship between the tightening torque of the flared pipe joint, the connection axial clamping force, and the connection reliability, as shown in Table 4, to verify the F1 - T relational expression corresponding to whether the surface of the connection thread pair of Pipe Joint 1 is coated:

[0104] Table 4. F1 - T relational expressions corresponding to whether the surface of the pipe joint connection thread pair is coated

[0105]

[0106]

[0107] Note: In the T - F1 relational expression, the unit of F1 is kN and the unit of T is Nm.

[0108] Conclusion: After the surface of the connection thread pair of the flared straight - through pipe joint for the test is coated, under the same tightening torque condition, the axial clamping force will increase significantly, and the increase amplitude can reach 120%.

[0109] The connection reliability optimization method of the flared pipe joint of the present invention utilizes the special connection structure of the flared pipe joint, designs a special dedicated sensor to measure the axial clamping force of the pipe joint connection; develops a method for establishing the quantitative relationship between the tightening torque, the axial clamping force, and the sealing performance of the flared pipe joint connection; the scheme is easy to implement, has less equipment investment, high result reliability, and can measure the axial clamping force of various flared pipe joint connections, and has a wide application prospect in aspects such as connection structure design, assembly process formulation, and connection reliability research, and has significant social benefits.

[0110] Here, it should be noted that the description of the above technical solution is exemplary. This specification can be embodied in different forms and should not be construed as limited to the technical solutions set forth herein. On the contrary, providing these descriptions will make the disclosure of the present invention thorough and complete, and will fully convey the scope disclosed in this specification to those skilled in the art. In addition, the technical solutions of the present invention are only defined by the scope of the claims.

[0111] The examples used to describe the various aspects disclosed in this specification and the claims are merely examples, and thus, this specification and the claims are not limited to the details shown. In the above description, when the detailed description of related known functions or configurations is determined to unnecessarily obscure the key points of this specification and the claims, the detailed description will be omitted.

[0112] When using the terms "comprising", "having", and "including" described in this specification, unless otherwise stated, it may also have another part or other parts, and the terms used may generally be in the singular but may also represent the plural form.

[0113] Finally, it should be pointed out that the above content is a further detailed description of the invention in combination with specific embodiments. It cannot be considered that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the art to which the present invention pertains, without departing from the concept of the present invention, simple substitutions made should be regarded as belonging to the protection scope of the present invention. The above embodiments are only relatively representative examples of the present invention. Obviously, the present invention is not limited to the above embodiments and there can be many variations. Any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention should be regarded as belonging to the protection scope of the present invention.

[0114] At the same time, it should be noted that the description of the above technical solution is exemplary. This specification can be embodied in different forms and should not be construed as limited to the technical solutions set forth herein. On the contrary, providing these descriptions will make the disclosure of the present invention thorough and complete, and will fully convey the scope disclosed in this specification to those skilled in the art. In addition, the technical solutions of the present invention are only defined by the scope of the claims. The features of the various embodiments of the present invention can be combined or pieced together partially or entirely with each other, and can be implemented in various different configurations as can be fully understood by those skilled in the art. The embodiments of the present invention can be implemented independently of each other, or can be implemented together in a mutually dependent relationship.

[0115] For those of ordinary skill in the art to which the present invention pertains, without departing from the concept of the present invention, several simple deductions or substitutions can also be made, and the above structures should all be regarded as belonging to the protection scope of the present invention.

Claims

1. An optimization method for the connection reliability of a flared tube joint, characterized in that: It includes the following steps: A) Fabricate the measurement sensor: Machine the measurement sensor for the tapered end of the analog pipe joint, and paste several resistance strain gauges circumferentially on its inner wall. The outer diameter of the measurement sensor is smaller than the minor diameter of the pipe joint thread, and its length is minimized as much as possible without affecting subsequent measurements to prevent interference problems during the tightening process of the thread pair. The sensitive grid of the resistance strain gauge is parallel to the axis of the measurement sensor. The resistance strain gauge has good stability, and its strain limit is not less than the maximum strain of the measurement sensor; B) Calibrate the measurement sensor: Apply axial compressive loads F of different magnitudes through the indenter of the tensile testing machine. Convert the change in resistance R of the resistance strain gauges in the measurement sensor into a change in voltage V through a strain gauge to obtain the F-V relationship expression. During the process of applying the axial compressive load by the indenter of the tensile testing machine, no eccentric loading should occur. To ensure measurement accuracy and sensitivity, form a half-bridge wiring structure for the resistance strain gauges; C) Measure: Cut off the tapered end of the finished pipe joint and replace it with the measurement sensor. Connect all components to simulate the actual assembly conditions, tighten the nut to the tightening torque T, record the voltage reading V, calculate the connection axial clamping force F1 at this time according to the F-V expression, and then obtain the relationship expression between the connection axial clamping force F1 and the test torque T; D) Connection reliability optimization strategy: According to the relationship expression between the connection axial clamping force F1 and the tightening torque T obtained in step C), combined with the test results of the connection body sealability at different torques, establish a quantitative relationship between the tightening torque of the flared pipe joint, the connection axial clamping force, and the connection reliability.

2. The method for optimizing the connection reliability of the flared tube joint according to claim 1, wherein: In step A), the measurement sensor can be reused.

3. The method for optimizing the connection reliability of the flared tube joint according to claim 1, wherein: In step A), the tapered angle and surface roughness of the measurement sensor are consistent with the technical requirements of the pipe joint.

4. The optimized method for the connection reliability of the flared tube joint according to claim 1, wherein: In step A), the inner wall of the measurement sensor is bright and clean, and the surface roughness Ra ≤ 1.

6.

5. The optimized method for the connection reliability of the flared tube joint according to claim 1, characterized in that: In step A), the material of the measurement sensor is low alloy steel subjected to quenching and tempering treatment.

6. The optimized method for the connection reliability of the flared tube joint according to claim 1, characterized in that: In step C), the surface treatment of the finished pipe joint should be carried out after cutting off the tapered end.

7. The optimized method for the connection reliability of the flared tube joint according to claim 1, wherein: In step C), for the tightening tool used, its torque measurement accuracy should be consistent with the actual assembly conditions of the production line.

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