Method for evaluating connection strength of axial extrusion pipeline joint

Abstract

The invention discloses a method for evaluating the connection strength of an axial extrusion pipeline joint. The minimum connection strength Fmin of a pipe joint is # imgabs0 #. According to the method, the minimum connection strength of the pipe joint can be evaluated through size measurement and working pressure measurement and calculation, and the method can be used for calculation of the connection strength of axial extrusion joints of different sizes. According to the method, the test cost is reduced, the design period is shortened, the design efficiency is effectively improved, and good practicability is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of aircraft piping system assembly, and in particular relates to a method for evaluating the connection strength of an axially extruded piping joint. Background Art

[0002] Pipe fittings are crucial components in connecting pipe systems, and their performance directly impacts the sealing, strength, and durability of the entire system. Testing pipe fittings involves multiple aspects, including mechanical properties, sealing performance, corrosion resistance, and pressure resistance, to ensure they operate safely and reliably in diverse environments. Mechanical performance testing aims to assess the tensile strength, yield strength, and hardness of pipe fittings, ensuring they do not break or deform during use. A tensile strength test involves applying a tensile force using a tensile testing machine to determine the maximum tensile strength of a material. A yield strength test assesses the maximum stress a material can withstand before permanent deformation begins. A hardness test uses Rockwell hardness and Brinell hardness methods to assess the hardness of the fitting material, ensuring it possesses sufficient resistance to wear and pressure. Pipe fitting connection strength is a design indicator for pipe fittings, evaluating whether the structural connection force meets requirements when subjected to axial loads. Currently, domestic testing of pipe fitting connection strength is generally conducted through physical testing, which increases the design cycle and cost of pipe fittings. Methods for accurately estimating joint connection strength in advance using theoretical calculations are still largely unavailable in China. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for evaluating the connection strength of an axially extruded pipe joint, aiming to solve the above-mentioned problem.

[0004] The present invention is mainly achieved through the following technical solutions:

[0005] A method for evaluating the connection strength of axially extruded pipe joints. The minimum connection strength F of the pipe joint is min for:

[0006] F min ≥K3(F Z +F f ) (6)

[0007] Where: K3 is the safety factor;

[0008] F Z The axial force between the inner ring of the pipe joint and the conduit at the sealing position of the pipe joint;

[0009] F f The friction force generated by the radial force of the catheter.

[0010] In order to better realize the present invention, further, F Z The calculation formula is:

[0011]

[0012] Among them: K1 is a constant term;

[0013] R is the diameter of the catheter;

[0014] μ1 is the friction force between the groove of the inner ring of the joint and the catheter;

[0015] P0 is the working pressure of the pipeline;

[0016] h is the contact depth between the groove of the inner ring of the joint and the conduit;

[0017] H is the groove depth of the inner ring of the joint.

[0018] In order to better realize the present invention, further, F f The calculation formula is:

[0019]

[0020] Where: L is the contact length between the groove of the inner ring of the joint and the conduit;

[0021] F(x) is the contact surface pressure;

[0022] μ2 is the friction force between the inner ring of the joint excluding the groove and the catheter.

[0023] In order to better implement the present invention, further, the minimum connection strength F of the pipe joint min for:

[0024]

[0025] In order to better implement the present invention, the following steps are further included:

[0026] Step S1: Determine the sealing position dimensions of the pipe joint and the working pressure P0 of the pipe joint according to the structure and working conditions of the pipe joint; the sealing position dimensions include the conduit diameter R, the contact depth h between the groove of the inner ring of the joint and the conduit, and the groove depth H of the inner ring of the joint;

[0027] Step S2: Calculate the axial force F between the inner ring of the pipe joint and the pipe at the sealing position of the pipe joint Z for:

[0028]

[0029] Among them: K1 is a constant term;

[0030] μ1 is the friction force between the groove of the inner ring of the joint and the catheter;

[0031] Step S3: Calculate the radial force F between the inner ring of the joint and the catheter j , the contact area between the inner ring of the joint and the catheter is equivalent to a region with an equivalent elastic modulus E * The contact between the elastic cylinder and the rigid plane, with the contact center as the coordinate origin, the contact pressure F j (x) is:

[0032]

[0033] Where: K2 is the correction coefficient;

[0034] L is the contact length between the groove of the inner ring of the joint and the catheter;

[0035] x is the contact length between the groove of the inner ring of the joint and the catheter;

[0036] Step S4: Calculate radial force F j The friction force F f :

[0037]

[0038] Where: μ2 is the friction force between the inner ring of the joint excluding the groove and the catheter;

[0039] Step S5: Calculate the minimum connection strength F of the pipe joint min :

[0040]

[0041] Among them: K3 is the safety factor.

[0042] In order to better implement the present invention, further, in step S3, the equivalent elastic modulus E * The calculation formula is as follows:

[0043]

[0044] The contact pressure F of the contact surface is j (x) is:

[0045]

[0046] Where: E S is the elastic modulus of the inner ring of the joint (MPa);

[0047] E c is the elastic modulus of the catheter (MPa);

[0048] Vs is the Poisson’s ratio of the inner ring material of the joint;

[0049] Vc is the Poisson's ratio of the catheter material.

[0050] The beneficial effects of the present invention are as follows:

[0051] The present invention can evaluate the minimum connection strength of a pipe joint by measuring dimensions and calculating working pressure, and can be used to calculate the connection strength of axial extrusion joints of different sizes. This invention reduces testing costs, shortens the design cycle, effectively improves design efficiency, and has good practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 This is a schematic structural diagram of the axially extruded pipe joint of the present invention;

[0053] Figure 2 It is a force diagram of the axially extruded pipe joint of the present invention.

[0054] Among them: 1-connector outer ring, 2-connector inner ring, 3-conduit. DETAILED DESCRIPTION

[0055] Example 1:

[0056] A method for evaluating the connection strength of an axially extruded pipe joint, for accurately estimating the connection strength of an axially extruded joint in advance, comprises the following steps:

[0057] Step 1: Determine the structural dimensions and working pressure of the pipe joint: Determine the sealing position dimensions and working pressure of the pipe joint according to the structure and working conditions of the pipe joint.

[0058] Step 2: Calculate the axial force F between the inner ring 2 of the joint and the conduit 3 Z :According to the structure and assembly relationship of the pipe joint, considering the elastic-plastic deformation of the material during the connection process, the axial force at the sealing position of the pipe joint is calculated using methods including but not limited to theoretical and numerical calculations:

[0059]

[0060] in:

[0061] P0 is the pipeline working pressure (MPa);

[0062] h is the contact depth between the groove of the joint inner ring 2 and the conduit 3 (mm);

[0063] H is the groove depth of the joint inner ring 2 (mm);

[0064] R is the diameter of the catheter 3 (mm);

[0065] μ1 is the friction force between the groove of the inner ring 2 of the joint and the conduit 3;

[0066] K1 is a constant term.

[0067] Step 3: Calculate the radial force F between the inner ring 2 and the conduit 3 j :The contact area between the inner ring 2 of the joint and the conduit 3 is equivalent to the contact between an elastic cylinder with an equivalent elastic modulus E and a rigid plane. The contact center is taken as the coordinate origin, and the contact pressure F of the contact surface is j (x) is:

[0068]

[0069] in:

[0070] R is the diameter of the catheter 3 (mm);

[0071] L is the contact length between the groove of the joint inner ring 2 and the conduit 3 (mm);

[0072] K2 is the correction coefficient, which is a constant term;

[0073] x is the contact length between the groove of the inner ring 2 of the joint and the conduit 3, both of which can be set directly;

[0074] E * is the equivalent elastic modulus. The calculation formula is:

[0075]

[0076] in:

[0077] E * is the equivalent elastic modulus (MPa);

[0078] E S is the elastic modulus of the inner ring 2 of the joint (MPa);

[0079] E c is the elastic modulus of the catheter 3 (MPa);

[0080] Vs is the Poisson's ratio of the material of the inner ring 2 of the joint;

[0081] Vc is the Poisson's ratio of the conduit 3 material.

[0082] Step 4: Calculate the friction force F generated by the radial force f :

[0083]

[0084] in:

[0085] L is the half width of the contact surface between the joint inner ring 2 and the conduit 3;

[0086] F(x) is the contact surface pressure; F(x) is just F j part of (x);

[0087] μ1 is the friction force between the groove of the inner ring 2 of the joint and the conduit 3

[0088] μ2 is the friction force between the inner ring 2 of the joint and the conduit 3 except for the groove;

[0089] Step 5. Calculate the minimum pull-off resistance of the pipe joint:

[0090] F min ≥K3(F Z +F f )(6)

[0091] Right now:

[0092]

[0093] Among them: K3 is the safety factor, which can be set directly;

[0094] The minimum pull-off resistance value is the minimum connection strength value of the pipe joint.

[0095] Example 2:

[0096] A method for evaluating the connection strength of axially extruded pipe joints, for aircraft axially extruded joints, such as Figure 1 As shown, the axial extrusion joint includes a joint outer ring 1, a joint inner ring 2 and a conduit 3 arranged in sequence from top to bottom. The following steps are included:

[0097] Step 1: Figure 2 As shown, determine the pipe joint structure size and working pressure, where the working pressure is 35Mpa;

[0098] Step 2: Calculate the axial force F between the inner ring 2 of the joint and the conduit 3 Z :

[0099]

[0100] in:

[0101] μ1 is 0.3; p is 35 MPa; h is 0.12 mm; H is 0.16 mm; R is 6 mm; K1 is 8; by including but not limited to formula (2) and the finite element method, the axial force Fz at the sealing area position can be calculated to be 1560 N.

[0102] Step 3: Calculate the radial force F in the contact area j :

[0103]

[0104] in:

[0105] E S 110000MPa; E cis 108000MPa; Vs is 0.33; V C =0.33; L =0.4mm; R =6mm. By including but not limited to formula (8) and finite element method, the radial force F in the sealing area can be calculated: j for:

[0106]

[0107] Step 4: Calculate the friction force F generated by the radial force f

[0108]

[0109] The friction force F generated by the radial force can be calculated by using the finite element method including but not limited to formula (5): f It is 2395N.

[0110] Step 5. Calculate the minimum pull-off resistance of the pipe joint:

[0111] F min ≥K3(F Z +F f )=1.1×(1560+2395)=4350N

[0112] The actual measured value is 4556N. The error between the calculated value and the measured value in this embodiment is within 5%. Therefore, the evaluation method of the present invention has high reliability, reduces test costs, shortens the design cycle, effectively improves design efficiency, and has good practicality.

[0113] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification or equivalent change made to the above embodiment based on the technical essence of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A method for evaluating the connection strength of an axially extruded pipe joint, characterized in that: Minimum connection strength F of pipe joint min for: F min ≥K3(F Z +F f ) (6) Where: K3 is the safety factor; F Z The axial force between the inner ring of the pipe joint and the conduit at the sealing position of the pipe joint; F f The friction force generated by the radial force of the catheter.

2. The method for evaluating the connection strength of an axially extruded pipe joint according to claim 1, characterized in that: F Z The calculation formula is: Among them: K1 is a constant term; R is the diameter of the catheter; μ1 is the friction force between the groove of the inner ring of the joint and the catheter; P0 is the working pressure of the pipeline; h is the contact depth between the groove of the inner ring of the joint and the conduit; H is the groove depth of the inner ring of the joint.

3. The method for evaluating the connection strength of an axially extruded pipe joint according to claim 2, characterized in that: F f The calculation formula is: Where: L is the contact length between the groove of the inner ring of the joint and the conduit; F(x) is the contact surface pressure; μ2 is the friction force between the inner ring of the joint excluding the groove and the catheter.

4. The method for evaluating the connection strength of an axially extruded pipe joint according to claim 3, characterized in that: Minimum connection strength F of pipe joint min for:

5. A method for evaluating the connection strength of an axially extruded pipe joint according to any one of claims 1 to 4, characterized in that: The following steps are involved: Step S1: Determine the sealing position dimensions of the pipe joint and the working pressure P0 of the pipe joint according to the structure and working conditions of the pipe joint; the sealing position dimensions include the conduit diameter R, the contact depth h between the groove of the inner ring of the joint and the conduit, and the groove depth H of the inner ring of the joint; Step S2: Calculate the axial force F between the inner ring of the pipe joint and the pipe at the sealing position of the pipe joint Z for: Among them: K1 is a constant term; μ1 is the friction force between the groove of the inner ring of the joint and the catheter; Step S3: Calculate the radial force F between the inner ring of the joint and the catheter j , the contact area between the inner ring of the joint and the catheter is equivalent to a region with an equivalent elastic modulus E * The contact between the elastic cylinder and the rigid plane, with the contact center as the coordinate origin, the contact pressure F j (x) is: Where: K2 is the correction coefficient; L is the contact length between the groove of the inner ring of the joint and the catheter; x is the contact length between the groove of the inner ring of the joint and the catheter; Step S4: Calculate radial force F j The friction force F f : Where: μ2 is the friction force between the inner ring of the joint excluding the groove and the catheter; Step S5: Calculate the minimum connection strength F of the pipe joint min : Among them: K3 is the safety factor.

6. The method for evaluating the connection strength of an axially extruded pipe joint according to claim 5, characterized in that: In step S3, the equivalent elastic modulus E * The calculation formula is as follows: The contact pressure F of the contact surface is j (x) is: Where: E S is the elastic modulus of the inner ring of the joint (MPa); E c is the elastic modulus of the catheter (MPa); Vs is the Poisson’s ratio of the inner ring material of the joint; Vc is the Poisson's ratio of the catheter material.

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