WO2013071673A1

WO2013071673A1 - Method for evaluating binding strength of mechanical composite pipe

Info

Publication number: WO2013071673A1
Application number: PCT/CN2011/084533
Authority: WO
Inventors: 张燕飞; 魏帆; 郭崇晓; 王永芳; 王小艳
Original assignee: 西安向阳航天材料股份有限公司
Priority date: 2011-11-18
Filing date: 2011-12-23
Publication date: 2013-05-23
Also published as: DE112011105860T5; CN102507742B; DE112011105860B4; AU2011381327A1; AU2011381327B2; CN102507742A

Abstract

A method for evaluating the binding strength of a mechanical composite pipe comprises the following steps: selecting a standard mechanical composite pipe; imposing excitation on the standard mechanical composite pipe in specific manner, recording an excitation force signal, collecting acceleration signals in real time, and obtaining a modal parameter value of the standard mechanical composite pipe after analysis; imposing the same excitation on a mechanical composite pipe under test in the same manner, collecting acceleration signals at corresponding points in real time, and obtaining the same modal parameter value of the mechanical composite pipe under test after analysis; comparing the two modal parameter values; and determining, according to a comparison result, whether the binding strength of the mechanical composite pipe under test meet requirements, thereby solving the problems in the prior art that the destructive test needs to be performed, the test error is big, the cost is high, the efficiency is low, and the on-line test cannot be performed.

Description

An evaluation method for the combined strength of mechanical composite pipes

Technical field

The invention belongs to the technical field of mechanical property detection, and particularly relates to a method for evaluating the bonding strength of a mechanical composite pipe.

Background technique

The mechanical composite pipe utilizes the relative deformation of the liner pipe and the base pipe to make the liner pipe and the base pipe joint with each other. The metallurgical bonding interface is not formed between the liner pipe and the base pipe, and the combination of the liner pipe and the base pipe mainly depends on the base pipe and the liner pipe. The radial residual stress is maintained. Therefore, the strength of the joint directly determines the environment in which the mechanical composite pipe is used.

Current indicators for evaluating the bond strength of mechanical composite pipes are axial shear separation strength and radial clamping force. Wherein, the axial shear separation strength refers to the shear stress of the axial direction interface when the base pipe and the liner are relatively slid under the external load; the radial clamping stress refers to the composite pipe and the liner after the composite Radial residual compressive stress on the outer surface of the inner liner.

As far as the evaluation methods of the above two indicators are concerned, destructive sampling methods are adopted at home and abroad. There are two main methods of damage detection: one is the residual stress release method to measure the radial clamping force, and the other is Axial compression or axial stretching is used to measure axial shear strength. The residual stress release method is a method for calculating the circumferential residual stress of a composite pipe by measuring the change of the axial and circumferential strain of the liner before and after the composite pipe is removed. Axial stretching or compression is a method of stretching or compressing a base pipe and a liner such that it produces a maximum axial shear stress when relatively sliding.

There are three disadvantages in the above two detection methods: First, it belongs to destructive inspection, inspection cost Second, the detection method is cumbersome, the detection speed is slow, and it takes two or three days to test the strength of a composite tube by using residual stress and axial tensile or compression method; third, only in the composite tube The two ends are sampled, the detection error is large, and the test result has low reliability.

Summary of the invention

SUMMARY OF THE INVENTION The object of the present invention is to provide a method for evaluating the bonding strength of a mechanical composite pipe, which solves the problem that the prior art method requires destructive detection, and has large detection error, high cost, low efficiency, and inability to detect on-line.

The technical solution adopted by the present invention is a method for evaluating the bonding strength of a mechanical composite pipe, which comprises the following steps:

Step 1. Select a standard mechanical composite pipe whose bonding strength meets the evaluation requirements and is the same material and specification as the mechanical composite pipe to be tested;

Step 2: Apply excitation to the standard mechanical composite tube obtained in step 1 in a certain way, record the excitation force signal, collect the acceleration signal of the specific point of the standard composite mechanical tube in real time, analyze and process the obtained signal, and obtain the standard. The modal parameter value of a mechanical composite pipe;

Step 3: Apply the same excitation to the mechanical composite pipe to be tested in the same manner as in step 2, and collect the acceleration signal of the corresponding point of the mechanical composite pipe in real time, analyze and process the obtained signal, and obtain the mechanical composite pipe to be tested. The same modal parameter value;

Step 4: Comparing the modal parameter value of the mechanical composite pipe to be tested obtained in step 3 with the modal parameter value of the standard mechanical composite pipe obtained in step 2, and judging whether the bonding strength of the mechanical composite pipe to be tested is based on the comparison result qualified.

Among them, in step 1, the specific selection method of the standard mechanical composite pipe is:

Step 1.1: coaxially assembling the base pipe and the liner with the material to be tested, the outer diameter, the equal wall thickness and the equal length, and obtain the mechanical composite pipe before the standardization treatment; Step 1.2, Standardization

Step 1.2.1, initial loading

Install the sealing device at both ends of the composite pipe obtained in step 1.1, and attach the axial strain gauge and the circumferential strain gauge to the midpoint directly above the outer portion of the base pipe;

Water is injected into the inner cavity of the liner, and the water injection speed is increased by 0.01 ± 0.005Mpa per minute in the hydrostatic pressure in the liner, and the circumferential strain and axial strain of the base pipe are dynamically collected and recorded;

According to the obtained hoop strain and axial strain, the real-time hoop stress of the inner surface of the base pipe is calculated. When ^{≥ σ} « is satisfied, the water injection is stopped and the water is unloaded. According to the unloaded base pipe hoop strain and axial strain, the ring is calculated. To the residual stress ^, when the ^σ «« ^≤ ^σ ^{θ ≤ 1} · ^5σ «« is obtained, the mechanical composite pipe is standardized, wherein, the predetermined minimum hoop stress value, otherwise, the process proceeds to step 1.2.2;

Step 1.2.2, repeated loading

Filling the inner cavity of the liner again, the water injection speed is increased by the hydrostatic pressure in the liner every minute.

0.005Mpa, after one minute of water injection, the water is unloaded, and the circumferential strain and axial strain of the base pipe after collecting and unloading are calculated to obtain the circumferential residual stress ^, which is obtained when ^σ «« ^≤ ^σ ^{θ ≤ 1} · ^5σ «« is ^satisfied . Standardize the treated mechanical composite tube, otherwise repeat this step until ^σ « ^≤ ^σ ^{θ ≤ 1} · ^5σ ** is satisfied _;

Step 1.2.3,

The sealing device at both ends of the obtained standard post-treatment mechanical composite pipe was disassembled to obtain a standard mechanical composite pipe.

Further, the natural frequency modal parameters ", as the specific method step 2: the length obtained in step 1 are standard mechanical composite pipe ¹ is horizontally placed on two V-shaped grooves, the adjustment of the two V-grooves Positioning such that the outer end faces of the two V-groove support portions are vertically aligned with the two outer end faces of the composite pipe; An acceleration sensor is disposed at a midpoint position directly above the outside of the base pipe, and an excitation device is applied to the base pipe by the excitation device, and the horizontal distance between the application position and the acceleration sensor is within a range of 〃 10 to the acceleration sensor and the excitation The vibration applying device is connected to the computer through the dynamic signal collecting instrument, and the computer analyzes the frequency response of the real-time acceleration signal and the exciting force signal collected by the dynamic signal collecting instrument, and obtains the inherent condition of the mechanical composite pipe of the standard component through the modal parameter identification. Frequency ^^; In step 3, take the same method as step 2 to obtain the natural frequency of the mechanical composite pipe to be tested 3⁄4

In step 4, the natural frequency _iM of the mechanical composite pipe to be tested obtained in step 3 is compared with the natural frequency of the standard mechanical composite pipe obtained in step 2. When the ^^ ^ ^^, the mechanical composite pipe to be tested is combined. The strength is qualified. Otherwise, it is considered that the combined strength of the mechanical composite pipe to be tested is unqualified.

Further, the modal parameter is damping, and the specific method of step 2 is: placing the standard mechanical composite pipe of the length obtained in step 1 horizontally on two V-shaped grooves, adjusting the positions of the two V-shaped grooves, so that The outer end faces of the two V-groove support portions are vertically aligned with the two outer end faces of the composite pipe; an acceleration sensor is disposed at a midpoint position directly above the outer portion of the base pipe, and an excitation device is applied to the base pipe to excite the vibration The horizontal distance between the application position and the acceleration sensor is in the range of 〃10 to 、, and the acceleration sensor and the excitation application device are connected to the computer through the dynamic signal acquisition device, and the real-time acceleration signal and the vibration acquired by the computer are collected by the dynamic signal acquisition device. The vibration signal is subjected to frequency response analysis, and the damping of the standard mechanical composite pipe is obtained by modal parameter identification;

In step 3, the same method as step 2 is adopted, and finally the resistance of the mechanical composite pipe to be tested is obtained.

In step 4, the damping of the mechanical composite pipe to be tested obtained in step 3 is compared with the damping of the standard mechanical composite pipe obtained in step 2. When ^^^, the combined strength of the mechanical composite pipe to be tested is qualified, otherwise, it is considered The mechanical composite pipe joint strength was not tested. Further, the modal parameters of transmissibility; 7 specific method, step 2 as follows: Step 1 The length of a standard mechanically obtained composite tube ¹ is horizontally placed on two V-shaped grooves, the adjustment of the two V-grooves a position such that the outer end faces of the two V-shaped groove supports are vertically aligned with the two outer end faces of the composite pipe;

An acceleration sensor is disposed at a point A of the nozzle directly above the inside of the liner, and an acceleration sensor No. 2 is disposed at a midpoint position B directly above the outside of the base pipe, and an excitation device is applied to the base pipe by the excitation device, and two Both the acceleration sensor and the excitation application device are connected to the computer through a dynamic signal acquisition device, and the computer processes and analyzes the obtained signal to obtain a time domain signal of point A and a time domain signal of point B, which are respectively obtained by Fourier transform. ^ and will be divided by ^β ^, the transfer rate of the acceleration of the defect relative to the acceleration of point B is _3⁄4?s , 0 < _3⁄43⁄4 <1;

In step 3, the same method as step 2 is adopted to obtain the transfer rate of the mechanical composite pipe to be tested.

3⁄4 test;

In step 4, the transmissibility of mechanical test composite pipe obtained in step 3 _¾ transmissibility standard mechanical composite pipe 2 obtained in step _i _{¾? S} contrast, when the «≥¾, mechanical composite pipe binding test The strength is qualified. Otherwise, it is considered that the combined strength of the mechanical composite pipe to be tested is unqualified.

The beneficial effects of the method of the invention are:

1. By applying excitation to the selected standard mechanical composite pipe and the mechanical composite pipe to be tested, obtaining modal parameters, and comparing the modal parameters, to determine whether the combined strength of the mechanical composite pipe to be tested is evaluated. The composite standard, which does not require damage to the pipeline, reduces inspection costs.

2. The method for selecting the standard mechanical composite tube of the method of the invention is simple, scientific and reasonable, and has been proved by a large number of experiments that the detection error as the evaluation standard is small and the result is reliable.

3. The method of the invention is simple and easy, and the detection efficiency is high. It takes less than one minute to test a composite tube, so that online real-time detection of the combined strength of the composite tube can be realized; It can reduce the detection error and has the advantage of high detection accuracy compared with the existing residual stress and axial stretching or compression method.

DRAWINGS

Figure 1 is a schematic view showing the structure of a mechanical composite pipe in the method of the present invention;

2 is a schematic diagram of a two-degree-of-freedom vibration model of transverse vibration of a mechanical composite pipe in the method of the present invention; and FIG. 3 is a schematic view of vibration testing of a mechanical composite pipe in the method of the present invention.

Detailed ways

The invention will be described in detail below with reference to the drawings and specific embodiments.

As shown in Fig. 1, the mechanical composite pipe 1 is composed of a base pipe 2 and a liner 3 located in the base pipe 2. Example 1

The method for evaluating the bonding strength of a mechanical composite pipe includes the following steps:

Step 1. Select the standard composite mechanical pipe with the same material and specification as the mechanical composite pipe to be tested, that is, the selected standard mechanical composite pipe and the composite pipe to be tested, etc. , such as wall thickness and equal length.

The specific selection method of the standard mechanical composite pipe is:

Step 1.1: Coaxial assembly with the material of the composite pipe to be tested, the outer diameter, the equal wall thickness and the length of the base pipe and the liner, and obtain the mechanical composite pipe before the standardization treatment;

Step 1.2, Standardization

Step 1.2.1, initial loading

Water is injected into the inner cavity of the liner to cause elastic deformation of the liner, and the base pipe is elastically deformed. The water injection speed is increased by 0.01 ± 0.005 MPa per minute in the hydrostatic pressure in the liner, and is collected every minute. Record the circumferential strain and axial strain of the base pipe;

According to the formula + f (ε _{θ +} ε _ζ ) , where ^ is the inner diameter of the base pipe, r ₃ is the outer diameter of the base pipe, E is the elastic modulus of the base pipe, and V is the Poisson's ratio of the base pipe, and the base is obtained. The real-time circumferential stress σ _{θ of the} inner surface of the pipe stops water injection and unloads water when ^≥ σ « is satisfied, which is based on the circumferential strain of the base pipe after unloading

^ and axial strain ^ calculated to obtain the circumferential residual stress ^σ , when the ^σ «« ^≤ ^σ ^{θ ≤ 1} · ^5σ « « is obtained after the standardized treatment of the mechanical composite pipe, which, "for the combination given by the customer or the standard The hoop stress index calculated from the strength index, otherwise, proceed to step 1.2.2;

Step 1.2.2, repeated loading

Step 1.2.3,

Step 2: Apply excitation to the standard mechanical composite tube obtained in step 1 in a certain way, record the excitation force signal, collect the acceleration signal of the specific point of the standard composite mechanical tube in real time, analyze and process the obtained signal, and obtain the standard. The natural frequency of a mechanical composite pipe ^^.

The specific method of step 2 is:

As shown in FIG. 3, the standard mechanical composite pipe of length ^ obtained in step 1 is horizontally placed on the two V-shaped grooves 2, and the positions of the two V-shaped grooves 2 are adjusted to support the two V-shaped grooves 2 The outer end face of the portion is vertically aligned with the two outer end faces of the composite pipe. The acceleration sensor 4 is disposed at a midpoint position directly above the outside of the base pipe, and the sensitivity of the acceleration sensor 4 is generally required to be 100 mv/g or more. Excitation is applied to the base pipe by the excitation device 3, and the horizontal distance between the excitation application position and the acceleration sensor 4 is within a range of 〃ιο, and the acceleration sensor and the excitation device are both passed through a dynamic signal acquisition device (DHDAS5920) and a computer. The modal analysis software (DHMA) is used to analyze the frequency response of the real-time acceleration signal and the excitation force signal collected by the dynamic signal acquisition device, and the natural frequency of the mechanical composite pipe of the standard component is obtained by modal parameter identification _3⁄43⁄4 .

The selection criteria of the agitating device are: the rubber hammer is used when the estimated natural frequency value is less than or equal to 200 Hz; the nylon hammer is used when the estimated natural frequency value is 200 Hz to 500 Hz; the metal hammer is used for estimating the natural frequency value greater than 500 Hz.

Step 3: Apply the same excitation to the mechanical composite pipe to be tested in the same manner as in step 2, and collect the acceleration signal of the corresponding point of the mechanical composite pipe in real time, analyze and process the obtained signal, and obtain the mechanical composite pipe to be tested. The natural frequency of _iM .

The specific method of step 3 is:

The length of the mechanical composite pipe to be tested is horizontally placed on the same two V-shaped grooves as in step 2, and the positions of the two V-shaped grooves are adjusted so that the outer end faces of the two V-shaped groove supporting portions and the composite pipe are both The outer end faces are vertically aligned;

An acceleration sensor is disposed at a midpoint position directly above the base pipe of the mechanical composite pipe to be tested, and the sensitivity of the acceleration sensor is generally required to be greater than or equal to 100 mv/g. Excitation is applied to the base pipe by the excitation device. The excitation device and the excitation application position, size and mode are the same as in step 2. The acceleration acquisition position is the same as that in step 2. The acceleration sensor and the excitation device pass the dynamic signal acquisition device. Connected with the computer, the computer performs frequency response analysis on the real-time acceleration signal and the excitation force signal collected by the dynamic signal acquisition instrument, and obtains the natural frequency of the mechanical composite pipe to be tested through modal parameter identification. Step 4: Comparing the natural frequency _iM of the mechanical composite pipe to be tested obtained in the step 3 with the natural frequency of the standard mechanical composite pipe obtained in the step 2, when the ^^ ^ ^^, the mechanical composite pipe joint strength to be tested Qualified, otherwise, the combined strength of the mechanical composite pipe to be tested is considered unqualified.

Example 2

In this embodiment, the modal parameter for detecting and evaluating the joint strength of the composite pipe is damping. In step 2, after the frequency response analysis of the acceleration signal and the force signal, the damping of the standard mechanical composite tube is obtained. In step 3, after the frequency response analysis of the acceleration signal and the force signal of the mechanical composite pipe to be tested, the damping of the mechanical composite pipe to be tested is obtained, and the other steps of steps 1 to 3 are the same as in the first embodiment.

In step 4, the damping of the mechanical composite pipe to be tested obtained in step 3 is compared with the damping of the standard mechanical composite pipe obtained in step 2. When ^^^, the combined strength of the mechanical composite pipe to be tested is qualified, otherwise, it is considered The mechanical composite pipe joint strength was not tested.

1. The relationship between the bonding strength of the mechanical composite pipe and the normal stiffness of the combined interface:

According to the rough surface normal contact stiffness fractal model, assuming that the contact surface is isotropic, and the interaction between the microprotrusions on the rough surface is negligible, the dimensionless normal stiffness of the mechanical bond interface can be expressed as r„ = ^{2 (2} - Factory ^ W „

When the contact surface undergoes elastoplastic deformation, the relationship between the normal load and the contact area between the two cylinders is: I ~ 9 _

P = -^G'^g, (D)A^[(^-)~ A ~—": D] + g ₂ CD)4 : D, _{D ≠ 1 5} .

P = ;

Where is a dimensionless normal force, G' is a dimensionless fractal roughness parameter, a coefficient related to the hardness and yield strength of the material, & and is a function of the fractal dimension D,

By combining the relationship between the dimensionless contact stiffness and the dimensionless normal force, the stiffness of the mechanical bond interface increases with the increase of the normal load.

Since the mechanical composite pipe is mechanically bonded by the elastoplastic deformation of the base pipe and the liner by underwater deflagration technology, its bonding strength is related to the radial residual compressive stress at the interface between the base pipe and the liner, that is, The greater the radial residual compressive stress, the higher the joint strength of the composite pipe, and the radial compressive stress of the composite pipe can be expressed as: = p , where p is the normal force on the joint surface of the composite pipe and A is the true contact area of the composite pipe.

In summary, the higher the bonding strength, the larger the normal load of the bonding interface, and the larger the normal load of the bonding interface, the greater the normal stiffness of the bonding interface. Therefore, the higher the bonding strength, the greater the normal stiffness of the bonding interface.

2. The relationship between the normal stiffness of the interface and the natural frequency of the composite pipe:

Because the interface between the mechanical composite pipe base pipe and the liner is relatively complicated, it is difficult to theoretically analyze the influence of the joint interface of the base pipe and the liner on the dynamic characteristics of the composite pipe by using the vibration model of the infinitely free beam. In order to reduce the difficulty of analysis, the lateral vibration of the simply supported branches at both ends of the composite pipe is simplified to a vibration model of two degrees of freedom. As shown in Figure 2, which represents the mass of the base pipe; m ₂ represents the quality of the liner; represents the bending stiffness of the composite pipe; represents the interface stiffness between the base pipe and the liner; c represents the interface damping between the base pipe and the liner , "The natural frequency of the model system. The stiffness and damping of the interface between the base pipe and the liner are simulated by spring stiffness and damping elements, respectively: Motion differential equation:

(k _x + k ₂ ) m ₂ + m^ ₂ [(^ + k ₂ )m ₂ + m^ ₂ ] ² 4m ₁ m ₂ fc ₁ fc ω

For the guidance, you can get:

0

For the same reason, take " ^: for derivation:

>0

Dk ₂ π πι k _x + k ₂ )m ₂ + m^k. In summary, it can be seen that w ^{2 /} ^ ^{2 is always} greater than zero, and the conclusion is obtained as the ^ increases. Since ^ represents the normal stiffness of the joint interface between the base pipe and the liner, it is concluded that the composite pipe having a larger normal stiffness is combined with the higher natural frequency.

3. The relationship between mechanical composite pipe joint strength and natural frequency and damping:

The conclusion of the relationship between the bond strength and the normal stiffness of the bonded interface (the higher the bond strength, the combination The greater the normal stiffness of the interface and the analysis of the relationship between the normal stiffness and the natural frequency of the interface (the greater the normal stiffness of the interface, the higher the natural frequency), the higher the natural frequency of the mechanical composite pipe is. in conclusion.

At the same time, as shown in the following table, the natural frequency and damping of a plurality of mechanical composite pipes are obtained by the method of the present invention, and the joint strength is obtained by using the existing shear separation failure test method, and the higher the combined strength of the composite pipe, the greater the natural frequency. The conclusion that the damping is smaller is also verified; the accuracy of the method for evaluating the bonding strength of the mechanical composite pipe is also verified. In the 76x (6+2) mechanical composite pipe, the outer diameter of the mechanical composite pipe is 76 mm, the wall thickness of the base pipe is 6 mm, and the wall thickness of the liner is 2 mm; the specification is 219x ( 14.3+3) mechanical composite In the tube, the outer diameter of the mechanical composite pipe is 219 mm, the wall thickness of the base pipe is 14.3 mm, and the wall thickness of the liner is 3 mm.

Example 3

In the present embodiment, the step method of detecting the evaluation of the joint strength of the composite tube as the transfer rate step 1 is the same as that of the first embodiment.

Step 2: Apply excitation to the standard mechanical composite tube obtained in step 1 in a certain way, record the excitation force signal, collect the acceleration signal of the specific point of the standard composite mechanical tube in real time, analyze and process the obtained signal, and obtain the standard. The transfer rate of a mechanical composite pipe.

The specific method of step 2 is: the standard part mechanical composite pipe water of length ^ obtained in step 1 The two V-grooves are placed flat, and the positions of the two V-grooves are adjusted such that the outer end faces of the two V-groove support portions are vertically aligned with the two outer end faces of the composite pipe.

An acceleration sensor is arranged at the position A of the nozzle directly above the inside of the liner, and the distance a between the position of the point A and the nozzle a satisfies 0 a 50 mm; the second acceleration sensor is disposed at the midpoint of the point B directly above the outside of the base pipe; The excitation device applies excitation on the base pipe, and the excitation application position is located on the right side of the position B, and is 100 mm to 500 mm from the point B; the two acceleration sensors and the excitation application device are both connected to the computer through the dynamic signal acquisition device. Connected, the computer will process and analyze the acquired signal to obtain the time domain signal of point A) and the time domain signal of point B (), after the Fourier transform, respectively, and ^), which will be divided by ^β ^, ^{传递 The} acceleration of the point acceleration relative to the acceleration at point B, ^{Q ≤ ≤1} _;

In step 3, the same method as step 2 is adopted, the same excitation is applied to the mechanical composite pipe to be tested, and the acceleration signal of the corresponding point of the mechanical composite pipe is collected in real time, and the obtained signal is analyzed and processed to obtain the mechanical composite to be tested. The transfer rate of the tube ^«, ^Q≤ " ^≤1 .

In step 4, the transmissibility of mechanical test composite pipe obtained in step 3 ^ ⁷ transmissibility standard mechanical composite pipe «obtained in Step 2 are compared, when ^≥, mechanical composite pipe bonding strength test qualified, or It is considered that the combined strength of the mechanical composite pipe to be tested is unqualified.

In the method of the present invention, the transfer rate; 7 can also be used as a modal parameter for detecting and evaluating the bonding strength of the composite tube. The transfer rate and bonding strength of a plurality of mechanical composite pipes are respectively obtained by the method of the present invention and the existing shear separation failure test method. From the table below, it can be seen that the transfer strength is high when the bond strength is high, and the accuracy of the method for evaluating the bond strength of the mechanical composite pipe is also verified. In the mechanical composite pipe of the specification 89x (5+2), the outer diameter of the mechanical composite pipe is 89 mm, the wall thickness of the base pipe is 5 mm, and the wall thickness of the liner is 2 mm.

Zvo 8S.0 ε.9ΐ.ο/ειοζ OAV

Claims

Claim

A method for evaluating the bonding strength of a mechanical composite pipe, comprising the following steps: Step 1. Selecting a standard mechanical composite pipe having the same bonding strength as the evaluation requirement and having the same material and specification as the mechanical composite pipe to be tested;

The method for evaluating the joint strength of a mechanical composite pipe according to claim 1, wherein in the step 1, the specific selection method of the standard mechanical composite pipe is:

Step 1.1: Coaxially assemble the base pipe and the liner with the material such as the composite pipe 9 to be tested, the outer diameter, the equal wall thickness and the equal length, and obtain the mechanical composite pipe before the standardization treatment;

Step 1.2, Standardization

Step 1.2.1, initial loading

Filling the inner cavity of the liner, the water injection speed is increased by 0.01 0.01 per minute in the hydrostatic pressure in the liner

0.005Mpa, dynamically collect and record the circumferential strain and axial strain of the base pipe;

According to the obtained hoop strain and axial strain, the real-time hoop stress of the inner surface of the base pipe is calculated. When ^{≥ σ} « is satisfied, the water injection is stopped and the water is unloaded. According to the unloaded base pipe hoop strain and axial strain, the ring is calculated. To the residual stress ^, when the ^σ «« ^≤ ^σ ^{θ ≤ 1} · ^5σ «« is obtained, the mechanical composite pipe is standardized, wherein "the hoop stress calculated by the bond strength index given by the customer or the standard" Indicator, otherwise, go to step 1.2.2;

Step 1.2.2, repeated loading

Step 1.2.3,

The method for evaluating the joint strength of a mechanical composite pipe according to claim 1 or 2, wherein the modal parameter is a natural frequency,

The specific method of step 2 is: placing the standard mechanical composite pipe of length ^ obtained in step 1 horizontally on two V-shaped grooves, adjusting the positions of the two V-shaped grooves, and making the two V-shaped groove supporting portions The outer end surface is vertically aligned with the two outer end faces of the composite pipe;

An acceleration sensor is disposed at a midpoint position directly above the outside of the base pipe, and an excitation device is applied to the base pipe by the excitation device, and the horizontal distance between the application position and the acceleration sensor is within a range of 〃10 to ⁷ " ιο, and the acceleration is accelerated. The sensor and the excitation application device are connected to the computer through a dynamic signal acquisition device, and the computer performs the real-time acceleration signal and the excitation force signal collected by the dynamic signal acquisition device. Frequency response analysis, the natural frequency of the standard mechanical composite pipe is obtained by modal parameter identification; in step 3, the same method as step 2 is adopted to obtain the natural frequency of the mechanical composite pipe to be tested 3⁄4

The method for evaluating the joint strength of a mechanical composite pipe according to claim 1 or 2, wherein the modal parameter is damping

An acceleration sensor is disposed at a midpoint position directly above the outside of the base pipe, and an excitation device is applied to the base pipe by the excitation device, and the horizontal distance between the application position and the acceleration sensor is within a range of 〃10 to ⁷ " ιο, and the acceleration is accelerated. The sensor and the excitation applying device are connected to the computer through the dynamic signal collecting instrument. The computer analyzes the frequency response of the real-time acceleration signal and the exciting force signal collected by the dynamic signal collecting instrument, and obtains the mechanical composite of the standard component through the modal parameter identification. Damping of the tube;

In step 4, the damping of the mechanical composite pipe to be tested obtained in step 3 is compared with the damping of the standard mechanical composite pipe obtained in step 2. When ^^^, the mechanical composite pipe to be tested is combined. The specific method of step 2 is: placing the standard mechanical composite pipe of length ^ obtained in step 1 horizontally on two V-shaped grooves, adjusting the positions of the two V-shaped grooves, and making the two V-shaped groove supporting portions The outer end surface is vertically aligned with the two outer end faces of the composite pipe;

3⁄4 test;