A determination method for the failure of a pressurized pipeline penetration

Abstract

The present invention discloses a method for determining the failure of a pressurized pipeline penetration, which includes the following steps: S1. Obtain the initial parameters of the penetrator, including the initial velocity v and mass m; S2. Calculate the critical penetration velocity of the pressurized pipeline according to the initial parameters of the penetrator and the parameters of the pressurized pipeline; S3. Compare the initial velocity v of the penetrator with the critical penetration velocity of the pressurized pipeline calculated in step S2. If <, the penetrator will not penetrate the pipeline; if >, the penetrator will penetrate the pipeline. The present invention can more simply calculate the critical penetration velocity of the pressurized pipeline through basic data, and establish a determination basis for the failure of the pressurized pipeline penetration based on the critical penetration velocity, so as to more effectively determine the failure of the pressurized pipeline penetration. The method for determining the failure of the pressurized pipeline penetration has high universality, thus providing a more effective determination method for preventing penetrator penetration in the field of pressurized pipelines.

Description

Technical Field

[0001] The embodiments of the present invention belong to the field of protection of pressure pipelines, and particularly relate to a method for determining the failure of a pressure pipeline penetration. Background Art

[0002] Accidents of pressure pipeline penetration often cause the bursting of pressure pipelines, damage to units and valves, and even cause casualties. Therefore, analyzing whether the penetrator in the pressure pipeline will penetrate the pipeline to avoid or reduce the losses caused by pipeline penetration is of great significance for ensuring the safety and stability of the normal transportation of pressure pipelines. The impact limits, including the rupture limit and the penetration limit, are specific impact terms describing the critical thresholds for the transition of failure modes, and they represent the resistance of the target structure to external impacts. The penetration limit represents the critical velocity therein and the velocity at which the penetrator initially penetrates the pipe wall. The impact limit can provide a clear picture and reveal the triggering conditions for the failure modes of pressurized pipe fittings.

[0003] At present, the research on the prediction and evaluation of pressure pipeline penetration mainly focuses on judging whether the pressure pipeline penetrates through impact tests. However, there are still the following deficiencies in analyzing the penetration failure of pressure pipelines through impact experiments: (1) The result analysis of the impact experiment cannot directly obtain the judgment basis for the non-penetration of the pressure pipeline at a certain velocity of the penetrator. (2) There are many uncontrollable factors in the experimental process, and it is necessary to analyze a large number of variables, which requires a lot of time and energy and is not efficient enough. (3) The results after experimental analysis can only show the judgment of the penetration failure of the pressure pipeline under specific conditions, and cannot directly obtain the critical penetration velocity of the pipeline required under different pipeline internal pressures. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for determining the failure of a pressure pipeline penetration, to overcome the deficiencies in the prior art, to provide a calculation formula for more quickly, conveniently, and efficiently calculating the critical penetration velocity of a pressure pipeline using basic physical parameters, and to construct a judgment basis for the failure of a pressure pipeline penetration so as to more efficiently judge the penetration failure of a pressure pipeline.

[0005] A method for determining the failure of a pressure pipeline penetration includes the following steps:

[0006] S1. Obtain the initial parameters of the penetrator, including the initial velocity v and the mass m;

[0007] S2. Calculate the critical penetration velocity v of the pressure pipeline according to the initial parameters of the penetrator and the parameters of the pressure pipeline pl ;

[0008] S3. Compare the initial velocity v of the penetrator with the critical penetration velocity v of the pressure pipeline calculated in step S2 pl , if v < vpl , the penetrator will not penetrate the pipeline; if v > v pl , the penetrator will penetrate the pipeline.

[0009] Furthermore, it further includes step S4: constructing a penetration failure determination curve with the critical penetration velocity v of the pressurized pipeline as the y-axis and the internal pressure p of the pipeline as the x-axis. If the initial velocity v of the penetrator is above the penetration failure determination curve, the penetrator will penetrate the pipeline; if the initial velocity v of the penetrator is below the penetration failure determination curve, the penetrator will not penetrate the pipeline. pl

[0010] Furthermore, in step S2, the calculation formula for the critical penetration velocity v of the pressurized pipeline is as follows: pl

[0011]

[0012] where v pl is the critical penetration velocity of the pressurized pipeline (m / s), k is the petal splitting coefficient, defined as θ1 is the initial flipping angle, which is the flipping angle of the failed part of the pipe wall relative to its initial position at the beginning of the petal splitting stage, θ2 is the final flipping angle, which is the flipping angle of the failed part of the pipe wall relative to its initial position at the end of the petal splitting stage, m is the mass of the penetrator (kg), t is the wall thickness of the pipeline (m), a is the petal length of the petal triangle formed in the petal splitting stage (m), l is the perpendicular bisector length of the petal triangle formed in the petal splitting stage (m), ρ is the density of the pipeline material (kg / m 3 ), p is the internal pressure of the pipeline (MPa), n is the number of cracks formed in the petal splitting stage of the pipeline, and Y is the yield strength (MPa).

[0013] Furthermore, the calculation of the critical penetration velocity v of the pressurized pipeline in step S2 pl specifically includes the following steps:

[0014] S21. Calculate the velocity v1 of the penetrator, the total bending moment M of the cantilever petal, and the energy change ΔW before and after the flipping stage p : R :

[0015] The algebraic expression for the velocity v1 of the penetrator at the end of the petal splitting stage is obtained from the moment balance equation in the petal splitting stage:

[0016]

[0017] where v1 is the velocity of the penetrator at the end of the petal splitting stage (m / s), k is the petal splitting coefficient, defined as v0 is the initial velocity of the penetrator (m / s);

[0018] The total bending moment M of the cantilever flap p is calculated as follows:

[0019]

[0020] where M p is the total bending moment of the cantilever flap (N*m), Y is the yield strength (MPa), t is the wall thickness of the pipe (m), p is the internal pressure of the pipe (MPa), ol is the length of the perpendicular bisector of the petal triangle formed in the petal splitting stage (m), B is the base width of a single petal (m), and x is the moving distance of the plastic hinge formed in the petal splitting stage (m);

[0021] The energy ΔW changed before and after the flipping stage R is calculated as follows:

[0022]

[0023] where ΔW R is the energy changed before and after the flipping stage (MJ), m is the mass of the penetrator (kg), n is the number of cracks formed in the petal splitting stage of the pipe, ρ is the density of the pipe material (kg / m 3 ), a is the petal length of the petal triangle formed in the petal splitting stage (m), and v r is the residual velocity of the penetrator;

[0024] S22. Substitute the penetrator velocity v1 at the end of the petal splitting stage, the total bending moment M of the cantilever flap p , and the energy ΔW changed before and after the rotation stage R into the energy balance equation in the flipping stage:

[0025]

[0026] S23. Since the residual velocity v r is 0 m / s, after simplifying the above balance equation, the critical penetration velocity v of the pressurized pipe pl is obtained, and the calculation formula

[0027]

[0028] where v pl is the critical penetration velocity of the pressurized pipe (m / s), and k is the petal splitting coefficient, defined as θ1 is the initial flipping angle, which is the flipping angle of the failed part of the pipe wall relative to its initial position at the start of the petal splitting stage. θ2 is the final flipping angle, which is the flipping angle of the failed part of the pipe wall relative to its initial position at the end of the petal splitting stage. m is the mass of the penetrator (kg), t is the wall thickness of the pipe (m), a is the petal length (m) of the petal triangle formed in the petal splitting stage, l is the length of the perpendicular bisector of the petal triangle formed in the petal splitting stage, ρ is the density of the pipe material (kg / m 3 ), p is the internal pressure of the pipe (MPa), n is the number of cracks formed in the petal splitting stage of the pipe, and Y is the yield strength (MPa).

[0029] Furthermore, the diameter-to-thickness ratio of the pressurized pipe is greater than or equal to 42.

[0030] The beneficial effects of the present invention are as follows:

[0031] (1) The present invention provides a method for calculating the critical penetration failure of a pressurized pipe using only basic parameters of the pressurized pipe and the penetrator. Only by constructing the critical penetration speed of the pressurized pipe can the judgment basis for the penetration failure of the pressurized pipe be obtained, avoiding the deficiencies of the traditional impact test being not intuitive and efficient enough, and enabling a faster and more efficient judgment of the penetration failure of the pressurized pipe.

[0032] (2) By calculating the critical penetration speed of the pressurized pipe under different internal pressures of the pipe, a relationship diagram between the internal pressure of the pipe and the critical penetration speed of the pipe is constructed, thus providing a more intuitive judgment basis for determining whether the pressurized pipe penetrates and fails at the initial speed of the penetrator under different internal pressures of the pipe. Description of the Drawings

[0033] Figure 1 is a schematic flow diagram of the present invention.

[0034] Figure 2 is a schematic diagram of the principle of the petal splitting stage formula provided by the present invention.

[0035] Figure 3 is a schematic diagram of the (a) structure and (b) mechanical analysis of the petal formed in the petal splitting stage provided by the present invention.

[0036] Figure 4 is a schematic diagram of the penetration failure judgment curve of the pressurized pipe constructed by the present invention. Detailed Embodiments

[0037] Now, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be understood that the embodiments shown and described in the drawings are merely exemplary, intended to illustrate the principles and processes of the present invention, and not to limit the scope of the present invention.

[0038] The present invention is used to determine whether a pressurized pipeline will undergo through - penetration failure when impacted by a penetrator. When the pipeline is being penetrated, petalling will occur. Petalling refers to a failure mode in which the cracks in the pipeline wall spread like "petals". During this stage, the pipeline wall will undergo crack propagation in the form of "petal unfolding". The petals generated during the petal formation stage can be regarded as cantilever beams rotating around the root of the plastic hinge, and the triangular petal part rotates around the root of the plastic hinge. At the beginning of this stage, the flipped angle of the failed part of the pipeline wall relative to its initial position is the initial flip angle θ1, and at the end of this stage, the flipped angle of the failed part of the pipeline wall relative to its initial position is the final flip angle θ2.

[0039] The present invention provides a method for determining the through - penetration failure of a pressurized pipeline, as Figure 1 shown, including the following steps S1 - S3:

[0040] S1. Respectively obtain the outer diameter D, wall thickness t, yield strength Y, density ρ of the pressurized pipeline, and the internal pressure p of the designed pressurized pipeline, as well as the initial parameters of the penetrator, including the initial velocity v and mass m of the penetrator;

[0041] S2. Use the law of conservation of energy and the moment balance equation during the impact process to derive a calculation formula to calculate the thin - walled pressurized pipeline. Calculate the critical penetration velocity v of the pressurized pipeline according to the initial parameters of the penetrator and the parameters of the pressurized pipeline pl , preferably, it is more applicable when the diameter - to - thickness ratio, that is, the ratio of the diameter to the pipeline wall thickness, is ≥ 42. Specifically, step S2 further includes the following sub - steps:

[0042] S21. Respectively calculate the velocity v1 of the penetrator at the end of the petalling stage, the total bending moment M of the cantilever petal p , the energy change ΔW before and after the flipping stage R .

[0043] To evaluate the penetration limit and the remaining velocity of the penetrator during petalling failure, a simplified analytical model process is established based on the energy balance during the impact. That is, the petals generated during the petal formation stage can be regarded as cantilever beams rotating around the root of the plastic hinge, and the triangular petal part rotates around the root of the plastic hinge. At the beginning of the petalling stage, the flipped angle of the failed part of the pipeline wall relative to its initial position is the initial flip angle, and at the end of the petalling stage, the flipped angle of the failed part of the pipeline wall relative to its initial position is the final flip angle, as Figure 2 shown: θ1 is the initial flip angle, θ2 is the final flip angle, a is the petal length of the petal triangle formed during the petalling stage, t is the petal thickness, that is, the wall thickness of the pipeline, v0 is the initial velocity of the penetrator, v1 is the remaining velocity of the penetrator after penetration, where v r is the residual velocity of the penetrator after penetrating the pipeline, v n and vt They are the normal and tangential component velocities respectively.

[0044] According to engineering experience, for every 1 Mpa increase in internal pressure, θ1 will decrease by 5°. θ2 is generally approximately equal to π / 4. In engineering practice (radius r = D / 2)

[0045] The algebraic expression for the penetrator velocity v1 at the end of the stage is obtained from the moment balance equation in the petal splitting stage:

[0046]

[0047] where k is the petal splitting coefficient, defined as where v0 is the initial velocity of the penetrator, ρ is the density of the pipeline material (kg / m 3 ), a is the petal length (m) of the petal triangle formed in the petal splitting stage, and t is the wall thickness of the pipeline (m).

[0048] Such as Figure 3 (a) The structure of the petal and (b) the mechanical analysis diagram, x is the moving distance of the plastic hinge from the tip after a period of time, B is the base width of a single petal, a is the petal length, and l is the length of the perpendicular bisector of the petal triangle formed.

[0049] It can be seen from the above figure that the algebraic expressions for calculating the petal length a and the perpendicular bisector l using the isosceles triangle formula

[0050]

[0051] It can be seen from the above figure that the total bending moment M of the cantilever petal p = M1 - M2, and the calculation formula is:

[0052]

[0053] where M p is the total bending moment of the cantilever petal (N*m), Y is the yield strength (MPa), t is the wall thickness of the pipeline (m), p is the internal pressure of the pipeline (MPa), l is the length of the perpendicular bisector of the petal triangle formed in the petal splitting stage (m), B is the base width of a single petal (m), and x is the moving distance of the plastic hinge formed in the petal splitting stage (m).

[0054] The energy change ΔW before and after the flipping stage R The calculation formula is:

[0055]

[0056] where ΔW RΔW is the energy (MJ) before and after the flipping stage, m is the mass of the penetrator (kg), n is the number of cracks formed during the pipe petal splitting stage, ρ is the density of the pipe material (kg / m 3 ), a is the petal length (m) of the petal triangle formed during the petal splitting stage, v r is the residual velocity of the penetrator.

[0057] S22. Substitute the penetrator velocity v1 at the end of the petal splitting stage, the total bending moment M p of the cantilever petal, and the energy change ΔW R before and after the rotation stage into the energy balance equation in the flipping stage:

[0058]

[0059] S23. Since the residual velocity V r is 0, after simplifying the above balance equation, the critical penetration velocity v pl of the pressurized pipe is obtained. (In general engineering practice, the diameter-thickness ratio of the pressurized pipe is greater than 40, and the fitting accuracy of this formula is more accurate when the diameter-thickness ratio is greater than or equal to 42)

[0060]

[0061] where v pl is the critical penetration velocity (m / s) of the pressurized pipe, k is the petal splitting coefficient, defined as θ1 is the initial flipping angle, which is the flipping angle of the failed part of the pipe wall relative to its initial position at the start of the petal splitting stage, θ2 is the final flipping angle, which is the flipping angle of the failed part of the pipe wall relative to its initial position at the end of the petal splitting stage, m is the mass of the penetrator (kg), t is the wall thickness of the pipe (m), a is the petal length (m) of the petal triangle formed during the petal splitting stage, l is the length of the perpendicular bisector of the petal triangle formed during the petal splitting stage, ρ is the density of the pipe material (kg / m 3 ), p is the internal pressure of the pipe (MPa), n is the number of cracks formed during the pipe petal splitting stage, and Y is the yield strength (MPa).

[0062] Note: The petal splitting coefficient k is defined as

[0063]

[0064] where m is the mass of the penetrator and n is the number of cracks. According to engineering experience, the number of cracks n is generally equal to 4.

[0065] S3. Compare the initial velocity v of the penetrator with the critical penetration velocity v pl of the pressurized pipe calculated in step S2. pl , if v < v pl , the penetrator will not penetrate the pipe; if v > vpl , the penetrator will penetrate through the pipeline.

[0066] Furthermore, it may further include step S4: constructing a penetration failure determination curve with the critical penetration speed v of the pressurized pipeline pl as the y-axis and the internal pressure p of the pipeline as the x-axis. If the initial speed v of the penetrator is above the penetration failure determination curve, the penetrator will penetrate through the pipeline; if the initial speed v of the penetrator is below the penetration failure determination curve, the penetrator will not penetrate through the pipeline.

[0067] Example: A pressurized pipeline is impacted by a penetrator, and the initial parameters are shown in Table 1 below.

[0068] Table 1 Basic parameters of the penetrator and the pressurized pipeline

[0069]

[0070] Since the pipeline diameter-thickness ratio is 83 > 46, when the internal pressure of the pressurized pipeline is 2 Mpa, substituting the data into the penetration critical speed calculation formula, the critical penetration speed of the pipeline can be obtained as 155 m / s. According to the determination basis of the pressurized pipeline penetration failure, it is as shown in Table 2 below.

[0071] Table 2 Determination basis for the penetration failure of the pressurized pipeline when the internal pressure is 2 Mpa

[0072]

[0073] Through the above judgment method, it is possible to simply and accurately judge whether a penetrator can penetrate a pressurized pipeline at different speeds under the current conditions.

[0074] It may further include step S4: obtained through formula calculation. When the internal pressure (p) is between 0 and 5 MPa, construct the following Figure 4 relationship diagram of the critical penetration speed of the pipeline and the internal pressure of the pipeline (the penetration limit increases approximately linearly with the increase of the internal pressure. This can also be explained as that the internal pressure enhances the equivalent stiffness of the pressurized pipeline, which requires more impact energy to reach the impact limit). When the critical penetration speed is in region A, the penetrator at the current speed will penetrate through the pressurized pipeline. When the critical penetration speed is in region B, the penetrator at the current speed will not penetrate through the pressurized pipeline.

[0075] Through Figure 4 the relationship diagram, engineers can clearly see the critical penetration speed under different internal pressures in actual engineering. Then, based on the determination of the pressurized pipeline penetration failure, it is possible to simply and clearly understand what impact speed the penetration needs to reach to cause the pipeline to penetrate, so as to provide protection opinions and protection measures for the existing pipeline according to the calculation results.

[0076] The determination method for the penetration failure of a pressurized pipeline provided by the present invention only needs to obtain the characteristic parameters of the pipeline and the penetrator in step S1, and can directly obtain the critical penetration speed of the pressurized pipeline, which can provide data for analyzing and judging the penetration problem of the pressurized pipeline more quickly, conveniently and efficiently, so as to judge the penetration failure situation of the pressurized pipeline. The determination method for the penetration failure of the pressurized pipeline has high universality, thus providing a more effective determination method for preventing penetrators from penetrating in the field of pressurized pipelines.

[0077] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and deformations can still be made, and these improvements and deformations should also be regarded as the protection scope of the present invention.

Claims

1. A determination method for the failure of a pressurized pipeline penetration, characterized in that The steps include: S1. Obtain the initial parameters of the penetrator, including the initial velocity v and mass m; S2. Calculate the critical penetration velocity \(v\) of the pressurized pipeline based on the initial parameters of the penetrator and the parameters of the pressurized pipeline pl ; Calculate the critical penetration velocity \(v\) of the pressurized pipeline pl The calculation formula is as follows: where v pl is the critical penetration velocity of the pressurized pipeline, with the unit of m / s; k is the petal splitting coefficient, defined as θ1 is the initial flipping angle, which is the flipping angle of the failed part of the pipe wall relative to its initial position at the beginning of the petal splitting stage; θ2 is the final flipping angle, which is the flipping angle of the failed part of the pipe wall relative to its initial position at the end of the petal splitting stage; m is the mass of the penetrator, with the unit of kg; t is the wall thickness of the pipeline, with the unit of m; a is the petal length of the petal triangle formed in the petal splitting stage, with the unit of m; l is the length of the perpendicular bisector of the petal triangle formed in the petal splitting stage, with the unit of m; ρ is the density of the pipeline material, with the unit of kg / m 3 ; p is the internal pressure of the pipeline, with the unit of MPa; n is the number of cracks formed in the petal splitting stage of the pipeline; Y is the yield strength, with the unit of MPa; S3. Compare the initial velocity v of the penetrator with the critical penetration velocity v of the pressurized pipeline calculated in step S2 pl , if v < v pl , then the penetrator will not penetrate the pipeline; if v > v pl , then the penetrator will penetrate the pipeline; S4: Construct a penetration failure judgment curve with the critical penetration velocity v of the pressurized pipeline as the y-axis and the internal pressure p of the pipeline as the x-axis. If the initial velocity v of the penetrator is above the penetration failure judgment curve, the penetrator will penetrate the pipeline; if the initial velocity v of the penetrator is below the penetration failure judgment curve, the penetrator will not penetrate the pipeline. pl For the y-axis, the internal pressure p of the pipeline is the penetration failure judgment curve of the x-axis. If the initial velocity v of the penetrator is above the penetration failure judgment curve, the penetrator will penetrate the pipeline; if the initial velocity v of the penetrator is below the penetration failure judgment curve, the penetrator will not penetrate the pipeline.

2. The determination method for the failure of a pressurized pipeline penetration according to claim 1, characterized in that Calculate the critical penetration velocity v of the pressurized pipeline in step S2 pl Specifically, it includes the following steps: S21. Calculate the penetrator velocity v1 and the total bending moment M of the cantilever flap at the end of the petal splitting stage p and the energy change ΔW before and after the flipping stage R : Obtain the algebraic expression of the penetrator velocity v1 at the end of the stage from the moment balance equation in the petal splitting stage: where v1 is the penetrator velocity at the end of the petal fracture stage, with the unit of m / s; k is the petal fracture coefficient, defined as v0 is the initial velocity of the penetrator, with the unit of m / s; The total bending moment M of the cantilever flap p is calculated as follows: where M p is the total bending moment of the cantilever flap, in N*m; Y is the yield strength, in MPa; t is the wall thickness of the pipe, in m; p is the internal pressure of the pipe, in MPa; l is the length of the perpendicular bisector of the petal triangle formed in the petal splitting stage, in m; B is the base width of a single petal, in m; x is the moving distance of the plastic hinge formed in the petal splitting stage, in m; The energy change ΔW before and after the flipping phase R is calculated as follows: where ΔW R is the energy change before and after the flipping stage, in MJ; m is the mass of the penetrator, in kg; n is the number of cracks formed during the pipe petal fracture stage; ρ is the density of the pipe material, in kg / m 3 ; a is the petal length of the petal triangle formed during the petal fracture stage, in m; v r is the residual velocity of the penetrator, in m / s; S22. Substitute the penetrator velocity v1 at the end of the petal splitting stage, the total bending moment M of the cantilever petal p , and the energy change ΔW before and after the rotation stage R into the energy balance equation in the flipping stage: S23. From the residual velocity v r being 0 m / s, after simplifying the above equilibrium equation, the critical penetration velocity v pl of the pressurized pipeline is obtained, and the where v pl is the critical penetration velocity of the pressurized pipeline, with the unit of m / s; k is the petal splitting coefficient, defined as θ1 is the initial flipping angle, which is the flipping angle of the failed part of the pipe wall relative to its initial position at the beginning of the petal splitting stage; θ2 is the final flipping angle, which is the flipping angle of the failed part of the pipe wall relative to its initial position at the end of the petal splitting stage; m is the mass of the penetrator, with the unit of kg; t is the wall thickness of the pipeline, with the unit of m; a is the petal length of the petal triangle formed in the petal splitting stage, with the unit of m; l is the length of the perpendicular bisector of the petal triangle formed in the petal splitting stage, with the unit of m; ρ is the density of the pipeline material, with the unit of kg / m 3 ; p is the internal pressure of the pipeline, with the unit of MPa; n is the number of cracks formed in the petal splitting stage of the pipeline; Y is the yield strength, with the unit of MPa.

3. The determination method for the failure of a pressurized pipeline penetration according to claim 1, characterized in that, The diameter-thickness ratio of the pressurized pipeline is greater than or equal to 42.

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