Fatigue test device and simulation method for vortex-induced vibration of glass fiber reinforced flexible pipe

Abstract

The invention discloses a fatigue test device for vortex-induced vibration of a glass fiber reinforced flexible pipe and a simulation method, and relates to the field of glass fiber reinforced flexible pipes. The simulation method comprises the steps that a pipeline is equally divided in the length direction of the pipeline, and n pipeline sections with the length being S are obtained; based on the distributed load in the length direction of the pipeline, the equivalent position of the equivalent concentrated force and the equivalent action point corresponding to each pipeline section is calculated; calculating the setting position of a pull rope corresponding to each lever in each layer of levers according to the equivalent concentrated force corresponding to each pipeline section and the equivalent position of the equivalent action point; vortex-induced vibration simulation is carried out on the pipeline based on the arrangement position of each lever in the tension transmission assembly corresponding to the pull rope, and accurate simulation of vortex-induced vibration is realized.

Description

Technical Field

[0001] The invention relates to the field of glass fiber reinforced flexible pipes, and in particular to a fatigue test device and a simulation method for vortex-induced vibration of glass fiber reinforced flexible pipes. Background Art

[0002] Fiber reinforced polymer (FRP) pipes are widely used in marine engineering and oil and gas production due to their light weight, high strength and corrosion resistance. However, in the marine environment, flexible pipes are exposed to vortex-induced vibration (VIV) caused by ocean currents and waves, which can cause fatigue damage to the pipes and shorten their service life. In order to optimize the design, extend the service life and reduce operating costs, it is essential to conduct systematic experimental research on the vibration fatigue characteristics of fiber reinforced flexible pipes under wave action. Such research helps to gain a deeper understanding of the behavior of materials under complex marine conditions and provide a scientific basis for improving the safety and reliability of structures.

[0003] Traditional vortex-induced vibration test equipment has the problems of high cost, complex structure and long test cycle. In order to simulate the complex marine environment, these devices usually need to be equipped with expensive wave simulation systems and large vibration platforms, which further increases the cost. In addition, the existing test machines are not accurate enough in simulating real working conditions, and it is difficult to fully reproduce the fatigue damage of flexible pipes under actual working conditions. Therefore, the development of an efficient, low-cost test equipment that can accurately simulate the fatigue vibration of flexible pipes under wave effects has become a problem that needs to be solved in the current technical field. Summary of the invention

[0004] In order to reduce the cost of vortex-induced vibration simulation and effectively realize the fatigue performance test of glass fiber reinforced flexible pipe, the present invention proposes a fatigue test device for vortex-induced vibration of glass fiber reinforced flexible pipe, including a first tension component, a second tension component, and a tension transmission component;

[0005] The pulling direction of the first pulling component is perpendicular to the length direction of the pipeline, one end of the pulling force transmission component is connected to the first pulling component, and the other end is divided into a plurality of branches parallel to the pulling direction of the first pulling component and respectively connected to a plurality of action points of the pipeline;

[0006] The first tension component applies a tension force to pull the pipe to bend in a direction perpendicular to its length;

[0007] The pulling direction of the second pulling component is parallel to the length direction of the pipeline, and the second pulling component applies pulling force to straighten the bent pipeline.

[0008] Furthermore, it also includes a fixed frame, and the first tension component, the second tension component and the pipeline are all fixed on the fixed frame;

[0009] The first tension component is perpendicular to the pipeline, the second tension component and the pipeline are located on the same straight line, and one end of the pipeline is fixed on a fixed frame, and the other end is connected to the output end of the second tension component 1.

[0010] Furthermore, the first tension component and the second tension component both use tension cylinders;

[0011] The tension transmission component includes multiple layers of levers parallel to the length direction of the pipeline, the lever layer close to the pipeline is the first layer; the lever layer close to the first tension component is the last layer, the number of levers in this layer is one, and the pipeline is facing the direction of the first tension component, and the number of levers in the previous layer is twice the number of levers in the next layer;

[0012] The first tension component and the last layer of levers, two adjacent layers of levers, and the first layer of levers and the pipeline are all connected by pull ropes.

[0013] Furthermore, from the direction of the pipeline toward the first tension component, both ends of the levers of the rear layer are provided with pull ropes connected to two adjacent levers in the front layer.

[0014] The present invention also proposes a simulation method for vortex-induced vibration of a glass fiber reinforced flexible pipe, which is applied to a fatigue test device and comprises:

[0015] Divide the pipeline equally along its length to obtain n pipeline segments of length S. Let the starting point of each pipeline segment be L. i , L i =i*S, n=2 p , i=0,1,2…n-1; p is a positive integer greater than 1; L i It corresponds to the starting position of the i+1th pipeline segment;

[0016] Based on the distributed load f(x) along the length of the pipeline, the equivalent concentrated force and the equivalent position of the equivalent action point corresponding to each pipeline section are calculated; where x represents the position coordinate along the length of the pipeline;

[0017] Calculate the setting position of the pull rope corresponding to each lever in each layer of levers according to the equivalent concentrated force corresponding to each pipeline section and the equivalent position of the equivalent action point;

[0018] The vortex-induced vibration of the pipeline is simulated based on the setting position of the pull rope corresponding to each lever in the tension transmission component.

[0019] Furthermore, in the tension transmission assembly, the total number of levers is E, and the number of levers in any layer is N. e ; Where: E = log 2 (n); n represents the number of pipeline sections, e represents the layer number, e=1…E.

[0020] Furthermore, the calculation formula of the distributed load f(x) along the length of the pipeline is:

[0021] Where x represents the position coordinate along the length of the pipeline, L represents the total length of the pipeline; f max Indicates the maximum value of the distributed load.

[0022] Furthermore, the calculation of the equivalent concentrated force and the equivalent position of the equivalent action point corresponding to the pipeline section is as follows:

[0023] Calculate the equivalent concentrated force F of the i-th pipeline segment i ′, the calculation formula is: F i ′ represents the equivalent concentrated force corresponding to the i-th pipeline segment;

[0024] Calculate the moment M corresponding to the i-th pipeline segment i ′ , the calculation formula is:

[0025] By equivalent concentrated force F i ′ With torque M i ′ Calculate the equivalent length d of the i-th pipe segment i ′ , the calculation formula is:

[0026] According to the equivalent length d i ′ Calculate the equivalent position W of the i-th pipeline segment i , the calculation formula is: i =L i-1 +d i ′ .

[0027] Furthermore, the setting position of the pull rope corresponding to each lever in each layer of levers is calculated according to the equivalent concentrated force corresponding to each pipeline section and the equivalent position of the equivalent action point; specifically:

[0028] Based on the length direction of the pipeline, the pipeline segments are combined into multiple pipeline groups, each of which corresponds to a lever in the first layer;

[0029] The length of the target lever corresponding to the pipeline group is calculated by the equivalent position of the equivalent action point corresponding to each pipeline segment in the pipeline group; the first equivalent length and the second equivalent length of the target lever and their corresponding equivalent concentrated force are calculated by using the lever principle and combining the equivalent concentrated force of each pipeline segment in the pipeline group; the equivalent position of the target lever is determined based on the first equivalent length and the second equivalent length, and the target lever represents the lever in the first layer corresponding to the pipeline group;

[0030] Starting from the second layer, based on the number of levers in the previous layer, the levers are combined in pairs to form lever groups, and each lever group corresponds to a lever in the current layer; for each lever group, the length of the corresponding lever in the current layer is calculated using the equivalent position corresponding to each lever in the lever group; then, the first equivalent length and the second equivalent length of the lever in the current layer and its equivalent concentrated force are calculated using the equivalent concentrated force of each lever in the lever group and the length of the corresponding lever in the current layer; based on the first equivalent length and the second equivalent length, the equivalent position of the corresponding lever in the current layer is determined; this process is performed layer by layer until the calculation of all layers is completed.

[0031] Furthermore, when the layer number e>1 of the current layer, in each lever group of the previous layer, the equivalent positions of the two levers are connected to the two ends of the corresponding levers of the current layer e through a pull rope; when the layer number e=1 of the current layer, the two ends of each lever in the current layer are respectively connected to the equivalent positions of the two pipe segments in the corresponding pipe group through a pull rope.

[0032] Compared with the prior art, the present invention has at least the following beneficial effects:

[0033] (1) The vortex-induced vibration fatigue test device for glass fiber reinforced flexible pipes proposed in the present invention has a simple structure, does not rely on large equipment and expensive control systems, can effectively simulate the vortex-induced vibration effect under the action of waves, and greatly reduces the R&D and maintenance costs compared with traditional vortex-induced vibration test equipment;

[0034] (2) The simulation method of vortex-induced vibration of a glass fiber reinforced flexible pipe proposed in the present invention comprises: dividing the pipe equally along the length direction of the pipe to obtain n pipe sections with a length of S; calculating the equivalent concentrated force and the equivalent position of the equivalent action point corresponding to each pipe section based on the distributed load along the length direction of the pipe; calculating the setting position of the pull rope corresponding to each lever in each layer of levers according to the equivalent concentrated force and the equivalent position of the equivalent action point corresponding to each pipe section; simulating the vortex-induced vibration of the pipe based on the setting position of the pull rope corresponding to each lever in the tension transmission component, thereby realizing accurate simulation of the vortex-induced vibration;

[0035] (3) The present invention achieves precise control of the stress conditions of each part of the pipeline through reasonable pipeline segmentation and equivalent concentrated force calculation, ensuring that the load applied during the test is consistent with the actual situation. This helps to more accurately reproduce the fatigue damage of the flexible pipe under actual working conditions and provides a reliable basis for improving the design;

[0036] (4) In the present invention, starting from the second layer, based on the number of levers in the previous layer, the levers are combined in pairs in sequence to form lever groups, and each lever group corresponds to a lever in the current layer; for each lever group, the length of the corresponding lever in the current layer is calculated using the equivalent position corresponding to each lever in the lever group; then, the first equivalent length and the second equivalent length of the lever in the current layer and their equivalent concentrated force are calculated using the equivalent concentrated force of each lever in the lever group and the length of the corresponding lever in the current layer; based on the first equivalent length and the second equivalent length, the equivalent position of the corresponding lever in the current layer is determined; this process is performed layer by layer until the calculation of all layers is completed, that is, the present invention uses multiple layers of levers and pull ropes to convert complex distributed loads into equivalent concentrated forces, and gradually integrates the points of force application in a layer-by-layer progressive manner; this method not only simplifies the mechanical model, but also improves the authenticity and accuracy of the simulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a structural schematic diagram of a fatigue testing device for vortex-induced vibration of a glass fiber reinforced flexible pipe according to an embodiment of the present invention;

[0038] Figure 2 A flow chart of a method for simulating vortex-induced vibration of a glass fiber reinforced flexible pipe according to an embodiment of the present invention;

[0039] Figure 3 FIG. 4 is a distributed load diagram along the length direction of the pipeline according to an embodiment of the present invention.

[0040] In the figure: 1. first tension component; 2. second tension component; 3. fixed frame; 4. pipeline; 5. pull rope; 6. lever. DETAILED DESCRIPTION

[0041] The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.

[0042] Embodiment 1

[0043] In order to reduce the cost of vortex-induced vibration simulation and effectively realize the fatigue performance test of glass fiber reinforced flexible pipes, such as Figure 1 As shown, the present invention proposes a fatigue test device for vortex-induced vibration of glass fiber reinforced flexible pipes, comprising a first tension component 1, a second tension component 2, and a tension transmission component responsible for transmitting tension from the first tension component to the pipe;

[0044] The pulling direction of the first pulling component 1 is perpendicular to the length direction of the pipeline 4. One end of the pulling force transmission component is connected to the first pulling component 1, and the other end is divided into a plurality of branches parallel to the pulling direction of the first pulling component 1 and respectively connected to a plurality of action points of the pipeline 4.

[0045] Specifically, the force direction of the first tension component 1 is perpendicular to the length direction of the glass fiber reinforced flexible pipe, i.e., the pipe 4. This means that when the first tension component 1 applies tension, it causes the pipe to bend and deform in a direction that is perpendicular to its length direction. The tension transmission component plays a crucial bridge role. One end of it is connected to the first tension component 1, and the other end is divided into multiple branches. These branches are parallel to the tension direction of the first tension component 1 and are respectively connected to different positions of the pipe 4. This multi-point connection method ensures that the tension can be evenly distributed at various points of action on the pipe, thereby more realistically simulating various stress conditions that the pipe may encounter in actual applications.

[0046] The first tension component 1 applies tension to pull the pipe 4 to bend along a direction perpendicular to its length;

[0047] The pulling direction of the second pulling component 2 is parallel to the length direction of the pipe 4 , and the second pulling component 2 applies pulling force to straighten the bent pipe 4 .

[0048] During the bending process, the tension of the first tension component 1 causes the pipe 4 to bend and deform in a direction perpendicular to its own length. This bending simulates the vortex-induced vibration effect that the flexible pipe may experience under the action of waves. In order to complete a complete fatigue test cycle, the action of the second tension component 2 is also required. The tension direction of the second tension component 2 is parallel to the length direction of the pipe 4. Its function is to apply reverse tension to straighten the bent pipe 4 again after the first tension component 1 bends the pipe. In this way, the two tension components work together to realize the bending-straightening cycle of the pipe within a test cycle, thereby simulating the dynamic load conditions that the pipe is subjected to in the marine environment.

[0049] The first tension component 1 and the second tension component 2 both use tension cylinders;

[0050] In order to achieve the above functions, the first tension component 1 and the second tension component 2 both use tension cylinders as power sources. The tension cylinder is a hydraulic actuator that can convert the pressure energy in the hydraulic system into mechanical energy, that is, linear tension or thrust. The reason for choosing tension cylinders is that they have high output force, precise control ability and long service life, which are very suitable for use in such fatigue testing equipment that requires high precision and stability. By adjusting the pressure inside the cylinder, the tension applied to the pipeline 4 can be easily controlled, thereby changing the test conditions to adapt to different types of glass fiber reinforced flexible pipes or different research needs.

[0051] The tension transmission component includes multiple layers of levers 6 parallel to the length direction of the pipeline, the lever layer close to the pipeline 4 is the first layer; the lever layer close to the first tension component 1 is the last layer, the number of levers 6 in this layer is one, and the pipeline 4 is facing the direction of the first tension component 1, and the number of levers 6 in the previous layer is twice the number of levers 6 in the next layer;

[0052] Such a design ensures that the force can be gradually integrated and transmitted, and finally achieves effective action on the entire pipeline. Each layer of levers is connected to the upper or lower layer, as well as the first tension component 1 or the pipeline 4 itself through the pull rope 5, thus forming a multi-level, networked force transmission system. This structure not only simplifies the mechanical model, but also improves the authenticity and accuracy of the simulation, so that complex distributed loads can be effectively converted into equivalent concentrated forces that are easier to manage and simulate.

[0053] The first tension component 1 and the last layer of levers 6 , two adjacent layers of levers 6 , and the first layer of levers 6 and the pipeline 4 are all connected by pull ropes 5 .

[0054] From the pipe 4 toward the first tension assembly 1 , both ends of the lever 6 of the next layer are provided with a pull rope 5 to connect with two adjacent levers 6 in the previous layer.

[0055] The pull ropes 5 play a key role in the present invention. They are responsible for transferring the tension applied by the first tension assembly 1 to the levers of each layer step by step, and then these levers further distribute it to different parts of the pipeline. In addition, from the direction of the pipeline 4 toward the first tension assembly 1, both ends of the levers 6 of the latter layer are provided with pull ropes 5 to connect with two adjacent levers 6 in the previous layer. This connection method allows the force to be effectively transferred between different levels, and ensures that the tension can be stably and accurately transmitted to the pipeline even under complex and changing test conditions.

[0056] It also includes a fixed frame 3, on which the first tension component 1, the second tension component 2 and the pipeline 4 are all fixed;

[0057] The first tension component 1 is perpendicular to the pipeline 4 , the second tension component 2 is located on the same straight line as the pipeline 4 , and one end of the pipeline 4 is fixed on the fixed frame 3 , and the other end is connected to the output end of the second tension component 2 .

[0058] Specifically, if Figure 1 As shown, the fixed frame 3 is a rectangular frame structure, which includes two long sides and two short sides, the second tension component 2 is fixedly installed on the top of one short side, and the first tension component 1 is fixedly installed in the middle of one long side. Optionally, an isolation rod parallel to the two long sides is also provided inside the fixed frame 3, and the two ends of the isolation rod are respectively fixed on the two short sides. The isolation rod and a long side away from the first tension component 1 and the short sides on both sides together constitute an internal frame, and the pipe 4 is arranged in the internal frame, and the pipe 4 is parallel to a long side away from the first tension component 1 and the isolation rod, and the pipe 4 and a long side away from the first tension component 1 and the isolation rod have a certain distance to ensure that the pipe 4 can be bent and deformed smoothly. One end of the pipe 4 is fixed on a short side away from the second tension component 2, and the other end is fixedly connected to the output end of the second tension component 2.

[0059] The vortex-induced vibration fatigue test device for glass fiber reinforced flexible pipes proposed in the present invention has significant advantages. The device has a simple structure and can complete efficient vortex-induced vibration effect simulation without relying on large equipment and expensive control systems. Traditional vortex-induced vibration test equipment usually needs to be equipped with complex wave simulation systems and large vibration platforms, which not only increases the cost of the equipment, but also makes the operation more complicated. In contrast, the present invention achieves efficient reproduction of vortex-induced vibration phenomena under wave action through ingenious design, greatly reducing R&D and maintenance costs. More importantly, this low-cost solution does not sacrifice test accuracy, but ensures the reliability and validity of experimental data through reasonable mechanical design. For researchers and engineers, this means that they can carry out high-quality material performance evaluation under more economical conditions, thereby accelerating the research and development process of new glass fiber reinforced flexible pipes and improving the competitiveness of products in the market.

[0060] Embodiment 2

[0061] like Figure 2 As shown, the present invention also proposes a simulation method for vortex-induced vibration of glass fiber reinforced flexible pipes, which is specially designed for the aforementioned fatigue test device. The core of this simulation method is to achieve a high degree of simulation of vortex-induced vibration phenomenon through a series of precise calculations and the application of mechanical models. Specifically, the method includes:

[0062] Divide the pipeline equally along its length to obtain n pipeline segments of length S. Let the starting point of each pipeline segment be L.i , L i =i*S, n=2 p , i=0,1,2…n-1; p is a positive integer greater than 1; L i It corresponds to the starting position of the i+1th pipeline segment;

[0063] This segmentation method not only helps to simplify subsequent calculations, but also makes it possible to capture the stress changes of the pipeline at different locations in more detail.

[0064] To ensure the authenticity and accuracy of the simulation, the equivalent concentrated force and the equivalent position of the equivalent action point corresponding to each pipeline section are calculated based on the distributed load along the length of the pipeline. The distributed load here refers to the continuous force distribution acting on the surface of the pipeline, which can be used to describe the complex effects of waves or water flow on the pipeline.

[0065] Based on Figure 3 The distributed load f(x) along the length of the pipeline is shown, and the equivalent concentrated force and the equivalent position of the equivalent action point corresponding to each pipeline section are calculated; where x represents the position coordinate along the length of the pipeline;

[0066] The calculation formula for the distributed load f(x) along the length of the pipeline is:

[0067] Where x represents the position coordinate along the length of the pipeline, L represents the total length of the pipeline; f max Indicates the maximum value of the distributed load.

[0068] The calculation of the equivalent concentrated force and the equivalent position of the equivalent action point corresponding to the pipeline section is as follows:

[0069] Calculate the equivalent concentrated force F of the i-th pipeline segment i ′ , the calculation formula is: F i ′ represents the equivalent concentrated force corresponding to the i-th pipeline segment;

[0070] Calculate the moment M corresponding to the i-th pipeline segment i ′ , the calculation formula is:

[0071] By equivalent concentrated force F i ′ With torque M i ′ Calculate the equivalent length d of the i-th pipe segment i ′ , the calculation formula is:

[0072] According to the equivalent length d i ′ Calculate the equivalent position W of the i-th pipeline segment i , the calculation formula is: i =L i-1 +d i ′ .

[0073] Calculate the setting position of the pull rope corresponding to each lever in each layer of levers according to the equivalent concentrated force corresponding to each pipeline section and the equivalent position of the equivalent action point;

[0074] The setting position of the pull rope corresponding to each lever in each layer of levers is calculated according to the equivalent concentrated force corresponding to each pipeline section and the equivalent position of the equivalent action point; specifically:

[0075] Based on the length direction of the pipeline, the pipeline segments are combined into multiple pipeline groups, each of which corresponds to a lever in the first layer;

[0076] This grouping strategy not only simplifies the subsequent mechanical analysis, but also ensures the reasonable distribution of forces at different locations.

[0077] The length of the target lever corresponding to the pipeline group is calculated by the equivalent position of the equivalent action point corresponding to each pipeline segment in the pipeline group; the first equivalent length and the second equivalent length of the target lever and their corresponding equivalent concentrated force are calculated by using the lever principle and combining the equivalent concentrated force of each pipeline segment in the pipeline group; the equivalent position of the target lever is determined based on the first equivalent length and the second equivalent length, and the target lever represents the lever in the first layer corresponding to the pipeline group;

[0078] It should be noted that the equivalent action point here refers to a specific position obtained through calculation that can represent the stress condition of the pipeline section, which comprehensively considers the changing characteristics of the distributed load along the length of the pipeline. Based on these equivalent action points, the effective length of the target lever can be determined. This step is crucial to ensure that the pull rope is correctly connected to the lever, so that the force can be accurately transmitted to different parts of the pipeline.

[0079] Starting from the second layer, based on the number of levers in the previous layer, the levers are combined in pairs to form lever groups, and each lever group corresponds to a lever in the current layer; for each lever group, the length of the corresponding lever in the current layer is calculated using the equivalent position corresponding to each lever in the lever group; then, the first equivalent length and the second equivalent length of the lever in the current layer and its equivalent concentrated force are calculated using the equivalent concentrated force of each lever in the lever group and the length of the corresponding lever in the current layer; based on the first equivalent length and the second equivalent length, the equivalent position of the corresponding lever in the current layer is determined; this process is performed layer by layer until the calculation of all layers is completed.

[0080] This design principle maintains consistency, that is, the number of levers in each layer is half of the previous layer, until there is only one lever left in the last layer. Figure 1 For example, if there are 4 levers in the first layer, then there will be 2 levers in the second layer and only 1 lever in the third layer. This decreasing arrangement of levers allows complex distributed loads to be gradually converted into equivalent concentrated forces that are easier to manage and simulate, ultimately achieving effective action on the entire pipeline.

[0081] At the same time, the above calculation process is an iterative process that is progressive and progressive, aiming to gradually integrate the points of force application to achieve accurate simulation of complex distributed loads. In the calculation of each layer, two key factors are always paid attention to: one is the equivalent position of each lever in the current layer, and the other is the equivalent concentrated force borne by these levers. These two factors together determine how the force is transmitted between different levels and ultimately acts on different parts of the pipeline.

[0082] In the tension transmission assembly, the total number of levers is E, and the number of levers in any layer is N. e ; Where: E = log 2 (n); n represents the number of pipeline sections, e represents the layer number, e=1…E.

[0083] When the layer number e>1 of the current layer, in each lever group of the previous layer, the equivalent positions of the two levers are connected to the two ends of the corresponding levers of the current layer e through a pull rope; when the layer number e=1 of the current layer, the two ends of each lever in the current layer are respectively connected to the equivalent positions of the two pipe segments in the corresponding pipe group through a pull rope.

[0084] The following is based on Figure 1 The calculation of each layer is explained in detail, and the setting Figure 1 The n in is equal to 8, which means that there are 8 pipeline segments in total:

[0085] 1. Calculation of the first layer:

[0086] 1) Calculate the length of the first lever in the first layer corresponding to the first pipe group. The calculation formula includes:

[0087] Among them, lg represents the length, Indicates the length of the first lever in the first layer, which is the target lever.

[0088] 2) Calculate the first equivalent length and the second equivalent length of the first lever in the first layer and their corresponding equivalent concentrated forces:

[0089] Among them, d 1 1 and d 21 represent the first equivalent length and the second equivalent length of the first lever in the first layer respectively;

[0090] F 1 ′ d 1 1 =F 2 ′ d 2 1 (Formula 3);

[0091] The first equivalent length d of the first lever in the first layer is calculated by equations 2 and 3. 1 1 With the second equivalent length d 2 1 ;

[0092] In the formula, Represents the equivalent concentrated force corresponding to the first lever in the first layer.

[0093] 3) Based on the first equivalent length d 1 1 With the second equivalent length d 2 1 , determine the equivalent position corresponding to the first lever in the first layer: Where, W represents the equivalent position; Represents the equivalent position corresponding to the first lever in the first layer.

[0094] The calculation method of the first equivalent length, second equivalent length, equivalent concentrated force and equivalent position corresponding to other levers in the first layer is the same as the calculation method of the first lever in the first layer mentioned above, and will not be repeated here.

[0095] 2. Calculation of the second layer:

[0096] 1) Based on the number of levers in the first layer, the levers are combined in pairs to form lever groups. Each lever group corresponds to a lever in the second layer. The first lever and the second lever in the first layer form the first lever group, which corresponds to the first lever in the second layer. The third lever and the fourth lever form the second lever group, which corresponds to the second lever in the second layer.

[0097] Calculate the length of the first lever in the second layer using the formula:

[0098] In the formula, They represent the equivalent positions of the second lever and the first lever in the first layer respectively; Represents the length of the first lever in the second layer.

[0099] 2) Calculate the first equivalent length and the second equivalent length of the first lever in the second layer:

[0100] Among them, d 1 2 and d 2 2 represent the first equivalent length and the second equivalent length of the first lever in the second layer respectively;

[0101] in, and They represent the equivalent concentrated forces corresponding to the first lever and the second lever in the first layer respectively;

[0102] The first equivalent length d corresponding to the first lever in the second layer is calculated by equation 2 and equation 3. 1 2 With the second equivalent length d 2 2 ;

[0103] In the formula, and represent the equivalent concentrated forces of the first lever and the second lever in the first layer respectively; Represents the equivalent concentrated force corresponding to the first lever in the second layer.

[0104] 3) Based on the first equivalent length d 1 2 With the second equivalent length d 2 2 , determine the equivalent position of the first lever in the second layer: Where, W represents the equivalent position; represents the equivalent position corresponding to the first lever in the first layer, Represents the equivalent position corresponding to the first lever in the second layer.

[0105] The calculation method of the first equivalent length, second equivalent length, equivalent concentrated force and equivalent position corresponding to other levers in the second layer is the same as the calculation method of the first lever in the second layer mentioned above, and will not be repeated here.

[0106] 2. Calculation of the third layer:

[0107] 1) Based on the number of levers in the second layer, the levers are combined in pairs to form lever groups. Each lever group corresponds to a lever in the third layer. The first lever and the second lever in the second layer are the first lever group, which corresponds to the first lever in the third layer.

[0108] Calculate the length of the first lever in the third layer using the following formula:

[0109] In the formula, represent the equivalent positions of the second lever and the first lever in the second layer respectively; Represents the length of the first lever in the third layer.

[0110] 2) Calculate the first equivalent length and the second equivalent length of the first lever in the third layer:

[0111] Among them, d 1 3 and d 2 3 represent the first equivalent length and the second equivalent length of the first lever in the third layer respectively;

[0112] in, and represent the equivalent concentrated forces corresponding to the first lever and the second lever in the second layer respectively;

[0113] The first equivalent length d corresponding to the first lever in the third layer is calculated by equation 2 and equation 3. 1 3 With the second equivalent length d 2 3 ;

[0114] In the formula, and represent the equivalent concentrated forces of the first lever and the second lever in the second layer respectively; Represents the equivalent concentrated force corresponding to the first lever in the third layer.

[0115] 3) Based on the first equivalent length d 1 3 With the second equivalent length d 2 3 , determine the equivalent position of the first lever in the third layer: Where, W represents the equivalent position; represents the equivalent position corresponding to the first lever in the second layer, It represents the equivalent position of the first lever in the third layer. Since n is 8, there is only one lever in the third layer, and the calculation is complete.

[0116] The present invention realizes accurate control of the stress conditions of each part of the pipeline through reasonable pipeline segmentation and equivalent concentrated force calculation, ensuring that the load applied during the test is consistent with the actual situation. This helps to more accurately reproduce the fatigue damage of the flexible pipe under actual working conditions and provides a reliable basis for improving the design.

[0117] At the same time, starting from the second layer, the present invention combines the levers in pairs in sequence based on the number of levers in the previous layer to form lever groups, and each lever group corresponds to a lever in the current layer; for each lever group, the length of the corresponding lever in the current layer is calculated using the equivalent position corresponding to each lever in the lever group; then, the first equivalent length and the second equivalent length of the lever in the current layer and their equivalent concentrated force are calculated using the equivalent concentrated force of each lever in the lever group and the length of the corresponding lever in the current layer; based on the first equivalent length and the second equivalent length, the equivalent position of the corresponding lever in the current layer is determined; this process is performed layer by layer until the calculation of all layers is completed, that is, the present invention uses multiple layers of levers and pull ropes to convert complex distributed loads into equivalent concentrated forces, and gradually integrates the points of force application in a layer-by-layer progressive manner; this method not only simplifies the mechanical model, but also improves the authenticity and accuracy of the simulation.

[0118] The vortex-induced vibration of the pipeline is simulated based on the setting position of the pull rope corresponding to each lever in the tension transmission component.

[0119] The simulation method of vortex-induced vibration of a glass fiber reinforced flexible pipe proposed in the present invention comprises: dividing the pipeline equally along the length direction of the pipeline to obtain n pipeline sections with a length of S; calculating the equivalent concentrated force and the equivalent position of the equivalent action point corresponding to each pipeline section based on the distributed load along the length direction of the pipeline; calculating the setting position of the pull rope corresponding to each lever in each layer of levers according to the equivalent concentrated force and the equivalent position of the equivalent action point corresponding to each pipeline section; simulating the vortex-induced vibration of the pipeline based on the setting position of the pull rope corresponding to each lever in the tension transmission component, thereby realizing accurate simulation of the vortex-induced vibration.

[0120] The present invention applies a tension perpendicular to the length direction of the pipeline through the first tension component and transmits these forces through the lever layer, thereby simulating the dynamic response under vortex-induced vibration conditions. This design is intended to reproduce the influence of vortex-induced forces caused by waves and ocean currents on the pipeline in an actual marine environment. It should be noted that in vortex-induced vibration, the vortex-induced force f(t) can be expressed as: Where: ρ is the fluid density (unit: kg / m 3 ); U is the fluid velocity (unit: m / s); C L is the lift coefficient; D is the pipe diameter (unit: m); ω v is the excitation frequency of vortex-induced vibration (unit: rad / s); t is time.

[0121] The present invention simulates vortex-induced vibration, specifically:

[0122] 1. Apply vertical tension (first tension component):

[0123] In the middle (or near the middle) of the pipeline, a constant tension is applied by the first tension component, and the tension direction is perpendicular to the length direction of the pipeline. This tension is used to simulate the force exerted on the pipeline by waves or ocean currents perpendicular to its length direction, so that the pipeline can bend in the direction perpendicular to its length.

[0124] 2. Apply parallel tension (second tension component):

[0125] At the left end of the pipe, a constant tension is applied by the second tension component, and the tension direction is parallel to the length direction of the pipe. This tension is used to simulate the process of straightening the curved pipe and reproduce the reciprocating motion of the flexible pipe in actual working conditions.

[0126] 3. Use the lever system to transmit force:

[0127] The force applied to the pipeline is distributed and transmitted through multiple layers of levers. The design of the multiple layers of levers enables each lever to integrate the equivalent concentrated force from multiple pipeline segments and transmit it to the next level. The positions of the action points of these levers (i.e., equivalent positions) are calculated based on the equivalent action points of the pipeline segments to ensure accurate force transmission. In this embodiment, the number of levers gradually decreases from the layer close to the pipeline until the layer closest to the first tension component, so that more pipeline segment forces can be gradually integrated, and finally an effective effect on the entire pipeline is formed.

[0128] In addition, the lever layer close to the pipeline is responsible for gradually decomposing the vertical tension transmitted by the first tension component and evenly distributing it to different parts of the pipeline. Each lever is connected to the equivalent action point of the corresponding pipeline section through the pull ropes at both ends to ensure that the force can be accurately transmitted to each key position, achieving fine control of the force conditions of each part of the pipeline:

[0129] 3.1 Layer-by-layer lever design: Starting from the layer closest to the pipe, the number of levers gradually decreases until the layer closest to the first tension component. Specifically, the layer closest to the pipe has the most levers, and the number of levers is halved as each layer moves back toward the first tension component. For example, the layer closest to the pipe may have multiple levers, while the next layer will have half the number of levers, and the next layer will further halve, and so on, until the last layer (close to the first tension component) has only one lever;

[0130] 3.2 Accurate transmission and distribution of force: The levers on each layer are connected to the two adjacent levers on the previous layer through the ropes at both ends, so that the force is gradually transmitted and distributed. This design ensures that the complex distributed load can be effectively converted into an equivalent concentrated force that is easier to manage and simulate, and ultimately achieves effective action on the entire pipeline at the layer closest to the pipeline.

[0131] 3.3 Optimized mechanical simulation: Through the collaborative work of multiple layers of levers, the device not only simplifies the mechanical model, but also improves the authenticity and accuracy of the simulation. The design and connection method of each layer of levers are carefully calculated to ensure that the load applied during the test is consistent with the actual situation, providing a reliable basis for improving the design of flexible pipes.

[0132] This design ensures that the force transmitted from the first tension component can be accurately and evenly distributed to different parts of the pipeline, thereby achieving efficient simulation of the dynamic response of the pipeline under vortex-induced vibration conditions.

[0133] 4. Simulate vortex-induced vibration response:

[0134] Through the synergistic effect of the above-mentioned tension and multi-layer levers, the dynamic response of the pipeline under vortex-induced vibration conditions is simulated. Specifically, the pipeline will bend and recover periodically in the direction perpendicular to its length. This motion pattern is similar to the vortex-induced vibration caused by waves and ocean currents in the actual marine environment.

[0135] In addition, during the simulation process, sensors can be used to monitor the stress, strain, and displacement of each part of the pipeline in real time to ensure that the test conditions are as consistent as possible with the actual working environment. Based on the monitoring data, the magnitude and frequency of the applied tension can be appropriately adjusted to optimize the simulation effect.

[0136] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0137] In addition, in the present invention, descriptions such as "first", "second", "one", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0138] In the present invention, unless otherwise clearly specified and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" 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 a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0139] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

Claims

1. A fatigue test device for vortex-induced vibration of glass fiber reinforced flexible pipes, characterized in that: It includes a first tension component, a second tension component, and a tension transmission component; The pulling direction of the first pulling component is perpendicular to the length direction of the pipeline, one end of the pulling force transmission component is connected to the first pulling component, and the other end is divided into a plurality of branches parallel to the pulling direction of the first pulling component and respectively connected to a plurality of action points of the pipeline; The first tension component applies a tension force to pull the pipe to bend in a direction perpendicular to its length; The pulling direction of the second pulling component is parallel to the length direction of the pipeline, and the second pulling component applies pulling force to straighten the bent pipeline.

2. The fatigue testing device for vortex-induced vibration of glass fiber reinforced flexible pipe according to claim 1 is characterized in that: It also includes a fixed frame, and the first tension component, the second tension component and the pipeline are all fixed on the fixed frame; The first tension component is perpendicular to the pipeline, the second tension component and the pipeline are located on the same straight line, and one end of the pipeline is fixed on a fixed frame, and the other end is connected to the output end of the second tension component.

3. The fatigue testing device for vortex-induced vibration of glass fiber reinforced flexible pipe according to claim 1, characterized in that: The first tension component and the second tension component both use tension cylinders; The tension transmission component includes multiple layers of levers parallel to the length direction of the pipeline, the lever layer close to the pipeline is the first layer; the lever layer close to the first tension component is the last layer, the number of levers in this layer is one, and the pipeline is facing the direction of the first tension component, and the number of levers in the previous layer is twice the number of levers in the next layer; The first tension component and the last layer of levers, two adjacent layers of levers, and the first layer of levers and the pipeline are all connected by pull ropes.

4. The fatigue testing device for vortex-induced vibration of glass fiber reinforced flexible pipe according to claim 1, characterized in that: From the direction of the pipeline toward the first tension component, both ends of the lever of the rear layer are provided with pull ropes connected with two adjacent levers in the front layer.

5. A method for simulating vortex-induced vibration of a glass fiber reinforced flexible pipe, applied to a fatigue test device, characterized in that: include: Divide the pipeline equally along its length to obtain n pipeline segments of length S. Let the starting point of each pipeline segment be L. i , L i =i*S, n=2 p , i=0,1,2…n-1; p is a positive integer greater than 1; L i It corresponds to the starting position of the i+1th pipeline segment; Based on the distributed load f(x) along the length of the pipeline, the equivalent concentrated force and the equivalent position of the equivalent action point corresponding to each pipeline section are calculated; where x represents the position coordinate along the length of the pipeline; Calculate the setting position of the pull rope corresponding to each lever in each layer of levers according to the equivalent concentrated force corresponding to each pipeline section and the equivalent position of the equivalent action point; The vortex-induced vibration of the pipeline is simulated based on the setting position of the pull rope corresponding to each lever in the tension transmission component.

6. A method for simulating vortex-induced vibration of a glass fiber reinforced flexible pipe according to claim 5, characterized in that: In the tension transmission assembly, the total number of levers is E, and the number of levers in any layer is N. e ; Where: E = log2(n); n represents the number of pipeline sections, e represents the layer number, e=1…E.

7. A method for simulating vortex-induced vibration of a glass fiber reinforced flexible pipe according to claim 6, characterized in that: The calculation formula for the distributed load f(x) along the length of the pipeline is: Where x represents the position coordinate along the length of the pipeline, L represents the total length of the pipeline; f max Indicates the maximum value of the distributed load.

8. The method for simulating vortex-induced vibration of a glass fiber reinforced flexible pipe according to claim 7, characterized in that: The calculation of the equivalent concentrated force and the equivalent position of the equivalent action point corresponding to the pipeline section is as follows: Calculate the equivalent concentrated force F of the i-th pipeline segment i ′ , the calculation formula is: i≥1,F i ′ represents the equivalent concentrated force corresponding to the i-th pipeline segment; Calculate the moment M corresponding to the i-th pipeline segment i ′ , the calculation formula is: By equivalent concentrated force F i ′ With torque M i ′ Calculate the equivalent length d of the i-th pipe segment i ′ , the calculation formula is: According to the equivalent length d i ′ Calculate the equivalent position W of the i-th pipeline segment i , the calculation formula is: W i =L i-1 +d i ′ 。 9. A method for simulating vortex-induced vibration of a glass fiber reinforced flexible pipe according to claim 8, characterized in that: The setting position of the pull rope corresponding to each lever in each layer of levers is calculated according to the equivalent concentrated force corresponding to each pipeline section and the equivalent position of the equivalent action point; specifically: Based on the length direction of the pipeline, the pipeline segments are combined into multiple pipeline groups, each of which corresponds to a lever in the first layer; The length of the target lever corresponding to the pipeline group is calculated by the equivalent position of the equivalent action point corresponding to each pipeline segment in the pipeline group; the first equivalent length and the second equivalent length of the target lever and their corresponding equivalent concentrated force are calculated by using the lever principle and combining the equivalent concentrated force of each pipeline segment in the pipeline group; the equivalent position of the target lever is determined based on the first equivalent length and the second equivalent length, and the target lever represents the lever in the first layer corresponding to the pipeline group; Starting from the second layer, based on the number of levers in the previous layer, the levers are combined in pairs to form lever groups, and each lever group corresponds to a lever in the current layer; for each lever group, the length of the corresponding lever in the current layer is calculated using the equivalent position corresponding to each lever in the lever group; then, the first equivalent length and the second equivalent length of the lever in the current layer and its equivalent concentrated force are calculated using the equivalent concentrated force of each lever in the lever group and the length of the corresponding lever in the current layer; based on the first equivalent length and the second equivalent length, the equivalent position of the corresponding lever in the current layer is determined; this process is performed layer by layer until the calculation of all layers is completed.

10. A method for simulating vortex-induced vibration of a glass fiber reinforced flexible pipe according to claim 9, characterized in that: When the layer number e>1 of the current layer, in each lever group of the previous layer, the equivalent positions of the two levers are connected to the two ends of the corresponding levers of the current layer e through a pull rope; when the layer number e=1 of the current layer, the two ends of each lever in the current layer are respectively connected to the equivalent positions of the two pipe segments in the corresponding pipe group through a pull rope.

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