Pipeline wet creep performance experimental device and experimental method

Abstract

The invention discloses a pipeline wet creep performance experimental device and experimental method.The experimental device comprises a base unit, a water tank and a loading unit, the base unit comprises a base and a pressure sensor, and the pressure sensor is arranged on the base; the water tank is arranged on the pressure sensor, the top of the water tank is open, and a pipeline is placed in the water tank; the loading unit is provided with a loading end, and the loading end can apply load to the pipeline in the vertical downward direction. The experimental method comprises the following steps: measuring and calculating the initial ring stiffness and experimental load of the pipeline; placing the pipeline in a water tank, injecting water into the water tank until the pipeline is completely submerged, and applying an experimental load to the pipeline through a loading unit; and recording the data of the deflection of the pipeline along with time change. Compared with the prior art, the experimental device for the wet creep performance of the pipeline, provided by the invention, is low in cost and simple and convenient to operate, can be used for batch parallel testing, and can be used for accurately simulating the wet creep performance of the pipeline in a wet environment and a long-term constant load.

Description

Technical Field

[0001] This invention relates to the field of testing the wet creep performance of pipelines, specifically to an experimental apparatus and method for testing the wet creep performance of pipelines. Background Technology

[0002] Glass fiber reinforced plastic (GFRP) pipes are widely used in municipal engineering, petrochemical, and marine engineering fields with extremely high durability requirements due to their outstanding advantages such as lightweight, high strength, excellent corrosion resistance, and convenient construction. During their service life, these pipes not only need to withstand long-term static and dynamic loads, but their performance is also significantly affected by the environment (especially moisture and chemical media). In actual engineering projects, pipes are often buried underground or submerged in water, operating in a continuously humid or alternating wet-dry environment. Moisture can penetrate into the composite material, potentially causing plasticization, swelling, or even hydrolysis of the resin matrix, as well as debonding at the fiber / resin interface, leading to degradation of material properties, especially long-term creep performance. Therefore, accurately assessing and predicting the long-term mechanical behavior of GFRP pipes in humid environments is crucial for ensuring their structural safety and reliability throughout their entire design life.

[0003] However, current experimental methods for studying the wet creep performance of this type of pipeline have significant limitations. Conventional experimental setups often fall short in simulating real humid environments, enabling parallel testing of multiple samples, and ensuring long-term constant loads, thus affecting the accuracy, reliability, and efficiency of experimental data.

[0004] Therefore, there is an urgent need in this field for a testing scheme that can overcome the above-mentioned defects, namely, a low-cost, easy-to-operate, batch-capable, and accurate simulation method and supporting equipment for testing the wet creep performance of pipelines under humid environments and long-term loads. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned technical deficiencies and propose a test device and method for testing the wet creep performance of pipelines, thereby solving the technical problem that the existing technology lacks test equipment that can simulate a real wet environment, achieve parallel testing of multiple samples, and ensure long-term constant load.

[0006] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a test apparatus for the wet creep performance of a pipeline, comprising: a base unit, a water tank, and a loading unit. The base unit includes a base and a pressure sensor, wherein the pressure sensor is disposed on the base; A water tank is mounted on the pressure sensor, with an open top and the interior of the tank used to house pipes. The loading unit has a loading end that can apply a load to the pipe in a vertically downward direction.

[0008] In some embodiments, the loading unit includes multiple support rods, a loading plate, and a counterweight. The multiple support rods are vertically arranged and arranged around the water tank, with their lower ends fixedly connected to the base. The loading plate is located directly above the water tank and is slidably connected to each of the support rods, and can slide along the support rods in the vertical direction. The counterweight is placed on the loading plate, and the loading plate is used to apply a load to the pipeline.

[0009] In some embodiments, the loading unit further includes a pressure block, the lower end of which is the loading end. The length of the loading end is greater than the length of the pipe. The pressure block is located below the loading plate and can extend into the water tank and contact the pipe. The loading plate applies a load to the pipe through the pressure block.

[0010] In some embodiments, the loading unit further includes a fixing nut, the support rod has an external thread, the loading plate has through holes corresponding to the support rod, the fixing nut is fitted onto the support rod and engaged with the external thread, and the loading plate rests on the fixing nut.

[0011] In some embodiments, the water tank is transparent at least on one side facing one end of the pipe.

[0012] Secondly, the present invention also provides a method for testing the wet creep performance of a pipeline, using the aforementioned pipeline wet creep performance testing apparatus, comprising the following steps: Measure and calculate the initial ring stiffness and experimental load of the pipeline; The pipe is placed in a water tank, and water is added to the tank until the pipe is completely submerged. The experimental load is then applied to the pipe through the loading unit. Record data on how the pipe deflection changes over time.

[0013] In some embodiments, measuring the initial ring stiffness and experimental load of the pipeline includes the following steps: Multiple reference lines are drawn along the diameter of the pipe at one end. The reference lines are evenly distributed around the circumference of the pipe. The wall thickness, length, outer diameter and middle diameter of the pipe are measured and calculated at each reference line. Then the average wall thickness, average length, average outer diameter and average middle diameter of the pipe are calculated. The pipe is placed in a universal testing machine, and the universal testing machine gradually increases the load applied to the pipe at a preset speed until the pipe deflection reaches the preset experimental value and then stops. The load applied by the universal testing machine at this time is the initial load. Then, the initial ring stiffness of the pipe is calculated based on the initial load, and the experimental load of the pipe is calculated based on the initial ring stiffness.

[0014] In some embodiments, one of the reference lines is selected as the initial reference line, and when the pipe is placed in the universal testing machine and in the water tank, the initial reference line points in the same direction to the pipe end face.

[0015] In some embodiments, the loading speed v of the universal testing machine is calculated using the formula: v = 0.00035D 2 / e, where D is the average mean diameter of the pipe and e is the average thickness of the pipe.

[0016] In some embodiments, the relationship between ring stiffness S and load F is: S = (0.0186 + 0.025Δy / D)F / (ΔyL), where Δy is the deformation of the pipe, L is the average length of the pipe, and D is the average mean diameter of the pipe.

[0017] Compared with the prior art, the experimental device for wet creep performance of pipelines provided by the present invention is low in cost, easy to operate, can be used for batch parallel testing, and can accurately simulate the wet creep performance of pipelines under humid environment and long-term constant load. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the pipe wet creep performance test device provided in an embodiment of the present invention; Figure 2 This is a flowchart of the experimental method for testing the wet creep performance of pipelines provided in an embodiment of the present invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0020] To address the technical problems caused by the deficiencies of existing experimental devices, this invention provides a pipe wet creep performance experimental device, which can better simulate the wet creep performance of pipes under humid environments and long-term constant loads.

[0021] It should be noted that the pipe wet creep performance testing device described in this invention is used for, but not limited to, testing composite material pipes. For ease of explanation, this invention will only use the pipe wet creep performance testing device to test composite material pipes as an example. The principle of the pipe wet creep performance testing device for testing other types of pipes is essentially the same as that for testing composite material pipes, and will not be elaborated here.

[0022] Please see Figure 1 , Figure 1This is a schematic diagram of the structure of the pipeline wet creep performance testing device provided in an embodiment of the present invention. The pipeline wet creep performance testing device includes a base unit 1, a water tank 2, and a loading unit 3.

[0023] The base unit 1 includes a base 11 and a pressure sensor 12. The pressure sensor 12 is mounted on the base 11 and can measure the pressure above, allowing experimenters to check whether the load is applied as required. The pressure sensor 12 can also be connected to an external strain gauge, deflection dial gauge, or computer to import the data signal into specialized equipment for automated processing, thereby improving data processing efficiency and accuracy.

[0024] Water tank 2 is mounted on pressure sensor 12. The top of water tank 2 is open, and it is filled with water to simulate a humid environment. The interior of water tank 2 houses pipes 5. Water tank 2 can hold one pipe 5, or a larger water tank 2 can be used to place multiple pipes 5 side-by-side, enabling parallel testing of multiple samples. Sufficient space must be provided between each pipe 5 and between the pipe 5 and the side wall of water tank 2 to allow for pipe 5 deformation.

[0025] The loading unit 3 has a loading end, which can apply a load to the pipe 5 in a vertically downward direction.

[0026] In some embodiments, the water tank 2 is transparent on at least one side facing one end of the pipe 5, for example, it can be made of glass or acrylic sheet, so that the experimenter can observe the deformation of the pipe 5. Of course, in other embodiments, the water tank 2 may have more sides, or all sides may be made of transparent material.

[0027] In some embodiments, the loading unit 3 includes multiple support rods 31, a loading plate 32, and a counterweight 33. The multiple support rods 31 are vertically arranged and surround the water tank 2, with their lower ends fixedly connected to the base 11. For added stability, the upper ends of each support rod 31 can also be connected to the same fixed plate 34. The loading plate 32 is located directly above the water tank 2 and is slidably connected to each support rod 31, allowing it to slide vertically along the support rods 31. The counterweight 33 is placed on the loading plate 32, which is used to apply load to the pipe 5.

[0028] Based on the above embodiments, the loading unit 3 further includes a pressure block 35. The lower end of the pressure block 35 is the loading end, which can extend into the water tank 2 and contact the pipe 5. The length of the loading end is greater than the length of the pipe 5, so that the loading end can extend a certain distance from both ends of the pipe 5, making the pipe 5 uniformly stressed along its length. The pressure block 35 is located below the loading plate 32. The pressure block 35 can be fixedly connected to the lower surface of the loading plate 32, or the loading plate 32 can simply be placed on the pressure block 35, with the weight of the counterweight 33 pressing the pressure block 35, and applying a load to the pipe 5 through the pressure block 35.

[0029] Based on the above embodiments, the loading unit 3 further includes a fixing nut 36, a support rod 31 with external threads, and a loading plate 32 with through holes corresponding to the support rod 31. The fixing nut 36 is fitted onto the support rod 31 and engaged with the external threads, and the loading plate 32 rests on the fixing nut 36. When not conducting experiments or during experimental preparation, the fixing nut 36 keeps the loading plate 32 in a higher position to facilitate operation by the experimenter inside the water tank 2. During laboratory testing, the fixing nut 36 is screwed downwards along the support rod 31, causing the pressure block 35 to press against the pipe 5, and the fixing nut 36 disengages from the loading plate 32.

[0030] Please see Figure 2 , Figure 2 This is a flowchart of a pipeline wet creep performance test method provided in an embodiment of the present invention. This pipeline wet creep performance test method, using the aforementioned pipeline wet creep performance test apparatus, includes the following steps: S1 measures and calculates the initial ring stiffness and experimental load of pipe 5.

[0031] S2 places pipe 5 in water tank 2, fills water tank 2 until pipe 5 is completely submerged, and applies experimental load to pipe 5 through loading unit 3.

[0032] S3 records data on how the pipe's deflection changes over time.

[0033] In some embodiments, measuring the initial ring stiffness and experimental load of pipe 5 in step S1 includes the following steps: Draw multiple reference lines along the diameter of pipe 5 at one end. The reference lines are evenly distributed around the circumference of the pipe. Measure and calculate the wall thickness, length, outer diameter, and middle diameter of pipe 5 at each reference line. Then calculate the average wall thickness, average length, average outer diameter, and average middle diameter of pipe 5.

[0034] Pipe 5 is placed in a universal testing machine, which integrates tensile, bending, compression, shear, and ring stiffness testing functions and is mainly used for mechanical property testing of metallic and non-metallic materials. The load applied to pipe 5 is gradually increased at a preset speed until the deflection of pipe 5 reaches the preset experimental value, at which point the load applied by the universal testing machine is the initial load. Then, the initial ring stiffness of pipe 5 is calculated based on the initial load, and the experimental load of pipe 5 is calculated based on the initial ring stiffness.

[0035] Based on the above embodiments, one of the reference lines is selected as the initial reference line. When the pipe 5 is placed in the universal testing machine and in the water tank 2, the initial reference line points to the same direction on the end face of the pipe 5.

[0036] In practice, different colors can be used to distinguish the initial reference line from other reference lines; that is, use one color to draw the initial reference line and another color to draw other reference lines.

[0037] In this embodiment, three pairs of reference lines are drawn, each pair lying on the same diameter, thus forming six reference lines spaced 60° apart. One pair of reference lines is selected as the initial reference lines. During the experiment, one of the initial reference lines is placed vertically downwards in the universal testing machine, so that the position where the universal testing machine applies the load to the pipe 5 is facing the other initial reference line. The universal testing machine is controlled to apply a preload, slightly pressing down on the pipe 5, and then the load and displacement are reset to zero.

[0038] Start the universal testing machine and gradually increase the load applied to pipe 5 at a preset speed. The formula for calculating the loading speed v is: v = 0.00035D 2 / e, where D is the average mean diameter of pipe 5 and e is the average thickness of pipe 5. The test continues until the deflection of pipe 5 reaches a preset experimental value, which in this embodiment is 3% of the average mean diameter of pipe 5. At this point, the universal testing machine applies the initial load F0. Based on the relationship between ring stiffness S and load F: S = (0.0186 + 0.025Δy / D)F / (ΔyL), where Δy is the deformation of the pipe, and Δy0 is calculated from the degree of deformation, i.e., 3% of the average mean diameter of pipe 5, and L is the average length of the pipe. Substituting the initial load F0 into the formula yields the initial ring stiffness S0. Then, substitute the initial ring stiffness S0 back into the formula S=(0.0186+0.025Δy / D)F / (ΔyL). Here, Δy1 is taken as the deformation of the pipe in this experiment. For example, if the pipe deflection needs to reach 9% of the average mean diameter of pipe 5 in this experiment, then calculate Δy1. Then, calculate the experimental load F1 based on the initial ring stiffness S0 and the experimental deformation Δy1.

[0039] It should be noted that the preset deformation value in the universal testing machine is within the elastic deformation range of the pipe, and it can automatically return to its original shape after the load is removed.

[0040] Then, place pipe 5 in the water tank 2 in the same orientation, i.e., with the initial reference line vertical, and one of the pipes abutting against the bottom plate of the water tank 2. Fill the water tank 2 with water until pipe 5 is completely submerged, remove the support of the fixing nut 36, and lower the loading plate 32 so that the pressure block 35 presses against the other initial reference line. Then, place the counterweight 33 corresponding to the experimental load F1 on the loading plate 32.

[0041] Then, a deflection measuring device, such as a dial gauge, is used to measure the deflection of the pipe and record the relationship between the deflection and time.

[0042] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A test apparatus for wet creep performance of pipelines, characterized in that, include: A base unit, comprising a base and a pressure sensor, wherein the pressure sensor is disposed on the base; A water tank is mounted on the pressure sensor, with an open top and the interior of the tank for housing pipes. A loading unit having a loading end capable of applying a load to the pipe in a vertically downward direction.

2. The experimental apparatus for testing the wet creep performance of pipelines according to claim 1, characterized in that, The loading unit includes multiple support rods, a loading plate, and a counterweight. The multiple support rods are vertically arranged and surround the water tank, with their lower ends fixedly connected to the base. The loading plate is located directly above the water tank and is slidably connected to each of the support rods, allowing it to slide vertically along the support rods. The counterweight is placed on the loading plate, which is used to apply a load to the pipeline.

3. The experimental apparatus for testing the wet creep performance of pipelines according to claim 2, characterized in that, The loading unit also includes a pressure block, the lower end of which is the loading end. The length of the loading end is greater than the length of the pipe. The pressure block is located below the loading plate and can extend into the water tank and contact the pipe. The loading plate applies a load to the pipe through the pressure block.

4. The experimental apparatus for testing the wet creep performance of pipelines according to claim 2, characterized in that, The loading unit also includes a fixing nut, the support rod has an external thread, the loading plate has through holes corresponding to the support rod, the fixing nut is fitted on the support rod and engaged with the external thread, and the loading plate rests on the fixing nut.

5. The experimental apparatus for testing the wet creep performance of pipelines according to claim 1, characterized in that, The water tank is transparent on at least one side facing one end of the pipe.

6. A test method for the wet creep performance of a pipeline, characterized in that, The pipeline wet creep performance test apparatus as described in any one of claims 1-5 includes the following steps: Measure and calculate the initial ring stiffness and experimental load of the pipeline; The pipe is placed in a water tank, and water is added to the tank until the pipe is completely submerged. The experimental load is then applied to the pipe through the loading unit. Record data on how the pipe deflection changes over time.

7. The experimental method for the wet creep performance of pipelines according to claim 6, characterized in that, The measurement of the initial ring stiffness and experimental load of the pipeline includes the following steps: Multiple reference lines are drawn along the diameter of the pipe at one end. The reference lines are evenly distributed around the circumference of the pipe. The wall thickness, length, outer diameter and middle diameter of the pipe are measured and calculated at each reference line. Then the average wall thickness, average length, average outer diameter and average middle diameter of the pipe are calculated. The pipe is placed in a universal testing machine, and the universal testing machine gradually increases the load applied to the pipe at a preset speed until the pipe deflection reaches the preset experimental value and then stops. The load applied by the universal testing machine at this time is the initial load. Then, the initial ring stiffness of the pipe is calculated based on the initial load, and the experimental load of the pipe is calculated based on the initial ring stiffness.

8. The experimental method for the wet creep performance of pipelines according to claim 7, characterized in that, Choose one of the reference lines as the initial reference line. When placing the pipe in the universal testing machine and in the water tank, the initial reference line points in the same direction to the pipe end face.

9. The experimental method for the wet creep performance of pipelines according to claim 7, characterized in that, The formula for calculating the loading speed v of the universal testing machine is: v = 0.00035D 2 / e, where D is the average mean diameter of the pipe and e is the average thickness of the pipe.

10. The experimental method for the wet creep performance of a pipeline according to claim 7, characterized in that, The relationship between ring stiffness S and load F is: S = (0.0186 + 0.025Δy / D)F / (ΔyL), where Δy is the deformation of the pipe, L is the average length of the pipe, and D is the average mean diameter of the pipe.

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