An experimental device and experimental method for measuring the limit contact stress of pipeline connectors
By designing an experimental device including test piece fixture, tension tooling and dial meter, and using continuous loading experimental methods, the problem of difficulty in measuring the limit contact stress of pipeline connectors in the prior art is solved, and high-precision measurement and connector performance analysis are achieved.
Patent Information
- Application Number
- CN202210668103.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-06-14
- Publication Date
- 2025-04-25
- Estimated Expiration
- 2042-06-14
AI Technical Summary
The prior art is difficult to measure the ultimate contact stress of pipeline connections, resulting in a decrease in the connection preload force and insufficient connection strength, and a large internal contact surface, so it is impossible to conduct direct testing.
An experimental device is designed, including a test piece fixture, tension tooling, a dial gauge and a pipeline connecting ball head specimen. Through the experimental method of continuous loading, the dial gauge is used to measure displacement changes and calculate the ultimate contact stress.
Accurate measurement of the ultimate contact stress of pipeline connectors is achieved, the accuracy and reliability of experiments are improved, and the direction of technology to improve the accuracy of pipeline connectors is guided.
Smart Images
Figure CN115014932B_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of short-term relaxation testing, and relates to an experimental device and an experimental method for measuring the limit contact stress of a pipeline connector, which are used for measuring the limit contact stress of a pipe joint when the pipeline is connected. Background Art
[0002] The aircraft hydraulic pipeline system is an important part of the aircraft hydraulic system. It is connected with high-pressure plunger pumps, valves or valves, actuators, etc. to achieve different control tasks such as the retraction and extension of the aircraft's landing gear, flaps and speed brakes, and the power-assisted control of ailerons, elevators and rudders. Due to the long-distance pipeline laying, a large number of pipe joints are required on each hydraulic fluid path to connect the pipelines, resulting in a large number of pipe joints in the hydraulic system and a wide distribution. Pipe joints are important components for pipeline connection. Failure of any pipe joint will cause a major accident in the aircraft hydraulic system. Therefore, the research on the connection accuracy and reliability of pipe joints is crucial to the aircraft hydraulic system.
[0003] The present invention mainly studies the short-term relaxation effect of pipe joints. Short-term stress relaxation refers to the phenomenon that the total deformation (the sum of elastic deformation and plastic deformation) of the force-bearing body remains unchanged, while the stress slowly decreases over time. In this process, the elastic deformation is continuously transformed into plastic deformation. However, the occurrence of short-term relaxation should not be due to its preload exceeding the material's ultimate contact strength, resulting in obvious short-term relaxation. Since pipeline connectors have many internal contact surfaces, there is currently no clear experimental method for measuring the ultimate contact stress in pipeline connectors, nor is there a clear measurement method and determination method. In this regard, it is of great significance to design an experimental device and experimental method for the ultimate contact stress of pipeline connectors, which also provides guidance for improving the precision technology of pipeline connectors. Summary of the invention
[0004] The problem addressed by the present invention is the ultimate contact stress of the material in a pipe connector specimen: in each contact surface of the pipe joint, due to changes in external factors or initial loading, the preload exceeds the material yield limit, the material undergoes plastic deformation, and depressions occur on the contact surface. If the force exceeds the ultimate contact strength of the material, significant stress relaxation will occur, causing a significant decrease in the connection preload, and the connection strength cannot meet the established requirements. In addition, the pipe connector has many internal contact surfaces and cannot be tested directly. In response to the above problems, the present invention provides an experimental device and an experimental method for measuring the ultimate contact stress of connected parts in a pipe joint specimen.
[0005] The technical solution adopted by the present invention is:
[0006] An experimental device for measuring the limit contact stress of a pipeline connector includes a test piece fixture 2, a tension tool 3, a micrometer, a micrometer fixture, and a pipeline connection ball head test piece 4. The experimental device is loaded with force through a tensile machine, and two micrometers are used to accurately measure the change in displacement during the experiment.
[0007] The specimen fixture 2 is a hollow cylindrical structure consisting of an upper and lower surface and a fixture side wall 10; wherein, a fixture upper chuck 8 is provided at the top center of the upper surface, and the fixture upper chuck 8 is clamped on the upper chuck of the stretching machine; a fixture bottom hole 11 is opened at the center of the lower surface, and a ring-shaped tooling 9 is provided at the fixture bottom hole 11, which is 3 mm higher than the lower surface; and two openings are provided on the fixture side wall 10, which pass through from front to back.
[0008] The pipeline connection ball head test piece 4 is placed in the annular fixture 9 of the test piece fixture 2, and the conduit portion thereof passes through the fixture bottom hole 11 of the test piece fixture 2.
[0009] The tension tooling 3 comprises a welding nozzle tooling 12 and a tension shaft tooling 13; wherein, the welding nozzle tooling 12 simulates a real nozzle, and its lower part is an inverted cone-shaped mouth with a through hole inside; the tension shaft tooling 13 is a flange-type smooth rod shaft, and the diameter of the smooth rod shaft is slightly smaller than the through hole of the welding nozzle tooling. The flange face cover of the tension shaft tooling 13 is located on the upper surface of the welding nozzle tooling 12, and its smooth rod shaft passes through the through hole of the welding nozzle tooling 12 and the through hole of the pipeline connection ball head specimen 4 in turn, and then extends 100 to 200 mm outside the bottom hole 11 of the fixture, and keeps the axis lines coincident; when loading, the lower chuck of the stretching machine clamps the smooth rod shaft of the tension shaft tooling 13.
[0010] There are two micrometer fixtures, namely, the upper micrometer fixture 1 and the lower micrometer fixture 7; a magnetic base is provided below the upper and lower micrometer fixtures, and the two are fixed to the upper and lower outer surfaces of the specimen fixture 2 respectively through the magnetic base. The micrometer includes an upper micrometer 5 and a lower micrometer 6, and the upper and lower micrometers are fixed to the chucks of the upper and lower micrometer fixtures respectively. The magnetic base can control the magnetic force through a switch, so as to adjust the position of the chuck of the lower micrometer fixture 7 so that the probe of the lower micrometer 6 is vertically against the expanded part of the pipeline connection ball head specimen 4, and adjust the position of the chuck of the upper micrometer fixture 1 so that the probe of the upper micrometer 5 is vertically against the upper surface of the tension shaft fixture 13 of the tension fixture 3.
[0011] Two micrometers are connected to the computer via data cables and are used to measure the displacement changes of the overall and pipeline connection ball head specimens during the experiment; among them, the upper micrometer 5 collects the changes in indentation depth of all contact surfaces of the overall under pressure, and the lower micrometer 6 collects the changes in indentation depth of the contact surface between the pipeline connection ball head specimen and the annular tooling under pressure.
[0012] An experimental method for measuring the limit contact stress of a pipeline connector using the above experimental device, wherein the loading mode of the experimental method is continuous loading, and the continuous loading is to apply a uniform and continuously increasing tension to the tension shaft tooling 13, and the experiment needs to process the obtained experimental curve graph; the experimental method specifically includes the following steps:
[0013] Step 1: Assemble the experimental setup
[0014] 1.1) Place the pipeline connection ball head specimen 4 into the specimen fixture 2, and the tension shaft fixture 13 of the tension fixture 3 passes through the welding nozzle fixture 12 of the tension fixture 3 and the through hole of the pipeline connection ball head specimen 4 in sequence, and protrude 100 to 200 mm from the bottom hole 11 of the fixture, and ensure that the axes coincide; fix the upper and lower micrometer fixtures on the upper and lower surfaces of the specimen fixture respectively, and fix the upper parts of the upper and lower micrometers on the chucks of the upper and lower micrometer fixtures respectively, and adjust the vertical positions of the chucks of the two micrometer fixtures to make the probes of the two micrometers vertically against the upper surface of the tension shaft fixture and the upper surface of the pipeline connection ball head specimen respectively;
[0015] 1.2) Adjust the distance between the upper and lower chucks of the stretching machine chuck, fix the upper chuck 8 of the fixture on the upper chuck of the stretching machine, and fix the polished shaft of the tension shaft fixture 13 on the lower chuck of the stretching machine;
[0016] 1.3) Connect the stretching machine, micrometer and computer.
[0017] Step 2: Debug the experimental device before use
[0018] 2.1) Fine-tune the lower crossbeam of the stretching machine through the stretching machine controller, and complete the clamping of the lower chuck of the stretching machine chuck and the polished shaft of the tension shaft fixture 13, so that the welding nozzle fixture 12 of the tension fixture is pressed against the pipeline connection ball head test piece 4;
[0019] 2.2) Adjust the positions of the two dial gauge fixture chucks to make the two dial gauges respectively press the tension fixture 3 and the pipeline connection ball head test piece 4 to form a reading of 1mm to 1.5mm, and then reset the two dial gauges to zero.
[0020] Step 3: Conduct continuous loading experiments
[0021] 3.1) Using a computer to control the tensile machine to uniformly load the tensile shaft fixture 13, during the experiment, the upper and lower micrometers read the displacement data of the whole and pipeline connection ball head specimens respectively, and the computer reads the pressure data applied by the tensile machine;
[0022] 3.2) Replace the tension tooling 3 and the pipe connection ball head specimen 4, repeat the above steps 4 to 5 times, and record the experimental results.
[0023] Step 4: Analyze the experimental results after loading, analyze the mechanical properties of the pipe joint, and obtain the limit contact stress of the pipe joint when connected. The limit contact stress of the pipe joint is its maximum bearing capacity in actual assembly and use. Exceeding the limit contact stress will lead to obvious short-term relaxation.
[0024] During the experiment, there are two contact surfaces in the pipeline connection ball joint specimen, one is the contact surface between the ball joint of the pipeline connection ball joint specimen 4 and the welding nozzle fixture 12, and the other is the contact surface between the pipeline connection ball joint specimen 4 and the annular fixture 9. The micrometer 5 measures the overall total displacement, which needs to be converted:
[0025] L 1 =L 总 -L 2 (1)
[0026] Where, L 1 Indicates the change in indentation between the ball head of the pipeline connection specimen and the contact surface of the welding nozzle fixture after being stressed; L 总 Represents the overall displacement change; L 2 It indicates the change of indentation between the contact surface of the pipeline connection ball head specimen and the annular tooling after being subjected to force.
[0027] Compared with the prior art, the present invention has the following beneficial effects:
[0028] (1) Simple experimental preparation stage: The device only has a specimen fixture and a tensile tooling, and the rest are purchased parts. The specimen fixture and tensile tooling have simple structures and are easy to process.
[0029] (2) High experimental measurement accuracy: The reading of the micrometer is intuitive and convenient, the accuracy of the micrometer is 1μm, and the experimental data processing results are more convincing.
[0030] (3) The experimental method is ingenious: This experimental method can measure the displacement of the internal contact surface of the pipeline connector, and can also measure the displacement of multiple contact surfaces at the same time.
[0031] (4) Wide range of applications: In addition to the stress relaxation test of pipeline connectors, this experimental device can also perform yield tests, ultimate contact strength tests, and tensile tests on pipeline connectors, and has a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS
[0032] Figure 1 Schematic diagram of the overall experimental device of the present invention.
[0033] Figure 2 It is a two-dimensional model diagram of the fixture and other experimental parts (excluding the micrometer and the magnetic base of the micrometer); among them, (a) is the main view, (b) is the side view, (c) is the bottom view, and (d) is the axial view.
[0034] Figure 3 It is a two-dimensional model diagram of the specimen fixture; among them, (a) is the main view, (b) is the side view, (c) is the bottom view, and (d) is the axial view.
[0035] Figure 4 This is the three-dimensional model diagram of the tension tooling.
[0036] Figure 5 Schematic diagram of placing the pipe connection ball head specimen into the lower surface of the specimen fixture; wherein (a) is the main view, (b) is the side view, (c) is the top view, and (d) is the axial view.
[0037] In the figure: 1 upper micrometer fixture; 2 test piece fixture; 3 tension tooling; 4 pipe connection ball head test piece; 5 upper micrometer; 6 lower micrometer; 7 lower micrometer fixture; 8 fixture upper chuck; 9 annular tooling; 10 fixture side wall; 11 fixture bottom hole; 12 welding nozzle tooling; 13 tension shaft tooling. Specific implementation plan
[0038] The present invention is further described below in conjunction with the technical scheme and the accompanying drawings.
[0039] According to the experimental device for measuring the short-term relaxation effect of pipeline connectors provided by the present invention, Figure 1 , Figure 2 As shown, it includes a tension tool 3, a micrometer, a micrometer fixture, a pipeline connection ball head specimen 4 and a specimen fixture 2. The material type, shape and size of the pipeline connection ball head specimen used in the experiment are all the same.
[0040] Experimental tooling design: The specimen fixture 2 must meet the strength requirements, and heat treatment must be performed after processing to enhance rigidity. The design dimensions of the specimen fixture 2 are 10mm thick on the upper and lower end faces; the diameter of the chuck 8 on the fixture is 20mm, the height is 55mm, the outer diameter is 140mm, and the height is 120mm; the diameter of the bottom hole 11 of the fixture is 45mm; the diameter of the annular tooling 9 at the bottom of the fixture is 51mm and the height is 3mm. Two micrometers, a pipe connection ball head specimen 4, and a tension tooling 3 are placed in the space inside the specimen fixture 2. There is a magnetic base under the micrometer fixture, which is used to fix the position of the micrometer. The magnetic base is placed on the upper and lower outer surfaces of the specimen fixture 2 respectively. The tensioning tool 3 includes a welding nozzle tool 12 and a tensioning shaft tool 13. The welding nozzle tool 12 must be designed and matched according to the size of the ball-type pipe joint and can cooperate with the ball-type pipe joint during the test; the tensioning shaft tool 13 is a flange-type bare rod shaft composed of a slender shaft and a disc. Since it is subjected to direct tension, its strength must be increased, and the strength is level 10.9.
[0041] Other experimental parts description: During the experiment, the error is within the range of 1μm, so the accuracy of the two micrometers must be sufficient, and both use digital display five-button micrometers. The micrometer has a dedicated data line, and the experimental data is transmitted to the computer for processing during the experiment to accurately obtain the change process of the indentation depth during the experiment; the selection of the micrometer fixture needs to consider the size of the micrometer. Too large or too small will make it difficult to adjust the position of the micrometer.
[0042] The specific implementation process of the experimental method is as follows:
[0043] Preparation stage: According to Figure 1-5 As shown, prepare all the equipment needed for the experiment. Connect the welding nozzle fixture 12, the tension shaft fixture 13, and the pipeline connection ball head specimen 4 in sequence, and then put them into the specimen fixture 2; then clamp the two micrometers on the magnetic base, and fix the two micrometer fixtures on the upper and lower inner surfaces of the specimen fixture respectively; adjust the position of the lower micrometer fixture 7 chuck so that the lower micrometer 6 probe is vertically against the expansion of the pipeline connection ball head specimen, adjust the position of the upper micrometer fixture 1 chuck so that the upper micrometer 5 probe is vertically against the upper surface of the tension fixture, and make the upper and lower micrometer readings between 400μm and 420μm. Connect the tensile machine to the computer, perform online testing, debug the control software of the tensile machine, and enter the sample. Check and adjust the position of the specimen fixture 2 and other experimental pieces, and clamp the specimen fixture 2 on the tensile machine. Check the operability of the micrometer and debug the acquisition program of the micrometer. Finally, check the overall assembly and connection.
[0044] Adjustment before the experiment: Start the stretching machine and computer, open the corresponding control software, operate the stretching machine controller to move the crossbeam of the stretching machine, clamp the lower chuck of the stretching machine chuck to the tension shaft tooling to form a small tension. Reset the two micrometers to make it read 0.
[0045] Conduct a continuous loading experiment: The continuous loading is to apply a uniform and continuously increasing tensile force to the pipe connection ball head specimen until the indentation depth exceeds 500μm. At this time, the material has already exceeded the limit contact pressure and is damaged. The entire process data is recorded and fitted into a stress-deformation curve. The contact pressure corresponding to the plastic indentation depth of 20μm, 100μm, and 200μm is read from this curve. Specifically: start the tensile machine and the micrometer acquisition button, start the computer to perform the tensile experiment, and the moving speed is 0.050mm / min. The micrometer data is fitted into a time-displacement curve, and the tensile machine calculator is fitted into a time-force curve. The continuous loading experiment is carried out 4 to 5 times, and the tensile tooling 3 and the pipe connection ball head specimen 4 are replaced each time.
[0046] Processing experimental data: The data are processed to obtain stress-time curves of the contact surface between the ball head of the pipeline connection ball head specimen 4 and the welding nozzle fixture 12 and the contact surface between the pipeline connection ball head specimen 4 and the annular fixture 9, from which it can be seen when plastic deformation occurs and the limit stress is obtained.
[0047] The above-described embodiments merely express the implementation methods of the present invention, but they cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.
Claims
1. An experimental device for measuring the limit contact stress of pipeline connectors, characterized in that: The experimental device comprises a test piece fixture (2), a tension tool (3), a micrometer, a micrometer fixture and a pipeline connection ball head test piece (4); The specimen fixture (2) is a hollow cylindrical structure consisting of an upper and lower surface and a fixture side wall (10); wherein an upper fixture chuck (8) is provided at the center of the top of the upper surface for clamping on the upper chuck of the stretching machine; a fixture bottom hole (11) is provided at the center of the lower surface, and an annular tooling (9) is provided at the fixture bottom hole (11); and two openings are provided on the fixture side wall (10) that pass through from front to back; The pipeline connection ball head test piece (4) is placed in the annular fixture (9) of the test piece fixture (2), and its conduit portion passes through the fixture bottom hole (11) of the test piece fixture (2); The tension tooling (3) comprises a welding nozzle tooling (12) and a tension shaft tooling (13); wherein the welding nozzle tooling (12) simulates a real nozzle, and its lower part is an inverted cone-shaped mouth, and the interior is a through hole; the tension shaft tooling (13) is a flange-type polished shaft, and its flange surface cover is clamped on the upper surface of the welding nozzle tooling (12), and its polished shaft sequentially passes through the through hole of the welding nozzle tooling (12) and the through hole of the pipeline connection ball head test piece (4), and then extends out of the bottom hole (11) of the fixture, and the axis lines are kept coincident; when loading, the lower chuck of the tensile machine clamps the polished shaft of the tension shaft tooling (13); The micrometer fixture comprises an upper micrometer fixture (1) and a lower micrometer fixture (7); a magnetic base is provided below the upper and lower micrometer fixtures, and the two are respectively fixed to the upper and lower outer surfaces of the specimen fixture (2) through the magnetic base; the micrometer comprises an upper micrometer fixture (5) and a lower micrometer fixture (6), and the upper and lower micrometer fixtures are respectively fixed to the clamps of the upper and lower micrometer fixtures; the magnetic base controls the magnetic force through a switch, thereby adjusting the position of the clamp of the lower micrometer fixture (7) so that the probe of the lower micrometer fixture (6) is vertically pressed against the expanded part of the pipeline connection ball head specimen (4), and adjusting the position of the clamp of the upper micrometer fixture (1) so that the probe of the upper micrometer fixture (5) is vertically pressed against the upper surface of the tension shaft fixture (13); Both micrometers are connected to a computer, wherein the upper micrometer (5) collects the change in indentation depth of all contact surfaces under pressure, and the lower micrometer (6) collects the change in indentation depth of the contact surface between the pipeline connection ball head specimen and the annular tooling under pressure.
2. The experimental device for measuring the limit contact stress of pipeline connectors according to claim 1, characterized in that: The annular tooling (9) is a simulated outer sleeve nut, and its length above the lower surface of the specimen fixture is 3 mm.
3. An experimental device for measuring the limit contact stress of pipeline connectors according to claim 1 or 2, characterized in that: The polished shaft of the tension shaft fixture (13) extends out of the bottom hole (11) of the fixture by 100 to 200 mm.
4. An experimental method for measuring the limit contact stress of a pipeline connector using the experimental device as described in any one of claims 1 to 3, characterized in that: The experimental method includes the following steps: Step 1: Assemble the experimental setup 1.1) Place the pipe connection ball head specimen (4) into the specimen fixture (2), and the tension shaft fixture (13) of the tension fixture sequentially passes through the welding nozzle fixture (12) of the tension fixture and the through hole of the pipe connection ball head specimen (4) and extends 100 to 200 mm from the bottom hole (11) of the fixture, and ensure that the axes coincide; fix the upper and lower micrometer fixtures on the upper and lower surfaces of the specimen fixture respectively, and fix the upper parts of the upper and lower micrometer fixtures on the clamps of the upper and lower micrometer fixtures respectively, and adjust the vertical positions of the clamps of the two micrometer fixtures so that the probe of the lower micrometer (6) is vertically against the upper surface of the pipe connection ball head specimen and the probe of the upper micrometer (5) is vertically against the upper surface of the tension fixture; 1.2) Adjust the distance between the upper and lower chucks of the stretching machine chuck, fix the upper chuck (8) of the fixture to the upper chuck of the stretching machine, and fix the polished shaft of the tension shaft fixture (13) to the lower chuck of the stretching machine; 1.3) Connect the stretching machine, dial gauge and computer; Step 2: Debug the experimental device before use 2.1) The lower crossbeam of the stretching machine is fine-tuned through the stretching machine controller, and the lower clamp of the stretching machine chuck and the polished shaft of the tension shaft fixture (13) are clamped, so that the welding nozzle fixture (12) of the tension fixture is pressed against the pipeline connection ball head test piece (4); 2.2) Adjust the positions of the two dial gauge fixture chucks so that the two dial gauges respectively press the tension fixture (3) and the pipeline connection ball head test piece (4) to form a reading of 1 mm to 1.5 mm, and then reset the two dial gauges to zero; Step 3: Conduct continuous loading experiments The tensile machine is controlled by a computer to uniformly load the tensile shaft fixture (13). During the experiment, the upper and lower micrometers read the displacement data of the whole and the pipeline connection ball head test piece respectively, and the computer reads the pressure data applied by the tensile machine. When the micrometer reading reaches 400 μm to 420 μm, the experiment is stopped, the whole process data is recorded, and the stress-displacement curve is fitted. Step 4: Analyze the experimental results after loading, analyze the mechanical properties of the material, and obtain the limit contact stress of the pipe joint under the connection condition.
5. The experimental method according to claim 4, characterized in that: After each continuous loading test is completed, the pipeline connection ball head test piece (4) and the tension tooling (3) are replaced, and the loading test is repeated 4 to 5 times.
6. The experimental method according to claim 4 or 5, characterized in that: Subtract the readings of the upper and lower dial indicators: L1=L 总 -L2 (1) Where, L1 represents the change in indentation between the ball head of the pipeline connection specimen and the contact surface of the welding nozzle fixture after being subjected to force; L 总 Indicates the overall displacement change; L2 indicates the indentation change between the contact surface of the pipeline connection ball head specimen and the annular tooling after force is applied.