Four-point bending test device for full-size large-diameter pipeline

Abstract

The utility model discloses a four-point bending test device for a full-size large-diameter pipeline. The four-point bending test device comprises a supporting unit and a loading unit, the loading unit comprises an oil cylinder fixing end, an oil cylinder is arranged at the lower end of the oil cylinder fixing end, a load distribution beam is arranged at the output end of the oil cylinder, and upper clamps are hinged to the lower ends of the two sides of the load distribution beam; the supporting unit comprises a base, two supporting parts are arranged on the base, lower clamps used in cooperation with the upper clamps are arranged at the upper ends of the supporting parts in a hinged mode, and the upper clamps are located between the two lower clamps. The device has the advantages of being stable in loading, free of influence of concentrated force on the pipeline, capable of improving test result analysis, simple in structure, low in manufacturing cost, not prone to damage, convenient to operate and the like.

Description

Technical Field

[0001] The utility model relates to a testing device, in particular to a four-point bending testing device for a full-size large-diameter pipeline. Background Art

[0002] High pressure, large transmission volume and long-distance transmission have become the development trend of natural gas pipeline transportation in my country. Increasing the pipe diameter is one of the effective ways to increase the pipeline natural gas transmission volume and reduce the transmission cost. At present, the China-Russia East Line has adopted a pipeline with a diameter of 1422mm, a wall thickness of 30.8mm, X80 steel and a design pressure of 12MPa. However, the weldability of high-grade steel is very poor. If the preheating process before welding and the insulation process after welding are not in place, various weld defects will be induced in the pipeline. Among them, circumferential cracks are a relatively common defect. Existing studies have shown that crack defects are the main cause of plastic failure pressure or pipeline rupture. High-grade steel (X70, X80) and large-diameter (Ф1016mm, Ф1219mm) pipelines represented by the West-East Gas Pipeline II and the China-Myanmar Pipeline have experienced more than 30 weld cracking and leakage accidents during the initial pressure test and commissioning of the pipeline. It is urgent to carry out research on how to improve the strain capacity of oil and gas pipeline welding joints.

[0003] The strain capacity of pipeline welded joints is an important factor affecting the safe operation of pipelines. Due to the actual constraints of real pipelines and the complex load forms, and the differences between some small-sized specimens used in existing tests of material fracture toughness, such as SENB and SENT, and large-sized wide plate tests, these small-sized test results are difficult to characterize the strain capacity of real pipelines. At the same time, due to the high cost of full-scale tests, there is no corresponding full-scale test on the strain capacity of pipeline welded joints in China. At present, numerical simulation methods are more often used to carry out relevant research. However, due to the lack of relevant experimental verification, the existing research results on the strain capacity of pipeline welded joints are difficult to be effectively promoted.

[0004] The above-mentioned problems have attracted attention in the engineering community at home and abroad. Judging from the current research results, the proposed full-scale bending loading scheme for pipelines includes: 1. Using the two-point bending method to test the critical curvature radius of the bending deformation of the specimen, and then characterize the bending strength of the specimen. The specimen is clamped between two baffles. When the baffles move inward at the same speed, they produce a squeezing effect on the specimen. As the inward displacement of the baffle increases, the specimen bends and deforms, and at the same time, the cracks on the surface of the specimen gradually expand, and eventually the function reaches the limit state and fracture occurs; 2. Using a full-scale three-point bending test machine, place the steel pipe on two support points with a certain distance between them, and the hydraulic cylinder applies a load to the specimen from the center of the two support points. Such a force structure causes the two support points of the specimen to form two almost equal moments. This moment structure will cause three-point bending until the specimen breaks at the center.

[0005] The limitations of the two methods mentioned above are: 1. The two-point bending test method is often used to measure the bending strength of small specimens and thin plates. For full-size pipes, the test equipment needs to be large in size and provide a large extrusion load to compress and bend the pipe; 2. The three-point bending test has a simple loading method, but due to the concentrated loading method and uneven bending distribution, the compressed position may be subject to additional bending moment, which has a greater impact on the test results.

[0006] Therefore, those skilled in the art are committed to providing a full-size large-diameter pipe four-point bending test device that can effectively solve the above-mentioned technical problems. Utility Model Content

[0007] In view of the above-mentioned defects in the prior art, the technical problem to be solved by the utility model is to provide a full-size large-diameter pipe four-point bending test device which can effectively solve the above-mentioned technical problems.

[0008] To achieve the above-mentioned purpose, the utility model provides a full-size large-diameter pipeline four-point bending test device, comprising a support unit and a loading unit;

[0009] The loading unit comprises a cylinder fixed end, a cylinder is arranged at the lower end of the cylinder fixed end, a load distribution beam is arranged at the output end of the cylinder, and upper clamps are hingedly arranged at the lower ends of both sides of the load distribution beam;

[0010] The support unit comprises a base, on which two supporting parts are arranged, and the upper end of each supporting part is hingedly provided with a lower clamp used in conjunction with each upper clamp, and each upper clamp is located between the two lower clamps.

[0011] Preferably, the fixed end of the oil cylinder is a positioning frame or a wall.

[0012] Preferably, an upper connecting piece is provided at the output end of the oil cylinder, and the upper half of the middle section of the load distribution beam is clamped by the upper connecting piece and is detachably connected to the upper connecting piece.

[0013] Preferably, adjustable pressure head supports are provided at the lower ends of both sides of the load distribution beam, and the lower end of each adjustable pressure head support is hinged to the upper end of each upper clamp.

[0014] Preferably, an adjustment support is provided at the lower half of the support portion, a slide rail is provided on the base, the adjustment support is slidably connected to the base via the slide rail, and is detachably positioned with the base via screws.

[0015] Preferably, the lower half of the support portion is provided with an adjustment support, the adjustment support is slidably connected to the base and is detachably positioned with the base by screws.

[0016] Preferably, the upper half of the support portion and the lower half of the upper connecting member are both provided with pin holes, and each of the pin holes is provided with a pin.

[0017] Preferably, a stepped hole for being penetrated by a bolt is formed on the top of the upper connecting member, the number of the stepped holes is the same as the number of the oil cylinders, and the upper connecting member is fixed to the loading end of the piston of the hydraulic oil cylinder by bolts.

[0018] The beneficial effects of the utility model are as follows:

[0019] 1. For the first time, a four-point bending test device suitable for full-size pipes with diameters of 1422 and X80 was established;

[0020] 2. Compared with the traditional bending test, the support unit of the device of the present application is connected by pins. The load applied during the loading process does not act directly on the pins, but on the support part. The support part is laterally provided with supports to balance the horizontal component of the load and ensure the safety of the structure;

[0021] 3. The four-point bending is formed by the cooperation of two upper clamps and two lower clamps. The four-point bending loading in the utility model is more stable, which can avoid the influence of concentrated force on the pipeline. Compared with the three-point bending, it can also reduce the load and displacement required by the cylinder piston rod. During the test, the welded joints are subjected to pure bending moment and are all in the maximum bending moment area of ​​the system, which is conducive to the analysis of the test results. It also has the beneficial effects of simple structure, low manufacturing cost, not easy to damage and easy operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a structural schematic diagram of a specific implementation method of the utility model.

[0023] Figure 2 It is a structural schematic diagram of the lower clamp and other components in the utility model.

[0024] Figure 3 The utility model is a structural schematic diagram of a load distribution beam in which pin holes are provided.

[0025] Figure 4 It is a top view structural schematic diagram of a base provided with a slide rail in the utility model. DETAILED DESCRIPTION

[0026] The utility model is further described below in conjunction with the accompanying drawings and embodiments:

[0027] In the description of the present invention, it should be noted that the terms "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0028] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "setting", and "connection" should be understood in a broad sense, for example, it 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 it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0029] At present, there is no four-point bending test for large-diameter full-size pipes at home and abroad, and there is no test device that can meet the above test conditions. The purpose of this utility model is to propose a device and method suitable for full-size large-diameter pipe welding joint testing, which provides strong technical support for four-point bending tests for full-size pipes with diameters of 1422 and X80.

[0030] like Figures 1 to 4 As shown, a full-size large-diameter pipe four-point bending test device includes a support unit and a loading unit;

[0031] The loading unit includes a cylinder fixed end 13, a cylinder 22 is provided at the lower end of the cylinder fixed end 13, a load distribution beam 3 is provided at the output end of the cylinder 22, and upper clamps 5 are hingedly provided at the lower ends of both sides of the load distribution beam 3; in the utility model, the loading force required for the test is provided by the cylinder 22, and the cylinder design specification refers to the enterprise standard QB / HC00-2013 "Hydraulic Cylinder Design Calculation", and the cylinder stroke is based on the national standard GB / T2349.80 "Hydraulic and Pneumatic Systems and Components-Cylinder Stroke Series".

[0032] The cylinder loading force is transmitted to the loading beam (i.e., load distribution beam 3) through the cylinder. The loading beam is designed to be a rigid component to reduce deformation. The purpose of this design is to be compatible with cylinders of different specifications. At the same time, the device does not need to control the constant loading rate and loading force of the cylinder, and does not need to provide an oil pressure control system to control the two cylinders to move in unison.

[0033] The support unit includes a base 4 , on which two support parts 2 are arranged. The upper end of each support part 2 is hingedly provided with a lower clamp 66 used in conjunction with each upper clamp 5 , and each upper clamp 5 is located between the two lower clamps 66 .

[0034] The oil cylinder fixed end 13 is a positioning frame or a wall.

[0035] An upper connecting piece 12 is disposed at the output end of the oil cylinder 22 , and the upper half of the middle section of the load distribution beam 3 is clamped by the upper connecting piece 12 and is detachably connected to the upper connecting piece 12 .

[0036] Adjustable pressure head supports 9 are provided at the lower ends of both sides of the load distribution beam 3 , and the lower ends of the adjustable pressure head supports 9 are hinged to the upper ends of the upper clamps 5 .

[0037] A plurality of positioning screw holes 33 are provided at the lower end of the load distribution beam 3 , and each of the positioning screw holes 33 is arranged along the length direction of the load distribution beam 3 . Each of the adjustable pressure head supports 9 is detachably connected to the load distribution beam 3 via a plurality of positioning screws 77 .

[0038] The lower half of the support portion 2 is provided with an adjustment support 7, and the base 4 is provided with a slide rail 8. The adjustment support 7 is slidably connected to the base 4 through the slide rail 8, and is detachably positioned with the base 4 through screws. When in use, the base 4 is fixed on the solid ground of the laboratory. As a further preferred embodiment, a slide rail is provided on the base 4, and the adjustment support 7 is slidably adjusted with the base 4 through the slide rail.

[0039] The full-size pipeline four-point bending test platform is to place the pipeline 99 test piece on two support points (i.e., two lower fixtures 66) at a certain distance, and apply a downward load to the pipeline 99 at the same distance from the midpoint of the two support points through the cylinder 22. The sample (i.e., the pipeline 99) undergoes four-point bending (such as Figure 1 As shown in the figure, the bending radius at the midpoint is the largest. The bending moment of the four-point bending test is evenly distributed, which effectively improves the accuracy of the test results. Before the actual test, the distance between the two adjustable pressure head supports 9 can be adjusted according to actual needs, and the distance between the two support parts 2 can also be adjusted.

[0040] In addition, in order to prevent the influence of stress concentration and loading shear force, the total length of the sample tube should be no less than 8 times the pipe diameter - that is, the inner diameter of the pipe in the test is much smaller than the length of the specimen pipe, so the specimen pipe section can be assumed to be a beam model under four-point bending stress.

[0041] The pipe 99 is placed on two lower clamps 66. In the utility model, the structures of the lower clamps 66 and the upper clamps are both semicircular rings, which can provide lateral support for the pipe 99 to prevent the pipe 99 from excessive lateral movement. The hinge structure can be used to make the semicircular ring rotate longitudinally as the bending angle of the pipe changes during loading, so that the pipe and the semicircular ring surface are in contact, ensuring that the pipe and the semicircular ring have sufficient contact area. In this way, under the condition of a certain loading load, the contact force between the pipe and the semicircular ring becomes smaller, so that the pipe will not be flattened. The width of the semicircular ring is proportionally converted according to the size of the test bench of the University of Alberta.

[0042] At the same time, the structure adopts pin connection, and the load applied during the loading process does not act directly on the pin, but on the support column, and the support column is provided with a support laterally to balance the horizontal component of the load, thereby ensuring the safety of the structure. The upper half of the support portion 2 and the lower half of the upper connecting member 12 are both provided with pin holes 15, and each of the pin holes 15 is provided with a pin.

[0043] The load is transferred to the specimen through the load distribution beam (F / 2), and the upper connecting member 12 is acted on by the oil cylinder. The top of the upper connecting member 12 is provided with stepped holes for being penetrated by bolts. The number of the stepped holes is the same as the number of the oil cylinder 22. The loading end of the piston of the hydraulic cylinder is fixed by bolts. The upper connecting member 12 is connected to the load distribution beam 3 by a pin, and the pin is not subjected to force.

[0044] The loading head is connected to the load distribution beam 3 through a threaded hole to adjust the span. The upper clamp 5 and the lower clamp 66 are arranged movably to ensure that the clamp and the test piece are in contact with each other, and a uniform surface load can be applied to the test piece - the pipe is bent but not flattened.

[0045] The utility model also includes the following technical points:

[0046] 1) For the first time, a device and method suitable for full-size large-diameter pipeline welding joint testing was established, providing strong technical support for the four-point bending test of full-size pipelines with diameters of 1422 and X80.

[0047] 2) The hinge structure can make the semicircular ring rotate longitudinally as the bending angle of the pipe changes during loading, so that the pipe and the supporting semicircular ring are in contact with each other, ensuring that the pipe and the semicircular ring have sufficient contact area. In this way, under the condition of a certain loading load, the contact force between the pipe and the semicircular ring becomes smaller, so that the pipe will not be flattened.

[0048] 3) The supporting structure is connected by pins. The load applied during the loading process does not act directly on the pins, but on the supporting columns. The supporting columns are supported laterally to balance the horizontal component of the load and ensure the safety of the structure.

[0049] 4) The loading beam is designed as a rigid component to reduce deformation. The purpose of this design is to match different specifications of oil cylinders. At the same time, the device does not need to control the constant loading rate and loading force of the oil cylinder, and does not need to provide an oil pressure control system to control the two oil cylinders to move in unison. The loading pressure head is connected to the load distribution beam through a threaded hole to achieve the function of adjusting the span. Compared with the traditional bending test, the utility model can be applied to full-size large-diameter pipelines.

[0050] The preferred specific embodiments of the utility model are described in detail above. It should be understood that ordinary technicians in this field can make many modifications and changes based on the concept of the utility model without creative work. Therefore, all technical solutions that can be obtained by technicians in this technical field based on the concept of the utility model through logical analysis, reasoning or limited experiments on the basis of the existing technology should be within the scope of protection determined by the claims.

Claims

1. A full-size large-diameter pipe four-point bending test device, characterized by: It includes a supporting unit and a loading unit; The loading unit comprises a cylinder fixed end (13), a cylinder (22) is arranged at the lower end of the cylinder fixed end (13), a load distribution beam (3) is arranged at the output end of the cylinder (22), and upper clamps (5) are hingedly arranged at the lower ends of both sides of the load distribution beam (3); The support unit comprises a base (4), on which two supporting parts (2) are arranged, and the upper end of each supporting part (2) is hingedly provided with a lower clamp (66) for use with each upper clamp (5), and each upper clamp (5) is located between the two lower clamps (66).

2. The full-size large-diameter pipe four-point bending test device according to claim 1, characterized in that: The oil cylinder fixed end (13) is a positioning frame or a wall.

3. The full-size large-diameter pipe four-point bending test device according to claim 2, characterized in that: An upper connecting piece (12) is provided at the output end of the oil cylinder (22), and the upper middle half of the load distribution beam (3) is clamped by the upper connecting piece (12) and is detachably connected to the upper connecting piece (12).

4. The full-size large-diameter pipe four-point bending test device as claimed in claim 3 is characterized by: Adjustable pressure head supports (9) are provided at the lower ends of both sides of the load distribution beam (3), and the lower ends of the adjustable pressure head supports (9) are respectively hinged to the upper ends of the upper clamps (5).

5. The full-size large-diameter pipe four-point bending test device according to claim 4, characterized in that: A plurality of positioning screw holes (33) are provided at the lower end of the load distribution beam (3), and each of the positioning screw holes (33) is arranged along the length direction of the load distribution beam (3). Each of the adjustable pressure head supports (9) is detachably connected to the load distribution beam (3) via a plurality of positioning screws (77).

6. The full-size large-diameter pipe four-point bending test device according to claim 5, characterized in that: The lower half of the support portion (2) is provided with an adjustment support (7), and the base (4) is provided with a slide rail (8). The adjustment support (7) is slidably connected to the base (4) via the slide rail (8) and is detachably positioned with the base (4) via screws.

7. The full-size large-diameter pipe four-point bending test device according to claim 6, characterized in that: The upper half of the support portion (2) and the lower half of the upper connecting member (12) are both provided with pin holes (15), and each of the pin holes (15) is provided with a pin.

8. The full-size large-diameter pipe four-point bending test device according to claim 7, characterized in that: The top of the upper connecting member (12) is provided with a stepped hole for being penetrated by a bolt, the number of the stepped holes being the same as the number of the oil cylinder (22), and the upper connecting member (12) is fixed to the loading end of the piston of the hydraulic oil cylinder by means of bolts.

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