A method for testing a large-diameter bimetallic composite pipe under tensile and bending combined load

Abstract

The present application relates to the field of bimetallic composite pipe load test, especially to a large-diameter bimetallic composite pipe tensile and bending combined load test method. The large-diameter bimetallic composite pipe tensile and bending combined load test method is to use a tensile and bending testing machine to provide internal support for the large-diameter bimetallic composite pipe to respectively perform tensile test and bending test. The testing machine is provided with vertical hydraulic tension machine and horizontal hydraulic tension machine, and the upper mechanical clamp and the lower mechanical clamp are used to clamp the two ends of the bimetallic composite pipe, and the upper internal support rod and the lower internal support rod are used to provide internal support for the bimetallic composite pipe to avoid large-area collapse phenomenon and effectively measure the tensile or bending test limit value of the bimetallic composite pipe. The technical defects that the bimetallic composite pipe cannot obtain the test limit value due to the lack of internal support in the actual working condition and the large-area collapse phenomenon when subjected to tension are overcome.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of bimetallic composite pipe load test, in particular to a large-diameter bimetallic composite pipe tensile and bending combined load test method. BACKGROUND

[0002] The large-diameter bimetallic composite pipe is a new type of pipe material which combines a metal with good corrosion resistance and a high-strength metal. This composite structure not only retains the advantages of the two materials, but also improves the overall performance of the pipe, making it have a wide application prospect in the fields of marine engineering and oil transportation. Tensile test and bending test are important methods for evaluating the mechanical properties of materials. For large-diameter bimetallic composite pipes, tensile test is mainly used to determine the tensile strength, yield strength and ductility of the base pipe and the overlaying layer, and the purpose of bending test is to determine the bending performance of the material. However, when existing equipment tests bimetallic composite pipes, there is a large area of collapse when the pipes are subjected to tension or bending due to the lack of internal support inside the pipes. Therefore, it is not possible to simulate the test when the bimetallic composite pipe is filled with internal support under real application conditions, and thus the test limit value of the bimetallic composite pipe cannot be obtained. SUMMARY

[0003] In order to overcome the shortcomings of the bimetallic composite pipe lacking internal support in real application conditions, resulting in a large area of collapse when subjected to tension or bending and failing to obtain the test limit value, the present application provides a large-diameter bimetallic composite pipe tensile and bending combined load test method.

[0004] The technical scheme is as follows: a large-diameter bimetallic composite pipe tensile and bending combined load test method, which uses a tensile and bending testing machine to perform tensile test and bending test on the large-diameter bimetallic composite pipe. In the tensile test, internal support is used to avoid collapse, thereby accurately determining the tensile test limit value. A tensile and bending testing machine includes a test table, a vertical hydraulic tension machine, a horizontal hydraulic tension machine, an upper fixed block, an upper mechanical clamp, an inner lining block, an upper internal support rod, a lower fixed block, a lower mechanical clamp, a sleeve, and a lower internal support rod. The test table is connected with the vertical hydraulic tension machine which applies upward tensile load. The vertical lifting part of the vertical hydraulic tension machine is connected with the horizontal hydraulic tension machine which applies horizontal bending load. The horizontal moving part of the horizontal hydraulic tension machine is connected with the upper fixed block. The upper fixed block is connected with the upper mechanical clamp. The inner lining block is fixedly connected in the upper fixed block. The upper internal support rod is connected in the inner lining block to provide upper internal support. The upper internal support rod penetrates downward through the upper mechanical clamp. The test table is connected with the lower fixed block. The lower fixed block is connected with the lower mechanical clamp. The lower fixed block is connected with the sleeve. The sleeve is connected with the lower internal support rod to provide lower internal support. The lower internal support rod penetrates upward through the lower mechanical clamp.

[0005] As a further preferred option, the outer surface of the upper inner support rod is provided with an adjusting thread structure; the upper inner support rod is screwed onto the inner liner block through the adjusting thread structure.

[0006] As a further preferred option, the sleeve is slidably connected to the lower fixing block; an adjusting screw is rotatably connected inside the test bench; the adjusting screw is screwed onto the sleeve; and an adjusting motor that drives the adjusting screw to rotate is installed on the fixing plate inside the test bench.

[0007] As a further preferred embodiment, the upper inner support rod has a hollow cavity structure; the upper inner support rod has a liquid inlet pipe structure that connects to the hollow cavity structure; the lower inner support rod has several drainage threads on its outer surface; the sleeve has a liquid collection groove structure that connects to the drainage threads; the sleeve has a vertical channel structure that connects to the liquid collection groove structure; and a collection pipe is inserted into the vertical channel structure of the sleeve.

[0008] As a further preferred option, a sealing ring is fixedly connected inside the lower mechanical clamp to seal the lower end of the bimetallic composite pipe.

[0009] As a further preferred option, a suction pump is installed on the mounting plate connected to the regulating motor; the inlet end of the suction pump is connected to the lower outlet end of the collection pipe.

[0010] As a further preferred option, the upper end of the lower inner strut is provided with a sealing protrusion structure that is compatible with the hollow cavity structure of the upper inner strut.

[0011] As a further preferred option, the upper inner support rod is provided with several liquid outlet holes that connect to the hollow cavity structure.

[0012] As a further preferred option, the outer surface of the upper inner support rod is provided with a guide thread structure corresponding to the number of liquid outlet hole structures, and the guide thread structure is connected to the corresponding liquid outlet hole structure.

[0013] As a further preferred option, a temperature sensor for testing the temperature of the bimetallic composite tube is installed inside the lower mechanical clamp.

[0014] Beneficial effects: the large-diameter bimetal composite pipe tensile and bending composite load test method of the application is to use a tensile and bending testing machine to provide internal support for large-diameter bimetal composite pipe to carry out tensile test and bending test respectively, the tensile and bending testing machine provided by the application is provided with a vertical hydraulic tension machine and a horizontal hydraulic tension machine, the two ends of the bimetal composite pipe are clamped by the upper mechanical clamp and the lower mechanical clamp respectively, in the tensile test, the upper inner support rod cooperates with the lower inner support rod to provide complete internal support for the bimetal composite pipe, so as to avoid large-area tensile collapse phenomenon and accurately obtain the tensile test limit value of the bimetal composite pipe, in the bending test, the upper inner support rod cooperates with the lower inner support rod to provide internal support with cavity for the bimetal composite pipe, the cavity is aligned with the bending area of the bimetal composite pipe, so as to avoid large-area bending collapse phenomenon and effectively measure the bending test limit value of the bimetal composite pipe; the technical defects that the bimetal composite pipe cannot obtain the test limit value due to the lack of internal support in the actual working condition and the existence of large-area collapse phenomenon when subjected to tensile or bending are overcome. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 It is a perspective view of a tensile and bending testing machine of the application;

[0016] Figure 2 It is a perspective view of a vertical hydraulic tension machine and a horizontal hydraulic tension machine of a tensile and bending testing machine of the application;

[0017] Figure 3 It is a perspective view of an upper inner support rod of a tensile and bending testing machine of the application;

[0018] Figure 4 It is a perspective view of a lower fixed block of a tensile and bending testing machine of the application;

[0019] Figure 5 It is a perspective view of a lower mechanical clamp of a tensile and bending testing machine of the application;

[0020] Figure 6 It is a sectional perspective view of a lower fixed block of a tensile and bending testing machine of the application;

[0021] Figure 7 It is a partial sectional perspective view of a sleeve of a tensile and bending testing machine of the application;

[0022] Figure 8 It is a partial perspective view of a height-adjusting screw rod of a tensile and bending testing machine of the application.

[0023] Reference numerals: 1-Test stand, 21-Vertical hydraulic tensile testing machine, 22-Horizontal hydraulic tensile testing machine, 31-Upper fixing block, 32-Upper mechanical clamp, 33-Inner liner block, 34-Upper inner support rod, 3401-Adjusting thread structure, 3402-Hollow cavity structure, 3403-Inlet pipe structure, 3404-Outlet hole structure, 3405-Guiding thread structure, 41-Lower fixing block, 42-Lower mechanical clamp, 43-Sleeve, 4301-Collection tank structure, 4302-Vertical channel structure, 44-Height adjusting screw, 45-Adjusting motor, 46-Lower inner support rod, 4601-Drainage thread structure, 4602-Sealing protrusion structure, 47-Collection pipe, 48-Sealing ring, 49-Suction pump, 5-Temperature sensor. Detailed Implementation

[0024] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0025] Example 1: A method for testing the combined tensile and bending loads of a large-diameter bimetallic composite pipe in this example involves using a tensile and bending testing machine to provide internal support for conducting tensile and bending tests on the large-diameter bimetallic composite pipe.

[0026] like Figures 1-8 As shown, a tensile and bending testing machine of this embodiment includes a test bench 1, a vertical hydraulic tensile machine 21, a horizontal hydraulic tensile machine 22, an upper fixing block 31, an upper mechanical clamp 32, an inner liner block 33, an upper inner support rod 34, a lower fixing block 41, a lower mechanical clamp 42, a sleeve 43, and a lower inner support rod 46. The vertical hydraulic tensile machine 21 is connected inside the test bench 1, and the vertical hydraulic tensile machine 21 can apply an upward tensile load to the bimetallic composite tube. The vertical lifting component of the vertical hydraulic tensile machine 21 is connected to the horizontal hydraulic tensile machine 22, and the horizontal hydraulic tensile machine 22 can apply a horizontal bending load to the bimetallic composite tube. The horizontal moving component of the horizontal hydraulic tensile machine 22 is connected to the upper... The upper fixing block 31 is connected to an upper mechanical clamp 32; an inner liner block 33 is fixed inside the upper fixing block 31; an upper inner support rod 34 is connected inside the inner liner block 33; the upper inner support rod 34 passes downward through the upper mechanical clamp 32; a lower fixing block 41 is connected inside the test bench 1; a lower mechanical clamp 42 is connected to the lower fixing block 41; a sleeve 43 is connected inside the lower fixing block 41; a lower inner support rod 46 is connected inside the sleeve 43; the lower inner support rod 46 passes upward through the lower mechanical clamp 42; the upper mechanical clamp 32 and the lower mechanical clamp 42 respectively clamp the two ends of the bimetallic composite tube; the upper inner support rod 34 and the lower inner support rod 46 together provide internal support for the bimetallic composite tube.

[0027] like Figure 3As shown, the upper inner support rod 34 is provided with an adjusting threaded structure 3401 on the outer surface; the upper inner support rod 34 is screwed with the inner lining block 33 through the adjusting threaded structure 3401; the operator manually rotates the upper inner support rod 34 to drive it to move along the inner lining block 33 in the upward and downward directions, so as to realize the manual adjustment of the extension length of the upper inner support rod 34.

[0028] As shown, Figures 6-8 the sleeve 43 is slidingly connected with the lower fixed block 41; the test bench 1 is rotatably connected with a height-adjusting screw rod 44; the height-adjusting screw rod 44 is screwed with the sleeve 43; a fixed plate in the test bench 1 is provided with an adjusting motor 45; the output shaft of the adjusting motor 45 is fixedly connected with the height-adjusting screw rod 44; the adjusting motor 45 drives the height-adjusting screw rod 44 to rotate, and at the same time, the height-adjusting screw rod 44 drives the sleeve 43 to move along the lower fixed block 41 in the upward and downward directions, so as to realize the adjustment work of the sleeve 43 driving the lower inner support rod 46 to extend from the lower mechanical clamp 42.

[0029] The tensile test method of the tensile and bending testing machine of the embodiment is as follows.

[0030] First, the operator controls the vertical hydraulic tension machine 21 to drive the upper fixed block 31 and the upper mechanical clamp 32 connected with the horizontal hydraulic tension machine 22 to move downward, clamps the upper end and the lower end of the bimetallic composite pipe between the upper mechanical clamp 32 and the lower mechanical clamp 42 respectively, and inserts the upper inner support rod 34 into the upper side of the bimetallic composite pipe and the lower fixed block 41 into the lower side of the bimetallic composite pipe, then the adjusting motor 45 drives the height-adjusting screw rod 44 to rotate, the height-adjusting screw rod 44 drives the sleeve 43 and the lower inner support rod 46 connected with the sleeve 43 to move upward, so that the upper end of the lower inner support rod 46 tightly abuts against the upper inner support rod 34, so that the upper inner support rod 34 and the lower inner support rod 46 jointly provide complete inner support to the bimetallic composite pipe, then the vertical hydraulic tension machine 21 pulls the upper mechanical clamp 32 to apply an upward tensile load to the bimetallic composite pipe, and at the same time, the upper inner support rod 34 and the lower inner support rod 46 jointly provide inner support to the bimetallic composite pipe, so as to avoid the large-area tensile collapse of the bimetallic composite pipe during the tensile process, so that each tensile area of the bimetallic composite pipe maintains a complete tubular structure for tensile test, and the tensile test limit value of the bimetallic composite pipe is effectively measured.

[0031] The bending test method of the tensile and bending testing machine of the embodiment is as follows.

[0032] First, the operator adjusts the length of the upper inner support rod 34 from the upper mechanical clamp 32, and then controls the vertical hydraulic tensioner 21 to drive the upper fixed block 31 and the upper mechanical clamp 32 connected by the horizontal hydraulic tensioner 22 to move downward, so that the upper end and the lower end of the bimetallic composite pipe are clamped between the upper mechanical clamp 32 and the lower mechanical clamp 42, and the upper inner support rod 34 is inserted into the upper side of the bimetallic composite pipe, and the lower fixed block 41 is inserted into the lower side of the bimetallic composite pipe. Then, adjust the motor 45 to drive the height adjustment screw rod 44 to rotate, and the height adjustment screw rod 44 drives the sleeve 43 and the lower inner support rod 46 connected thereto to move upward, so that the upper end of the lower inner support rod 46 moves upward to approach the upper inner support rod 34, but the lower inner support rod 46 does not tightly adhere to the upper inner support rod 34, so that the lower inner support rod 46 and the upper inner support rod 34 have a short distance cavity structure inside the bimetallic composite pipe, and the cavity structure is aligned with the area of the bimetallic composite pipe to be tested for bending. In this way, the upper inner support rod 34 and the lower inner support rod 46 jointly provide internal support for the area of the bimetallic composite pipe that does not need to be tested for bending, and then the horizontal hydraulic tensioner 22 drives the upper fixed block 31 to drive the upper mechanical clamp 32 to apply a bending load to the right of the bimetallic composite pipe. At this time, the upper inner support rod 34 and the lower inner support rod 46 jointly provide internal support for the area of the bimetallic composite pipe that does not need to be tested for bending, and only allow the area of the bimetallic composite pipe to be tested for bending to appear bending deformation under the action of the bending load to the right, so as to avoid the phenomenon of large area bending collapse of the bimetallic composite pipe during bending, and effectively measure the bending test limit value of the bimetallic composite pipe.

[0033] The tensile and bending composite test method of the tensile and bending testing machine of the present embodiment is as follows.

[0034] First, the operator adjusts the length of the upper inner support rod 34 extending from the upper mechanical clamp 32. Then, the operator controls the vertical hydraulic tensioning machine 21 to move the upper fixing block 31 and the upper mechanical clamp 32 connected to the horizontal hydraulic tensioning machine 22 downwards, clamping the upper and lower ends of the bimetallic composite tube between the upper mechanical clamp 32 and the lower mechanical clamp 42 respectively. The upper inner support rod 34 is inserted into the upper part of the bimetallic composite tube, and the lower fixing block 41 is inserted into the lower part of the bimetallic composite tube. Next, the adjusting motor 45 drives the height adjusting screw 44 to rotate, which in turn drives the sleeve 43 and its connected lower inner support rod 46 upwards. The upper end of the lower inner support rod 46 moves upwards towards the upper inner support rod 34, but the lower inner support rod 46 is not tightly attached to the upper inner support rod 34, allowing the lower inner support rod 46 and the upper inner support rod 34 to remain within the bimetallic composite tube. The tube has a short cavity structure, which is aligned with the area of ​​the bimetallic composite tube to be bent. This allows the upper inner support rod 34 and the lower inner support rod 46 to provide internal support for the area of ​​the bimetallic composite tube that does not need to be bent. Then, the vertical hydraulic tensile testing machine 21 pulls the upper mechanical clamp 32 to apply an upward tensile load to the bimetallic composite tube. At the same time, the horizontal hydraulic tensile testing machine 22 pushes the upper fixed block 31 to drive the upper mechanical clamp 32 to apply a rightward bending load to the bimetallic composite tube. At this time, the upper inner support rod 34 and the lower inner support rod 46 provide internal support for the area of ​​the bimetallic composite tube that does not need to be bent. The bimetallic composite tube is simultaneously subjected to an upward tensile load and a rightward bending load and produces corresponding deformation, effectively measuring the limit value of the combined tensile and bending test of the bimetallic composite tube.

[0035] Example 2, based on Example 1 above, as follows: Figures 1-8 As shown, in this embodiment, a hollow cavity structure 3402 is provided inside the upper inner support rod 34; an inlet pipe structure 3403 is provided at the upper end of the upper inner support rod 34, which is connected to the hollow cavity structure 3402, and the inlet pipe structure 3403 is externally connected to the output port of the heat transfer oil conveying equipment; a plurality of drainage thread structures 4601 are provided on the outer surface of the lower inner support rod 46; a liquid collection groove structure 4301 is provided on the sleeve 43, which is connected to the lower outlet end of all drainage thread structures 4601; The sleeve 43 has a vertical channel structure 4302 that connects to the liquid collection tank structure 4301; a collection pipe 47 is inserted into the vertical channel structure 4302 of the sleeve 43; a sealing ring 48 that seals the lower end of the bimetallic composite pipe is fixedly connected in the lower mechanical clamp 42; a suction pump 49 is installed on the fixed plate connected to the regulating motor 45; the inlet end of the suction pump 49 is connected to the lower outlet end of the collection pipe 47; the outlet end of the suction pump 49 is connected to the return port of the heat transfer oil conveying equipment.

[0036] In this embodiment, when the bimetallic composite pipe is clamped between the lower mechanical clamp 42 and the upper mechanical clamp 32, the lower end of the bimetallic composite pipe is tightly sealed against the sealing ring 48, the lower inner support rod 46 and the upper inner support rod 34 are both inserted into the interior of the bimetallic composite pipe, and the lower inner support rod 46 and the upper inner support rod 34 are not in close contact with each other, leaving a long distance cavity structure between the lower inner support rod 46 and the upper inner support rod 34 inside the bimetallic composite pipe. Then, the external heat conducting oil conveying device continuously conveys heat conducting oil at a specified temperature into the hollow cavity structure 3402 through the liquid inlet pipe structure 3403 of the upper inner support rod 34. The heat conducting oil flowing out of the hollow cavity structure 3402 enters the cavity structure between the lower inner support rod 46 and the upper inner support rod 34 inside the bimetallic composite pipe. The heat conducting oil then flows along the drainage thread structure 4601 of the lower inner support rod 46, through the inner wall of the bimetallic composite pipe, and into the liquid collection groove structure 4301 of the sleeve 43. Finally, the suction pump 49 sucks the heat conducting oil in the liquid collection groove structure 4301 through the collection pipe 47 and conveys it back to the external heat conducting oil conveying device, achieving the adjustment of the temperature of the bimetallic composite pipe to a specified temperature by the continuous flow of heat conducting oil through the cavity structure inside the bimetallic composite pipe. In this way, the bimetallic composite pipe can be subjected to corresponding tensile testing or bending testing under different specified temperature conditions. The temperature sensor 5 is installed in the lower mechanical clamp 42 and continuously monitors the temperature of the bimetallic composite pipe to determine whether the bimetallic composite pipe is in a specified temperature condition.

[0037] In embodiment 3, based on the above-mentioned embodiment 2, as shown in the figure, the upper end of the lower inner support rod 46 of this embodiment is provided with a plug block structure 4602 adapted to the lower outlet end of the hollow cavity structure 3402 of the upper inner support rod 34. Figures 1-8

[0038] ​In the present embodiment, after the lower inner support rod 46 and the upper inner support rod 34 are brought close to each other and tightly attached, the plug block structure 4602 at the upper end of the lower inner support rod 46 is blocked at the outlet end of the hollow cavity structure 3402 of the upper inner support rod 34, and the lower outlet end of the flow guide thread structure 3405 is aligned with the upper inlet end of the flow guide thread structure 4601. At this time, the heat conducting oil in the upper inner support rod 34 cannot flow out from the lower outlet end of the hollow cavity structure 3402, and the heat conducting oil in the upper inner support rod 34 flows out from the liquid outlet hole structure 3404 into the flow guide thread structure 3405, and then flows along the flow guide thread structure 3405 to the corresponding flow guide thread structure 4601. The heat conducting oil can continue to flow along the flow guide thread structure 3405 and the flow guide thread structure 4601 through the inner wall of the bimetallic composite pipe, and the heat conducting oil continuously flowing through the inner wall of the bimetallic composite pipe can continuously heat and conduct the bimetallic composite pipe, so as to ensure that the bimetallic composite pipe can continuously be in the specified temperature condition to complete the tensile test work. In addition, the heat conducting oil flowing through the flow guide thread structure 3405 and the flow guide thread structure 4601 can also act as a lubricant to provide lubrication for the inner wall of the bimetallic composite pipe, thereby reducing the resistance of the upper inner support rod 34 and the lower inner support rod 46 moving in the bimetallic composite pipe. Not only can the upper inner support rod 34 and the lower inner support rod 46 be more easily inserted and pulled out, but also can reduce the wear of the upper inner support rod 34 and the lower inner support rod 46 when moving in the bimetallic composite pipe.

[0039] The technical principles of the embodiments of the present application are described above in combination with specific embodiments. These descriptions are only to explain the principles of the embodiments of the present application, and cannot be interpreted in any way as a limitation on the protection scope of the embodiments of the present application. Based on the explanations here, other specific embodiments of the embodiments of the present application can be conceived by those skilled in the art without creative labor, and these embodiments will fall within the protection scope of the embodiments of the present application.

Claims

1. A method for testing large-diameter bimetallic composite pipes under combined tensile and bending loads, characterized in that: This method uses a tensile and bending testing machine to perform tensile and bending tests on large-diameter bimetallic composite pipes. In the tensile test, internal support is used to prevent collapse, thereby accurately determining the tensile test limit value. A tensile and bending testing machine includes a test bench (1), a vertical hydraulic tensile machine (21), a horizontal hydraulic tensile machine (22), an upper fixed block (31), an upper mechanical clamp (32), an inner liner block (33), an upper inner support rod (34), a lower fixed block (41), a lower mechanical clamp (42), a sleeve (43), and a lower inner support rod (46); the test bench (1) is connected to a vertical hydraulic tensile machine (21) that applies an upward tensile load; the vertical lifting component of the vertical hydraulic tensile machine (21) is connected to a horizontal hydraulic tensile machine (22) that applies a horizontal bending load; the horizontal moving component of the horizontal hydraulic tensile machine (22) is connected to the upper fixed block (31). Fixed block (31); Upper fixed block (31) is connected to upper mechanical clamp (32); Inner liner block (33) is fixed inside upper fixed block (31); Inner liner block (33) is connected to upper inner support rod (34) providing upper inner support; Upper inner support rod (34) passes downward through upper mechanical clamp (32); Lower fixed block (41) is connected inside test table (1); Lower fixed block (41) is connected to lower mechanical clamp (42); Sleeve (43) is connected inside lower fixed block (41); Lower inner support rod (46) providing lower inner support is connected inside sleeve (43); Lower inner support rod (46) passes upward through lower mechanical clamp (42). The upper inner support rod (34) has an adjusting thread structure (3401) on its outer surface; the upper inner support rod (34) is screwed onto the inner liner block (33) through the adjusting thread structure (3401). The sleeve (43) is slidably connected to the lower fixing block (41); the test bench (1) is rotatably connected to the height adjustment screw (44); the height adjustment screw (44) is screwed to the sleeve (43); the fixing plate inside the test bench (1) is equipped with an adjustment motor (45) that drives the height adjustment screw (44) to rotate.

2. The method for testing large-diameter bimetallic composite pipes under tensile and bending combined loads according to claim 1, characterized in that: The upper inner support rod (34) has a hollow cavity structure (3402) inside; the upper inner support rod (34) has a liquid inlet pipe structure (3403) that connects to the hollow cavity structure (3402); the lower inner support rod (46) has several drainage thread structures (4601) on its outer surface; the sleeve (43) has a liquid collection groove structure (4301) that connects to the drainage thread structure (4601); the sleeve (43) has a vertical channel structure (4302) that connects to the liquid collection groove structure (4301) inside; the vertical channel structure (4302) of the sleeve (43) is inserted with a collection pipe (47).

3. The method for testing large-diameter bimetallic composite pipes under tensile and bending combined loads according to claim 2, characterized in that: A sealing ring (48) is fixed inside the lower mechanical clamp (42) to seal the lower end of the bimetallic composite pipe.

4. The method for testing tensile and bending combined loads on a large-diameter bimetallic composite pipe according to claim 2, characterized in that: A suction pump (49) is installed on the fixed plate connected to the regulating motor (45); the inlet end of the suction pump (49) is connected to the lower outlet end of the collection pipe (47).

5. The method for testing large-diameter bimetallic composite pipes under tensile and bending combined loads according to claim 2, characterized in that: The upper end of the lower inner strut (46) is provided with a sealing protrusion structure (4602) that is compatible with the hollow cavity structure (3402) of the upper inner strut (34).

6. The method for testing tensile and bending combined loads on a large-diameter bimetallic composite pipe according to claim 2, characterized in that: The upper inner support rod (34) has several liquid outlet holes (3404) that connect to the hollow cavity structure (3402).

7. The method for testing large-diameter bimetallic composite pipes under tensile and bending combined loads according to claim 6, characterized in that: The outer surface of the upper inner support rod (34) is provided with a flow guiding thread structure (3405) corresponding to the number of liquid outlet hole structures (3404), and the flow guiding thread structure (3405) is connected to the corresponding liquid outlet hole structure (3404).

8. A method for testing tensile and bending combined loads on a large-diameter bimetallic composite tube according to any one of claims 2-7, characterized in that: A temperature sensor (5) for testing the temperature of the bimetallic composite tube is installed inside the lower mechanical clamp (42).

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