CN209961620U

CN209961620U - Indoor experimental device for testing mechanical behavior of floating pipe-in-pipe system

Info

Publication number: CN209961620U
Application number: CN201920345170.1U
Authority: CN
Inventors: 王新华; 王旭; 陈迎春; 辛雨函; 刘俊儒; 李延峰
Original assignee: Beijing University of Technology
Current assignee: Beijing University of Technology
Priority date: 2019-03-19
Filing date: 2019-03-19
Publication date: 2020-01-17
Anticipated expiration: 2029-03-19

Abstract

The utility model relates to an indoor experimental apparatus for testing mechanical behavior of pipe system in floating pipe. The two ends of the outer rod are respectively fixed with the clamping block and the connecting block through welding, and the inner rod in the outer rod can be applied with pulling force or pressure through the axial force loading device. In the experiment process, the rotation angle of the second chain wheel, the experiment time, the diameter of the first chain wheel and the thickness of the chain are recorded by the angle sensor, so that the compression amount or the elongation amount and the deformation speed of the inner rod can be calculated, and the torque value of the coupler recorded by the torque sensor can be used for calculating the axial tension or the pressure applied to the inner rod; the tension and pressure sensor records the data of tension and pressure applied to the double-end pin, namely the inner rod, so that the stress condition of the other end of the inner rod can be obtained. The instability mechanism of the slender rod under external load under the unsteady boundary condition is analyzed by recording multiple groups of data volumes.

Description

Indoor experimental device for testing mechanical behavior of floating pipe-in-pipe system

Technical Field

The utility model relates to an indoor experimental apparatus for be arranged in test floating pipe well pipe system mechanics action, specifically speaking are the experimental apparatus who is used for analyzing the mechanics transmission characteristic of slender pole when receiving the side direction disturbance in unsteady state outer pole.

Background

The slender rod is widely applied to engineering practice, such as a deep sea oil pipe, a drill rod in oil engineering, an oil pumping rod, a nanofiber rod and the like, and the flexible rigidity is low, so that the buckling condition is easy to occur when the slender rod is used, and the forward-rotation buckling or spiral buckling phenomenon is further generated. Meanwhile, the flexible rod is often complex in boundary conditions when in use, so that the instability characteristic of the flexible rod is more special. Therefore, the study on the instability characteristics of the slender rod under the special linear boundary condition can provide an effective theoretical basis for the use of the slender rod.

The current relevant papers are: the Harbin engineering university Ship engineering college published in the non-linear mechanics model of the axially stretched elongated rod in 2015, 04, the differential equation of motion of the elongated rod element under the axial stretching deformation is researched in the original text, and the convergence and accuracy of the stretched rod element are verified through the comparative analysis with the axially stretched cantilever beam; a seventh research institute of the middle vessel rework group company is published in petrochemical technology 2017,24(01, ANSYS Workbench-based slender strut buckling analysis research, wherein slender struts actually encountered in engineering are taken as research objects in the original text, a strut instability theory is briefly introduced, simulation modeling is performed on the slender struts through ANSYS Workbench finite element software, parameter setting and boundary condition application are performed according to actual conditions, solution is performed by using statics analysis and buckling analysis theories to obtain finite element calculation results, and finally a conclusion is obtained.

The patent refers to the field of' measuring the length of a rod in a rod body by measuring the length of the rod, and measuring the length of the rod.

Disclosure of Invention

The utility model relates to an indoor experimental apparatus for testing mechanical behavior of pipe system in floating pipe. The experimental device can be used for analyzing the mechanical transmission characteristics of the slender rod in unsteady buckling instability.

The utility model aims at:

an indoor experimental device for testing mechanical behavior of a floating pipe-in-pipe system is composed of a first frame connecting beam 1, a first screw 2, a first gasket 3, a corner bracket connecting piece 4, an inner rod axial load applying device 5, a total frame 6, a first fixing block 7, a first bolt 8, a second gasket 9, a first nut 10, an outer rod deformation applying device 11, a steel wire rope 12, a hook 13, an inner rod tail end axial load testing device 14, a second screw 15, a third gasket 16, a first bottom plate 17, a second fixing block 18, a second bolt 19, a fourth gasket 20, a second nut 21, an outer rod fixing mechanism 22, an outer rod 23 and an inner rod 24. The first frame connecting beam 1 is connected with a main frame 6 through an angle bracket connecting piece 4 and bears an inner rod axial load applying device 5; the inner rod axial load applying device 5 is connected with the main frame 6 through the angle bracket connecting piece 4; the outer rod deformation applying device 11 is connected with the main frame 6 through a first fixing block 7, a first bolt 8, a second washer 9 and a first nut 10; one end of a steel wire rope 12 is wound on the outer rod deformation applying device 11, and the other end of the steel wire rope is tied on a hook 13; the hook 13 hooks the outer rod 23; one end of the outer rod 23 is connected with the outer rod fixing mechanism 22 through welding, and the other end of the outer rod is connected with the axial load testing device 14 at the tail end of the inner rod through welding; the inner rod 24 is inserted into the outer rod 23, one end of the inner rod is contacted with the sensor probe, and the other end of the inner rod is fixed by the inner rod axial load applying device 5; the axial load testing device 14 at the tail end of the inner rod is connected with a first bottom plate 17 through a second screw 15 and a third gasket 16; the first bottom plate 17 is connected with the second fixing block 18 through a second bolt 19, a fourth washer 20 and a second nut 21; the second fixed block 18 is connected with the main frame 6 through the corner bracket connecting piece 4; the outer bar fixing means 22 are connected to the overall frame 6 by means of the corner bracket connections 4.

The utility model discloses device 5 is applyed to interior pole axial load of experimental apparatus comprises chain 25, chain tensioning device 26, a sprocket 27, a connecting axle 28, hydraulic clamping device 29, clamp plate 30, No. three bolts 31, No. five packing rings 32, No. three nuts 33, No. two sprocket 34, bearing 35, No. two connecting axles 36, No. two frame attach crossbeam 37, No. three screw 38, a backup pad 39, motor 40, shaft coupling 41, angle sensor 42, No. three frame attach crossbeam 43, No. four screws 44, No. two bottom plates 45, torque sensor 46, fastening connection 47. The chain 25 is meshed with the first chain wheel 27 and the second chain wheel 34 and is contacted with the chain expansion device 26, the chain 25 is provided with a clamping block in an arc shape, the chain is connected with the clamping block through a chain pin shaft, and the surface of the clamping block, which is contacted with the inner rod 24, is provided with a radian with the same diameter as the outer diameter of the inner rod, so that the clamping block and the inner rod 24 are tightly attached to achieve good clamping and injection performance; the first chain wheel 27 is connected with the second bottom plate 45 through a first connecting shaft 28; the second chain wheel 34 is connected with a second bottom plate 45 through a second connecting shaft 36; the bearing 35 is nested in the second chain wheel 34 and matched with the second connecting shaft 36; one end of a first connecting shaft 28 penetrates through a second bottom plate 45 and is matched with a first chain wheel 27, the other end of the first connecting shaft penetrates through a torque sensor 46 and is connected with a coupler 41, when the device works, the torque value measured by the torque sensor 46 is T, the axial tension or pressure borne by the inner rod is F, and the distance from the outer edge of the inner rod to the motor is the distance which can calculate the axial force borne by the inner rod; the angle sensor 42 is sleeved on the other connecting shaft 28, when the device works, the angle sensor 42 measures the rotating angle of the second chain wheel 34, the experimental time is t, the rotating speed of the chain wheel can be calculated, and further the moving speed of the chain is calculated; the chain expansion device 26 is connected with a second bottom plate 48 through a hydraulic clamping device 29; the pressing plate 30 is connected with the second base plate 45 through a third bolt 31, a fifth washer 32 and a third nut 33, and the pressing plate 30 plays a role in fixing the chain 25, the chain expansion device 28, the first chain wheel 27 and the second chain wheel 34 during operation; the hydraulic clamping device 29 penetrates through the pressing plate 30, the chain expansion device 26 and the second bottom plate 45, one end of the hydraulic clamping device 29 is fixedly welded with the second bottom plate 45, the other end of the hydraulic clamping device is connected with the fastening connecting piece 47 through threads, and the fastening connecting piece 47 can slide in a sliding groove in the second bottom plate 45 to cause the chain expansion device 26 to move, so that the inner rod 24 is clamped; the second frame connecting cross beam 37 is connected with the first supporting plate 39 through a fourth screw 44; the motor 40 is supported by the first supporting plate 39 and is connected with the first connecting shaft 28 through a coupling 41; the third frame connecting beam 43 is connected with the second bottom plate 45 through a fourth screw 44.

The utility model discloses experimental apparatus's chain expander device 26 comprises No. one floating fixture block 48, No. one flat head rivet 49, roller 50, No. two floating fixture blocks 51, No. two flat head rivets 52, No. three flat head rivets 53, No. three floating fixture block 54. The roller 50 is connected with the first floating fixture block 48 through a first flat head rivet 49; the first floating fixture block 48 is connected with the second floating fixture block 51 through a second flat head rivet 52; the second floating fixture block 51 is connected with the third floating fixture block 54 through a third flat head rivet 53.

The utility model discloses experimental apparatus's outer pole fixed establishment 22 comprises sliding beam 55, fixing device connecting beam 56, clamp tight piece 57, No. five screws 58. The sliding beam 55 is connected with the main frame 6 through the corner bracket connecting piece 4; the fixing device connecting beam 56 is connected with the sliding beam 55 through the angle bracket connecting piece 4; the clamping block 57 is connected with the fixture connecting beam 56 by a fifth screw 58, and the dummy pipe 23 is connected with the clamping block 57 by welding.

The utility model discloses the terminal axial load testing arrangement 14 of interior pole of experimental apparatus is kept off stopper 59, a double-end pin 60, is drawn and is pressed sensor 61, No. two double-end pin 62, connecting block 63 and constitute by the pipe end. One end of the pipe end blocking plug 59 is plugged into the inner rod 24, the other end of the pipe end blocking plug 59 is connected with the tension and compression sensor 61 through a first double-head pin 60, and the outer cylindrical surface of the pipe end blocking plug 59 is in a step shape, so that the blocking plug can be prevented from completely entering the inner rod; the other end of the tension and compression sensor 61 is connected with a connecting block 63 through a second double-headed pin 62; the connecting block 63 is connected with the second screw 15 and the third washer 16 and the first bottom plate 17.

The utility model discloses total frame 6 of experimental apparatus comprises a frame bracing piece 64, No. four frame connection crossbeams 65, a frame upper portion connection crossbeam 66, No. two frame upper portion connection crossbeams 67, No. three frame upper portion connection crossbeams 68. The first frame support rod 64 is connected with the fourth frame connecting beam 65 through the corner bracket connecting piece 4; the first frame support rod 64 is connected with a first frame upper connecting beam 66 through a corner bracket connecting piece 4; the first frame upper connecting beam 66 is connected with the second frame upper connecting beam 67 through the corner bracket connecting piece 4; the first frame upper connecting beam 66 and the third frame upper connecting beam 68 are connected by the corner bracket connection 4.

Drawings

FIG. 1 is an overall three-dimensional view of the experimental set-up of the present invention;

FIG. 2 is a front three-dimensional view of the inner rod axial load applying device of the present invention;

FIG. 3 is a rear three-dimensional view of the inner rod axial load applying device of the present invention;

FIG. 4 is a three-dimensional view of the chain expansion device of the present invention;

FIG. 5 is a three-dimensional view of the outer rod securing mechanism of the present invention;

FIG. 6 is a three-dimensional view of the inner rod end axial load testing device of the present invention;

fig. 7 is a three-dimensional view of the overall frame of the present invention;

Detailed Description

The invention will be described in more detail below by way of example with reference to the accompanying drawings:

an indoor experimental device for testing mechanical behavior of a floating pipe-in-pipe system comprises a first frame connecting beam 1, a first screw 2, a first gasket 3, an angle bracket connecting piece 4, an inner rod axial load applying device 5, a total frame 6, a first fixing block 7, a first bolt 8, a second gasket 9, a first nut 10, an outer rod deformation applying device 11, a steel wire rope 12, a hook 13, an inner rod end axial load testing device 14, a second screw 15, a third gasket 16, a first bottom plate 17, a second fixing block 18, a second bolt 19, a fourth gasket 20, a second nut 21, an outer rod fixing mechanism 22, an outer rod 23, an inner rod 24, a chain 25, a chain expansion device 26, a first chain wheel 27, a first connecting shaft 28, a hydraulic clamping device 29, a pressing plate 30, a third bolt 31, a fifth gasket 32, a third nut 33, a second chain wheel 34, a bearing 35, a second connecting shaft 36, a first connecting shaft 27, a first connecting shaft 28, a second fixing device, a second fixing, A second frame connecting beam 37, a third screw 38, a first supporting plate 39, a motor 40, a coupler 41, an angle sensor 42, a third frame connecting beam 43, a fourth screw 44, a second bottom plate 45, a torque sensor 46, a fastening connector 47, a first floating fixture block 48, a first flat head rivet 49, a roller 50, a second floating fixture block 51, a second flat head rivet 52, a third flat head rivet 53, a third floating fixture block 54, a sliding beam 55, a fixing device connecting beam 56, a clamping block 57, a fifth screw 58, a pipe end blocking plug 59, a first double head pin 60, a pulling and pressing sensor 61, a second double head pin 62, a connecting block 63, a first frame supporting rod 64, a fourth frame connecting beam 65, a first frame upper connecting beam 66, a second frame upper connecting beam 67 and a third frame upper connecting beam 68.

Combine fig. 1, the utility model discloses experimental apparatus is by frame attach crossbeam 1, a screw 2, a packing ring 3, angle leg joint spare 4, interior pole axial load applys device 5, total frame 6, a fixed block 7, a bolt 8, No. two packing rings 9, a nut 10, outer pole deformation applys device 11, wire rope 12, couple 13, interior pole terminal axial load testing arrangement 14, No. two screws 15, No. three packing rings 16, a bottom plate 17, No. two fixed blocks 18, No. two bolts 19, No. four packing rings 20, No. two nuts 21, outer pole fixed establishment 22, outer pole 23, interior pole 24 constitutes. The first frame connecting beam 1 is connected with a main frame 6 through an angle bracket connecting piece 4, bears an injection inner rod axial load applying device 5 and plays a role in enhancing the strength of a frame; the inner rod axial load applying device 5 is connected with the main frame 6 through the angle bracket connecting piece 4, and the device has the functions of completing the injection operation of the inner rod and measuring the compression amount or the elongation amount, the deformation speed and the like of the inner rod; the outer rod deformation applying device 11 is connected with the main frame 6 through a first fixing block 7, a first bolt 8, a second washer 9 and a first nut 10; one end of a steel wire rope 12 is wound on the outer rod deformation applying device 11, and the other end of the steel wire rope is tied on a hook 13; the hook 13 hooks the outer rod 23, and the outer rod deformation applying device 11, the steel wire rope 12 and the hook 13 are combined with each other to achieve the purpose of real shape of the inner rod in the sea by lifting the inner rod and the outer rod; one end of the outer rod 23 is connected with the outer rod fixing mechanism 22 through welding, and the other end of the outer rod is connected with the axial load testing device 14 at the tail end of the inner rod through welding; the inner rod 24 is inserted into the outer rod 23, one end of the inner rod is contacted with a tension-compression sensor probe, the stress condition of the tail end of the inner rod can be measured, and the other end of the inner rod is fixed by the inner rod axial load applying device 5; the axial load testing device 14 at the tail end of the inner rod is connected with a first bottom plate 17 through a second screw 15 and a third washer 16 and is used for measuring the stress condition of the tail end of the inner rod; the first bottom plate 17 is connected with the second fixing block 18 through a second bolt 19, a fourth washer 20 and a second nut 21; the second fixing block 18 is connected with the main frame 6 through the angle bracket connecting piece 4, the function of moving the position of the axial load testing device at the tail end of the inner rod can be realized through adjusting the angle bracket connecting piece, and the shapes of the inner rod and the outer rod can be further adjusted; the outer rod fixing mechanism 22 is connected with the main frame 6 through the angle bracket connecting piece 4, the device is used for fixing the position of one end of the outer rod through welding, in addition, the position of the outer rod fixing mechanism 22 can be changed through adjusting the angle bracket connecting piece, and then the position of the outer rod can be adjusted.

Combine fig. 2, fig. 3, the utility model discloses device 5 is applyed to interior pole axial load of experimental apparatus comprises chain 25, chain tensioning device 26, sprocket 27, a connecting axle 28, hydraulic clamping device 29, clamp plate 30, No. three bolts 31, No. five packing rings 32, No. three nuts 33, No. two sprockets 34, bearing 35, No. two connecting axles 36, No. two frame attach crossbeam 37, No. three screws 38, a backup pad 39, motor 40, shaft coupling 41, angle sensor 42, No. three frame attach crossbeam 43, No. four screws 44, No. two bottom plates 45, torque sensor 46, fastening connection 47. The chain 25 is meshed with the first chain wheel 27 and the second chain wheel 34 and is contacted with the chain expansion device 26, the chain 25 is provided with a clamping block in an arc shape, the chain is connected with the clamping block through a chain pin shaft, and the surface of the clamping block, which is contacted with the inner rod 24, is provided with a radian with the same diameter as the outer diameter of the inner rod, so that the clamping block and the inner rod 24 are tightly attached to achieve good clamping and injection performance; the first chain wheel 27 is connected with the second bottom plate 45 through a first connecting shaft 28; the second chain wheel 34 is connected with a second bottom plate 45 through a second connecting shaft 36; the bearing 35 is nested in the second chain wheel 34 and matched with the second connecting shaft 36; one end of a first connecting shaft 28 penetrates through a second bottom plate 45 and is matched with the first chain wheel 27, the other end of the first connecting shaft penetrates through a torque sensor 46 and is connected with the coupler 41, and the axial tension or pressure borne by the inner rod can be measured and calculated through data recorded by the torque sensor; the angle sensor 42 is sleeved on the surface of the other connecting shaft 28, and the information such as the compression amount or the extension amount of the inner rod, the deformation speed and the like can be measured and calculated according to the data recorded by the angle sensor, the diameter of the chain wheel, the thickness of the chain, the experiment time and the like; the chain expansion device 26 is connected with a second bottom plate 45 through a hydraulic clamping device 29, and the device can play a role in supporting a chain and can also play a role in clamping an outer rod when the hydraulic clamping device works; the pressing plate 30 is connected with the second base plate 45 through a third bolt 31, a fifth washer 32 and a third nut 33, and the pressing plate 30 plays a role in fixing the chain 25, the chain expansion device 26, the first chain wheel 27 and the second chain wheel 34 during operation; the hydraulic clamping device 29 penetrates through the pressing plate 30, the chain expansion device 26 and the second bottom plate 45, one end of the hydraulic clamping device 29 is fixedly welded with the second bottom plate 45, the other end of the hydraulic clamping device is connected with the fastening connecting piece 47 through threads, and the fastening connecting piece 47 can slide in a sliding groove in the second bottom plate 45 to cause the chain expansion device 26 to move, so that the inner rod 24 is clamped; the second frame connecting beam 37 is connected with the first support plate 39 through a fourth screw 44, and is connected with the main frame through an angle bracket connecting piece, so that the effect of fixing the position of the axial load applying device of the whole inner rod can be achieved, and the strength of the frame can be enhanced; the motor 40 is supported by the first supporting plate 39 and is connected with the first connecting shaft 28 through a coupler 41 so as to provide power for the whole device; the third frame connecting beam 43 is connected with the second bottom plate 45 through a fourth screw 44, and the beam is also connected with the main frame through a corner bracket connecting piece, so that the same function as the second frame connecting beam 37 can be achieved.

Referring to fig. 4, the chain expansion device 26 of the experimental apparatus of the present invention comprises a floating block 48, a flat head rivet 49, a roller 50, a floating block 51, a flat head rivet 52, a flat head rivet 53, and a floating block 54. The roller 50 is connected with the first floating fixture block 48 through a first flat head rivet 49, and the roller is in contact with the chain and reduces the friction force when the device works; the first floating fixture block 48 is connected with the second floating fixture block 51 through a second flat head rivet 52; the second floating fixture block 51 is connected with the third floating fixture block 54 through a third flat head rivet 53. Through the connection mode, the roller 50, the first floating fixture block 48 and the second floating fixture block 51 can rotate around the flat-headed rivet, so that the flexibility of the device can be greatly improved while the chain is supported, and the stretching degree of the chain in different working states can be adjusted.

Referring to fig. 5, the outer rod fixing mechanism 22 of the experimental apparatus of the present invention is composed of a sliding beam 55, a fixing device connecting beam 56, a clamping block 57, and a fifth screw 58. The sliding beam 55 is connected with the main frame 6 through the angle bracket connecting piece 4, and the sliding beam 55 can be stopped at any position on the supporting rod through the elastic angle bracket connecting piece; the fixing device connecting beam 56 is connected with the sliding beam 55 through the corner bracket connecting piece 4 and is used for installing the clamping block 57; the clamping block 57 is connected with the fixing device connecting cross beam 56 through a fifth screw 58, and the inner rod 23 is connected with the clamping block 57 through welding, so that the end position of one end of the outer rod is fixed.

Referring to fig. 6, the testing apparatus 14 for testing the axial load at the end of the inner rod of the experimental apparatus of the present invention comprises a tube end stopper 59, a first stud pin 60, a tension/compression sensor 61, a second stud pin 62, and a connecting block 63. One end of the pipe end blocking plug 59 is plugged into the inner rod 24, the other end of the pipe end blocking plug 59 is connected with the tension and compression sensor 61 through a first double-head pin 60, and the outer cylindrical surface of the pipe end blocking plug 59 is in a step shape, so that the blocking plug can be prevented from completely entering the inner rod; the other end of the tension and compression sensor 61 is connected with a connecting block 63 through a second double-headed pin 62, and the sensor can measure the stress condition of the tail end of the inner rod during an inner rod experiment; the connecting block 63 is connected with the first base plate 17 through a second screw 15 and a third washer 16 so as to fix the device for testing the axial load at the tail end of the inner rod, and the outer rod 23 is connected with the connecting block 63 through welding.

With reference to fig. 7, the utility model discloses experimental apparatus's assembly 6 comprises a frame bracing piece 64, No. four frame connection crossbeams 65, a frame upper portion connection crossbeam 66, No. two frame upper portion connection crossbeams 67, No. three frame upper portion connection crossbeams 68. The first frame supporting rod 64 is connected with the fourth frame connecting cross beam 65 through the corner bracket connecting piece 4, the first frame supporting rod 64 plays a role of supporting the whole frame, and the fourth frame connecting cross beam 65 has a reinforcing effect on the whole frame and is also connected with the first frame connecting cross beam, so that a certain supporting effect is achieved on an inner shaft axial load applying device; the first frame support rod 64 is connected with a first frame upper connecting beam 66 through a corner bracket connecting piece 4; the first frame upper connecting beam 66 is connected with the second frame upper connecting beam 67 through the corner bracket connecting piece 4; the first frame upper connecting beam 66 and the third frame upper connecting beam 68 are connected by the corner bracket connection 4. Crossbeam 67 is connected on No. two frame upper portions, No. three frame upper portions are connected crossbeam 68 and all can be played the effect that strengthens shelf intensity, and in addition, they are connected with a fixed block respectively, can play the supporting role to the outer pole shape change and exert additional device.

Claims

1. The utility model provides an indoor experimental apparatus for testing mechanical behavior of floating pipe-in-pipe system which characterized in that: the device comprises a first frame connecting beam (1), a first screw (2), a first gasket (3), a corner bracket connecting piece (4), an inner rod axial load applying device (5), a total frame (6), a first fixing block (7), a first bolt (8), a second gasket (9), a first nut (10), an outer rod deformation applying device (11), a steel wire rope (12), a hook (13), an inner rod end axial load testing device (14), a second screw (15), a third gasket (16), a first bottom plate (17), a second fixing block (18), a second bolt (19), a fourth gasket (20), a second nut (21), an outer rod fixing mechanism (22), an outer rod (23) and an inner rod (24); the first frame connecting beam (1) is connected with a main frame (6) through an angle bracket connecting piece (4) and bears an inner rod axial load applying device (5); the inner rod axial load applying device (5) is connected with the main frame (6) through an angle bracket connecting piece (4); the outer rod deformation applying device (11) is connected with the main frame (6) through a first fixing block (7), a first bolt (8), a second washer (9) and a first nut (10); one end of a steel wire rope (12) is wound on the outer rod deformation applying device (11), and the other end of the steel wire rope is tied on the hook (13); the hook (13) hooks the outer rod (23); one end of the outer rod (23) is connected with the outer rod fixing mechanism (22) through welding, and the other end of the outer rod is connected with the axial load testing device (14) at the tail end of the inner rod through welding; the inner rod (24) is inserted into the outer rod (23), one end of the inner rod is in contact with the sensor probe, and the other end of the inner rod is fixed by the inner rod axial load applying device (5); the inner rod tail end axial load testing device (14) is connected with a first bottom plate (17) through a second screw (15) and a third gasket (16); the first bottom plate (17) is connected with the second fixing block (18) through a second bolt (19), a fourth washer (20) and a second nut (21); the second fixed block (18) is connected with the main frame (6) through an angle bracket connecting piece (4); the outer rod fixing mechanism (22) is connected with the main frame (6) through the angle bracket connecting piece (4).

2. The laboratory experimental apparatus for testing mechanical behavior of a floating pipe-in-pipe system according to claim 1, wherein: the inner rod axial load applying device (5) comprises a chain (25), a chain expansion device (26), a first chain wheel (27), a first connecting shaft (28), a hydraulic clamping device (29), a pressing plate (30), a third bolt (31), a fifth gasket (32), a third nut (33), a second chain wheel (34), a bearing (35), a second connecting shaft (36), a second frame connecting beam (37), a third screw (38), a first supporting plate (39), a motor (40), a coupler (41), an angle sensor (42), a third frame connecting beam (43), a fourth screw (44), a second base plate (45), a torque sensor (46) and a fastening connecting piece (47); the chain (25) is meshed with the first chain wheel (27) and the second chain wheel (34) and is contacted with the chain expansion device (26), the chain (25) is provided with a clamping block in an arc shape, the chain is connected with the clamping block through a chain pin shaft, and the surface of the clamping block, which is contacted with the inner rod (24), is provided with a radian with the same diameter as the outer diameter of the inner rod, so that the clamping block and the inner rod (24) are tightly attached to achieve good clamping and injection performance; the first chain wheel (27) is connected with the second bottom plate (45) through a first connecting shaft (28); the second chain wheel (34) is connected with the second bottom plate (45) through a second connecting shaft (36); the bearing (35) is nested in the second chain wheel (34) and is matched with the second connecting shaft (36); one end of a first connecting shaft (28) penetrates through a second bottom plate (45) and is matched with a first chain wheel (27), and the other end of the first connecting shaft penetrates through a torque sensor (46) and is connected with a coupler (41); the angle sensor (42) is sleeved on the surface of the other connecting shaft I (28); the chain expansion device (26) is connected with a second bottom plate (45) through a hydraulic clamping device (29); the pressing plate (30) is connected with the second base plate (45) through a third bolt (31), a fifth washer (32) and a third nut (33), and the pressing plate (30) can fix the chain (25), the chain expansion device (26), the first chain wheel (27) and the second chain wheel (34) during operation; the hydraulic clamping device (29) penetrates through the pressing plate (30), the chain expansion device (26) and the second bottom plate (45), one end of the hydraulic clamping device (29) is fixed with the second bottom plate (45) through welding, the other end of the hydraulic clamping device is connected with the fastening connecting piece (47) through threads, and the fastening connecting piece (47) can slide in a sliding groove in the second bottom plate (45) to cause the chain expansion device (26) to move, so that the inner rod (24) is clamped; the second frame connecting beam (37) is connected with the first supporting plate (39) through a fourth screw (44); the motor (40) is supported by a first supporting plate (39) and is connected with a first connecting shaft (28) through a coupling (41); the third frame connecting beam (43) is connected with the second bottom plate (45) through a fourth screw (44).

3. The laboratory experimental apparatus for testing mechanical behavior of a floating pipe-in-pipe system according to claim 1, wherein: the chain expansion device (26) consists of a first floating fixture block (48), a first flat head rivet (49), a roller (50), a second floating fixture block (51), a second flat head rivet (52), a third flat head rivet (53) and a third floating fixture block (54); the roller (50) is connected with the floating fixture block (48) through a flat head rivet (49); the first floating fixture block (48) is connected with the second floating fixture block (51) through a second flat head rivet (52); the second floating fixture block (51) is connected with the third floating fixture block (54) through a third flat head rivet (53).

4. The laboratory experimental apparatus for testing mechanical behavior of a floating pipe-in-pipe system according to claim 1, wherein: the outer rod fixing mechanism (22) consists of a sliding cross beam (55), a fixing device connecting cross beam (56), a clamping block (57) and a fifth screw (58); the sliding beam (55) is connected with the main frame (6) through an angle bracket connecting piece (4); the fixing device connecting beam (56) is connected with the sliding beam (55) through the angle bracket connecting piece (4); the clamping block (57) is connected with the fixing device connecting cross beam (56) through a fifth screw (58), and the outer rod (23) is connected with the clamping block (57) through welding.

5. The laboratory experimental apparatus for testing mechanical behavior of a floating pipe-in-pipe system according to claim 1, wherein: the inner rod tail end axial load testing device (14) consists of a pipe end stop plug (59), a first double-head pin (60), a tension and compression sensor (61), a second double-head pin (62) and a connecting block (63); one end of a pipe end blocking plug (59) is plugged into the inner rod (24), the other end of the pipe end blocking plug is connected with a tension-compression sensor (61) through a first double-head pin (60), and the outer cylindrical surface of the pipe end blocking plug (59) is in a step shape, so that the blocking plug is prevented from completely entering the inner rod; the other end of the tension and compression sensor (61) is connected with a connecting block (63) through a second double-head pin (62); the connecting block (63) is connected with a second screw (15) and a first bottom plate (17) of a third gasket (16).

6. The laboratory experimental apparatus for testing mechanical behavior of a floating pipe-in-pipe system according to claim 1, wherein: the main frame (6) consists of a first frame supporting rod (64), a fourth frame connecting beam (65), a first frame upper connecting beam (66), a second frame upper connecting beam (67) and a third frame upper connecting beam (68); the first frame supporting rod (64) is connected with the fourth frame connecting beam (65) through an angle bracket connecting piece (4); the first frame supporting rod (64) is connected with a first frame upper connecting beam (66) through an angle bracket connecting piece (4); the first frame upper part connecting beam (66) is connected with the second frame upper part connecting beam (67) through an angle bracket connecting piece (4); the first frame upper part connecting beam (66) is connected with the third frame upper part connecting beam (68) through an angle bracket connecting piece (4).