Testing Device and Method for the Push-out Interlayer Shear Performance of a Tightly Wound Superconducting Coil

Abstract

The present invention discloses a testing device and method for the push-out type interlayer shear performance of a closely wound superconducting coil. The testing device includes a pressure head, a push rod, a base groove, a push block and a linear driving device. The push rod is arranged at the lower end of the pressure head. A testing cavity is provided on the base groove. Two push blocks are movably arranged in the testing cavity. The linear driving device is arranged on the base groove and can drive the two push blocks to move relatively in the testing cavity to close or separate. The block-shaped test sample cut from the closely wound superconducting coil is clamped and fixed by the two push blocks, and then the push rod is driven by a mechanical testing device to move downward and press against the superconducting wire, and gradually push it out and fall into the wire leakage position. By analyzing the collected test data, the interlayer shear performance of the closely wound superconducting coil is tested, and thus the interlayer shear strength of the superconducting coil is accurately obtained, which is of great significance for guiding the production and manufacturing of superconducting coils; in addition, the overall structure is simple, easy to implement, simple to operate, and conducive to popularization and application.

Description

Technical Field

[0001] The present invention relates to the technical field of coil testing, and particularly relates to a push-out type interlayer shear performance testing device and method for a closely wound superconducting coil. Background Art

[0002] Superconducting magnets are currently widely used in large scientific devices such as magnetically confined thermonuclear fusion, high-energy particle accelerators, and medical devices such as magnetic resonance imaging. In particular, they have a wider application prospect in the field of closely wound superconducting magnets such as nuclear magnetic resonance imaging (MRI), nuclear magnetic resonance spectroscopy (NMR), and physical property measurement systems (PPMS). Currently, these high-end devices mainly use low-temperature superconducting materials such as NbTi and Nb3Sn to manufacture magnets. In order to resist the electromagnetic force during operation, avoid the magnet from quenching due to mechanical disturbances of the superconducting wire, and improve the inter-turn insulation performance, epoxy resin is impregnated under vacuum pressure during the manufacturing process of the superconducting magnet coil, so that the superconducting magnet forms a solid overall structure to suppress the movement of the superconducting wire.

[0003] With the increasing demand for superconducting magnets with higher magnetic field strength, whether the bonding force between the superconducting wire and the insulation structure can resist the action of huge electromagnetic forces will directly affect the safe and stable operation of the superconducting magnet. Effective testing of the bonding force between the superconducting wire and the insulation structure is of great guiding significance for the design and manufacture of superconducting magnets.

[0004] Therefore, how to evaluate the interlayer shear strength of superconducting coils is one of the main design parameters determining whether they can be applied to related industries. Currently, the short beam method is mostly used for testing the interlayer shear strength of superconducting coils, and the obtained test results are the comprehensive results of the superconducting wire and the insulation structure, which do not represent the true shear performance of the superconducting coil and are generally used as a rapid screening method for the insulation structure of superconducting coils. Therefore, the design of a device and method for testing the shear performance of the superconducting wire and the insulation structure in superconducting coils is of great significance for guiding the engineering design and manufacture of superconducting magnets. Summary of the Invention

[0005] Aiming at the above deficiencies, the purpose of the present invention is to provide a push-out type interlayer shear performance testing device for a closely wound superconducting coil with a reasonable structural design, which can realize the testing of the interlayer shear performance of the closely wound superconducting coil and has good testing effects.

[0006] The purpose of the present invention is also to provide a method for testing the push-out type interlayer shear performance of a closely wound superconducting coil. This testing method is easy to operate, can realize the testing of the interlayer shear performance of the closely wound superconducting coil, and thus accurately obtain the interlayer shear strength of the superconducting coil.

[0007] The technical solutions provided by the present invention to achieve the above purposes are as follows:

[0008] A test device for the push-out interlayer shearing performance of a closely wound superconducting coil, which includes a pressure head, a push rod, a base groove, a push block, and a linear driving device. The pressure head is arranged on a mechanical testing device and is connected to the sensor of the mechanical testing device. The push rod is arranged at the lower end of the pressure head. A test cavity is provided on the base groove. Two push blocks are movably arranged in the test cavity. The linear driving device is arranged on the base groove and can drive the two push blocks to move relatively in the test cavity to close or separate. A wire leakage position is provided on the bottom surface of the test cavity.

[0009] As a preferred embodiment of the present invention, the cavity wall of the test cavity has an interlayer space, and a vacuum flange communicating with the interlayer space is provided on the base groove and is connected to a vacuum pumping device through the vacuum flange to reduce the large volatilization of liquid nitrogen during testing under low-temperature conditions.

[0010] As a preferred embodiment of the present invention, the two side walls of the base groove symmetrically bulge outward to form mounting platforms. The linear driving device includes a screw rod and a screw rod support seat. The screw rod support seat is arranged on the mounting platform. The screw rod is arranged on the screw rod support seat, and one end of the screw rod extends into the test cavity and is rotatably connected to the back surface of the push block.

[0011] As a preferred embodiment of the present invention, it further includes a bellows. A through hole for the screw rod to pass through is provided on the cavity wall of the test cavity. One end of the bellows is sleeved on the outer edge of the through hole, and the other end is connected to the back surface of the push block. Sealing is carried out through the bellows to prevent the leakage of liquid nitrogen under low-temperature testing. One end of the screw rod axially passes through the through hole and the bellows and is rotatably connected to the back surface of the push block. If a concave cavity is provided on the back surface of the push block, a tapered bearing or a combination of a deep groove ball bearing and a thrust bearing sleeved on the screw rod is arranged in the concave cavity to play an axial and radial supporting role.

[0012] As a preferred embodiment of the present invention, a heat insulation board is provided between the mounting platform and the screw rod support seat to reduce heat leakage.

[0013] A test method for the above-mentioned test device for the push-out interlayer shearing performance of a closely wound superconducting coil includes the following steps:

[0014] S1: Cut the closely wound superconducting coil to be tested to obtain a block-shaped test sample. The block-shaped test sample includes an insulating block and a number of superconducting wires embedded and penetrating the insulating block from top to bottom;

[0015] S2: Place the block-shaped test sample between the two push blocks, and make one end of the superconducting wire face the push rod of the electronic universal testing machine. Drive the two push blocks to move towards each other through the linear driving device to clamp and fix the block-shaped test sample;

[0016] S3: Adjusting a mandrel of the mechanical testing device to align with any superconducting wire on the insulating block, wherein the outer diameter of the mandrel is preferably 5 to 10 microns smaller than the diameter of the superconducting wire;

[0017] S4: Evacuate the base tank and then add liquid nitrogen to the test chamber. This evacuation reduces heat leakage and the volatilization rate of the liquid nitrogen. The mechanical testing apparatus's top rod is controlled to move downward, gradually pushing the superconducting wire aligned with it out of the insulation block and into the leaking wire position. Test data is recorded. The top rod's downward speed is 0.5 to 2 mm / min, preferably 1 mm / min.

[0018] As a preferred solution of the present invention, the densely wound superconducting coil is manufactured by the following steps:

[0019] (1) preparing a winding frame and a superconducting wire, and winding the superconducting wire around the winding frame in a dense winding manner turn by turn and layer by layer to obtain a winding coil having an arc-shaped portion and a straight-shaped portion;

[0020] (2) Immersing the wound coil in insulating glue and then curing it to form a densely wound superconducting coil;

[0021] (3) The densely wound superconducting coil is cut transversely corresponding to the position of the straight portion to obtain a block test sample with a thickness of 10 to 20 mm.

[0022] The beneficial effects of the present invention are as follows: the structure design of the push-out interlayer shear performance testing device for densely wound superconducting coils provided by the present invention is reasonable, the block test sample cut from the densely wound superconducting coil is clamped and fixed by two push blocks, and then the push rod is driven downward by the mechanical testing equipment to press on the superconducting wire, and is gradually pushed out and dropped into the leaking wire position, and the collected test data is analyzed to realize the test of the interlayer shear performance of the densely wound superconducting coil, thereby accurately obtaining the interlayer shear strength of the superconducting coil, which is of great significance for guiding the production and manufacturing of superconducting coils; in addition, the overall structure is simple, easy to implement, simple to operate, and conducive to popularization and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the three-dimensional structure of the present invention.

[0024] Figure 2 It is a schematic diagram of the AA cross-sectional structure of the present invention.

[0025] Figure 3 It is a schematic diagram of the BB cross-sectional structure of the present invention.

[0026] Figure 4 Schematic diagram of the structure of the block test sample in the present invention. DETAILED DESCRIPTION

[0027] Example: Refer to Figures 1 to 4 , a push-out type interlayer shear performance testing device for a closely wound superconducting coil provided by the present invention, which includes a pressure head 1, a push rod 2, a base groove 3, a push block 4, a linear driving device 5 and a bellows 6.

[0028] The pressure head 1 is arranged on a mechanical testing device and is connected to the sensor of the mechanical testing device. The pressure head 1 can be made of conventional stainless steel materials and is easy to process.

[0029] The push rod 2 is arranged at the lower end of the pressure head 1. A screw hole is provided at the lower end of the pressure head 1, and an external thread adapted to the screw hole is provided at the upper end of the push rod 2. The upper end of the push rod 2 is installed on the screw hole through a threaded structure, which brings convenience to replacement. The push rod 2 is preferably made of high-strength steel, such as 34CrNiMo6 high-strength alloy, with high strength. At the same time, a push rod 2 with a corresponding diameter is selected according to the wire diameter of the superconducting wire to be tested. The outer diameter dimension of the push rod 2 is preferably 5-10 microns smaller than the wire diameter of the superconducting wire.

[0030] A test cavity 31 is provided on the base groove 3. A wire leakage position 32 is provided at the center of the bottom surface of the test cavity 31 to enable the superconducting wire to be pushed out without interference. Two push blocks 4 are movably arranged in the test cavity 31. The bottom surface of the test cavity 31 is a smooth surface, and the push blocks 4 are movably placed on the bottom surface of the test cavity 31. It is also possible to provide a slide rail on the bottom surface of the test cavity 31, and a slider or chute adapted to the slide rail on the bottom surface of the push block 4, also realizing the movable arrangement in the test cavity 31.

[0031] The linear driving device 5 is arranged on the base groove 3 and can drive the two push blocks 4 to move towards or away from each other in the test cavity 31. Symmetrically outward protrusions are formed on both side walls of the base groove 3 to form mounting platforms 33. In this embodiment, the linear driving device 5 includes a screw rod 51 and a screw rod support seat 52. The screw rod support seat 52 is arranged on the mounting platform 33. Preferably, a heat insulation plate 53 is provided between the mounting platform 33 and the screw rod support seat 52 to reduce heat leakage. The screw rod 51 is arranged on the screw rod support seat 52, and one end of the screw rod 51 extends into the test cavity 31 and is rotatably connected to the back surface of the push block 4. In this embodiment, a concave cavity is provided at the center position of the back surface of the push block 4 corresponding to the center of the bellows 6, and a tapered bearing is arranged in the concave cavity, which can bear radial loads and single-direction axial loads. One end of the screw rod 51 axially passes through the through hole and the bellows 6 and is adapted to the tapered bearing. In other embodiments, a combination of deep groove ball bearings and thrust bearings can also be used to realize the rotational connection to the back surface of the push block 4.

[0032] By rotating the screw rod 51, the position of the pushing block 4 is adjusted to achieve the purpose of clamping the block-shaped test sample 7, and it is also convenient to quickly move the position of the block-shaped test sample 7, saving the test time.

[0033] Preferably, the cavity wall of the test cavity 31 has a sandwich space, and a vacuum flange 34 communicating with the sandwich space is provided on the base groove 3. The vacuum flange 34 is connected to a vacuum pumping device to reduce the volatilization of a large amount of liquid nitrogen during testing under low-temperature conditions. A through hole for the screw rod 51 to pass through is provided on the cavity wall of the test cavity 31. One end of the bellows 6 is sleeved on the outer edge of the through hole and welded to the cavity wall of the test cavity 31, and the other end of the bellows 6 is welded to the back of the pushing block 4. The bellows 6 is used for socket sealing to prevent the leakage of liquid nitrogen under low-temperature testing.

[0034] During testing, the tightly wound superconducting coil push-out type interlayer shear performance testing device of the present invention is installed on a mechanical testing device. In this embodiment, the mechanical testing device is preferably an electronic universal testing machine; specifically, it includes the following steps:

[0035] S1: First, a tightly wound superconducting coil to be tested needs to be prepared, a winding frame and superconducting wire are prepared. The superconducting wire can be superconducting wires such as NbTi and Nb3Sn. The winding frame is wrapped with insulating material and release cloth, and the winding frame is fixed on the winding machine tooling. The inlet end of the superconducting wire is fixed, and the superconducting wire is wound around the winding frame in a turn-by-turn and layer-by-layer tightly wound manner. After the coil is wound to the set size, the outlet end of the superconducting wire is fixed, and insulating material and release cloth are wrapped to obtain the wound coil. For convenience of testing, the wound coil is preferably in a racetrack shape, having an arc portion and a straight portion; in other embodiments, the wound coil can also be circular or square, etc.

[0036] S2: The wound coil is placed in a mold of a pressure tank for vacuum heating and degassing. Epoxy resin GY282, diluent DY3601, and curing agent HY5200 are selected as the impregnating and filling material, that is, insulating glue, according to a mass percentage ratio of 60:40:21. After the epoxy resin GY282, diluent DY3601, and curing agent HY5200 are subjected to vacuum degassing treatment at 40°C, they are injected into a mixing tank for continuous degassing and mixing. After degassing and stirring evenly, they are poured, and heated to 85°C in the pressure tank for heat preservation for 30 h, and heated to 135°C for heat preservation for 28 h for curing. After curing, the final tightly wound superconducting coil is formed;

[0037] S3: Take out the closely wound superconducting coil from the pressure tank and demold it. Horizontally water-cut the closely wound superconducting coil at the position corresponding to the linear part to obtain a block-shaped test sample 7 with a thickness of 10 - 20 mm. Check the dimensions of the block-shaped test sample 7 processed by testing and make records. The block-shaped test sample 7 includes an insulating block 71 and a number of superconducting wires 72 embedded and penetrating the insulating block 71 from top to bottom;

[0038] S4: Place the block-shaped test sample 7 between two push blocks 4, and make one end of the superconducting wire 72 face the ejector rod 2 of the electronic universal testing machine. Drive the two push blocks 4 to move towards each other through a linear drive to clamp and fix the block-shaped test sample 7, and adjust the perpendicularity of the block-shaped test sample 7 to ensure that a shear force load of 90° is achieved;

[0039] S5: Adjust the ejector rod 2 of the electronic universal testing machine to align with any one of the superconducting wires 72 on the insulating block 71;

[0040] S6: Evacuate the base groove 3, then add liquid nitrogen into the test chamber 31. After the liquid level in the liquid nitrogen tank is relatively stable, control the ejector rod 2 of the electronic universal testing machine to descend at a loading speed of 1 mm / min to push the superconducting wire 72 opposite to it out of the insulating block 71 completely and fall into the wire leakage position 32, and record the test data;

[0041] S7: Analyze the collected test data after each block-shaped test sample 7 is tested. Repeat S4 to S6 until all test samples are tested and the test ends. By analyzing the collected test data, the interlayer shear performance of the closely wound superconducting coil is tested, and thus the interlayer shear strength of the superconducting coil can be accurately obtained, which can be used to guide the design and manufacture in the field of closely wound superconducting magnets such as nuclear magnetic resonance imaging, nuclear magnetic resonance spectroscopy, and comprehensive physical property measurement systems.

[0042] According to the revelation and teaching of the above specification, those skilled in the art of the present invention can also make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention. In addition, although some specific terms are used in this specification, these terms are only for convenience of description and do not constitute any limitation to the present invention. As described in the above embodiments of the present invention, other test devices and test methods obtained by adopting the same or similar structures are within the protection scope of the present invention.

Claims

1. A test device for the push-out type interlayer shear performance of a closely wound superconducting coil, which includes a pressure head. The pressure head is arranged on a mechanical testing device and is connected to the sensor of the mechanical testing device. It is characterized in that, It also includes a push rod, a base groove, a push block and a linear drive device. The push rod is arranged at the lower end of the pressure head. The base groove is provided with a test cavity. Two push blocks are movably arranged in the test cavity. The linear drive device is arranged on the base groove and can drive the two push blocks to relatively close or separate in the test cavity. A leakage position is provided on the bottom surface of the test cavity. The densely wound superconducting coil to be tested is cut to obtain a block test sample, which includes an insulating block and a plurality of superconducting wires embedded and extending through the insulating block from top to bottom. The block test sample is placed between two push blocks, with one end of the superconducting wire facing the push rod of an electronic universal testing machine. A linear drive device drives the two push blocks toward each other to clamp and secure the block test sample. The push rod of a mechanical testing device is adjusted to align with any superconducting wire on the insulating block. The push rod of the mechanical testing device is controlled downward to gradually push the superconducting wire aligned with the push rod out of the insulating block and into the leakage position, and the test data is recorded. The outer diameter of the mandrel is 5 to 10 microns smaller than the diameter of the superconducting wire, the thickness of the block test sample is 10 to 20 mm, and the downward speed of the mandrel of the mechanical testing equipment is 0.5 to 2 mm / min; The cavity wall of the test cavity has an interlayer space, and a vacuum flange connected to the interlayer space is provided on the base groove; The two side walls of the base groove symmetrically protrude outward to form a mounting platform; The linear drive device includes a screw and a screw support seat, the screw support seat is arranged on the mounting table, the screw is arranged on the screw support seat, and one end of the screw extends into the test cavity and is rotatably connected to the back of the push block; It also includes a bellows, a through hole for the screw to pass through is provided on the cavity wall of the test cavity, one end of the bellows is sleeved on the outer edge of the through hole, and the other end is connected to the back of the push block, one end of the screw axially passes through the through hole and the bellows, and is rotatably connected to the back of the push block; A heat insulation board is provided between the mounting platform and the screw support seat.

2. A testing method for the interlayer shear performance of the closely wound superconducting coil push-out type testing device described in claim 1, characterized in that, It includes the following steps: S1: Cutting the densely wound superconducting coil to be tested to obtain a block test sample, wherein the block test sample includes an insulating block and a plurality of superconducting wires embedded from top to bottom through the insulating block; S2: placing the block test sample between two push blocks, with one end of the superconducting wire facing the top rod of the electronic universal testing machine, and driving the two push blocks to move toward each other by a linear drive device to clamp and fix the block test sample; S3: adjusting the top rod of the mechanical testing device to align with any superconducting wire on the insulating block; S4: Control the push rod of the mechanical testing equipment to push the superconducting wire relative to it downward to gradually push it out of the insulation block and drop it into the leakage line position, and record the test data.

3. The test method according to claim 2, characterized in that, The densely wound superconducting coil is manufactured by the following steps: (1) preparing a winding frame and a superconducting wire, and winding the superconducting wire around the winding frame in a turn-by-turn and layer-by-layer dense winding manner to obtain a winding coil having an arc-shaped portion and a straight-shaped portion; (2) Immerse the wound coil in insulating glue and then cure it to form a densely wound superconducting coil; (3) The densely wound superconducting coil is cut transversely corresponding to the position of the straight portion to obtain a block-shaped test sample.

4. The test method according to claim 2, wherein In step S4, the base tank is vacuumed in advance, and then liquid nitrogen is added into the test cavity.

5. The test method according to claim 2, wherein The downward speed of the mandrel of the mechanical testing equipment is 0.5 to 2 mm / min, the outer diameter of the mandrel is 5 to 10 microns smaller than the diameter of the superconducting wire, and the thickness of the block test sample is 10 to 20 mm.

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