CN115728131A - Device for realizing continuous application of large-stress load at low temperature by using superconducting coil - Google Patents

Abstract

The invention discloses a device which utilizes superconducting coils to realize continuous application of large stress loads at low temperatures. The base is connected to the shell, and there is a circular boss in the middle of the base to limit the position of the lower round cake coil, and the pressure plate is placed on the upper round cake coil. At the top, there is a circular boss in the middle of the bottom of the pressure plate to limit the upper circular cake coil. The pressure plate is connected with the piston, and the top block is placed above the piston to contact the sample and apply pressure. The upper and lower round cake coils are wound on the stainless steel skeleton by means of wet winding or dry winding impregnation of NbTi superconducting wires. When the upper and lower circular pie coils pass a reverse current to generate electromagnetic repulsion, the upper circular cake coil is pushed upwards and transmitted to the top block through the pressure plate and the piston, thereby exerting pressure on the sample. The invention uses the electromagnetic repulsion generated by the superconducting coil to continuously apply a large stress load to the test sample at low temperature. The stress-dependent measurement of critical properties such as cables provides a new low-temperature stress continuous loading device.

Description

A device that uses superconducting coils to realize continuous application of large stress loads at low temperatures

technical field

The invention relates to the field of stress-dependent measurement of the critical performance of a low-temperature superconducting conductor, in particular to a device that utilizes a superconducting coil to realize continuous application of large stress loads at low temperatures.

Background technique

In recent years, with the development of superconducting technology, particle accelerators and fusion magnets require stable superconducting materials to obtain higher magnetic fields. Critical current (I _c ) is one of the important properties to measure the performance of superconducting materials, and temperature and magnetic field will have certain influence on critical current. At present, NbTi and Nb ₃ Sn are still the main superconducting materials for large-scale superconducting applications. NbTi is a tough material and is easy to process. Many magnets in the past were made of NbTi, but its critical performance is poor and it is difficult to obtain higher magnetic field. The critical performance of Nb ₃ Sn is significantly higher than that of NbTi, so in order to obtain a higher magnetic field, brittle Nb ₃ Sn or new practical high-temperature superconducting materials (MgB ₂ , Bi-2212, YBCO, etc.) must be selected, but due to technical As well as commercial reasons, new practical high-temperature superconducting materials have not yet been put into use on a large scale. Therefore, Nb ₃ Sn must be chosen for higher field superconducting applications.

The Nb ₃ Sn superconducting wire is not a monolithic structure, but needs to be embedded in a common metal structure to obtain higher mechanical properties and thermal stability. With the development of technology, different wire manufacturing techniques are used for production. At present, the manufacturing technologies mainly used to produce commercial Nb ₃ Sn superconducting wires include: bronze method, PIT, RRP and so on. All Nb ₃ Sn must undergo heat treatment to make the internal material react to form a superconducting phase. In order to avoid excessive self-inductance, superconducting cables made of multi-strand superconducting wires are usually used to develop large-scale superconducting magnets. For example, most accelerator magnets use Rutherford cables, which have a twisted structure and can realize complete transposition of superconducting wires. Rutherford cables have the advantages of high current density, good mechanical strength, compact winding structure, and low coil circulation loss. The critical properties of Nb ₃ Sn after heat treatment are very sensitive to stress and strain. Under the influence of electromagnetic, mechanical and thermal stress under high field, the performance usually declines. Therefore, it is necessary to continuously apply stress to Nb ₃ Sn materials/conductors by means of experiments. The stressed state during its operation, assessing the stress dependence of its critical performance.

At present, various measurement technologies are developing rapidly, and many methods of applying loads to Nb ₃ Sn Rutherford cables have emerged, but they are all limited by the size of the structure, unable to achieve continuous loading of stress at low temperatures, and the process of applying loads is cumbersome. Easy to operate. The present invention develops a device that uses the electromagnetic repulsion of superconducting coils to realize continuous application of large stress loads at low temperatures, which can apply continuous large-range loads to Nb ₃ Sn Rutherford cable test samples in extremely low temperature (4.2K) environments, and It can accurately measure the load size, simplifies the load application procedure, shortens the test time, and improves the load loading range. At the same time, the applied load is measured by the extensometer and the strain gauge, which improves the accuracy of the load measurement and provides a key infrastructure for the critical performance degradation research of the Nb ₃ Sn Rutherford cable under the transverse stress load.

Contents of the invention

The purpose of the present invention is to provide a device that utilizes the electromagnetic repulsion of superconducting coils to realize continuous application of large stress loads at low temperatures. The low-temperature electromagnetic continuous pressurization device can treat Nb ₃ Sn Rutherford The cable test sample is continuously loaded and the magnitude of the load can be accurately measured.

In order to achieve the above object, the technical scheme adopted in the present invention is:

A device that uses superconducting coils to achieve continuous application of large stress loads at low temperatures:

The device comprises a base, an upper disc coil, a lower disc coil, a pressing plate, a casing, a piston, a top block, an extensometer and a strain gauge;

Wherein, the upper circular cake coil and the lower circular cake coil are superconducting coils; the base is connected with the casing bolts, and a circular boss is provided in the middle of the base to limit the position of the lower circular cake coil, and the pressure plate is placed above the upper circular cake coil. There is also a circular boss in the middle of the bottom of the pressure plate to limit the position of the upper circular cake coil. The pressure plate is connected with the piston bolts, and the top block is placed above the piston to contact the sample and apply pressure;

When the upper and lower circular cake coils pass the reverse current to generate electromagnetic repulsion, the upper circular cake coil is pushed upwards and transmitted to the top block through the pressure plate and the piston, thereby continuously applying pressure to the sample; the displacement change of the pressure plate is detected by the extensometer, The strain gauge detects the strain at both ends of the top block, and calculates the stress value applied to the sample by combining the current input to the lower disc coil and the self-weight of the upper disc coil, pressure plate, piston, and top block, and monitors the uniformity of the applied stress in real time.

Further, the material of the base, the pressing plate, the shell and the top block is stainless steel.

Further, the material of the base, the pressure plate, the shell and the top block is 304 stainless steel.

Further, the piston material is carbon fiber. Compared with stainless steel, carbon fiber is less dense and stronger, and it can also maintain good strength in extremely low temperature environments.

Further, the upper and lower circular pie coils are composed of NbTi superconducting wires wound on the stainless steel skeleton by means of wet winding or dry winding impregnation. NbTi superconducting wires are in a superconducting state at an extremely low temperature of 4.2K. Compared with conventional resistance coils, they have no heat loss and higher current-carrying capacity. At this time, when reverse current is passed to the upper and lower round pie coils, electromagnetic waves will be generated. Repulsive force, the upper disc coil will be jacked up, and the pressure will be transmitted upwards to the top block through the pressure plate and the piston.

Further, the top block is made of 316 stainless steel, and its corners are rounded to avoid stress concentration during the process of applying pressure to the test sample.

Further, the extensometer is installed on the pin passing through the upper disc coil to measure the relative displacement caused by the electromagnetic repulsion after the upper and lower disc coils are energized, and the upper and lower disc coils are calculated by combining the energized current The electromagnetic repulsion force generated after electrification subtracts the gravity of the pressure plate, piston, and top block to obtain the pressure value applied to the surface of the sample.

Further, the two strain gauges are respectively installed on both sides of the top block. When the upper and lower circular cake coils pass the reverse current to generate electromagnetic repulsion, the force is transmitted to the top block through the pressure plate and the piston, and then applied to the surface of the test sample. When the top block is stressed, it will produce a small deformation. The strain gauge can calculate the force of the top block by measuring the small deformation of the top block, that is, the magnitude of the load applied by the test sample, and at the same time judge the uniformity of the pressure.

Further, the load applied to the test sample is obtained by measuring and calculating the strain gauge and the extensometer respectively, so as to provide load measurement precision and accuracy.

The beneficial effects of the present invention are: the present invention utilizes the electromagnetic repulsion generated by the superconducting coil to continuously apply a large stress load to the test sample at low temperature. , providing a new low-temperature stress continuous loading device for the stress-dependent measurement of critical properties such as various types of superconducting cables.

Description of drawings

Figure 1 is a structural diagram of a device that utilizes the electromagnetic repulsion of superconducting coils to realize continuous application of large stress loads at low temperatures.

In the figure: 1-strain gauge, 2-top block, 3-housing, 4-piston, 5-extensometer, 6-press plate, 7-upper circular cake coil, 8-lower circular cake coil, 9-base.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and embodiments.

As shown in Figure 1, a device that uses the electromagnetic repulsion of superconducting coils to realize continuous application of large stress loads at low temperatures includes a base 9, an upper circular cake coil 7, a lower circular cake coil 8, a pressure plate 6, a casing 3, and a piston 4. Jack block 2, extensometer 5 and strain gauge 1. Among them, the base 9, the pressure plate 6, the shell 3 and the top block 2 are made of stainless steel, the base 9 is connected with the shell 3 by bolts, and there is a circular boss in the middle of the base 9 to limit the position of the lower round cake coil 8, and the pressure plate 6 is placed on the upper Above the circular cake coil 7, there is a circular boss in the middle below the pressure plate 6 to limit the 7 circles of the upper circular cake line. The pressure plate 6 is connected with the piston 4 by bolts, and the top block 2 is placed above the piston 4 to contact the sample and apply pressure. The upper and lower round cake coils 7 and 8 are wound on the stainless steel frame by means of wet winding or dry winding impregnation of NbTi superconducting wires. When the upper and lower pancake coils 7 and 8 pass a reverse current to generate electromagnetic repulsion, the upper pancake coil 7 is pushed upwards and transmitted to the top block 2 through the pressure plate 6 and the piston 4, thereby continuously applying pressure to the sample. The extensometer 5 detects the displacement variation z of the pressure plate 6, and the strain gauge 1 detects the deformation ∈ at both ends of the top block 2, combined with the current input to the superconducting coil and the upper circle coil 7, pressure plate 6, piston 4, and top block 2 The self-weight can be calculated to obtain the stress value exerted on the sample, according to the formula:

σ=∈×E

Wherein, σ is the stress generated inside the top block 2 by the repulsive force transmitted upward by the piston 4, ∈ is the strain generated by the top block 2 measured by the strain gauge, and E is the elastic modulus of the top block 2 under this condition. Through this formula, the internal stress of the jack block 2 can be calculated. Simultaneously, since the stress condition of the jack block 2 is only the vertical upward force, the internal stress of the jack block 2 is equal to the pressure generated by the thrust of the piston 4 on the jack block 2 . Then according to the area of the top block 2, the magnitude of the upward force can be calculated. The strain gauges on both sides of the top block 2 can monitor the uniformity of the applied stress in real time.

Then according to the formula:

Wherein, F is the electromagnetic repulsion generated by the upper round cake coil 7 and the lower round cake coil 8 energization, I is the current size of the upper round cake coil 7 and the lower round cake coil 8 energization, and _M12 is the upper round cake coil 7 and the lower circle The mutual inductance between the cake coils 8, z is the displacement measured by the extensometer, m is the mass of the pressing plate 6 and the piston 4, and g is the acceleration of gravity. According to this formula, the magnitude of the electromagnetic repulsion can be calculated.

The materials of the base 9, the pressing plate 6, the shell 3 and the top block 2 are 304 stainless steel.

The piston 4 is made of carbon fiber, which is less dense and stronger than stainless steel, and can also maintain good strength in extremely low temperature environments.

The upper and lower round cake coils 7 and 8 are wound on the stainless steel frame by means of wet winding or dry winding impregnation of NbTi superconducting wires. NbTi superconducting wires are in a superconducting state at an extremely low temperature of 4.2K. Compared with conventional resistance coils, they have no heat loss and higher current-carrying capacity. At this time, reverse current is passed to the upper and lower circular pie coils 7 and 8, then Electromagnetic repulsion will be generated, and the upper disc coil 7 will be pushed up, and the pressure will be transmitted upward to the top block 2 through the pressure plate 6 and the piston 4 .

The top block 2 is made of 316 stainless steel with rounded corners to avoid stress concentration during the process of applying pressure to the test sample.

The extensometer 5 is installed on the pin passing through the upper disc coil 7 to measure the relative displacement of the upper and lower disc coils 7 and 8 due to the electromagnetic repulsion after being energized, and the upper and lower disc coils are calculated by combining the energized current 7, 8 The electromagnetic repulsion force generated after energization is subtracted from the gravity of the pressure plate 6, piston 4, and top block 2 to obtain the pressure value applied to the sample surface.

Two strain gauges 1 are installed on both sides of the top block 2. When the upper and lower round cake coils 7 and 8 pass reverse current to generate electromagnetic repulsion, the force is transmitted to the top block 2 through the pressure plate 6 and the piston 4, and then applied to the test sample surface. When the top block 2 is stressed, it will produce a small deformation. The strain gauge 1 can calculate the force of the top block 2 by measuring the small deformation of the top block, that is, the magnitude of the load applied by the test sample, and at the same time judge the uniformity of the pressure. Calculated as follows:

σ=∈×E

Wherein, σ is the stress generated inside the top block 2 by the repulsive force transmitted upward by the piston 4, ∈ is the strain generated by the top block 2 measured by the strain gauge, and E is the elastic modulus of the top block 2 under this condition. The internal stress of the top block 2 under stress can be calculated through the formula. Simultaneously, since the force condition of the jack block is only the vertical upward force, the internal stress of the jack block 2 is equal to the pressure generated by the thrust of the piston 4 on the jack block 2 . Then according to the area of the top block 2, the magnitude of the upward force can be calculated. Strain gauges on both sides of the top block can monitor the uniformity of the applied stress in real time.

The present invention uses the strain gauge 1 to measure the strain of the top block 2 due to the pressure generated on the basis of measuring the electromagnetic repulsion F generated by the energization of the upper round cake coil 7 and the lower round cake coil 8, thereby calculating the force on the top block 2 and adopting the extensometer 5. Measure the small upward displacement of the upper disc coil 7 due to the electromagnetic repulsion F to calculate the force on the top block 2. The load applied to the test sample can be obtained by combining the two methods, which can achieve mutual verification and measurement. Accuracy to improve the effect of load measurement precision and accuracy.

Claims (8)

1. A device utilizing a superconducting coil to realize continuous application of a large stress load at low temperature, characterized in that: The device comprises a base, an upper disc coil, a lower disc coil, a pressing plate, a casing, a piston, a top block, an extensometer and a strain gauge; Wherein, the upper circular cake coil and the lower circular cake coil are superconducting coils; the base is connected with the casing bolts, and a circular boss is provided in the middle of the base to limit the position of the lower circular cake coil, and the pressure plate is placed above the upper circular cake coil. There is also a circular boss in the middle of the bottom of the pressure plate to limit the position of the upper circular cake coil. The pressure plate is connected with the piston bolts, and the top block is placed above the piston to contact the sample and apply pressure; When the upper and lower circular cake coils pass the reverse current to generate electromagnetic repulsion, the upper circular cake coil is pushed upwards and transmitted to the top block through the pressure plate and the piston, thereby continuously applying pressure to the sample; the displacement change of the pressure plate is detected by the extensometer, The strain gauge detects the strain at both ends of the top block, and calculates the stress value applied to the sample by combining the current input to the lower disc coil and the self-weight of the upper disc coil, pressure plate, piston, and top block, and monitors the uniformity of the applied stress in real time. 2. A kind of device utilizing superconducting coils to realize continuous application under low temperature of large stress load according to claim 1, characterized in that: The material of the base, the pressing plate, the shell and the top block is stainless steel. 3. A device utilizing superconducting coils to realize continuous application of large stress loads at low temperatures according to claim 2, characterized in that: The material of the base, pressing plate, shell and top block is 304 stainless steel. 4. A device utilizing superconducting coils to realize continuous application of large stress loads at low temperatures according to claim 1, characterized in that: The piston material is carbon fiber. 5. A device utilizing superconducting coils to realize continuous application of large stress loads at low temperatures according to claim 1, characterized in that: The upper and lower round cake coils are composed of NbTi superconducting wire wound on the stainless steel skeleton by means of wet winding or dry winding impregnation. 6. A device utilizing a superconducting coil to continuously apply a large stress load at low temperature according to claim 1, characterized in that: The top block is made of 316 stainless steel with rounded corners. 7. A device utilizing superconducting coils to realize continuous application of large stress loads at low temperatures according to claim 1, characterized in that: The extensometer is installed on the pin passing through the upper pancake coil to measure the relative displacement caused by the electromagnetic repulsion after the upper and lower pancake coils are energized, and combined with the energized current to calculate the displacement of the upper and lower pancake coils after energization. The electromagnetic repulsion of the pressure plate, the piston, and the top block are subtracted to obtain the pressure value applied to the surface of the sample. 8. A device utilizing superconducting coils to realize continuous application of large stress loads at low temperatures according to claim 1, characterized in that: Two strain gauges are respectively installed on both sides of the top block. When the upper and lower circular cake coils pass a reverse current to generate electromagnetic repulsion, the force is transmitted to the top block through the pressure plate and the piston, and then applied to the surface of the test sample. When the top block is subjected to There will be a small deformation when the force is applied, and the strain gauge can calculate the force of the top block by measuring the small deformation of the top block, that is, the magnitude of the load applied by the test sample, and at the same time judge the uniformity of the pressure.

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