A measuring device and method for real-time detecting the effective strain state of a superconducting sample under different tensile and torsional strains

Abstract

The present invention discloses a measuring device and method for real-time detecting the effective strain state of a superconducting sample under different tensile and torsional strains. The measuring device includes components such as a cryogenic dewar, a heater, a coil group, a rotary drive assembly, a linear drive assembly, a sample rod, a transmission rod, a signal generator, a data acquisition card, and a computer. By setting the rotary drive assembly and the linear drive assembly, the test device can control the rotation of the transmission rod and its movement in the vertical direction, and transmit the acting force to the superconducting sample through the transmission rod to achieve the stretching and torsion of the superconducting sample, thereby realizing the measurement of the effective strain state of the superconducting sample under different tensile and torsional strains in real time. The device provided by the present invention is applicable to real-time measuring the AC susceptibility signal of a superconducting sample with temperature under different torsional angles and tensile conditions, and calculating the effective strain state of the superconducting sample through subsequent algorithms, which is more convenient and efficient compared with other detection methods.

Description

Technical Field

[0001] The present invention relates to the field of superconducting electronics, and particularly relates to a measuring device and method for real-time detecting the effective strain state of a superconducting sample under different tensile and torsional strains. Background Art

[0002] Fusion energy, as an efficient clean energy, its use is one of the ultimate dreams of mankind. The all-superconducting tokamak magnetic confinement fusion device is an important guarantee for the continuous operation of a fusion reactor to generate fusion energy. While actively carrying out the construction work of the International Thermonuclear Experimental Reactor (ITER), countries are also simultaneously engaged in the design and development of future fusion reactors. However, future fusion reactors will all face the significant characteristics of high working magnetic fields and high operating currents, and the maximum magnetic fields of their central solenoid coils and toroidal field coils will all exceed 12 T. Considering factors such as technical reliability and industrial feasibility, the currently relatively successful superconducting materials are the low-temperature superconducting material - high-performance Nb 3 Sn superconducting wire and the high-temperature superconducting material - YBCO superconducting tape. These two materials have made good progress in their corresponding low-temperature and high-temperature superconducting fields in terms of performance testing, conductor development, and industrial production.

[0003] To meet the winding of high-field magnets, second-generation high-temperature superconducting tapes such as YBCO are usually wound into cable conductors in the form of CORC cables or CICC (Cable in the conduit conductor) conductors. Since high-temperature superconducting samples are stacked by multiple layers of materials such as copper layers, buffer layers, superconducting layers, and substrates, they have significant anisotropy in macroscopic electromagnetic properties. When they are wound into CORC cables and conductors, the samples will inevitably be subjected to tensile and torsional forces, which will lead to an irreversible decline in current-carrying performance, resulting in serious damage and distributed cracks in the superconducting layers of high-temperature superconducting samples. And high-performance Nb 3As an A15-type intermetallic compound, Sn superconducting wire is very fragile after heat treatment and phase formation, and is very sensitive to strain. The CICC conductor made thereof will also be subjected to tensile strain and torsional strain under electromagnetic operating conditions, resulting in irreversible changes in current-carrying performance. At present, the structural damage detection of superconducting samples is all destructive dissection, which may cause secondary damage to the samples and make it impossible to detect their true strain conditions. Moreover, the shapes of the samples after winding are various and cannot be in a flat state without strain, which greatly reduces the means for detecting the sample structure. In terms of non-destructive detection technology, neutron diffraction has a high measurement accuracy, but its measurement cost is too high and the measured samples are radioactive and difficult to retrieve. The alternating current susceptibility measurement method can perform non-destructive detection of the performance of superconducting samples, with low cost and no radiation effect. The alternating current susceptibility signal and temperature signal data collected by it can be post-processed into the effective strain state of the superconducting sample to characterize the true performance of the superconducting sample. Therefore, developing a device that can measure the effective strain state of superconducting samples under different degrees of tensile and torsional strain in real time is one of the important detection methods for characterizing the performance degradation of superconducting samples.

[0004] In order to accurately measure the effective strain state of a superconducting sample, the volume of the sample to be measured needs to be large enough (>60 cubic millimeters) to meet its true strain state. At present, there is no effective strain state measurement technology for superconducting samples in China, let alone an effective strain measurement technology that can measure the effective strain after the sample is stretched to a certain extent or twisted by a certain angle in real time. Moreover, the current alternating current susceptibility measurement device can only meet the requirements of small-volume or even powdered samples to be measured, and cannot meet the test requirements for actual superconducting samples. Summary of the Invention

[0005] To solve the deficiencies in the prior art, the present invention proposes a measurement device and method for real-time detecting the effective strain state of superconducting samples under different tensile and torsional strains, which is applicable to real-time measuring the alternating current susceptibility signal of large-volume superconducting samples with temperature at different torsional angles, and calculating the effective strain state of the superconducting samples through subsequent algorithms.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A measuring device for real-time detecting the effective strain state of a superconducting sample under different tensile and torsional strains, comprising: a cryogenic dewar, in which a heater and a coil group are placed, the coil group is located inside the heater and fixedly connected to the heater; preferably, the coil group and the heater are coaxially arranged, and the bottom of the coil group is fixedly connected to the heater. The heater is connected to a temperature controller, and a temperature sensor is installed on the coil group; the outlet end of the cryogenic dewar is connected to a sample rod with a hollow structure, the inside of the sample rod is communicated with the inside of the cryogenic dewar, and a transmission rod is axially penetrated through the inside of the sample rod, and the transmission rod is used to fix the top of the superconducting sample; the transmission rod is connected with a rotary drive assembly for driving its rotation and a linear drive assembly for driving its movement in the vertical direction; the sample rod is connected with a vacuum pump and a gas pump for controlling the gas environment in the cryogenic dewar; the coil group is connected with a signal generator and a data acquisition card; both the temperature controller and the data acquisition card are signal-connected to a computer; wherein:

[0008] The coil group is used to fix the bottom of the superconducting sample and receive the alternating current signal provided by the signal generator, and generate a magnetic susceptibility signal;

[0009] The signal generator is used to provide an alternating current signal for the coil group;

[0010] The data acquisition card collects the magnetic susceptibility signal generated by the coil group and performs phase-locked amplification processing;

[0011] The computer is used to obtain the magnetic susceptibility signal and temperature signal from the data acquisition card and the temperature controller.

[0012] Further solution: The coil group includes coils and a coil bobbin for winding the coils; the coils include an exciting coil, a pickup coil, and a compensation coil; the coil bobbin includes an exciting coil bobbin for winding the exciting coil, and a pickup coil and a compensation coil bobbin fixed inside the exciting coil bobbin; the pickup coil and the compensation coil bobbin are fixedly connected to the exciting coil bobbin, and the exciting coil bobbin is fixedly connected to the heater. The pickup coil and the compensation coil bobbin include an upper connecting section, a middle section, and a lower connecting section. The pickup coil and the compensation coil are respectively wound on the upper connecting section and the lower connecting section. The upper connecting section, the middle section, and the lower connecting section can be connected to each other as an integral structure through a connection method of internal and external threads. The form of threaded connection facilitates the assembly between sections and also facilitates its own replacement; the inside of the upper connecting section is a hollow sample cavity for accommodating a superconducting sample; the upper end inside the middle section has a positioning cavity communicating with the sample cavity, and a positioning groove for fixing the superconducting sample is provided at the bottom of the positioning cavity inside the middle section; an installation groove for installing a temperature sensor is provided on the outer side wall of the middle section; signal wire grooves are provided around the outer sides of the pickup coil and the compensation coil bobbin, facilitating the arrangement of signal wires such as the pickup coil, the compensation coil, and the temperature sensor, and preventing damage to the signal wires during assembly and testing. The measurement device provided by the present invention meets the effective strain test requirements of superconducting sub-cables composed of superconducting tapes with large volume and width-to-thickness ratio and first / second-level superconducting strands. By designing the sample cavity as a large-diameter sample cavity to accommodate the required test samples. And as the volume of the sample cavity increases, the number of turns and wire diameter of the coils are correspondingly increased. The test device provided by the present invention can perform effective strain tests on various superconducting materials and small superconducting sub-cables, and has a wide range of applications.

[0013] Further solution: The rotary drive assembly includes a servo motor. The output end of the servo motor is connected with a driving wheel, and the driving wheel is meshed and driven with a driven wheel. A connecting rod passes through the central axis position of the driven wheel, and the connecting rod and the driven wheel are connected through gears, and the connecting rod can move relative to the driven wheel in the vertical direction. The connecting rod is connected to the transmission rod through a coupling; an external gear is provided on the outside of the connecting rod, and a through hole is provided at the central axis position of the driven wheel, and a gear groove adapted to the external gear is provided inside the through hole. The gear transmission between the connecting rod and the driven wheel is realized through the cooperation of the external gear and the gear groove. When the driven wheel rotates, it can drive the connecting rod to rotate synchronously;

[0014] The linear drive assembly includes a linear module, and the output end of the linear module is vertically downward; a weighing sensor is connected to the output end of the linear module, and a rotary stretching and separating component is connected below the weighing sensor; the rotary stretching and separating component includes an upper connecting portion for connecting with the weighing sensor and a lower connecting portion for connecting with a connecting rod, and the upper connecting portion and the lower connecting portion are detachably connected; the upper connecting portion and the lower connecting portion are connected by threads; a through first connection hole and a second connection hole are opened from top to bottom at the axis of the lower connecting portion, and the aperture of the first connection hole is larger than that of the second connection hole; the top of the connecting rod has a clamping head, and the outer diameter of the clamping head is smaller than the aperture of the first connection hole and larger than the aperture of the second connection hole, so that the clamping head can rotate freely in the first connection hole and can be clamped inside the lower connecting portion;

[0015] In a further aspect, a multi-hole connector is installed above the sample rod. The function of the multi-hole connector is to realize the connection between the sample rod and other external devices. The vacuum pump and the gas pump are both connected to the multi-hole connector through pipelines (so as to realize the connection with the sample rod and the inside of the cryogenic dewar); a micro-pressure reducing valve and a high-vacuum needle valve are installed at the gas outlet end of the gas pump. The function of the micro-pressure reducing valve is to reduce the helium pressure in the gas pump, and the function of the high-vacuum needle valve is to perform micro-control on the helium gas passing through the gas pump and decompressed by the micro-pressure reducing valve, so that the helium gas input into the cryogenic dewar can be accurately adjusted; an absolute pressure transmitter is installed in one connector of the multi-hole connector, which can measure the amount of helium gas input into the cryogenic dewar. In addition, other connectors in the multi-hole connector can also be used for the installation and arrangement of other signal lines in the measuring device.

[0016] In a further aspect, a Bragg fiber grating sensor is installed on the superconducting sample. This sensor can effectively measure the tensile strain of superconducting strands with a very small wire diameter in an extremely low temperature environment. Compared with traditional cryogenic strain gauges, it cannot be installed on superconducting strands for measurement. In addition, Bragg fiber gratings have very high test accuracy and electromagnetic interference resistance. In addition, arranging Bragg fiber gratings on superconducting wires and superconducting tapes can also detect the actual temperature of the sample to be measured, and cross-compare with the values displayed by the temperature sensors located on the coil skeleton.

[0017] The present invention also discloses a measurement method for real-time detecting the effective strain state of a superconducting sample under different tensile and torsional strains, which is completed by using the measurement device as described above, and includes the following steps:

[0018] Step 1: Check the fixing condition of the coils in the coil group and the protection condition of the lead-out ends to ensure that there is no bending or damage; if the coils are not firmly fixed and the lead-out ends are bent or broken, the coils need to be rewound;

[0019] Step 2: Weld one end of the superconducting sample inside the coil group and the other end inside the drive rod, ensuring that the superconducting sample is not interfered by external factors during welding to prevent changes in the initial strain state of the sample;

[0020] Step 3: By controlling the rotational drive assembly or the linear drive assembly, the drive rod can be twisted or stretched, thereby causing the superconducting sample to generate torsional or tensile strain;

[0021] Step 4: Place the cryogenic dewar in the liquid helium dewar and cool the internal cavity environment of the cryogenic dewar;

[0022] Step 5: Open the vacuum pump to evacuate the internal cavity of the cryogenic dewar, and ensure that the cavity is in a high vacuum state according to the reading shown on the molecular pump. Ensure that the gas pump is closed during evacuation;

[0023] Step 6: Open the gas pump, the micro-pressure reducing valve, the high-vacuum needle valve and the absolute pressure transmitter. Precisely control the helium gas in the gas pump through the micro-pressure reducing valve and the high-vacuum needle valve, so that there is an appropriate amount of helium gas in the cryogenic dewar under high vacuum state, ensuring uniform distribution of helium gas in the cavity and appropriate heat exchange rate;

[0024] Step 7: Turn on the temperature controller. The temperature controller reads the temperature signal through the temperature sensor placed near the sample and controls the temperature of the superconducting sample by adjusting the heater power;

[0025] Step 8: Turn on the signal generator and the data acquisition card. The alternating current signal is transmitted to the coil group through the signal generator. After the coil group induces the magnetic susceptibility signal, it is transmitted to the data acquisition card. The magnetic susceptibility signal is sent to the computer after being processed by the phase-locked amplification of the data acquisition card;

[0026] Step 9: Turn on the computer and start the Labview test software. At the same time, receive the magnetic susceptibility signal from the data acquisition card and the temperature signal from the temperature controller, and read the measurement data in real time and display the curves of the magnetic susceptibility signal and the temperature signal;

[0027] Step 10: The effective strain state of the sample can be obtained by post-processing the magnetic susceptibility matrix in the magnetic susceptibility-temperature curve drawn by the computer through the Tikonov regularization technique.

[0028] It should be noted that components such as the temperature sensor, the weighing sensor, the temperature controller, the signal generator, and the data acquisition card used in the present invention are all commercially available products and can be obtained through market purchase. For those skilled in the art, products with corresponding functions can be selected in the market according to needs.

[0029] Compared with the prior art, the beneficial effects of the present invention are:

[0030] The testing device provided by the present invention can achieve the rotational control and vertical movement control of the transmission rod by setting a rotational drive component and a linear drive component; and a rotational stretching and separating component is arranged between the rotational drive component and the linear drive component, which can separate the rotational movement of the connecting rod and the longitudinal movement in the vertical direction, making them not affect each other, and transmitting the acting force to the superconducting sample through the transmission rod to achieve the stretching and torsion of the superconducting sample, thereby realizing the measurement of the effective strain state of the superconducting sample under different stretching and torsion strains in real time. The device provided by the present invention is applicable to the real-time measurement of the AC susceptibility signal of a large-volume superconducting sample with temperature under different torsion angles and stretching conditions, and calculates the effective strain state of the superconducting sample through subsequent algorithms, which is more convenient and efficient compared with other detection methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the overall structure of the measuring device provided by the present invention;

[0032] Figure 2 It is an exploded view of the internal installation structure of the sample rod, the connecting rod and the cryogenic dewar;

[0033] Figure 3 It is a schematic diagram of the connection structure of the rotational drive component and the linear drive component;

[0034] Figure 4 It is an exploded view of the rotational drive component;

[0035] Figure 5 It is a perspective view of the rotational stretching and separating component;

[0036] Figure 6 It is a schematic diagram of the structure of the coil group;

[0037] Figure 7 It is an exploded view of the pick-up coil and the compensation coil skeleton;

[0038] Reference numerals: 1 - cryogenic dewar, 2 - heater, 3 - coil group, 301 - excitation coil, 302 - pickup coil, 303 - compensation coil, 304 - excitation coil skeleton, 305 - pickup coil and compensation coil skeleton, 3051 - upper connection section, 3052 - middle section, 3053 - lower connection section, 3054 - sample chamber, 3055 - positioning chamber, 3056 - positioning groove, 3057 - mounting groove, 3058 - signal wire groove, 4 - temperature controller, 5 - sample rod, 6 - transmission rod, 7 - rotary drive assembly, 701 - servo motor, 702 - driving wheel, 703 - driven wheel, 704 - connecting rod, 705 - external gear, 706 - gear groove, 707 - clamping joint, 8 - linear drive assembly, 801 - linear module, 802 - load cell, 803 - rotary stretching and separating component, 8031 - upper connection part, 8032 - lower connection part, 8033 - first connection hole, 8034 - second connection hole, 9 - vacuum pump, 10 - gas pump, 11 - signal generator, 12 - data acquisition card, 13 - computer, 14 - coupling, 15 - multi - hole joint, 16 - micro - pressure reducing valve, 17 - high - vacuum needle valve, 18 - absolute pressure transmitter, 19 - support plate. Detailed implementation manners

[0039] The following further illustrates the present invention with reference to embodiments, so that those skilled in the art can better understand the present invention and be able to implement it. However, the embodiments given are not intended to limit the present invention.

[0040] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "upper", "lower", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation of the present invention. In the present invention, the terms "first" and "second" do not represent specific quantities and sequences, but are only used for name distinction.

[0041] In the present invention, unless otherwise clearly defined and limited, the terms "installation", "connection", "connection", "fixation", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0042] Reference Figures 1 to 7, a measuring device for real-time detecting the effective strain state of a superconducting sample under different tensile and torsional strains, comprising: a cryogenic dewar 1, a heater 2 and a coil group 3 are placed inside the cryogenic dewar 1, the coil group 3 is located inside the heater and fixedly connected to the heater; preferably, the coil group 3 and the heater 2 are coaxially arranged, and the bottom of the coil group 3 is fixedly connected to the heater 2. The heater 2 is connected to a temperature controller 4, and a temperature sensor is installed on the coil group 3; the outlet end of the cryogenic dewar 1 is connected to a sample rod 5 with a hollow structure, the inside of the sample rod 5 is communicated with the inside of the cryogenic dewar 1, a transmission rod 6 is axially penetrated inside the sample rod 5, and the transmission rod 6 is used to fix the top of the superconducting sample; the transmission rod 6 is connected with a rotary drive assembly 7 for driving its rotation and a linear drive assembly 8 for driving its movement in the vertical direction; the sample rod 5 is connected with a vacuum pump 9 and a gas pump 10 for controlling the gas environment inside the cryogenic dewar 1; the coil group 3 is connected with a signal generator 11 and a data acquisition card 12; both the temperature controller 4 and the data acquisition card 12 are signal-connected to a computer 13. Among them:

[0043] The rotary drive assembly 7 includes a servo motor 701, the output end of the servo motor 701 is connected with a driving wheel 702, the driving wheel 702 is meshed and driven with a driven wheel 703, a connecting rod 704 is penetrated through the central axis position of the driven wheel 703, the connecting rod 704 and the driven wheel 703 are connected by gears, and the connecting rod 704 can move relative to the driven wheel 703 in the vertical direction, the connecting rod 704 is connected to the transmission rod 6 through a coupling 14; an external gear 705 is arranged outside the connecting rod 704, a through hole is opened at the central axis position of the driven wheel 703, and a gear groove 706 adapted to the external gear 705 is arranged inside the through hole. The gear transmission between the connecting rod 704 and the driven wheel 703 is realized through the cooperation of the external gear 705 and the gear groove 706, and when the driven wheel 703 rotates, the connecting rod 704 can be driven to rotate synchronously;

[0044] The linear drive assembly 8 includes a linear module 801, and the output end of the linear module 801 is vertically downward; a weighing sensor 802 is connected to the output end of the linear module 801, and a rotary stretching and separating component 803 is connected below the weighing sensor 802; the rotary stretching and separating component 803 includes an upper connecting portion 8031 for connecting with the weighing sensor 802 and a lower connecting portion 8032 for connecting with the connecting rod 704, and the upper connecting portion 8031 and the lower connecting portion 8032 are detachably connected; preferably, the upper connecting portion 8031 and the lower connecting portion 8032 are connected by threads; a through first connecting hole 8033 and a second connecting hole 8034 are opened vertically from top to bottom at the axis of the lower connecting portion 8032, and the aperture of the first connecting hole 8033 is larger than that of the second connecting hole 8034; the top of the connecting rod 704 has a clamping head 707, and the outer diameter of the clamping head 707 is smaller than the aperture of the first connecting hole 8033 and larger than the aperture of the second connecting hole 8034, so that the clamping head 707 can freely rotate in the first connecting hole 8033 and can be clamped inside the lower connecting portion 8032.

[0045] As a specific implementation manner, a support plate 19 is vertically fixed above the transmission rod 6, and the servo motor 701 and the linear module 801 are both installed on the support plate 19.

[0046] The coil group 3 is used to fix the bottom of the superconducting sample and receive the alternating current signal provided by the signal generator 11, and generate a magnetic susceptibility signal; its structure refers to Figure 6 and Figure 7, the coil group 3 includes coils and a coil bobbin for winding the coils; the coils include an exciting coil 301, a pickup coil 302, and a compensation coil 303, and these coils are all wound with enameled pure copper wire that can shield external signals. The coils are protected by epoxy impregnation fixation and a hollow plastic tube is sleeved on the lead-out copper wire end to prevent damage to the copper wire lead-out end; the coil bobbin includes an exciting coil bobbin 304 for winding the exciting coil 301 and a pickup coil and compensation coil bobbin 305 fixed inside the exciting coil bobbin 304; the pickup coil 302 and the compensation coil 303 bobbins are fixedly connected to the exciting coil bobbin 304, and the exciting coil bobbin 304 is fixedly connected to the heater 2; there is no need to fix between the conventional coil bobbin and the heater because their relative positions do not change during the test. However, in the present invention, in order to cooperate with the linear drive assembly 8 and the rotary drive assembly 7 to apply tensile and torsional drives to the superconducting sample, it is necessary to keep the other end of the superconducting sample fixed in order to achieve the purpose of stretching and twisting the superconducting sample. Specifically, the fixing connection between them can be achieved by respectively opening threaded holes at the bottom of the pickup coil and compensation coil bobbin, the bottom of the exciting coil bobbin, and the bottom of the heater, and installing connecting bolts in the threaded holes. The pickup coil and compensation coil bobbin 305 includes an upper connecting section 3051, a middle section 3052, and a lower connecting section 3053. The pickup coil 302 and the compensation coil 303 are respectively wound on the upper connecting section 3051 and the lower connecting section 3053. The upper connecting section 3051, the middle section 3052, and the lower connecting section 3053 can be connected to each other as an integral structure through the connection method of internal and external threads. The form of threaded connection facilitates the assembly between each section and also facilitates its own replacement; the inside of the upper connecting section 3051 is a hollow sample cavity 3054, and the inner diameter of the sample cavity can be 13 mm for accommodating the superconducting sample; the upper end inside the middle section 3052 has a positioning cavity 3055 communicating with the sample cavity 3054, and a positioning groove 3056 for fixing the superconducting sample is opened at the bottom of the middle section 3052 inside the positioning cavity 3055. During the experiment, the bottom of the test sample can be fixed in the positioning groove 3056 by welding or adhesive bonding. The shape of the positioning groove 3056 can be designed according to the actual test product. For example, a circular groove can be opened to facilitate the placement of superconducting strands, a triangular groove can be opened to facilitate the placement of first-level superconducting cables, and a polygonal groove can be opened for the placement of multi-level cables; an installation groove 3057 for installing a temperature sensor is opened on the outer side wall of the middle section 3052; signal wire grooves 3058 are opened around the outside of the pickup coil and compensation coil bobbin 305 to facilitate the arrangement of signal wires such as the pickup coil 302, the compensation coil 303, and the temperature sensor, and prevent damage to the signal wires during assembly and testing.

[0047] A signal generator 11 for providing an alternating current signal to the coil group 3;

[0048] The data acquisition card 12 collects the magnetic susceptibility signals generated by the coil set 3 and performs phase-locked amplification processing;

[0049] The computer 13 is used to obtain the magnetic susceptibility signals and temperature signals from the data acquisition card 12 and the temperature controller.

[0050] As a preferred embodiment, a porous joint 15 is installed above the sample rod 5. The drive rod passes through the inside of the porous joint. Both ends of the porous joint are sealed through some conventional seals to prevent air leakage at the connection between the porous joint and the sample rod and at the connection between the porous joint and the drive rod. The function of the porous joint is to connect the sample rod with other external devices. The vacuum pump 9 and the gas pump 10 are both connected to the porous joint 15 through pipelines, so as to achieve communication with the sample rod 5 and the inside of the cryogenic dewar 1; a micro-pressure reducing valve 16 and a high-vacuum needle valve 17 are installed at the gas outlet end of the gas pump 10. The function of the micro-pressure reducing valve 16 is to reduce the helium pressure in the gas pump 10, and the function of the high-vacuum needle valve 17 is to perform micro-control on the helium gas passing through the gas pump 10 and decompressed by the micro-pressure reducing valve 16, so that the helium gas input into the cryogenic dewar 1 can be accurately adjusted; an absolute pressure transmitter 18 is installed in one joint of the porous joint 15, which can measure the amount of helium gas input into the cryogenic dewar 1. In addition, other joints in the porous joint can also be used for the installation and arrangement of other signal lines in the measuring device, which is convenient for leading out the signal lines inside the device, so as to connect external devices such as computers with the internal structure of the device.

[0051] As another embodiment, a Bragg fiber grating sensor is installed on the superconducting sample. This sensor can effectively measure the tensile strain of superconducting strands with a very small wire diameter in an extremely low temperature environment. Compared with traditional cryogenic strain gauges, they cannot be installed on superconducting strands for measurement. In addition, the Bragg fiber grating has very high test accuracy and anti-electromagnetic interference. And arranging the Bragg fiber grating on superconducting wires and superconducting tapes can also detect the actual temperature of the sample to be measured, and cross-compare with the values displayed by the temperature sensors located on the coil skeleton to improve the measurement accuracy.

[0052] The present invention also discloses a measurement method for real-time detecting the effective strain state of a superconducting sample under different tensile and torsional strains, which is completed by using the measuring device as described above, and includes the following steps:

[0053] Step 1: Check the fixing condition of the coils in the coil set and the protection condition of the lead-out ends to ensure that there is no bending or damage; if the coils are not firmly fixed and the lead-out ends are bent or broken, the coils need to be rewound;

[0054] Step 2: Weld one end of the superconducting sample inside the coil group and the other end inside the drive rod, ensuring that the superconducting sample is not interfered by external factors during welding to prevent changes in the initial strain state of the sample;

[0055] Step 3: By controlling the rotational drive assembly or the linear drive assembly, the drive rod can be twisted or stretched, thereby causing the superconducting sample to generate torsional or tensile strain;

[0056] Step 4: Place the cryogenic dewar in the liquid helium dewar and cool the internal cavity environment of the cryogenic dewar;

[0057] Step 5: Open the vacuum pump to evacuate the internal cavity of the cryogenic dewar, and ensure that the inside of the cavity is in a high vacuum state according to the reading shown on the molecular pump. Ensure that the gas pump is closed during evacuation;

[0058] Step 6: Open the gas pump, the micro-pressure reducing valve, the high-vacuum needle valve and the absolute pressure transmitter. Precisely control the helium gas in the gas pump through the micro-pressure reducing valve and the high-vacuum needle valve, so that the cryogenic dewar in the high-vacuum state has an appropriate amount of helium gas, ensuring uniform distribution of helium gas in the cavity and an appropriate heat exchange rate;

[0059] Step 7: Turn on the temperature controller. The temperature controller reads the temperature signal through the temperature sensor placed near the sample and controls the temperature of the superconducting sample by adjusting the power of the heater;

[0060] Step 8: Turn on the signal generator and the data acquisition card. The alternating current signal is transmitted to the coil group through the signal generator. After the coil group induces the magnetic susceptibility signal, it is transmitted to the data acquisition card. The magnetic susceptibility signal is sent to the computer after being processed by the phase-locked amplification of the data acquisition card.

[0061] Step 9: Turn on the computer and start the Labview test software. At the same time, receive the magnetic susceptibility signal from the data acquisition card and the temperature signal from the temperature controller, and read the measurement data in real time and display the curves of the magnetic susceptibility signal and the temperature signal;

[0062] Step 10: The effective strain state of the sample can be obtained by post-processing the magnetic susceptibility matrix in the magnetic susceptibility-temperature curve drawn by the computer through the Tikonov regularization technique.

[0063] Obviously, the described embodiments are part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Claims

1. A measuring device for real-time detecting the effective strain state of a superconducting sample under different tensile and torsional strains, characterized in that, it includes: A cryogenic dewar, in which a heater and a coil group are placed. The coil group is located inside the heater and fixedly connected to the heater. The heater is connected to a temperature controller, and a temperature sensor is installed on the coil group. The outlet end of the cryogenic dewar is connected to a sample rod with a hollow structure. The inside of the sample rod is communicated with the inside of the cryogenic dewar. A transmission rod is axially penetrated through the inside of the sample rod, and the transmission rod is used to fix the top of the superconducting sample. The transmission rod is connected with a rotary drive assembly for driving its rotation and a linear drive assembly for driving its movement in the vertical direction. The sample rod is connected with a vacuum pump and a gas pump. The coil group is connected with a signal generator and a data acquisition card. Both the temperature controller and the data acquisition card are signal-connected to a computer. Among them: The coil group is used to fix the bottom of the superconducting sample and receive the alternating current signal provided by the signal generator, and generate a magnetic susceptibility signal; The signal generator is used to provide an alternating current signal for the coil group; The data acquisition card collects the magnetic susceptibility signal generated by the coil group and performs phase-locked amplification processing; The computer is used to obtain the magnetic susceptibility signal and temperature signal from the data acquisition card and the temperature controller; The rotary drive assembly includes a servo motor. The output end of the servo motor is connected with a driving wheel, and the driving wheel is meshed and driven with a driven wheel. A connecting rod is penetrated through the central axis position of the driven wheel. The connecting rod and the driven wheel are connected by a gear, and the connecting rod can move relative to the driven wheel in the vertical direction. The connecting rod is connected directly above the transmission rod; The linear drive assembly includes a linear module, and the output end of the linear module is vertically downward. The output end of the linear module is connected with a load cell, and a rotary and tensile separation component is connected below the load cell. The rotary and tensile separation component includes an upper connecting part for connecting with the load cell and a lower connecting part for connecting with the connecting rod. The upper connecting part and the lower connecting part are detachably connected. A through first connecting hole and a second connecting hole are opened from top to bottom at the axis center of the lower connecting part. The aperture of the first connecting hole is larger than that of the second connecting hole. The top of the connecting rod has a clamping head, and the outer diameter of the clamping head is smaller than the aperture of the first connecting hole and larger than the aperture of the second connecting hole, so that the clamping head can freely rotate in the first connecting hole and can be clamped inside the lower connecting part.

2. The measuring device for real-time detecting the effective strain state of a superconducting sample under different tensile and torsional strains according to claim 1, characterized in that: The connecting rod and the transmission rod are connected by a coupling.

3. The measuring device for real-time detecting the effective strain state of a superconducting sample under different tensile and torsional strains according to claim 1, characterized in that: The outside of the connecting rod has an external gear, and a through hole is opened at the central axis position of the driven wheel. The inside of the through hole has a gear groove adapted to the external gear.

4. The measuring device for real-time detecting the effective strain state of a superconducting sample under different tensile and torsional strains according to claim 1, characterized in that: a porous joint is installed above the sample rod, and the vacuum pump and the gas pump are both connected to the porous joint through pipelines; a micro-pressure reducing valve and a high-vacuum needle valve are installed at the gas outlet end of the gas pump; an absolute pressure transmitter is installed in one joint of the porous joint.

5. The measuring device for real-time detecting the effective strain state of a superconducting sample under different tensile and torsional strains according to claim 1, characterized in that: the coil group includes coils and a coil skeleton for winding the coils; the coils include an exciting coil, a pick-up coil and a compensation coil; the coil skeleton includes an exciting coil skeleton for winding the exciting coil and a pick-up coil and a compensation coil skeleton fixed inside the exciting coil skeleton; the pick-up coil and the compensation coil skeleton are fixedly connected to the exciting coil skeleton, and the exciting coil skeleton is fixedly connected to the heater; the pick-up coil and the compensation coil skeleton include an upper connecting section, a middle section and a lower connecting section, and the pick-up coil and the compensation coil are respectively wound on the upper connecting section and the lower connecting section; the inside of the upper connecting section is a hollow sample cavity; the upper end inside the middle section has a positioning cavity communicated with the sample cavity, and a positioning groove for fixing the superconducting sample is opened at the bottom of the positioning cavity inside the middle section; an installation groove for installing a temperature sensor is opened on the outer side wall of the middle section; signal wire grooves are opened around the outer side of the pick-up coil and the compensation coil skeleton.

6. The measuring device for real-time detecting the effective strain state of a superconducting sample under different tensile and torsional strains according to claim 1, characterized in that: a Bragg fiber grating sensor is installed on the superconducting sample.

7. A measuring method for real-time detecting the effective strain state of a superconducting sample under different tensile and torsional strains, characterized in that: it is completed by using the measuring device according to any one of claims 1 to 6, and includes the following steps: Step 1: Check the fixing condition of the coils in the coil group and the protection condition of the lead-out ends to ensure that there is no bending and damage; if the coils are not firmly fixed and the lead-out ends are bent and broken, the coils need to be rewound; Step 2: Weld one end of the superconducting sample inside the coil group and the other end inside the driving rod, and ensure that the superconducting sample is not interfered by external factors during welding to prevent the initial strain state of the sample from changing; Step 3: By controlling the rotary drive assembly or the linear drive assembly, the driving rod can be twisted or stretched, so that the superconducting sample generates torsional or tensile strain; Step 4: Place the cryogenic dewar in the liquid helium dewar and cool the inner cavity environment of the cryogenic dewar; Step 5: Open the vacuum pump to evacuate the inner cavity of the cryogenic dewar, and ensure that the inside of the cavity is in a vacuum state according to the reading shown on the molecular pump. When evacuating, ensure that the gas pump is closed; Step 6: Turn on the gas pump, the micro-pressure reducing valve, the high-vacuum needle valve and the absolute pressure transmitter. Precisely control the helium gas in the gas pump through the micro-pressure reducing valve and the high-vacuum needle valve, so that there is an appropriate amount of helium gas in the cryogenic dewar under vacuum state, ensuring that the helium gas in the cavity is evenly distributed and the heat exchange rate is appropriate; Step 7: Turn on the temperature controller. The temperature controller reads the temperature signal through the temperature sensor placed near the sample and controls the temperature of the superconducting sample by adjusting the heater power; Step 8: Turn on the signal generator and the data acquisition card. Transmit the alternating current signal to the coil group through the signal generator. After the coil group induces the magnetic susceptibility signal, it is transmitted to the data acquisition card. The magnetic susceptibility signal is sent to the computer after being processed by the phase-locked amplification of the data acquisition card; Step 9: Turn on the computer and start the Labview test software. At the same time, receive the magnetic susceptibility signal from the data acquisition card and the temperature signal from the temperature controller, read the measurement data in real time and display the curves of the magnetic susceptibility signal and the temperature signal; Step 10: The effective strain state of the sample can be obtained by post-processing the magnetic susceptibility matrix in the magnetic susceptibility-temperature curve drawn by the computer through the Tikonov regularization technique.

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