Device for detecting micron-sized cracks of in-pile material at high temperature and high pressure

Abstract

The invention provides a device for detecting micron-sized cracks of in-pile materials at high temperature and high pressure. The device comprises a sealing head, a gas circuit pipeline, a top cover, an outer sleeve, a double-layer corrugated pipe, a bottom cover, a CT sample block, a pressure sensor placing device and a stress rod, the double-layer corrugated pipe is connected with a gas circuit pipeline, a sealing head is installed on the gas circuit pipeline, a top cover is installed between the first corrugated pipe and the gas circuit pipeline, one end of the second corrugated pipe is connected with a stress rod, a bottom cover is installed between the second corrugated pipe and the stress rod, the stress rod is provided with a detection end fixing hole and an open space, and a CT sample block is located in the open space. The pressure sensor placing device is installed on the CT sample block, the load under the actual application condition can be simulated, the size of the sample crack can be directly detected through direct current potential reduction, and the precision reaches the micron level; all parameter signals are transmitted to an upper computer end through serial port communication to be displayed, and parameters such as crack size change, device temperature, device pressure and excitation signal size are monitored in real time.

Description

Technical Field

[0001] The present invention belongs to the field of crack detection of in-pile environmental materials in a nuclear radiation environment under high temperature and high pressure conditions, and specifically relates to a micron-level crack detection device for in-pile materials under high temperature and high pressure conditions. Background Art

[0002] With the increasing number of nuclear power plants being built, the safety of nuclear power plants is of vital importance. According to research, most nuclear safety accidents are caused by nuclear leakage from nuclear reactors and pressure vessels. Among them, fatigue failure of important mechanical equipment such as nuclear power pressure vessels is one of the major safety hazards.

[0003] In the containers of nuclear radiation reactors, the materials, welding materials and processes used in different welding parts are all different. The welded structure not only has unstable mechanical properties, but also has residual stress in welding and metallurgical defects such as cracks, pores and inclusions. Especially when the components are in a high-temperature and high-pressure water environment for a long time, it is easy for the welded joints to become weak locations where cracks grow and defects occur. In the actual operation of nuclear power plants, stress corrosion cracking (SCC) is a representative, which reduces the design life and safety performance of nuclear power equipment, and is a problem that we urgently need to solve.

[0004] The suddenness and concealment of SCC crack extension pose a great threat to the safety, economy and service life of nuclear power plants. So far, domestic research on stress corrosion cracking of materials under irradiation conditions is based on the inspection and analysis of materials after irradiation tests in reactors. The results obtained are the final amount of changes in the material's cumulative physical environment, mechanical properties and organizational structure. It is difficult to determine the synergistic effect of the in-core irradiation environment and SCC influencing factors, as well as the process evolution law of materials closely related to time, stress load and irradiation environment.

[0005] The device of the present invention can simulate and observe the crack evolution process in the irradiation environment in the pile, carry out the online measurement technology research of SCC crack extension in the irradiation test process through the high temperature and high pressure device, and develop the SCC crack extension online measurement instrument standardization device and system, which can detect the micron-level crack length in the nuclear radiation environment. It includes the following structures: double-layer bellows, force load transmission mechanism, prefabricated crack CT specimen, pressure sensor, gas pipeline, fixed gasket, high temperature pressure adapter block, center guide rod, center rod guide end cap, welding thread head, support ring, tightening nut M4, single-layer casing, etc. Summary of the invention

[0006] In order to solve the above technical problems, the present invention proposes a micron-level crack detection device for in-pile materials under high temperature and high pressure, which can fully simulate the high temperature and high pressure environment under a nuclear radiation environment. Through the material tension control unit, the loading mechanism applies a constant tension or pressure to the material to be tested, simulating the load under actual application conditions. Through the direct current potential drop (DCPD), the size of the sample crack can be directly detected with an accuracy of micron level; all parameter signals are transmitted to the host computer for display through serial port communication, and parameters such as changes in crack size, device temperature, device pressure and the size of the excitation signal are monitored in real time. The host computer operation interface is simple and the human-computer interaction is friendly.

[0007] To achieve the above object, the technical solution adopted by the present invention is: A device for detecting micron-level cracks in a pile material under high temperature and high pressure, characterized in that it comprises a sealing head, an air pipeline, a top cover, a double-layer bellows, a bottom cover, a CT specimen block, a pressure sensor placement device and a stress-bearing rod, the double-layer bellows comprises a first bellows and a second bellows, the first bellows is connected and fixed to the second bellows, one end of the first bellows is connected to the air pipeline, a sealing head is installed on the air pipeline, a top cover is installed between the first bellows and the air pipeline, one end of the second bellows is connected to the stress-bearing rod, a bottom cover is installed between the second bellows and the stress-bearing rod, a detection end fixing hole and an open space are provided on the stress-bearing rod, the CT specimen block is located in the open space on the stress-bearing rod, and the CT specimen block is A rectangular structure is provided with a prefabricated crack from its upper end to the middle part, the CT specimen block is provided with a first excitation part and a second excitation part, the prefabricated crack is provided with a first voltage detection part and a second voltage detection part, the first excitation part and the second excitation part are respectively connected with an excitation wire, the first voltage detection part and the second voltage detection part are connected with a detection wire, the excitation wire and the detection wire do not interfere with each other, the excitation wire and the detection wire are led out through the gas pipeline, and data is obtained and displayed on the upper computer. When inflating or deflation is performed through the gas pipeline, the first bellows and the second bellows push the CT specimen block to generate pressure, and a load force can be generated on the specimen at this time. At this time, the specimen can be excited and detected through the excitation wire and the detection wire. The pressure sensor placement device is installed on the CT specimen block, a pressure sensor is installed on the pressure sensor placement device, a fixing hole is also opened on the pressure sensor placement device, a thermocouple is installed in the fixing hole, the detection end of the thermocouple is fixed in the detection end fixing hole, the thermocouple and the pressure sensor do not interfere with each other, the thermocouple is connected to an electric couple wire, the electric couple wire is led out through an air pipeline, and data is obtained and displayed on the host computer.

[0008] In the above structure: the present invention proposes a micron-level crack detection device for in-pile materials under high temperature and high pressure, including a sealing head, an air pipeline, a top cover, a double-layer bellows, a bottom cover, a CT specimen block, a pressure sensor placement device and a stress rod. The sealing head is used to seal the air pipeline. The air pipeline can not only be used to realize inflation and deflation, but also can lead out the excitation signal (two excitation wires), voltage signal (two detection wires) and thermocouple (two thermocouple wires) of the CT specimen block, so as to obtain data to be displayed on the upper computer. The top cover at the front end and the bottom cover at the rear end are used to achieve sealing between the gas pipeline and the first bellows, the second bellows and the stress-bearing rod, ensuring the airtightness of the device and providing more comprehensive protection for the entire device. It can protect the internal components from the influence of the external environment, such as dust, moisture, corrosive gases in the air, etc. When welding the top cover, full welding is adopted at both ends.

[0009] Double-layer bellows is a metal pipe with a corrugated shape, usually made of materials such as stainless steel or copper. The first bellows and the second bellows act as a connecting device to transmit the external load force to the regulating device. When the external load force acts on the first bellows and the second bellows, the medium (nitrogen) in the two bellows will also be subject to corresponding pressure changes and transmitted to other parts of the device, thereby achieving the regulation of the load force. The elastic deformation of the two bellows is very sensitive to pressure changes, which can achieve precise regulation and control of the load force.

[0010] The CT specimen block is a rectangular structure, with a prefabricated crack arranged from its upper end to the middle part. The CT specimen block is provided with a first excitation part and a second excitation part, and a first voltage detection part and a second voltage detection part are arranged in the prefabricated crack. The first excitation part and the second excitation part are respectively connected with excitation wires, and the first voltage detection part and the second voltage detection part are connected with detection wires. The excitation wires and detection wires connected to the CT specimen block need to be bent 90° to the left or right so that the two cannot interfere with each other. The excitation wires and detection wires are led out through the air pipeline, and data is obtained and displayed on the upper computer. When inflating or deflation is performed through the air pipeline, the first bellows and the second bellows push the CT specimen block to generate pressure, and at this time, a load force can be generated on the specimen. At this time, the excitation wire and the detection wire can be used to excite and detect the specimen.

[0011] CT specimen (Compacted Tension, CT), also known as compact tensile specimen, is one of the standard specimen shapes used to study the crack growth behavior and fracture toughness of materials. It is rectangular with a central notch or pre-crack.

[0012] In the device of the present invention, a first excitation part, a second excitation part, a first voltage detection part and a second voltage detection part are respectively provided on the CT specimen block, an excitation signal is passed into the first excitation part and the second excitation part, a constant current is passed, the voltage is set to 1V, the current is set to 1A, and the DC voltage source is in a constant current mode; the voltage is detected at the first voltage detection part and the second voltage detection part. According to the DCPD algorithm, when the current passing through the specimen is constant, the voltage at both ends of the crack on the specimen will increase with the increase of the crack length, and the crack value can be obtained by the voltage.

[0013] The stress rod is used to realize the installation and fixation of the CT specimen block and the fixation of the thermocouple detection end. The stress rod can make the CT specimen block have better load bearing capacity. By slow wire walking, pre-cracks are pre-made at the pre-crack location. The minimum crack length is 5um and the maximum crack length is 6mm.

[0014] The pressure sensor placement device is installed on the CT specimen block. The pressure sensor is installed on the pressure sensor placement device. The thermocouple can be placed in the opening of the pressure sensor without interfering with its use. The detection end of the thermocouple is fixed in the detection end fixing hole. The thermocouple is connected with an electric couple wire, which is led out through an air pipeline to obtain data and display it on the host computer.

[0015] This device is used in conjunction with "A High-Pressure Gas Regulating System Device Based on Stress Corrosion Cracking". The first connecting seat and the second connecting seat on the "A High-Pressure Gas Regulating System Device Based on Stress Corrosion Cracking" correspond to tooling in different environments. Taking the second connecting seat as an example, the four holes are used to inflate and deflate the two interlayers of the bellows. The two small holes at 0° and 90° in the clockwise direction of the second connecting seat are used to inflate the inner interlayer of the bellows, the 180° small hole in the clockwise direction is used to inflate the outer interlayer, and the other hole is for collecting and discarding the entire device. For detailed contents of the high-pressure gas regulating system device, please refer to the patent "A High-Pressure Gas Regulating System Device Based on Stress Corrosion Cracking". The first connecting seat is used to inflate another set of tooling.

[0016] In order to ensure the sealing of the electric heating element, the thermocouple and the signal cable, the present invention adds a sealing element, which is mainly composed of a sealing head joint, a sealing head gasket, a sealing head sealing pad, a sealing head gland and a sealing head nut.

[0017] The sealing head gasket includes a Teflon sealing ring, which is located between the joint and the sealing head to provide additional sealing and protection. It can fill the gap between the contact surfaces and ensure the tightness of the seal. There are 8 3.5mm through holes on the rings with a radius of 50mm and 57mm.

[0018] It also includes a fixed gasket, which is located between the joint and the sealing head to provide additional sealing and protection. It can fill the gap between the contact surfaces and ensure the tightness of the seal.

[0019] These sealing heads and their components can effectively protect the electric heating elements, thermocouples and signal cables inside the device and ensure the required sealing in the air environment test device. Such a design can prevent interference from the external environment, provide stable test conditions, and ensure accurate measurement and data acquisition.

[0020] As a preferred technical solution of the present invention: it also includes an outer sleeve, which is provided with an opening, and includes a shell wall and a shell cover, the first corrugated tube is installed in the opening, and the shell cover is connected to the top cover.

[0021] In the above structure, in order to make the device operate normally in an air environment, the entire device is placed in the enclosure of an extended outer sleeve to protect the first bellows from the influence of the external environment, such as dust, moisture, corrosive gases, etc. in the air.

[0022] As a preferred technical solution of the present invention: it also includes a first end cover, a second end cover and a center guide rod, the first end cover is installed at one end of the first corrugated tube, the end of the center guide rod is fixed on the first end cover, the second corrugated tube is sleeved on the center guide rod, and the second end cover is installed at the end of the second corrugated tube.

[0023] In the above structure: the first end cover is used to realize the installation of the central guide rod, and the installation and fixation of the second bellows are realized through the central guide rod and the second end cover.

[0024] As a preferred technical solution of the present invention: it also includes a sealing end cover, which is installed on the opening of the outer sleeve, and a through hole is provided on the sealing end cover, and the central guide rod is arranged through the sealing end cover.

[0025] In the above structure: a sealing end cover is installed on the opening of the outer sleeve, which can achieve sealing between the outer sleeve and the second bellows to prevent air leakage.

[0026] As a preferred technical solution of the present invention: the gas circuit pipeline includes a stainless steel tube and a sample outlet, the top cover includes a first concentric circular tube and a second concentric circular tube, the first concentric circular tube and the second concentric circular tube are respectively provided with mounting through holes, the stainless steel tube and the sample outlet are respectively installed in the mounting through holes, and the excitation line and the detection line are respectively located in the sample outlet.

[0027] In the above structure: the stainless steel tube is used to realize the inflation and deflation of the device, the top cover is composed of two concentric first concentric circular tubes and a second concentric circular tube, the stainless steel tube and the sample outlet are respectively installed in the installation through hole, and the sample outlet is used to realize the lead-out of the excitation line and the detection line to facilitate data acquisition.

[0028] As a preferred technical solution of the present invention: the force-bearing rod includes a force-bearing block and a connecting block, the force-bearing block includes two concave first force-bearing blocks and a second force-bearing block, the first force-bearing block and the second force-bearing block are connected by the connecting block, the first force-bearing block and the second force-bearing block are respectively provided with a first connecting hole and a second connecting hole, the detection end fixing hole is opened on the connecting block, the open space is the gap between the first force-bearing block and the second force-bearing block, and the concave surfaces on the first force-bearing block and the second force-bearing block are planes.

[0029] As a preferred technical solution of the present invention: the CT sample block is provided with a first sample fixing hole and a second sample fixing hole, the first sample fixing hole and the second sample fixing hole are fixed in the first connecting hole and the second connecting hole by a sample fixing device and are located in the open space, the plane is used to place the sample, and the length of the plane is determined by the size of the sample.

[0030] In the above structure: the force-bearing rod includes a force block and a connecting block, the force block includes two concave first force blocks and a second force block, the first force block and the second force block are connected by the connecting block, the first sample fixing hole and the second sample fixing hole on the CT sample block are respectively connected to the first connecting hole and the second connecting hole through a gasket, and the main part of the CT sample block is placed in the open space; the detection end of the thermocouple is placed through the detection end fixing hole, and the length of the plane is determined by the size of the sample.

[0031] As a preferred technical solution of the present invention: the pressure sensor placement device also includes a first base column, a first fixing hole, a second fixing hole, a second base column and a chassis, the pressure sensor is placed on the chassis, the first base column and the second base column are used to achieve support, and the signal line of the pressure sensor is respectively led out through the first fixing hole and the second fixing hole.

[0032] In the above structure: the first bottom column and the second bottom column are for support, with a length of 20mm, the first fixing hole and the second fixing hole are for leading out the signal line of the pressure sensor, with a size of M4; the pressure sensor is placed on the chassis, with a diameter of 16mm, which can perfectly place the pressure sensor on the chassis; the first fixing hole has a completely symmetrical structure, with a size of 3.4mm, which can fix the pressure sensor placement structure at the bottom of the entire device to ensure that the pressure sensor is not moved. There are four second fixing holes that are symmetrical on the opposite sides, in order to fix the device left and right.

[0033] As a preferred technical solution of the present invention: it also includes a main control device, which is connected to the host computer through an RS422 module, and the main control device includes a K-type thermocouple detection circuit, a current commutation circuit and a main control chip. The K-type thermocouple detection circuit and the current commutation circuit are driven by the main control chip to achieve thermocouple measurement and elimination of thermoelectric potential. The pressure sensor is connected to the main control chip to achieve the acquisition of pressure data.

[0034] In the above structure: the main control device integrates the measurement of K-type thermocouple, the data acquisition of pressure sensor, the implementation of DCPD algorithm and the implementation of voltage and current excitation signals.

[0035] K-type thermocouple detection circuit: IN0 and IN1 are used as differential inputs, filtered by C204 and C206 respectively, and both ends of the differential input are pulled up to 3.3V by R206 and R212. The resistance of R206 and R212 is 10MΩ. This chip is driven by SPI2.

[0036] The current commutation circuit is composed of four solid-state relays, U601, U602, U603 and U604. The ULN2003 with the number U600 is used as the driver to improve the load capacity. This chip is suitable for driving high-speed and high-power systems. The current commutation module can eliminate the influence of thermal potential on the test parameters. It uses 5V power supply and two IO ports of the main control chip: PB6 and PB7.

[0037] PB6 and PB7 are connected to IN1 and IN2 to control the high and low levels of U600. The No. 1 IO port of the four relays is pulled high by the 5V voltage. One output port of ULN2003 is connected to the No. 2 port of U601 and U603 (1C), and the other output port of ULN2003 is connected to the No. 2 port of U602 and U604 (2C), thus completing the circuit connection of the solid-state relay control end; The No. 4 IO ports of U601 and U602 are connected together to I+, and the No. 4 IO ports of U603 and U604 are connected together to I-; the No. 3 IO ports of U601 and U604 are connected together to I1+, which is the current inflow end of the CT sample; the No. 3 IO ports of U602 and U603 are connected together to I1-, which is the current outflow end of the CT sample; the direction of the current can be controlled by controlling the high and low levels of PB6 and PB7. When PB6 is high and PB7 is low, 1C outputs high and 2C outputs low. U601 and U603 are disconnected because the voltage difference between the two input pins is less than 0.5V. U602 and U604 are closed because the voltage difference between the two input pins is less than 4.5V. When the current I+ flows in, U601 is disconnected and U602 is closed. Therefore, the current flows from U602 into the CT sample and flows back to I- from U604. When PB6 is low and PB7 is high, the opposite is true. The current flows from U601 into the CT sample and flows back to I- from U603.

[0038] The current pressure in the tooling and the temperature in the current device are displayed in the pressure display box; the parameters of the relationship between each voltage and crack value are set in the crack algorithm, and different relationship formulas are divided under different crack lengths; the excitation size is set in the voltage and current excitation signal box, and the voltage, current, overvoltage and overcurrent can be set. You can choose to turn on or off the output in the control box, and click "OK" to take effect. The voltage detected on the CT specimen block can be displayed in the wire box. The crack value can be calculated through the formula in the crack algorithm. The real-time voltage value is displayed in the voltage curve in the form of a curve, and the real-time crack value is displayed in the crack curve in the form of a curve.

[0039] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention integrates mechanical design, hardware circuit design, software drive and host computer development into one detection device. It includes: the design of double-layer bellows, force load transmission mechanism, prefabricated crack CT specimen block, placement and design of pressure sensor, installation of thermocouple, setting of DC power supply parameters, reading of nanovoltmeter data, real-time voltage-crack value conversion, current commutation setting, ADS1220 chip drive, RS485 sensor drive, RS232 instrument communication and RS422 communication realization. A complete system, so it can be used as soon as it is turned on.

[0040] 2. The present invention can fully simulate the high temperature and high pressure environment under the nuclear radiation environment. Through the material tension control unit, the loading mechanism applies a constant tension or pressure to the material to be tested, simulating the load under actual application conditions. The size of the sample crack can be directly detected by the DC potential reduction method with an accuracy of micron level.

[0041] 3. The present invention is provided with a double-layer bellows design, and inflation and deflation are achieved through four electric ball valves. Electric valve No. 1 controls the outer layer inflation, electric valves No. 2 and No. 3 control the inner layer inflation, electric ball valve No. 4 is used for deflation, and the deflation device is used for exhaust gas treatment.

[0042] 4. Sealing design of the device: To ensure the sealing of the electric heating element, thermocouple and signal cable, a sealing head is added. The sealing head structure is mainly composed of a sealing head joint, a sealing head gasket, a sealing head gasket, a sealing head gland and a sealing head nut. Such a design can prevent interference from the external environment, provide stable test conditions, and ensure accurate measurement and data collection.

[0043] 5. The hardware of the present invention has high integration, and all functions are concentrated on a 10cm*10cm circuit board. The CT sample can be directly connected to the circuit board. The circuit can withstand a maximum current of 5A. Within the current-carrying range of the CT sample, the current commutation circuit on the hardware can perfectly meet the commutation requirements.

[0044] 6. The voltage value and crack value are displayed in real time in the form of a line graph, which can intuitively show the growth and change of the crack length. The real-time applied excitation (current, voltage, overcurrent and overvoltage) can be seen on the host computer. The excitation size can be changed during the experiment, and the voltage value will change in real time. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is the overall system diagram of the present invention; Figure 2 It is a schematic diagram of the overall structure of the present invention; Figure 3 It is a schematic diagram of the stress-bearing rod structure; Figure 4 It is a schematic diagram of the external structure of the present invention; Figure 5 Schematic diagram of the outer casing structure; Figure 6 It is a schematic diagram of the AA end surface of the present invention; Figure 7 It is a schematic diagram of the cross-sectional structure of a double-layer bellows; Figure 8 It is a schematic diagram of the gas pipeline structure; Fig. 9 It is a schematic diagram of the structure of a high-pressure gas conditioning system device based on stress corrosion cracking; Fig.10 is a schematic diagram of the structure of a pressure sensor placement device; Fig.11 is a schematic diagram of the support ring structure; Fig.12 It is a schematic diagram of the structure of Teflon sealing ring; Fig.13 is a schematic diagram of the fixed gasket structure; Fig.14 It is a schematic diagram of the structure of the CT specimen block; Fig.15 This is the K-type thermocouple circuit connection diagram; Fig.16 It is the current commutation circuit link diagram; Fig.17 This is the RS232 module circuit connection diagram; Fig.18 This is the upper computer monitoring interface diagram.

[0046] List of reference numerals: 1. Sealing head; 2. Air pipeline; 3. Top cover; 31. Mounting through hole; 32. First concentric tube; 33. Second concentric tube; 34. Stainless steel tube; 35. Sample outlet; 4. Outer sleeve; 41. Opening; 42. Shell wall; 43. Shell cover; 44. Sealing end cover; 45. First end cover; 46. First bellows; 5. Double-layer bellows; 51. Second end cover; 52. Center guide rod; 53. Second bellows; 6. Bottom cover; 7. Sample fixing device; 8. CT sample block; 81. First excitation unit; 82. First voltage detection unit; 83. Second voltage detection unit part; 84, second excitation part; 85, first sample fixing hole; 86, second sample fixing hole; 87, prefabricated crack; 9, pressure sensor placement device; 91, first base column; 92, first fixing hole; 93, second fixing hole; 94, second base column; 95, chassis; 96, lead-out hole; 10, force-bearing rod; 101, first connecting hole; 102, detection end fixing hole; 103, plane; 104, open space; 105, second connecting hole; 106, first force-bearing block; 107, second force-bearing block; 108, connecting block; 11, first connecting seat; 12, second connecting seat. DETAILED DESCRIPTION

[0047] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments: like Figure 1-18As shown, the present invention proposes a micron-level crack detection device for in-pile materials under high temperature and high pressure, comprising a sealing head 1, an air pipeline 2, a top cover 3, a double-layer bellows 5, a bottom cover 6, a CT specimen block 8, a pressure sensor placement device 9 and a stress rod 10, wherein the double-layer bellows 5 comprises a first bellows 46 and a second bellows 53, wherein the first bellows 46 and the second bellows 53 are connected and fixed, one end of the first bellows 46 is connected to the air pipeline 2, the sealing head 1 is installed on the air pipeline 2, the top cover 3 is installed between the first bellows 46 and the air pipeline 2, one end of the second bellows 53 is connected to the stress rod 10, the bottom cover 6 is installed between the second bellows 53 and the stress rod 10, the stress rod 10 is provided with a detection end fixing hole 102 and an open space 104, and the CT specimen block 8 is located at the open space 104 on the stress rod 10. 04, the CT specimen block 8 is a rectangular structure, and a prefabricated crack 87 is arranged from its upper end to the middle part. The CT specimen block 8 is provided with a first excitation part 81 and a second excitation part 84, and a first voltage detection part 82 and a second voltage detection part 83 are arranged in the prefabricated crack 87. The first excitation part 81 and the second excitation part 84 are respectively connected with excitation wires, and the first voltage detection part 82 and the second voltage detection part 83 are connected with detection wires. The excitation wires and the detection wires do not interfere with each other. The excitation wires and the detection wires are led out through the air pipeline 2, and data is obtained and displayed on the upper computer. When inflating or deflation is performed through the air pipeline 2, the first bellows 46 and the second bellows 53 push the CT specimen block 8 to generate pressure, and at this time, a load force can be generated on the specimen. At this time, the specimen can be excited and detected through the excitation line and the detection line.

[0048] The pressure sensor placement device 9 is installed on the CT sample block 8. A pressure sensor is installed on the pressure sensor placement device 9. A fixing hole is also opened on the pressure sensor placement device 9. A thermocouple is installed in the fixing hole. The detection end of the thermocouple is fixed in the detection end fixing hole 102. The thermocouple and the pressure sensor do not interfere with each other. The thermocouple is connected to a thermocouple wire, which is led out through the gas pipeline 2 to obtain data and display it on the host computer.

[0049] It also includes an outer sleeve 4 , which is provided with an opening 41 , and includes a shell wall 42 and a shell cover 43 . The first bellows 46 is installed in the opening 41 , and the shell cover 43 is connected to the top cover 3 .

[0050] It also includes a first end cover 45, a second end cover 51 and a center guide rod 52. The first end cover 45 is installed at one end of the first bellows 46, the end of the center guide rod 52 is fixed on the first end cover 45, the second bellows 53 is sleeved on the center guide rod 52, and the second end cover 51 is installed at the end of the second bellows 53.

[0051] It also includes a sealing end cover 44 , which is installed on the opening 41 of the outer sleeve 4 . A through hole is provided on the sealing end cover 44 , and the central guide rod is provided through the sealing end cover 44 .

[0052] The gas pipeline 2 includes a stainless steel tube 34 and a sample outlet 35, and the top cover 3 includes a first concentric tube 32 and a second concentric tube 33. The first concentric tube 32 and the second concentric tube 33 are respectively provided with mounting holes 31, and the stainless steel tube 34 and the sample outlet 35 are respectively installed in the mounting holes 31, and the excitation line and the detection line are respectively located in the sample outlet 35.

[0053] The force-bearing rod 10 includes a force block and a connecting block 108, the force block includes two concave first force blocks 106 and second force blocks 107, the first force blocks 106 and second force blocks 107 are connected by the connecting block 108, the first force blocks 106 and second force blocks 107 are respectively provided with first connecting holes 101 and second connecting holes 105, the detection end fixing hole 102 is opened on the connecting block 108, the open space 104 is the gap between the first force blocks 106 and the second force blocks 107, and the concave surfaces on the first force blocks 106 and the second force blocks 107 are planes 103.

[0054] The CT sample block 8 is provided with a first sample fixing hole 85 and a second sample fixing hole 86. The first sample fixing hole 85 and the second sample fixing hole 86 are fixed in the first connecting hole 101 and the second connecting hole 105 through the sample fixing device 7 and are located in the open space 104. The plane 103 is used to place the sample, and the length of the plane 103 is determined by the size of the sample.

[0055] The pressure sensor placement device 9 also includes a first base column 91, a first fixing hole 92, a second fixing hole 93, a second base column 94 and a chassis 95. The pressure sensor is placed on the chassis 95. The first base column 91 and the second base column 94 are used to achieve support. The signal lines of the pressure sensor are respectively led out through the first fixing hole 92 and the second fixing hole 93.

[0056] It also includes a main control device, which is connected to the host computer through an RS422 module. The main control device includes a K-type thermocouple detection circuit, a current commutation circuit and a main control chip. The K-type thermocouple detection circuit and the current commutation circuit are driven by the main control chip to achieve thermocouple measurement and elimination of thermoelectric potential. The pressure sensor is connected to the main control chip to achieve the acquisition of pressure data.

[0057] The present invention proposes a micron-level crack detection device for in-pile materials under high temperature and high pressure, comprising a sealing head 1, an air pipeline 2, a top cover 3, a double-layer bellows 5, a bottom cover 6, a CT specimen block 8, a pressure sensor placement device 9 and a stress-bearing rod 10. The sealing head 1 is used to achieve sealing of the air pipeline 2. The air pipeline 2 can not only be used to achieve inflation and deflation, but also can lead out the excitation signal (two excitation wires), voltage signal (two detection wires) and thermocouple (two thermocouple wires) of the CT specimen block 8, thereby acquiring data to be displayed on a host computer.

[0058] The top cover 3 at the front end and the bottom cover 6 at the rear end are used to achieve sealing between the gas pipeline 2 and the first bellows 46, and between the second bellows 53 and the force-bearing rod 10, thereby ensuring the airtightness of the device and providing more comprehensive protection for the entire device. It can protect the internal components from the influence of the external environment, such as dust, moisture, corrosive gases in the air, etc. When welding the top cover 3, full welding at both ends is adopted.

[0059] The double-layer bellows 5 is a metal pipe with a corrugated shape, usually made of materials such as stainless steel or copper. The first bellows 46 and the second bellows 53 serve as a connecting device, which can transmit the external load force to the regulating device. When the external load force acts on the first bellows 46 and the second bellows 53, the medium (nitrogen) in the two bellows will also be subject to corresponding pressure changes and transmitted to other parts of the device, thereby achieving the regulation of the load force. The elastic deformation of the two bellows is very sensitive to pressure changes, and can achieve precise regulation and control of the load force.

[0060] The CT specimen block 8 is a rectangular structure, and a prefabricated crack 87 is provided from its upper end to the middle part. The CT specimen block 8 is provided with a first excitation part 81 and a second excitation part 84, and a first voltage detection part 82 and a second voltage detection part 83 are provided in the prefabricated crack 87. The first excitation part 81 and the second excitation part 84 are respectively connected with excitation wires, and the first voltage detection part 82 and the second voltage detection part 83 are connected with detection wires. The excitation wires and detection wires connected to the CT specimen block 8 need to be bent 90° to the left or right so that the two cannot interfere with each other. The excitation wires and the detection wires are led out through the air pipeline 2, and data is obtained and displayed on the upper computer. When inflating or deflation is performed through the air pipeline 2, the first bellows 46 and the second bellows 53 push the CT specimen block 8 to generate pressure, and a load force can be generated on the specimen at this time. At this time, the excitation wire and the detection wire can be used to excite and detect the specimen.

[0061] CT specimen (Compacted Tension, CT), also known as compact tension specimen, is one of the standard specimen shapes used to study the crack growth behavior and fracture toughness of materials. It is rectangular with a central notch or pre-made crack87.

[0062] In the device of the present invention, a first excitation part 81, a second excitation part 84, a first voltage detection part 82 and a second voltage detection part 83 are respectively provided on the CT specimen block, and an excitation signal is passed into the first excitation part 81 and the second excitation part 84, and a constant current is passed, the voltage is set to 1V, the current is set to 1A, and the DC voltage source is in a constant current mode; the voltage is detected in the first voltage detection part 82 and the second voltage detection part 83. According to the DCPD algorithm, when the current passing through the specimen is constant, the voltage at both ends of the crack on the specimen will increase with the increase of the crack length, and the crack value can be obtained by the voltage.

[0063] The stress rod 10 is used to realize the installation and fixation of the CT sample block 8 and the fixation of the thermocouple detection end. The stress rod 10 can make the CT sample block 8 have better load bearing capacity. By slow wire walking, a crack is preformed at the preformed crack 87, and the minimum crack length is 5um and the maximum crack length is 6mm.

[0064] The pressure sensor placement device 9 is installed on the CT sample block 8. A pressure sensor is installed on the pressure sensor placement device 9. The thermocouple can be placed in the opening 41 of the pressure sensor without interfering with its use. The detection end of the thermocouple is fixed in the detection end fixing hole 102. A thermocouple wire is connected to the thermocouple. The thermocouple wire is led out through the gas pipeline 2 to obtain data for display on the host computer.

[0065] This device is used in conjunction with "A High-Pressure Gas Regulating System Device Based on Stress Corrosion Cracking". The first connecting seat 11 and the second connecting seat 12 on the "A High-Pressure Gas Regulating System Device Based on Stress Corrosion Cracking" correspond to tooling in different environments. Taking the second connecting seat 12 as an example, the four holes are used to inflate and deflate the two interlayers of the two bellows. The two small holes at 0° and 90° in the clockwise direction of the second connecting seat 12 are used to inflate the inner interlayer of the bellows, the 180° small hole in the clockwise direction is used to inflate the outer interlayer, and the other hole is for collecting and discarding the entire device. For detailed contents of the high-pressure gas regulating system device, please refer to the patent "A High-Pressure Gas Regulating System Device Based on Stress Corrosion Cracking". The first connecting seat 11 is used to inflate another set of tooling.

[0066] In order to ensure the sealing of the electric heating element, the thermocouple and the signal cable, the present invention adds a sealing element, which is mainly composed of a sealing head 1 joint, a sealing head 1 gasket, a sealing head 1 sealing pad, a sealing head 1 gland and a sealing head 1 nut.

[0067] The sealing head 1 gasket includes a Teflon sealing ring, which is located between the joint and the sealing head 1 to provide additional sealing and protection. It can fill the gap between the contact surfaces and ensure the tightness of the seal. There are 8 3.5mm through holes on the rings with a radius of 50mm and 57mm.

[0068] A fixed gasket is also included, which is located between the joint and the sealing head 1 to provide additional sealing and protection. It can fill the gap between the contact surfaces to ensure the tightness of the seal.

[0069] Through these sealing heads 1 and their components, the electric heating elements, thermocouples and signal cables inside the device can be effectively protected, and the required sealing in the air environment test device can be ensured. Such a design can prevent interference from the external environment, provide stable test conditions, and ensure accurate measurement and data collection.

[0070] In order to make the device operate normally in an air environment, the entire device is placed in the cage of the extended outer sleeve 4 to protect the first bellows 46 from the influence of the external environment, such as dust, moisture, corrosive gases, etc. in the air.

[0071] The first end cover 45 is used to realize the installation of the central guide rod 52 , and the second bellows 53 is installed and fixed through the central guide rod 52 and the second end cover 51 .

[0072] A sealing end cover 44 is installed on the opening 41 of the outer sleeve 4 to achieve sealing between the outer sleeve 4 and the second bellows 53 to prevent air leakage.

[0073] The stainless steel tube 34 is used to realize the inflation and deflation of the device. The top cover 3 is composed of two concentric first concentric circular tubes 32 and second concentric circular tubes 33. The stainless steel tube 34 and the sample outlet 35 are respectively installed in the installation through hole 31. The sample outlet 35 is used to realize the lead-out of the excitation line and the detection line to facilitate data acquisition.

[0074] The force-bearing rod 10 includes a force block and a connecting block 108. The force block includes two concave first force blocks 106 and second force blocks 107. The first force block 106 and the second force block 107 are connected by the connecting block 108. The first sample fixing hole 85 and the second sample fixing hole 86 on the CT sample block 8 are respectively connected to the first connecting hole 101 and the second connecting hole 105 through gaskets. The main part of the CT sample block 8 is placed in the open space 104; the detection end of the thermocouple is placed through the detection end fixing hole 102, and the length of the plane 103 is determined by the size of the sample.

[0075] The first bottom column 91 and the second bottom column 94 are for supporting purposes, and the length is 20mm. The first fixing hole 92 and the second fixing hole 93 are for leading out the signal line of the pressure sensor, and the size is M4. The pressure sensor is placed on the chassis 95, and the diameter is 16mm, which can perfectly place the pressure sensor on the chassis 95. The first fixing hole 92 has a completely symmetrical structure, and the size is 3.4mm, which can fix the pressure sensor placement structure at the bottom of the entire device to ensure that the pressure sensor is not moved. There are four second fixing holes 93 that are symmetrical on the opposite sides, so as to be able to fix the device left and right.

[0076] The main control device integrates the measurement of K-type thermocouples, data acquisition of pressure sensors, implementation of DCPD algorithms, and implementation of voltage and current excitation signals.

[0077] K-type thermocouple detection circuit: IN0 and IN1 are used as differential inputs, filtered by C204 and C206 respectively, and both ends of the differential input are pulled up to 3.3V by R206 and R212. The resistance of R206 and R212 is 10MΩ. This chip is driven by SPI2.

[0078] The current commutation circuit is composed of four solid-state relays, U601, U602, U603 and U604. The ULN2003 with the number U600 is used as the driver to improve the load capacity. This chip is suitable for driving high-speed and high-power systems. The current commutation module can eliminate the influence of thermal potential on the test parameters. It uses 5V power supply and two IO ports of the main control chip: PB6 and PB7.

[0079] PB6 and PB7 are connected to IN1 and IN2 to control the high and low levels of U600. The No. 1 IO port of the four relays is pulled high by the 5V voltage. One output port of ULN2003 is connected to the No. 2 port of U601 and U603 (1C), and the other output port of ULN2003 is connected to the No. 2 port of U602 and U604 (2C), thus completing the circuit connection of the solid-state relay control end.

[0080] The No. 4 IO ports of U601 and U602 are connected together to I+, and the No. 4 IO ports of U603 and U604 are connected together to I-; the No. 3 IO ports of U601 and U604 are connected together to I1+, which is the current inflow end of the CT sample; the No. 3 IO ports of U602 and U603 are connected together to I1-, which is the current outflow end of the CT sample; the direction of the current can be controlled by controlling the high and low levels of PB6 and PB7. When PB6 is high and PB7 is low, 1C outputs high and 2C outputs low. U601 and U603 are disconnected because the voltage difference between the two input pins is less than 0.5V. U602 and U604 are closed because the voltage difference between the two input pins is less than 4.5V. When the current I+ flows in, U601 is disconnected and U602 is closed. Therefore, the current flows from U602 into the CT sample and flows back to I- from U604. When PB6 is low and PB7 is high, the opposite is true. The current flows from U601 into the CT sample and flows back to I- from U603.

[0081] The current pressure in the tooling and the temperature in the current device are displayed in the pressure display box; the parameters of the relationship between each voltage and crack value are set in the crack algorithm, and different relationship formulas are corresponding to different crack lengths; the excitation size is set in the voltage and current excitation signal box, and the voltage, current, overvoltage and overcurrent can be set. You can choose to turn on or off the output in the control box, and click "OK" to take effect. The voltage detected on the CT specimen block 8 can be displayed in the wire box. The crack value can be calculated through the formula in the crack algorithm. The real-time voltage value is displayed in the voltage curve in the form of a curve, and the real-time crack value is displayed in the crack curve in the form of a curve.

[0082] The comparison between the present invention and the prior art is as follows: 1. Most of the existing crack detection systems are designed for non-destructive or destructive testing under normal conditions. However, the device of the present invention can perform micron-level crack detection under high temperature and high pressure in a nuclear radiation environment. The detection accuracy is high, the maximum working pressure is 10MPa, the maximum temperature is 400 degrees, and the results are stable and reliable.

[0083] 2. The existing crack detection system can only measure prefabricated cracks 87 when the experimental test equipment is stable and reliable. However, the device of the present invention can simulate and observe the crack evolution process in the irradiation environment in the pile through the cooperation of "A high-pressure gas conditioning system device based on stress corrosion cracking", carry out research on the online measurement technology of SCC crack extension during irradiation test, and develop the standardized device and system of SCC crack extension online measurement instrument.

[0084] 3. The CT samples of the existing crack detection devices are generally placed in an exposed position. The device of the present invention is provided with a tooling that is resistant to high temperature and high pressure. The samples are detected in a closed space, which can shield the interference of many clutters.

[0085] 4. Existing crack detection devices perform detection in a non-destructive or destructive manner. The device of the present invention uses a DC potential drop method and adds a current conversion module to eliminate the influence of thermoelectric potential, thereby effectively improving the accuracy.

[0086] 5. Existing crack detection systems generally do not have overly complex circuit designs and will not reflect the temperature and pressure conditions of the device. The device of the present invention collects the data of the thermocouple and pressure sensor through the main control circuit and packages them for display on the host computer.

[0087] 6. Existing crack detection systems rarely have a host computer display interface. All parameter signals are transmitted to the host computer through serial communication for display, which monitors the changes in crack size, device temperature, device pressure, and the size of the excitation signal in real time. The host computer operation interface is simple and the human-computer interaction is friendly.

[0088] 7. The prefabricated crack 87 of the existing crack detection system is generally achieved through a fatigue stretching machine, while the prefabricated crack 87 of the device of the present invention is achieved through a slow wire-feeding device, the crack length can be controlled at 1um, the crack accuracy is high, and the achievement effect is good.

[0089] The above description is only a preferred embodiment of the present invention and does not constitute any other form of limitation to the present invention. Any modification or equivalent change made based on the technical essence of the present invention still falls within the scope of protection required by the present invention.

Claims

1. A device for detecting micron-level cracks in pile materials under high temperature and high pressure, characterized in that: The invention comprises a sealing head (1), an air pipeline (2), a top cover (3), a double-layer bellows (5), a bottom cover (6), a CT sample block (8), a pressure sensor placement device (9) and a force-bearing rod (10), wherein the double-layer bellows (5) comprises a first bellows (46) and a second bellows (53), wherein the first bellows (46) and the second bellows (53) are connected and fixed, one end of the first bellows (46) is connected to the air pipeline (2), and the air pipeline (2) is provided with a sealing head (1), a top cover (3) is provided between the first bellows (46) and the gas pipeline (2), one end of the second bellows (53) is connected to a force-bearing rod (10), a bottom cover (6) is provided between the second bellows (53) and the force-bearing rod (10), a detection end fixing hole (102) and a space (104) are provided on the force-bearing rod (10), and the CT specimen block (8) is located in the space (104) on the force-bearing rod (10) In the embodiment, the CT sample block (8) is a rectangular structure, and a prefabricated crack (87) is provided from the upper end to the middle of the CT sample block (8). A first excitation part (81) and a second excitation part (84) are provided on the CT sample block (8), and a first voltage detection part (82) and a second voltage detection part (83) are provided in the prefabricated crack (87). The first excitation part (81) and the second excitation part (84) are respectively connected with excitation wires, and the first voltage detection part (82) and the second voltage detection part (83) are connected with detection wires. The excitation wires and the detection wires do not interfere with each other. The excitation wires and the detection wires are led out through the gas pipeline (2) to obtain data to the upper computer for display. When the gas pipeline (2) is inflated or deflated, the first bellows (46) and the second bellows (53) push the CT sample block (8) to generate pressure, and at this time, a load force can be generated on the sample. At this time, the sample can be excited and detected through the excitation wire and the detection wire. The pressure sensor placement device (9) is installed on the CT sample block (8), a pressure sensor is installed on the pressure sensor placement device (9), a fixing hole is also opened on the pressure sensor placement device (9), a thermocouple is installed in the fixing hole, the detection end of the thermocouple is fixed in the detection end fixing hole (102), the thermocouple and the pressure sensor do not interfere with each other, the thermocouple is connected to the thermocouple, the thermocouple wire is led out through the gas pipeline (2), and the acquired data is displayed on the upper computer.

2. The device for detecting micron-level cracks in pile materials under high temperature and high pressure according to claim 1, characterized in that: It also includes an outer sleeve (4), which is provided with an opening (41), and includes a shell wall (42) and a shell cover (43), the first bellows (46) is installed in the opening (41), and the shell cover (43) is connected to the top cover (3).

3. The device for detecting micron-level cracks in pile materials under high temperature and high pressure according to claim 1, characterized in that: It also includes a first end cover (45), a second end cover (51) and a center guide rod (52), wherein the first end cover (45) is installed on one end of a first bellows (46), the end of the center guide rod (52) is fixed on the first end cover (45), the second bellows (53) is sleeved on the center guide rod (52), and the second end cover (51) is installed on the end of the second bellows (53).

4. The device for detecting micron-level cracks in pile materials under high temperature and high pressure according to claim 1 or 2, characterized in that: It also comprises a sealing end cover (44), wherein the sealing end cover (44) is mounted on the opening (41) of the outer sleeve (4), a through hole is arranged on the sealing end cover (44), and the central guide rod is arranged through the sealing end cover (44).

5. The device for detecting micron-level cracks in pile materials under high temperature and high pressure according to claim 1, characterized in that: The gas pipeline (2) comprises a stainless steel pipe (34) and a sample outlet (35); the top cover (3) comprises a first concentric circular pipe (32) and a second concentric circular pipe (33); the first concentric circular pipe (32) and the second concentric circular pipe (33) are respectively provided with mounting through holes (31); the stainless steel pipe (34) and the sample outlet (35) are respectively mounted in the mounting through holes (31); and the excitation line and the detection line are respectively located in the sample outlet (35).

6. The device for detecting micron-level cracks in pile materials under high temperature and high pressure according to claim 1, characterized in that: The force-bearing rod (10) comprises a force-bearing block and a connecting block (108), wherein the force-bearing block comprises two concave first force-bearing blocks (106) and second force-bearing blocks (107), wherein the first force-bearing block (106) and the second force-bearing block (107) are connected via the connecting block (108), wherein the first force-bearing block (106) and the second force-bearing block (107) are respectively provided with a first connecting hole (101) and a second connecting hole (105), wherein the detection end fixing hole (102) is provided on the connecting block (108), wherein the open space (104) is a gap between the first force-bearing block (106) and the second force-bearing block (107), and wherein the concave surfaces on the first force-bearing block (106) and the second force-bearing block (107) are plane surfaces (103).

7. The device for detecting micron-level cracks in pile materials under high temperature and high pressure according to claim 1 or 6, characterized in that: The CT sample block (8) is provided with a first sample fixing hole (85) and a second sample fixing hole (86). The first sample fixing hole (85) and the second sample fixing hole (86) are fixed in a first connection hole (101) and a second connection hole (105) through a sample fixing device (7) and are located in an open space (104). The plane (103) is used to place the sample, and the length of the plane (103) is determined by the size of the sample.

8. The device for detecting micron-level cracks in pile materials under high temperature and high pressure according to claim 1, characterized in that: The pressure sensor placement device (9) further comprises a first base column (91), a first fixing hole (92), a second fixing hole (93), a second base column (94) and a chassis (95); the pressure sensor is placed on the chassis (95); the first base column (91) and the second base column (94) are used to achieve support; and the signal line of the pressure sensor is led out through the first fixing hole (92) and the second fixing hole (93), respectively.

9. The device for detecting micron-level cracks in pile materials under high temperature and high pressure according to claim 1, characterized in that: It also includes a main control device, which is connected to the host computer through an RS422 module. The main control device includes a K-type thermocouple detection circuit, a current commutation circuit and a main control chip. The K-type thermocouple detection circuit and the current commutation circuit are driven by the main control chip to achieve thermocouple measurement and elimination of thermoelectric potential. The pressure sensor is connected to the main control chip to achieve the acquisition of pressure data.

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