Axial compression creep test device and test method

Abstract

An axial compression creep test device and test method belong to the field of nuclear engineering materials. The axial compression creep test device comprises a base, a guide rod, a pressing plate, a pressing device and a deflection rod. The base is connected to one end of the guide rod, the pressing plate is provided through the other end of the guide rod and is subjected to pressure towards the base by the pressing device, the pipe to be tested is abutted between the base and the pressing plate, a plurality of deflection rods are arranged on the outer circumferential side of the pipe to be tested, and the two ends of the deflection rod are abutted to the base and the pressing plate and are subjected to bending deformation. The device converts the axial compression creep deformation of the pipe to be tested into the bending deformation of the deflection rod, realizes the amplification of the deformation amount, so that the deformation amount can be measured outside the irradiation capsule by a non-destructive testing method, thereby realizing the continuous measurement of the same sample, improving the measurement accuracy and reducing the test cost.

Description

Technical Field

[0001] This invention belongs to the field of nuclear engineering materials, specifically relating to an axial compression creep testing device and testing method. Background Technology

[0002] Components within a reactor, such as fuel rod cladding tubes and control rod guide tubes, are susceptible to axial pressure loads during service. Long-term exposure to high-temperature irradiation can lead to axial compressive creep deformation in tubular components. To improve the safety and reliability of long-term reactor operation, it is necessary to systematically investigate the compressive creep behavior of these components. Existing creep testing methods require loading the sample into an irradiation capsule, sending the capsule entirely into the research reactor for irradiation, and then removing and disassembling it after reaching a certain irradiation dose to measure the sample's dimensional changes in a hot chamber. Because the sample generates induced radioactivity after irradiation, it is difficult to re-encapsulate it for further testing. This prevents existing methods from continuously tracking the creep behavior of the same sample; each measurement requires destructive disassembly of the irradiation capsule, generating significant amounts of radioactive waste; and the limited measurement accuracy in the hot chamber, typically only on the order of ±10 μm, makes it difficult to accurately track early, minute deformations. Therefore, providing an axial compression testing device capable of continuously tracking the same sample is of high practical value. Summary of the Invention

[0003] The purpose of this invention is to provide an axial compression creep testing device that enables continuous tracking of creep deformation of the same sample. This invention also provides an axial compression creep testing method.

[0004] According to one embodiment of the present invention, an axial compression creep testing device is provided. The device includes a base, a guide rod, a pressure plate, a pressurizing device, and flexural rods. The base is fixedly connected to one end of the guide rod. The pressure plate passes through the guide rod from the other end and is movable axially along the guide rod. A pipe to be tested is placed between the pressure plate and the base, such that the pipe passes through the guide rod and abuts against the base and the pressure plate respectively. The pressurizing device is connected to the pressure plate and applies a pressure load towards the base to the pressure plate. A plurality of flexural rods are uniformly arranged circumferentially around the guide rod, with both ends of each flexural rod abutting against the base and the pressure plate respectively. When the pipe to be tested is installed between the base and the pressure plate, the flexural rods are distributed on the outer periphery of the pipe to be tested and undergo bending deformation.

[0005] This device can convert axial compressive creep deformation into bending deformation of a flexure rod, thus amplifying the deformation amount. This allows for the measurement of the bending deformation of the flexure rod using non-destructive testing techniques without damaging the irradiated capsule, thereby calculating the axial compressive creep deformation amount. This enables non-destructive testing and allows for continuous testing of the same sample, improving testing efficiency and reducing the generation of radioactive waste.

[0006] Furthermore, in some embodiments, the pressurizing device includes an upper pressure plate and a spring. The upper pressure plate is fixedly connected to the guide rod, the spring is in a compressed state and passes through the guide rod, and the two ends of the spring abut against the upper pressure plate and the pressurizing plate, respectively.

[0007] Furthermore, in some embodiments, the spring is made of a nickel-based 718 alloy.

[0008] Furthermore, in some embodiments, the other end of the guide rod is provided with a threaded section, and the upper pressure plate is provided with a threaded hole at its center, and the upper pressure plate is connected to the threaded section through the threaded hole.

[0009] Furthermore, in some embodiments, the flexural bar is made of zirconium alloy, stainless steel, or aluminum alloy.

[0010] Furthermore, in some embodiments, the flexural bar is configured as a sheet-like structure with a length of 10mm-60mm, a width of 5mm-10mm, and a thickness of 0.3mm-2mm.

[0011] Furthermore, in some embodiments, the flexural bar is configured as a rod-shaped structure with a length of 10mm-60mm and a diameter of 0.3mm-2mm.

[0012] Furthermore, in some embodiments, the base and / or the pressure plate further include an adjusting bolt, the flexural rod abutting against the adjusting bolt, and rotating the adjusting bolt can change the axial distance between the adjusting bolt and the pressure plate and / or the base to achieve active adjustment of the deflection of the flexural rod.

[0013] According to another aspect of the present invention, an axial compression creep test method is provided, the method comprising the following steps: Step a): Provide the pipe fitting to be tested, install the pipe fitting to be tested on the axial compression creep test device, the axial compression creep test device is the axial compression creep test device provided in any of the foregoing embodiments, and measure the bending deformation of the flexural rod to obtain the first deflection; Step b): The pipe fitting to be tested and the axial compression creep test device are loaded into an irradiation capsule and sent into the research reactor for a certain dose of irradiation test; Step c): Remove the irradiated capsule and measure the bending deformation of the flexural bar using neutron phase-contrast imaging or high-energy X-ray CT to obtain the second deflection; calculate the axial compression deformation of the pipe to be tested based on the second deflection.

[0014] Furthermore, in some embodiments, the method further includes step d): after the measurement is completed, the irradiation capsule is sent into the research reactor to continue the irradiation experiment. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of the pipe fitting to be tested and the axial compression creep test device in one embodiment; Figure 2 This is a schematic cross-sectional view of the pipe fitting to be tested and the axial compression creep test device in one embodiment. Figure 3 This is a schematic cross-sectional view of the irradiated pipe fitting and the axial compression creep test device in one embodiment. Figure 4 for Figure 1 A magnified structural diagram of region A in the middle.

[0016] Meaning of the reference numerals in the attached figures: 1-Base; 2-Guide rod; 3-Pressure plate; 4-Flexing rod; 5-Spring; 6-Upper pressure plate; 7-Threaded section; 8-Adjusting bolt; 9-Pipe to be tested.

[0017] The purpose of the above-described drawings is to provide a detailed description of the present invention so that those skilled in the art can understand the technical concept of the invention, and is not intended to limit the invention. For the sake of brevity, the above-described drawings only schematically depict the structures related to the technical features of the present invention, and do not depict the complete structure and all details strictly according to actual scale. Detailed Implementation

[0018] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings.

[0019] The term "embodiment" as used herein means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment herein. The phrase appearing in various places in the specification does not necessarily refer to the same embodiment, nor is it limited to mutually exclusive, independent, or alternative embodiments. Those skilled in the art will understand that the embodiments herein can be combined with other embodiments without causing structural conflicts.

[0020] In this description, unless otherwise explicitly specified and limited, the technical terms "installation," "connection," "joining," etc., should be interpreted broadly, for example, referring to movable connections, fixed connections, or integration. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application based on the specific circumstances.

[0021] In this description, terms such as "upper," "lower," "left," "right," "lateral," "longitudinal," "height," "length," and "width," which indicate orientation or positional relationships, are intended to accurately describe the embodiments and simplify the description, rather than limiting the parts or structures involved to have a specific orientation, or to be installed or operated in a specific orientation, and should not be construed as limiting the embodiments in this document.

[0022] In this description, terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating relative importance or limiting the number, specific order, or primary / secondary relationship of the described technical features. In this description, "multiple" means at least two.

[0023] Currently, axial compression tests on critical reactor structural components such as fuel rod cladding tubes and control rod guide tubes require pressure testing at both ends of the component sample, followed by encapsulation in an irradiation capsule. The capsule is then inserted into a dedicated channel in the research reactor for irradiation with a specific dose. After removal and disassembly, the deformation of the component sample is measured in a hot chamber. However, because the irradiated sample generates induced radioactivity, it cannot be resealed for further testing, making continuous tracking of the irradiation creep behavior of the same sample difficult. Using a method of deploying multiple samples at once and removing them in stages is costly and consumes significant resources. Furthermore, the data lacks consistency due to the varying irradiation doses received. Moreover, the disassembly and disposal of the irradiation capsule after each test generates substantial radioactive waste, increasing the difficulty of radioactive contamination management.

[0024] To overcome the aforementioned problems of the prior art, one embodiment of the present invention provides an axial compression creep testing device. When using this device to conduct axial compression creep tests on pipe fittings, multiple accurate measurements can be performed on the same sample subjected to different irradiation doses using non-destructive testing methods, ensuring the consistency of the test samples and effectively reducing the generation of radioactive waste. Figure 1 and Figure 2As shown, the testing apparatus includes a base 1, a guide rod 2, a pressure plate 3, and a flexure rod 4. The base 1 is fixedly connected to the lower end of the guide rod 2. The pressure plate 3 passes through the upper end of the guide rod 2 and is axially movable along the guide rod 2. A pipe fitting 9 to be tested is placed between the pressure plate 3 and the base 1. In its installed state, the pipe fitting 9 passes through the guide rod 2, with its lower end abutting against the base 1 and its upper end abutting against the pressure plate 3. A pressurizing device is also provided above the pressure plate 3, applying pressure to the pressure plate 3 towards the base 1 to provide an axial compressive load to the pipe fitting 9 to be tested. The guide rod 2 and the base 1 can be connected by welding, mechanical connection such as bolts or pins, or integral molding.

[0025] In a preferred embodiment, the pressurizing device includes a spring 5 and an upper pressure plate 6. The spring 5 passes through the guide rod 2, and the upper pressure plate 6 is fixedly connected to the guide rod 2 to keep the spring 5 in a compressed state. In a further preferred embodiment, the upper end of the guide rod 2 is provided with a threaded section 7, and the center of the upper pressure plate 6 is provided with a threaded hole that matches the threaded section 7, so that the upper pressure plate 6 can be fixedly connected to the threaded section 7 through the threaded hole. The spring 5 is made of a metal material with good neutron permeability and strong resistance to radiation swelling, such as zirconium alloy, nuclear-grade stainless steel, or aluminum alloy.

[0026] Multiple flexural rods 4 are evenly arranged axially around the guide rod 2, with their two ends abutting against the base 1 and the pressure plate 3, respectively. When the pipe fitting 9 to be tested is installed between the base 1 and the pressure plate 3, the flexural rods 4 are located on the outer periphery of the pipe fitting 9 to be tested, and the flexural rods 4 are subjected to axial compression and undergo a certain amount of bending deformation. The flexural rods 4 are also made of zirconium alloy, nuclear-grade stainless steel, or aluminum alloy with good neutron permeability and strong resistance to radiation swelling. In different embodiments, depending on the test requirements, the flexural rods 4 can take different forms: in some embodiments, the flexural rods 4 are configured as a sheet-like structure with a length of 10mm-60mm, a width of 5mm-10mm, and a thickness of 0.3mm-2mm; in other embodiments, the flexural rods 4 are configured as a rod-like structure with a length of 10mm-60mm and a diameter of 0.3mm-2mm. As the experiment progresses, when the tested pipe fitting 9 undergoes axial compressive creep, the flexural bar 4 can convert its axial deformation into its own bending deformation, thereby amplifying the deformation from the μm level to the mm level, which can be identified by non-destructive testing technology outside the irradiated capsule. Based on geometric derivation, the relationship between the deflection δ of the flexural bar 4 and the axial deformation ΔL of the tested pipe fitting 9 satisfies: ΔL = δ 2 π 2 / 4L, where L is the length of the flexural bar 4.

[0027] In a further preferred embodiment, in order to better adjust the initial bending degree of the flexural bar 4, such as... Figure 4As shown, the flexural rod 4 is adjusted using an adjusting bolt 8. Specifically, a through hole is provided on the pressure plate 3 at the position for mounting the flexural rod 4. One end of the adjusting bolt 8 passes through the through hole and abuts against the flexural rod 4 inserted into the through hole. When the adjusting bolt 8 is rotated, it moves axially, thereby changing the distance between the two ends of the flexural rod 4 and realizing the adjustment of the bending degree of the flexural rod 4. In different embodiments, the adjusting bolt 8 can be set in different positions: in some embodiments, the adjusting bolt 8 is only set on the pressure plate 3; in some embodiments, the adjusting bolt 8 is only set on the base 1; and in other embodiments, the adjusting bolt 8 can be set on both the pressure plate 3 and the base 1, thereby allowing the bending degree of the flexural rod 4 to be adjusted from both the upper and lower ends.

[0028] In a preferred embodiment, combined with Figure 1 , Figure 2 and Figure 4 The process of conducting an axial compression creep test using the axial compression creep testing apparatus provided in the above embodiments is as follows: Step a): Provide the pipe fitting 9 to be tested. The pipe fitting 9 is a Zr-4 alloy pipe with an outer diameter of 9.5 mm, a wall thickness of 0.5 mm, and a length of 60 mm. Fit the pipe fitting 9 onto the guide rod 2, ensuring the lower end of the pipe fitting 9 abuts against the base 1. Then, sequentially fit the pressure plate 3, spring 5, and upper pressure plate 6 onto the guide rod 2, and tighten the upper pressure plate onto the threaded section 7. The spring 5 is made of zirconium alloy and is machined to have a preset elastic force according to the test requirements. The spring 5 compresses and provides a pressure load to the upper pressure plate 6, subjecting the pipe fitting 9 to a continuous axial compressive load. Grind the ends of four flexible rods 4 flat and evenly spaced them between the base 1 and the pressure plate 3, ensuring the ends of the flexible rods 4 abut against the base 1 and the adjusting bolts 8 mounted on the pressure plate 3, respectively. The flexible rods 4 are 60 mm long, 5 mm wide, and 0.8 mm thick. Rotate the adjusting bolt 8 to make the flexural rod 4 bend slightly, and then spot weld the adjusting bolt 8 to the pressure plate 3 to lock it. The initial deflection of the flexural rod 4 in its initial state is measured to be 0.25 mm.

[0029] Step b): The tube to be tested, 9, is encapsulated together with the test kit into an irradiation capsule. The irradiation capsule is made of 6061 aluminum alloy, with an inner diameter of 12 mm and a wall thickness of 1 mm. The irradiation capsule is filled with 0.3 MPa helium gas and sealed using electron beam welding. The irradiation capsule is then placed into a dedicated channel in the research reactor for irradiation treatment.

[0030] Step c): After irradiation with the specified dose, the reactor is shut down, the irradiated capsule is removed, and within 8 hours, the irradiated capsule is placed in a neutron imaging station for 60 seconds of exposure to obtain a neutron phase-contrast imaging image. After irradiation, the tested pipe 9 undergoes axial compressive creep deformation, such as... Figure 3As shown, due to the reduction in the axial length of the pipe fitting 9 under test, the bending degree of the flexural bar 4 intensifies, deviating from the initial position B. The deformation of the pipe fitting 9 under test is calculated by measuring the second deflection of the flexural bar 4 after irradiation. In other embodiments, high-energy X-ray CT can also be used for imaging.

[0031] Step d): After the measurement is completed, the irradiation capsule is sent back into the research reactor to continue the irradiation experiment until the preset maximum irradiation dose is reached.

[0032] The results of the measured deflection changes of the flexural bar 4 and the calculated deformation of the tested pipe fitting 9 under irradiation doses of 1.5 dpa, 3 dpa and 5 dpa are shown in Table 1.

[0033] Table 1. Test Measurement and Calculation Results of Zr-4 Tube Samples

[0034] Using the axial compression creep test method provided in the above embodiments, the axial compression creep deformation accuracy of the tested pipe fitting 9 can reach ±0.15μm, demonstrating good precision. The test process consistently measures the same sample, ensuring sample consistency. Furthermore, the measurement process does not require disassembling or destroying the irradiation capsule, significantly reducing radioactive waste, improving test efficiency, and lowering test costs.

[0035] The purpose of the above embodiments is to provide a further detailed description of the present invention in conjunction with the accompanying drawings, so that those skilled in the art can understand the technical concept of the present invention. Within the scope of the present invention, optimization or equivalent substitution of the involved part structures and method steps, as well as combination of implementation methods in different embodiments without causing structural and principle conflicts, all fall within the protection scope of the present invention.

Claims

1. An axial compression creep testing device, characterized in that, Includes a base, guide rod, pressure plate, pressure device, and flexural rod, among which, The base is fixedly connected to one end of the guide rod, and the pressure plate passes through the other end of the guide rod and can move along the axial direction of the guide rod; the pipe to be tested is placed between the pressure plate and the base, so that the pipe to be tested passes through the guide rod and abuts against the base and the pressure plate respectively; The pressurizing device is connected to the pressurizing plate and applies a pressure load toward the base to the pressurizing plate; Multiple flexural bars are evenly arranged around the guide bar, with the two ends of each flexural bar abutting against the base and the pressure plate, respectively. When the pipe to be tested is installed between the base and the pressure plate, the flexural bars are distributed on the outer periphery of the pipe to be tested and undergo bending deformation.

2. The axial compression creep testing device according to claim 1, characterized in that, The pressurizing device includes an upper pressure plate and a spring. The upper pressure plate is fixedly connected to the guide rod. The spring is in a compressed state and passes through the guide rod. The two ends of the spring abut against the upper pressure plate and the pressurizing plate, respectively.

3. The axial compression creep testing apparatus according to claim 2, characterized in that, The spring is made of nickel-based 718 alloy.

4. The axial compression creep testing apparatus according to claim 2 or 3, characterized in that, The other end of the guide rod is provided with a threaded section, and the upper pressure plate is provided with a threaded hole at its center. The upper pressure plate is connected to the threaded section through the threaded hole.

5. The axial compression creep testing apparatus according to any one of claims 1 to 3, characterized in that, The flexural bar is made of zirconium alloy, stainless steel or aluminum alloy.

6. The axial compression creep testing apparatus according to claim 5, characterized in that, The flexural bar is configured as a thin sheet structure with a length of 10mm-60mm, a width of 5mm-10mm, and a thickness of 0.3mm-2mm.

7. The axial compression creep testing apparatus according to claim 5, characterized in that, The flexural bar is configured as a rod-shaped structure with a length of 10mm-60mm and a diameter of 0.3mm-2mm.

8. The axial compression creep testing apparatus according to any one of claims 1 to 3, characterized in that, The base and / or the pressure plate further include an adjusting bolt, and the flexural rod abuts against the adjusting bolt. Rotating the adjusting bolt can change the axial distance between the adjusting bolt and the pressure plate and / or the base to achieve active adjustment of the deflection of the flexural rod.

9. A method for axial compression creep testing, characterized in that, Includes the following steps: Step a): Provide the pipe fitting to be tested, install the pipe fitting to be tested on the axial compression creep test device, the axial compression creep test device is the axial compression creep test device as described in any one of claims 1 to 8, and measure the bending deformation of the flexural rod to obtain the first deflection; Step b): The pipe fitting to be tested and the axial compression creep test device are loaded into an irradiation capsule and sent into the research reactor for a certain dose of irradiation test; Step c): Remove the irradiated capsule and measure the bending deformation of the flexural bar using neutron phase-contrast imaging or high-energy X-ray CT to obtain the second deflection; calculate the axial compression deformation of the pipe to be tested based on the second deflection.

10. The axial compression creep test method according to claim 9, characterized in that, It also includes step d): After the measurement is completed, the irradiation capsule is sent into the research reactor to continue the irradiation test.

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