Biaxial fatigue test mold

Abstract

The utility model discloses a biaxial fatigue test mold which comprises two clamping and loading assemblies, each clamping and loading assembly comprises a threaded sleeve, a sleeve, a deformation block and a clamping sleeve, and the deformation block is placed between the threaded sleeve and the sleeve; a clamping hole channel is formed in the deformation block; the threaded sleeve moves relative to the sleeve by rotating and screwing, and the generated displacement acts on the deformation block, so that the clamping hole channel of the deformation block annularly holds the pipe. One end of the clamping sleeve is connected with the sleeve, the other end of the clamping sleeve is connected with the fatigue machine, an oil injection pipe is arranged on the side face of the clamping sleeve, one end of the oil injection pipe is communicated with a cavity channel of the clamping sleeve, and the other end of the oil injection pipe is connected with an external oil source. And the external and internal parts of the pipe are simultaneously clamped and loaded, so that local high stress concentration generated on the surface of the pipe by a traditional mechanical clamp is reduced, and the accuracy of an experimental result is improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to nuclear material testing technical field, concretely is a kind of double-shaft fatigue test mould. BACKGROUND

[0002] Fatigue failure of material refers to the phenomenon that material is destroyed or fails after a certain cycle period under alternating stress. Fatigue failure is a delayed failure caused by cyclic stress, and the stress level at the time of failure is often lower than the tensile strength of the material, or even lower than the yield strength of the material. The fatigue life of the material is related to the cyclic stress it suffers, and the higher the stress level, the shorter the life, and the lower the stress level, the longer the life.

[0003] Double-shaft fatigue is a fatigue failure phenomenon that occurs when a material or structure simultaneously bears cyclic stress or strain in two different directions, which is a typical form of multi-axial fatigue. Compared with uniaxial fatigue (only one direction is stressed), double-shaft fatigue requires higher requirements for material life prediction and engineering design due to the complexity of stress state. The material simultaneously bears cyclic loads in two orthogonal directions (axial and circumferential directions).

[0004] In nuclear reactors, fuel cladding often bears multi-axial stress state caused by factors such as in-pipe fission gas expansion, temperature fluctuation, radiation, mechanical load, etc. Double-shaft fatigue simulates a load state closer to actual working conditions, which is crucial for accurately predicting the mechanical properties and durability of nuclear materials. The high temperature and radiation environment in nuclear reactors can cause radiation damage and microstructure changes in materials, such as lattice defects and precipitates, which can significantly change the fatigue properties of the materials. Research on double-shaft fatigue helps to reveal the fatigue behavior of fuel cladding under complex axial and circumferential stress states, providing guidance for improving the reliability and life of materials. Unlike uniaxial fatigue, double-shaft fatigue can more comprehensively describe the damage accumulation process of materials under complex stress states. Some components in nuclear reactors, such as fuel cladding, pressure vessels, pipes, control rods, etc., often bear multi-axial alternating stress. Understanding the double-shaft fatigue behavior can help predict the fatigue life of these components and ensure their safe operation.

[0005] Existing pipe fatigue molds mostly only consider uniaxial fatigue, ignoring the complex stress conditions of pipe fatigue in the nuclear field. Double-shaft fatigue testing equipment is usually more complex than uniaxial fatigue testing equipment. It is necessary to design and manufacture equipment that can simultaneously apply two independent loads, which not only increases the complexity and manufacturing cost of the equipment. And, during the double-shaft fatigue test process, it is difficult to control the loading accuracy of the two independent load axes. It is easy to cause uneven or low accuracy of the two independent load axes, resulting in deviation of the test results. SUMMARY

[0006] The purpose of this invention is to provide a biaxial fatigue test mold that eliminates the need for complex biaxial mechanical equipment to simultaneously clamp and apply loads to the outside and inside of the pipe, thus avoiding the test structure deviation problems caused by uneven or inaccurate application of two independent loads that are prone to occur with complex biaxial mechanical equipment.

[0007] The technical solution of this utility model is:

[0008] A biaxial fatigue testing mold includes two symmetrically arranged clamping and loading components. Each clamping and loading component includes: a threaded sleeve, which is a tubular structure with its internal space serving as a first mating channel; a sleeve, one end of which is threadedly connected to the threaded sleeve, the internal space of which serves as a second mating channel; and a deformation block, which has a clamping channel along its central axis for inserting a tube. One end of the deformation block is fitted into the first mating channel, and the other end is fitted into the second mating channel. The first mating channel and the second mating channel are... The structure of the channel matches the structure of the deformable block; a clamping sleeve, the internal space of which serves as the clamping sleeve cavity, one end of the clamping sleeve is connected to the other end of the sleeve by a fixing member, the clamping sleeve cavity and the clamping channel are coaxially connected, the other end of the clamping sleeve is the clamping end, an oil injection pipe is provided on the side of the clamping sleeve, one end of the oil injection pipe is connected to the clamping sleeve cavity, the other end of the oil injection pipe is connected to an external oil source, a sealing ring is provided at the end of the clamping sleeve cavity near the sleeve, and one end of the pipe is fitted in the sealing ring.

[0009] Furthermore, one end of the sleeve and one end of the clamping sleeve are both configured as a disc structure with threaded holes, and the fixing member is a threaded rod. This ensures that the sleeve and the clamping sleeve are tightly fixed together, eliminating axial stress transmission.

[0010] Furthermore, multiple channels are formed from one end face of the deformable block along its axial direction, terminating in front of its other end face.

[0011] Furthermore, the plurality of channels are arranged sequentially along the axial direction of the deformable block, and the extension directions of two adjacent channels are opposite.

[0012] Furthermore, the deformable block includes: a first truncated cone structure and a second truncated cone structure arranged coaxially, both the first and second truncated cone structures being truncated cone structures with opposite inclination directions of the cone surfaces, an annular groove being formed at the connection between the first and second truncated cone structures, the first and second truncated cone structures being integrally formed, and the diameters of the circular surfaces of the first and second truncated cone structures that are close to each other being the same.

[0013] Furthermore, the first mating channel mates with the second conical pedestal structure, and the first mating channel is a first conical channel that matches the slope of the conical surface of the second conical pedestal structure. The second mating channel includes a straight channel and a second conical channel that matches the slope of the conical surface of the first conical pedestal structure. The straight channel and the second conical channel are connected, and the first conical pedestal structure abuts against the second conical channel.

[0014] Furthermore, the oil injection pipe and the clamping sleeve cavity are arranged vertically.

[0015] Furthermore, the diameter of the clamping sleeve cavity is larger than the diameter of the pipe, and the outer ring and inner ring of the sealing ring are respectively sealed to the clamping sleeve cavity and the pipe.

[0016] Compared with the prior art, the beneficial effects of this utility model are:

[0017] This invention combines the tensile and compressive fatigue loads applied by a fatigue machine axially clamped at the clamping end with the circumferential stress applied by the oil pressure of the injection pipe. It eliminates the need for complex biaxial mechanical equipment to simultaneously clamp and apply loads to the outside and inside of the pipe, avoiding the test structure deviations caused by uneven or inaccurate application of two independent loads, which is common with complex biaxial mechanical equipment. Furthermore, this invention uses fixing components to secure the clamping sleeve and the sleeve itself, resulting in a more uniform preload on the pipe and reducing localized high stress concentrations, clamping damage, and slippage on the pipe surface caused by traditional mechanical clamps. This improves the accuracy of test data, avoids excessive damage to the sample end that could interfere with fatigue life test results, and achieves biaxial or multiaxial coupling of the pipe. It better simulates the comprehensive stress state experienced by the pipe or pipeline in actual use environments, improving the reliability and representativeness of experimental results.

[0018] This utility model consists of a threaded sleeve, a deformation block, a sleeve, and a clamping sleeve. The threaded sleeve and the sleeve are connected by threads, and the sleeve and the clamping sleeve are connected by a threaded rod. The overall structure is compact, and the installation, disassembly, and replacement of pipe samples on the mold are very convenient, which can reduce experimental preparation time and improve testing efficiency.

[0019] This invention allows for the adjustment and replacement of sealing rings based on different pipe sizes and material properties, in order to adapt to the testing needs of pipe fittings of different specifications and materials. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the clamping and loading component structure of this utility model.

[0021] Figure 2 This is a schematic diagram of the deformable block structure of this utility model.

[0022] Figure 3 for Figure 1An enlarged view of the structural diagram of the central A region.

[0023] Among them, 1. Threaded sleeve, 11. First mating channel, 2. Deformation block, 21. Clamping channel, 22. First conical structure, 23. Second conical structure, 24. Annular groove, 25. Channel, 3. Sleeve, 31. Second mating channel, 4. Clamping sleeve, 41. Clamping sleeve cavity, 42. Oil injection pipe, 43. Clamping end, 5. Screw, 6. Sealing ring, 7. Pipe. Detailed Implementation

[0024] The following is combined Figures 1 to 3 The specific embodiments of this utility model will be described in detail below. In the description of this utility model, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0025] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature; in the description of this utility model, unless otherwise stated, "a plurality of" means two or more.

[0026] It should be noted that the connection between the fatigue machine and the clamping sleeve, as well as the connection between the oil source and the oil injection pipe involved in this utility model, all adopt conventional connection methods and do not involve any innovation.

[0027] Example

[0028] A biaxial fatigue testing mold includes two symmetrically arranged clamping and loading components, which are located at both ends of a tube 7, as shown below. Figure 1 As shown, each clamping and loading assembly includes: a threaded sleeve 1, a sleeve 3, a deformation block 2, and a clamping sleeve 4. The threaded sleeve 1 has a sleeve structure, and its internal space serves as a first mating channel 11. A threaded section is formed on the inner side of one end of the threaded sleeve 1. A threaded section is formed on the outer side of one end of the sleeve 3. The sleeve 3 and the threaded sleeve 1 are threadedly connected through their respective threaded sections. The internal space of the sleeve 3 serves as a second mating channel 31. The deformation block 2 is placed between the first mating channel 11 and the second mating channel 31. Figure 1As shown, the deformation block 2 has a clamping channel 21 along its central axis for the pipe 7 to pass through. The diameter of the clamping channel 21 is slightly larger than the diameter of the pipe 7. One end of the deformation block 2 is sleeved and abuts against one end of the second mating channel 31, and the other end is sleeved and confined in the first mating channel 11. The threaded sleeve 1 is rotated and tightened to cause relative displacement with the sleeve 3. The displacement generated acts on the deformation block 2, so that the clamping channel 21 of the deformation block 2 is tightened circumferentially, thereby circumferentially gripping the pipe 7. The internal space of the clamping sleeve 4 serves as the clamping sleeve cavity 41. One end of the clamping sleeve 4 is connected to the other end of the sleeve 3 via a fastener 5. The clamping sleeve cavity 41 and the clamping channel 21 are coaxially connected. The other end of the clamping sleeve 4 is the clamping end 43, which is used to connect to the fatigue machine. The side of the clamping sleeve 4 is provided with an oil injection pipe 42. One end of the oil injection pipe 42 is connected to the clamping sleeve cavity 41, and the other end of the oil injection pipe 42 is connected to an external oil source, which is an oil filling system. The oil filling system is used to fill the clamping sleeve cavity 41 with oil to achieve uniform circumferential loading on the inner wall of the pipe 7, thereby obtaining a more uniform internal pressure distribution, reducing experimental errors caused by eccentric stress or local stress concentration, and more closely resembling the actual service state. The repeatability and comparability of the test results are better.

[0029] To avoid the problems associated with existing biaxial fatigue molds for pipes, which use wedges with quadrilateral or semi-circular inner walls for pre-tightening clamping, slippage is prone to occur during axial loading, and local stress concentration is likely to occur at the clamping end, leading to fatigue failure of the pipe at the clamping end, reducing the validity of test results, and increasing data dispersion and uncertainty. In some embodiments, the threaded sleeve 1 is fixed together with the sleeve 3 by rotating and tightening, resulting in relative displacement. The resulting displacement acts on the deformation block 2, causing it to clamp the pipe 7 through circumferential force. The cooperation between the threaded sleeve 1, sleeve 3, and deformation block 2 makes the pre-tightening force on the pipe 7 more uniform, avoiding the local stress concentration caused by traditional wedge clamps. The clamping sleeve 4 is fixed together with the sleeve 3 by four long threaded rods, and the fatigue test is achieved by the force applied to the clamping sleeve 4 by the fatigue machine. During axial loading, the circumferential tightening of the deformation block 2 further increases the pre-tightening force on the pipe 7, preventing the pipe from slipping. At this point, all clamping and loading components are fixed together. Excluding axial stress transmission, the circumferential stress of the pipe 7 is mainly controlled by oil filling. The oil source is introduced into the cavity 41 of the clamping sleeve from the oil injection pipe 42 above the clamping sleeve 4, thus achieving circumferential stress distribution in the pipe. This achieves biaxial stress distribution.

[0030] By combining the tensile and compressive fatigue loads applied by the fatigue machine axially clamped on the clamping end 43 with the circumferential stress applied by the oil pressure on the oil injection pipe 42, the pipe 7 is simultaneously clamped and loaded both externally and internally. This reduces the localized high stress concentration or clamping damage to the surface of the pipe 7 caused by traditional mechanical clamps. This improves the accuracy of test data, avoids excessive damage to the sample end that could interfere with fatigue life test results, and achieves biaxial or multiaxial coupling of the pipe 7. It also better simulates the comprehensive stress state experienced by the pipe 7 or pipeline in actual use environments, such as internal pressure and external loads under high temperature and high pressure conditions, improving the reliability and representativeness of experimental results.

[0031] Sealing both ends of the oil filling pipe 42 can effectively prevent leakage caused by thermal expansion and contraction at high temperatures, ensuring the stability and safety of the filling process.

[0032] In some embodiments, such as Figure 3 As shown, a sealing ring 6 is provided at one end of the clamping sleeve cavity 41 near the sleeve 3. When different pipe materials 7 are selected for experiments, by changing the sealing ring 6 of different sizes, and with the fixing effect of the deformation block 2, the pipe material 7 within the specified size range can be fixed. Furthermore, the sealing ring 6 fitted onto the pipe material 7 also provides a sealing effect. The diameter of the clamping sleeve cavity 41 is larger than the diameter of the pipe material 7, and the outer and inner rings of the sealing ring 6 are respectively sealed to the clamping sleeve cavity 41 and the pipe material 7.

[0033] In some embodiments, one end of the sleeve 3 and one end of the clamping sleeve 4 are both configured as a disc structure with threaded holes, and the fixing member 5 is a threaded rod. This ensures that the sleeve 3 and the clamping sleeve 4 are tightly fixed together, eliminating axial stress transmission.

[0034] In some embodiments, such as Figure 2 As shown, multiple channels 25 are formed from one end face of the deformable block 2 along its axial direction, terminating at the other end face. These channels 25 are arranged sequentially along the axial direction of the deformable block 2, with adjacent channels 25 extending in opposite directions. This alternating arrangement of opposing channels allows the wedge to deform more uniformly under stress, avoiding stress concentration and improving structural flexibility. Furthermore, each channel cannot simultaneously penetrate both end faces of the deformable block 2, preserving some of the overall structural strength and allowing for more controlled deformation, preventing excessive weakening of the deformable block 2's structural strength.

[0035] In some embodiments, the deformation block 2 includes a first conical truncated structure 22, a second conical truncated structure 23, and an annular groove 24 coaxially arranged. Both the first conical truncated structure 22 and the second conical truncated structure 23 are conical truncated structures, and the inclination directions of the conical surfaces are opposite. An annular groove 24 is formed at the connection between the first conical truncated structure 22 and the second conical truncated structure 23. The first conical truncated structure 22 and the second conical truncated structure 23 are integrally formed. The diameters of the circular surfaces of the first conical truncated structure 22 and the second conical truncated structure 23 that are close to each other are the same, so that the deformation block 2 can contract simultaneously from two directions through the first conical truncated structure 22 and the second conical truncated structure 33 under the axial displacement of the threaded sleeve 1 and the sleeve 2, thereby improving the clamping and fixing effect on the pipe 7.

[0036] In some embodiments, such as Figure 1 and Figure 2 As shown, the first mating channel 11 mates with the second conical platform structure 23, and the first mating channel 11 is a first conical channel that matches the slope of the conical surface of the second conical platform structure 23. The second mating channel 31 includes a straight channel and a second conical channel that matches the slope of the conical surface of the first conical platform structure 22. The straight channel and the second conical channel are connected. The first conical platform structure 22 abuts against the second conical channel so that when the threaded sleeve 2 and the sleeve 3 are displaced, the displacement force can be uniformly applied to the deformable block 2.

[0037] In some embodiments, such as Figure 1 As shown, the oil injection pipe 42 and the clamping sleeve cavity 41 are arranged vertically to ensure smooth injection of hydraulic oil and to facilitate sealing of the connection between the oil injection pipe 42 and the clamping sleeve cavity 41.

[0038] The above-disclosed embodiments are merely preferred embodiments of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A biaxial fatigue test mold, characterized in that, The system includes two symmetrically arranged clamping and loading components, each of which includes: The threaded sleeve (1) has its internal space serving as the first mating channel (11); A sleeve (3) is threaded to the threaded sleeve (1) at one end, and the internal space of the sleeve (3) serves as a second mating channel (31). The deformation block (2) has a clamping channel (21) for the pipe (7) to pass through. One end of the deformation block (2) is fitted into the first mating channel (11), and the other end is fitted into the second mating channel (31). The channel structure of the first mating channel (11) and the second mating channel (31) matches the structure of the deformation block (2). A clamping sleeve (4) has an internal space that serves as a clamping sleeve cavity (41). One end of the clamping sleeve (4) is connected to the other end of the sleeve (3) via a fastener (5). The clamping sleeve cavity (41) is connected to the clamping channel (21). The other end of the clamping sleeve (4) is a clamping end (43). An oil injection pipe (42) is provided on the side of the clamping sleeve (4). One end of the oil injection pipe (42) is connected to the clamping sleeve cavity (41). A sealing ring (6) is provided at the end of the clamping sleeve cavity (41) near the sleeve (3). One end of the pipe (7) is fitted into the sealing ring (6).

2. The biaxial fatigue test mold according to claim 1, characterized in that, One end of the sleeve (3) and one end of the clamping sleeve (4) are both configured as a disc structure with threaded holes, and the fixing member (5) is a threaded rod.

3. The biaxial fatigue test mold according to claim 1, characterized in that, Multiple channels (25) are opened from one end face of the deformable block (2) along its axial direction, terminating in front of its other end face.

4. The biaxial fatigue test mold according to claim 3, characterized in that, The multiple channels (25) are arranged sequentially along the axial direction of the deformable block (2), and the extension directions of two adjacent channels (25) are opposite.

5. A biaxial fatigue test mold according to claim 3, characterized in that, The deformable block (2) includes a first conical truncated structure (22) and a second conical truncated structure (23) arranged coaxially. Both the first conical truncated structure (22) and the second conical truncated structure (23) are conical truncated structures, and the inclination directions of the conical surfaces are opposite. An annular groove (24) is opened at the connection between the first conical truncated structure (22) and the second conical truncated structure (23).

6. The biaxial fatigue test mold according to claim 5, characterized in that, The first conical truncated structure (22) and the second conical truncated structure (23) are integrally formed, and the diameters of the circular surfaces of the first conical truncated structure (22) and the second conical truncated structure (23) that are close to each other are the same.

7. A biaxial fatigue test mold according to claim 5, characterized in that, The first mating channel (11) mates with the second conical truncated structure (23), and the first mating channel (11) is a first conical channel that matches the slope of the conical surface of the second conical truncated structure (23). The second mating channel (31) includes: a straight channel and a second conical channel that matches the slope of the conical surface of the first conical truncated structure (22). The straight channel and the second conical channel are connected. The first conical truncated structure (22) abuts against the second conical channel.

8. The biaxial fatigue test mold according to claim 1, characterized in that, The oil injection pipe (42) and the clamping sleeve cavity (41) are arranged vertically.

9. A biaxial fatigue test mold according to claim 1, characterized in that, The diameter of the clamping sleeve cavity (41) is larger than the diameter of the pipe (7), and the outer ring and inner ring of the sealing ring (6) are respectively sealed to the clamping sleeve cavity (41) and the pipe (7).

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