Tension and compression clamp for strong transient thermal gradient fatigue test of hollow sample and use method of tension and compression clamp

Abstract

The invention discloses a tension and compression clamp for a strong transient thermal gradient fatigue test of a hollow sample and a using method, and relates to the field of high-temperature mechanical property tests.The tension and compression clamp comprises two symmetrically-arranged clamps, the two clamps are used for being connected with the two ends of the hollow sample respectively, and each clamp comprises a pull rod, a locking sleeve, a clamping ring and a first cushion block; the locking sleeve is used for fixing the clamping ring and the first cushion block to one end of the pull rod, a first threaded hole used for installing a hollow sample is formed in the clamping ring, and a main airflow channel in the pull rod, a first airflow channel in the first cushion block and a hollow channel of the hollow sample are sequentially communicated. According to the invention, the two clamps can be used for transmitting a tensile / compression load to the hollow sample and providing cooling gas for the hollow sample, so that strong transient thermal gradient tensile / compression fatigue loading of the hollow sample is realized, and a strong transient thermal gradient fatigue test of the hollow sample is carried out.

Description

Technical Field

[0001] The invention relates to the field of high temperature mechanical property test, in particular to a tension and compression fixture for a strong transient thermal gradient fatigue test of a hollow sample and a use method thereof. Background Art

[0002] Turbine components of aircraft engines (turbine blades, turbine disks, etc.) serve under severe thermomechanical cycle loads (high temperature, high pressure, high speed, etc.). Advanced aircraft engines often use high-efficiency cooling technology to ensure that turbine components can work for a long time at ambient temperatures exceeding the heat resistance limit. In fact, the outer edge grooves of turbine blades and turbine disks are usually thin in size and have complex internal cooling paths, which results in a significant temperature difference between the gas side and the cold side of the turbine components along the thickness direction. The actual working thermal environment is a cyclic temperature gradient field. At the same time, for some special high-efficiency cooling technologies such as impingement cooling and film cooling, the distribution of their cooling capacity on the cooled surface is very uneven. The cooling requirements of a large area of ​​the turbine component surface are often met by an array of impingement holes and an array of film holes, which also causes a temperature gradient along the surface of the turbine component, making the actual temperature gradient distribution more complicated. In the presence of a temperature gradient, the mechanical behavior and response of the material are significantly different from those under uniform temperature conditions. Studies have shown that when a large temperature gradient exists, the material life may be reduced by an order of magnitude, which poses a challenge to the high-temperature strength assessment of turbine components.

[0003] In order to effectively study and characterize the differences between the mechanical behavior of high-temperature materials under the action of temperature gradient and uniform temperature field and the corresponding failure mechanism, it is necessary to realize the joint loading of fatigue specimens with tensile and compressive mechanical loads and complex cyclic temperature gradient fields at the experimental level. However, the existing high-temperature fatigue tensile / compression test fixtures are mainly designed for uniform temperature field loading, lack cooling structures for hollow specimens, and cannot directly meet the loading requirements of thermal gradients. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a tension and compression fixture and a method of use for a strong transient thermal gradient fatigue test of a hollow specimen, which can provide cooling gas to the hollow specimen, thereby realizing strong transient thermal gradient tensile / compression fatigue loading of the hollow specimen.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] The present invention provides a tension and compression fixture for a strong transient thermal gradient fatigue test of a hollow specimen, comprising two symmetrically arranged fixtures, the two fixtures being respectively used to connect with two ends of the hollow specimen, the fixture comprising a pull rod, a locking sleeve, a clamping ring and a first cushion block, one end of the pull rod being provided with a groove, the first cushion block being used to be arranged in the groove and protruding from one end of the pull rod, the clamping ring being used to be arranged at one end of the first cushion block away from the pull rod, a first threaded hole for mounting the hollow specimen being arranged inside the clamping ring, the locking sleeve being used to be threadedly mounted on the outside of one end of the pull rod, the locking sleeve being used to fix the clamping ring and the first cushion block to one end of the pull rod, and enabling the two ends of the first cushion block to respectively press against one end of the pull rod and one end of the hollow specimen; a main air flow channel being provided on the pull rod, a first air flow channel being provided on the first cushion block, one end of the main air flow channel being communicated with the outside, and the other end being able to be communicated with one end of the first air flow channel, and the other end of the first air flow channel being used to be communicated with a hollow channel of the hollow specimen.

[0007] Preferably, one end of the pull rod of any of the clamps close to the clamping ring is provided with a rotation-stop groove, and one end of the clamping ring close to the pull rod is provided with a rotation-stop protrusion, and the rotation-stop protrusion can extend into the rotation-stop groove.

[0008] Preferably, the clamping ring includes a first circular ring and a second circular ring connected to each other, the outer diameter of the first circular ring is larger than the outer diameter of the second circular ring, and the first threaded hole is arranged on the inner walls of the first circular ring and the second circular ring; the interior of the locking sleeve includes a screw hole section, a first circular hole section and a second circular hole section arranged in sequence, and the locking sleeve is threadedly installed on the outside of one end of the pull rod through the screw hole section, the inner diameter of the first circular hole section is larger than the inner diameter of the second circular hole section, the first circular hole section matches the first circular ring structure, and the second circular hole section matches the second circular ring structure.

[0009] Preferably, the fixture also includes a second pad and an air duct, the second pad is used to replace the first pad, the second pad is provided with a second air flow channel, the second air flow channel includes a second threaded hole and a center hole connected in sequence, the second threaded hole is used to be located near one end of the pull rod, the inner diameter of the second threaded hole is smaller than the inner diameter of the center hole, the main air flow channel, the second threaded hole, the center hole and the hollow channel of the hollow sample can be connected in sequence; one end of the air duct is threadedly installed in the second threaded hole, the other end of the air duct can pass through the center hole and extend into the hollow channel of the hollow sample, and an annular air flow channel exists between the air duct and the center hole and the hollow channel of the hollow sample; the second pad is provided with a first exhaust hole, the locking sleeve is provided with a second exhaust hole, one end of the first exhaust hole is connected to the annular air flow channel, and the other end is connected to the outside through the second exhaust hole.

[0010] Preferably, the second cushion block is provided with a plurality of the first exhaust holes in sequence along the circumferential direction, and the axial direction of the first exhaust holes is perpendicular to the axial direction of the pull rod; the locking sleeve is provided with a plurality of the second exhaust holes in sequence along the circumferential direction, and the axial direction of the second exhaust holes is perpendicular to the axial direction of the pull rod.

[0011] Preferably, when the first cushion block is disposed at one end of the pull rod, the axial direction of the first airflow channel is consistent with the axial direction of the pull rod; when the second cushion block is disposed at one end of the pull rod, the axial direction of the second airflow channel is consistent with the axial direction of the pull rod.

[0012] Preferably, a mounting groove is provided at a joint between the main airflow channel on the pull rod and the first cushion block or the second cushion block, and a first annular sealing gasket is provided in the mounting groove.

[0013] Preferably, the clamp also includes a second annular sealing gasket, and the first gasket and the second gasket are both provided with a convex stop at one end away from the pull rod, and the convex stop is used to extend into a concave stop on an end face of the hollow specimen, and the height of the convex stop is smaller than the height of the concave stop, and the second annular sealing gasket is used to be arranged between the convex stop and the concave stop.

[0014] Preferably, the main airflow channel includes an axial airflow channel and a connecting airflow channel. The axial airflow channel is arranged along the axial direction of the pull rod. The connecting airflow channel is perpendicular to the axial airflow channel. The two ends of the connecting airflow channel are respectively connected to the outside world and one end of the axial airflow channel, and the other end of the axial airflow channel is connected to the groove.

[0015] The present invention also provides a method for using a tension and compression fixture for a hollow specimen strong transient thermal gradient fatigue test, comprising the following steps:

[0016] Step 1: complete the assembly of the two clamps and the hollow specimen, so that each locking sleeve is separated from one of the pull rods, and install the two clamps on the fatigue testing machine;

[0017] Step 2: Use the fatigue testing machine to perform compression, so that the hollow specimen, the two pull rods and the two first cushion blocks are subjected to a certain pre-pressure, and the absolute value of the pre-pressure can ensure that the loading chain composed of the two clamps and the hollow specimen can still eliminate all contact gaps and thread gaps after the fatigue testing machine is unloaded to a zero-force state, and does not cause damage to the hollow specimen that affects the fatigue test results;

[0018] Step 3, tighten the two locking sleeves, and then remove the pre-pressure applied by the fatigue testing machine in step 2;

[0019] Step 4: introduce cooling gas through the main air flow channel of one of the pull rods, operate the fatigue testing machine and the high-temperature heating device, set the test conditions and start the high-temperature fatigue test.

[0020] Compared with the prior art, the present invention has achieved the following technical effects:

[0021] The tension and compression fixture for the strong transient thermal gradient fatigue test of a hollow specimen of the present invention comprises two symmetrically arranged fixtures, and the two fixtures are respectively used to connect with the two ends of the hollow specimen. The fixture comprises a pull rod, a locking sleeve, a clamping ring and a first pad. The locking sleeve is used to fix the clamping ring and the first pad to one end of the pull rod. A first threaded hole for installing the hollow specimen is arranged inside the clamping ring. The main air flow channel on the pull rod, the first air flow channel on the first pad and the hollow channel of the hollow specimen are connected in sequence. During the test, cooling gas is introduced through the main air flow channel of a pull rod, and the cooling gas flows through the main air flow channel and the first air flow channel of one fixture, the hollow channel of the hollow specimen, and the first air flow channel and the main air flow channel of another fixture in sequence. In the present invention, the two fixtures can transmit tensile / compressive loads to the hollow specimen and provide cooling gas for the hollow specimen, thereby realizing strong transient thermal gradient tensile / compressive fatigue loading of the hollow specimen to carry out a strong transient thermal gradient fatigue test of the hollow specimen. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 A cross-sectional view of a tension and compression fixture for a strong transient thermal gradient fatigue test of a hollow specimen provided in the first embodiment of the present invention;

[0024] Figure 2 A working principle diagram of a tension and compression fixture for a strong transient thermal gradient fatigue test of a hollow specimen provided in the first embodiment of the present invention;

[0025] Figure 3 A schematic diagram of the installation of the first cushion block in the tension and compression fixture for the strong transient thermal gradient fatigue test of hollow specimens provided in the first embodiment of the present invention;

[0026] Figure 4 A schematic structural diagram of a pull rod provided with a rotation-stop groove in a tension-compression fixture for a strong transient thermal gradient fatigue test of a hollow specimen provided in Embodiment 1 of the present invention;

[0027] Figure 5 A schematic structural diagram of a clamping ring provided with a rotation-stopping protrusion in a tension-compression fixture for a hollow specimen strong transient thermal gradient fatigue test provided in the first embodiment of the present invention;

[0028] Figure 6 A schematic structural diagram of a pull rod without a rotation-stop groove in a tension-compression fixture for a strong transient thermal gradient fatigue test of a hollow specimen provided in the first embodiment of the present invention;

[0029] Figure 7 A schematic structural diagram of a clamping ring without a rotation-stopping protrusion in a tension-compression fixture for a strong transient thermal gradient fatigue test of a hollow specimen provided in the first embodiment of the present invention;

[0030] Figure 8 A cross-sectional view of a tension and compression fixture for a strong transient thermal gradient fatigue test of a hollow specimen provided in the second embodiment of the present invention;

[0031] Fig. 9 A working principle diagram of a tension and compression fixture for a strong transient thermal gradient fatigue test of a hollow specimen provided in the second embodiment of the present invention;

[0032] Fig.10 A cross-sectional view of the connection between a clamp and a specimen in a tension and compression clamp for a hollow specimen strong transient thermal gradient fatigue test provided in the second embodiment of the present invention;

[0033] Fig.11 A schematic diagram of the installation of a second cushion block and an air duct in a tension-compression fixture for a strong transient thermal gradient fatigue test of a hollow specimen provided in the second embodiment of the present invention;

[0034] Fig.12 A schematic diagram of the structure of an air duct in a tension and compression fixture for a strong transient thermal gradient fatigue test of a hollow specimen provided in the second embodiment of the present invention;

[0035] Fig.13 A schematic diagram of the structure of the second cushion block in the tension and compression fixture for the strong transient thermal gradient fatigue test of hollow specimens provided in the second embodiment of the present invention;

[0036] Fig.14 This is a schematic structural diagram of a locking sleeve in a tension and compression fixture for a strong transient thermal gradient fatigue test of a hollow specimen provided in the second embodiment of the present invention.

[0037] Explanation of the accompanying drawings: 1. Pull rod; 2. Locking sleeve; 3. Clamping ring; 31. First circular ring; 32. Second circular ring; 4. First gasket; 5. Connecting air flow channel; 6. Axial air flow channel; 7. First air flow channel; 8. Hollow specimen; 9. Mounting groove; 10. Convex stopper; 11. Anti-rotation groove; 12. Anti-rotation protrusion; 13. Second gasket; 14. Air duct; 15. First exhaust hole; 16. Second exhaust hole; 17. Annular air flow channel. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] The purpose of the present invention is to provide a tension and compression fixture for a strong transient thermal gradient fatigue test of a hollow specimen and a method of use, which can provide cooling gas to the hollow specimen, thereby realizing strong transient thermal gradient tensile / compression fatigue loading of the hollow specimen.

[0040] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0041] Embodiment 1:

[0042] like Figure 1-Figure 7As shown, this embodiment provides a tension and compression fixture for a strong transient thermal gradient fatigue test of a hollow specimen 8, including two symmetrically arranged fixtures, the two fixtures are respectively used to connect with the two ends of the hollow specimen 8, the fixture includes a pull rod 1, a locking sleeve 2, a clamping ring 3 and a first cushion block 4, one end of the pull rod 1 is provided with a groove, the first cushion block 4 is used to be arranged in the groove and protrude from one end of the pull rod 1, the first cushion block 4 can fit tightly with the groove, the clamping ring 3 is used to be arranged at the end of the first cushion block 4 away from the pull rod 1, a first threaded hole for mounting the hollow specimen 8 is arranged inside the clamping ring 3, both ends of the hollow specimen 8 are provided with external threads matching the first threaded hole structure, one end of the hollow specimen 8 is installed in a first threaded hole and protrudes from the end face of the clamping ring 3 close to the first cushion block 4. The locking sleeve 2 thread is used to be installed on the outside of one end of the pull rod 1. The locking sleeve 2 is used to fix the clamping ring 3 and the first cushion block 4 to one end of the pull rod 1, and can make the two ends of the first cushion block 4 respectively press against one end of the pull rod 1 and one end of the hollow sample 8. At this time, one end of the hollow sample 8 is fixed to the pull rod 1, so that the pull rod 1 can transfer the mechanical load of the fatigue testing machine to the hollow sample 8; a main air flow channel is provided on the pull rod 1, and a first air flow channel 7 is provided on the first cushion block 4. One end of the main air flow channel is connected to the outside world, and the other end can be connected to one end of the first air flow channel 7. The other end of the first air flow channel 7 is used to be connected to the hollow channel of the hollow sample 8.

[0043] During the test, cooling gas is introduced through the main airflow channel of a tie rod 1, and the cooling gas flows through the main airflow channel and the first airflow channel 7 of one fixture, the hollow channel of the hollow sample 8, the first airflow channel 7 and the main airflow channel of another fixture in sequence, and then flows to the atmosphere side by side, so as to build a temperature gradient for the hollow sample 8 and realize rapid cooling of the hollow sample 8. In this embodiment, the two fixtures can transmit tensile / compressive loads to the hollow sample 8 and provide cooling gas for the hollow sample 8, thereby realizing strong transient thermal gradient tensile / compressive fatigue loading of the hollow sample 8, so as to carry out strong transient thermal gradient fatigue test of the hollow sample 8.

[0044] Specifically, cooling gas under different conditions, such as cooling gas with different temperatures and flow rates, can be provided to the hollow sample 8 according to test requirements to adjust the cooling rate and thermal gradient distribution of the hollow sample 8 .

[0045] A stop groove 11 is provided at one end of the pull rod 1 of any clamp in this embodiment, close to the clamping ring 3 , and a stop protrusion 12 is provided at one end of the clamping ring 3, close to the pull rod 1 , and the stop protrusion 12 can extend into the stop groove 11 .

[0046] The anti-rotation protrusion 12 on the clamping ring 3 is embedded in the anti-rotation groove 11 on the pull rod 1 during the fixture installation process. During the process of tightening the locking sleeve 2, it can prevent the locking sleeve 2 from driving the clamping ring 3 to rotate and causing the hollow sample 8 to unscrew, thereby reducing the difficulty of fixture assembly.

[0047] When installing the two clamps, first complete the installation of the clamp with the anti-rotation protrusion 12 and the anti-rotation groove 11, and then complete the installation of the other clamp without the anti-rotation protrusion 12 and the anti-rotation groove 11.

[0048] The clamping ring 3 includes a first circular ring 31 and a second circular ring 32 connected to each other, the outer diameter of the first circular ring 31 is larger than the outer diameter of the second circular ring 32, and the first threaded hole is arranged on the inner wall of the first circular ring 31 and the second circular ring 32; the interior of the locking sleeve 2 includes a screw hole section, a first circular hole section and a second circular hole section arranged in sequence, one end of the pull rod 1 is provided with an external thread matching the screw hole section structure, and the locking sleeve 2 is threadedly installed on the outside of one end of the pull rod 1 through the screw hole section, the inner diameter of the first circular hole section is larger than the inner diameter of the second circular hole section, the first circular hole section matches the structure of the first circular ring 31, and the second circular hole section matches the structure of the second circular ring 32.

[0049] First, install one end of the hollow sample 8 in the clamping ring 3. After the first cushion block 4, the clamping ring 3 and the locking sleeve 2 are installed on one end of the pull rod 1, the pull rod 1 applies a tensile load to the hollow sample 8 through the locking sleeve 2 and the clamping ring 3, and the pull rod 1 applies a compressive load to the hollow sample 8 through the first cushion block 4, which can ensure smooth conversion of tensile / compressive loads.

[0050] The main airflow channel includes an axial airflow channel 6 and a connecting airflow channel 5. The axial airflow channel 6 is arranged along the axial direction of the pull rod 1. The connecting airflow channel 5 is perpendicular to the axial airflow channel 6. The two ends of the connecting airflow channel 5 are respectively connected to the outside and one end of the axial airflow channel 6, and the other end of the axial airflow channel 6 is connected to the groove. Specifically, the axial airflow channel 6 and the groove are both arranged at the center of the pull rod 1.

[0051] Specifically, when the first cushion block 4 is disposed at one end of the tie rod 1, the axial direction of the first airflow channel 7 is consistent with the axial direction of the tie rod 1, and the first airflow channel 7 is disposed at the center of the first cushion block 4. In this embodiment, the central axis of the first airflow channel 7 is colinear with the central axis of the axial airflow channel 6.

[0052] This embodiment also provides a method for using a tension and compression fixture for a hollow specimen strong transient thermal gradient fatigue test, comprising the following steps:

[0053] Step 1: Complete the assembly of the two fixtures and the hollow specimen 8, so that each locking sleeve 2 is separated from a pull rod 1, and install the two fixtures on the fatigue testing machine.

[0054] Specifically, the locking sleeve 2 is sleeved on the outside of the clamping ring 3, and the hollow specimen 8 is threadedly connected to the first threaded hole of the clamping ring 3 through an external thread, and protrudes from the end face of the clamping ring 3 close to the pull rod 1; then, the first cushion block 4 is arranged between the hollow specimen 8 and the pull rod 1, so that the convex stop 10 of the first cushion block 4 is located in the concave stop of the hollow specimen 8, and the other end of the first cushion block 4 is located in the groove of the pull rod 1; finally, the ends of the two pull rods 1 away from the hollow specimen 8 are installed on the fatigue testing machine.

[0055] Step 2: Use a fatigue testing machine to perform compression so that the hollow specimen 8, the two tie rods 1 and the two first pads 4 are subjected to a certain pre-pressure. The absolute value of the pre-pressure can ensure that the loading chain composed of the two clamps and the hollow specimen 8 can still eliminate all contact gaps and thread gaps after the fatigue testing machine is unloaded to a zero-force state, and does not cause damage to the hollow specimen 8 that affects the fatigue test results.

[0056] Step 3: Tighten the two locking sleeves 2, and then remove the pre-pressure applied by the fatigue testing machine in step 2.

[0057] Specifically, the locking sleeve 2 is threadedly installed on the external thread of the pull rod 1 until the locking sleeve 2 is tightened.

[0058] The first gasket 4 in this embodiment can transfer the compressive load between the hollow specimen 8 and the pull rod 1, and bear the pre-pressure during the installation process, so that after the locking sleeve 2 is locked, an axial pre-tightening force is generated between the components, thereby eliminating the contact gap and thread gap between the components during the tensile / compressive load conversion process of the fatigue test.

[0059] Step 4: introduce cooling gas through the main air flow channel of a pull rod 1, operate the fatigue testing machine and the high-temperature heating device, set the test conditions and start the high-temperature fatigue test.

[0060] The cooling air in this embodiment can flow into the hollow sample 8 through the main air flow channel and the first air flow channel 7 of one fixture, and after convection heat exchange with the inner wall of the hollow sample 8, it can be directly discharged into the atmosphere through the first air flow channel 7 and the main air flow channel of another fixture.

[0061] Specifically, the cooling gas enters the axial airflow channel 6 from the connecting airflow channel 5 of a tie rod 1, turns into axial flow under the constraint of the axial airflow channel 6, and flows into the heated hollow specimen 8 undergoing high-temperature fatigue test through a first cushion block 4 with a first airflow channel 7, performs convection cooling on the inner wall surface of the hollow specimen 8, and constructs a temperature gradient along the radial direction of the hollow specimen 8. Subsequently, the heated cooling gas continues to flow into another tie rod 1 through another first cushion block 4 with a first airflow channel 7, and is finally discharged into the atmosphere from the axial airflow channel 6 and the connecting airflow channel 5 of the other tie rod 1.

[0062] In this specific embodiment, a back-pressure valve is provided at one end of the connecting air flow channel 5 of a fixture away from the axial air flow channel 6, that is, a back-pressure valve is installed at the cooling gas discharge of a pull rod 1. By introducing high-pressure cooling gas at the cooling gas inlet of another pull rod 1, the pressure of the internal cooling gas of the tension and compression fixture used for the strong transient thermal gradient fatigue test of the hollow specimen 8 can be increased, the gas density can be increased, and the convective heat transfer effect can be enhanced, thereby achieving the rapid cooling capacity of the hollow specimen 8 or the adjustment of the radial temperature gradient.

[0063] Embodiment 2:

[0064] like Figure 8-Figure 14 As shown, the fixture also includes a second cushion block 13 and an air duct 14. The second cushion block 13 is used to replace the first cushion block 4. The second cushion block 13 is provided with a second air flow channel. The second air flow channel includes a second threaded hole and a center hole connected in sequence. The second threaded hole is used to be located at one end close to the pull rod 1. The inner diameter of the second threaded hole is smaller than the inner diameter of the center hole. The main air flow channel, the second threaded hole, the center hole and the hollow channel of the hollow sample 8 can be connected in sequence; one end of the air duct 14 is threadedly installed in the second threaded hole, and the other end of the air duct 14 can pass through the center hole and extend into the hollow channel of the hollow sample 8. There is an annular air flow channel 17 between the air duct 14 and the center hole and the hollow channel of the hollow sample 8; a first exhaust hole 15 is provided on the second cushion block 13, and a second exhaust hole 16 is provided on the locking sleeve 2. One end of the first exhaust hole 15 is connected to the annular air flow channel 17, and the other end is connected to the outside through the second exhaust hole 16.

[0065] In this specific embodiment, a plurality of first exhaust holes 15 are sequentially arranged on the second cushion block 13 along the circumferential direction, and the axial direction of the first exhaust hole 15 is perpendicular to the axial direction of the pull rod 1; a plurality of second exhaust holes 16 are sequentially arranged on the locking sleeve 2 along the circumferential direction, and the axial direction of the second exhaust hole 16 is perpendicular to the axial direction of the pull rod 1.

[0066] When the first pad 4 is replaced by the second pad 13, that is, the second pad 13 and the air duct 14 are used in the fixture, the second pad 13 can fit tightly with the groove, the second pad 13 protrudes from one end of the tie rod 1, the clamping ring 3 is used to be arranged at the end of the second pad 13 away from the tie rod 1, and one end of the hollow sample 8 is installed in a first threaded hole and protrudes from the end surface of the clamping ring 3 close to the second pad 13. The locking sleeve 2 thread is used to be installed on the outside of one end of the tie rod 1, and the locking sleeve 2 is used to fix the clamping ring 3 and the second pad 13 to one end of the tie rod 1, and can make the two ends of the second pad 13 respectively press against one end of the tie rod 1 and one end of the hollow sample 8.

[0067] Specifically, when the second cushion block 13 is disposed at one end of the rod 1, the second airflow channel is aligned with the axis of the rod 1. The second airflow channel is disposed at the center of the second cushion block 13, and the central axis of the second airflow channel is colinear with the central axis of the axial airflow channel 6 in this embodiment.

[0068] The main air flow channel on the tie rod 1 is provided with a mounting groove 9 at the joint with the first cushion block 4 or the second cushion block 13, and the first annular sealing gasket is provided in the mounting groove 9. When the first cushion block 4 is used, the two ends of the first annular sealing gasket are respectively pressed against the tie rod 1 and the first cushion block 4, thereby achieving the sealing at the joint between the tie rod 1 and the first cushion block 4. When the second cushion block 13 is used, the two ends of the first annular sealing gasket are respectively pressed against the tie rod 1 and the second cushion block 13, thereby achieving the sealing at the joint between the tie rod 1 and the second cushion block 13.

[0069] Both end faces of the hollow sample 8 are provided with concave stoppers. The fixture also includes a second annular sealing gasket, and the first gasket 4 and the second gasket 13 are provided with convex stoppers 10 at one end away from the pull rod 1. The convex stoppers 10 are used to extend into the concave stoppers on one end face of the hollow sample 8. The annular outer side surface of the convex stoppers 10 can fit tightly with the annular inner side surface of the concave stoppers. The coaxiality of the first gasket 4 or the second gasket 13 and the hollow sample 8 is ensured by the cooperation of the convex stoppers 10 and the concave stoppers, ensuring the circumferential uniformity of the cooling effect of the inner wall of the hollow sample 8.

[0070] The height of the male stop 10 is smaller than that of the female stop, and the second annular sealing gasket is used to be arranged between the male stop 10 and the female stop. When the first gasket 4 is used, the two ends of the second sealing gasket are respectively pressed against the first gasket 4 and the hollow sample 8, thereby achieving the sealing at the joint between the first gasket 4 and the hollow sample 8. When the second gasket 13 is used, the two ends of the second sealing gasket are respectively pressed against the second gasket 13 and the hollow sample 8, thereby achieving the sealing at the joint between the second gasket 13 and the hollow sample 8.

[0071] In this specific embodiment, a convex stop 10 is provided at the center of the end of the first cushion block 4 and the second cushion block 13 away from the pull rod 1. The convex stop 10 is a circular ring. The concave stop is provided at the center of an end surface of the hollow sample 8, and the concave stop is a circular groove.

[0072] Specifically, the two air ducts 14 of the two fixtures extend into the hollow sample 8 from both ends respectively, and there is a gap between the two air ducts 14 .

[0073] First, install one end of the hollow sample 8 in the clamping ring 3. After the second gasket 13, the clamping ring 3 and the locking sleeve 2 are installed at one end of the pull rod 1, since the second gasket 13 is set in the groove and protrudes from one end of the pull rod 1, an annular space is formed among the locking sleeve 2, the second gasket 13, the pull rod 1 and the clamping ring 3.

[0074] In this embodiment, a second exhaust hole 16 is provided on the threaded section of the locking sleeve 2 , and the second exhaust hole 16 is connected to the annular space, and the other end of the first exhaust hole 15 is connected to the annular space, thereby achieving the other end of the first exhaust hole 15 connected to the second exhaust hole 16 .

[0075] The flow path of the cooling gas in the two fixtures is the same. Specifically, the cooling gas enters the axial air flow channel 6 from the connecting air flow channel 5 of a pull rod 1, and turns into axial flow under the constraint of the axial air flow channel 6, and flows into the heated hollow specimen 8 undergoing a high-temperature fatigue test through the air duct 14. The air duct 14 constrains the cooling gas to the center height of the hollow specimen 8 and releases it to achieve local cooling, thereby constructing a radial and axial dual temperature gradient inside the wall of the hollow specimen 8, and then flows out to both ends of the hollow specimen 8 along the annular air flow channel 17 between the air duct 14 and the inner wall of the hollow specimen 8, and finally the cooling gas is discharged into the annular space through the first exhaust hole 15 on the second pad 13, and is discharged from the second exhaust hole 16 on the locking sleeve 2.

[0076] Furthermore, the coaxiality between the second cushion block 13 and the hollow sample 8 is ensured by the cooperation of the convex stopper 10 and the concave stopper, and the second air flow channel is located at the center of the second cushion block 13, thereby ensuring the coaxiality between the air duct 14 and the hollow sample 8, thereby ensuring the circumferential uniformity of the local cooling effect at the center height of the hollow sample 8. At the same time, the size of the local cooling range at the center height of the hollow sample 8 can also be adjusted by using air ducts 14 of different lengths.

[0077] This embodiment also provides a method for using a tension and compression fixture for a hollow specimen strong transient thermal gradient fatigue test, comprising the following steps:

[0078] Step 1: Complete the assembly of the two fixtures and the hollow specimen 8, so that each locking sleeve 2 is separated from a pull rod 1, and install the two fixtures on the fatigue testing machine.

[0079] Specifically, the locking sleeve 2 is sleeved on the outside of the clamping ring 3, and the hollow specimen 8 is threadedly connected to the first threaded hole of the clamping ring 3 through an external thread, and protrudes from the end surface of the clamping ring 3 close to the pull rod 1; then, the second cushion block 13 is arranged between the hollow specimen 8 and the pull rod 1, so that the convex stop 10 of the second cushion block 13 is located in the concave stop of the hollow specimen 8, and the air duct 14 extends into the hollow channel of the hollow specimen 8, and the other end of the second cushion block 13 is located in the groove of the pull rod 1; finally, the ends of the two pull rods 1 away from the hollow specimen 8 are installed on the fatigue testing machine.

[0080] Step 2: Use a fatigue testing machine to perform compression so that the hollow specimen 8, the two tie rods 1 and the two second pads 13 are subjected to a certain pre-pressure. The absolute value of the pre-pressure can ensure that the loading chain composed of the two clamps and the hollow specimen 8 can still eliminate all contact gaps and thread gaps after the fatigue testing machine is unloaded to a zero-force state, and does not cause damage to the hollow specimen 8 that affects the fatigue test results.

[0081] Step 3: Tighten the two locking sleeves 2, and then remove the pre-pressure applied by the fatigue testing machine in step 2.

[0082] Specifically, the locking sleeve 2 is threadedly installed on the external thread of the pull rod 1 until the locking sleeve 2 is tightened.

[0083] The second gasket 13 in this embodiment can transfer the compressive load between the hollow specimen 8 and the pull rod 1, and bear the pre-pressure during the installation process, so that after the locking sleeve 2 is locked, an axial pre-tightening force is generated between the components, thereby eliminating the contact gap and thread gap between the components during the tensile / compressive load conversion process of the fatigue test.

[0084] Step 4: Introduce cooling gas through the main air flow channels of the two tie rods 1, operate the fatigue testing machine and the high-temperature heating device, set the test conditions and start the high-temperature fatigue test.

[0085] The present specification uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A tension and compression fixture for hollow specimen strong transient thermal gradient fatigue test, characterized in that: The utility model comprises two symmetrically arranged clamps, which are respectively used to connect with two ends of the hollow sample, and the clamps comprise a pull rod, a locking sleeve, a clamping ring and a first cushion block. A groove is arranged at one end of the pull rod, and the first cushion block is arranged in the groove and protrudes from one end of the pull rod. The clamping ring is arranged at the end of the first cushion block away from the pull rod. A first threaded hole for mounting the hollow sample is arranged inside the clamping ring, and the locking sleeve is used to be threadedly mounted on the outside of one end of the pull rod. The locking sleeve is used to fix the clamping ring and the first cushion block to one end of the pull rod, and can make the two ends of the first cushion block respectively press against one end of the pull rod and one end of the hollow sample; a main air flow channel is arranged on the pull rod, and a first air flow channel is arranged on the first cushion block. One end of the main air flow channel is connected with the outside, and the other end can be connected with one end of the first air flow channel, and the other end of the first air flow channel is used to be connected with the hollow channel of the hollow sample.

2. The tension and compression fixture for hollow specimen strong transient thermal gradient fatigue test according to claim 1 is characterized in that: One end of the pull rod of any of the clamps close to the clamping ring is provided with a rotation-stopping groove, and one end of the clamping ring close to the pull rod is provided with a rotation-stopping protrusion, and the rotation-stopping protrusion can extend into the rotation-stopping groove.

3. The tension and compression fixture for hollow specimen strong transient thermal gradient fatigue test according to claim 1 is characterized in that: The clamping ring includes a first circular ring and a second circular ring connected to each other, the outer diameter of the first circular ring is larger than the outer diameter of the second circular ring, and the first threaded hole is arranged on the inner walls of the first circular ring and the second circular ring; the interior of the locking sleeve includes a screw hole section, a first circular hole section and a second circular hole section arranged in sequence, and the locking sleeve is threadedly installed on the outside of one end of the pull rod through the screw hole section, the inner diameter of the first circular hole section is larger than the inner diameter of the second circular hole section, the first circular hole section matches the first circular ring structure, and the second circular hole section matches the second circular ring structure.

4. The tension and compression fixture for hollow specimen strong transient thermal gradient fatigue test according to claim 1 is characterized in that: The fixture also includes a second pad and an air duct, the second pad is used to replace the first pad, the second pad is provided with a second air flow channel, the second air flow channel includes a second threaded hole and a center hole connected in sequence, the second threaded hole is used to be located near one end of the pull rod, the inner diameter of the second threaded hole is smaller than the inner diameter of the center hole, the main air flow channel, the second threaded hole, the center hole and the hollow channel of the hollow sample can be connected in sequence; one end of the air duct is threadedly installed in the second threaded hole, the other end of the air duct can pass through the center hole and extend into the hollow channel of the hollow sample, and an annular air flow channel exists between the air duct and the center hole and the hollow channel of the hollow sample; the second pad is provided with a first exhaust hole, the locking sleeve is provided with a second exhaust hole, one end of the first exhaust hole is connected to the annular air flow channel, and the other end is connected to the outside through the second exhaust hole.

5. The tension and compression fixture for hollow specimen strong transient thermal gradient fatigue test according to claim 4 is characterized in that: The second cushion block is provided with a plurality of the first exhaust holes in sequence along the circumferential direction, and the axial direction of the first exhaust holes is perpendicular to the axial direction of the pull rod; the locking sleeve is provided with a plurality of the second exhaust holes in sequence along the circumferential direction, and the axial direction of the second exhaust holes is perpendicular to the axial direction of the pull rod.

6. The tension and compression fixture for hollow specimen strong transient thermal gradient fatigue test according to claim 4 is characterized in that: When the first cushion block is disposed at one end of the pull rod, the axial direction of the first airflow channel is consistent with the axial direction of the pull rod; when the second cushion block is disposed at one end of the pull rod, the axial direction of the second airflow channel is consistent with the axial direction of the pull rod.

7. The tension and compression fixture for hollow specimen strong transient thermal gradient fatigue test according to claim 4 is characterized in that: The main airflow channel on the pull rod is provided with a mounting groove at a joint with the first cushion block or the second cushion block, and the mounting groove is used to set a first annular sealing gasket.

8. The tension and compression fixture for hollow specimen strong transient thermal gradient fatigue test according to claim 4 is characterized in that: The clamp also includes a second annular sealing gasket. The first gasket and the second gasket are both provided with a convex stop at one end away from the pull rod. The convex stop is used to extend into a concave stop on an end surface of the hollow specimen. The height of the convex stop is smaller than the height of the concave stop. The second annular sealing gasket is used to be arranged between the convex stop and the concave stop.

9. The tension and compression fixture for hollow specimen strong transient thermal gradient fatigue test according to claim 1 is characterized in that: The main air flow channel includes an axial air flow channel and a connecting air flow channel. The axial air flow channel is arranged along the axial direction of the pull rod. The connecting air flow channel is perpendicular to the axial air flow channel. The two ends of the connecting air flow channel are respectively connected to the outside and one end of the axial air flow channel, and the other end of the axial air flow channel is connected to the groove.

10. A method for using the tension and compression fixture for a hollow specimen strong transient thermal gradient fatigue test as claimed in any one of claims 1 to 9, characterized in that: The following steps are involved: Step 1: complete the assembly of the two clamps and the hollow specimen, so that each locking sleeve is separated from one of the pull rods, and install the two clamps on the fatigue testing machine; Step 2: Use the fatigue testing machine to perform compression, so that the hollow specimen, the two pull rods and the two first cushion blocks are subjected to a certain pre-pressure, and the absolute value of the pre-pressure can ensure that the loading chain composed of the two clamps and the hollow specimen can still eliminate all contact gaps and thread gaps after the fatigue testing machine is unloaded to a zero-force state, and does not cause damage to the hollow specimen that affects the fatigue test results; Step 3, tighten the two locking sleeves, and then remove the pre-pressure applied by the fatigue testing machine in step 2; Step 4: introduce cooling gas through the main air flow channel of one of the pull rods, operate the fatigue testing machine and the high-temperature heating device, set the test conditions and start the high-temperature fatigue test.

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