Multilayer thermal protection structure super-high temperature multi-axial force and heat coupling test system and method

Abstract

The application discloses a multilayer thermal protection structure ultrahigh-temperature multi-axial force thermal coupling test system and method, and belongs to the field of multilayer thermal protection structure testing. The system comprises an in-plane loading module, an out-of-plane loading module and an ultrahigh-temperature radiation loading module loaded on a test piece. The in-plane loading module is connected with the outer periphery of the test piece through an in-plane extension type clamp to simulate in-plane fatigue load. The out-of-plane loading module is connected with the end surface of the test piece through an out-of-plane extension type tool to simulate out-of-plane fatigue load. The ultrahigh-temperature radiation loading module is arranged in close contact with the end surface of the test piece, and can ensure the constancy of the loading temperature while providing high-temperature load. The application solves the problem that the existing test method cannot simultaneously load the in-plane load, the out-of-plane load and the high-temperature load, so that the real value of the ultrahigh-temperature load and the complex stress borne by the multilayer thermal protection structure cannot be obtained, and the actual reference value is low.

Description

Technical Field

[0001] This invention belongs to the field of multilayer thermal protection structure testing, specifically relating to a multilayer thermal protection structure ultra-high temperature multiaxial force thermal coupling test system and method. Background Technology

[0002] Hypersonic vehicles, combining high speed, strong penetration capability, good stealth, and short reaction time, have become a core technology pursued by the aviation industry and a crucial direction for the development of the aerospace industry now and for a considerable period to come. Compared to subsonic and supersonic vehicles, hypersonic vehicles face a more severe aerodynamic heating challenge during flight. The high temperatures generated by aerodynamic heating can easily cause ablation of the vehicle's shape, and its internal equipment may also malfunction. To avoid these adverse consequences, effective thermal protection structures must be employed.

[0003] It is worth noting that aerospace structures are frequently subjected to multiaxial stress during use, which places higher demands on the safety and reliability of thermal protection structures. Furthermore, single types of thermal protection materials and structures are insufficient to meet the corresponding load-bearing and heat insulation requirements, leading to the development of multi-layered integrated thermal protection structures. Therefore, experimental research on multiaxial force-thermal coupling of thermal protection structures for hypersonic vehicles under ultra-high temperature environments is particularly important and has significant implications for advancing hypersonic vehicle technology.

[0004] To comprehensively verify the performance of multilayer thermal protection structures under ultra-high temperature and multiaxial force-thermal coupling environments, it is necessary not only to simulate the actual thermal load environment but also to simultaneously apply multiaxial static and fatigue loads during the test. Currently, the publicly available force-thermal coupling test methods for C / SiC multilayer thermal protection structures provide the thermal load environment through electrically heated ceramic resistance plates, which has drawbacks such as slow heating rates; and can only apply out-of-plane static loads, not multiaxial fatigue loads. Published virtual thermal coupling test methods use quartz lamp heating, and the operating temperature cannot exceed 1000 degrees Celsius; the size of the quartz lamp limits the use of this device for small test pieces, etc.

[0005] In summary, existing technologies cannot adequately simulate the ultra-high temperature loads and complex stresses experienced by the multi-layered thermal protection structure of hypersonic vehicles under actual operating conditions. Therefore, this invention addresses the need for ultra-high temperature multiaxial force thermal coupling tests on multi-layered thermal protection structures by establishing a principle-based experimental method for the ultra-high temperature multiaxial force thermal coupling response characteristics of multi-layered thermal protection structures suitable for small test pieces. Summary of the Invention

[0006] The technical problem to be solved:

[0007] To overcome the shortcomings of existing technologies, this invention provides a multi-layer thermal protection structure ultra-high temperature multiaxial force thermal coupling test system and method, which integrates in-plane load, out-of-plane load, and high temperature load (above 1200 degrees Celsius). Combined with special tooling, it can achieve precise loading of the testing machine, solving the problem that existing test methods cannot simultaneously handle in-plane load, out-of-plane load, and high temperature load, resulting in difficulty in obtaining the true value of ultra-high temperature load and complex stress borne by multi-layer thermal protection structures, and low practical reference value.

[0008] The technical solution of the present invention is: a multi-layer thermal protection structure ultra-high temperature multiaxial force thermal coupling test system, including an in-plane loading module, an out-of-plane loading module and an ultra-high temperature radiation loading module loaded on the test piece;

[0009] The in-plane loading module is connected to the outer periphery of the test piece through an in-plane extension fixture. The multiaxial loading force applied by the in-plane loading module is transmitted to the test piece along a set direction through the in-plane extension fixture to simulate in-plane fatigue load.

[0010] The out-of-plane loading module is connected to the end face of the test piece through an out-of-plane extension tooling. The loading force of the out-of-plane loading module is applied vertically to the end face of the test piece through the out-of-plane extension tooling to simulate out-of-plane fatigue load.

[0011] The ultra-high temperature radiation loading module is fitted to the end face of the test piece, which can ensure the constant loading temperature while providing high temperature loading.

[0012] A further technical solution of the present invention is: the test piece is a cross-shaped multi-layer thermal protection structure, including a heat-resistant layer, a heat-insulating layer and a cold structure layer arranged in sequence, wherein the heat-resistant layer serves as a high-temperature loading surface and is opposite to and attached to the ultra-high temperature radiation loading module, and the length of the heat-resistant layer at the end of the cross shape is greater than that of the heat-resistant layer and the heat-insulating layer, for connecting the in-plane extended clamp.

[0013] A further technical solution of the present invention is as follows: the in-plane extension fixture includes a positioning plate, a fixing plate, and a cooling channel. One end of the positioning plate serves as a loading end and is connected to the in-plane loading module, while the other end serves as a force-applying end and is connected to the end of the heat-insulating layer of the test piece. The force-applying end of the positioning plate is provided with a mounting surface for the end of the heat-insulating layer. The fixing plate is fastened to the mounting surface of the end of the heat-insulating layer by fasteners, and the end of the heat-insulating layer is clamped and fixed between the force-applying end of the positioning plate and the fixing plate, thereby realizing the in-plane extension of the end of the heat-insulating layer. The cooling channel is connected to a water chiller to reduce heat transfer of the in-plane extension fixture.

[0014] A further technical solution of the present invention is: the in-plane loading module is a multi-axis fatigue testing machine, including loading heads arranged in the positive and negative XY directions in the plane, and the four loading heads are respectively connected to the four ends of the test piece through in-plane extension fixtures, with the loading direction being parallel to the extension direction of the four ends.

[0015] A further technical solution of the present invention is: the out-of-plane extension fixture includes a vertical plate, which is set perpendicular to the two end faces of the test piece, and has reinforcing ribs on both sides; a first vertical plate located on one side of the cold structural layer is vertically fixed at the center of the cross of the cold structural layer; there are two second vertical plates located on one side of the heat-insulating layer, which are respectively vertically fixed to the surfaces of two oppositely arranged in-plane extension fixtures; the out-of-plane loading force applied to the test piece by the out-of-plane loading module is received through the vertical plates set at both ends of the test piece.

[0016] A further technical solution of the present invention is: the out-of-plane loading module has a traction rope and weights, one end of which is connected to a vertical plate and the other end is connected to the weights. The out-of-plane loading force on the test piece can be adjusted by increasing or decreasing the number of weights or changing their specifications.

[0017] A further technical solution of the present invention is as follows: the ultra-high temperature radiation loading module includes a shell and an electromagnetic induction coil disposed therein; a through hole is opened on one side wall of the shell, and a silicon carbide heating element is installed in the through hole; a high-temperature resistant insulation board is fixed on the outer wall of the shell around the through hole, and a 25mm channel is opened on the high-temperature resistant insulation board to form a heating window, the inlet of the channel is opposite to the silicon carbide heating element, and the outlet of the channel is opposite to the test piece; the heating temperature of the silicon carbide heating element by the electromagnetic induction coil is controlled by a temperature control box, and the heat is transferred to the test piece through the channel to complete the high-temperature loading;

[0018] The inner wall of the outer casing is equipped with water-cooling pipes, which are connected to a water chiller to reduce the temperature of the outer casing through circulating water.

[0019] A further technical solution of the present invention is: it also includes an acquisition module, which includes an in-plane multi-axis force and displacement data acquisition module, a temperature acquisition module, and a strain acquisition module;

[0020] The in-plane multiaxial force-displacement data acquisition module is installed on a multiaxial fatigue testing machine and acquires data while loading is in progress;

[0021] The temperature acquisition module consists of S-type thermocouples and an infrared thermal imager. There are four S-type thermocouples: one is installed at the center of the radiant heating surface, responsible for feeding back the temperature of the test piece to the temperature control box, thereby achieving precise temperature control; two are installed in the central area at the junction of the insulation layer and the heat protection layer; and one is installed on the outer surface of the cold structural layer. The infrared thermal imager is used to measure the temperature of the entire field, and the S-type thermocouples are used to verify its data to ensure the accuracy of the measured temperature.

[0022] The strain acquisition module uses a high-temperature DIC for measurement.

[0023] A further technical solution of the present invention is: it also includes a fixed module as a frame structure, the top of which is slidably connected to the outer shell of the ultra-high temperature radiation loading module through a slide rail; and a support frame is provided on its top to support and limit the direction of force applied by the traction rope.

[0024] A method for ultra-high temperature multiaxial force thermal coupling test of a multilayer thermal protection structure, the specific steps of which are as follows:

[0025] The test piece is fixedly connected to the four loading heads of the in-plane loading module by four in-plane extension clamps;

[0026] Install the ultra-high temperature radiation loading module onto the fixed module and adjust its position so that the heating window is in contact with the radiated heating surface of the test piece.

[0027] The modules of the multi-layer thermal protection structure ultra-high temperature multiaxial force thermal coupling test system were activated to conduct a loading test;

[0028] The in-plane multi-axis force and displacement data acquisition module feeds back the real-time measurement data to the host computer to adjust the loading force.

[0029] The temperature acquisition module feeds back the real-time measurement data to the temperature control box, which adjusts the loading current to achieve precise control of the loading temperature.

[0030] The global strain of the test specimen is measured using a strain acquisition module.

[0031] Beneficial effects

[0032] The beneficial effects of this invention are as follows: This invention combines in-plane and out-of-plane loading modules. By designing specialized fixtures and tooling, it can simultaneously apply in-plane and out-of-plane loading forces to the test piece, and the loading force can be flexibly and precisely adjusted. Simultaneously, the ultra-high temperature radiation loading module is positioned on one side of the radiated heating surface of the test piece. Based on its heating window design, ultra-high temperature loading can be achieved on small test pieces. Therefore, this invention can conduct principle-based tests on the ultra-high temperature multiaxial force-thermal coupling response characteristics of multi-layer protective structures, closely resembling real-world application scenarios, ensuring test accuracy and providing realistic reference data for the practical application of multi-layer protective structures. Specific advantages are analyzed as follows:

[0033] 1. This invention employs an ultra-high temperature radiant heating module, enabling precise thermal load simulation of small, multi-layered thermal protection structures and achieving single-sided radiant heating. This heating method is highly similar to the single-sided aerodynamic heating conditions experienced by the outer surface of hypersonic vehicles, thus ensuring the accuracy and reliability of the test results. Based on electromagnetic induction-driven silicon carbide heating elements for rapid radiant heating, the heating rate can be adjusted within 5-15℃ / s, with a maximum operating temperature of 1500℃. Furthermore, compared to quartz lamp radiant heating, this invention can operate stably for extended periods in ultra-high temperature environments (i.e., 1250 degrees Celsius).

[0034] 2. The present invention uses the above-mentioned multiaxial load simulation module, which can ensure that under high temperature single-sided thermal load, the in-plane multiaxial fatigue load and out-of-plane static load of the test piece can be applied simultaneously, which is more in line with the actual working conditions. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the experimental device structure of the present invention;

[0036] Figure 2 This is a schematic diagram of the ultra-high temperature radiant heating module of the present invention;

[0037] Figure 3 This is a schematic diagram of the small multiaxial test specimen of the present invention;

[0038] Figure 4 This is a schematic diagram of the connection between the in-plane extended clamp 20 and the temperature cooling module of the present invention;

[0039] Figure 5 This is a schematic diagram of the connection between the in-plane extending fixture 20 of the present invention and the test piece;

[0040] Explanation of reference numerals in the attached drawings: 1. Fixing module, 2. Ultra-high temperature radiant heating module, 3. Multi-axis fatigue testing machine, 4. Weight, 5. Traction rope, 6. Water-cooled pipe, 7. Loading head, 8. Support frame, 9. Heating window, 10. High temperature resistant insulation board (mullite), 11. Passageway, 12. Heat-insulating layer (ceramic matrix composite material), 13. Heat-insulating layer (carbon aerogel), 14. Cold structure layer (titanium alloy cold structure), 15. Water-cooled channel, 16. Out-of-plane extended fixture, 17. Fixing plate, 18. Positioning plate, 19. Test piece, 20. In-plane extended clamp. Detailed Implementation

[0041] The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the invention, and should not be construed as limiting the invention.

[0042] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention 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. Therefore, they should not be construed as limitations on this invention.

[0043] Based on the existing requirements for aerospace structural testing and the limitations of current testing methods, the system designed in this invention must strictly meet the following four conditions when applying thermal loads to ensure the realism and accuracy of the simulation: First, the thermal load must be applied to one side of the test piece to simulate the heating conditions of the aircraft during actual flight; second, the thermal load must be able to change rapidly over time to reflect the various thermal environments that the aircraft may encounter during flight; third, the thermal load temperature must be high enough, reaching above 1200 degrees Celsius, to ensure that the test can cover the extreme high-temperature environments that the aircraft may encounter; finally, the test system must be able to operate stably for a long time under ultra-high temperature conditions to ensure the reliability and validity of the test results.

[0044] In applying external loads, the following three key conditions must be met: First, the external loads must meet the requirements of multi-axis loading to simulate the various complex stress states that hypersonic vehicles may encounter during actual use; second, static and fatigue loads need to be applied simultaneously to comprehensively evaluate the performance of the thermal protection structure under multiple loads; and finally, the application of external loads must be stable and controllable during the test to ensure the accuracy of the test results.

[0045] Meanwhile, full-scale structural thermal testing suffers from drawbacks such as large scale, high energy consumption, high cost, and demanding measurement and control technology requirements. In contrast, small-scale structural equivalent testing exhibits significant advantages, effectively reducing testing costs, significantly shortening the testing cycle, and accelerating model development. Therefore, the proposed scheme must fully meet the requirements of small-scale test pieces to ensure its effectiveness and feasibility in practical applications. The implementation of this scheme is expected to overcome many limitations of full-scale structural thermal testing, bringing significant breakthroughs and progress to research and development in related fields.

[0046] Based on the aforementioned problems and requirements, this invention proposes an ultra-high temperature multiaxial force thermal coupling test system for multi-layer thermal protection structures, comprising an in-plane loading module, an out-of-plane loading module, and an ultra-high temperature radiation loading module loaded onto the test piece. The in-plane loading module is connected to the outer periphery of the test piece via an in-plane extended fixture, which transmits the multiaxial loading force applied by the in-plane loading module to the test piece along a predetermined direction to simulate in-plane fatigue load. The out-of-plane loading module is connected to the end face of the test piece via an out-of-plane extended fixture, which applies the loading force of the out-of-plane loading module perpendicularly to the end face of the test piece to simulate out-of-plane fatigue load. The ultra-high temperature radiation loading module is fitted to the end face of the test piece, ensuring the constant loading temperature while providing high-temperature loading. By combining the three loading modules, an ultra-high temperature multiaxial force thermal coupling test on a multi-layer thermal protection structure is completed, enabling the acquisition of accurate and reliable test data.

[0047] The above technical solution will be further explained below with reference to the accompanying drawings and examples:

[0048] In one embodiment, a multiaxial thermal fatigue test was conducted on a small test specimen of a ceramic matrix composite multilayer thermal protection structure under an ultra-high temperature environment, referring to... Figure 1 As shown, the test system used for testing includes an in-plane loading module, an out-of-plane loading module, an ultra-high temperature radiation loading module, a data acquisition module, and a fixing module. The in-plane loading module is a multi-axis fatigue testing machine 3, which includes four loading heads 7 arranged in the positive and negative XY directions. The out-of-plane loading module includes a traction rope 5 and weights 6. The ultra-high temperature radiation loading module 2 is slidably mounted on the fixing module 1.

[0049] In one embodiment, refer to Figure 3 As shown, the test specimen includes a multi-layer thermal protection structure consisting of a heat-insulating layer 12, a heat-insulating layer 13, and a cold structure layer 14. The heat-insulating layer is made of needle-punched ceramic matrix composite material produced by Northwestern Polytechnical University, and its surface is covered with a SiC coating by chemical vapor deposition technology. The heat-insulating layer is made of carbon aerogel produced by National University of Defense Technology, and the cold structure is made of TC2 alloy.

[0050] In one embodiment, the in-plane extension fixture 20 is made of Inconel 718 nickel-based superalloy, a material that maintains excellent strength and stability at high temperatures. Bolts made of the same material as the fixture are used to connect the fixture to the test piece. Furthermore, the in-plane extension fixture 20 employs a unique dovetail clamp structure, which significantly increases the friction between the fixture and the test piece, thereby effectively reducing stress concentration at the edges of the test piece holes and lowering the shear force on the bolts.

[0051] In one embodiment, the fixing module 1 is a frame-type support constructed from 50*50 aluminum alloy profiles, with its bottom fixed to the ground by bolts to ensure the stability of the support. The main function of this support is to fix the ultra-high temperature radiant heating module and the out-of-plane loading module to each other by bolts, ensuring that they maintain a stable and accurate position during use.

[0052] In one embodiment, a temperature cooling module is further included, which includes a water chiller, as shown in the reference. Figure 4 As shown, the water chiller is connected to the ultra-high temperature radiation heating module 3 and the in-plane extension fixture 20 through water cooling pipes and supporting equipment, thereby ensuring that the outer surface temperature of the ultra-high temperature radiation heating module 3 is maintained at room temperature and the temperature of the loading head 7 of the multi-axis fatigue testing machine 3 is stabilized below 100 degrees Celsius.

[0053] In one embodiment, refer to Figure 2 As shown, the ultra-high temperature radiant heating module 3 includes a silicon carbide heating element, an electromagnetic induction coil, a temperature control box, a high-temperature resistant insulation board 10, and a shell. The core working principle of this module is to achieve efficient electromagnetic heating of the silicon carbide heating element by passing a high-frequency current through the electromagnetic induction coil. In the internal structure of the ultra-high temperature radiant heating module, the high-temperature resistant insulation board 10 is designed as a 25mm long heat flow channel. This design not only withstands ultra-high temperature environments but also effectively ensures that heat loss during the transfer process is minimized. The silicon carbide heating element is placed at one end of the channel, while the test piece is placed against the other end. This structural design ensures that the heat generated by the silicon carbide heating element can smoothly pass through the channel and directly reach the surface of the test piece. In this way, single-sided ultra-high temperature radiant heating of the test piece can be achieved. This characteristic allows the ultra-high temperature radiant heating module to realistically simulate the real environment of a multi-layered heat shield structure on a hypersonic vehicle being subjected to aerodynamic heating on one side during hypersonic flight. Meanwhile, an S-type thermocouple is installed at the center of the test specimen to collect temperature signals in real time and transmit them to the temperature control chamber. Based on the received temperature signals, the temperature control chamber intelligently adjusts the current in the heating coil, thereby precisely controlling the heat generated by the silicon carbide heating element and achieving both rapid heating and fine temperature control. The temperature control chamber has multiple settable parameters, including heating rate, maximum temperature, and temperature holding time, to meet the flexible adjustment and precise control requirements of different heat loads.

[0054] In one embodiment, the high-temperature resistant insulation board is made of mullite, and the outer shell is made of 304 stainless steel.

[0055] During flight, hypersonic vehicles are subjected not only to the aforementioned ultra-high temperature loads, but also to in-plane multiaxial dynamic and static fatigue loads and tensile stresses from high-speed airflow on the multiaxial thermal protection structure. To more realistically simulate the actual operating conditions of hypersonic vehicles during flight, a multiaxial load simulation module is implemented.

[0056] In one embodiment, the multi-axis load simulation module consists of several parts, including a multi-axis fatigue testing machine and an out-of-plane load simulation module. The multi-axis fatigue testing machine is a ZYSS series biaxial servo dynamic and static material testing machine manufactured by Changchun Mechanical Science Research Institute Co., Ltd. The in-plane multi-axis load spectrum can be obtained based on the actual flight conditions of the hypersonic vehicle during flight. The out-of-plane load is applied through the out-of-plane load simulation module, which uses pulleys on a fixed module to convert the gravity of the weights into a horizontal tensile force, applied to the multi-layer thermal protection structure. The applied out-of-plane load is changed by altering the mass of the weights.

[0057] In one embodiment, the data acquisition module is divided into an in-plane multiaxial force-displacement data acquisition module, a temperature acquisition module, and a strain acquisition module. The in-plane multiaxial load-displacement data is acquired by the aforementioned multiaxial fatigue testing machine. The temperature acquisition module consists of S-type thermocouples and an infrared thermal imager. There are four S-type thermocouples: one installed at the center of the radiated heating surface, responsible for feeding back the test piece temperature to the temperature control box, thus enabling precise temperature control; two installed at the center of the interface between the insulation layer and the heat-resistant layer; and one installed on the outer surface of the cold structure. The infrared thermal imager is used to measure the overall temperature. Since infrared thermal imager temperature measurements may have errors, S-type thermocouples are used to verify its data to ensure the accuracy of the measured temperature. The strain acquisition module uses a high-temperature DIC for measurement.

[0058] In one embodiment, a method for ultra-high temperature multiaxial force thermal coupling test of a multilayer thermal protection structure includes the following specific steps:

[0059] First, the multiaxial fatigue testing machine 3 is connected to the test piece 19 through the in-plane extension fixture 20, and the in-plane multiaxial fatigue load can be applied to the test piece 19 through the control system of the multiaxial fatigue testing machine 3.

[0060] Secondly, the ultra-high temperature radiation heating simulation module 3 is moved to a predetermined position so that the outlet of the high temperature channel 11 is closely attached to the heating area of ​​the test piece 19, thereby achieving single-sided high temperature radiation to the test piece 19.

[0061] Simultaneously, the temperature at the center of the irradiated surface of the test piece 19 is measured using a thermocouple, and the temperature signal is transmitted to the temperature control box in real time. The temperature control box then adjusts the current in the high-frequency coil flexibly based on the received temperature signal, thereby achieving precise temperature control.

[0062] Next, the out-of-plane load application module is connected to the fixing module 1 by bolts, and the magnitude of the out-of-plane load is controlled by adjusting the mass of the weight 4.

[0063] Finally, the temperature cooling system is connected to the fixture and the ultra-high temperature radiation heating module to ensure that the outer surface temperature of the ultra-high temperature radiation heating module is maintained at room temperature and the temperature of the testing machine clamp is stabilized below 100 degrees Celsius.

[0064] The global strain of the test specimen was obtained using high-temperature digital image correlation (DIC) technology, and the surface temperature of the test specimen was measured by a combination of an S-type thermocouple and an infrared thermal imager.

[0065] Before the formal test, the position of the fixed module needs to be adjusted, and bolts are used to fix it to the ground. The ultra-high temperature radiation heating module and the multi-axis load module are also fixed in the appropriate position of the fixed module to ensure the accuracy of the relative position between the two modules and the test piece, so that the two modules can function normally.

[0066] Fatigue loads were applied using a multiaxial fatigue testing machine, with 45 kg weights used for out-of-plane loading. Temperature loads were controlled by a temperature control box in an ultra-high temperature radiant heating module, with a heating rate set at 10℃ / s, a maximum temperature of 1250℃, and a holding time of 1000s. During the tests, a DIC non-contact strain measurement system was used to acquire strain data on the test specimen surface, thermocouples were used to obtain temperatures at five points, and an infrared thermal imager was used to obtain the global temperature field on the specimen surface. After each test, the specimen was allowed to cool to room temperature before the test process was repeated until the specimen fractured.

[0067] Based on the principle-based experimental method established in this invention, in-depth multiaxial force-thermal coupling experimental research is conducted on small-scale test specimens of multi-layered thermal protection structures under ultra-high temperature environments. This experimental method not only reveals the thermodynamic response characteristics of multi-layered thermal protection structures under different multiaxial load conditions and thermal loads, but also further evaluates their force-thermal damage under repeated force-thermal loads. Most importantly, due to the miniaturized design of the test specimens, experimental costs can be significantly reduced when additional test conditions are required, thereby obtaining richer experimental data and significantly improving experimental efficiency. This innovation provides a more solid experimental support and data foundation for the application of multi-layered thermal protection structures in hypersonic vehicles, and is expected to significantly accelerate the development process of related models, providing strong support for practical applications.

[0068] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A multi-layer thermal protection structure ultra-high temperature multiaxial force thermal coupling test system, characterized in that: It includes an in-plane loading module, an out-of-plane loading module, and an ultra-high temperature radiation loading module loaded onto the test specimen; the test specimen is a cross-shaped multi-layer thermal protection structure, including a heat-resistant layer, a heat-insulating layer, and a cold structural layer arranged in sequence, wherein the heat-resistant layer serves as the high-temperature loading surface and is opposite to and attached to the ultra-high temperature radiation loading module, and the length of the heat-resistant layer at the end of the cross shape is greater than that of the cold structural layer and the heat-insulating layer, which is used to connect the in-plane extended fixture; The in-plane loading module is connected to the outer periphery of the test piece via an in-plane extension fixture. The in-plane extension fixture transmits the multiaxial loading force applied by the in-plane loading module to the test piece along a set direction to simulate in-plane fatigue load. The in-plane extension fixture includes a positioning plate, a fixing plate, and a cooling channel. One end of the positioning plate serves as the loading end, connected to the in-plane loading module, and the other end serves as the force-applying end, connected to the end of the heat-insulating layer of the test piece. The force-applying end of the positioning plate has a mounting surface for the end of the heat-insulating layer. Fasteners secure the fixing plate to the mounting surface of the end of the heat-insulating layer, clamping and fixing the end of the heat-insulating layer between the force-applying end of the positioning plate and the fixing plate, thus achieving in-plane extension of the end of the heat-insulating layer. The cooling channel is connected to a water chiller to reduce heat transfer from the in-plane extension fixture. The out-of-plane loading module is connected to the end face of the test piece through an out-of-plane extension tooling. The loading force of the out-of-plane loading module is applied vertically to the end face of the test piece through the out-of-plane extension tooling to simulate out-of-plane fatigue load. The ultra-high temperature radiation loading module is fitted to the end face of the test piece, which can ensure the constant loading temperature while providing high temperature loading. The ultra-high temperature radiation loading module includes a shell and an electromagnetic induction coil disposed therein. A through hole is opened on one side wall of the shell, and a silicon carbide heating element is installed in the through hole. A high-temperature resistant insulation board is fixed on the outer wall of the shell around the through hole, and a 25mm long channel is opened on the high-temperature resistant insulation board to form a heating window. The inlet of the channel is opposite to the silicon carbide heating element, and the outlet of the channel is opposite to the test piece. The heating temperature of the silicon carbide heating element by the electromagnetic induction coil is controlled by a temperature control box. The heat is transferred to the test piece through the channel to complete the high-temperature loading. A water-cooling pipe is installed on the inner wall of the shell. The water-cooling pipe is connected to a water chiller, and the shell temperature is reduced by circulating water.

2. The ultra-high temperature multiaxial force thermal coupling test system with a multi-layer thermal protection structure according to claim 1, characterized in that: The in-plane loading module is a multi-axis fatigue testing machine, including loading heads arranged in the positive and negative XY directions in the plane. The four loading heads are respectively connected to the four ends of the test piece through in-plane extension fixtures, and the loading directions are parallel to the extension directions of the four ends.

3. The ultra-high temperature multiaxial force thermal coupling test system with a multi-layer thermal protection structure according to claim 2, characterized in that: The out-of-plane extension fixture includes a vertical plate, which is set perpendicular to the two end faces of the test piece and has reinforcing ribs on both sides; a first vertical plate located on one side of the cold structural layer is vertically fixed at the center of the cross of the cold structural layer; there are two second vertical plates located on one side of the heat insulation layer, which are respectively vertically fixed to the surfaces of two oppositely arranged in-plane extension fixtures; the out-of-plane loading force applied to the test piece by the out-of-plane loading module is received through the vertical plates set at both ends of the test piece.

4. The ultra-high temperature multiaxial force thermal coupling test system with a multi-layer thermal protection structure according to claim 3, characterized in that: The out-of-plane loading module includes a traction rope and weights. One end of the traction rope is connected to a vertical plate, and the other end is connected to the weights. The out-of-plane loading force on the test piece can be adjusted by increasing or decreasing the number of weights or changing their specifications.

5. The ultra-high temperature multiaxial force thermal coupling test system with a multi-layer thermal protection structure according to claim 4, characterized in that: It also includes a data acquisition module, which includes an in-plane multi-axis force and displacement data acquisition module, a temperature acquisition module, and a strain acquisition module; The in-plane multiaxial force-displacement data acquisition module is installed on a multiaxial fatigue testing machine and acquires data while loading is in progress; The temperature acquisition module consists of S-type thermocouples and an infrared thermal imager. There are four S-type thermocouples: one is installed at the center of the radiant heating surface, responsible for feeding back the temperature of the test piece to the temperature control box, thereby achieving precise temperature control; two are installed in the central area at the junction of the insulation layer and the heat protection layer; and one is installed on the outer surface of the cold structural layer. The infrared thermal imager is used to measure the temperature of the entire field, and the S-type thermocouples are used to verify its data to ensure the accuracy of the measured temperature. The strain acquisition module uses a high-temperature DIC for measurement.

6. The ultra-high temperature multiaxial force thermal coupling test system with a multi-layer thermal protection structure according to claim 5, characterized in that: It also includes a fixed module with a frame structure, the top of which is slidably connected to the outer shell of the ultra-high temperature radiation loading module via a slide rail; and a support frame is provided on its top to support and limit the direction of force applied by the traction rope.

7. A method for ultra-high temperature multiaxial force thermal coupling test of a multi-layer thermal protection structure, implemented based on the ultra-high temperature multiaxial force thermal coupling test system for a multi-layer thermal protection structure as described in claim 6; characterized in that... The specific steps are as follows: The test piece is fixedly connected to the four loading heads of the in-plane loading module by four in-plane extension clamps; Install the ultra-high temperature radiation loading module onto the fixed module and adjust its position so that the heating window is in contact with the radiated heating surface of the test piece. Start each module of the ultra-high temperature multiaxial force thermal coupling test system for the multi-layer thermal protection structure as described in claim 6, and conduct a loading test; The in-plane multi-axis force and displacement data acquisition module feeds back the real-time measurement data to the host computer to adjust the loading force. The temperature acquisition module feeds back the real-time measurement data to the temperature control box, which adjusts the loading current to achieve precise control of the loading temperature. The global strain of the test specimen is measured using a strain acquisition module.

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