Thermal fatigue test system for ceramic matrix composite material test piece

Abstract

The invention belongs to the technical field of structural mechanical property evaluation of ceramic matrix composite parts, and provides a thermal fatigue test system of a ceramic matrix composite test piece, the thermal fatigue test system comprises a chassis and a tray, an adjusting bolt is fixedly mounted on the chassis, and a nut is mounted on the adjusting bolt in a threaded manner; the tray is slidably installed on the adjusting bolt and makes contact with the end, away from the chassis, of the nut. A sleeve is fixedly installed on the inner side of the tray, and a test piece is installed on the chassis and located on the outer side of the adjusting bolt. The outer side of the test piece is sleeved with a coil, and the coil penetrates through a groove in the test piece to be fixedly connected with the sleeve. Through cooperative control of an axial adjustable coil and an air nozzle and boundary constraint optimization of a chassis, precise reproduction of a local temperature field and high-fidelity simulation of a thermal mechanical boundary of a test piece of a ceramic matrix composite material in a thermal fatigue test are realized, so that precise control of local high-temperature-low-temperature circulation of a key part is realized.

Description

Technical Field

[0001] This invention belongs to the technical field of structural mechanical property evaluation of ceramic matrix composite parts, and specifically relates to a thermal fatigue testing system for ceramic matrix composite test pieces. Background Technology

[0002] The need for lightweight aero-engines is a key technological direction for improving thrust-to-weight ratio, reducing energy consumption, and extending service life. In recent years, ceramic matrix composites have gradually become ideal candidate materials to replace traditional high-temperature alloy components (such as flame tubes and turbine outer rings) due to their excellent high-temperature resistance (capable of withstanding temperatures above 1200℃), low density (only 1 / 3 that of nickel-based superalloys), and good creep resistance. However, the brittle nature and complex damage mechanisms of ceramic matrix composites (such as crack initiation, propagation, and oxidation failure) pose challenges to their long-term reliability assessment under extreme thermomechanical loads.

[0003] During aero-engine operation, core components such as the flame tube and turbine outer ring are subjected to alternating periods of high-temperature combustion gas impact (instantaneous temperatures can reach over 1500°C) and subsequent low-temperature environments, leading to repeated high- and low-temperature cyclic thermal fatigue. This thermal cycling significantly affects the mechanical properties of the materials, including strength, fracture toughness, and interfacial bonding stability, thereby threatening the service life and safety of the components. Therefore, it is urgent to establish a thermal fatigue testing system in a laboratory environment capable of accurately simulating actual operating conditions to investigate the failure mechanisms of materials and optimize their engineering applications.

[0004] However, existing testing methods have significant limitations when testing ceramic matrix composites: Firstly, traditional thermal fatigue tests often employ overall heating, but due to the stiffness mismatch between ceramic matrix composites and metal fixtures or testing equipment, non-uniform thermal stress concentration can easily occur, even inducing premature failure under unrealistic operating conditions, making it difficult to accurately assess the intrinsic properties of the material. Secondly, critical components of aero-engines only experience extreme temperature shocks in localized areas (such as the combustion surface of the flame tube or the heated surface of the turbine outer ring), and overall heating cannot simulate the dynamic thermal environment of actual localized high-temperature-low-temperature cycles. Furthermore, the non-metallic properties of ceramic matrix composites make them sensitive to thermal shock, and overall heating may introduce additional testing errors.

[0005] Therefore, there is an urgent need for a thermal fatigue testing system for ceramic matrix composite specimens to improve the accuracy of the experiment. Summary of the Invention

[0006] To address the aforementioned problems, this invention proposes a thermal fatigue testing system for ceramic matrix composite test specimens, comprising a chassis and a tray. An adjusting bolt is fixedly mounted on the chassis, and a nut is threaded onto the adjusting bolt. The tray is slidably mounted on the adjusting bolt and contacts the end of the nut away from the chassis. A sleeve is fixedly mounted on the inner side of the tray, and a test specimen is mounted on the chassis, located outside the adjusting bolt. A coil is fitted onto the outer side of the test specimen, and the coil passes through a groove on the test specimen and is fixedly connected to the sleeve.

[0007] Furthermore, several air nozzles are provided on the outer circumference of the test piece. The air nozzles are connected by a fixing bracket set on the outside of the chassis, and the air nozzles are located on the side of the coil away from the chassis.

[0008] Furthermore, the angle between the axis of the jet nozzle and the axis of the test piece is α, where 29°≤a≤31°.

[0009] Furthermore, the airflow pressure ejected from the nozzle is ≥0.5MPa.

[0010] Furthermore, a central positioning boss is provided on the inner side of the chassis, and the central positioning boss is located on the inner side of the sleeve.

[0011] Furthermore, the central positioning boss is made of ceramic material.

[0012] Furthermore, the chassis adopts Ceramic material production.

[0013] Furthermore, the tray is provided with the same number of through holes as the adjusting bolts.

[0014] Furthermore, the coil generates an alternating magnetic field to heat the sleeve.

[0015] Furthermore, both the coil and the nozzle are electrically connected via an infrared-PID closed-loop temperature control system.

[0016] Beneficial effects: 1. This invention achieves accurate reproduction of the local temperature field and high-fidelity simulation of thermomechanical boundaries in thermal fatigue tests of ceramic matrix composite test pieces through the coordinated control of axially adjustable coils and jet nozzles, combined with the optimization of chassis boundary constraints, thereby enabling precise control of local high-temperature-low-temperature cycles in key parts.

[0017] 2. This invention utilizes a chassis... Made of ceramic, the temperature of the clamping area is stably controlled at a low temperature on the platform even in a high-temperature environment, greatly reducing the intensity of thermal interference and truly restoring the mechanical boundary conditions of the component during service.

[0018] 3. This invention provides near-realistic simulation capabilities for components such as combustion chamber liners of aero-engines by using a coil and jet nozzle in conjunction with an infrared-PID closed-loop temperature control system.

[0019] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention can be realized and obtained by means of the structures pointed out in the description and the drawings. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 A schematic diagram of the overall structure of the thermal fatigue testing system in an embodiment of the present invention is shown.

[0022] Figure 2 A schematic diagram of the sleeve structure of the thermal fatigue testing system in an embodiment of the present invention is shown.

[0023] Figure 3 A schematic diagram of the coil structure of the thermal fatigue testing system in an embodiment of the present invention is shown.

[0024] Figure 4 A schematic diagram of the nut structure of the thermal fatigue testing system in an embodiment of the present invention is shown.

[0025] Figure 5 A schematic diagram of the adjusting bolts of the thermal fatigue testing system in an embodiment of the present invention is shown.

[0026] Figure 6 A schematic diagram of the chassis of the thermal fatigue testing system in an embodiment of the present invention is shown.

[0027] Figure 7 A schematic diagram of the structure of the tray of the thermal fatigue testing system in an embodiment of the present invention is shown.

[0028] Figure 8 A schematic diagram of the jet nozzle of the thermal fatigue testing system in an embodiment of the present invention is shown.

[0029] Figure 9 A schematic diagram of the structure of the test piece of the thermal fatigue testing system in an embodiment of the present invention is shown.

[0030] In the diagram, 1. Sleeve; 2. Coil; 3. Nut; 4. Adjusting bolt; 5. Base; 6. Tray; 7. Air nozzle; 8. Test piece. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Example 1, refer to Figure 1 A thermal fatigue testing system for ceramic matrix composite test specimens includes a sleeve 1, a coil 2, a nut 3, an adjusting bolt 4, a base 5, a tray 6, an air nozzle 7, and a test specimen 8. The adjusting bolt 4 is fixedly mounted on the base 5, and the nut 3 is threaded onto the adjusting bolt 4. The tray 6 is slidably mounted on the adjusting bolt 4 and contacts the end of the nut 3 away from the base 5. The sleeve 1 is fixedly mounted on the inner side of the tray 6, located inside the adjusting bolt 4. The test specimen 8 is mounted on the base 5, located outside the adjusting bolt 4. The coil 2 is fitted onto the outer side of the test specimen 8, passing through a groove on the test specimen 8 and fixedly connected to the sleeve 1. Specifically, the coil 2 is arranged circumferentially around the sleeve 1, and after an alternating current is applied, eddy current heating is generated within the wall thickness of the sleeve 1. The nut 3 and the adjusting bolt 4 form a threaded pair, and the lifting displacement of the tray 6 is controlled by the depth of screwing. The sleeve 1 acts as a heat conduction medium; its outer wall is directly heated by electromagnetic induction and radiates heat to the inner wall of the cylindrical test specimen 8. Coil 2 is arranged circumferentially around sleeve 1. When an alternating current is applied, eddy current heating is generated within the wall thickness of sleeve 1. Nut 3 and adjusting bolt 4 form a threaded pair. The lifting and lowering displacement of tray 6 is controlled by the depth of screwing nut 3. Adjusting bolt 4 penetrates tray 6 vertically, with its bottom end abutting against chassis 5 to form a fulcrum. When nut 3 rotates, it drives tray 6 to move axially along adjusting bolt 4. This invention realizes a targeted testing system that precisely controls the local high-temperature-low-temperature cycle of key parts, while simultaneously solving the stiffness matching problem of the material-metal interface, to realistically reflect the thermal fatigue behavior of ceramic matrix composites under typical aero-engine operating conditions. Based on the above technical requirements, this invention proposes an innovative testing scheme, providing a reliable performance evaluation method for the engineering application of ceramic matrix composites.

[0033] This invention utilizes an axially adjustable coil 2 and an air nozzle 7 (see reference). Figure 1The coordinated control of KF (where KF represents the direction of cold air flow), combined with the boundary constraint optimization of chassis 5, enables accurate reproduction of the local temperature field and high-fidelity simulation of the thermomechanical boundary in the thermal fatigue test of ceramic matrix composite specimen 8. Specifically, the use of a lifting sleeve 1 and a four-axis precision positioning mechanism (nut 3, adjusting bolt 4, and tray 6) allows for dynamic adjustment of the position of the thermal test section, completely eliminating thermal damage and thermal expansion mismatch stress in the non-test area caused by overall heating, and reducing the temperature gradient simulation error from >15% in traditional schemes to <5%. The low thermal conductivity (30W / m·K) of the ceramic chassis 5 allows the temperature of the clamping area to be stably controlled below 200℃ in a high-temperature environment of 1300℃, reducing the thermal interference intensity by 85% and realistically restoring the mechanical boundary conditions of the component during service. The innovative integration of high-frequency induction heating (heating rate of 200℃ / s) and jet cooling technology, combined with an infrared-PID closed-loop temperature control system, provides near-realistic simulation capabilities for components such as the combustion chamber bushing of aero-engines.

[0034] refer to Figure 1 Several jet nozzles 7 are arranged around the outer circumference of the test piece 8. The jet nozzles 7 are connected by a fixing bracket located on the outside of the chassis 5, and the jet nozzles 7 are located on the side of the coil 2 away from the chassis 5. Specifically, the jet nozzles 7 are evenly distributed in a 90° circumferential direction, and their jet axis is aligned with the outer surface of the test piece 8 to form a circumferential cooling zone, with an airflow pressure ≥0.5MPa. All parts of the entire system cooperate with each other to ultimately achieve accurate simulation of the thermal fatigue behavior of ceramic matrix composites under typical operating conditions of aero-engines.

[0035] Furthermore, the angle between the axis of the nozzle 7 and the axis of the test piece 8 is α, where 29°≤α≤31°.

[0036] Furthermore, the airflow pressure ejected by the nozzle 7 is ≥0.5MPa. The nozzles 7 are evenly distributed circumferentially at 90°, and their injection axis is aligned with the outer surface of the test piece 8 to form a circumferential cooling zone, with an airflow pressure ≥0.5MPa.

[0037] refer to Figure 7 A central positioning boss is provided on the inner side of the middle of the chassis 5, and the central positioning boss is located inside the sleeve 1. Specifically, the central positioning boss realizes the radial positioning of the test piece 8, and the central positioning boss is made of ceramic material.

[0038] Furthermore, chassis 5 adopts Made of ceramic materials. Specifically, high-temperature resistant and heat-insulating. Ceramic materials can ensure that the temperature of the support surface remains stable below 200°C even at a high temperature of 1300°C, effectively blocking the heat conduction path; and the ceramic material maintains structural rigidity and blocks the transfer of heat to the support structure at high temperatures.

[0039] refer to Figure 7 The tray 6 has the same number of through holes as the adjusting bolts 4. The axial displacement of the nut 3 causes the tray 6 and the fixed sleeve 1 to move synchronously.

[0040] refer to Figure 3 Coil 2 generates an alternating magnetic field to heat sleeve 1.

[0041] Furthermore, coil 2 and nozzle 7 are both electrically connected via an infrared-PID closed-loop temperature control system. Specifically, the infrared-PID closed-loop temperature control system (full name: infrared temperature measurement feedback type proportional-integral-derivative closed-loop temperature control system) includes an infrared temperature measurement module (e.g., an infrared thermal imager), a PID controller, and actuators (coil 2 and nozzle 7). The PID controller, infrared temperature measurement module, coil 2, and nozzle 7 are all electrically connected.

[0042] The embodiments of the present invention employ a cylindrical test piece 8 of ceramic matrix composite material manufactured by SiC / SiC (Silicon Carbide Fiber Reinforced Silicon Carbide Matrix Composite) and MI process (Melt Infiltration), a sleeve 1 made of high-temperature alloy, a lifting device (nut 3, adjusting bolt 4 and tray 6), a heating device (coil 2) and a cooling device (air nozzle 7); it can achieve alternating high and low temperature cycles from 800℃ to 1200℃, with each cycle lasting less than 5 minutes.

[0043] The installation steps of this invention are as follows: First, the chassis 5 is horizontally fixed to the test bench base and leveled with a level. Then, the lifting mechanism consisting of four sets of adjusting bolts 4 and nuts 3 is vertically assembled. The tray 6 is fitted into the nuts 3 and leveled. The sleeve 1 is fixed in the center of the tray 6 through the groove, and the gap between the sleeve 1 and the inner wall of the test piece 8 is controlled to be 0.3-0.5mm. The coil 2 is spirally wound on the outer wall of the sleeve 1 with a turn spacing of 2mm±0.1mm and connected to the water cooling system. The test piece 8 is vertically installed into the positioning boss of the chassis 5. The four sets of jet nozzles 7 are evenly distributed in a 90° circumferential direction. The axis of the jet nozzle 7 is at an angle of 30°±1° with the normal of the test piece 8. The throat is 10mm±0.2mm away from the surface. The air circuit pressure test reaches 1.2 times the working pressure. Finally, the adjusting bolts 4 are manually or driven by a robotic arm to perform a 10mm stroke lifting and lowering verification. When the displacement error is >0.1mm, the thread pair synchronization is adjusted to ensure that the core performance of the system positioning accuracy ±0.05mm and cooling rate meets the standards.

[0044] This invention innovatively proposes a thermal fatigue testing system for cylindrical specimens made of ceramic matrix composites. It overcomes the shortcomings of traditional methods, such as fixed heating zones and uncontrollable temperature gradients, through an axially dynamically adjustable thermal loading mechanism. The system employs a five-module collaborative architecture: the thermal isolation clamping module uses a... The ceramic chassis 5 serves as the core support component, with a central positioning boss at its center for radial positioning of the test specimen 8. It is also heat-resistant and thermally insulated. The ceramic material ensures that the support surface temperature remains stable below 200℃ even at a high temperature of 1300℃, effectively blocking the heat conduction path. The axially adjustable heating module innovatively integrates coil 2 and sleeve 1. Coil 2 is supplied with a 5-20kHz alternating current and is water-cooled and temperature-controlled through a hollow copper tube. Sleeve 1 is made of high-temperature alloy material. The two are connected by tray 6 to achieve precise axial displacement of 0-50mm. Combined with a linear heating rate of 15℃ / s-200℃ / s, it can accurately simulate a gradient temperature field.

[0045] This system achieves precise local thermal field control through axially moving coil 2: the sleeve 1 and the split-type heat insulation structure (i.e., chassis 5) work together to strictly limit the heat loading within the Φ50mm×10mm test area, completely avoiding the problem of material thermal degradation in non-test areas caused by overall heating; combined with infrared thermal imager temperature monitoring, it dynamically maintains the cyclic switching between the 1200℃ high-temperature zone and the 800℃ cooling zone, accurately reproducing the actual service conditions of the hot-end components of the aero-engine. Based on The low thermal expansion characteristics of the ceramic material chassis 5 ensure that the thermal expansion coefficient of the fixture matches the ceramic matrix by more than 90%, eliminating the initiation of false cracks caused by boundary condition distortion. This system possesses rapid cooling capabilities, stemming from its air compression cooling jet system (connected to a compressor and jet nozzle 7 for rapid cooling), enabling the cooling process to be completed in a very short time, meeting the simulation requirements of extreme thermal transient conditions. The intelligent closed-loop control system forms the core of full-process automation: through a dual-loop regulation architecture of a high-frequency power supply, a PID controller, and a pneumatic servo valve, it achieves coordinated control of the induced current and jet flow rate.

[0046] Example 2, refer to Figure 2 Test piece 8, which indirectly heats ceramic matrix composite material through electromagnetic induction heating sleeve 1 (reference) Figure 9 Sleeve 1 serves as a heat transfer medium, and its outer wall is directly heated by electromagnetic induction, radiating heat to the inner wall of cylindrical test piece 8.

[0047] refer to Figure 3 Coil 2 generates an alternating magnetic field to heat sleeve 1; this system is equipped with four nuts 3 (see reference). Figure 4The lifting system, consisting of adjusting bolt 4 and tray 6, is used to adjust the position of sleeve 1 to adapt to various thermal fatigue test sections.

[0048] refer to Figure 5 This system is equipped with four adjusting bolts and nuts 3, which, together with the nuts 3 and the tray 6, form a lifting system to adjust the position of the sleeve 1, making it easy to adapt to various thermal fatigue test sections.

[0049] refer to Figure 6 The chassis 5 is made of high-temperature resistant material. The ceramic material and the base 5 serve to support and limit the test piece 8, preventing it from moving under the impact of high-pressure cooling gas and affecting the thermal fatigue test.

[0050] refer to Figure 7 The system includes a tray 6 and four adjusting bolts and a nut 3. The nuts 3 and adjusting bolts 4 work together to form a lifting system, which is used to adjust the position of the sleeve 1 to adapt to various thermal fatigue test sections.

[0051] refer to Figure 8 The system is equipped with four jet nozzles 7, which are adjusted by bolts. They spray high-pressure cooling air to cool the test piece 8 and achieve thermal fatigue cycle.

[0052] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A thermal fatigue testing system for ceramic matrix composite specimens, characterized in that, The device includes a chassis (5) and a tray (6). An adjusting bolt (4) is fixedly installed on the chassis (5), and a nut (3) is threaded onto the adjusting bolt (4). The tray (6) is slidably installed on the adjusting bolt (4) and contacts the end of the nut (3) away from the chassis (5). A sleeve (1) is fixedly installed on the inner side of the tray (6). A test piece (8) is installed on the chassis (5) and is located outside the adjusting bolt (4). A coil (2) is fitted on the outer side of the test piece (8) and passes through the groove on the test piece (8) and is fixedly connected to the sleeve (1).

2. The thermal fatigue testing system for ceramic matrix composite specimens according to claim 1, characterized in that, The outer circumference of the test piece (8) is provided with several air nozzles (7), which are connected by a fixing frame provided on the outside of the chassis (5), and the air nozzles (7) are located on the side of the coil (2) away from the chassis (5).

3. The thermal fatigue testing system for ceramic matrix composite specimens according to claim 2, characterized in that, The angle between the axis of the jet nozzle (7) and the axis of the test piece (8) is α, where 29°≤a≤31°.

4. A thermal fatigue testing system for ceramic matrix composite specimens according to claim 2 or 3, characterized in that, The airflow pressure ejected by the jet nozzle (7) is ≥0.5MPa.

5. The thermal fatigue testing system for ceramic matrix composite specimens according to claim 1, characterized in that, The chassis (5) has a central positioning boss on its inner side, which is located inside the sleeve (1).

6. The thermal fatigue testing system for ceramic matrix composite specimens according to claim 5, characterized in that, The central positioning boss is made of ceramic material.

7. A thermal fatigue testing system for ceramic matrix composite specimens according to claim 5 or 6, characterized in that, The chassis (5) is made of ceramic material.

8. The thermal fatigue testing system for ceramic matrix composite specimens according to claim 1, characterized in that, The tray (6) has the same number of through holes as the adjusting bolts (4).

9. The thermal fatigue testing system for ceramic matrix composite specimens according to claim 1, characterized in that, The coil (2) generates an alternating magnetic field for heating the sleeve (1).

10. The thermal fatigue testing system for ceramic matrix composite specimens according to claim 9, characterized in that, The coil (2) and the nozzle (7) are both electrically connected through an infrared-PID closed-loop temperature control system.

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