A fatigue testing fixture and method for a ceramic matrix composite turbine blade disk tenon joint structure

Abstract

This invention relates to a fatigue testing fixture and method for a ceramic matrix composite turbine disk tenon joint structure. The upper and lower ends of the fixture are connected to a fatigue testing machine via a cylindrical clamp, which is threaded to the upper and lower side clamps respectively. The upper clamp of the tenon joint structure mainly consists of an upper clamping plate, an upper connecting plate, an upper clamping block, and a wedge-shaped clamping block. The upper clamping block and the wedge-shaped clamping block are clamped together by an inclined surface on the upper clamping section of the tenon simulation piece. The lower clamp of the tenon joint structure consists of a lower clamping plate and a lower connecting plate. The lower clamping plate is connected to the tenon simulation piece via a square opening slot, and the bottom of the lower clamping plate has cooling water holes. This invention avoids the failure of the composite material clamping section caused by dovetail or pin clamping, and can stably support fatigue or static strength tests of composite material tenon joint structures under tensile loads from room temperature to 1100℃ and from 0N to 100kN.

Description

Technical Field

[0001] This invention belongs to the field of mechanical performance evaluation of the tenon joint structure of ceramic matrix composite turbine disk, specifically relating to a fatigue test fixture and test method for the tenon joint structure of ceramic matrix composite turbine disk. Background Technology

[0002] The tenon joint structure connecting the turbine blades and disks of aero-gas turbine engines operates under harsh conditions of high temperature, high pressure, and high load. Under the interaction of complex loads, the tenon joint, as the connection point between the turbine blades and the turbine disk, experiences additional contact and wear factors, further deteriorating its working environment and making it highly susceptible to fatigue failure. Since turbine blades and turbine disks are critical structural components of aero-engines, failure can have severe consequences. Therefore, it is necessary to conduct research on fatigue performance and fatigue life assessment techniques for tenon joints. With the continuous development of materials technology, ceramic matrix composites, due to their excellent mechanical properties and high-temperature resistance, are gradually becoming ideal next-generation candidate materials for aerospace hot-end components. To accelerate the engineering application of new materials, it is necessary to conduct various strength and fatigue tests under operating temperature conditions in a laboratory environment to investigate the strength and fatigue characteristics of the tenon joints of ceramic matrix composites.

[0003] Considering the brittleness, anisotropy, and multiphase nature of composite materials, testing fixtures and methods applicable to metals present certain challenges. Traditional metal clamping methods include friction clamping, dovetail clamping, and pin clamping. Direct friction clamping using fatigue testing machine grippers at high temperatures may damage the machine. For composite specimens, machining dovetail or pin holes can cause fiber breakage or matrix enrichment areas in the clamping section, potentially leading to specimen breakage and test failure. Furthermore, the non-conductive nature of ceramic matrix composites limits the heating methods of electromagnetic induction coils. Using high-temperature furnaces requires furnaces of different sizes for different specimen dimensions, and the entire fixture set must be made of high-temperature alloy materials, significantly increasing testing costs. Additionally, under heavy load conditions, tenon joints may experience excessive deformation of the tenon groove, leading to tenon slippage. Therefore, in order to ensure the smooth progress of the experiment and avoid the above problems, it is urgent to design a fixture suitable for the test of the tenon joint structure of the turbine disk of ceramic matrix composite material, which can not only ensure the stability of the specimen clamping part, but also flexibly use different heating methods.

[0004] The following significant problems exist in the testing of ceramic matrix composite turbine disk tenon joint structures: (1) How to ensure the stability of the composite specimen clamping, which has characteristics such as brittleness, inability to drill holes, and inability to undergo abrupt changes in cross-section. (2) How to flexibly adopt different heating methods for non-conductive composite specimens according to actual conditions. (3) How to ensure that the tenon joint structure does not slip under high load conditions. After reviewing existing patents and literature, no test fixture design or test method that can solve the above three core problems was found. Therefore, it is necessary to develop a fatigue test fixture and test method for ceramic matrix composite turbine disk tenon joint structures to solve the above problems.

[0005] Chinese invention patent CN201420342894.8 discloses a device for testing the ultra-high temperature tensile properties of carbon / carbon composite materials. Since carbon fibers are conductive, inductive heating can still be used. However, because neither the fibers nor the matrix of ceramic matrix composites are conductive, this method is not suitable for fixture design in fatigue testing of tenon-joint structures.

[0006] Chinese invention patent CN202010271891.X discloses a fixture and testing method for testing the tensile strength of three-dimensional woven composite materials. This method connects the specimen and the fixture by drilling holes in the clamping section, with a total of 10 holes on both sides. However, drilling holes can cause fiber breakage in the composite material, resulting in localized damage. The 10 localized damages in the clamping section of the specimen can easily cause the specimen to break in the clamping section rather than the testing area.

[0007] Chinese invention patent CN201810528413.5 discloses a high-low cycle composite fatigue test fixture for a turbine blade tenon joint structure. The fixture uses a friction clamping method to fix the specimen. However, for composite materials, direct friction clamping by the testing machine may cause the specimen to break. On the other hand, under high temperature conditions, direct clamping of the testing machine is too close to the high temperature zone, which can easily damage the testing machine.

[0008] Chinese invention patent CN201910892049.5 discloses a high-temperature high-load test fixture and test method for a tenon structure. The fixture is connected to the tenon by designing a dovetail-shaped tenon simulation clamping section. However, for composite materials, the dovetail design will cause the fibers to bend and the fiber volume fraction to decrease. This leads to a decrease in the strength of the dovetail part and makes it easy for failure to occur in the clamping section.

[0009] Existing literature, “Zhang Yukun, Chen Yong, Tang Xu. Static strength test method for tenon components of plywood composite fan blades [J / OL]. Propulsion Technology: 1-10 [2022-03-02]” and “Kang Yongqiang, Chen Yong. Interlaminar stress analysis of tenon joints of plywood composite fan blades [J]. Journal of Aerospace Power, 2020, 35(02):388-396”, demonstrates a method of conducting composite tenon joint tests by drilling holes in the specimen clamping area and adding a pad between the specimen and the clamp. However, as analyzed above, drilling holes in the specimen clamping section is very likely to lead to test failure.

[0010] In summary, existing technologies lack a fixture design method suitable for fatigue testing of ceramic matrix composite turbine disk tenon joint structures. This invention addresses the aforementioned problems of non-conductivity and easy failure of the clamping section, and can effectively solve the clamping and heating problems of composite material specimens. Summary of the Invention

[0011] To overcome the shortcomings of existing technologies, this invention proposes a fatigue testing fixture and method for the tenon joint structure of ceramic matrix composite turbine disks. This invention overcomes problems such as the easy failure of the composite material clamping section and the difficulty in applying inductive heating caused by existing designs, improving the versatility of the fixture and reducing testing costs. This invention can be used for static strength, low-cycle fatigue, low-cycle creep, creep, and thermomechanical fatigue tests on the tenon joint structure of ceramic matrix composite turbine disks under high-temperature / room-temperature conditions, testing the strength or lifespan of the tenon joint structure.

[0012] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0013] A fatigue testing fixture for a ceramic matrix composite turbine blade disk tenon joint structure includes: an upper fixture, an upper clamping plate, clamping bolts, an upper clamping block, a wedge-shaped clamping block, an upper clamping plate bolt, an upper connecting plate, an upper connecting plate bolt, a reinforcing plate, a tenon simulation component, a lower connecting plate bolt, a lower connecting plate, a mortise simulation component, a lower clamping plate, cooling water holes, and a lower fixture. One unthreaded cylindrical section of the upper fixture is connected to a fatigue testing machine, and the other end is connected to the internal thread at the upper end of the upper clamping plate via an external thread. The lower sides of the upper clamping plate are positioned relative to each other by upper clamping plate bolts and the central bolt holes of the upper connecting plate. The two upper connecting plates are fixed to the sides of the upper clamping block by upper connecting plate bolts. The upper clamping block and the wedge-shaped clamping block are engaged by inclined surfaces, and the inner side of the wedge-shaped clamping block is connected to the reinforcing plate. The reinforcing plates are glued to both sides of the clamping section of the tenon simulation part; the clamping bolts are screwed in from above the upper clamping block to press the lower wedge-shaped clamping block; the surface of the tenon simulation part is provided with a wear-resistant conductive coating, which mates with the tenon groove simulation part below, and the outer side of the tenon groove simulation part is positioned in conjunction with the opening groove of the lower clamping plate. The lower clamping plate and the lower connecting plate are connected by the lower connecting plate bolt at the opening above the opening groove; the lower internal thread of the lower clamping plate is connected to the external thread of the lower end clamp, and the cylindrical section of the other end of the lower end clamp is connected to the fatigue testing machine; the lower clamping plate is cooled by cooling water through the cooling water holes on both sides of the bottom; when carrying out high-temperature fatigue tests, electromagnetic induction coils or high-temperature furnaces are used to heat the turbine blade disk tenon joint structure.

[0014] Furthermore, the maximum high temperature is 1100℃, and the maximum load is 100kN; the fatigue test includes static strength, low-cycle fatigue, creep-fatigue, creep or thermomechanical loading; the tenon simulation part is one of ceramic matrix composite materials such as SiC / SiC, SiO2 / SiC, Al2O3 / SiC, etc., and the tenon simulation part is one of high temperature alloys such as GH4169, GH4720Li or titanium alloys such as TC4, TC11.

[0015] Furthermore, the load transmission route on the upper side of the fatigue test fixture is as follows: the upper clamp transmits the load to the upper clamping plate through the thread, and the thread is subjected to axial force; the upper clamping plate transmits the load to the upper connecting plate, and the upper connecting plate transmits the load to the upper clamping block, and the thread is subjected to shear force; the upper clamping block transmits the load to the wedge-shaped clamping block through the inclined surface, and the wedge-shaped clamping block transmits the load to the tenon simulation part through friction.

[0016] Furthermore, the friction clamping of the tenon simulation component is ensured by the two upper clamping bolts to prevent the specimen from slipping; the upper clamping block and the wedge-shaped clamping block form a clamping force on the inner side of the wedge-shaped clamping block during loading through the inclined surface, and the inner side of the wedge-shaped clamping block acts on the reinforcing plates on both sides of the clamping section of the tenon simulation component. The surface of the reinforcing plates is knurled to increase the friction; the upper connecting plates on both sides control the upper clamping block, the wedge-shaped clamping block and the tenon simulation component to prevent lateral displacement; the two clamping bolts at the upper end of the upper clamping block are screwed downward along the axial direction and contact the wedge-shaped clamping block, that is, during the assembly of the fixture, the lateral clamping force of the wedge-shaped clamping block on the tenon simulation component is increased to avoid the phenomenon of specimen slippage.

[0017] Furthermore, the material of the lower clamping plate and the lower connecting plate is one of cast high-temperature alloy, single-crystal high-temperature alloy or powder high-temperature alloy, which can withstand a high temperature of up to 1100℃, thereby simulating the load conditions of the real working condition of the ceramic-based turbine disk tenon joint structure.

[0018] Furthermore, two cooling water holes are opened on both sides of the bottom of the lower clamping plate. Cooling water is allowed to flow through the interior of the lower clamping plate through an external water pipe to cool the fixture and reduce the operating temperature of the lower clamping plate.

[0019] Furthermore, the wear-resistant and conductive coating is deposited on the surface of the tenon simulation part after processing. The coating consists of a lubricating layer and a wear-resistant layer. The lubricating layer consists of one or more of the following materials and compounds: gold, silver, borosilicates, etc. The wear-resistant layer consists of one or more of the following: nickel, cobalt, platinum, rhodium, and their oxides. The coating is attached to the surface of the composite material tenon simulation part by electroplating, sputtering, physical or chemical vapor deposition. At the same time, when heating with an inductor coil, the conductivity of the coating can heat the tenon simulation part through heat conduction, so that the composite material tenon simulation part is heated evenly.

[0020] Furthermore, the lower clamping plate adopts an open slot to prevent the tenon simulation part from being dislodged due to excessive deformation, and also to facilitate the assembly of the clamp.

[0021] This invention also discloses a test method for a fatigue test fixture for a ceramic matrix composite turbine blade disk tenon joint structure, characterized by comprising the following steps:

[0022] Step 1: Fatigue Testing Fixture Assembly: First, use adhesive to attach the reinforcing sheet to both sides of the clamping section of the tenon simulation part, and let it stand for a sufficient time to ensure the bonding effect; connect the upper clamping plate to the upper clamping fixture via threads; properly align the upper clamping block and the wedge-shaped clamping block, with the reinforcing sheet clamped inside the wedge-shaped clamping block, then screw in the clamping bolts on the upper side of the upper clamping plate to tighten the wedge-shaped clamping block; use the upper connecting plate bolts to ensure that the upper connecting plate and the upper clamping block are concentric, and then connect the upper connecting plate and the upper clamping plate with the upper clamping plate bolts; use the fatigue testing machine... The upper chuck clamps the upper fixture; connect the tenon and mortise simulation parts, and connect the lower clamping plate to the lower fixture. Then, insert the mortise simulation part into the middle of the lower clamping plate, and fix the lower connecting plate to both sides of the lower clamping plate with the lower connecting plate bolts. The lower fixture is then assembled. The inductor coil is then placed on the tenon joint and its shape is adjusted to ensure that the tenon joint is heated evenly, or a high-temperature furnace is used for heating. Connect the external cooling water to the cooling water hole. The lower chuck of the fatigue machine clamps the cylindrical section of the lower fixture to complete the assembly.

[0023] Step 2: Set fatigue test loading conditions based on the actual working load of the ceramic matrix composite turbine disk tenon joint structure; select several measuring points at the cross-section of the test part of the tenon and mortise simulation parts, and attach strain gauges and thermocouples; turn on the outer cooling water switch and check the water tightness of the passage; connect the inductor coil fitted at the tenon joint to the high-frequency furnace or use a high-temperature furnace for heating, set the temperature and adjust the relative position of the inductor coil and the test part, and ensure that the temperature field conforms to the working temperature field of the ceramic matrix composite turbine disk tenon joint structure by thermocouple reading;

[0024] Step 3: After completing Step 2, conduct a ceramic matrix composite turbine disk tenon joint structure test. Set up a load controller to apply the corresponding load conditions using a fatigue testing machine. At the same time, set up a temperature controller to raise the temperature and correct it according to the actual temperature measured by thermocouples until the actual temperature of the test part reaches the target temperature. Through the coordinated control of the load controller and temperature controller, the mechanical load and temperature load are applied synchronously to the test part. When the test part reaches the specified number of cycles or fails, the test ends.

[0025] The advantages of this invention compared to the prior art are as follows:

[0026] (1) The present invention uses a wedge-shaped clamping block for friction clamping of the ceramic matrix composite tenon simulation part, which avoids the phenomenon of easy failure of the clamping section of the specimen caused by the use of dovetail and pin clamping in the existing design, and also avoids the situation of damage to the testing machine caused by direct clamping of the fatigue testing machine.

[0027] (2) This invention features an innovative coating that combines conductivity and wear resistance for ceramic matrix composites. Since the composite tenon simulation part is constantly in contact and rubs against the metal tenon simulation part during loading, it is prone to wear. Therefore, an electroplating coating process is used to protect the tenon surface and improve its fatigue life. On the other hand, considering that ceramic matrix composites are non-conductive and therefore difficult to heat using inductive heating, and that high-temperature furnace heating is often limited by size and has high fixture processing costs, the good conductivity of the coating allows for the use of flexible electromagnetic coils to heat the tenon simulation part through heat conduction, ensuring uniform heating.

[0028] (3) The present invention has better stability than existing tenon structure fixtures: clamping bolts are used to provide clamping force for clamping the specimen, ensuring that the specimen will not slip, and the clamping force is adjustable; the tenon groove simulation is fixed by using an open groove method, ensuring that the tenon groove simulation will not deform excessively under large load conditions, causing the tenon simulation to slip.

[0029] (4) Compared with existing designs, the design of this invention reduces the amount of high-temperature alloy used in the fixture while improving versatility. When using inductive heating, only the lower connecting plate, lower connecting plate bolts, and lower clamping plate need to use high-temperature alloy. At the same time, when conducting tests on tenon simulation parts of different sizes, only the appropriate tenon simulation parts need to be replaced, and the other parts can be used interchangeably.

[0030] In summary, compared with existing technologies, this invention proposes a fatigue testing fixture design and method for the tenon joint structure of ceramic matrix composite turbine disks. This method overcomes the problem of specimen clamping section failure that easily occurs when using dovetail or pin clamps in existing designs. Furthermore, it innovatively proposes a conductive coating method for inductive heating of composite materials. The fixture's stability, versatility, and cost control are all significantly improved compared to existing technologies, laying a solid experimental foundation for exploring the strength and fatigue performance of tenon joint structures of ceramic matrix composite turbine disks. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the fatigue test fixture for the ceramic matrix composite turbine blade disk tenon joint structure of the present invention;

[0032] Figure 2 This is an exploded view of the fatigue test fixture for the ceramic matrix composite turbine blade disk tenon joint structure of the present invention;

[0033] Figure 3 This is a schematic diagram of the lower tenon joint structure of the fatigue test fixture for the ceramic matrix composite turbine disk tenon joint structure of the present invention. Detailed Implementation

[0034] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the protection scope of the present invention.

[0035] This invention provides a fatigue testing fixture and method for a ceramic matrix composite turbine disk tenon joint structure. In this embodiment, a tenon simulation component 10 is manufactured using SiC / SiC and CVI processes, and a mortise simulation component 13 is manufactured using a GH4720Li dies. The test load is 35 kN, the low-cycle fatigue test stress ratio is 0.1, and the test temperature is 650℃. An electromagnetic induction coil is used to heat the connection between the tenon simulation component 10 and the mortise simulation component 13.

[0036] like Figure 1-2 As shown, the fatigue test fixture for the mortise and tenon structure of the ceramic matrix composite turbine disk of the present invention includes an upper fixture 1, an upper clamping plate 2, clamping bolts 3, an upper clamping block 4, a wedge-shaped clamping block 5, an upper clamping plate bolt 6, an upper connecting plate 7, an upper connecting plate bolt 8, a reinforcing plate 9, a tenon simulation component 10, a lower connecting plate bolt 11, a lower connecting plate 12, a tenon simulation component 13, a lower clamping plate 14, a cooling water hole 15, and a lower fixture 16. The lower connecting plate 12, the lower connecting plate bolt 11, and the lower clamping plate 14 are made of high-temperature alloy, while the rest can be made of titanium alloy or stainless steel. One end of the upper clamp 1, without threads, is a cylindrical section connected to the fatigue testing machine, and the other end is connected to the internal thread at the upper end of the upper clamping plate 2 via an external thread. The two sides of the lower end of the upper clamping plate 2 are positioned by upper clamping plate bolts 6 and the center bolt holes of the upper connecting plate 7. The two upper connecting plates 7 are fixed to both sides of the upper clamping block 4 by upper connecting plate bolts 8. The upper clamping block 4 and the wedge-shaped clamping block 5 are engaged by an inclined surface, and the inner side of the wedge-shaped clamping block 5 is attached to the reinforcing plate 9. The reinforcing plate 9 is fixed to the tenon simulation part 10 by adhesive. The clamping section has two sides; the clamping bolts 3 are screwed in from above the upper clamping block 2 and contact the wedge-shaped clamping block 5 below; the surface of the tenon simulation part 10 is coated with a conductive coating, and it mates with the tenon groove simulation part 13 below. The outer side of the tenon groove simulation part 1 mates with the opening groove of the lower clamping plate 14 for positioning. The lower clamping plate 14 and the lower connecting plate 12 are connected at the opening above the opening groove by the lower connecting plate bolt 11; the lower clamping 14 is connected to the lower end clamping fixture 16 by the lower internal thread and the lower end clamping fixture 16 by the external thread. The other end of the lower end clamping fixture 16 is connected to the fatigue testing machine by the cylindrical section. The lower clamping plate 14 is cooled by cooling water through the cooling water holes 15 on both sides of the bottom, which reduces the operating temperature of the lower clamping plate 14, thereby extending the service life of the fixture and reducing the test cost. When conducting high-temperature fatigue tests, electromagnetic induction coils and high-temperature furnaces can be used to heat the turbine blade disk tenon joint structure.

[0037] The maximum temperature can reach 1100℃, and the maximum load is 100kN. The test includes static strength, low cyclic fatigue, creep-fatigue, creep, thermomechanical loading and other loading methods; the tenon simulation part 10 can be one of the ceramic matrix composite materials such as SiC / SiC, SiO2 / SiC, Al2O3 / SiC, etc., and the tenon simulation part 10 can be one of the high temperature alloys such as GH4169, GH4720Li or titanium alloys such as TC4, TC11.

[0038] The materials of the lower clamping plate 14 and the lower connecting plate 12 are one of cast high-temperature alloy, single-crystal high-temperature alloy or powder high-temperature alloy, which can withstand a high temperature of up to 1100℃, thus simulating the load conditions of the real working condition of the ceramic-based turbine disk tenon joint structure.

[0039] After processing, the tenon simulation part 10 is coated with a wear-resistant and conductive coating. The coating consists of a lubricating layer and a wear-resistant layer. The lubricating layer may be composed of one or more of gold, silver, borosilicates, and their compounds; the wear-resistant layer may be composed of one or more of nickel, cobalt, platinum, rhodium, and their oxides. The coating is applied to the surface of the composite material tenon simulation part 10 by electroplating, sputtering, physical or chemical vapor deposition to minimize wear on the tenon and mortise. Simultaneously, the conductivity of the coating allows for uniform heating of the composite material tenon simulation part 10.

[0040] The assembly of the test fixture includes: first, using adhesive to attach the reinforcing sheet 9 to both sides of the clamping section of the tenon simulation part 10, and allowing it to stand for a sufficient time to ensure the bonding effect. In this test, AB glue was used, and the fixture was left to stand for 24 hours after attachment; the upper clamping plate 2 is connected to the upper clamping fixture 1 via threads. The upper clamping block 4 and the wedge-shaped clamping block 5 are properly fitted together, with the inner side of the wedge-shaped clamping block 5 clamping the reinforcing sheet 9. Then, clamping bolts 3 are screwed into the upper side of the upper clamping plate 2 to press the wedge-shaped clamping block 5. The clamping force on the specimen is controlled by adjusting the length of the clamping bolts 3. The upper connecting plate bolts 8 are used to ensure that the upper connecting plate 7 and the upper clamping block 4 are concentric, and then the upper connecting plate bolts 6 are used to connect the upper connecting plate 7 and the upper clamping plate 2. The upper clamping fixture 1 is clamped with the upper chuck of the fatigue testing machine. Connect the tenon simulation part 10 and the mortise simulation part 13, and connect the lower clamping plate 14 to the lower end clamping fixture 16. Then, insert the mortise simulation part 13 into the middle of the lower clamping plate 14, and fix the lower connecting plate 12 to both sides of the lower clamping plate 14 with the lower connecting plate bolts 11. The lower clamping fixture is now assembled. Next, the inductor coil is sleeved on the tenon joint and its shape is adjusted to ensure that the tenon joint is heated evenly. Cooling water is connected at the cooling water hole 15. Ensure that all mating surfaces have good contact and that the bolt connections are secure. After checking that everything is correct, use the fatigue machine lower chuck to clamp the cylindrical section of the lower end clamping fixture 16. The clamping fixture assembly is now complete.

[0041] During fixture assembly, the upper clamping block 4 and the wedge-shaped clamping block 5, through the inclined surface, form a clamping force on the inner side of the wedge-shaped clamping block 5 during loading. The inner side of the wedge-shaped clamping block 5 acts on the reinforcing plates 9 on both sides of the clamping section of the tenon simulation part 10. The surface of the reinforcing plates 9 is knurled to increase friction. The upper connecting plates 7 on both sides control the upper clamping block 4, the wedge-shaped clamping block 5, and the tenon simulation part 10 to prevent lateral displacement. The two clamping bolts 3 at the upper end of the upper clamping block 4 are screwed downward axially and contact the wedge-shaped clamping block 5, thereby increasing the lateral clamping force of the wedge-shaped clamping block 5 on the tenon simulation part 10 during fixture assembly and preventing the specimen from slipping out. The purpose of the open slot in the lower clamping plate 14 is to prevent excessive deformation of the tenon simulation part 13, which would cause the tenon simulation part 10 to come out, and also to facilitate fixture assembly. The lower connecting plate 12 and the lower clamping plate 14 are connected by lower connecting plate bolts 11 on both sides above the opening slot of the lower clamping plate 14 to fix the lower clamping plate 14 and prevent it from deforming excessively. Figure 3 As shown, the purpose of connecting above the slot is to expose the tenon joint below, facilitating further detailed observation and non-contact measurement during fatigue testing. A speckle pattern is sprayed onto the side of the specimen beforehand, a CCD camera is mounted, and a telecentric lens is configured to observe the deformation during loading and obtain the strain field of the tenon joint structure.

[0042] The load transfer route on the upper side of the test fixture is as follows: the upper clamp 1 transmits the load to the upper clamping plate 2 via threads, where the threads are subjected to axial force; the upper clamping plate 2 transmits the load to the upper connecting plate 7, which in turn transmits it to the upper clamping block 4, where the threads are subjected to shear force; the upper clamping block 4 transmits the load to the wedge-shaped clamping block 5 via an inclined surface, and the wedge-shaped clamping block 5 transmits the load to the tenon simulation piece 10 via friction. This keeps the fatigue testing machine's clamps away from the heating parts of the tenon joint structure, preventing high-temperature damage to the testing machine; at the same time, it achieves friction clamping of the test piece, avoiding test failures caused by dovetail clamping, pin drilling, or other clamping methods due to clamping section failure.

[0043] The friction clamping of the tenon simulation component 10 is ensured by the two upper clamping bolts 3 to prevent the specimen from slipping. Specifically, the clamping method is as follows: the upper clamping block 4 and the wedge-shaped clamping block 5, through the inclined surface, form a clamping force on the inner side of the wedge-shaped clamping block 5 during loading. The inner side of the wedge-shaped clamping block 5 acts on the reinforcing plates 9 on both sides of the clamping section of the tenon simulation component 10. The surface of the reinforcing plates 9 is knurled to increase friction. The upper connecting plates 2 on both sides control the upper clamping block 4, the wedge-shaped clamping block 5, and the tenon simulation component 10 to prevent lateral displacement. The two clamping bolts 3 at the upper end of the upper clamping block 2 are screwed downwards axially, contacting the wedge-shaped clamping block 5. This increases the lateral clamping force of the wedge-shaped clamping block 5 on the tenon simulation component 10 during fixture assembly, preventing the specimen from slipping.

[0044] The purpose of the open slot in the lower clamping plate 14 is to prevent excessive deformation of the tenon simulation part 13, which could cause the tenon simulation part 10 to come out, and also to facilitate the assembly of the fixture. The purpose of connecting above the open slot is to expose the tenon joint below, which facilitates further detailed observation and non-contact measurement tests during fatigue testing.

[0045] The experimental loading conditions for the real working load of the ceramic matrix composite turbine disk tenon joint structure according to the present invention are set. Several measuring points are selected at the test sections of the tenon simulation part 10 and the mortise simulation part 13, and strain gauges and thermocouples are attached. The cooling water switch is turned on, and the water tightness of the passage is checked. The inductor coil fitted at the tenon joint is connected to the high-frequency furnace, the temperature is set, and the relative position of the coil and the test part of the tenon joint is adjusted. The temperature field error between the thermocouple reading and the set temperature field of 650℃ is ensured to be less than ±2℃. Subsequently, the load controller is set to apply the corresponding load conditions using a fatigue testing machine, such as monotonic tension, low-cycle fatigue, low-cycle creep, creep, thermomechanical fatigue, etc. At the same time, the temperature controller is set to raise the temperature and is corrected according to the actual temperature measured by the thermocouple until the actual temperature of the test part reaches the target temperature. Through the coordinated control of the load controller and the temperature controller, the mechanical load and temperature load are synchronously applied to the tenon joint test part. The test ends when the tenon simulation part 10 reaches the specified number of cycles or fails.

[0046] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A fatigue testing fixture for a ceramic matrix composite turbine blade disk tenon joint structure, characterized in that: The components include an upper clamp (1), an upper clamping plate (2), clamping bolts (3), an upper clamping block (4), a wedge-shaped clamping block (5), an upper clamping plate bolt (6), an upper connecting plate (7), an upper connecting plate bolt (8), a reinforcing plate (9), a tenon simulation piece (10), a lower connecting plate bolt (11), a lower connecting plate (12), a tenon simulation piece (13), a lower clamping plate (14), a cooling water hole (15), and a lower clamp (16); the ceramic matrix composite material is brittle and anisotropic. And the characteristics of a multiphase system; the cylindrical section of the unthreaded end of the upper clamp (1) is connected to the fatigue testing machine, and the other end is connected to the internal thread of the upper end of the upper clamp plate (2) through the external thread; the two sides of the lower end of the upper clamp plate (2) are positioned by the upper clamp plate bolts (6) and the center bolt holes of the upper connecting plate (7); the two upper connecting plates (7) are fixed to the two sides of the upper clamp block (4) by the upper connecting plate bolts (8); the upper clamp block (4) and the wedge clamp block (5) are engaged by the inclined plane. The inner side of the wedge-shaped clamping block (5) is attached to the reinforcing plate (9); the reinforcing plate (9) is fixed to both sides of the clamping section of the tenon simulation part (10) by adhesive; the clamping bolt (3) is screwed in from above the upper clamping block (4) to press the lower wedge-shaped clamping block (5); the surface of the tenon simulation part (10) is provided with a wear-resistant conductive coating, and it cooperates with the mortise simulation part (13) below. The outer side of the mortise simulation part (13) is positioned by cooperating with the opening groove of the lower clamping plate (14). The clamping plate (14) and the lower connecting plate (12) are connected at the opening above the slot by the lower connecting plate bolt (11); the lower clamping plate (14) is connected to the lower end clamp (16) by the external thread, and the other end of the lower end clamp (16) is connected to the fatigue testing machine by the cylindrical section; the lower clamping plate (14) is cooled by cooling water through the cooling water holes (15) on both sides of the bottom; when carrying out high temperature fatigue test, the turbine disk tenon joint structure is heated by electromagnetic induction coil; When heating with an inductor coil, the conductivity of the coating can heat the tenon simulation part (10) through heat conduction, so that the tenon simulation part (10) of the composite material is heated evenly. The friction clamping of the tenon simulation piece (10) is ensured by the two upper clamping bolts (3) to prevent the specimen from slipping; the upper clamping block (4) and the wedge clamping block (5) form a clamping force on the inner side of the wedge clamping block (5) when loaded through the inclined surface. The inner side of the wedge clamping block (5) acts on the reinforcing plates (9) on both sides of the clamping section of the tenon simulation piece (10). The surface of the reinforcing plates (9) is knurled to increase the friction force; the upper connecting plates (7) on both sides control the upper clamping block (4), the wedge clamping block (5) and the tenon simulation piece (10) to prevent lateral displacement; the two clamping bolts (3) at the upper end of the upper clamping block (4) are screwed down axially and contact the wedge clamping block (5), that is, the lateral clamping force of the wedge clamping block (5) on the tenon simulation piece (10) is increased when the fixture is assembled, so as to avoid the phenomenon of specimen slippage.

2. The fatigue testing fixture for a ceramic matrix composite turbine blade disk tenon joint structure according to claim 1, characterized in that: The maximum temperature is 1100℃ and the maximum load is 100kN; the tenon simulation part (10) is made of one of SiC / SiC, SiO2 / SiC, or Al2O3 / SiC ceramic matrix composite materials, and the tenon simulation part (13) is made of one of GH4169, GH4720Li high-temperature alloys or TC4, TC11 titanium alloys.

3. The fatigue testing fixture for a ceramic matrix composite turbine blade disk tenon joint structure according to claim 1, characterized in that: The load transmission route on the upper side of the fatigue test fixture is as follows: the upper clamp (1) transmits the load to the upper clamping plate (2) through the thread, and the thread is subjected to axial force; the upper clamping plate (2) transmits the load to the upper connecting plate (7), and the upper connecting plate (7) transmits the load to the upper clamping block (4), and the thread is subjected to shear force; the upper clamping block (4) transmits the load to the wedge-shaped clamping block (5) through the inclined surface, and the wedge-shaped clamping block (5) transmits the load to the tenon simulation part (10) through friction.

4. The fatigue testing fixture for a ceramic matrix composite turbine blade disk tenon joint structure according to claim 1, characterized in that: The lower clamping plate (14) and the lower connecting plate (12) can withstand a high temperature of up to 1100℃, thus simulating the load conditions of the real working conditions of the ceramic-based turbine disk tenon joint structure.

5. The fatigue testing fixture for a ceramic matrix composite turbine blade disk tenon joint structure according to claim 1, characterized in that: The lower clamping plate (14) has two cooling water holes (15) on both sides of its bottom. Cooling water is allowed to flow through the lower clamping plate (14) through an external water pipe to cool the fixture and reduce the operating temperature of the lower clamping plate (14).

6. The fatigue testing fixture for a ceramic matrix composite turbine blade disk tenon joint structure according to claim 1, characterized in that: After the tenon simulation part (10) is processed, the wear-resistant conductive coating is plated on its surface; the coating consists of a lubricating layer and a wear-resistant layer, the lubricating layer consists of one or more of gold, silver and borosilicates and their compounds; the wear-resistant layer consists of one or more of nickel, cobalt, platinum and rhodium and their oxides; the coating is attached to the surface of the composite tenon simulation part (10) by electroplating, sputtering, physical or chemical vapor deposition.

7. The fatigue testing fixture for a ceramic matrix composite turbine blade disk tenon joint structure according to claim 1, characterized in that: The lower clamping plate (14) has an open slot to prevent the tenon simulation part (13) from deforming excessively and causing the tenon simulation part (10) to come out of it, and it also facilitates the assembly of the clamp.

8. The test method for the fatigue test fixture of the ceramic matrix composite turbine disk tenon joint structure according to any one of claims 1-7, characterized in that, Includes the following steps: Step 1: Fatigue test fixture assembly: First, use adhesive to attach the reinforcing plate (9) to both sides of the clamping section of the tenon simulation part (10); connect the upper clamp (1) to the upper clamp plate (2) via threads; properly align the upper clamping block (4) and the wedge clamping block (5), with the inner side of the wedge clamping block (5) clamping the reinforcing plate (9), then screw in the clamping bolt (3) on the upper side of the upper clamp plate (2) to press the wedge clamping block (5); use the upper connecting plate bolt (8) to ensure that the upper connecting plate (7) and the upper clamping block (4) are concentric, and then use the upper clamping plate bolt (6) to connect the upper connecting plate (7) and the upper clamping plate (2); use the fatigue testing machine... Clamp the upper clamp (1) with the chuck; connect the tenon simulation part (10) and the mortise simulation part (13), connect the lower clamping plate (14) to the lower clamp (16), then insert the mortise simulation part (13) into the middle of the lower clamping plate (14), and fix the lower connecting plate (12) to both sides of the lower clamping plate (14) with the lower connecting plate bolt (11) to complete the assembly of the lower clamping plate. Then, put the inductor coil on the tenon joint and adjust its shape to make the tenon joint evenly heated for heating. Connect the outer cooling water at the cooling water hole (15); clamp the cylindrical section of the lower clamping plate (16) with the fatigue machine lower chuck to complete the assembly. Step 2: Set fatigue test loading conditions according to the actual working load of the ceramic matrix composite turbine disk tenon joint structure; select several measuring points at the test section of the tenon simulation part (10) and the mortise simulation part (13), and attach strain gauges and thermocouples; turn on the outer cooling water switch and check the water tightness of the passage; connect the inductor coil fitted at the tenon joint to the high frequency furnace for heating, set the temperature and adjust the relative position of the inductor coil and the test part, and ensure that the temperature field conforms to the working temperature field of the ceramic matrix composite turbine disk tenon joint structure by thermocouple reading; Step 3: After completing Step 2, conduct a ceramic matrix composite turbine disk tenon joint structure test. Set up a load controller to apply the corresponding load conditions using a fatigue testing machine. At the same time, set up a temperature controller to raise the temperature and correct it according to the actual temperature measured by thermocouples until the actual temperature of the test part reaches the target temperature. Through the coordinated control of the load controller and temperature controller, the mechanical load and temperature load are applied synchronously to the test part. When the test part reaches the specified number of cycles or fails, the test ends.

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