Ceramic matrix composite high-temperature bending mechanical property test tooling

Abstract

A kind of high-temperature bending mechanical property test tool of ceramic matrix composite, wherein the lower head adopts modular design, wherein the structure design of lower head support roller support and span adjustment block realizes adjustable span of test device, while ensuring controllable sample placement centering, ensuring test accuracy;The upper and lower press heads and the upper and lower connecting rods are designed using materials suitable for high temperature to ensure that the strength does not decrease and does not deform in a high-temperature test environment;The upper and lower press heads are designed separately in a modular manner and can be connected through a certain structure, which not only ensures the accuracy of the test, but also facilitates the replacement of press head parts during maintenance, saving costs.

Description

Technical Field

[0001] This invention relates to the field of materials engineering experiments, specifically to a testing fixture for the high-temperature bending mechanical properties of ceramic matrix composites, which can be used in a high-temperature vacuum environment. Background Technology

[0002] Ceramic matrix composites, as a novel type of composite material, are compounds with ceramic materials as the matrix and ceramic fibers, whiskers, particles, etc., as reinforcements. These materials maintain good mechanical properties even at high temperatures and play an important role in defense industries such as aerospace and nuclear power. Therefore, it is necessary to conduct high-temperature bending mechanical property tests on various ceramic matrix composites at high temperatures (above 800℃) to obtain accurate mechanical property data, thereby guiding the structural design of ceramic matrix composites. High-temperature bending performance tests require fixing both ends of a plate-shaped workpiece and applying a set pressure load to its middle section.

[0003] Invention patent CN 106053250 B discloses "Apparatus and method for measuring the bending elastic modulus and fracture strain of materials at ultra-high temperature", which includes a load transfer structure, a deformation transfer structure and a deformation sensor. The load transfer structure includes an upper pressure head, a lower pressure head, a hot end pressure rod and a water-cooled protective sleeve. The lower pressure head has a through hole in its center, and a bent sample is placed on the lower pressure head. The upper pressure head is located above the center of the bent sample. The water-cooled protective sleeve is a hollow water-cooled I-shaped structure, including upper and lower crossbeams and a middle column, used to block the heat conducted by the hot-end pressure rod. The water-cooled protective sleeve has a through hole in its center, and the hot-end pressure rod has a through hole in its center. One end of the hot-end pressure rod is connected to the upper end of the water-cooled protective sleeve, so that the hot-end pressure rod communicates with the through hole of the water-cooled protective sleeve. The other end of the hot-end pressure rod is connected to the bottom surface of the lower pressure head, so that the through hole of the hot-end pressure rod communicates with the through hole of the lower pressure head. The upper pressure head, lower pressure head, and hot-end pressure rod are made of materials that can withstand ultra-high temperatures above 1500℃. The materials can be one or more of graphite, ceramic, or refractory metals.

[0004] The existing technology employs an overly simplistic structure, failing to consider the potential for high-temperature testing, such as chuck loosening, deformation, or even damage. Such conditions lead to test failure and unreliable results. Furthermore, replacement requires replacing the entire device, resulting in high costs. The existing technology also suffers from a simple clamping structure, neglecting to account for abnormal sample loading caused by misalignment of the upper and lower loading mechanisms, thus affecting test accuracy. Additionally, the high-temperature alloy clamps are limited to temperatures below 800 degrees Celsius; while high-temperature graphite clamps are inherently weak, fragile, and lack rigidity, unsuitable for testing high-strength ceramic matrix composites. Moreover, graphite clamps are highly susceptible to oxidation and burn-out, requiring extremely high sealing during testing. Any leaks can lead to instantaneous damage and significantly increase operating costs.

[0005] Therefore, how to improve the experimental equipment, avoid the deformation and damage of the clamps under high temperature conditions, improve the convenience of equipment replacement, and adjust the span of the experimental device to adapt to samples of various lengths have become urgent technical problems to be solved. Summary of the Invention

[0006] The purpose of this invention is to provide a high-temperature bending mechanical property testing fixture for ceramic matrix composites. The components of the upper and lower pressure heads are made of various high-temperature resistant materials. The structural design of the lower pressure head support roller and the span adjustment block enables the span of the testing device to be adjustable, while ensuring that the sample placement is centered and controllable, thus guaranteeing the testing accuracy.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] A high-temperature bending mechanical property testing fixture for ceramic matrix composites includes an upper fixture, a lower fixture, and a sample located between the upper fixture and the lower fixture.

[0009] The upper clamping fixture, from top to bottom, includes an upper connecting seat, an upper connecting rod, and an upper pressure head.

[0010] The lower part of the upper connecting seat is fixedly connected to the upper connecting rod.

[0011] The upper connecting rod is connected to the upper connecting seat and the upper pressure head respectively;

[0012] The upper pressure head is connected to the upper connecting rod at its upper part and has a pressure head contact sample part at its lower part, wherein the pressure head contact sample part is designed with a cylindrical surface.

[0013] The lower fixture, from top to bottom, includes a lower pressure head, a lower connecting rod, and a lower connecting seat.

[0014] The top of the pressure head has two adjustable pressure support rollers, the two ends of the sample are supported by the pressure support rollers, and the lower part of the pressure head is fixedly connected to the lower connecting rod.

[0015] The lower connecting rod is fixedly connected to the lower pressure head and the lower connecting seat respectively;

[0016] The lower connecting seat mates with the lower connecting rod for connection.

[0017] The sample is supported by two downward support rollers of the lower pressure head, and the length direction of the sample is perpendicular to the extension direction of the part of the upper pressure head that contacts the sample.

[0018] The deformation measuring rod is placed at the center of the lower fixture and contacts the back of the sample. Its rear end extends out through the center hole of the lower fixture to the outside of the test fixture and connects to the displacement measuring mechanism.

[0019] Optionally, the upper connecting seat has a threaded hole inside, and the top of the upper connecting rod has a bolt mounting hole. The upper part of the upper connecting rod is embedded in the upper connecting seat and is fixedly connected to the upper connecting seat by an upper connecting rod fixing screw passing through the bolt mounting hole of the upper connecting rod.

[0020] Optionally, the upper pressure head has a pin connection hole, and the upper connecting rod has a circular pin mounting hole. The upper pressure head is inserted into the upper connecting rod, and the upper pressure head fixing pin fixes the upper connecting rod and the upper pressure head.

[0021] Optionally, the pressing head includes a pressing head base, multiple span adjustment blocks, two pressing support roller support seats, and two pressing support rollers.

[0022] Two pressure support roller support seats are symmetrically placed on the pressure head base. The upper part of the support roller support seat has a cylindrical groove to accommodate the pressure support roller. The bottom part has a groove that engages with the boss structure of the pressure head base to form a slide rail structure. The upper two sides of the pressure support roller support seat have protrusions to place the sample piece in the middle of the protrusions.

[0023] The two downward support rollers have a cylindrical structure and are symmetrically placed in the corresponding grooves of the downward support roller support seat;

[0024] The three span adjustment blocks have a lower groove structure that engages with the boss structure of the lower pressure head base to form a slide rail structure.

[0025] The upper part of the pressure head base is designed with a guide rail boss structure for placing multiple pressure support roller support seats and span adjustment blocks at intervals. It has a hole at the center for placing the deformation measuring rod for testing deformation. The bottom is a cylindrical structure that is installed in conjunction with the lower connecting rod.

[0026] Optionally, the lower pressure head base has a cylindrical structure at the bottom and a circular fixing groove around its outer perimeter. The lower pressure head base is inserted into the circular stepped structure at the top of the lower connecting rod, and multiple lower pressure head base fixing screws are screwed into the fixing groove of the lower pressure head base from the outside of the lower connecting rod through through holes.

[0027] Optionally, the upper inner side of the lower connecting seat has a circular mounting part, and the outer periphery of the circular step portion at the lower part of the lower connecting rod has a circular fixing groove. Multiple lower base fixing screws are screwed into the fixing groove of the circular step portion at the lower part of the lower connecting rod from the outside of the lower connecting seat through the through hole to fix the lower connecting seat and the lower connecting rod.

[0028] Optionally, the top of the upper connecting seat and the lower part of the lower connecting seat have threaded structures to connect the fixture to the loading mechanism of the testing machine, respectively.

[0029] Optionally, each component in the lower fixture has a through hole at its center to accommodate the deformation measuring rod, the tip of which is a ball head and contacts the center point of the sample.

[0030] Optionally, the upper pressure head and the lower pressure head are made of high-temperature ceramic material, and the upper connecting rod and the lower connecting rod are made of high-temperature ceramic matrix composite material or high-temperature multiphase alloy material.

[0031] The present invention has the following advantages:

[0032] 1. The upper and lower pressure heads are designed with high-temperature ceramic materials, which can maintain strength and not deform under test environment of 800 to 1800 degrees Celsius. This solves the problems of sharp strength drop and large thermal deformation of high-temperature alloys above 800 degrees Celsius, as well as the problems of low strength and brittleness of high-temperature graphite. The structure is simplified and reliable.

[0033] 2. The upper and lower pressure head connecting rods are designed with high-temperature ceramic composite materials and high-temperature molybdenum-lanthanum alloy, which can maintain strength and not deform under test environment of 800-1500 degrees Celsius. This solves the problems of sharp strength drop and large thermal deformation of high-temperature alloys above 800 degrees Celsius, as well as the problems of low strength and brittleness of high-temperature graphite. The structure is simplified and reliable.

[0034] 3. Modular design of multiple lower pressure head support roller supports and span adjustment blocks on the lower pressure head base to achieve adjustable span of the test device, while ensuring controllable centering of the sample placement, ensuring test accuracy, and facilitating timely replacement when sample components are damaged.

[0035] 4. The upper and lower pressure heads are designed to be separate and can be connected by a certain structure, which not only ensures the accuracy of the test, but also makes it easy to replace only the pressure head parts during maintenance, thus saving costs. Attached Figure Description

[0036] Figure 1 This is a view of a specimen used in a specific embodiment of the present invention;

[0037] Figure 2 This is a front view of the test fixture according to a specific embodiment of the present invention;

[0038] Figure 3 This is a cross-sectional view of the test fixture according to a specific embodiment of the present invention;

[0039] Figure 4 This is a perspective view of the test fixture according to a specific embodiment of the present invention;

[0040] Figure 5 This is an exploded view of the upper clamping fixture according to a specific embodiment of the present invention;

[0041] Figure 6This is a cross-sectional view of the upper clamping fixture according to a specific embodiment of the present invention;

[0042] Figure 7 This is a perspective view of the upper pressure head according to a specific embodiment of the present invention;

[0043] Figure 8 This is a cross-sectional view of the upper connecting rod according to a specific embodiment of the present invention;

[0044] Figure 9 This is a perspective view of the upper connecting seat according to a specific embodiment of the present invention;

[0045] Figure 10 This is a cross-sectional view of the upper connecting seat according to a specific embodiment of the present invention;

[0046] Figure 11 This is a cross-sectional view of the upper pressure head connecting pin according to a specific embodiment of the present invention;

[0047] Figure 12 This is a cross-sectional view of the upper connecting rod fixing screw according to a specific embodiment of the present invention;

[0048] Figure 13 This is a cross-sectional view of the lower clamping fixture according to a specific embodiment of the present invention;

[0049] Figure 14 This is a perspective view of the lower clamping fixture according to a specific embodiment of the present invention;

[0050] Figure 15 This is an exploded view of the pressure head according to a specific embodiment of the present invention;

[0051] Figure 16 This is a cross-sectional view of the pressure head base according to a specific embodiment of the present invention;

[0052] Figure 17 This is another cross-sectional view of the lower clamping fixture according to a specific embodiment of the present invention;

[0053] Figure 18 This is an exploded view of the lower fixture tooling according to a specific embodiment of the present invention;

[0054] Figure 19 This is a schematic diagram of a measuring push rod according to a specific embodiment of the present invention.

[0055] The technical features referred to by the reference numerals in the figure are as follows:

[0056] 11. Upper connecting seat; 12. Upper connecting rod; 13. Upper pressure head; 14. Upper connecting rod fixing screw; 15. Upper pressure head fixing pin; 2. Sample piece; 21. Lower connecting seat; 22. Lower connecting rod; 23. Lower pressure head; 24. Lower pressure head base; 25. Span adjustment block; 26. Lower pressure support roller support; 27. Lower pressure support roller support seat; 28. Lower pressure head base fixing screw; 29. ​​Lower base fixing screw; 3. Sample piece; 4. Deformation measuring rod. Detailed Implementation

[0057] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0058] The main features of this invention are: the lower pressure head adopts a modular design, wherein the structural design of the lower pressure head support roller base and the span adjustment block enables the span of the test device to be adjustable, while ensuring controllable centering of the sample and guaranteeing test accuracy; the upper and lower pressure heads and the upper and lower connecting rods are made of materials suitable for high temperatures, ensuring that the strength does not decrease and the deformation does not occur under high temperature test conditions; the upper and lower pressure heads adopt a modular and separate design, and can be connected by a certain structure, which not only ensures the accuracy of the test, but also facilitates maintenance by only replacing the pressure head parts, thus saving costs.

[0059] A test method for the mechanical properties of flexural strength of ceramic matrix composites in a high-temperature vacuum environment, based on the national standard Test Method for High-Temperature Bending Strength of Fine Ceramics (Standard No.: GB / T14390-2008), designs the test specimen as follows: Figure 1 As shown, the specific requirements are as follows:

[0060] 1) Traditional high-temperature material bending performance testing uses cylindrical or rectangular strip specimens. However, cylindrical specimens for ceramic matrix composites are difficult to prepare. Therefore, in this invention, a rectangular flat plate specimen is designed with a thickness of b = 3-6 mm, a total length of L = 50-70 mm and a width of H = 6-8 mm, depending on the specific specimen design.

[0061] 2) The two ends of the specimen are support sections, and the distance between the two support points is the test span. The span can be adjusted according to the specimen size to ensure that the test span is greater than 8 to 10 times the specimen thickness.

[0062] 3) The specific design dimensions for each part of the failure are determined through simulation calculation and analysis to ensure that the specimen fails in the test section during the test.

[0063] For details, see Figures 2-18 The structure and installation process of the high-temperature bending mechanical property testing fixture for ceramic matrix composite materials of the present invention will be described separately.

[0064] See Figures 2-4 The high-temperature bending mechanical property testing fixture for ceramic matrix composites includes an upper fixture, a lower fixture, and a sample 3 located between the upper fixture and the lower fixture.

[0065] The upper clamping fixture includes, from top to bottom, an upper connecting seat 11, an upper connecting rod 12, and an upper pressure head 13. In the high-temperature test, the entire upper pressure head 13 and most of the upper connecting rod 12 are located in the high-temperature zone inside the high-temperature environment chamber, while the upper connecting seat 11, the mounting base of the upper connecting rod 12, is located outside the high-temperature environment chamber and is only affected by thermal radiation temperature.

[0066] Among them, see Figure 10 The lower part of the upper connecting seat 11 is fixedly connected to the upper connecting rod 12, and the top end has a threaded structure to connect the clamp to the loading mechanism of the testing machine.

[0067] The upper connecting rod 12 is connected to the upper connecting seat 11 and the upper pressure head 13 respectively;

[0068] See Figure 7 The upper pressure head 13 is connected to the upper connecting rod 12 at its upper part and has a pressure head contact part at its lower part. The pressure head contact part adopts a cylindrical surface design to achieve linear contact of the pressure point during the test, thereby improving the test accuracy. At the same time, the cylindrical surface structure is conducive to the normal transmission of load and avoids load deflection.

[0069] In an optional embodiment, the upper connecting seat 11 has a threaded hole inside, and the top of the upper connecting rod 12 has a bolt mounting hole. The upper part of the upper connecting rod 12 is embedded in the upper connecting seat 11 and is fixedly connected to the upper connecting seat 11 by an upper connecting rod fixing screw 14 passing through the bolt mounting hole of the upper connecting rod 12.

[0070] In another optional embodiment, the upper pressure head 13 has a pin connection hole, the upper connecting rod 12 has a circular pin mounting hole, the upper pressure head 13 is inserted into the upper connecting rod 12, and the upper pressure head fixing pin 15 fixes the upper connecting rod 12 and the upper pressure head 13, and the pressure load is transmitted through end face contact.

[0071] In the upper fixture, the upper pressure head 13 is made of high-temperature resistant, high-strength, and high-hardness ceramic material, such as hot-pressed sintered SiC ceramic material or SiC / Si3N4 composite ceramic; the upper connecting rod 12 is made of high-temperature ceramic composite material or high-temperature multiphase alloy material, such as C / SiC ceramic composite material or high-temperature molybdenum-lanthanum alloy; the upper connecting seat 11 and the upper pressure head fixing screw 14 are made of high-temperature alloy material, such as nickel-based high-temperature alloy GH4169; the upper pressure head fixing pin 15 is made of high-temperature ceramic composite material or high-temperature multiphase alloy material, such as C / SiC ceramic composite material or high-temperature molybdenum-lanthanum alloy.

[0072] See Figure 13 , 14 The lower fixture tooling includes, from top to bottom, a lower pressure head 23, a lower connecting rod 22, and a lower connecting seat 21. In the high-temperature test, the entire lower pressure head 23 and most of the lower connecting rod 22 are in the high-temperature zone inside the high-temperature environment chamber, while the mounting base of the lower connecting rod 22, the lower connecting seat 21, is outside the high-temperature environment chamber and is only affected by thermal radiation temperature.

[0073] The top of the pressing head 23 has two adjustable pressing support rollers 27. Both ends of the sample 3 are supported by the pressing support rollers 27. The lower part of the pressing head is fixedly connected to the lower connecting rod 22.

[0074] The lower connecting rod 22 is fixedly connected to the lower pressure head 23 and the lower connecting seat 21 respectively;

[0075] The lower connecting seat 21 is connected to the lower connecting rod 22. The lower part has a threaded structure, and the fixture is connected to the loading mechanism of the testing machine through the threaded structure.

[0076] The sample 3 is supported by two downward support rollers 27 of the lower pressure head, and the length direction of the sample 3 is perpendicular to the extension direction of the pressure head of the upper pressure head 13 in contact with the sample, thereby applying a destructive force to the test section of the sample 13.

[0077] The deformation measuring rod 4 is placed at the center of the lower fixture and contacts the back of the sample 3. Its rear end is led out through the center hole of the lower fixture to the outside of the test fixture and connected to the displacement measuring mechanism.

[0078] The lower fixture has through holes in the center of each component to accommodate the deformation measuring rod 4. The tip of the deformation measuring rod 4 is a ball head design and contacts the center point of the sample 3 (i.e., the back side of the contact position corresponding to the upper pressure head), which is beneficial to the measurement accuracy.

[0079] Specifically, the pressing head 23 includes a pressing head base 24, multiple span adjustment blocks 25, two pressing support roller support seats 26, and two pressing support rollers 27.

[0080] Two of the downward support rollers 27 are cylindrical and made of high-temperature, high-strength ceramic material to ensure that their strength does not decrease or deform at 1500 degrees Celsius. The two downward support rollers 27 are symmetrically placed in the corresponding grooves of the downward support roller support seat. Their cylindrical surfaces ensure ideal line contact with the sample and facilitate precise control of the test span. At the same time, they ensure that the supporting load is in the normal direction of the sample surface.

[0081] Two pressure support roller support seats 26 are made of high-temperature high-strength ceramic material or high-temperature ceramic matrix composite material to ensure that the strength does not decrease or deform at 1500 degrees Celsius. The two are symmetrically placed on the pressure head base. The upper part of the support roller has a cylindrical groove to accommodate the pressure support roller 27 and precisely control its position. The bottom has a groove that cooperates with the boss structure of the pressure head base 24 to form a slide rail structure, ensuring that the position of the pressure support roller support seat is accurately aligned and avoiding sample placement deviation. The upper two sides of the pressure support roller support seat 26 have protrusions to place the sample 3 in the middle of the protrusions, constraining the placement of the sample and preventing the sample from slipping during the experiment.

[0082] Multiple span adjustment blocks 25, made of high-temperature graphite material, include three parts. By controlling the size of the parts, their symmetrical placement on the lower pressure head base is ensured. The groove structure at the bottom of the block engages with the boss structure of the lower pressure head base 24 to form a slide rail structure, ensuring precise centering of the part. The use of high-temperature graphite material ensures that the material does not deform or lose strength in a vacuum environment of 1500-2000 degrees Celsius. It is also easy to process, and the position of the lower pressure support roller support seat can be precisely controlled by processing its width, thereby realizing the adjustment and control of the test span.

[0083] The lower pressure head base 24 is made of high-temperature ceramic matrix composite material or high-temperature molybdenum-lanthanum alloy material. Its upper part is designed with a guide rail boss structure for placing the lower pressure support roller support seat 26 and the span adjustment block 25 at intervals. It has an opening at the center for placing the deformation measuring rod 4 for testing deformation. Its lower part is a cylindrical structure that is installed in conjunction with the lower connecting rod.

[0084] The lower connecting rod 22 is designed to be made of high-temperature resistant, high-strength high-temperature ceramic composite material and high-temperature multiphase alloy material, such as C / SiC ceramic composite material or high-temperature molybdenum-lanthanum alloy. Its upper and lower parts are circular stepped structures to cooperate with the lower pressure head base 24 and the lower connecting seat 21, respectively.

[0085] Specifically, the lower pressure head base 24 has a cylindrical structure at the bottom and a circular fixing groove around its outer perimeter. The lower pressure head base 24 is inserted into the circular stepped structure at the top of the lower connecting rod 22. Multiple lower pressure head base fixing screws 28 are screwed into the fixing groove of the lower pressure head base from the outside of the lower connecting rod 22 through through holes, and the pressure load is transmitted through end face contact.

[0086] The lower connecting seat 21 has a circular mounting part on the upper inner side, and the lower connecting rod 22 has a circular fixing groove around the outer periphery of the circular step part. Multiple lower base fixing screws 29 are screwed into the fixing groove of the circular step part of the lower connecting rod 22 from the outside of the lower connecting seat 21 through the through hole to fix the lower connecting seat 21 and the lower connecting rod 22.

[0087] In this invention, the lower pressure head base and the lower connecting seat adopt a circular fixing groove, and the fixing screws or pins can be screwed into the fixing groove, which reduces the difficulty of fixing the two to the lower connecting rod.

[0088] Both the lower pressure head base fixing screw 28 and the lower base fixing screw 29 can be made of high-temperature alloy metal.

[0089] The following describes how to install the test fixture of the present invention and conduct tests.

[0090] (1) Installation of upper clamp

[0091] According to the design, the upper fixture, namely the upper pressure head and the upper connecting rod, is assembled and connected to the loading mechanism of the testing machine. During installation, ensure that the position of the upper pressure head is aligned with the center of the loading mechanism, and that the entire fixture is perpendicular to the loading plane.

[0092] (2) Installation of the lower clamp

[0093] 1) Assemble most of the lower fixture, namely the lower pressure head base and the lower connecting rod, according to the design, and connect them to the loading mechanism of the testing machine. During installation, ensure that the center of the lower pressure head is aligned with the center of the loading mechanism, and that the entire fixture is perpendicular to the loading plane; ensure that the displacement push rod is centered and perpendicular to the loading plane.

[0094] 2) Process the span adjustment block according to the design, and install it together with the lower pressure roller support seat and the lower pressure support roller on the corresponding position on the lower pressure head base, and make sure that the lower pressure roller support seat and the lower pressure support roller are placed symmetrically on both sides.

[0095] (3) Sample installation

[0096] 1) Place the sample on the lower pressure head support roller. Ensure that its position is centered;

[0097] 2) Control the upper pressure head to move slowly, ensuring that it makes slight contact with the middle position of the sample;

[0098] 3) Control the deformation measuring rod to make slight contact with the lower surface of the sample, and align it with the contact point of the upper indenter;

[0099] 4) Install the high-temperature environment chamber, heat it to the specified temperature, and then begin the test.

[0100] The present invention has the following advantages:

[0101] 1. The upper and lower pressure heads are designed with high-temperature ceramic materials, which can maintain strength and not deform under test environment of 800 to 1800 degrees Celsius. This solves the problems of sharp strength drop and large thermal deformation of high-temperature alloys above 800 degrees Celsius, as well as the problems of low strength and brittleness of high-temperature graphite. The structure is simplified and reliable.

[0102] 2. The upper and lower pressure head connecting rods are designed with high-temperature ceramic composite materials and high-temperature molybdenum-lanthanum alloy, which can maintain strength and not deform under test environment of 800-1500 degrees Celsius. This solves the problems of sharp strength drop and large thermal deformation of high-temperature alloys above 800 degrees Celsius, as well as the problems of low strength and brittleness of high-temperature graphite. The structure is simplified and reliable.

[0103] 3. Modular design of multiple lower pressure head support roller supports and span adjustment blocks on the lower pressure head base to achieve adjustable span of the test device, while ensuring controllable centering of the sample placement, ensuring test accuracy, and facilitating timely replacement when sample components are damaged.

[0104] 4. The upper and lower pressure heads are designed to be separate and can be connected by a certain structure, which not only ensures the accuracy of the test, but also makes it easy to replace only the pressure head parts during maintenance, thus saving costs.

[0105] The above description is a further detailed explanation of the present invention in conjunction with specific preferred embodiments. It should not be considered that the specific embodiments of the present invention are limited to this. For those skilled in the art, several simple deductions or substitutions can be made without departing from the concept of the present invention, and all such deductions or substitutions should be considered to fall within the scope of protection of the present invention as defined by the submitted claims.

Claims

1. A testing fixture for the high-temperature bending mechanical properties of ceramic matrix composites, characterized in that: It includes an upper fixture, a lower fixture, and a sample piece located between the upper fixture and the lower fixture; The upper clamping fixture, from top to bottom, includes an upper connecting seat, an upper connecting rod, and an upper pressure head. The lower part of the upper connecting seat is fixedly connected to the upper connecting rod. The upper connecting rod is connected to the upper connecting seat and the upper pressure head respectively; The upper pressure head is connected to the upper connecting rod at its upper part and has a pressure head contact sample part at its lower part, wherein the pressure head contact sample part is designed with a cylindrical surface. The lower fixture, from top to bottom, includes a lower pressure head, a lower connecting rod, and a lower connecting seat. The top of the pressure head has two adjustable pressure support rollers, the two ends of the sample are supported by the pressure support rollers, and the lower part of the pressure head is fixedly connected to the lower connecting rod. The lower connecting rod is fixedly connected to the lower pressure head and the lower connecting seat respectively; The lower connecting seat mates with the lower connecting rod for connection. The sample is supported by two downward support rollers of the lower pressure head, and the length direction of the sample is perpendicular to the extension direction of the part of the upper pressure head that contacts the sample. The deformation measuring rod is placed at the center of the lower fixture and contacts the back of the sample. Its rear end is led out through the center hole of the lower fixture to the outside of the test fixture and connected to the displacement measuring mechanism. The pressing head includes a pressing head base, multiple span adjustment blocks, two pressing support roller support seats, and two pressing support rollers; Two pressure support roller support seats are symmetrically placed on the pressure head base. The upper part of the support roller support seat has a cylindrical groove to accommodate the pressure support roller. The bottom part has a groove that engages with the boss structure of the pressure head base to form a slide rail structure. The upper two sides of the pressure support roller support seat have protrusions to place the sample piece in the middle of the protrusions. The two downward support rollers have a cylindrical structure and are symmetrically placed in the corresponding grooves of the downward support roller support seat; The three span adjustment blocks have a lower groove structure that engages with the boss structure of the lower pressure head base to form a slide rail structure. The upper part of the pressure head base has a guide rail boss structure for placing multiple pressure support roller support seats and span adjustment blocks at intervals. It has a hole at the center for placing the deformation measuring rod for testing deformation. The bottom part is a cylindrical structure that is installed in conjunction with the lower connecting rod.

2. The mechanical property testing fixture according to claim 1, characterized in that: The upper connecting seat has a threaded hole inside, and the top of the upper connecting rod has a bolt mounting hole. The upper part of the upper connecting rod is embedded in the upper connecting seat and is fixedly connected to the upper connecting seat by an upper connecting rod fixing screw passing through the bolt mounting hole of the upper connecting rod.

3. The mechanical property testing fixture according to claim 2, characterized in that: The upper pressure head has a pin connection hole, and the upper connecting rod has a circular pin mounting hole. The upper pressure head is installed into the upper connecting rod, and the upper pressure head fixing pin fixes the upper connecting rod and the upper pressure head.

4. The mechanical property testing fixture according to claim 1, characterized in that: The lower pressure head base has a cylindrical structure at the bottom and a circular fixing groove around its outer circumference. The lower pressure head base is inserted into the circular stepped structure at the top of the lower connecting rod. Multiple lower pressure head base fixing screws are screwed into the fixing groove of the lower pressure head base from the outside of the lower connecting rod through through holes.

5. The mechanical property testing fixture according to claim 4, characterized in that: The lower connecting seat has a circular mounting part on the upper inner side, and the outer periphery of the circular step part at the bottom of the lower connecting rod has a circular fixing groove. Multiple lower base fixing screws are screwed into the fixing groove of the circular step part at the bottom of the lower connecting rod from the outside of the lower connecting seat through the through hole to fix the lower connecting seat and the lower connecting rod.

6. The mechanical property testing fixture according to claim 1, characterized in that: The top of the upper connecting seat and the lower part of the lower connecting seat have threaded structures to connect the fixture tooling to the loading mechanism of the testing machine, respectively.

7. The mechanical property testing fixture according to claim 1, characterized in that: The lower fixture has through holes at the center of each component to accommodate the deformation measuring rod, the tip of which is a ball head and contacts the center point of the sample.

8. The mechanical property testing fixture according to claim 1, characterized in that: The upper pressure head and the lower pressure head are made of high-temperature ceramic material, and the upper connecting rod and the lower connecting rod are made of high-temperature ceramic matrix composite material or high-temperature molybdenum-lanthanum alloy material.

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