CN115436161A - Tensile-tensile fatigue test fixture and test method for ceramic matrix composite joggle joint structure - Google Patents
Tensile-tensile fatigue test fixture and test method for ceramic matrix composite joggle joint structure Download PDFInfo
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- CN115436161A CN115436161A CN202211078122.3A CN202211078122A CN115436161A CN 115436161 A CN115436161 A CN 115436161A CN 202211078122 A CN202211078122 A CN 202211078122A CN 115436161 A CN115436161 A CN 115436161A
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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Abstract
The invention relates to a tensile-tensile fatigue test fixture and a test method for a ceramic matrix composite joggle structure, which can meet the static strength of the ceramic matrix composite turbine blade joggle structure under the conditions of high temperature and normal temperature and the loading requirements of various fatigue tests. The upper and lower segments of the clamp are connected with a fatigue testing machine by adopting a round bar-shaped clamp, and the upper and lower round bars are connected with other parts by threads. The upper part comprises an upper round bar, a U-shaped plate, a pin, a clamping plate bolt and a gasket; the lower side part consists of a transverse clamping piece, a longitudinal clamping piece, a transition section and a lower side round bar; the clamp can flexibly adapt to ceramic matrix composite tenon test pieces with different sizes, simultaneously avoids the problem of test failure caused by fracture of a clamping section caused by dovetail, pin or thread clamping, can be used for the test conditions of tensile load of a composite joggle part from room temperature to 1100 ℃ and from 0N to 100kN, and is particularly used for fatigue or static strength tests with higher requirements on the uniformity of a temperature field.
Description
Technical Field
The invention belongs to the field of mechanical property evaluation of a ceramic matrix composite joggle structure test, and particularly relates to a tensile-tensile fatigue test clamp and a test method for a ceramic matrix composite joggle structure.
Background
Ceramic matrix composites are considered a potential material of choice for the next generation of aviation gas turbine engine turbine blades due to their low density and high temperature resistance. The blade disc connecting part of the hot end component is in a working environment with high temperature, high pressure and high rotating speed, and simultaneously, the factors of ceramic matrix composite/high temperature alloy contact, abrasion and the like are superposed, so that the service environment of the joggle joint part of the blade disc connection is very severe, and fatigue failure is very easy to cause. Therefore, before the ceramic matrix composite is applied to engineering practice, a large number of simulation tests under real load conditions need to be carried out on the joggle joint structure in a laboratory environment, the strength and the fatigue performance of the joggle joint structure are explored, a reliable mechanical property evaluation method is developed, and a foundation is laid for the improvement of the performance of a new generation of aero-engine.
In a traditional metal high-temperature mechanical property test, clamping modes such as pins, dovetail grooves or threads are mostly adopted. However, for brittle anisotropic materials such as ceramic matrix composites, pin clamping requires pin holes in the clamping section of the test piece, and the holes can break fibers to cause damage; the dovetail-shaped clamping can cause the fiber deflection and the matrix enrichment area to appear at the clamping section of the test piece; the prior process for machining the threads by adopting the ceramic matrix composite material has certain problems. Therefore, the existing clamp is difficult to be applied to the high-temperature mechanical test of the ceramic matrix composite material. On the other hand, the structural size of the tenon needs to be changed in the exploratory test, which also puts requirements on the universality of the clamp; under the heavy load condition, the excessive deformation of tongue-and-groove can make the tenon test piece can appear drawing and take off, lead to experimental failure, consequently, for the appearance of the smooth of assurance test, avoiding above problem, the anchor clamps that need a ceramic matrix composite joggle structure at present draw-draw fatigue test promptly, can guarantee the steadiness at test piece centre gripping position, can promote the commonality of anchor clamps to the not unidimensional tenon simultaneously.
Aiming at the problems in the joggle structure test of the ceramic matrix composite material, the following obvious problems exist: (1) How to ensure the stability of the composite material test piece clamping which can not punch holes, can not change the section suddenly and can not process threads. (2) How to promote the commonality of anchor clamps to the tenon test piece of different sizes. (3) How to guarantee that the tenon test piece does not pull out under the condition of large load. After reviewing the existing patents and documents, no design of test fixture and test method capable of solving the above three core problems have been found. Therefore, there is a need to develop a clamp design and test method for tensile-tensile fatigue test of the joggle joint structure of ceramic matrix composite material to solve the above problems.
The Chinese invention patent CN201810570207.0 discloses a test device for testing the high-temperature strength of a ceramic matrix composite material tenon joint structure, the method also adopts a method of bolt pressing and friction clamping, but the clamp has more arc surfaces, large processing difficulty and high cost, and meanwhile, the whole set of clamp needs to be replaced aiming at tenon test pieces with different sizes, so that the test cost is further increased.
The Chinese invention patent CN202010271891.X discloses a clamp for testing the tensile strength of a composite material, which clamps the composite material in a pin hole mode, but the fiber breaking bearing capacity of a clamping section is reduced by punching the clamping section of the composite material, and the problem of test failure caused by the fact that a test piece is broken at the clamping section is very easy to occur in the test process.
The existing documents 'Kang Yongjiang, chen Yong. Analysis of stress between layers of a tenon of a fan blade made of a laminated composite material [ J ]. The report of aeronautics and dynamics, 2020,35 (02): 388-396.' show a testing device for the tenon test of the fan blade made of the laminated composite material, and the testing device also has the problem of punching of a tenon clamping section. The tenon pulling-out is prevented by enlarging the mortise, but the mortise is too large to exceed the size of the high-temperature furnace, so that the mortise is not suitable for high-temperature mechanical tests.
The prior document "Watanabe F, nakamura T, shinohara K.the application of ceramic matrix composite to low pressure turbine blade [ C ]// Turbo Expo: power for Land, sea, and air. American Society of Mechanical Engineers,2016,49828 V006T02A003" shows a fixture device for high temperature testing of a tenon made of ceramic matrix composite material, which uses bolts to connect the fixture and the test piece, but the broken fibers of the bolt holes of the clamping section of the test piece reduce the success rate of the test, and the design has no device for preventing the pull-off of the tenon.
In conclusion, the prior art lacks a clamp design method suitable for the tensile-tensile fatigue test of the ceramic matrix composite joggle joint structure, and the problems that the clamping section is easy to lose efficacy, the clamp universality is improved, the tenon is prevented from being pulled off and the like are pertinently treated, so that the problems are well solved.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides the tensile-tensile fatigue test fixture and the test method for the ceramic matrix composite joggle joint structure, which solve the problems of easy failure of a composite material clamping section, easy pulling-off of a large-load test tenon and the like caused by the existing design, improve the universality of the fixture and reduce the test cost. The invention can be used for the static strength and various fatigue tests of the ceramic matrix composite turbine blade joggle joint structure.
In order to achieve the purpose, the invention adopts the technical scheme that:
a tensile-tensile fatigue test fixture for a ceramic matrix composite joggle structure comprises an upper side round bar, a U-shaped plate, a clamping plate, a pin, a reinforcing sheet, a clamping plate bolt, a gasket, a tenon simulating piece, a transverse clamping piece, a longitudinal clamping piece, a mortise simulating piece, a transition section and a lower side round bar; a clamping block of the fatigue testing machine clamps the cylindrical section of the upper round rod, and one end of the external thread of the upper round rod is connected with the threaded hole of the U-shaped plate; the U-shaped plate and the clamping plate penetrate through the U-shaped plate and are positioned through two pins, the lower end of the clamping plate clamps the tenon simulation piece in a pressing mode through four clamping plate bolts, a gasket is arranged between the nut and the clamping plate at intervals, and metal reinforcing plates are adhered to two sides of a clamping section on the upper side of the tenon simulation piece; the lower end of the tenon simulation piece is matched with the mortise simulation piece, two transverse clamping pieces on the upper side of the mortise simulation piece are fixed in a lap joint mode, and two longitudinal clamping pieces on the upper side clamp the transverse clamping pieces to prevent the transverse clamping pieces from falling off; the external threads on the lower side of the mortise simulation part are connected with the internal threads on the upper side of the transition section, a cooling water hole is formed in the transition section, and the internal threads on the lower side of the transition section are connected with the external threads of the lower round rod; the cylindrical section of the lower round rod is clamped on a fatigue testing machine; when the high-temperature test is carried out, a high-temperature furnace is adopted for heating.
Further, the upper side of the mortise simulation piece is fixed by a transverse clamping piece and a longitudinal clamping piece; the two transverse clamping pieces are of U-shaped structures, and the end parts of the two transverse clamping pieces are used for fixing an opening above the mortise simulation piece in an annular mode in an overlapping mode, so that the tenon simulation piece is prevented from being pulled off due to excessive deformation of the mortise simulation piece in a large-load test, and the test is prevented from failing; two vertical clamping pieces are U-shaped structures, and are respectively arranged on two sides of the tenon simulation piece and used for clamping the transverse clamping piece from top to bottom so as to prevent the transverse clamping piece from falling off due to vibration in the test process.
Furthermore, the two sides of the mortise simulation piece and the transverse clamping pieces have inclination angles of 6-12 degrees; the tenon joint part is not blocked by fixing the transverse clamping piece and the longitudinal clamping piece, so that the tenon joint part can be observed conveniently in the test process.
Further, the shim is between the clamping plate and the nut for clamping the analogue piece of the tenon.
Further, the distance between the two clamping plates is freely adjusted according to the thickness of the clamping section of the tenon simulating piece.
Furthermore, the material of the tongue-and-groove simulation piece, the transverse clamping piece, the longitudinal clamping piece and the transition section is one of cast high-temperature alloy, single-crystal high-temperature alloy or powder high-temperature alloy, and the rest parts are made of stainless steel materials outside the high-temperature furnace.
Furthermore, a cooling water hole is formed in the lower side of the transition section, and cooling water flows through the clamp of the transition section through an external water pipe, so that the service temperature of the clamp is reduced.
Further, the load transmission route on the upper side of the fatigue test fixture is as follows: the upper round bar is transmitted to the U-shaped plate through threads, and the threads are stressed axially; the U-shaped plate is transmitted to the clamping plate through the pin, and the pin bears shearing force; the clamping plate is transmitted to the tenon simulating piece through friction force; force is transferred between the mortise simulation part and the transition section, between the transition section and the lower side round bar through threads, and the threads are all subjected to axial force.
The invention also provides a test method of the tensile-tensile fatigue test fixture of the ceramic matrix composite joggle joint structure, which comprises the following steps:
step 1: assembling a test fixture: firstly, adhering reinforcing sheets made of aluminum alloy to two sides of a clamping section above a tenon simulation piece by using an adhesive, and standing for a certain time; then, the tenon simulating piece is placed between the two clamping plates and is screwed down through the four clamping plate bolts, and a gasket is arranged between the nut and the clamping plate; connecting the U-shaped plate with the upper round rod through threads, positioning the U-shaped plate and the clamping plate through pins, assembling the clamp at the upper half part, and clamping the upper round rod in a chuck at the upper side of the fatigue testing machine; the mortise simulation piece is matched with the tenon simulation piece, the two transverse clamping pieces above the mortise simulation piece are used for locking the deformation of the mortise simulation piece in a lap joint mode, and a longitudinal clamping piece is respectively arranged above the transverse clamping piece and on two sides of the tenon simulation piece and vertically clamps the transverse clamping piece downwards; the internal threads on the upper part and the lower part of the transition section are respectively connected with the mortise simulation piece and the lower side round rod, the cylindrical section of the lower side round rod is connected with a lower end chuck of the fatigue testing machine, and the clamp is assembled;
step 2: setting test parameters according to the real working condition of the ceramic matrix composite joggle joint structure, setting a measuring point at the checking section of the joggle joint part, and laying a thermocouple; a fiber bragg grating sensor is arranged on the other side of the tenon joint structure, and the damage state of the tenon joint structure is monitored; opening a cooling water passage and checking the water tightness; placing the high-temperature furnace at the tenon joint structure, and applying a uniform temperature field;
and step 3: after the step 2 is finished, performing a strength or fatigue test on the joggle joint structure of the ceramic matrix composite material, ensuring that the temperature in the high-temperature furnace meets the test requirement through a temperature controller, and preserving the heat for one hour after the temperature displayed by the thermocouple reaches a set temperature, and starting the test; and applying corresponding load conditions through a load controller of the fatigue testing machine, and finishing the test when the tenon joint structure of the ceramic matrix composite material reaches the specified service life or fails.
Compared with the prior art, the invention has the beneficial effects that:
(1) The invention aims at the problem that the clamping section of the test piece is volatile and difficult to process due to the adoption of dovetail, pin and thread clamping in the traditional metal clamping method by adopting a friction clamping mode of clamping plate bolt pressing in a ceramic matrix composite joggle joint structure.
(2) The invention designs an innovative anti-pulling-off structure aiming at the ceramic matrix composite joggle joint structure, two transverse clamping pieces above the mortise simulation piece clamp the deformation of the mortise simulation piece through lapping, and the upper side of each transverse clamping piece and two sides of the tenon simulation piece are respectively provided with a longitudinal clamping piece for fixing the transverse clamping pieces. The deformation of the mortise simulation piece is controlled, and meanwhile, the size of the fixture is reduced as much as possible, and the fixture can be wrapped by the high-temperature furnace. On the other hand, the anti-pulling-off design can also leak out of the joggle joint part and can be observed through a quartz glass window of the high-temperature furnace.
(3) The design of the invention improves the universality of the clamp and can be flexibly suitable for tenon simulation pieces with different sizes. To the tenon simulation piece of equidimension not, the distance between two splint is adjustable, only need change not the tongue-and-groove simulation piece of equidimension can. Meanwhile, for a high-temperature test, only the transverse clamping piece, the longitudinal clamping piece, the mortise simulation piece and the transition section need to be subjected to high-temperature-resistant metal processing, and other parts can be made of stainless steel.
In conclusion, compared with the prior art, the invention provides a design and a test method of a tensile-tensile fatigue test fixture for the ceramic matrix composite joggle joint structure. The method overcomes the problem that the clamping section of the test piece is easy to lose efficacy or difficult to process when the traditional clamp with the metal joggle joint structure is applied to the ceramic matrix composite material, and simultaneously, an innovative anti-pulling-off structure is designed for the tenon of the composite material. Meanwhile, the stability, the universality and the cost control of the clamp are greatly improved compared with the prior art, and a solid test foundation is laid for the exploration of the strength and the fatigue performance of the joggle joint structure of the ceramic matrix composite material.
Drawings
FIG. 1 is a schematic view of a tensile-tensile fatigue test fixture for a joggle joint structure of a ceramic matrix composite according to the present invention;
FIG. 2 is an exploded view of a tensile-tensile fatigue test fixture for a ceramic matrix composite joggle structure according to the present invention;
FIG. 3 shows the inclination angles of the two sides of the mortise simulation piece of the fixture for the tensile-tensile fatigue test of the ceramic matrix composite joggle structure of the invention
A schematic diagram of (a);
FIG. 4 is a schematic view of the pull-out prevention device of the tensile-tensile fatigue test fixture of the ceramic matrix composite joggle structure of the present invention;
FIG. 5 is a schematic view of the position of a high temperature furnace of the tensile-tensile fatigue test fixture of the ceramic matrix composite joggle structure of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments, and all other embodiments obtained by a person skilled in the art based on the embodiments of the present invention belong to the protection scope of the present invention without creative efforts.
The invention provides a tensile-tensile fatigue test fixture and a test method for a ceramic matrix composite joggle joint structure. The embodiment of the invention adopts a tenon simulation piece manufactured by SiC/SiC and RMI processes and a mortise simulation piece manufactured by GH 4169; the test load is 17kN, the stress ratio of the low cycle fatigue test is 0.1, and the test temperature is 550 ℃.
The invention discloses a tensile-tensile fatigue test fixture for a ceramic matrix composite joggle structure, which comprises an upper side round bar 1, a U-shaped plate 2, a clamping plate 3, a pin 4, a reinforcing sheet 5, a clamping plate bolt 6, a gasket 7, a tenon simulation piece 8, a transverse clamping sheet 9, a longitudinal clamping sheet 10, a mortise simulation piece 11, a transition section 12 and a lower side round bar 13. A clamping block of the fatigue testing machine clamps the cylindrical section of the upper side round rod 1, and one end of the external thread of the upper side round rod 1 is connected with the threaded hole of the U-shaped plate 2; the U-shaped plate 2 and the clamping plate 3 are positioned by two pins 4, the lower end of the clamping plate 3 clamps a tenon simulation piece 8 in a pressing mode through four clamping plate bolts 6, a gasket 7 is arranged between the nut and the clamping plate 3 at an interval, and metal reinforcing pieces 5 are adhered to two sides of a clamping section on the upper side of the tenon simulation piece 8; the lower end of the tenon simulation part 8 is matched with the mortise simulation part 11, two transverse clamping pieces 9 on the upper side of the mortise simulation part 11 are fixed in a lap joint mode, and two longitudinal clamping pieces 10 on the upper side clamp the transverse clamping pieces 9 to prevent the transverse clamping pieces 9 from falling off; the external thread on the lower side of the mortise simulation piece 11 is connected with the internal thread on the upper side of the transition section 12, the transition section 12 is provided with a cooling water hole, and the internal thread on the lower side of the transition section 12 is connected with the external thread of the lower round rod 13; the cylindrical section of the lower round rod 13 is clamped on a fatigue testing machine. When the high-temperature test is carried out, a high-temperature furnace can be adopted for heating.
The upper side of the mortise simulation piece 11 is fixed by a transverse clamping piece 9 and a longitudinal clamping piece 10. The two transverse clamping pieces 9 are of U-shaped structures, and the end parts of the two transverse clamping pieces fix the upper opening of the mortise simulation piece 11 in an annular mode in a lap joint mode, so that the tenon simulation piece 8 is prevented from being pulled off due to excessive deformation of the mortise simulation piece 11 in a large-load test, and the test is prevented from failing; the two longitudinal clamping pieces 10 are of U-shaped structures, and are respectively arranged on two sides of the tenon simulating piece 8, and the transverse clamping pieces 9 are clamped from top to bottom, so that the transverse clamping pieces 9 are prevented from being vibrated and falling off in the test process.
The transverse clamping pieces 9 on both sides of the mortise simulating component 11 have inclination angles of 6-12 degrees. The purpose of the inclination of the tongue and groove simulator 11 is to facilitate the longitudinal positioning of the transverse jaw 9. Meanwhile, the tenon joint part is not blocked by fixing the transverse clamping piece 9 and the longitudinal clamping piece 10, so that the tenon joint part can be observed conveniently in the test process.
The gasket 7 is arranged between the clamping plate 3 and the nut used for the clamping tenon simulation piece 8, and is mainly used for preventing the nut from loosening in the test process, increasing the contact area and optimizing the clamping plate compression effect.
The invention can be applied to the test of the tenon simulating pieces 8 with different sizes. Two distance between splint 3 can freely be adjusted according to the thickness of 8 centre gripping sections of tenon analog piece, like this when developing the not unidimensional tenon analog piece 8 experiment, only need change tongue-and-groove analog piece 11 can, improved the commonality of this set of anchor clamps greatly.
The tongue-and-groove simulation piece 11, the transverse clamping piece 9, the longitudinal clamping piece 10 and the transition section 12 are made of one of cast high-temperature alloy, single crystal high-temperature alloy or powder high-temperature alloy and can bear the high temperature of 1100 ℃ at most, and the rest parts are arranged outside the high-temperature furnace and are made of stainless steel materials, so that the material and processing cost of the clamp are reduced.
The lower side of the transition section 12 is provided with a cooling water hole, and cooling water flows through the clamp of the transition section 12 through an external water pipe, so that the use temperature of the clamp is reduced, the service life of the transition section 12 is prolonged, and the total test cost is reduced.
The load transmission route at the upper side of the fatigue test fixture is that an upper round rod 1 is transmitted to a U-shaped plate 2 through threads, and the threads bear axial force; the U-shaped plate 2 is transmitted to the clamping plate 3 through the pin 4, and the pin 4 bears shearing force; the clamping plate 3 is transmitted to the tenon simulating part 8 by friction. The force is transmitted between the mortise simulation piece 11 and the transition section 12, and between the transition section 12 and the lower side round rod 13 through threads. The threads are all axially stressed. The force transmission route enables the fatigue testing machine to be far away from the heated joggle joint part, so that the experimental machine is protected; meanwhile, friction clamping can be realized on the tenon simulation part 8, and the test part clamping section is prevented from being damaged due to dovetail-shaped clamping, pin clamping or threaded clamping.
The test method of the invention comprises the following steps:
1. and (3) carrying out test piece processing, firstly designing a tenon simulation piece according to the size of the engine tenon, and determining the overall dimension of the tenon simulation piece according to the simulation piece design principle that the surface state is consistent and the damage parameters are consistent. Meanwhile, aiming at the overall dimension of the tenon simulation piece, a corresponding ceramic matrix composite material weaving method and a corresponding laying direction are designed. Aiming at the expansion of the cross section area of the tenon, the mode of filling the interlayer is adopted, the fiber volume fraction of the tenon part is ensured, and the main direction of the fiber is ensured to be consistent with the direction of the inclined plane of the shoulder of the tenon as much as possible.
2. Designing a tensile-tensile fatigue test fixture for the ceramic matrix composite material as shown in figure 1. The two sides of the mortise simulation part 11 have a certain inclination angle
As shown in fig. 3, the purpose of which is to facilitate the fixing of the lateral jaw 9. The inclination angles of the cross sections of the two transverse clamping pieces 9 on the upper side are consistent with the angle of the mortise simulation piece 11 and are fixed in a lap joint mode, and the upper side is provided with two longitudinal clamping piecesThe transverse clamping piece 9 is clamped to the clamping piece 10 to prevent falling off, as shown in figure 4; the cylindrical section of the lower round bar 13 is clamped on a fatigue testing machine, and the explosion diagram of the clamp is shown in figure 2. When a high-temperature test is carried out, a high-temperature furnace 14 can be adopted for heating, the assembly position of the high-temperature furnace is shown in figure 5, the upper edge of the high-temperature furnace 14 is lower than the lower edge of the clamping plate 3, the whole joggle joint structure, the transverse clamping pieces 9, the longitudinal clamping pieces 10 and the upper half part of the transition section 12 are filled into the high-temperature furnace 14, and the uniformity of a temperature field at the joggle joint structure in the test process is ensured. Meanwhile, the quartz glass window 15 of the high-temperature furnace 14 is opposite to the joggle joint part, so that an observation test is conveniently carried out.
3. Testing and mounting, namely firstly adopting an adhesive to stick the reinforcing sheet 5 made of aluminum alloy metal on two sides of the clamping section above the tenon simulating piece 8, standing for a certain time to ensure that the bonding effect is optimal, and processing knurling on the surface of the reinforcing sheet 5 to increase the friction force; then, the tenon simulating piece 8 is placed between the two clamping plates 3 and is screwed down through the four clamping plate bolts 6, and a gasket 7 is padded between the nut and the clamping plates 3; pass through threaded connection with U template 2 and upside pole 1, pass through pin 4 location with U template 2 and splint 3 again, the first half anchor clamps equipment is accomplished, presss from both sides upside pole 1 in fatigue testing machine upside chuck. The mortise simulation part 11 is matched with the tenon simulation part 8, the deformation of the mortise simulation part 11 is locked by the two transverse clamping pieces 9 above the mortise simulation part in a lap joint mode, and the longitudinal clamping pieces 10 are respectively arranged above the transverse clamping pieces 9 and at two sides of the tenon simulation part 8 and vertically clamp the transverse clamping pieces 9 downwards; internal threads above and below the transition section 12 are respectively connected with the mortise simulation part 11 and the lower side round rod 13, the cylindrical section of the lower side round rod 13 is connected with a lower end chuck of the fatigue testing machine, and the clamp is assembled.
4. And (3) experimental setting: and setting test parameters according to the real working condition of the ceramic matrix composite material joggle joint structure. Arranging a measuring point at the examination section of the joggle joint part, and pasting a thermocouple; and a fiber grating sensor is arranged and stuck on the other side of the tenon joint structure to monitor the damage state of the tenon joint structure. The cooling water passage was opened to check the water tightness. And (4) placing the high-temperature furnace at the tenon joint structure, and applying a uniform temperature field.
5. Carrying out tests: and (3) performing a strength or fatigue test on the joggle joint structure of the ceramic matrix composite material, ensuring that the temperature in the high-temperature furnace meets the test requirement through a temperature controller, and preserving the heat for one hour after the temperature displayed by the thermocouple reaches a set temperature, and starting the test. And applying corresponding load conditions through a load controller of the fatigue testing machine, and finishing the test when the tenon joint structure of the ceramic matrix composite material reaches the specified service life or fails.
The above examples are provided for the purpose of describing the present invention only and are not intended to limit the scope of the present invention. The scope of the invention is defined by the appended claims. Various equivalent substitutions and modifications can be made without departing from the spirit and principles of the invention, and are intended to be within the scope of the invention.
Claims (9)
1. A tensile-tensile fatigue test fixture for a ceramic matrix composite joggle structure is characterized by comprising an upper side round bar (1), a U-shaped plate (2), a clamping plate (3), a pin (4), a reinforcing sheet (5), a clamping plate bolt (6), a gasket (7), a tenon simulation piece (8), a transverse clamping piece (9), a longitudinal clamping piece (10), a mortise simulation piece (11), a transition section (12) and a lower side round bar (13); a clamping block of the fatigue testing machine clamps the cylindrical section of the upper round rod (1), and one end of the external thread of the upper round rod (1) is connected with the threaded hole of the U-shaped plate (2); the U-shaped plate (2) and the clamping plate (3) penetrate through the two pins (4) for positioning, the lower end of the clamping plate (3) clamps the tenon simulation piece (8) in a pressing mode through four clamping plate bolts (6), a gasket (7) is arranged between the nut and the clamping plate (3) at an interval, and metal reinforcing sheets (5) are adhered to two sides of a clamping section on the upper side of the tenon simulation piece (8); the lower end of the tenon simulation piece (8) is matched with the mortise simulation piece (11), two transverse clamping pieces (9) on the upper side of the mortise simulation piece (11) are fixed in a lap joint mode, and two longitudinal clamping pieces (10) on the upper side clamp the transverse clamping pieces (9) to prevent falling off; the external threads on the lower side of the mortise simulation part (11) are connected with the internal threads on the upper side of the transition section (12), a cooling water hole is formed in the transition section (12), and the internal threads on the lower side of the transition section (12) are connected with the external threads of the lower round rod (13); the cylindrical section of the lower round rod (13) is clamped on a fatigue testing machine; when a high-temperature test is carried out, a high-temperature furnace (14) is used for heating.
2. The ceramic matrix composite dovetail structure pull-pull fatigue test fixture according to claim 1, characterized in that: the upper side of the mortise simulation piece (11) is fixed by a transverse clamping piece (9) and a longitudinal clamping piece (10); the two transverse clamping pieces (9) are of U-shaped structures, and the end parts of the two transverse clamping pieces are used for fixing an opening above the mortise simulation piece (11) in an annular mode in a lap joint mode, so that the tenon simulation piece (8) is prevented from being pulled off due to excessive deformation of the mortise simulation piece (11) in a large-load test, and the test is prevented from failing; the two longitudinal clamping pieces (10) are of U-shaped structures, and are respectively arranged on two sides of the tenon simulation piece (8) to clamp the transverse clamping piece (9) from top to bottom, so that the transverse clamping piece (9) is prevented from being vibrated and falling off in the test process.
3. The ceramic matrix composite dovetail structure pull-pull fatigue test fixture according to claim 1, characterized in that: the two sides of the mortise simulation piece (11) and the transverse clamping pieces (9) have inclination angles of 6-12 degrees; the transverse clamping piece (9) and the longitudinal clamping piece (10) are fixed without blocking the joggle joint part, so that the joggle joint part can be observed conveniently in the test process.
4. The ceramic matrix composite dovetail structure pull-pull fatigue test fixture according to claim 1, characterized in that: the shim (7) is located between the clamping plate (3) and a nut for clamping the analogue part of the tenon (8).
5. The ceramic matrix composite joggle structure pulling-pulling fatigue test fixture of claim 1, characterized in that: the distance between the two clamping plates (3) can be freely adjusted according to the thickness of the clamping section of the tenon simulating piece (8).
6. The ceramic matrix composite joggle structure pulling-pulling fatigue test fixture of claim 1, characterized in that: the tongue-and-groove simulation piece (11), the transverse clamping piece (9), the longitudinal clamping piece (10) and the transition section (12) are made of one of cast high-temperature alloy, single-crystal high-temperature alloy or powder high-temperature alloy, and the rest parts are made of stainless steel materials outside the high-temperature furnace.
7. The ceramic matrix composite dovetail structure pull-pull fatigue test fixture according to claim 1, characterized in that: the lower side of the transition section (12) is provided with a cooling water hole, and cooling water flows through the clamp of the transition section (12) through an external water pipe to reduce the service temperature of the clamp.
8. The ceramic matrix composite dovetail structure pull-pull fatigue test fixture according to claim 1, characterized in that: the load transmission route of the upper side of the fatigue test clamp is as follows: the upper round bar (1) is transmitted to the U-shaped plate (2) through threads, and the threads bear axial force; the U-shaped plate (2) is transmitted to the clamping plate (3) through the pin (4), and the pin (4) is subjected to shearing force; the clamping plate (3) is transmitted to the tenon simulating piece (8) through friction force; the mortise simulation piece (11) and the transition section (12), the transition section (12) and the lower side round rod (13) transmit force through threads, and the threads are all subjected to axial force.
9. The method for testing a ceramic matrix composite dovetail structure pull-pull fatigue test fixture according to any one of claims 1-8, comprising the steps of:
step 1: assembling a test fixture: firstly, adhering reinforcing sheets (5) made of aluminum alloy to two sides of a clamping section above a tenon simulation piece (8) by adopting an adhesive, and standing for a certain time; then, the tenon simulating piece (8) is placed between the two clamping plates (3) and is screwed down through the four clamping plate bolts (6), and a gasket (7) is padded between the nut and the clamping plates (3); connecting the U-shaped plate (2) with the upper round rod (1) through threads, positioning the U-shaped plate (2) and the clamping plate (3) through the pin (4), assembling the clamp at the upper half part, and clamping the upper round rod (1) in the chuck at the upper side of the fatigue testing machine; the mortise simulation piece (11) is matched with the tenon simulation piece (8), the two transverse clamping pieces (9) above the mortise simulation piece (11) lock the deformation of the mortise simulation piece (11) in a lap joint mode, and the longitudinal clamping pieces (10) are respectively arranged above the transverse clamping pieces (9) and on two sides of the tenon simulation piece (8) and vertically clamp the transverse clamping pieces (9) downwards; the upper internal thread and the lower internal thread of the transition section (12) are respectively connected with the mortise simulation piece (11) and the lower side round rod (13), the cylindrical section of the lower side round rod (13) is connected with a lower end chuck of the fatigue testing machine, and the clamp is assembled;
step 2: setting test parameters according to the real working condition of the ceramic matrix composite joggle joint structure, setting a measuring point at the checking section of the joggle joint part, and laying a thermocouple; a fiber bragg grating sensor is arranged on the other side of the tenon joint structure, and the damage state of the tenon joint structure is monitored; opening a cooling water passage and checking the water tightness; placing the high-temperature furnace at the tenon joint structure, and applying a uniform temperature field;
and 3, step 3: after the step 2 is finished, performing a strength or fatigue test on the joggle joint structure of the ceramic matrix composite material, ensuring that the temperature in the high-temperature furnace meets the test requirement through a temperature controller, and preserving the heat for one hour after the temperature displayed by the thermocouple reaches a set temperature, and starting the test; and applying corresponding load conditions through a load controller of the fatigue testing machine, and finishing the test when the tenon joint structure of the ceramic matrix composite material reaches the specified service life or fails.
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