CN115078119A - High-temperature pull-pull fatigue test system and method - Google Patents
High-temperature pull-pull fatigue test system and method Download PDFInfo
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- CN115078119A CN115078119A CN202210758872.9A CN202210758872A CN115078119A CN 115078119 A CN115078119 A CN 115078119A CN 202210758872 A CN202210758872 A CN 202210758872A CN 115078119 A CN115078119 A CN 115078119A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
- G01N3/18—Performing tests at high or low temperatures
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/32—Investigating strength properties of solid materials by application of mechanical stress by applying repeated or pulsating forces
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0058—Kind of property studied
- G01N2203/0069—Fatigue, creep, strain-stress relations or elastic constants
- G01N2203/0073—Fatigue
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Abstract
The invention discloses a high-temperature pull-pull fatigue test system and a method, and designs a clamping device which can adapt to the thickness change of a sample and ensure the accurate centering of the sample based on a cold clamping mode; a movable thermocouple device is also designed, wherein the thermocouple is contacted with the sample in the stages of temperature rise and heat preservation, and the thermocouple slides to a position 3-6 mm away from the surface of the sample when the fatigue loading is formally started; and the silicon dioxide aerogel composite material is selected to manufacture the heat insulation felt and is placed at the upper opening of the high-temperature furnace, so that hot air flow continuously rising in the high-temperature furnace is blocked, the risk of overheating of a chuck and a sensor system above the testing machine in a long-time fatigue test is eliminated, and the stability and the uniformity of a temperature field of the high-temperature furnace are improved. The invention carries out technical innovation from the three aspects of clamping device, temperature measurement and control and high-temperature furnace heat insulation, effectively solves the technical problem of high-temperature pull-pull fatigue test, and improves the technical level of the high-temperature pull-pull fatigue test of the SiC-based composite material.
Description
Technical Field
The invention relates to the technical field of material mechanical property testing, in particular to a system and a method for testing high-temperature pull-pull fatigue of a SiC-based composite material, which are specially used for the pull-pull fatigue test of a silicon-based composite material under the conditions of long time and high temperature, and the high-temperature pull-pull fatigue test of other materials can be referred to.
Background
The ceramic matrix composite material is a composite material formed by introducing a reinforcing material into a ceramic matrix. The ceramic matrix composite material has the advantages of high strength, high modulus, high temperature resistance, corrosion resistance and the like of the ceramic material, and meanwhile, the reinforcement can improve the crack propagation resistance of the material and overcome the weakness, namely brittleness, of the ceramic material. There are three types of ceramic matrices commonly used: (1) a glass-ceramic matrix, typically representing a calcium aluminosilicate glass; (2) oxide matrix, typically Al 2 O 3 (ii) a (3) A non-oxide matrix, typically representing SiC. At home and abroad, the ceramic matrix composite material which can be finally applied to the hottest end part of an aeroengine is generally considered to be a composite material of a continuous fiber reinforced SiC matrix, in particular to SiC f/ SiC。
The tensile-tensile fatigue property is a mechanical property which needs to be mainly investigated in application evaluation of almost all materials, particularly for SiC-based composite materials, a SiC matrix is brittle, the matrix is firstly cracked under the cyclic loading of the tensile-tensile fatigue, and micro-damage such as debonding of a fiber matrix interface and fiber pulling-out is induced along with the gradual expansion of cracks in the matrix, so that the fatigue fracture of the materials is finally caused. The real service environment of the SiC-based composite material is high temperature, in order to evaluate the long-term service performance of the material, a tensile-tensile fatigue test of the SiC-based composite material under the high-temperature environment must be carried out, and the tensile-tensile fatigue performance of the SiC-based composite material under the high temperature is a main index for evaluating the performance of the material and is also an important basis for design and life prediction.
However, under the existing technical conditions, the high temperature pull-pull fatigue test of the SiC-based composite material has the following three technical difficulties in implementation:
(1) a clamping device. The existing clamping device is divided into three types, namely hydraulic clamping, Y-shaped end sample hanging and pin connection. Wherein, the hydraulic pressure centre gripping needs to paste the enhancement piece to the sample, and the clamp splice centre gripping sample of direct with the testing machine is easy to the sample clamp bad, and in fatigue test, the stress concentration and the alternating load of centre gripping root superpose each other moreover, make the sample often break in centre gripping department or centre gripping root. The clamping device for hanging the Y-shaped end sample realizes tension self-locking by utilizing the principle that the inclination of the side surface of the sample is the same as that of the side surface of the clamp groove, but has the problems of difficulty in ensuring accurate centering of the sample, unstable force transmission and the like. The pin connection mode needs to punch and penetrate a pin on a sample so as to be connected with a testing machine, the SiC-based composite material is brittle, and the punched part is often damaged by adopting a bolt connection mode. By reducing the aperture, the mode of connecting a plurality of holes and pins leads to difficult sample processing and overhigh cost.
(2) And (4) temperature measurement technology. There are certain temperature gradient and temperature deviation in the high temperature furnace, little volume high temperature furnace above-mentioned problem that the cooperation cold centre gripping mode was used is more serious, and conventional method is to adopt the asbestos rope to tie up three noble metal thermocouple in sample gauge length within range (gauge length both ends respectively set up 1, set up 1 in the middle of the gauge length), and make the temperature measurement terminal and the sample surface in close contact with of noble metal thermocouple, observe and control the temperature of these two thermocouples through the precision, ensure that sample gauge length section reaches required test temperature. Because the SiC-based composite material can be chemically reflected with Bt in the noble metal thermocouple under the high-temperature environment for a long time, the noble metal thermocouple cannot be directly contacted with a SiC-based composite material sample in a fatigue test, but the accurate control of the temperature of the sample cannot be ensured if the noble metal thermocouple is not directly contacted.
(3) And (4) heat insulation of the high-temperature furnace. The SiC-based composite material has the advantages of mild service condition, higher temperature, longer service life needing examination, and double examination of long time and high temperature, so that the heat insulation problem of the high-temperature furnace is highlighted. A large number of practices show that in the fatigue test process, hot air flow rising continuously in the high-temperature furnace flows out through a gap between the high-temperature furnace and a sample, parts and a system above the testing machine are heated continuously, in a long-time high-temperature fatigue test, a clamping block, a clamping head and a sensor above the testing machine are heated continuously to cause overheating, the accuracy of the sensor of the testing machine is possibly affected, the testing machine system and the parts of the testing machine are damaged seriously, and therefore the high-temperature furnace used in the high-temperature fatigue test must be insulated. In addition, the heating efficiency and the temperature uniformity of the high-temperature furnace can be improved by an effective heat insulation means, and the temperature fluctuation is reduced.
Disclosure of Invention
In view of the above, the present invention provides a high temperature pull-pull fatigue test system and method, starting with a clamping device, temperature measurement and control, and high temperature furnace thermal insulation, and designing a high temperature fatigue test clamping device capable of adapting to any thickness sample and accurately centering, and a temperature measurement device capable of separating a thermocouple welding head from the sample without opening a furnace in a fatigue test, so as to implement a test temperature measurement and control method of temperature measurement in a heating and heat preservation stage and indirect temperature measurement in a fatigue test stage, and provide an effective thermal insulation scheme for a high temperature furnace.
In order to achieve the purpose, the invention provides the following technical scheme:
a high temperature pull-pull fatigue test system, comprising: a clamping device;
the clamping device includes: the first assembly and the second assembly are matched in pair and have the same structure; the first assembly comprises: a first swash block;
a first groove used for mounting a sample is formed in the clamping surface side of the first inclined block, the first groove is provided with an end side wall and two opposite inclined side walls, two ends of the end side wall are respectively connected to first ends of the two inclined side walls, and an end slot opening opposite to the end side wall is formed between second ends of the two inclined side walls;
the width of the end notches is less than the width of the end side walls.
Preferably, the first groove is an isosceles trapezoid groove, the two inclined side walls are two waists respectively, and the end side wall and the end notch are two bottoms respectively.
Preferably, the depth of the first groove is less than half the thickness of the test piece;
the second assembly comprises: a second swash block;
when the sample is arranged in the first grooves of the first inclined block and the second inclined block, a gap is formed between the first inclined block and the second inclined block.
Preferably, the depth of the first groove is 0.05mm to 0.25mm less than half the thickness of the test piece.
Preferably, the first assembly further comprises: a first clamping block;
and a second groove matched with the first inclined block in shape is formed in the clamping surface side of the first clamping block.
Preferably, the first inclined block is T-shaped, and the second groove is a T-shaped groove.
Preferably, the first clamping block is provided with a water through hole;
and/or a first clamping block fixing rod and a second clamping block fixing rod are respectively arranged on two sides of the first clamping block.
Preferably, the method further comprises the following steps: the device comprises a high-temperature furnace, a thermocouple, a bracket base and a slide rail;
the outer wall of the high-temperature furnace is provided with a through hole for the thermocouple to pass through, the thermocouple is arranged on the support, the support is slidably arranged on the sliding rail through the support base, and the sliding rail is parallel to the axial direction of the through hole.
Preferably, the method further comprises the following steps: a high temperature furnace and a heat insulation blanket;
the heat insulation felt is arranged at a middle opening above the high-temperature furnace for the sample to pass through.
Preferably, the material of the insulation blanket is an aerogel composite.
Preferably, the high temperature furnace includes: a high temperature furnace left half and a high temperature furnace right half;
the heat insulation felt comprises: the first heat insulation felt is arranged at the top of the left half part of the high-temperature furnace, and the second heat insulation felt is arranged at the top of the right half part of the high-temperature furnace;
and rectangular openings are respectively formed in the centers of the opposite sides of the first heat insulation felt and the second heat insulation felt, and are combined to form a rectangular passage for the sample to pass through.
A high-temperature pull-pull fatigue test method adopts the high-temperature pull-pull fatigue test system.
According to the technical scheme, the invention has the beneficial effects that:
1. the invention relates to a high-temperature tensile-tensile fatigue test system and a method for SiC-based composite materials, which designs a clamping device combined by a clamping block with a T-shaped groove and a T-shaped inclined block with a trapezoidal groove, a Y-shaped end sample part is hung in the trapezoidal groove of the T-shaped inclined block during clamping, the sum of the depths of the trapezoidal grooves in a pair of T-shaped inclined blocks is less than the thickness of a sample, a small gap exists between the two T-shaped inclined blocks after the T-shaped inclined blocks are assembled with the sample, the small gap can ensure that the clamping block can provide a transverse clamping force for the sample after the two clamping blocks are clamped, a load can be transmitted to the sample by inducing friction force during tensile loading, a Y-shaped end part of the sample can form structural self-locking after being pressed with the T-shaped inclined block, the load can be transmitted by contact pressure, the clamping device realizes the mixing mode of hydraulic clamping and Y-shaped end sample hanging clamping, and the load of a testing machine can be transmitted before the sample contacts with a clamp, The force is simultaneously transferred by the rear surface, the left surface and the right surface, the force transfer of the front surface and the rear surface is based on a hydraulic clamping principle, the force transfer of the left side surface and the right side surface is based on a Y-shaped end sample hanging clamping principle, the stress concentration at the contact surface of the clamp and the sample in the situation of independently adopting any one of the clamping modes can be reduced, the sample is prevented from being abnormally clamped and damaged, and the effective load transfer is ensured.
2. The invention relates to a high-temperature pull-pull fatigue test system and method for SiC-based composite materials, which designs a clamping device combining a clamping block with a T-shaped groove and a T-shaped inclined block with a trapezoidal groove. When the thickness of different groups of samples is changed greatly, only one set of T-shaped inclined block meeting the requirement of the grooving depth needs to be replaced, so that the clamping device has good universality and remarkable economy.
3. The invention relates to a high-temperature pull-pull fatigue test system and method for SiC-based composite materials, which is a test temperature measurement and control method for realizing contact temperature measurement in a heating and heat preservation stage and indirect temperature measurement in a fatigue test stage by designing a movable thermocouple test system. In the heating and heat preservation stages of the fatigue test, the thermocouple temperature measurement welding head is in close contact with the surface of the sample, when the fatigue loading is started, the thermocouple temperature measurement welding head can be separated from the sample through the movable support under the condition that a high-temperature furnace is not required to be opened for manually removing the thermocouple, the temperature measurement precision and the temperature control accuracy which are the same as those of the thermocouple which is bound on the surface of the sample in the whole process can be achieved, and meanwhile, the problem that the thermocouple welding head and the sample are in long-term contact and can generate chemical reaction in a high-temperature environment is effectively avoided.
4. According to the high-temperature tensile-tensile fatigue testing system and method for the SiC-based composite material, the technical scheme that the aerogel is used for manufacturing the high-temperature furnace heat-insulating anvil for high-temperature fatigue is put forward for the first time, so that rising hot air flow of the high-temperature furnace can be effectively blocked, the temperature rise of system components above a testing machine is not obvious in long-time fatigue loading, and the risk of overhigh temperature rise of the system components of the testing machine in high-cycle and long-time fatigue tests is eliminated. The use of the aerogel composite material heat insulation anvil also greatly improves the sealing performance of the high-temperature furnace, and the temperature field in the high-temperature furnace can be more stable and uniform.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a schematic diagram of an exploded structure of a first assembly according to an embodiment of the present invention;
FIG. 2 is a schematic three-dimensional structure of a clamping device provided in an embodiment of the present invention, assembled with two parts of a sample;
FIG. 3 is a schematic diagram of a head-up view of a clamping device in accordance with an embodiment of the present invention assembled with a test sample;
FIG. 4 is a schematic top view of a sample assembled with a pair of blocks according to an embodiment of the present invention;
FIG. 5 is a schematic structural view of an insulation blanket arranged above a heating furnace according to an embodiment of the present invention;
FIG. 6 is a detailed view of the shape of an insulation blanket provided by an embodiment of the present invention;
FIG. 7 is a schematic diagram of an assembly structure of parts of a high temperature pull-pull fatigue test system according to an embodiment of the present invention;
fig. 8 is an assembly structure diagram of the high temperature pull-pull fatigue testing system and the testing machine according to the embodiment of the present invention.
Wherein, 1-a first clamping block; 2-a first swash block; 3-sample; 4-a third clamp splice; 5-a third swash block; 6-a second clamping block; 7-second sloping block; 8-a fourth clamping block; 9-fourth swash block; 11-T-shaped slot, 111-first inclined plane; 12-water through hole; 13-a first clamping block fixing rod, 14-a second clamping block fixing rod; 21-trapezoidal groove, 211-end side wall, 212-oblique side wall, 213-end notch, 22-first portion, 23-second portion, 231-second oblique surface; 27-a gap; 31-left half part of high temperature furnace; 32-the right half of the high temperature furnace; 33-a support; 34-a bracket base; 35-a slide rail; 36-a connecting arm; 37-connecting beam; 41-left column of testing machine, 42-right column of testing machine; 43 — system support; 44-the upper chuck of the testing machine, 45-the lower chuck of the testing machine; 101-a first sheathed thermocouple, 102-a second sheathed thermocouple, 103-a third sheathed thermocouple; 104-a first bore passage, 105-a second bore passage, 106-a third bore passage; 310-a first insulation blanket, 320-a second insulation blanket; 330 — rectangular vias.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the 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, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The high-temperature pull-pull fatigue test system provided by the embodiment of the invention comprises: a clamping device, the structure of which can be seen in fig. 1-3;
wherein, this clamping device includes: a first assembly and a second assembly which are matched in pairs (respectively clamping two sides of the upper end of the sample 3) and have the same structure, and a third assembly and a fourth assembly which are matched in pairs (respectively clamping two sides of the lower end of the sample 3) and have the same structure; the first assembly comprises: a first swash block 2;
a first groove for mounting the sample 3 is arranged on the clamping surface side of the first inclined block 2, the first groove is provided with an end side wall 211 and two opposite inclined side walls 212, two ends of the end side wall 211 are respectively connected with first ends of the two inclined side walls 212, and an end notch 213 opposite to the end side wall 211 is formed between second ends of the two inclined side walls 212;
the width of the end notch 213 is smaller than the width of the end side wall 211, i.e. both sloping side walls 212 slope inwardly towards a portion of the end notch 213 and outwardly towards a portion of the end side wall 211.
It can be seen from the above technical solutions that, in the high-temperature pull-pull fatigue testing system provided by the embodiment of the present invention, the oblique side wall 212 of the first groove in the first oblique block 2 is matched with the two oblique side surfaces of the sample 3, as shown in fig. 1 and fig. 2, under the action of a tensile load, the shape of the sample 3 and the first groove which are narrower from top to bottom can realize tensile self-locking through the oblique surface contact therebetween.
Specifically, the first groove is an isosceles trapezoid-shaped groove 21, the two inclined side walls 212 are two waists, and the end side wall 211 and the end notch 213 are two bottoms, and the structure thereof can be shown in fig. 1 to 3. The end side wall 211 and the end notch 213 are perpendicular to the specimen 3 and its stretching direction.
In order to further optimize the technical scheme, the depth of the first groove is less than half of the thickness of the sample 3;
the aforementioned second assembly comprises: the second inclined blocks 7 are matched with the first inclined blocks 2 in pairs and used for clamping two sides of the sample 3 respectively;
as shown in fig. 4, when the sample 3 is mounted in the first grooves of the first and second swash blocks 2 and 7, a gap 27 is formed between the first and second swash blocks 2 and 7. Namely, after the sample 3 is clamped by the first sloping block 2 and the second sloping block 7, the pair of sloping blocks are not jointed, but have a small gap 27; the small gap 27 ensures that the clamping device can adapt to the thickness change of the test samples 3, and ensures that the central axis of each test sample 3 is accurately aligned with the central axis loading line of the test piece.
Preferably, the depth of the first groove is 0.05mm to 0.25mm less than half the thickness of the sample 3. Namely, after the pair of the inclined blocks are oppositely folded from the side of the slotting surface, the depth of the trapezoidal groove formed by the two inclined blocks is 0.1 mm-0.5 mm smaller than the thickness of the sample, so that the sample can be ensured to have enough side clamping, and the sample is ensured to be naturally centered after being clamped. Accordingly, the present invention can also machine a series of T-shaped ramp blocks with different groove depths to accommodate samples of significantly different thicknesses.
In this embodiment, the first assembly further comprises: a first clamp block 1, the structure of which can be seen in fig. 1 and 2;
a second groove which has the same shape with the first inclined block 2 is arranged on the clamping surface side of the first clamping block 1. Namely, the clamping device is of a split structure, and the heat transferred to the clamping block with the T-shaped groove by the sample 3 through the T-shaped inclined block is limited, so that the clamping block with the T-shaped groove can be prepared from common steel meeting the requirements on rigidity and hardness, and the problem of high temperature resistance does not need to be considered.
Specifically, the first inclined block 2 is T-shaped, and the second groove is a T-shaped groove 11. As shown in fig. 1, the first swash block 2 includes: a first portion 22 and a second portion 23; the first portion 22 extends in a first direction, and the second portion 23 extends in a second direction perpendicular to the first direction; a first end of the second portion 23 is connected to the first portion 22. Further, both sides of the second portion 23 along the first direction are second inclined surfaces 231, and the second inclined surfaces 231 face the second end of the second portion 23; the side wall of the T-shaped slot 11 has a first inclined surface 111 that cooperates with a second inclined surface 231.
Preferably, the first clamping block 1 is provided with a water through hole 12, and the structure of the first clamping block can be shown in fig. 1 and is used for connecting with circulating water in a fatigue test to realize the cooling of the clamping block;
and/or a first clamping block fixing rod 13 and a second clamping block fixing rod 14 are respectively arranged on two sides of the first clamping block 1 and are used for being connected with a chuck of the testing machine, and when the clamping blocks are installed on the chuck of the testing machine, the clamping blocks are connected with the chuck of the testing machine through springs so as to realize fixation.
The high-temperature pull-pull fatigue test system provided by the embodiment of the invention further comprises: the structure of the high-temperature furnace, the thermocouple, the bracket 33, the bracket base 34 and the slide rail 35 can be seen in fig. 7;
the outer wall of the high-temperature furnace is provided with a through hole for a thermocouple to pass through, the thermocouple is mounted on the support 33, the support 33 is slidably mounted on the sliding rail 35 through the support base 34, and the sliding rail 35 is parallel to the axial direction of the through hole. In the heating and heat preservation stages of a fatigue test, a thermocouple temperature measuring contact is in close contact with the surface of a sample, and when fatigue loading is started, the thermocouple temperature measuring contact can be separated from the sample through a movable support under the condition that a high-temperature furnace is not required to be opened for manually removing a thermocouple, so that the problem that the thermocouple contact and a SiC-based composite material sample are in long-term contact and can generate chemical reaction is solved, and meanwhile, the temperature measuring precision and the temperature control accuracy which are the same as those of the thermocouple bound on the surface of the sample in the whole process can be expected.
The high-temperature pull-pull fatigue test system provided by the embodiment of the invention further comprises: a high temperature furnace and an insulation blanket, the structure of which can be seen with reference to fig. 5 and 7;
the heat insulation felt is arranged at the middle opening above the high-temperature furnace for the sample 3 to pass through, so that the sealing of the high-temperature furnace is realized, and the rising hot air flow of the high-temperature furnace can be blocked.
Preferably, the material of the heat insulation felt is aerogel composite material (silica is used as a matrix, mullite fiber is used as a reinforcing phase), and the requirement of a high-temperature test can be met.
Further, the high temperature furnace includes: a high temperature furnace left half 31 and a high temperature furnace right half 32, the structure of which can be seen with reference to fig. 5 and 7;
this thermal-insulated felt includes: a first insulation blanket 310 disposed on top of the left half 31 of the high temperature furnace, and a second insulation blanket 320 disposed on top of the right half 32 of the high temperature furnace;
the centers of the opposite sides of the first and second insulation blankets 310 and 320 are opened with rectangular openings, respectively, to form a rectangular passage 330 for fitting with the sample 3, the structure of which can be seen in fig. 6.
The embodiment of the invention also provides a high-temperature pull-pull fatigue testing method, which adopts the high-temperature pull-pull fatigue testing system.
The invention is further illustrated below with reference to specific embodiments:
the present invention can be more clearly understood without thereby limiting the scope of protection of the invention.
The high-temperature pull-pull fatigue test system for the SiC-based composite material is technically innovated from three aspects of a clamping device, temperature measurement and control and high-temperature furnace heat insulation, effectively solves the technical problem of the high-temperature pull-pull fatigue test of the SiC-based composite material, and is discussed with respect to the technical schemes of the three aspects.
1. The clamping device adopts a combination of a T-shaped inclined block with a trapezoidal groove and a wedge-shaped clamping block with a T-shaped groove.
A high-temperature tensile-tensile fatigue testing system and method for SiC-based composite materials are characterized by comprising a clamping device which can adapt to any change of the thickness of a sample and ensure the accurate centering of the sample, wherein the clamping device consists of four wedge-shaped clamping blocks with T-shaped grooves and four T-shaped inclined blocks, and each wedge-shaped clamping block and each T-shaped inclined block are used in a combined mode. Taking one of the assemblies as an example, as shown in fig. 1, the first assembly is composed of two parts, namely a first clamping block 1 with a T-shaped groove and a T-shaped first inclined block 2, the middle part of the lower part of one side of the clamping surface of the first clamping block 1 with the T-shaped groove is provided with a T-shaped groove 11, the shape and the size of the T-shaped groove 11 are completely the same as the configuration of the T-shaped first inclined block 2, and when the first assembly is used in a test, the first inclined block 2 is only required to be placed in the first clamping block 1 with the T-shaped groove. In addition, a water through hole 12 is formed in the side face of the first clamping block 1 with the T-shaped groove and used for being connected with circulating water in a fatigue test to achieve cooling of the clamping block, two clamping block fixing rods 13 and 14 extending outwards are designed on the two sides of the clamping block and used for being connected with a chuck of a testing machine, and when the clamping block is installed on the chuck of the testing machine, the clamping block is connected with the chuck of the testing machine through a spring so as to achieve fixing. The middle area below the first inclined block 2 of the T shape is provided with a trapezoidal groove 21, and the shape of the trapezoidal groove is the same as that of the two ends of the fatigue test sample 3 at the Y-shaped end part. Taking an assembly of a pair of wedge-shaped clamping blocks and a T-shaped inclined block on the left side of the clamping device as an example, when a sample is installed in the clamping device, the upper end and the lower end of a Y-shaped end sample 3 are hung and clamped in a first inclined block 2 on the upper side and a third inclined block 5 on the lower side. The assembled three-dimensional and plan views of the Y-shaped end sample and the upper and lower T-shaped swash blocks 2, 5 and the T-shaped swash blocks and T-shaped channel blocks 1, 4 are shown in fig. 2 and 3, respectively.
In addition, in order to adapt to different sample thicknesses and ensure accurate centering of a sample central axis and a central axis loading line of a testing machine, the depth of a trapezoidal groove in a T-shaped oblique block is slightly smaller than half of the sample thickness, and after a pair of T-shaped oblique blocks are oppositely folded from one side of a slotted surface, the depth of the trapezoidal groove formed by the T-shaped oblique blocks and the test sample is smaller than the thickness of the test sample by 0.1-0.5 mm, so that after the test sample is clamped between the T-shaped oblique blocks, the T-shaped oblique blocks are not attached, and a small gap (0.1-0.5 mm) exists between the T-shaped oblique blocks. Taking a pair of T-shaped inclined blocks 2 and 7 matched with a pair of wedge-shaped clamping blocks in a chuck on a testing machine as an example, as shown in fig. 4, when the upper end of a Y-shaped end sample 3 is clamped at the trapezoidal grooves of the pair of T-shaped inclined blocks 2 and 7, the sum of the depths of the two trapezoidal grooves on the T-shaped inclined blocks 2 and 7 is slightly smaller than the thickness of the Y-shaped end sample 3, and after the sample is clamped between the pair of T-shaped inclined blocks 2 and 7, the pair of T-shaped inclined blocks 2 and 7 are not jointed but have a small gap 27. The small gap can realize accurate centering of each sample, and can also generate transverse pressing force, force transmission channels on the front surface and the rear surface of the sample based on the friction principle are increased, the contact pressure of two side surfaces of the sample is reduced, the sample is prevented from being crushed in advance, and the force transmission stability of the clamping device can also be improved. The T-shaped inclined blocks with different groove depths can be processed, and in the test, the T-shaped inclined blocks can be replaced for samples with any thickness, so that the requirement that the depth of a trapezoidal groove formed by the two T-shaped inclined blocks is 0.1-0.5 mm smaller than the thickness of the samples can be met. Because the T-shaped inclined block is in direct contact with the sample, the T-shaped inclined block may have an overheating problem, and in order to ensure that the T-shaped wedge block can still effectively restrain the sample at high temperature and does not deform or damage, the T-shaped wedge block is suggested to be prepared by high-temperature alloy which can resist the high temperature of more than 600 ℃. The T-shaped inclined block and the clamping block provided with the T-shaped groove are separated, and the heat of the sample transferred to the clamping block provided with the T-shaped groove through the T-shaped inclined block is limited, so that the clamping block provided with the T-shaped groove can be prepared from common steel meeting the requirements on rigidity and hardness, and the problem of high temperature resistance does not need to be considered.
The invention adopts the T-shaped inclined block and has the advantages that: only a plurality of sets of T-shaped inclined blocks with different groove depths are required to be processed, and for samples with any thickness, the T-shaped inclined blocks with proper groove depths can be selected to meet the requirement that the depth of a trapezoidal groove formed by two T-shaped inclined blocks is 0.1-0.5 mm smaller than the thickness of the sample, so that the designed clamping device can be suitable for the pull-pull fatigue test of the samples with large variation in thickness range. In addition, the T-shaped inclined block and the wedge-shaped clamping block are separated, and the sample is directly contacted with the T-shaped inclined block for heat transfer, so that the T-shaped inclined block is prepared only by adopting high-temperature alloy, the wedge-shaped clamping block is made of common steel, and the manufacturing difficulty and the processing cost of the clamping device are low.
2. Temperature measurement-contact temperature measurement in the temperature rise and heat preservation stages, and indirect temperature measurement in the fatigue test process.
The high temperature furnace all has certain temperature gradient, the temperature deviation, little volume high temperature furnace that uses to the cold centre gripping mode of cooperation above-mentioned problem is more serious, conventional method is to adopt the asbestos rope to tie up the noble metal thermocouple at sample gauge length within range (the gauge length both ends respectively set up 1, set up 1 in the middle of the gauge length), and make the temperature measurement terminal and the sample surface in close contact with of noble metal thermocouple, through the temperature of these two thermocouples of accurate observing and controlling, ensure that sample gauge length section reaches required experimental temperature. Because the SiC-based composite material can be chemically reflected with Bt in the noble metal thermocouple under the high-temperature environment for a long time, the noble metal thermocouple cannot be directly contacted with a SiC-based composite material sample in a fatigue test, but the accurate control of the temperature of the sample cannot be ensured if the noble metal thermocouple is not directly contacted. In order to solve the technical difficulty, a fatigue test temperature measurement and control scheme of contact temperature measurement in the temperature rise and heat preservation stages and indirect temperature measurement in the fatigue test process is provided, and therefore a movable thermocouple test system is designed. Three armored thermocouples 101, 102 and 103 for measuring the temperature of a gauge length section are arranged on a support 33, a support base 34 below the support 33 is designed to be T-shaped so as to slide on a sliding rail 35 with a T-shaped groove below the support, the sliding rail 35 is connected to a connecting beam 37 through a connecting arm 36, the connecting beam 37 is used for connecting all parts of the system and is connected with a testing machine, and the distance between the thermocouples and the surface of a sample can be adjusted by moving the position of the support base 34 on the sliding rail 35 in the testing process. In cooperation, the high temperature furnace is provided with three circular hole passages 104, 105, 106 on one side, and the diameter of the circular hole is slightly larger than that of the armored thermocouple, so that the three armored thermocouples can smoothly pass through the corresponding circular holes and extend into the high temperature furnace. In the fatigue test, the positions of the supports can be adjusted in the heating and heat preservation stages, so that the three thermocouple temperature measuring welding heads are in direct contact with the surface of the sample, the accuracy of temperature measurement and control is ensured, and when the fatigue test is started, the high-temperature furnace is not required to be opened, and the thermocouple supports above the sliding rails are pulled and pulled, so that the thermocouple temperature measuring welding heads are separated from the surface of the sample by 3-6 mm.
3. The heating system is insulated, namely an aerogel composite material (silicon dioxide is used as a matrix, and mullite fiber is used as a reinforcing phase) heat insulation felt is adopted.
A large number of practices show that in the fatigue test process, hot air flow rising continuously in the high-temperature furnace flows out through a gap between the high-temperature furnace and a sample, parts and a system above the testing machine are heated continuously, in a long-time high-temperature fatigue test, a clamping block, a clamping head and a sensor above the testing machine are heated continuously to cause overheating, the accuracy of the sensor of the testing machine is possibly affected, the testing machine system and the parts of the testing machine are damaged seriously, and therefore the high-temperature furnace used in the high-temperature fatigue test must be insulated. In addition, the heating efficiency of the heating system can be improved by an effective heat insulation means, the temperature uniformity of the high-temperature furnace is improved, and the temperature fluctuation degree of the high-temperature furnace is reduced.
The method is characterized in that two heat insulation felts 310 and 320 are made of aerogel composite materials and are arranged at a middle opening through which a sample passes above a high-temperature furnace, a rectangular opening is cut at the center of one side of each of the two heat insulation felts 310 and 320, the two heat insulation felts are combined to form a rectangular passage 330, and the rectangular passage 330 is slightly smaller than the section of the sample at the contact position of the sample and the heat insulation felts. Before the high temperature furnace opened the heating, the rectangle opening part of two blocks of silica aerogel combined material heat insulation felts was packed into to the sample, then place the top with the high temperature furnace with silica aerogel combined material heat insulation felt, the contact between adjustment heat insulation felt and sample and the stove guarantees sealed well, makes heat insulation felt can not produce extra power to the sample, effectively blocks the rising channel of hot gas flow simultaneously.
The schematic diagram of a SiC-based composite high-temperature tensile-tensile fatigue testing system including all components is shown in fig. 7, the whole system is connected to a support frame 43 with a guide rail through a connecting beam 37, the support frame is connected with two upright posts 41 and 42 of a testing machine, and the connection mode and the assembly with the testing machine are shown in fig. 8.
As a preferred mode, all parts of the whole system are connected to a support frame with a guide rail through connecting beams, the support frame is connected with two stand columns of the testing machine, and the connecting structure has position adjustability and can be used for guaranteeing mechanical testing of samples with different sizes.
As a preferable mode, the T-shaped inclined block in the designed clamping device is suggested to be made of high-temperature alloy which can resist the high temperature of more than 600 ℃, and the wedge-shaped clamping block with the T-shaped groove is suggested to be made of steel materials meeting the requirements of rigidity and hardness.
The SiC-based composite material high-temperature tensile-tensile fatigue test system and method are based on a cold clamping mode, so that the system and method can only be matched with a small-volume high-temperature furnace which is shorter than a sample in length for use.
The system and the method for testing the high-temperature pull-pull fatigue of the SiC-based composite material can be suitable for the pull-pull fatigue test of the SiC-based composite material in a high-temperature environment below 1600 ℃.
The system and the method for testing the high-temperature pull-pull fatigue of the SiC-based composite material are suitable for the pull-pull fatigue test of a Y-shaped end sample of the SiC-based composite material.
The high-temperature pull-pull fatigue test system and method for the SiC-based composite material are specially used for high-temperature fatigue test of the fiber reinforced ceramic-based composite material taking SiC as a matrix, and can also be used for reference in high-temperature fatigue test of other materials which can generate chemical reaction when in long-term contact with a noble metal thermocouple.
For better understanding of the present invention, the following examples are further provided to illustrate the present invention, but the present invention is not limited to the following examples:
example (b): to the orthogonally layered SiC f Taking the/SiC composite material as an example, the high-temperature tensile-tensile fatigue test of the material at 1200 ℃ is carried out, the loading frequency is 30Hz, the maximum stress level is 140MPa, and the stress ratio is 0.01. The fatigue testing machine is an MTS hydraulic servo fatigue testing machine, the heating device adopts a high-temperature furnace with the appearance height of 110mm and the soaking zone length of 30mm and is heated by a silicon carbide rod. The method comprises the following specific steps:
(1) measuring the width and thickness of a gauge length section of a fatigue test sample at the Y-shaped end part to be 5.93mm and 2.93mm respectively, calculating the sectional area of the gauge length section of the test sample, and calculating the maximum load P of fatigue loading according to the set stress level of 140MPa max And 2085N, setting fatigue test parameters such as load, loading frequency, stress ratio, data acquisition frequency, sampling frequency and the like on the testing machine.
(2) Install four wedge water-cooling clamp blocks that open the T-slot in the upper and lower chuck 44, 45 of testing machine, select one set (containing four) fluting T shape sloping block that the specification is suitable for use according to sample thickness, install 4 fluting T shape sloping blocks respectively in four wedge clamp blocks, install the sample upper and lower end in two T shape sloping blocks on the left side of test system, down, control the test machine chuck and press from both sides tightly the sample, make trapezoidal tank bottom in the upper and lower two T shape sloping blocks on the right side laminate with the sample, it is about 1MPa to set up clamping-force, apply a preload about 50N simultaneously, make the sample hung, centre gripping in the T shape sloping block in the wedge clamp block.
(3) Adjust the position of high temperature furnace, make the length direction of the relative sample of high temperature furnace placed in the middle, adjust the position of thermocouple support on the slide rail, make the side of the bonding tool contact sample of three armor thermocouples, put together two parts of high temperature furnace, and place the thermal-insulated felt of aerogel combined material at the top opening part of high temperature furnace, ensure the thermal-insulated felt of aerogel combined material, the sample, sealing between the high temperature furnace, set up heating temperature on the high temperature furnace controller, nevertheless link to each other the limbers on water pipe and the wedge clamp splice, open the circulating water, make flowing water pass through the water-cooling clamp splice, open the heating function of heating furnace simultaneously.
(4) The temperature readings of the three armored thermocouples are monitored to reach the set target temperature, and the temperature is kept for 20 minutes after the target temperature is reached. After heat preservation is completed, on the premise of not opening the high-temperature furnace, the position of the thermocouple support on the slide rail is slightly moved towards the direction far away from the high-temperature furnace, the moving distance is about 3-6 mm, and the temperature measuring welding head of the thermocouple is separated from the surface of the sample.
(5) And starting a fatigue testing machine, and carrying out fatigue loading on the sample according to the preset setting. The stable temperature that reaches behind the accessible three armor thermocouples of breaking away from the sample surface in the test process guarantees that the temperature control of high temperature furnace is in the required scope, because this system adopts aerogel combined material heat insulating felt to seal, and the temperature field in the high temperature furnace is more even, more stable, and this has also guaranteed through the temperature value of three armor thermocouples that break away from the sample surface of control, realizes the validity of high temperature furnace temperature accurate control.
(6) And stopping the test when the preset target cycle number is reached or the test sample is broken.
In this example, SiC is used at the set maximum stress level and stress ratio f The fatigue test sample of the/SiC composite material passes through 10 7 After the target life of (3), no fracture occurred.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (12)
1. A high temperature pull-pull fatigue test system, comprising: a clamping device;
the clamping device includes: the first assembly and the second assembly are matched in pair and have the same structure; the first assembly comprises: a first swash block (2);
a first groove used for mounting a test sample (3) is formed in the clamping surface side of the first inclined block (2), the first groove is provided with an end side wall (211) and two opposite inclined side walls (212), two ends of the end side wall (211) are respectively connected to first ends of the two inclined side walls (212), and an end notch (213) opposite to the end side wall (211) is formed between second ends of the two inclined side walls (212);
the width of the end notches (213) is less than the width of the end side walls (211).
2. A high temperature pull-pull fatigue test system according to claim 1, wherein the first groove is an isosceles trapezoid groove (21), the two oblique side walls (212) are two waists, respectively, and the end side wall (211) and the end notch (213) are two bases, respectively.
3. A high temperature pull-pull fatigue test system according to claim 1, wherein the depth of the first groove is less than half the thickness of the test piece (3);
the second assembly comprises: a second swash block (7);
when the test sample (3) is arranged in the first grooves of the first inclined block (2) and the second inclined block (7), a gap (27) is formed between the first inclined block (2) and the second inclined block (7).
4. A high temperature pull-pull fatigue test system according to claim 3, wherein the depth of the first groove is 0.05mm to 0.25mm less than half the thickness of the test piece (3).
5. A high temperature pull-pull fatigue test system according to any of claims 1-4, wherein the first assembly further comprises: a first clamping block (1);
and a second groove matched with the first inclined block (2) in shape is formed in the clamping surface side of the first clamping block (1).
6. A high temperature pull-pull fatigue test system according to claim 5, wherein the first swash block (2) is T-shaped in shape and the second groove is a T-shaped groove (11).
7. A high-temperature pull-pull fatigue test system according to claim 5, wherein the first clamping block (1) is provided with a water through hole (12);
and/or a first clamping block fixing rod (13) and a second clamping block fixing rod (14) are respectively arranged on two sides of the first clamping block (1).
8. The high temperature pull-pull fatigue test system of claim 1, further comprising: the device comprises a high-temperature furnace, a thermocouple, a bracket (33), a bracket base (34) and a slide rail (35);
the outer wall of the high-temperature furnace is provided with a through hole for the thermocouple to pass through, the thermocouple is installed on the support (33), the support (33) is slidably installed on the sliding rail (35) through the support base (34), and the sliding rail (35) is parallel to the axial direction of the through hole.
9. The high temperature pull-pull fatigue test system of claim 1, further comprising: a high temperature furnace and a heat insulation blanket;
the heat insulation felt is arranged at a middle opening above the high-temperature furnace for the sample (3) to pass through.
10. The high temperature pull-pull fatigue test system of claim 9, wherein the material of the insulation blanket is an aerogel composite.
11. The high temperature pull-pull fatigue test system of claim 9, wherein the high temperature furnace comprises: a high temperature furnace left half (31) and a high temperature furnace right half (32);
the heat insulation felt comprises: a first heat insulation blanket (310) disposed on top of the high temperature furnace left half (31), and a second heat insulation blanket (320) disposed on top of the high temperature furnace right half (32);
rectangular openings are respectively formed in the centers of the opposite sides of the first heat insulation felt (310) and the second heat insulation felt (320) and form a rectangular passage (330) for the sample (3) to pass through together.
12. A high temperature pull-pull fatigue test method, characterized in that a high temperature pull-pull fatigue test system according to any one of claims 1 to 11 is used.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115791865A (en) * | 2022-12-25 | 2023-03-14 | 北京工业大学 | Ultra-high temperature loading device for fatigue test of weak-conductivity composite material heat engine |
| CN117433936A (en) * | 2023-12-19 | 2024-01-23 | 中航试金石检测科技(成都)有限公司 | Small sample low cycle fatigue testing device |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115791865A (en) * | 2022-12-25 | 2023-03-14 | 北京工业大学 | Ultra-high temperature loading device for fatigue test of weak-conductivity composite material heat engine |
| CN117433936A (en) * | 2023-12-19 | 2024-01-23 | 中航试金石检测科技(成都)有限公司 | Small sample low cycle fatigue testing device |
| CN117433936B (en) * | 2023-12-19 | 2024-04-05 | 中航试金石检测科技(成都)有限公司 | Small sample low cycle fatigue testing device |
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