Thermomechanical analyzer test fixture and method for measuring sample linear expansion coefficient

Abstract

The present invention discloses a test fixture for a thermomechanical analyzer, wherein a trapezoidal block is placed between two clamping blocks, and the left and right ends of the trapezoidal block are respectively placed in the trapezoidal grooves of the two left clamping blocks; during the sample testing process, the probe of the thermomechanical analyzer applies vertical forces to the trapezoidal block, and because the left and right end faces of the trapezoidal block are inclined surfaces, the trapezoidal block pushes the clamping blocks to the left and right sides, causing the sample to be tensioned; when the temperature rises and the sample expands, the clamping blocks are forced to move outward, and the trapezoidal block moves toward the sample in the vertical direction, and the probe moves toward the sample accordingly, and the probe displacement is detected and recorded. Using this test fixture for a thermomechanical analyzer, the displacement of the sample in the horizontal direction can be converted into the displacement of the probe in the vertical direction, and a set of probes and a sample carrier can be used to perform both tensile and compression tests on the sample, reducing equipment cost and replacement times. The present invention also discloses a method for measuring the linear expansion coefficient of a sample using this test fixture for a thermomechanical analyzer.

Description

Technical Field

[0001] The present invention relates to a thermal analysis test technology, in particular to a test fixture of a thermal mechanical analyzer and a method for measuring a linear expansion coefficient of a sample. Background Art

[0002] A thermal mechanical analyzer (TMA) is a device that measures the deformation of a material as a function of temperature and time under programmed temperature and non-vibration loads. It can measure parameters such as the thermal expansion coefficient and phase transition temperature of a material.

[0003] Commercial TMAs are equipped with different probes and stages to accommodate different testing scenarios. The probes and stages for measuring sample tension and compression are different, requiring a separate set to perform both tests, and they need to be replaced between tests. Furthermore, a single set of probes and stages is very expensive. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a thermomechanical analyzer test fixture and a method for measuring the linear expansion coefficient of a sample. A set of probes and a sample carrier can be used to perform both tensile and compression tests on the sample to be tested, reducing equipment costs and replacement times.

[0005] In order to solve the above technical problems, the present invention provides a thermomechanical analyzer test fixture, which includes two trapezoidal blocks, an upper trapezoidal block 11 and a lower trapezoidal block 12, and four clamping blocks, an upper left clamping block 21, an upper right clamping block 22, a lower left clamping block 23, and a lower right clamping block 24;

[0006] The left and right end surfaces of the upper trapezoidal block 11 are inclined surfaces, the left end surface of which is inclined to the right from top to bottom, and the right end surface of which is inclined to the left from top to bottom;

[0007] The left and right end surfaces of the lower trapezoidal block 12 are inclined surfaces, the left end surface of which is inclined to the left from top to bottom, and the right end surface of which is inclined to the right from top to bottom;

[0008] The left upper clamping block 21 is formed with a trapezoidal groove opening upward and rightward;

[0009] The upper right clamping block 22 is formed with a trapezoidal groove opening upward and leftward;

[0010] The left lower clamping block 23 is formed with a trapezoidal groove opening downward and rightward;

[0011] The right lower clamping block 24 is formed with a trapezoidal groove opening downward and leftward;

[0012] Each of the four clamping blocks is formed with an up-and-down through hole on the front and rear sides of the trapezoidal groove;

[0013] The trapezoidal grooves of the upper left clamping block 21 and the upper right clamping block 22 are adapted to the shapes of the left end and the right end of the upper trapezoidal block 11 respectively;

[0014] The trapezoidal grooves of the left lower clamping block 23 and the right lower clamping block 24 respectively match the shapes of the left end and the right end of the lower trapezoidal block 12;

[0015] The upper left clamping block 21 and the lower left clamping block 23 are assembled as a set and fixed by a fixing piece passing through the through hole, and are used to clamp the left end of the sample to be tested;

[0016] The upper right clamping block 22 and the lower right clamping block 24 form another set and are assembled and fixed by fixing members passing through the through holes to clamp the right end of the sample to be tested;

[0017] The upper trapezoidal block 11 is used to be placed between the upper left clamping block 21 and the upper right clamping block 22, with the left end of the upper trapezoidal block 11 placed in the trapezoidal groove of the upper left clamping block 21, and the right end of the upper trapezoidal block 11 placed in the trapezoidal groove of the upper right clamping block 22;

[0018] The lower trapezoidal block 12 is used to be placed between the lower left clamping block 23 and the lower right clamping block 24 , with the left end of the lower trapezoidal block 12 placed in the trapezoidal groove of the lower left clamping block 23 and the right end of the lower trapezoidal block 12 placed in the trapezoidal groove of the lower right clamping block 24 .

[0019] Preferably, the front and rear side surfaces of the upper trapezoidal block 11 and the lower trapezoidal block 12 are both vertical surfaces;

[0020] The front and rear walls of the trapezoidal grooves of the upper left clamping block 21, the upper right clamping block 22, the lower left clamping block 23, and the lower right clamping block 24 are all vertical surfaces;

[0021] The left wall of the trapezoidal groove of the upper left clamping block 21 and the lower left clamping block 23 is an inclined surface;

[0022] The right walls of the trapezoidal grooves of the upper right clamping block 22 and the lower right clamping block 24 are inclined surfaces.

[0023] Preferably, the upper trapezoidal block 11 and the lower trapezoidal block 12 have the same shape, and the inclination angles of the left and right end faces are the same;

[0024] The trapezoidal grooves of the upper left clamping block 21 , the upper right clamping block 22 , the lower left clamping block 23 and the lower right clamping block 24 have the same shape.

[0025] Preferably, the fastener is a bolt.

[0026] Preferably, the trapezoidal block and the clamping block are made of the same material.

[0027] Preferably, the thermal expansion coefficient of the material of the trapezoidal block and the clamping block is smaller than the thermal expansion coefficient of the material of the sample to be tested.

[0028] A method for measuring the linear expansion coefficient of a sample using the thermomechanical analyzer test fixture comprises the following steps:

[0029] S1. Thermomechanical analyzers use a probe and sample stage to measure compression.

[0030] S2. Place the sample to be tested and the fixture on the sample loading platform;

[0031] Fix the upper left clamping block 21 and the lower left clamping block 23 by passing the fixing piece through the through hole to clamp the left end of the sample to be tested;

[0032] Fix the upper right clamping block 22 and the lower right clamping block 24 by passing the fixing piece through the through hole to clamp the right end of the sample to be tested;

[0033] The upper trapezoidal block 11 is placed between the upper left clamping block 21 and the upper right clamping block 22, and the left and right ends of the upper trapezoidal block 11 are respectively placed in the trapezoidal grooves of the upper left and upper right clamping blocks, and the left and right end surfaces of the upper trapezoidal block 11 are respectively attached to the left wall of the trapezoidal groove of the upper left clamping block and the right wall of the trapezoidal groove of the upper right clamping block;

[0034] The lower trapezoidal block 12 is placed between the lower left clamping block 23 and the lower right clamping block 24, and the left and right ends of the lower trapezoidal block 12 are respectively placed in the trapezoidal grooves of the lower left and lower right clamping blocks, and the left and right end surfaces of the lower trapezoidal block 12 are respectively attached to the left wall of the trapezoidal groove of the lower left clamping block and the right wall of the trapezoidal groove of the lower right clamping block;

[0035] S3. At room temperature, the thermomechanical analyzer probe applies vertical force to the trapezoidal block. Because the left and right end surfaces of the trapezoidal block are inclined, the trapezoidal block pushes the clamping blocks to the left and right, tensioning the sample to be tested.

[0036] S4. The temperature is increased to expand the sample to be tested. The clamp is forced to move outward in the left and right directions. The trapezoidal block moves up and down toward the sample to be tested. The probe then moves toward the sample to be tested. The probe displacement is detected and recorded.

[0037] S5. Analyze and calculate the linear expansion coefficient of the sample.

[0038] Preferably, the trapezoidal block and the clamping block are made of the same material;

[0039] The upper trapezoidal block 11 and the lower trapezoidal block 12 have the same shape, and the inclination angles of the left and right end faces are the same;

[0040] The trapezoidal grooves of the upper left clamping block 21, the upper right clamping block 22, the lower left clamping block 23 and the lower right clamping block 24 have the same shape;

[0041] In step S5,

[0042] Where α is the linear expansion coefficient of the sample; L is the original length of the sample; ΔT is the temperature change; ΔH1 is the probe displacement; ω is the angle between the left and right end faces of the trapezoidal block and the long bottom face of the trapezoidal block; H0 is the height of the trapezoidal block; α His the linear expansion number of the trapezoidal block in the up and down directions; α L is the linear expansion coefficient of the trapezoidal block and the clamping block in the left and right directions.

[0043] Preferably, the materials used for the trapezoidal blocks and the clamping blocks are isotropic materials; L =α H =α0;

[0044]

[0045] Using this thermomechanical analyzer test fixture, the horizontal displacement of the sample to be tested can be converted into the vertical displacement of the probe of the thermomechanical analyzer. The probe and sample carrier used to measure compression can be used to measure the tension of the sample to be tested. Therefore, a set of probes and sample carriers can be used to perform both tension and compression tests on the sample to be tested, reducing equipment costs and replacement times. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0047] Figure 1 1 is a schematic diagram of the three-dimensional structure of an embodiment of a thermomechanical analyzer test fixture of the present invention;

[0048] Figure 2 1 is a schematic diagram of a vertical cross-sectional structure of an embodiment of a thermomechanical analyzer test fixture of the present invention;

[0049] Figure 3 FIG. 1 is a schematic diagram of the dimensions of an embodiment of a thermomechanical analyzer test fixture of the present invention.

[0050] Description of the accompanying drawings:

[0051] 11 upper trapezoidal block; 12 lower trapezoidal block; 21 upper left clamping block; 22 upper right clamping block; 23 lower left clamping block; 24 lower right clamping block; 3 sample; 4 through hole. DETAILED DESCRIPTION

[0052] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without creative work are within the scope of protection of the present invention.

[0053] The terms "first", "second" and similar words used in this application do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprises" and similar words mean that the elements or objects preceding the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right", "front", "back" and the like are only used to indicate relative position relationships. When the absolute position of the object being described changes, the relative position relationship may also change accordingly.

[0054] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features therein may be combined with each other.

[0055] Example 1

[0056] A thermomechanical analyzer test fixture, such as Figure 1 As shown, it includes two trapezoidal blocks, an upper trapezoidal block 11 and a lower trapezoidal block 12, and four clamping blocks, an upper left clamping block 21, an upper right clamping block 22, a lower left clamping block 23, and a lower right clamping block 24;

[0057] The left and right end surfaces of the upper trapezoidal block 11 are inclined surfaces, the left end surface of which is inclined to the right from top to bottom, and the right end surface of which is inclined to the left from top to bottom;

[0058] The left and right end surfaces of the lower trapezoidal block 12 are inclined surfaces, the left end surface of the lower trapezoidal block 12 is inclined to the left from top to bottom, and the right end surface of the lower trapezoidal block 12 is inclined to the right from top to bottom;

[0059] The upper left clamping block 21 is formed with a trapezoidal groove opening upward and rightward;

[0060] The upper right clamping block 22 is formed with a trapezoidal groove opening upward and leftward;

[0061] The left lower clamping block 23 is formed with a trapezoidal groove opening downward and rightward;

[0062] The right lower clamping block 24 is formed with a trapezoidal groove opening downward and leftward;

[0063] Each of the four clamping blocks has a vertical through hole 4 formed on the front and rear sides of its trapezoidal groove;

[0064] The trapezoidal grooves of the upper left clamping block 21 and the upper right clamping block 22 are adapted to the shapes of the left and right ends of the upper trapezoidal block 11 respectively (the left end surface of the upper trapezoidal block 11 is parallel to the left wall of the trapezoidal groove of the upper left clamping block 21, and the right end surface of the upper trapezoidal block 11 is parallel to the right wall of the trapezoidal groove of the upper right clamping block 22);

[0065] The trapezoidal grooves of the left lower clamping block 23 and the right lower clamping block 24 are adapted to the shapes of the left and right ends of the lower trapezoidal block 12, respectively (the left end surface of the lower trapezoidal block 12 is parallel to the left wall of the trapezoidal groove of the left lower clamping block 23, and the right end surface of the lower trapezoidal block 12 is parallel to the right wall of the trapezoidal groove of the right lower clamping block 24);

[0066] The upper left clamping block 21 and the lower left clamping block 23 are assembled as a set and fixed by a fixing member passing through the through hole 4 to clamp the left end of the sample 3 to be tested;

[0067] The upper right clamping block 22 and the lower right clamping block 24 form another set and are assembled and fixed through the through hole 4 by a fixing member to clamp the right end of the sample 3 to be tested;

[0068] The upper trapezoidal block 11 is used to be placed between the upper left clamping block 21 and the upper right clamping block 22, with the left end of the upper trapezoidal block 11 placed in the trapezoidal groove of the upper left clamping block 21, and the right end of the upper trapezoidal block 11 placed in the trapezoidal groove of the upper right clamping block 22;

[0069] The lower trapezoidal block 12 is used to be placed between the lower left clamping block 23 and the lower right clamping block 24 , with the left end of the lower trapezoidal block 12 placed in the trapezoidal groove of the lower left clamping block 23 and the right end of the lower trapezoidal block 12 placed in the trapezoidal groove of the lower right clamping block 24 .

[0070] During the test of sample 3, the probe of the thermomechanical analyzer applies vertical force to the trapezoidal block. Because the left and right end faces of the trapezoidal block are inclined, the trapezoidal block pushes the clamping blocks to the left and right sides, causing the sample 3 to be tensioned.

[0071] When the temperature rises and the sample 3 to be tested expands, the clamping block is forced to move outward, and the trapezoidal block moves toward the sample 3 to be tested in the up and down directions. The probe then moves toward the sample 3 to be tested, and the probe displacement is detected and recorded.

[0072] By using this thermomechanical analyzer test fixture, the horizontal displacement of the sample 3 to be tested can be converted into the vertical displacement of the probe of the thermomechanical analyzer. The probe and sample carrier used to measure compression can be used to measure the tension of the sample 3 to be tested. Therefore, a set of probes and sample carriers can be used to perform both tension and compression tests on the sample 3 to be tested, reducing equipment costs and replacement times.

[0073] Example 2

[0074] Based on the thermomechanical analyzer test fixture of the first embodiment, the front and rear side surfaces of the upper trapezoidal block 11 and the lower trapezoidal block 12 are both vertical surfaces;

[0075] The front and rear walls of the trapezoidal grooves of the upper left clamping block 21, the upper right clamping block 22, the lower left clamping block 23, and the lower right clamping block 24 are all vertical surfaces;

[0076] The left wall of the trapezoidal groove of the upper left clamping block 21 and the lower left clamping block 23 is an inclined surface;

[0077] The right walls of the trapezoidal grooves of the upper right clamping block 22 and the lower right clamping block 24 are inclined surfaces.

[0078] Preferably, the upper trapezoidal block 11 and the lower trapezoidal block 12 have the same shape, and the inclination angles of the left and right end faces are the same;

[0079] The trapezoidal grooves of the upper left clamping block 21 , the upper right clamping block 22 , the lower left clamping block 23 and the lower right clamping block 24 have the same shape.

[0080] Preferably, the fastener is a bolt.

[0081] Example 3

[0082] Based on the test fixture of the thermomechanical analyzer in Example 1, the trapezoidal block and the clamping block are made of the same material.

[0083] Preferably, the thermal expansion coefficient of the material of the trapezoidal block and the clamping block is smaller than the thermal expansion coefficient of the material of the sample 3 to be tested.

[0084] Example 4

[0085] like Figure 2 As shown, the method for measuring the linear expansion coefficient of a sample using the thermomechanical analyzer test fixture of embodiments one to three includes the following steps:

[0086] S1. Thermomechanical analyzers use a probe and sample stage to measure compression.

[0087] S2. Place the sample 3 and the fixture on the sample loading platform;

[0088] Pass the fixing piece through the through hole 4 to assemble and fix the upper left clamping block 21 and the lower left clamping block 23 to clamp the left end of the sample 3 to be tested;

[0089] The upper right clamping block 22 and the lower right clamping block 24 are assembled and fixed by a fixing piece passing through the through hole 4 to clamp the right end of the sample 3 to be tested;

[0090] The upper trapezoidal block 11 is placed between the upper left clamping block 21 and the upper right clamping block 22, and the left and right ends of the upper trapezoidal block 11 are respectively placed in the trapezoidal grooves of the upper left and upper right clamping blocks, and the left and right end surfaces of the upper trapezoidal block 11 are respectively attached to the left wall of the trapezoidal groove of the upper left clamping block and the right wall of the trapezoidal groove of the upper right clamping block;

[0091] The lower trapezoidal block 12 is placed between the lower left clamping block 23 and the lower right clamping block 24, and the left and right ends of the lower trapezoidal block 12 are respectively placed in the trapezoidal grooves of the lower left and lower right clamping blocks, and the left and right end surfaces of the lower trapezoidal block 12 are respectively attached to the left wall of the trapezoidal groove of the lower left clamping block and the right wall of the trapezoidal groove of the lower right clamping block;

[0092] S3. At room temperature, the probe of the thermomechanical analyzer applies vertical force to the trapezoidal block. Because the left and right end faces of the trapezoidal block are inclined, the trapezoidal block pushes the clamping block to the left and right sides, tensioning the sample 3 to be tested.

[0093] S4. Raising the temperature causes the sample to be tested 3 to expand, the clamp is forced to move outward along the left and right directions, the trapezoidal block moves in the up and down directions toward the sample to be tested 3, and the probe then moves toward the sample to be tested 3. The probe displacement is detected and recorded;

[0094] S5. Analyze and calculate the linear expansion coefficient of the sample.

[0095] Preferably, the trapezoidal block and the clamping block are made of the same material;

[0096] The upper trapezoidal block 11 and the lower trapezoidal block 12 have the same shape, and the inclination angles of the left and right end faces are the same;

[0097] Better, such as Figure 2 、 Figure 3 As shown, the trapezoidal grooves of the upper left clamping block 21, the upper right clamping block 22, the lower left clamping block 23 and the lower right clamping block 24 have the same shape;

[0098]

[0099] Among them, α is the linear expansion coefficient of the sample, which is to be determined; ΔL is the change in sample length, which is an unknown quantity; L is the original length of the sample, which is a known quantity; ΔT is the temperature change, which is a known quantity; ΔL1 is the length of the sample extrapolated by the probe pressing down the trapezoidal block, which is an unknown quantity; ΔL2 is the length of the sample extrapolated by the expansion of the trapezoidal block in the vertical direction, which is an unknown quantity; ΔL3 is the length of the sample extrapolated by the expansion of the trapezoidal block and the clamp in the left and right directions, which is an unknown quantity; ΔH1 is the probe displacement, which is a test quantity; ω is the angle between the left and right end faces of the trapezoidal block and the long bottom face of the trapezoidal block, which is a known quantity; H0 is the height of the trapezoidal block, which is a known quantity; ΔH0 is the change in the height of the trapezoidal block, which is an unknown quantity; L0 is the original length of the trapezoidal block placed between the clamps, which is an unknown quantity; α H is the linear expansion coefficient of the trapezoidal block in the vertical direction, a known quantity; α L is the linear expansion coefficient of the trapezoidal block and the clamping block in the left and right directions, a known quantity.

[0100] Under ideal conditions, if the thermal expansion coefficient of the materials used for the trapezoidal blocks and clamping blocks is 0, the above formula can be simplified to:

[0101]

[0102] In fact, the thermal expansion coefficient of the materials used for the trapezoidal blocks and clamps cannot be 0, and L0≈L, the above formula can be simplified to

[0103]

[0104] It can be seen that the quantity to be determined α is uniquely determined by the test quantity ΔH1. If the materials used for the trapezoidal block and the clamping block are isotropic materials, then α L =α H =α0, the above formula can be simplified to:

[0105]

[0106] In Example 4, a method for measuring the linear expansion coefficient of a sample is described. A thermomechanical analyzer uses a compression-measuring probe and a sample stage. Sample 3 and a fixture are placed on the stage and tested according to the method for measuring sample compression. The horizontal displacement of the sample is converted into the vertical displacement of the thermomechanical analyzer's compression-measuring probe. The compression-measuring probe and the sample stage are then used to measure the sample's tensile strength, thereby achieving the measurement of the sample's linear expansion coefficient. Furthermore, this method for measuring the sample's linear expansion coefficient takes into account the thermal expansion coefficient of the fixture material, resulting in more accurate test results.

[0107] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A thermomechanical analyzer test fixture, characterized in that: It comprises two trapezoidal blocks, an upper trapezoidal block (11) and a lower trapezoidal block (12), and four clamping blocks, an upper left clamping block (21), an upper right clamping block (22), a lower left clamping block (23), and a lower right clamping block (24); The left and right end surfaces of the upper trapezoidal block (11) are inclined surfaces, the left end surface of the upper trapezoidal block (11) is inclined to the right from top to bottom, and the right end surface of the upper trapezoidal block (11) is inclined to the left from top to bottom; The left and right end surfaces of the lower trapezoidal block (12) are inclined surfaces, the left end surface of the lower trapezoidal block (12) is inclined to the left from top to bottom, and the right end surface of the lower trapezoidal block (12) is inclined to the right from top to bottom; The left upper clamping block (21) is formed with a trapezoidal groove opening upward and rightward; The upper right clamping block (22) is formed with a trapezoidal groove opening upward and leftward; The left lower clamping block (23) is formed with a trapezoidal groove opening downward and rightward; The right lower clamping block (24) is formed with a trapezoidal groove opening downward and leftward; Each of the four clamping blocks is formed with a vertical through hole (4) on the front and rear sides of the trapezoidal groove; The trapezoidal grooves of the upper left clamping block (21) and the upper right clamping block (22) are respectively adapted to the shapes of the left end portion and the right end portion of the upper trapezoidal block (11); The trapezoidal grooves of the left lower clamping block (23) and the right lower clamping block (24) are respectively adapted to the shapes of the left end portion and the right end portion of the lower trapezoidal block (12); The upper left clamping block (21) and the lower left clamping block (23) are assembled as a group and fixed by a fixing member passing through the through hole (4) to clamp the left end of the sample to be tested (3); The upper right clamping block (22) and the lower right clamping block (24) are another set, which are assembled and fixed by a fixing member passing through the through hole (4) and are used to clamp the right end of the sample to be tested (3); The upper trapezoidal block (11) is used to be placed between the upper left clamping block (21) and the upper right clamping block (22), with the left end of the upper trapezoidal block (11) placed in the trapezoidal groove of the upper left clamping block (21), and the right end of the upper trapezoidal block (11) placed in the trapezoidal groove of the upper right clamping block (22); The lower trapezoidal block (12) is used to be placed between the lower left clamping block (23) and the lower right clamping block (24), the left end of the lower trapezoidal block (12) is placed in the trapezoidal groove of the lower left clamping block (23), and the right end of the lower trapezoidal block (12) is placed in the trapezoidal groove of the lower right clamping block (24).

2. The thermomechanical analyzer test fixture according to claim 1, characterized in that: The front and rear side surfaces of the upper trapezoidal block (11) and the lower trapezoidal block (12) are both vertical surfaces; The front and rear walls of the trapezoidal grooves of the upper left clamping block (21), the upper right clamping block (22), the lower left clamping block (23), and the lower right clamping block (24) are all vertical surfaces; The left walls of the trapezoidal grooves of the upper left clamping block (21) and the lower left clamping block (23) are inclined surfaces; The right walls of the trapezoidal grooves of the upper right clamping block (22) and the lower right clamping block (24) are inclined surfaces.

3. The thermomechanical analyzer test fixture according to claim 1, characterized in that: The upper trapezoidal block (11) and the lower trapezoidal block (12) have the same shape, and the inclination angles of the left and right end faces are the same; The trapezoidal grooves of the upper left clamping block (21), the upper right clamping block (22), the lower left clamping block (23) and the lower right clamping block (24) are of the same shape.

4. The thermomechanical analyzer test fixture according to claim 1, characterized in that: The fixing member is a bolt.

5. The thermomechanical analyzer test fixture according to claim 1, characterized in that: The trapezoidal blocks and the clamping blocks are made of the same material.

6. The thermomechanical analyzer test fixture according to claim 1, characterized in that: The thermal expansion coefficient of the materials of the trapezoidal block and the clamping block is smaller than the thermal expansion coefficient of the material of the sample to be tested (3).

7. A method for measuring the linear expansion coefficient of a sample using the thermomechanical analyzer test fixture according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1. Thermomechanical analyzers use a probe and sample stage to measure compression. S2. Place the sample to be tested (3) and the fixture on the sample carrier; The upper left clamping block (21) and the lower left clamping block (23) are assembled and fixed by a fixing member passing through the through hole (4) to clamp the left end portion of the sample to be tested (3); A fixing member is passed through the through hole (4) to assemble and fix the upper right clamping block (22) and the lower right clamping block (24) to clamp the right end of the sample to be tested (3); The upper trapezoidal block (11) is placed between the upper left clamping block (21) and the upper right clamping block (22), the left and right ends of the upper trapezoidal block (11) are respectively placed in the trapezoidal grooves of the upper left and upper right clamping blocks, and the left and right end surfaces of the upper trapezoidal block (11) are respectively attached to the left wall of the trapezoidal groove of the upper left clamping block and the right wall of the trapezoidal groove of the upper right clamping block; The lower trapezoidal block (12) is placed between the lower left clamping block (23) and the lower right clamping block (24), the left and right ends of the lower trapezoidal block (12) are respectively placed in the trapezoidal grooves of the lower left and lower right clamping blocks, and the left and right end surfaces of the lower trapezoidal block (12) are respectively attached to the left wall of the trapezoidal groove of the lower left clamping block and the right wall of the trapezoidal groove of the lower right clamping block; S3. At room temperature, the probe of the thermomechanical analyzer applies a force in the vertical direction to the trapezoidal block. Because the left and right end faces of the trapezoidal block are inclined, the trapezoidal block pushes the clamping block to the left and right sides, so that the sample to be tested (3) is tensioned; S4. The temperature is increased to expand the sample to be tested (3), the clamp is forced to move outward along the left and right directions, the trapezoidal block moves in the up and down directions toward the sample to be tested (3), and the probe moves toward the sample to be tested (3), and the probe displacement is detected and recorded; S5. Analyze and calculate the linear expansion coefficient of the sample.

8. The method for measuring the linear expansion coefficient of a sample according to claim 7, wherein: The trapezoidal blocks and clamping blocks are made of the same material; The upper trapezoidal block (11) and the lower trapezoidal block (12) have the same shape, and the inclination angles of the left and right end faces are the same; The trapezoidal grooves of the upper left clamping block (21), the upper right clamping block (22), the lower left clamping block (23) and the lower right clamping block (24) are of the same shape; In step S5, Where α is the linear expansion coefficient of the sample; L is the original length of the sample; ΔT is the temperature change; ΔH1 is the probe displacement; ω is the angle between the left and right end faces of the trapezoidal block and the long bottom face of the trapezoidal block; H0 is the height of the trapezoidal block; α H is the linear expansion number of the trapezoidal block in the up and down directions; α L is the linear expansion coefficient of the trapezoidal block and the clamping block in the left and right directions.

9. The method for measuring the linear expansion coefficient of a sample according to claim 8, wherein: The materials used for the trapezoidal blocks and clamping blocks are isotropic materials; α L =α H =α0;

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