A linear expansion coefficient measurement system and measurement method thereof

Abstract

The present invention discloses a linear expansion coefficient measurement system and method, comprising an insulating box, a fringe interference detection mechanism, and an optical measurement subsystem. Three fixed support plates are provided in the insulating box, and a parallel sliding support plate is provided on the opposite side of each fixed support plate. The three sliding support plates are connected to the fringe interference detection mechanism via X, Y, and Z axis measurement transmission mechanisms, respectively. A PTC heating plate and several temperature sensors are provided in the insulating box, and a semiconductor cooling plate is provided on the insulating box. In view of the diversity of the parts to be tested, the present invention adopts a transmission coordination design of a sliding plate, a measurement transmission mechanism, and a fringe interference detection mechanism. Special processing of the shape of the parts to be tested is not required, the types of materials that can be measured are expanded, and the linear expansion coefficient of the material to be tested in three directions can be measured. The present invention utilizes a light intensity curve method to determine the fringe boundary and a pixel calibration method to measure the fringe width, which greatly improves the measurement accuracy of the fringe width.

Description

Technical Field

[0001] The present invention relates to the field of linear expansion measurement, and in particular to a linear expansion coefficient measurement system and a measurement method thereof. Background Art

[0002] Thermal expansion is the phenomenon in which a material expands in volume or length as temperature increases. This phenomenon is typically characterized by the coefficient of thermal expansion (CTE). With the continuous advancement of industrial technology, the CTE of materials is becoming increasingly important in fields such as aerospace, optical cold processing, and EUV lithography, impacting the stable operation of systems under complex temperature conditions.

[0003] At present, the most commonly used method for measuring the thermal expansion coefficient is to use the ZKY-XP metal linear expansion coefficient measuring instrument. The metal linear expansion coefficient measuring instrument includes a metal linear expansion tester and an open PID temperature control tester. The metal linear expansion tester requires the material to be tested to be made into a hollow metal rod. One end of the hollow metal rod is fixed, and the other end is slidably installed through a bearing. The hollow metal rod can freely extend at the sliding end. The hollow metal rod is provided with a water inlet and a water outlet. Hot water is added through the water inlet, and the metal is heated by the water flowing through the hollow metal rod. Finally, the expansion of the metal is measured with a micrometer. Observe the reading of the micrometer during use. The required physical quantities can be observed through the combination of the PID temperature control tester and the metal linear expansion tester, and the relevant linear expansion coefficient can be obtained by calculation. However, the metal linear expansion coefficient measuring instrument has the following disadvantages:

[0004] 1. The hollow metal rod cools down slowly, and it takes a long time for the instrument to return to room temperature after the temperature is raised. For example, the temperature of the copper rod drops from 60.1°C to 30.8°C in 96 minutes. The slow cooling speed is not conducive to the continuous repeated use of the instrument.

[0005] 2. Although the metal linear expansion coefficient measuring instrument has the function of heating the material to be tested, it cannot cool it, so it can only measure the thermal expansion coefficient of the material, but cannot measure the contraction coefficient of the material.

[0006] 3. The metal linear expansion coefficient measuring instrument uses a micrometer to measure the tiny deformation of the material. The measurement results are related to its manufacturing process, material and other factors, and are easily affected by the ambient temperature and humidity, and the stability of the micrometer fixation. In addition, the micrometer measuring rod must be perpendicular to the surface of the workpiece being measured, otherwise errors will occur and the measurement data will be greatly affected by the outside world. Summary of the Invention

[0007] In view of the above-mentioned deficiencies in the prior art, the present invention provides a linear expansion coefficient measurement system and a measurement method thereof.

[0008] In order to achieve the above-mentioned purpose of the invention, the technical solution adopted by the present invention is: it includes an insulating box, a fringe interference detection mechanism and an optical measurement subsystem, three fixed support plates are arranged in the insulating box, and the three fixed support plates are connected to each other perpendicularly to form a corner structure, and a parallel sliding support plate is arranged on the opposite side of each fixed support plate, and the three sliding support plates are connected to the fringe interference detection mechanism through an X-axis measurement transmission mechanism, a Y-axis measurement transmission mechanism, and a Z-axis measurement transmission mechanism respectively; a PTC heating plate and several temperature sensors are arranged in the insulating box, and a semiconductor cooling plate is arranged on the insulating box, and the PTC heating plate, the semiconductor cooling plate, and the several temperature sensors are electrically connected to the temperature control subsystem.

[0009] Furthermore, the optical measurement subsystem includes a half-reflecting half-mirror, a reading microscope, a camera, a laptop computer, a beam expander, a first polarizer, a second polarizer and a helium-neon laser; the laptop computer is connected to the camera, the second polarizer, the reading microscope and the camera are sequentially located in the laser emission direction of the half-reflecting half-mirror, the helium-neon laser, the beam expander and the first polarizer are sequentially located in the laser incident direction of the half-reflecting half-mirror, the laser emission direction forms an angle of 45° with the half-reflecting half-mirror, the laser incident direction forms an angle of 135° with the half-reflecting half-mirror, and the laser emission direction is perpendicular to the laser incident direction.

[0010] Furthermore, the X-axis measurement transmission mechanism includes an X-axis transfer rod, one end of which is fixedly connected to the corresponding sliding support plate, and the other end is magnetically connected to the fringe interference detection mechanism; a circular through hole for installing the X-axis transfer rod is provided on the insulation box.

[0011] Furthermore, the Y-axis measurement transmission mechanism has the same structure as the Z-axis measurement transmission mechanism. The Z-axis measurement transmission mechanism includes a telescopic sleeve installed on the edge of the insulation box, a telescopic rod is arranged inside the telescopic sleeve, a rotating drum shaft is arranged at the protruding end of the telescopic rod, a rotating drum is arranged on the rotating drum shaft, and two L-shaped transmission rods are fixed on the rotating drum, one L-shaped transmission rod is connected to the corresponding sliding support plate, and one sliding support plate is magnetically connected to the fringe interference detection mechanism.

[0012] Furthermore, the L-shaped transfer rod includes a connecting section with the rotating drum and a bent end connected to the fringe interference detection mechanism, and a horizontal bubble is provided on the connecting section; a threaded through hole is provided on the telescopic sleeve, and a locking pin for fastening the telescopic rod is provided on the threaded through hole; and a strip through hole is provided on the insulation box to cooperate with the L-shaped transfer rod.

[0013] Furthermore, the fringe interference detection mechanism includes a first interference plate, a second interference plate and a mounting base with identical structures. The first interference plate and the second interference plate are both provided with polarizer mounting holes. A first glass slide is provided in the polarizer mounting hole of the first interference plate, and a second glass slide is provided in the polarizer mounting hole of the second interference plate. A rotating shaft is provided on one side of the bottom of the first interference plate, a supporting wheel is provided on the other side of the bottom of the first interference plate, and a magnetic portion is provided on the first interference plate. A mounting through hole cooperating with the rotating shaft is provided on the mounting base, and a thrust bearing cooperating with the mounting base is also provided on the rotating shaft.

[0014] Furthermore, the second interference plate is also magnetically connected to a fine-tuning rod, which includes a support column fixed on the mounting base, a transverse sleeve provided on the support column, an adjustment rod connected to the inner thread of the transverse sleeve, one end of the adjustment rod is magnetically connected to the second interference plate, and the other end of the adjustment rod is provided with an adjustment knob.

[0015] The measurement method of the three-dimensional linear expansion coefficient measurement system includes the following steps:

[0016] S1: Measure the initial length L0 and initial temperature T0 of the material to be tested, and set the material experimental temperature T;

[0017] S2: Before the experiment begins, connect the measurement transmission mechanism to the fringe interference detection mechanism, and adjust the second glass slide on the second interference plate to be parallel to the first wave plate on the first interference plate;

[0018] S3: Adjust the reading microscope and calculate the actual distance Δ between two pixels using the pixel distance of the crosshairs of the reading microscope and the actual distance;

[0019] S4: Perform an expansion deformation measurement experiment, start the temperature control subsystem, control the temperature in the insulation box to reach the material experimental temperature T, and after the temperature in the insulation box reaches the material experimental temperature T, take a screenshot of the interference fringes displayed on the laptop to obtain the interference pattern;

[0020] S5: Rotate the interference pattern to an angle of about 45 degrees with the horizontal; select the i-th row of data, obtain the pixel values ​​m1 and m2 corresponding to the peak of the light intensity distribution fitting curve, and the number of peaks K, and calculate the horizontal spacing a:

[0021]

[0022] Where Δ is the actual distance between two adjacent pixels;

[0023] S6: Select the jth column of data to obtain the pixel values ​​n1 and n2 corresponding to the peak of the light intensity distribution fitting curve, as well as the number of peaks L, and calculate the vertical spacing b using the actual distance Δ:

[0024]

[0025] Where Δ is the actual distance between two adjacent pixels;

[0026] S7: Calculate the spacing of the interference fringes:

[0027]

[0028] Where a is the horizontal spacing between adjacent stripes, and b is the vertical spacing between adjacent stripes.

[0029] S8: Calculate the deformation of the material:

[0030]

[0031] Where, is the wavelength of the incident laser, is the distance from the contact point between the transmission rod and frame A to the center of the rotating shaft of frame A, and e is the interference fringe spacing;

[0032] S9: Calculate the linear expansion coefficient of the material to be tested;

[0033] Change the material temperature and repeat steps S1 to S8 for multiple measurements. Use the least squares method to calculate the ratio of the material deformation D to the temperature change (T-T0) and the linear expansion coefficient of the material:

[0034]

[0035] Where D is the material deformation, L0 is the initial length of the material, T0 is the initial temperature of the material, and T is the temperature after the material changes.

[0036] Furthermore, step S2 specifically includes the following steps:

[0037] S21: Adjust the first interference plate to be magnetically connected to the transmission rod; adjust the second interference plate to be parallel to the first interference plate, and adjust the second interference plate to be magnetically connected to the fine-tuning rod;

[0038] S22: Turn on the HeNe laser and adjust the reading microscope until the crosshairs are visible. Adjust the distance between the reading microscope and the second interference plate until clear interference fringes are visible.

[0039] S23: Adjust the angle between the second interferometer plate and the first interferometer plate by turning the adjustment knob on the fine-tuning rod. When the fringe width is observed to increase, continue to turn the adjustment knob in this direction until the fringe just disappears. At this time, the second glass slide on the second interferometer plate is parallel to the first wave plate on the first interferometer plate.

[0040] Furthermore, step S2 specifically includes the following steps:

[0041] S31: Rotate the drum of the reading microscope so that the crosshairs are at position A, record the drum reading L1 at this time, and display and capture the image on the laptop via the CCD sensor;

[0042] S32: Continue to rotate the drum of the reading microscope until the crosshairs are at position B, record the drum reading L2 at this time, and display and capture the image CCD sensor on the laptop;

[0043] S33: performing image processing on the crosshairs to obtain pixel values ​​N1 and N2 corresponding to the i-th row when the crosshairs are translated from position A to position B;

[0044] S34: Calculate the actual distance Δ between the two pixels:

[0045]

[0046] The beneficial effects of the present invention are:

[0047] The present invention addresses the technical difficulties of slow natural cooling and one-way measurement. It uses semiconductor refrigeration plates for cooling and PTC heating plates for heating, and utilizes PLC heating plates to integrate the instrument's heating and cooling systems, thus achieving rapid cooling and two-way measurement functions.

[0048] In view of the diversity of the test pieces, the present invention adopts the design of "sliding plate + measurement transmission mechanism + fringe interference detection mechanism", which does not require special processing of the shape of the test piece, expands the types of testable materials, and can realize the measurement of the linear expansion coefficient of the test material in three directions.

[0049] To address the technical difficulties of small measurement range and overlapping interference fringes of wedge interferometry, the present invention adopts two independent designs of two separate parallel interference plates and light polarization selection, which improves the deformation measurement range of laser wedge interferometry and solves the technical problem of overlapping interference fringes.

[0050] The present invention addresses the technical difficulties of blurred stripe boundaries and low stripe width measurement accuracy by proposing a method of determining stripe boundaries using a light intensity curve method and measuring stripe width using a pixel calibration method, thereby greatly improving the measurement accuracy of stripe width.

[0051] The present invention can realize low-temperature and high-temperature linear expansion measurement through the combination of temperature control subsystem, semiconductor cooling sheet, PTC heating sheet and temperature sensor, and has the characteristics of bidirectional measurement. Compared with the existing metal linear expansion coefficient measuring instrument, it is more practical; at the same time, the combination of PTC heating sheet and semiconductor cooling sheet can make the temperature of the material to be tested quickly return to normal temperature, which is convenient for continuous experimental measurement.

[0052] The X-axis measurement transmission mechanism, Y-axis measurement transmission mechanism, and Z-axis measurement transmission mechanism of the present invention can transmit the expansion amount of the material to be tested in the X, Y, and Z directions to the fringe interference detection mechanism. By driving the first interference plate and first glass slide of the fringe interference detection mechanism to move, the optical measurement subsystem is used to measure the fringe spacing, which is conducive to obtaining the linear expansion coefficient.

[0053] The X-axis measurement transmission mechanism, Y-axis measurement transmission mechanism, and Z-axis measurement transmission mechanism of the present invention can cooperate with the fringe interference detection mechanism to respectively measure the expansion amounts of the material to be detected in the X, Y, and Z directions. It is only necessary to disconnect the magnetic connection between the X-axis measurement transmission mechanism, Y-axis measurement transmission mechanism, and Z-axis measurement transmission mechanism and the fringe interference detection mechanism, and switching the measurement direction is convenient.

[0054] The Y-axis measurement transmission mechanism and the Z-axis measurement transmission mechanism of the present invention both include a telescopic sleeve, a telescopic rod, a rotating cylinder shaft, an L-shaped transmission rod, a rotating cylinder, a locking pin and a level bubble. The telescopic rod can be telescoped within the telescopic sleeve to adapt to the volume change of the material to be tested, and the locking pin can fix the telescopic rod after telescoped; the L-shaped transmission rod is used to transmit the expansion displacement in the Y-axis and Z-axis directions, which is convenient for the fringe interference detection mechanism and the optical measurement subsystem to measure; the rotating cylinder shaft and the rotating cylinder cooperate to enable the L-shaped transmission rod to rotate smoothly and transmit the expansion displacement of the material to be tested in the Y-axis and Z-axis directions; the level bubble facilitates the adjustment of the horizontal working end of the L-shaped transmission rod to a horizontal level, which is convenient for subsequent measurement experiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0056] Figure 2 A fringe interference detection mechanism for a thermal insulation box and a fringe interference detection mechanism;

[0057] Figure 3 It is a structural diagram of the Z-axis measurement transmission mechanism;

[0058] Figure 4 Schematic diagram of the structure of the fringe interference detection mechanism Figure 1 ;

[0059] Figure 5 Schematic diagram of the structure of the fringe interference detection mechanism Figure 2 ;

[0060] Figure 6 Schematic diagram of the connection between the transmission mechanism and the fringe interference detection mechanism;

[0061] Figure 7 This is the principle diagram of pixel calibration method;

[0062] Figure 8This is the grayscale principle diagram of the light intensity curve method;

[0063] Figure 9 It is the light intensity distribution curve diagram of the light intensity curve method;

[0064] Figure 10 It is the fitting curve diagram of the light intensity curve method;

[0065] Figure 11 The calculation principle diagram of the stripe spacing;

[0066] Figure 12 The schematic diagram of the inclined stripes;

[0067] The symbols of the components are as follows:

[0068] 1. Insulation box; 2. Temperature control subsystem; 3. Semiconductor cooling plate; 4. PTC heating plate;

[0069] 10. Temperature sensor; 11. Fixed support plate; 12. Sliding support plate; 13. Material to be tested; 14. X-axis transfer rod;

[0070] 71. Telescopic sleeve; 72. Telescopic rod; 73. Rotating cylinder shaft; 74. L-shaped transmission rod; 75. Rotating cylinder; 76. Locking pin; 77. Level bubble;

[0071] 8. Fringe interference detection mechanism; 81. First interference plate; 82. Second interference plate; 83. First glass slide; 84. Second glass slide; 85. Polarizer mounting hole; 86. Rotating shaft; 87. Support wheel; 88. Magnetic attraction unit; 89. Fine-tuning lever; 80. Mounting base;

[0072] 9. Optical measurement subsystem; 91. Half-reflecting half-mirror lens; 92. Camera; 93. Reading microscope; 94. Beam expander; 95. Helium-neon laser; 96. First polarizer; 97. Second polarizer; 98. Laptop computer;

[0073] 891. Support column; 892. Horizontal sleeve; 893. Adjustment rod; 894. Adjustment knob. DETAILED DESCRIPTION

[0074] The specific embodiments of the present invention are described below to facilitate understanding of the present invention by those skilled in the art. However, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the appended claims, these changes are obvious, and all inventions and creations utilizing the concepts of the present invention are protected.

[0075] like Figure 1As shown, the optical measurement subsystem 9 includes a half-reflecting half-mirror 91, a reading microscope 93, a camera 92, a second polarizer 96, a laptop computer 98, a beam expander 94, a first polarizer 96, a second polarizer 7 and a helium-neon laser 95; the laptop computer 98 is connected to the camera 92, the second polarizer 97, the reading microscope 93 and the camera 92 are sequentially located in the laser emission direction of the half-reflecting half-mirror 91, the helium-neon laser 95, the beam expander 94 and the first polarizer 96 are sequentially located in the laser incident direction of the half-reflecting half-mirror 91, the laser emission direction and the half-reflecting half-mirror 91 form an angle of 45°, and the laser emission direction refers to the reflected light 1, reflected light 2, reflected light 3 and reflected light 4 reflected from the half-reflecting half-mirror 91 to the first polarizer 96; the laser incident direction and the half-reflecting half-mirror 91 form an angle of 135°, and the laser emission direction is perpendicular to the laser incident direction 7. As shown Figure 2 As shown, a first polarizer 96 is placed between a He-Ne laser 95 and a half-mirror lens 91, and a second polarizer 97 is placed between a reading microscope 93 and the half-mirror lens 91. The polarization direction of the first polarizer is placed at a 45-degree angle with the positive x-axis, while the polarization direction of the second polarizer 97 is placed at a 135-degree angle with the positive x-axis. The first reflected light, with its polarization direction at a 45-degree angle with the positive x-axis, is blocked by the second polarizer 97. The polarization direction of reflected light 2 is at a 135-degree angle with the positive x-axis and passes smoothly through the second polarizer 97. Reflected light 3 has the same polarization direction as reflected light 2 and passes through the second polarizer 97. Reflected light 4, with its polarization direction at a 45-degree angle with the positive x-axis, is blocked by the second polarizer 97. This allows only light rays 2 and 3 to enter the reading microscope 93, i.e., only the light reflected from the lower and upper surfaces of the air wedge sandwiched between the two wave plates, resulting in a single set of interference fringes.

[0076] like Figure 2As shown, the linear expansion coefficient measurement system includes an insulating box 1, a fringe interference detection mechanism 8 and an optical measurement subsystem 9. Three fixed support plates 11 are provided in the insulating box 1. The three fixed support plates 11 are connected to each other perpendicularly to form a corner structure. A parallel sliding support plate 12 is provided on the opposite side of each fixed support plate 11. The three sliding support plates 12 are connected to the fringe interference detection mechanism 8 through an X-axis measurement transmission mechanism, a Y-axis measurement transmission mechanism, and a Z-axis measurement transmission mechanism respectively; the X-axis measurement transmission mechanism, the Y-axis measurement transmission mechanism, and the Z-axis measurement transmission mechanism can realize the linear expansion measurement of the material to be detected in the three-dimensional direction. The X-axis measurement transmission mechanism, the Y-axis measurement transmission mechanism, and the Z-axis measurement transmission mechanism are connected to the fringe interference detection mechanism 8 by magnetic connection, which is convenient for switching to perform linear expansion measurement of the material to be detected in the X, Y and Z axis directions. The thermal insulation box 1 is provided with a PTC heating plate 4 and several temperature sensors 10. There are preferably two temperature sensors 10. The thermal insulation box 1 is provided with a semiconductor refrigeration plate 3. The PTC heating plate 4, the semiconductor refrigeration plate 3, and the several temperature sensors 10 are electrically connected to the temperature control subsystem 2. The semiconductor refrigeration plate 3 is used for cooling the thermal insulation box 1 and providing a low temperature for linear expansion under low temperature conditions. The semiconductor refrigeration plate 3 can quickly return the temperature in the thermal insulation box 1 to a normal temperature after the high-temperature linear expansion measurement, so as to facilitate the linear expansion measurement in the next direction. The PTC heating plate 4 is used for heating the thermal insulation box 1 and providing a high temperature for linear expansion under high temperature conditions. The PTC heating plate 4 can quickly return the temperature in the thermal insulation box 1 to a normal temperature after the low-temperature linear expansion measurement, so as to facilitate the linear expansion measurement in the next direction. Figure 2 As shown, the positive direction of the X-axis is right, the positive direction of the Y-axis is from outside to inside, and the positive direction of the Z-axis is vertically upward.

[0077] like Figure 4 and 5As shown, the fringe interference detection mechanism 8 includes a first interference plate 81, a second interference plate 82, and a mounting base 80 having the same structure. The first interference plate 81 and the second interference plate 82 are both provided with a polarizer mounting hole 85. A first glass plate 83 is disposed in the polarizer mounting hole 85 of the first interference plate 81, and a second glass plate 84 is disposed in the polarizer mounting hole 85 of the second interference plate 82. A rotating shaft 86 is provided on one side of the bottom of the first interference plate 81, and a supporting wheel 87 is provided on the other side of the bottom of the first interference plate 81. A magnetic portion 88 is provided on the first interference plate 81. The first glass plate 83 on the first interference plate 81 and the second glass plate 84 on the second interference plate 82 are fixed in the polarizer mounting hole 85 by inlaying or gluing. The mounting base 80 is provided with a mounting through hole that cooperates with the rotating shaft 86. The rotating shaft 86 is also provided with a thrust bearing that cooperates with the mounting base 80. The second interference plate 82 is also magnetically connected to a fine-tuning rod 89, and the fine-tuning rod 89 includes a support column 891 fixed to the mounting base 80, and a transverse sleeve 892 is provided on the support column 891, and the transverse sleeve 892 is internally threaded with an adjusting rod 893, one end of the adjusting rod 893 is magnetically connected to the second interference plate 82, and the other end of the adjusting rod 893 is provided with an adjusting knob 894, the fine-tuning rod 89 is magnetically connected to the second interference plate 82, and the adjusting knob 894 is used to rotate the adjusting rod 893 to extend or retract, thereby driving the second interference plate 82 to move, and adjusting the second interference plate 82 to a suitable position.

[0078] like Figure 3 and 6As shown, the X-axis measurement transmission mechanism includes an X-axis transfer rod 14, one end of the X-axis transfer rod 14 is fixedly connected to the corresponding sliding support plate 12, and the other end is magnetically connected to the fringe interference detection mechanism 8; a circular through hole for installing the X-axis transfer rod 14 is provided on the insulation box 1. The connecting end of the X-axis transfer rod 14 is provided with a spherical portion 141, and the first interference plate 81 is provided with a magnetic portion 88 and a fastening screw 812. The magnetic portion 88 and the fastening screw 812 are threadedly connected. The first interference plate 81 is also provided with an adjustment opening 811 that cooperates with the fastening screw 812. The spherical portion 141 is provided with a screw portion, and the X-axis transfer rod 14 is provided with a threaded blind hole that cooperates with the screw portion. The spherical portion 141 is threadedly connected to the X-axis transfer rod 14; the magnetic portion 88 is cylindrical, and one end of the magnetic portion 88 is provided with an arc-shaped groove that cooperates with the spherical portion 141. The spherical portion 141 is magnetically connected to the magnetic portion 88. The spherical portion 141 is preferably an iron ball, and the magnetic portion 88 is preferably a magnet or an electromagnet. The magnetic connection between the X-axis measurement transmission mechanism, the Y-axis measurement transmission mechanism, and the Z-axis measurement transmission mechanism and the fringe interference detection mechanism 8 can all adopt the magnetic connection mechanism between the X-axis transmission rod 14 and the first interference plate 81 described above. The magnetic connection between the adjustment rod 893 of the fine-tuning rod 89 and the second interference plate 82 also adopts the above structure, except that the magnetic portion 88 is fixed to the second interference plate 82. In order to better utilize the X-axis transmission rod 14 to perform shrinkage experiments on the material to be tested, screws can be used to connect and secure the fixed support plate 11 and the material to be tested 13.

[0079] The Y-axis measurement transmission mechanism has the same structure as the Z-axis measurement transmission mechanism. The Z-axis measurement transmission mechanism includes a telescopic sleeve 71 mounted on the edge of the insulation box 1. The telescopic sleeve 71 is perpendicular to the edge and angled at 135 degrees with the adjacent surfaces on both sides. A telescopic rod 72 is disposed within the telescopic sleeve 71. The protruding end of the telescopic rod 72 is provided with a rotating cylinder shaft 73. A rotating cylinder 75 is disposed on the rotating cylinder shaft 73. Two L-shaped transmission rods 74 are fixed to the rotating cylinder 75. One L-shaped transmission rod 74 is connected to the corresponding sliding support plate 12. The L-shaped transmission rod 74 is vertically fixed to the sliding support plate 12, and the other sliding support plate 12 is magnetically connected to the fringe interference detection mechanism 8. The telescopic sleeve 71 cooperates with the telescopic rod 72 to adjust the support height or width of the L-shaped transmission rod 74, thereby enabling the measurement of materials to be tested of different widths or heights through the L-shaped transmission rod 74 and the sliding support plate 12, making the Z-axis measurement transmission mechanism and the Y-axis measurement transmission mechanism more applicable.

[0080] The L-shaped transmission rod 74 includes a connecting section for the rotating cylinder 75 and a bent end connected to the fringe interference detection mechanism 8. A leveling bubble 77 is provided on the connecting section. The telescopic sleeve 71 is provided with a threaded through-hole, which is equipped with a locking pin 76 for securing the telescopic rod 72. The thermal insulation box 1 is provided with a strip-shaped through-hole that mates with the L-shaped transmission rod 74. When the Z-axis measurement transmission mechanism is performing deformation and displacement transmission, the Y-axis measurement transmission mechanism can remove the leveling bubble 77 by observing the connecting section of the L-shaped transmission rod 74, thereby adjusting the telescopic rod 72 to the appropriate position and securing it with the locking pin 76. This ensures that the connecting section of the L-shaped transmission rod 74 is parallel to the horizontal plane before operation, facilitating linear expansion measurement in the Z-axis direction.

[0081] Working principle of the three-dimensional linear expansion coefficient measurement system: three fixed support plates 2 are respectively installed at the bottom, left and rear of the insulation box 1, and three sliding support plates 12 are arranged at positions opposite to the fixed support plates 2, so that the material to be tested is clamped between the fixed support plates 2 and the sliding support plates 12, and has good contact; when the material to be tested heats up or cools down, it will expand and contract in the X, Y and Z directions, driving the sliding support plates 12 to move; the sliding support plates 12 are connected to the first interference plate 81 of the fringe interference detection mechanism 8 through the X-axis measurement transmission mechanism, the Y-axis measurement transmission mechanism, and the Z-axis measurement transmission mechanism, and cooperate with the optical measurement subsystem 9 to measure the material expansion in different directions; the moving distance of the sliding support plate 12 in this direction by the optical measurement subsystem 9 is the expansion and elongation of the material to be measured in this direction, which facilitates the calculation of the linear expansion coefficient.

[0082] The measurement method of the three-dimensional linear expansion coefficient measurement system includes the following steps: Figure 7 、 8 , 9, 10, 11 and 12:

[0083] S1: Measure the initial length L0 and initial temperature T0 of the material to be tested, and set the material experimental temperature T;

[0084] S2: Before the experiment begins, connect the measurement transmission mechanism to the fringe interference detection mechanism, and adjust the second glass slide 84 on the second interference plate 82 to be parallel to the first wave plate 83 on the first interference plate 81. This specifically includes the following steps:

[0085] S21: Adjust the first interference plate 81 to be magnetically connected to the transmission rod; adjust the second interference plate 82 to be parallel to the first interference plate 81, and adjust the second interference plate 82 to be magnetically connected to the fine-tuning rod 89;

[0086] S22: Turn on the He-Ne laser 95 and adjust the reading microscope 93 until the crosshairs are visible; adjust the distance between the reading microscope 93 and the second interference plate 82 until clear interference fringes are visible;

[0087] S23: Adjust the angle between the second interferometer plate 82 and the first interferometer plate 81 by rotating the adjustment knob 894 of the fine-tuning rod 89. When the width of the fringes increases, continue to rotate the adjustment knob 894 in this direction until the fringes just disappear. At this time, the second glass slide 84 on the second interferometer plate 82 is parallel to the first wave plate 83 on the first interferometer plate 81.

[0088] S3: Adjust the reading microscope 93 and calculate the actual distance Δ between two pixels using the pixel distance of the crosshairs of the reading microscope 93 and the actual distance. Step S3 specifically includes the following steps:

[0089] S31: Rotate the drum of the reading microscope 93 so that the crosshairs are at position A, record the drum reading L1 at this time, and display and capture the image at this time on the laptop computer 98 via the CCD sensor;

[0090] S32: Continue to rotate the drum of the reading microscope 93 until the crosshairs are at position B, record the drum reading L2 at this time, and display and capture the image of the CCD sensor on the laptop computer 98;

[0091] S33: performing image processing on the crosshairs to obtain pixel values ​​N1 and N2 corresponding to the i-th row when the crosshairs are translated from position A to position B;

[0092] S34: Calculate the actual distance Δ between the two pixels:

[0093]

[0094] S4: Perform an expansion deformation measurement experiment, start the temperature control subsystem, control the temperature in the insulation box 1 to reach the material experiment temperature T, and after the temperature in the insulation box 1 reaches the material experiment temperature T, take a screenshot of the interference fringes displayed on the laptop computer 98 to obtain an interference pattern; Figure 8

[0095] S5: Rotate the interference pattern to an angle of about 45 degrees with the horizontal; select the i-th row of data, obtain the pixel values ​​m1 and m2 corresponding to the peak of the light intensity distribution fitting curve, and the number of peaks K, and calculate the horizontal spacing a:

[0096]

[0097] Where Δ is the actual distance between two adjacent pixels;

[0098] S6: Select the jth column of data to obtain the pixel values ​​n1 and n2 corresponding to the peak of the light intensity distribution fitting curve, as well as the number of peaks L, and calculate the vertical spacing b using the actual distance Δ:

[0099]

[0100] Where Δ is the actual distance between two adjacent pixels;

[0101] S7: Calculate the spacing of the interference fringes, such as Figure 12 :

[0102]

[0103] Where a is the horizontal spacing between adjacent stripes, and b is the vertical spacing between adjacent stripes.

[0104] S8: Calculate the deformation of the material:

[0105]

[0106] Where λ is the wavelength of the incident laser, L is the distance from the contact point between the transmission rod and frame A to the center of the rotating shaft of frame A, and e is the interference fringe spacing;

[0107] S9: Calculate the linear expansion coefficient of the material to be tested;

[0108] Change the material temperature and repeat steps S1 to S8 for multiple measurements. Use the least squares method to calculate the ratio of the material deformation D to the temperature change (T-T0) and the linear expansion coefficient of the material:

[0109]

[0110] Where D is the material deformation, L0 is the initial length of the material, T0 is the initial temperature of the material, and T is the experimental temperature of the material.

Claims

1. A method for measuring a linear expansion coefficient measuring system, the measuring system comprising an insulating box (1), a fringe interference detection mechanism (8) and an optical measurement subsystem (9), wherein three fixed support plates (11) are provided in the insulating box (1), wherein the three fixed support plates (11) are connected perpendicularly to each other in pairs to form a corner structure, and a parallel sliding support plate (12) is provided on the opposite side of each fixed support plate (11), wherein the three sliding support plates (12) are connected to the fringe interference detection mechanism (8) via an X-axis measurement transmission mechanism, a Y-axis measurement transmission mechanism, and a Z-axis measurement transmission mechanism, respectively; A PTC heating plate (4) and a plurality of temperature sensors (10) are provided in the thermal insulation box (1); a semiconductor cooling plate (3) is provided on the thermal insulation box (1); the PTC heating plate (4), the semiconductor cooling plate (3), and the plurality of temperature sensors (10) are electrically connected to the temperature control subsystem (2); The optical measurement subsystem (9) includes a half-reflecting half-mirror (91), a reading microscope (93), a camera (92), a laptop computer (98), a beam expander (94), a first polarizer (96), a second polarizer (97) and a helium-neon laser (95); the laptop computer (98) is connected to the camera (92); the second polarizer (97), the reading microscope (93) and the camera (92) are sequentially located in the laser emission direction of the half-reflecting half-mirror (91); the helium-neon laser (95), the beam expander (94) and the first polarizer (96) are sequentially located in the laser incident direction of the half-reflecting half-mirror (91); the laser emission direction and the half-reflecting half-mirror (91) form an angle of 45°, the laser incident direction and the half-reflecting half-mirror (91) form an angle of 135°, and the laser emission direction is perpendicular to the laser incident direction; The fringe interference detection mechanism (8) includes a first interference plate (81), a second interference plate (82) and a mounting base (80) of the same structure, wherein the first interference plate (81) and the second interference plate (82) are both provided with a polarizing plate mounting hole (85), a first wave plate (83) is provided in the polarizing plate mounting hole (85) of the first interference plate (81), and a second wave plate (84) is provided in the polarizing plate mounting hole (85) of the second interference plate (82); a rotating shaft (86) is provided on one side of the bottom of the first interference plate (81), a supporting wheel (87) is provided on the other side of the bottom of the first interference plate (81), and a magnetic attraction portion (88) is provided on the first interference plate (81); a mounting through hole matched with the rotating shaft (86) is provided on the mounting base (80), and a thrust bearing matched with the mounting base (80) is also provided on the rotating shaft (86); It is characterized by: The following steps are included: S1: Measure the initial length of the material to be tested L 0. Initial temperature T 0, set the material experimental temperature T ; S2: Before the experiment begins, connect the measurement transmission mechanism to the fringe interference detection mechanism, and adjust the second wave plate (84) on the second interference plate (82) to be parallel to the first wave plate (83) on the first interference plate (81); S3: Adjust the reading microscope (93), and calculate the actual distance between two pixels using the pixel distance of the crosshairs of the reading microscope (93) and the actual distance. ; S4: Conduct expansion deformation measurement experiment, start the temperature control subsystem, and control the temperature in the insulation box (1) to reach the material test temperature T , and the temperature in the insulation box (1) reaches the material test temperature T Then, the interference fringes displayed on the laptop (98) are captured to obtain the interference pattern; S5: Rotate the interference pattern to an angle of about 45 degrees with the horizontal; select the i-th row of data, obtain the pixel values ​​m1 and m2 corresponding to the peak of the light intensity distribution fitting curve, and the number of peaks K, and calculate the horizontal spacing : Where Δ is the actual distance between two adjacent pixels; S6: Select the jth column of data, obtain the pixel values ​​n1 and n2 corresponding to the peak of the light intensity distribution fitting curve, and the number of peaks L, and calculate the vertical spacing using the actual distance Δ : Where Δ is the actual distance between two adjacent pixels; S7: Calculate the spacing of the interference fringes: Where, is the horizontal spacing between adjacent stripes, is the vertical spacing between adjacent stripes; S8: Calculate the deformation of the material: Where, is the incident laser wavelength, is the distance from the contact point between the transmission rod and frame A to the center of the rotation axis of frame A, e is the interference fringe spacing; S9: Calculate the linear expansion coefficient of the material to be tested; Change the material temperature, repeat the above steps S1 to S8, and measure multiple times; use the least square method to obtain the material deformation D and temperature change ( TT 0) to obtain the linear expansion coefficient of the material: Where, D is the material deformation, L 0 is the initial length of the material, T 0 is the initial temperature of the material, T is the temperature after the material changes.

2. The method for measuring the linear expansion coefficient according to claim 1, wherein: The X-axis measurement transmission mechanism includes an X-axis transmission rod (14), one end of the X-axis transmission rod (14) is fixedly connected to the corresponding sliding support plate (12), and the other end is magnetically connected to the fringe interference detection mechanism (8); the thermal insulation box (1) is provided with a circular through hole for mounting the X-axis transmission rod (14).

3. The method for measuring the linear expansion coefficient according to claim 1, wherein: The Y-axis measuring transmission mechanism has the same structure as the Z-axis measuring transmission mechanism. The Z-axis measuring transmission mechanism includes a telescopic sleeve (71) installed on the edge of the insulation box (1), a telescopic rod (72) is provided in the telescopic sleeve (71), a rotating cylinder shaft (73) is provided at the protruding end of the telescopic rod (72), a rotating cylinder (75) is provided on the rotating cylinder shaft (73), and two L-shaped transmission rods (74) are fixed on the rotating cylinder (75), one of the L-shaped transmission rods (74) is connected to the corresponding sliding support plate (12), and one of the sliding support plates (12) is magnetically connected to the fringe interference detection mechanism (8).

4. The method for measuring the linear expansion coefficient according to claim 3, wherein: The L-shaped transmission rod (74) includes a connecting section connected to the rotating cylinder (75) and a bent end connected to the fringe interference detection mechanism (8), and a horizontal bubble (77) is provided on the connecting section; a threaded through hole is provided on the telescopic sleeve (71), and a locking pin (76) for fastening the telescopic rod (72) is provided on the threaded through hole; and a strip through hole is provided on the insulation box (1) to cooperate with the L-shaped transmission rod (74).

5. The method for measuring the linear expansion coefficient according to claim 1, wherein: The second interference plate (82) is also magnetically connected to a fine-tuning rod (89), and the fine-tuning rod (89) includes a support column (891) fixed on the mounting base (80), and a transverse sleeve (892) is provided on the support column (891), and the transverse sleeve (892) is internally threadedly connected to an adjustment rod (893), one end of the adjustment rod (893) is magnetically connected to the second interference plate (82), and the other end of the adjustment rod (893) is provided with an adjustment knob (894).

6. The measuring method of the linear expansion coefficient measuring system according to claim 1, characterized in that: Step S2 specifically includes the following steps: S21: Adjust the first interference plate (81) to be magnetically connected to the transmission rod; adjust the second interference plate (82) to be parallel to the first interference plate (81), and adjust the second interference plate (82) to be magnetically connected to the fine-tuning rod (89); S22: Turn on the He-Ne laser (95), adjust the reading microscope (93) until the crosshairs are visible; adjust the distance between the reading microscope (93) and the second interference plate (82) until clear interference fringes are visible; S23: Adjust the angle between the second interference plate (82) and the first interference plate (81) by rotating the adjustment knob (894) of the fine-tuning rod (89). When the stripe width is observed to increase, continue to rotate the adjustment knob (894) in this direction until the stripe just disappears. At this time, the second wave plate (84) on the second interference plate (82) is parallel to the first wave plate (83) on the first interference plate (81).

7. The method for measuring a linear expansion coefficient according to claim 1, wherein: Step S3 specifically includes the following steps: S31: Rotate the drum of the reading microscope (93) so that the crosshairs are at position A, record the drum reading L1 at this time, and display and capture the image at this time on the laptop computer (98) through the CCD sensor; S32: Continue to rotate the drum of the reading microscope (93) so that the crosshairs are at position B, record the drum reading L2 at this time, and display and capture the image CCD sensor at this time on the laptop computer (98); S33: performing image processing on the crosshairs to obtain pixel values ​​N1 and N2 corresponding to the i-th row when the crosshairs are translated from position A to position B; S34: Calculate the actual distance between the two pixels : 。

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