An apparatus and method for testing the coefficient of thermal expansion of low-temperature composite materials.

Abstract

This invention provides a testing device and method for the coefficient of thermal expansion of low-temperature composite materials. The testing device includes a low-temperature chamber, a fixing element, a slide, and a sample clamp. The sample is connected to the inner side of the sample clamp, and the outer side of the sample clamp is connected to the slide. The slide is connected to the fixing element in a sliding manner. The fixing element is fixed at both ends to the inner side of the low-temperature chamber, and the outer side of the low-temperature chamber is connected to a Dewar flask. The low-temperature chamber includes a displacement measuring device. The coefficient of thermal expansion of the sample is calculated by reading the data indicated by the slide on the displacement measuring device. This invention provides a testing device and method for the coefficient of thermal expansion of low-temperature composite materials, which can effectively immerse large-sized composite material samples in liquid nitrogen to measure the coefficient of thermal expansion. The cooling rate is fast, and the measuring device has the advantages of simple structure, convenient operation, and high accuracy, reducing the cost of the measuring device, reducing measurement time, and improving the measurement efficiency.

Description

Technical Field

[0001] This invention relates to the field of thermal expansion coefficient testing technology, and more specifically, to a testing device and method for the thermal expansion coefficient of low-temperature composite materials. Background Technology

[0002] Currently, the standard testing method for the low-temperature thermal expansion coefficient of LNG cryogenic composite materials involves immersing the sample in liquid nitrogen, with the optical instrument independent of the liquid nitrogen. Six samples are taken longitudinally and transversely in each direction of the test sample, and each measurement requires three measurements of the same sample, with a 2-hour interval between cycles. The sample size is 400×50mm (340mm between markings). The product needs to be pre-loaded during testing to ensure it is under tension. However, existing low-temperature thermal expansion coefficient testing devices are difficult to use for measuring large-sized composite material samples, cannot apply pre-tension, and typically use liquid nitrogen or compressors to lower the ambient temperature around the sample, preventing immersion in liquid nitrogen. Each sample replacement results in a rapid temperature increase, requiring a long cooling time, which fails to meet the requirements of the testing device. Therefore, improving the applicability of low-temperature thermal expansion coefficient measurement devices is of great significance.

[0003] Patent CN114280096A describes a precise testing device and method for bidirectional thermal expansion / contraction deformation across temperature ranges. The device includes: a vibration damping table, a column, a marble platform, two first guide rails and two second guide rails; a first V-block, a second V-block, a first slider, a second slider, a first quartz rod, a second quartz rod, an LVDT displacement sensor, a horizontal displacement stage, a cryogenic container, a positioning stage, a heating plate, a five-dimensional rotary displacement stage, a camera, and a sample. The cryogenic container uses dry ice or liquid nitrogen as the cooling medium. Furthermore, to test thermal expansion deformation at different locations, only the five-axis rotary displacement stage needs to be adjusted to change the measurement position. It also mentions adjusting the two first sliders to make the fixed quartz rod fit tightly against the sample. At the other end of the sample, the horizontal displacement stage is adjusted to move the LVDT displacement sensor along the sample direction, pushing the two moving quartz rods to pre-tighten the sample. This is beneficial to improving the thermal expansion coefficient testing of large-sized samples to some extent. However, the system structure is complex and the operation is relatively cumbersome. Summary of the Invention

[0004] In view of this, the present invention aims to provide a testing device and method for the thermal expansion coefficient of low-temperature composite materials, in order to solve the problems of cumbersome sample replacement in the existing low-temperature thermal expansion coefficient instruments and the low testing efficiency caused by temperature changes before and after sample replacement; thereby improving the testing range of the device, enhancing the testing efficiency of the device, simplifying the complexity of the testing device, and improving the testing accuracy of the device.

[0005] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0006] The present invention relates to a device and method for testing the coefficient of thermal expansion of low-temperature composite materials. The device for testing the coefficient of thermal expansion includes a low-temperature chamber, a fixing member, a slide, and a sample clamp. The sample is connected to the inner side of the sample clamp, and the outer side of the sample clamp is connected to the slide. The slide is connected to the fixing member in a way that allows it to slide. The two ends of the fixing member are fixed to the inner side of the low-temperature chamber, and the outer side of the low-temperature chamber is connected to a Dewar jar. The low-temperature chamber includes a displacement measuring device. The coefficient of thermal expansion of the sample is calculated by reading the data indicated by the slide on the displacement measuring device.

[0007] Furthermore, the cryogenic chamber includes an upper cover, a lower cover, and a viewing window. The upper cover is located on the upper side of the cryogenic chamber, the lower cover is located on the lower side of the cryogenic chamber, and the viewing windows are located on the front and rear sides of the cryogenic chamber, respectively. The upper cover includes a groove, and the bottom of the displacement measuring device is located inside the groove.

[0008] Furthermore, the fasteners include support seats and guide posts. The support seats are respectively located on the lower side of the upper cover and the upper side of the lower cover, and the guide posts are located between the support seats to provide support for the slide.

[0009] Furthermore, the slide includes a slider, a pointer, and a linear bearing. The inner wall of the slider is connected to the outer wall of the linear bearing, the inner wall of the linear bearing is connected to the outer wall of the guide post, the front and rear sides of the slider are respectively connected to the sample clamp, and the pointer is set on the outer side of the slider through a groove.

[0010] Furthermore, the slider includes an upper slider and a lower slider. The upper slider is located at the end of the guide post near the upper cover. The upper side of the upper slider is connected to the support seat by a spring. The spring is used to make the upper slider move at a constant speed on the outer wall of the guide post. The lower slider is located at the end of the guide post near the lower cover.

[0011] Furthermore, the sample fixture includes a first fixture plate and a second fixture plate. One side of the second fixture plate is connected to the slider, and the other side of the second fixture plate is connected to the first fixture plate by bolts.

[0012] Furthermore, the first clamp plate includes a first side surface, and the second clamp plate includes a second side surface. The first side surface contacts the second side surface, and both the first and second sides surface are provided with strip corrugations. The sample is placed between the strip corrugations to prevent slippage when clamping the sample.

[0013] Furthermore, the fasteners can be connected to the cryogenic chamber by bolts, or the fasteners can be bonded to the cryogenic chamber by cryogenic adhesive.

[0014] A method for testing the coefficient of thermal expansion of low-temperature composite materials, the method using the aforementioned testing device for the coefficient of thermal expansion of low-temperature composite materials, the method comprising the following steps:

[0015] Step 1: Fix two samples of the same size and specifications onto the slider using the sample clamps, ensuring that the test areas of the two samples are the same when clamped on the sample clamps.

[0016] Step 2: Apply a preload to the sample using the slider. After the slider comes to rest, read and record the displacement lengths of each pointer: L1, L2, L3, and L4.

[0017] Step 3: Adjust the Dewar valve and introduce liquid nitrogen until the liquid nitrogen completely submerges the sample. After the slider stops again, read and record the displacement lengths L5, L6, L7 and L8 of each pointer at this time.

[0018] Step 4: Calculate the thermal expansion coefficient α of the sample by observing the change in pointer displacement before and after liquid nitrogen.

[0019] Furthermore, in step four, the original length of the sample is recorded as L0, the initial temperature of the low-temperature chamber is recorded as t0, and the temperature measured by the sensor after liquid nitrogen is introduced into the low-temperature chamber is recorded as t1. Then the coefficient of thermal expansion α = [(L1+L3-L2-L4-L5-L6+L7+L8)] / [2L0(t1-t0)].

[0020] Compared with the prior art, the device and method for testing the coefficient of thermal expansion of low-temperature composite materials described in this invention have the following advantages:

[0021] The aforementioned low-temperature composite material thermal expansion coefficient testing device and method can effectively preload large-size composite material samples and immerse them in liquid nitrogen to measure the thermal expansion coefficient. It offers rapid cooling and features a simple structure, convenient operation, and high accuracy. Furthermore, it effectively reduces the cost of the measuring device, shortens measurement time, improves measurement efficiency, and minimizes measurement errors caused by friction. It also ensures that the direction of material displacement change is consistent with the direction of the measured thermal expansion coefficient, thereby further guaranteeing that the measurement direction of the device is consistent with the direction of the measured thermal expansion coefficient, thus meeting the testing requirements for the thermal expansion coefficient in LNG low-temperature composite material testing. Attached Figure Description

[0022] The accompanying drawings, which constitute a part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0023] Figure 1 This is a schematic diagram of the front view of the testing device;

[0024] Figure 2 This is a schematic diagram of the overall cryogenic chamber;

[0025] Figure 3 This is a schematic diagram of the interior of the cryogenic chamber;

[0026] Figure 4 This is a partial schematic diagram of the sample fixture;

[0027] Figure 5 This is a schematic diagram of the linear bearing as a whole.

[0028] Figure 6 This is a schematic diagram of the front view of a linear bearing;

[0029] Figure 7 This is a schematic diagram of the slide block as a whole;

[0030] Figure 8 This is a schematic diagram of the interior of the slide.

[0031] Figure 9 This is a schematic diagram of the overall sample fixture.

[0032] Explanation of reference numerals in the attached drawings: 1. Low-temperature chamber; 101. Displacement measuring device; 1011. Displacement device one; 1012. Displacement device two; 102. Viewing window; 103. Top cover; 104. Bottom cover; 2. Fixing component; 21. Support base; 211. Support base one; 212. Support base two; 213. Support base three; 214. Support base four; 22. Guide column; 221. Guide column one; 222. Guide column two; 3. Slide; 31. Slider; 311, Upper slider; 312, Lower slider; 32, Pointer; 33, Linear bearing; 34, Spring; 341, First spring; 342, Second spring; 35, Slider seat 1; 351, Upper slider 1 block; 352, First pointer; 353, First bearing; 36, Slider seat 2; 361, Upper slider 2 blocks; 362, Second pointer; 363, Second bearing; 37, Slider seat 3; 371, Lower slider 1 block; 372, Third pointer; 373. Third bearing; 38. Sliding seat 4; 381. Lower sliding block 2; 382. Fourth pointer; 383. Fourth bearing; 4. Sample fixture; 41. Upper fixture; 411. Upper first fixture; 4111. Upper first clamping plate; 4112. Upper second clamping plate; 412. Upper second fixture; 4121. Upper third clamping plate; 4122. Upper fourth clamping plate; 42. Lower fixture; 421. Next fixture; 4211. Next clamping plate; 4212. Lower second... Clamping plate; 422, Lower second clamp; 4221, Lower third clamp; 4222, Lower fourth clamp; 43, Clamping plate one; 431, First side; 44, Clamping plate two; 441, Second side; 5, Sample; 6, Display screen; 7, Striped ripples; 71, First stripe; 72, Second stripe; 73, Third stripe; 74, Fourth stripe; 8, Bolt; 9, Groove; 91, First groove; 92, Second groove; 10, Sealing ring. Detailed Implementation

[0033] The inventive concepts of this disclosure will be described below using terminology commonly used by those skilled in the art to communicate the essence of their work to others skilled in the art. However, these inventive concepts may be embodied in many different forms and should not be construed as limited to the embodiments described herein.

[0034] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0035] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0036] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0037] This embodiment is for a thermal expansion coefficient measuring device. Similar to conventional thermal expansion coefficient measuring devices, the overall structure consists of a displacement sensor and a slider 31.

[0038] In existing technologies, low-temperature thermal expansion coefficient testing devices are difficult to measure large-sized composite material samples. Furthermore, the cooling methods typically involve using liquid nitrogen or compressors to lower the ambient temperature around the sample, which does not allow the sample to be immersed in liquid nitrogen. Each time the sample is replaced, the temperature rises sharply, and the waiting time for recooling is long, which cannot meet the requirements of the testing device.

[0039] To address the problems of cumbersome sample replacement and low testing efficiency caused by temperature changes before and after sample replacement in existing low-temperature thermal expansion coefficient instruments, this embodiment proposes a testing device and method for the thermal expansion coefficient of low-temperature composite materials. The thermal expansion coefficient testing device includes a low-temperature chamber 1, a fixing member 2, a slide 3, and a sample clamp 4. The sample 5 is connected to the inner side of the sample clamp 4, and the outer side of the sample clamp 4 is connected to the slide 3. The slide 3 is connected to the fixing member 2 in a way that allows it to slide. The inner wall of the slide 3 is set on the outer wall of the fixing member 2. Both ends of the fixing member 2 are fixed to the inner side of the low-temperature chamber 1, and the outer side of the low-temperature chamber 1 is connected to a Dewar jar. The low-temperature chamber 1 includes a displacement measuring device 101. After the slide 3 moves the sample 5 on the fixing member 2 and stops, the thermal expansion coefficient of the sample 5 is calculated by reading the data indicated by the slide 3 on the displacement measuring device 101. The displacement measuring device 101 includes a scale, a grating, a Hall effect displacement sensor, etc. The fixing member 2 can be connected to the low-temperature chamber 1 by bolts 8, or the fixing member 2 can be bonded to the low-temperature chamber 1 by a low-temperature resistant adhesive.

[0040] The aforementioned testing device significantly simplifies the complexity of conventional low-temperature thermal expansion coefficient testing devices, improves testing accuracy, expands the testing range, reduces testing time, enhances testing efficiency, and lowers testing costs.

[0041] The low-temperature chamber 1 includes an upper cover 103, a lower cover 104, and a viewing window 102. The upper cover 103 is located on the upper side of the low-temperature chamber 1, and the lower cover 104 is located on the lower side of the low-temperature chamber 1. The viewing window 102 is located on the front and rear sides of the low-temperature chamber 1, respectively, for observing the test situation. The upper cover 103 includes a groove 9. The bottom of the displacement measuring device 101 is fixedly located inside the groove 9, and the top of the displacement measuring device 101 is located above the low-temperature chamber 1, for cooperating with the slide 3 to measure the displacement of the slide 3 when the test sample 5 is moved. The low-temperature chamber 1 may also include a display screen 6 and a sealing ring 10. The display screen 6 is located on the outside of the low-temperature chamber 1, for displaying values ​​such as temperature and coefficient of thermal expansion. The sealing ring 10 is located at the bottom of the inner side of the groove 9 and / or the sealing ring 10 is located along the inner edge of the viewing window 102, for... To prevent liquid leakage, at least one groove 9 is provided, including a first groove 91 and a second groove 92. The first groove 91 and the second groove 92 are arranged in a linear array on the upper cover 103 to facilitate the passage of the slide 3. The displacement measuring device 101 includes a displacement device 1011 and a displacement device 1012. The bottom of the displacement device 1011 is fixedly disposed inside the first groove 91, and the top of the displacement device 1011 is disposed above the low temperature chamber 1. The bottom of the displacement device 1012 is fixedly disposed inside the second groove 92, and the top of the displacement device 1012 is disposed above the low temperature chamber 1. The displacement measuring device 101 includes a scale, a grating, and a Hall effect displacement sensor. In this embodiment, up, down, left, and right are all illustrative directions and have no other suggestive meaning.

[0042] The low-temperature chamber 1 effectively improves the low-temperature environment for sample 5 testing. By introducing liquid nitrogen into the low-temperature chamber 1, the environment of sample 5 can be effectively reduced to meet the testing requirements. At the same time, the displacement measuring device 101 can effectively measure the distance that sample 5 moves the slide 3 under different environments, thereby effectively calculating the thermal expansion coefficient of sample 5. This helps to improve the reliability of the device, enhance the airtightness of the device, reduce liquid leakage in the testing device, reduce testing costs, and improve testing efficiency.

[0043] The fixing component 2 includes a support base 21 and a guide post 22. The support base 21 is respectively disposed on the lower side of the upper cover 103 and the upper side of the lower cover 104. The guide post 22 is disposed between the support bases 21 to provide support for the slide 3. The support base 21 includes a first support base 211, a second support base 212, a third support base 213 and a fourth support base 214. The first support base 211 and the second support base 212 are both disposed on the lower side of the upper cover 103 and are arranged horizontally parallel to each other. The third support base 213 and the fourth support base 214 are both disposed on the upper side of the lower cover 104 and are arranged horizontally parallel to each other. The guide post 22 includes a first guide post 221 and a second guide post 222. The first guide post 221 is fixedly disposed between the first support base 211 and the third support base 213, and the second guide post 222 is fixedly disposed between the second support base 212 and the fourth support base 214.

[0044] The installation of fastener 2 effectively improves the stability of the device, enhances the operational stability of slide 3 within the device, simplifies the device structure, saves production costs, greatly improves the economic efficiency of the device, and also helps to improve the measurement precision and reliability of the device.

[0045] At least one slide block 3 is provided. The slide block 3 includes a slider 31, a pointer 32, and a linear bearing 33. The inner wall of the slider 31 is connected to the outer wall of the linear bearing 33, and the inner wall of the linear bearing 33 is connected to the outer wall of the guide post 22. The front and rear sides of the slider 31 are respectively connected to the sample clamp 4. The pointer 32 is set on the outside of the slider 31 through a groove 9. The other end of the pointer 32 can be set parallel to or in contact with the displacement measuring device 101 to facilitate the determination of the displacement of the slider 31 based on the position information of the pointer 32. The slider 31 includes an upper slider 311 and a lower slider 312. The upper slider 311 is set at the end of the guide post 22 near the upper cover 103. The upper side of the upper slider 311 is supported by a spring 34. A support 21 is connected to the upper cover 103. A spring 34 is used to make the upper slider 311 move at a constant speed on the outer wall of the guide post 22. The lower slider 312 is located at one end of the guide post 22 near the lower cover 104. At least one slide 3 is provided. The slide 3 includes a first slide 35, a second slide 36, a third slide 37, and a fourth slide 38. The first slide 35 and the third slide 37 are both located outside the first guide post 221. The first slide 35 is located above the third slide 37. The second slide 36 and the fourth slide 38 are both located outside the second guide post 222. The second slide 36 is located above the fourth slide 38. The first slide 35 and the second slide 36 are arranged horizontally and horizontally. The third slide 37 and the fourth slide 38 are arranged horizontally and horizontally.

[0046] The upper slider 311 includes an upper sliding block 351 and an upper sliding block 361; the lower slider 312 includes a lower sliding block 371 and a lower sliding block 381; the pointer 32 includes a first pointer 352, a second pointer 362, a third pointer 372, and a fourth pointer 382; the linear bearing 33 includes a first bearing 353, a second bearing 363, a third bearing 373, and a fourth bearing 383; the spring 34 includes a first spring 341 and a second spring 342; the sliding base 35 is integrally formed from the upper sliding block 351, the first pointer 352, and the first bearing 353; the upper side of the upper sliding block 351 is connected to the support base 211 via the first spring 341. The inner wall of the upper sliding block 351 is connected to the outer wall of the first bearing 353, and the inner wall of the first bearing 353 is connected to the outer wall of the guide post 221. The front and rear sides of the upper sliding block 351 are respectively connected to the sample clamp 4. One end of the first pointer 352 is set on the outer side of the upper sliding block 351 through the first groove 91, and the other end of the first pointer 352 is set parallel to or in contact with the displacement device 1011. The sliding seat 36 is integrally formed by the upper sliding block 361, the second pointer 362, and the second bearing 363. The upper side of the upper sliding block 361 is connected to the support seat 212 through the spring 342, and the inner wall of the upper sliding block 361 is connected to the outer wall of the second bearing 363. The inner wall of the second bearing 363 is connected to the outer wall of the guide post 222. The front and rear sides of the upper sliding block 361 are respectively connected to the sample clamp 4. One end of the second pointer 362 is set on the outer side of the upper sliding block 361 through the second groove 92, and the other end of the second pointer 362 is set parallel to or in contact with the displacement device 1012. The sliding seat 37 is integrally formed by the lower sliding block 371, the third pointer 372 and the third bearing 373. The inner wall of the lower sliding block 371 is connected to the outer wall of the third bearing 373. The inner wall of the third bearing 373 is connected to the outer wall of the guide post 221. The front and rear sides of the lower sliding block 371 are respectively connected to the sample clamp 4. The third pointer 362 is connected to the guide post 222. One end of the third pointer 372 is set on the outside of the sliding block 371 through the first groove 91, and the other end of the third pointer 372 is set parallel to or in contact with the displacement device 1011; the sliding seat 38 is integrally formed by the sliding block 381, the fourth pointer 382 and the fourth bearing 383. The inner wall of the sliding block 381 is connected to the outer wall of the fourth bearing 383, and the inner wall of the fourth bearing 383 is connected to the outer wall of the guide post 222. The front and rear sides of the sliding block 381 are respectively connected to the sample clamp 4. One end of the fourth pointer 382 is set on the outside of the sliding block 381 through the second groove 92, and the other end of the fourth pointer 382 is set parallel to or in contact with the displacement device 1012.

[0047] By setting up the slide block 3, the measurement accuracy of the device can be effectively improved and the measurement complexity of the device can be simplified. This makes the device for measuring the coefficient of thermal expansion more simplified, which is conducive to improving the convenience of the device and reducing the cost of the device. At the same time, the cooperation of the four slide blocks 3 can improve the measurement accuracy of the device while ensuring the simplification of the device, and enhance the applicability and effectiveness of the device. The setting of the pointer 32 can improve the visibility of the device, effectively present the changes of the sample 5, and calculate the coefficient of thermal expansion of the sample 5 through the recorded displacement data, which greatly improves the testing efficiency of the sample 5 and expands the range of samples that can be tested. The cooperation between the slide block 3 and the guide post 22 ensures to a certain extent that the direction of the displacement change of the measured sample 5 is in the direction of the measured coefficient of thermal expansion. The upper slider 311 is connected to the support base 21 through the spring 34, which can effectively ensure the stability of the device operation and improve the uniformity of the device's operating speed. The linear bearing 33 is set in the slider 31 to ensure that the slide block 3 can reciprocate on the two guide posts 22, ensuring that the displacement measurement direction of the sample 5 is consistent with the direction of its coefficient of thermal expansion.

[0048] At least one sample clamp 4 is provided. The sample clamp 4 includes a clamping plate 43 and a clamping plate 44. One side of the clamping plate 44 is connected to the slider 31, and the other side of the clamping plate 44 is connected to the clamping plate 43 by bolts 8, for clamping the sample 5. The clamping plate 43 includes a first side surface 431, and the clamping plate 44 includes a second side surface 441. The first side surface 431 and the second side surface 441 are in contact. Both the first side surface 431 and the second side surface 441 are provided with strip corrugations 7. The sample 5 is placed between the strip corrugations 7. To prevent slippage when clamping sample 5, the sample clamp 4 also includes an upper clamp 41 and a lower clamp 42. The upper clamp 41 is located on the front and / or rear side of the upper slider 311, and the lower clamp 42 is located on the front and / or rear side of the lower slider 312. The upper clamp 41 includes striped corrugations 7, which clamp the upper end of sample 5. The lower clamp 42 includes striped corrugations 7, which clamp the lower end of sample 5. The upper clamp 41 includes an upper clamp 411 and an upper clamp 412. 11 and the upper two clamps 412 are arranged parallel to each other on the front and rear sides of the upper slider 311. The upper clamp 411 is located on the front side of the upper slider 311, with one end of the upper clamp 411 located on the front side of the upper sliding block 351 and the other end of the upper clamp 411 located on the front side of the upper sliding block 361. The upper two clamps 412 are located on the rear side of the upper slider 311. One end of the upper two clamps 412 is located on the rear side of the upper sliding block 351 and the other end of the upper two clamps 412 is located on the rear side of the upper sliding block 361. The lower clamp 42 includes the lower clamp 421. The lower two clamps 422, the lower clamp 421 and the lower two clamps 422 are arranged parallel to each other on the front and rear sides of the lower slide block 312. The lower clamp 421 is located on the front side of the lower slide block 312, with one end of the lower clamp 421 located on the front side of the lower slide block 371 and the other end of the upper clamp 411 located on the front side of the lower slide block 381. The lower two clamps 422 are located on the rear side of the lower slide block 312, with one end of the lower two clamps 422 located on the rear side of the lower slide block 371 and the other end of the lower two clamps 422 located on the rear side of the lower slide block 381.

[0049] Among them, the striped ripples 7 include a first stripe 71, a second stripe 72, a third stripe 73, and a fourth stripe 74. The upper clamp 411 includes an upper clamping plate 4111 and an upper second clamping plate 4112. One side of the upper second clamping plate 4112 is connected to the front side of the upper slider 311, and the left and right ends of the other side of the upper second clamping plate 4112 are respectively connected to the left and right ends of the upper clamping plate 4111 by bolts 8. Both the upper clamping plate 4111 and the upper second clamping plate 4112 are provided with the first stripe 71, and the upper end of the sample 5 is positioned between the first stripes 71. The upper second clamping plate 412 includes an upper third clamping plate 4121 and an upper fourth clamping plate 4122. One side of the upper fourth clamping plate 4122 is connected to the rear side of the upper slider 311, and the left and right ends of the other side of the upper fourth clamping plate 4122 are respectively connected to the left and right ends of the upper third clamping plate 4121 by bolts 8. Both the upper third clamping plate 4121 and the upper fourth clamping plate 4122 are provided with the second stripe 74. 2. The upper end of sample 5 is positioned between the second stripes 72; the next clamp 421 includes a lower clamp 4211 and a lower second clamp 4212. One side of the lower second clamp 4212 is connected to the front side of the lower slider 312, and the left and right ends of the other side of the lower second clamp 4212 are respectively connected to the left and right ends of the lower clamp 4211 by bolts 8. Both the lower clamp 4211 and the lower second clamp 4212 are provided with a third stripe 73, and the lower end of sample 5 is positioned between the third stripes 73; the lower second clamp 422 includes a lower third clamp 4221 and a lower fourth clamp 4222. One side of the lower fourth clamp 4222 is connected to the rear side of the lower slider 312, and the left and right ends of the other side of the lower fourth clamp 4222 are respectively connected to the left and right ends of the lower third clamp 4221 by bolts 8. Both the lower third clamp 4221 and the lower fourth clamp 4222 are provided with a fourth stripe 74, and the lower end of sample 5 is positioned between the fourth stripes 74.

[0050] The sample clamp 4 helps to enhance the fixing force of the device on the sample 5, enhance the stability and reliability of the device during testing, and ensure the safety of the sample 5 during testing. It also ensures that the testing area of ​​the sample 5 is the same when both clamps are used at the same time, effectively improving the accuracy of the thermal expansion coefficient test of the sample 5. The strip corrugations 7 can further effectively prevent the sample 5 from slipping off the clamp of the sample clamp 4, reduce the measurement error caused by friction in the measuring device, and improve the accuracy of the measurement.

[0051] A method for testing the coefficient of thermal expansion of low-temperature composite materials, the method using the aforementioned testing device for the coefficient of thermal expansion of low-temperature composite materials, the method comprising the following steps:

[0052] Step 1: Fix two samples 5 of the same size and specifications onto the slider 31 using the sample clamp 4, and ensure that the test areas of the two samples 5 are the same when clamped on the sample clamp 4. The slider 31 is set in the low temperature chamber 1 by the fixing part 2. In this embodiment, "same size and specifications" means that the samples 5 have the same length, thickness and width, and has no other implied meaning.

[0053] Step 2: Apply different preloads to sample 5 by changing sliders 31 of different masses. After sliders 31 come to rest and pointers 32 stabilize, read and record the displacement lengths L1, L2, L3 and L4 of each pointer 32. In this embodiment, different preloads can be applied to sample 5 by changing sliders 31 of different masses as needed, which improves the observability of the device, but it is not limited to this in practice.

[0054] Step 3: Adjust the Dewar valve and introduce liquid nitrogen until the liquid nitrogen completely submerges the sample 5. After the slider 31 comes to a stop again, read and record the displacement lengths L5, L6, L7 and L8 of each pointer 32 at this time.

[0055] Step 4: Calculate the coefficient of thermal expansion α of sample 5 by measuring the displacement changes before and after liquid nitrogen.

[0056] The method described above can effectively reduce the testing time of the testing device, thereby improving the testing efficiency of the testing device. It can meet the testing requirements for the coefficient of thermal expansion at low temperature in LNG cryogenic composite materials, and can change the ambient temperature of sample 5 by opening and closing the Dewar tank valve, avoiding the extension of testing time caused by changes in the surrounding environment when replacing the sample, thus effectively improving the stability of the test.

[0057] In step one, bolts 8 are used to clamp sample 5 inside the upper clamp 41 and the lower clamp 42, and both the upper clamp 41 and the lower clamp 42 are fixed to the slider 31. Both the upper clamp 41 and the lower clamp 42 are provided with corrugated stripes 7, including wavy stripes, to prevent slippage of sample 5. Sample 5 can be made of composite material. In steps two and three, as sample 5 undergoes thermal expansion at different ambient temperatures, its length changes, causing slider 31 to move on guide post 22. Slider 31 moves pointer 32, recording the displacement change of sample 5's length before and after thermal expansion at ambient temperatures without liquid nitrogen and at ambient temperatures with liquid nitrogen. The coefficient of thermal expansion of sample 5 is calculated. Lubricant is applied between slider 31 and guide post 22 to reduce friction and prevent slider 312 from being damaged by the guide post 22 at low temperatures. Freezing ensures that the slider 31 can reciprocate on the guide post 22, ensuring the accuracy of the thermal expansion coefficient result of the sample 5 in the direction of the tested thermal expansion coefficient. In step two, the material of the slider 31 includes a low expansion coefficient material, such as Invar steel. In step three, the sample clamp 4 is made of a material with a small thermal expansion coefficient, such as 0° carbon fiber composite material or Invar steel. In step four, the original length of the sample 5 is recorded as L0, the initial temperature of the low temperature chamber 1 is recorded as t0, and the temperature measured by the sensor after liquid nitrogen is introduced into the low temperature chamber 1 is recorded as t1. Then the thermal expansion coefficient α = [(L1 + L3 - L2 - L4 - L5 - L6 + L7 + L8)] / [2L0(t1 - t0)]. The low temperature chamber 1 is equipped with a dedicated viewing window 102 for real-time observation of the test. In this embodiment, the inner layer of the low temperature chamber 1 is composed of stainless steel, polyurethane foam and insulation layer, but it is not limited to this in practice.

[0058] By using the weight of the slider 312 itself, a preload can be applied to the sample 5, keeping the sample 5 in a stable vertical state. As the sample 5 undergoes thermal expansion, its length changes, causing the slider 31 to move. The slider 31 then moves the pointer 32. Based on the displacement change of the pointer 32, the coefficient of thermal expansion can be calculated, simplifying the complexity of the testing device and method, and improving the accuracy of the test.

[0059] Example 1

[0060] Take two composite material samples 5 of the same size, and clamp the upper and lower ends of the two samples 5 with the sample clamp 4 using bolts 8, ensuring that the clamping areas are the same. Fix the clamp 4 to the slider 31. The upper slider 311 is connected to the support base 21 through the spring 34 to ensure stable operation of the device. Record the initial data pointed to by the pointer 32 after clamping the sample 5. Replace the lower slider 312 with a different mass according to the required preload to ensure that the sample 5 remains vertical and stable. The low temperature chamber 1 is equipped with a scale and a scale reading telescope. After the pointer 32 connected to the slider 31 stabilizes, read the data pointed to by the pointer 32 after stabilization. Calculate the change in the value pointed to by the pointer 32 before and after movement. Record the displacement change of the first pointer 352 as L1, the displacement change of the second pointer 362 as L2, the displacement change of the third pointer 372 as L3, and the displacement change of the fourth pointer 382 as L4. Close the low temperature chamber 1 and open the Dewar. The valve of the tank is opened, and liquid nitrogen is introduced to immerse the sample 5 in liquid nitrogen. After the measured temperature display reaches the test temperature and the pointer 32 stabilizes, the displacement change of the first pointer 352 is recorded as L5, the displacement change of the second pointer 362 as L6, the displacement change of the third pointer 372 as L7, and the displacement change of the fourth pointer 382 as L8 using a ruler-reading telescope. Specifically, L5, L6, L7, and L8 refer to the displacement changes of the pointer 32 after it stabilizes after liquid nitrogen is introduced and the test temperature is reached, relative to the reading of the pointer 32 after it stabilizes without liquid nitrogen. Then, the original length of the sample 5 is recorded as L0, the initial temperature of the low-temperature chamber 1 is recorded as t0, and the temperature measured by the sensor after liquid nitrogen is introduced into the low-temperature chamber 1 is recorded as t1. The coefficient of thermal expansion α can be calculated by the formula α=[(L1+L3-L2-L4-L5-L6+L7+L8)] / [2L0(t1-t0)].

[0061] By setting up the scale and the reading telescope, the change of pointer 32 in the device test can be effectively reflected, thereby testing the displacement change of sample 5 caused by thermal expansion and contraction. At the same time, the visibility of the thermal expansion change of sample 5 is improved, the testing efficiency of the device is improved, the testing stability of the device is enhanced, and the measurement of the device is made simpler, which is conducive to the wide application of the test.

[0062] Example 2

[0063] Take two composite material samples 5 of the same size, and clamp the upper and lower ends of the two samples 5 with the sample clamp 4 using bolts 8, ensuring that the clamping areas are the same. Fix the clamp 4 on the slider 31. The upper slider 311 is connected to the support base 21 through the spring 34 to ensure stable operation of the device. Record the initial data pointed to by the pointer 32 after clamping the sample 5. Replace the lower slider 312 with a different mass according to the required preload to ensure that the sample 5 remains vertical and stable. A grating is set on the low temperature chamber 1. After the pointer 32 connected to the slider 31 stabilizes, read the data pointed to by the pointer 32 after stabilization. Calculate the change in the value pointed to by the pointer 32 before and after movement. Record the displacement change of the first pointer 352 as L1, the displacement change of the second pointer 362 as L2, the displacement change of the third pointer 372 as L3, and the displacement change of the fourth pointer 382 as L4. Close the low temperature chamber 1, open the Dewar flask valve, introduce liquid nitrogen and immerse the sample 5 to be measured. After the temperature display reaches the test temperature and the pointer 32 stabilizes, the grating automatically measures and records the displacement change of the first pointer 352 as L5, the displacement change of the second pointer 362 as L6, the displacement change of the third pointer 372 as L7, and the displacement change of the fourth pointer 382 as L8. Here, L5, L6, L7, and L8 refer to the displacement changes of the pointer 32 after it stabilizes following the introduction of liquid nitrogen to reach the test temperature, relative to the reading of the pointer 32 after it stabilizes without the introduction of liquid nitrogen. The thermal expansion coefficient is directly calculated by the built-in program and displayed on the display screen 6. The calculation of the built-in program can be set by recording the original length of the sample 5 as L0, the initial temperature of the low-temperature chamber 1 as t0, and the temperature measured by the sensor after the introduction of liquid nitrogen into the low-temperature chamber 1 as t1. The thermal expansion coefficient can then be calculated and set according to the formula α=[(L1+L3-L2-L4-L5-L6+L7+L8)] / [2L0((t1-t0)].

[0064] By changing the measuring device, the automation of the device measurement can be further improved, the testing efficiency of the device can be effectively increased, the testing stability of the device can be enhanced, the testing of the device can be made more automated, and the accuracy of the device measurement can be further guaranteed.

[0065] In this invention, any thermal expansion coefficient testing device may include the structure of a testing device for the thermal expansion coefficient of low-temperature composite materials as described in this embodiment. Based on the relevant structure and assembly relationship of the slide 3 and the low-temperature chamber 1 provided in this embodiment, the thermal expansion coefficient testing device also includes conventional components such as displacement sensors and sliders 31. Since these are all prior art, they will not be described in detail here.

[0066] 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 within the protection scope of the present invention.

Claims

1. A device for testing the coefficient of thermal expansion of low temperature composites, characterized in that, The low-temperature box (1) includes a fixing part (2), a sliding seat (3) and a sample clamp (4), a sample (5) is connected to the inner side of the sample clamp (4), the outer side of the sample clamp (4) is connected to the sliding seat (3), the sliding seat (3) is connected to the fixing part (2) in a sliding manner, the two ends of the fixing part (2) are fixed to the inner side of the low-temperature box (1), the outer side of the low-temperature box (1) is connected to a Dewar flask, the low-temperature box (1) includes a displacement measuring device (101), the thermal expansion coefficient of the sample (5) is calculated by reading the data indicated by the sliding seat (3) on the displacement measuring device (101); the low-temperature box (1) includes an upper cover (103), the upper cover (103) includes a groove (9), the bottom of the displacement measuring device (101) is arranged inside the groove (9); the fixing part (2) includes guide columns (22) and support seats (21), the guide columns (22) are arranged between the support seats (21) to provide support for the sliding seat (3), the support seats (21) include support one seats (211), support two seats (212), support three seats (213) and support four seats (214), the support one seats (211) and the support two seats (212) are arranged in parallel on the left and right sides, the support three seats (213) and the support four seats (214) are arranged in parallel on the left and right sides, the guide columns (22) include guide one columns (221) and guide two columns (222), the guide one columns (221) are fixedly arranged between the support one seats (211) and the support three seats (213), the guide two columns (222) are fixedly arranged between the support two seats (212) and the support four seats (214), the sliding seat (3) includes a sliding block (31), a pointer (32) and a linear bearing (33), the inner side wall of the sliding block (31) is connected to the outer side wall of the linear bearing (33), the inner side wall of the linear bearing (33) is connected to the outer side wall of the guide column (22), the front and rear sides of the sliding block (31) are respectively connected to the sample clamp (4), the pointer (32) is arranged outside the sliding block (31) through the groove (9); the sliding block (31) includes an upper sliding block (311) and a lower sliding block (312), the upper sliding block (311) is arranged at one end of the guide column (22) close to the upper cover (103), the upper side of the upper sliding block (311) is connected to the support seat (21) through a spring (34), the spring (34) is used to make the upper sliding block (311) move at a constant speed on the outer side wall of the guide column (22), and the lower sliding block (312) is arranged at one end of the guide column (22) close to a lower cover (104).

2. The device for testing the thermal expansion coefficient of low-temperature composite materials according to claim 1, characterized in that, The low-temperature box (1) includes a lower cover (104) and a visual window (102), the upper cover (103) is arranged on the upper side of the low-temperature box (1), the lower cover (104) is arranged on the lower side of the low-temperature box (1), and the visual window (102) is arranged on the front and rear sides of the low-temperature box (1) respectively.

3. A device for testing the coefficient of thermal expansion of low temperature composites according to claim 2, characterized in that, The support seats (21) are arranged on the lower side of the upper cover (103) and the upper side of the lower cover (104) respectively.

4. The device for testing the thermal expansion coefficient of low-temperature composite materials according to claim 1, characterized in that, The sample clamp (4) includes a clamp one plate (43) and a clamp two plate (44), one side of the clamp two plate (44) is connected to the sliding block (31), and the other side of the clamp two plate (44) is connected to the clamp one plate (43) through a bolt (8).

5. A device for testing the coefficient of thermal expansion of low temperature composites according to claim 4, wherein, The first side (431) and the second side (441) are provided with strip-shaped corrugations (7), and the sample (5) is arranged between the strip-shaped corrugations (7) to prevent slipping when the sample (5) is clamped.

6. The device for testing the thermal expansion coefficient of low-temperature composite materials according to claim 3, characterized in that, The fixing member (2) can be connected with the low-temperature box (1) through bolts (8), or the fixing member (2) can be bonded with the low-temperature box (1) through a low-temperature resistant adhesive.

7. A method for testing the coefficient of thermal expansion of cryogenic composites, characterized in that, The test method uses a test device for the thermal expansion coefficient of a low-temperature composite material according to any one of claims 1-6, and the method comprises the following steps: Step one, two samples (5) of the same size are fixed on the sliding block (31) through the sample clamp (4), and the two samples (5) are ensured to be clamped on the same test area of the sample clamp (4); Step two, pre-tighten the sample (5) through the sliding block (31), and after the sliding block (31) is stationary, read and record the displacement lengths L1, L2, L3 and L4 of the respective pointers (32); Step three, adjust the valve of the Dewar flask and introduce liquid nitrogen until the liquid nitrogen completely covers the sample (5), and after the sliding block (31) is stationary again, read and record the displacement lengths L5, L6, L7 and L8 of the respective pointers (32) at this time; Step four, calculate the thermal expansion coefficient α of the sample (5) through the displacement changes of the liquid nitrogen front and rear pointers (32).

8. A method for testing the coefficient of thermal expansion of a cryogenic composite material according to claim 7, characterized in that, In step four, the original length of the sample (5) is L0, the initial temperature of the low-temperature box (1) is t0, and the temperature measured by the sensor after the low-temperature box (1) is introduced into liquid nitrogen is t1, then the thermal expansion coefficient α = [(L1+L2-L3-L4-L5-L6+L7+L8)] / [2L0(t1-t0)].

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