A memory alloy spring deformation amount measuring device

Abstract

This invention proposes a device for measuring the deformation of a shape memory alloy spring, comprising: a fluid storage container, a mounting bracket, and a displacement sensor; the fluid storage container holds a cryogenic fluid, causing the internal temperature of the fluid storage container to be approximately 77K; the mounting bracket, disposed within the fluid storage container, is used to fix the shape memory alloy spring; the displacement sensor, disposed at the top of the shape memory alloy spring, is used to record the deformation of the shape memory alloy spring from its ambient temperature state to the time after the cryogenic fluid is injected into the fluid storage container. This invention can measure the deformation of the shape memory alloy spring under a cryogenic environment of approximately 77K, and by changing the weight of the weight, the test data more closely approximates the operating environment of the shape memory alloy spring, which is beneficial for the design and analysis of shape memory alloy springs and coolers. The operation is simple and quick.

Description

Technical Field

[0001] This invention relates to the field of cryogenic refrigeration technology, and in particular to a device for measuring the deformation of a shape memory alloy spring. Background Technology

[0002] Self-adjusting JT refrigerators are widely used in infrared guidance applications. Compared to direct-injection refrigerators, self-adjusting JT refrigerators feature shorter start-up times and lower gas consumption during stable operation. They come in various self-adjusting forms, including bellows type and shape memory alloy type. The shape memory alloy type refrigerator's self-adjusting structure consists of a driving spring, a shape memory alloy spring, a balance spring, a compensating block, a valve needle, and a valve body. It utilizes the shape memory alloy spring to maintain different shapes at room temperature and low temperature, changing the distance between the valve needle and the valve body to achieve self-regulation of the refrigerator's flow rate. Therefore, the deformation and stability of the shape memory alloy spring are key parameters for ensuring the refrigerator's efficient design and stable operation.

[0003] Currently, most mass-produced shape memory alloys are for room temperature and high temperature, generally not involving low-temperature (77K) operating environments. The shape memory alloy spring involved in this patent operates at an environment temperature close to 77K; this spring is located inside a cooler, and conventional industrial CT and other transmission equipment cannot clearly observe its length through the external multi-layered metal structure, which is detrimental to the cooler's self-adjustment analysis. To measure the deformation of the shape memory alloy spring, Beijing University of Science and Technology designed a horizontal shape memory alloy spring deformation measurement device, using a bias spring to measure the spring's rebound deformation. However, this device uses liquid nitrogen for cooling, which is not conducive to long-term recording and analysis of shrinkage changes. Furthermore, because the liquid nitrogen boils on the surface of the shape memory alloy spring without a storage tank, it may lead to inconsistent temperature field distribution inside the spring, potentially causing instability in the spring's deformation. A novel measurement device is needed to measure the deformation of low-temperature shape memory alloy springs.

[0004] For shape memory alloy (MMA) self-adjusting JT refrigerators, the MMA spring changes the distance between the valve needle and the valve body, determining the refrigerator's flow rate. Its deformation is crucial to the refrigerator's design and operation; especially when the MMA spring's contraction is unstable, it can easily lead to flow rate fluctuations. Furthermore, the time taken for the MMA spring's low-temperature deformation process and its recovery at room temperature reflects the refrigerator's flow rate change rate and interval testing speed, respectively. Therefore, a simple and efficient testing device that can directly reflect the deformation of the MMA spring is needed to analyze its deformation, stability, and deformation time. However, existing MMA spring deformation measurement devices have limited applicability and are not suitable for analyzing the variation of MMA spring deformation with preload at a low temperature of 77K. Summary of the Invention

[0005] The technical problem to be solved by the present invention is that current measuring equipment cannot effectively measure the various parameters of shape memory alloy springs under the low temperature environment of 77K. In view of this, the present invention provides a shape memory alloy spring deformation measuring device.

[0006] The technical solution adopted in this invention is that the shape memory alloy spring deformation measuring device includes:

[0007] A fluid storage container for holding a cryogenic fluid, wherein the cryogenic fluid causes the ambient temperature inside the fluid storage container to include 77K;

[0008] A fixing bracket, disposed inside the fluid storage container, is used to fix the shape memory alloy spring in the vertical direction;

[0009] A displacement sensor is disposed at the top of the shape memory alloy spring to record the deformation of the shape memory alloy spring from room temperature to after the cryogenic fluid is injected into the fluid storage container.

[0010] In one embodiment, the device further includes a stopwatch for recording the time taken for the shape memory alloy spring to deform from its ambient temperature state to the time taken after the cryogenic fluid is injected into the fluid storage container.

[0011] In one embodiment, the device further includes: weights and a pressure sensor;

[0012] The pressure sensor is located below the fluid storage container, and the weight is located on the pressure sensor to measure the preload of the shape memory alloy spring.

[0013] In one embodiment, the device further includes a support frame for mounting the pressure sensor and the displacement sensor.

[0014] In one embodiment, the cryogenic fluid includes at least one of liquid nitrogen and liquid argon.

[0015] In one embodiment, the weights and the fixing frame are made of Kovar material.

[0016] In one embodiment, the length of the central rod of the fixing frame is adjustable.

[0017] In one embodiment, the displacement sensor and the shape memory alloy spring are configured in a non-contact manner.

[0018] By adopting the above technical solution, the present invention has at least the following advantages:

[0019] The shape memory alloy spring deformation measuring device of the present invention can measure the deformation of shape memory alloy springs and change the weight of the weights under low temperature environment of about 77K, so that the test data is closer to the use environment of shape memory alloy springs. This is beneficial to the design and analysis of shape memory alloy springs and coolers, and the operation is simple and quick. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structural composition of a shape memory alloy spring deformation measuring device according to an embodiment of the present invention;

[0021] Figure 2 This is a schematic diagram of the structural composition of a shape memory alloy spring deformation measuring device according to an application example of the present invention;

[0022] Figure Labels

[0023] 1-Support frame, 2-Memory alloy spring, 3-Fixed frame, 4-Weight, 5-Pressure sensor, 6-Stopwatch, 7-Fluid storage container, 8-Displacement sensor. Detailed Implementation

[0024] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments.

[0025] In the accompanying drawings, the thickness, size, and shape of the objects have been slightly exaggerated for ease of illustration. The drawings are for illustrative purposes only and are not drawn to scale.

[0026] It should also be understood that the terms "comprising," "including," "having," "containing," and / or "comprising," when used in this specification, indicate the presence of the stated features, integrals, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or combinations thereof. Furthermore, when expressions such as "at least one of..." appear after a list of listed features, they modify the entire listed feature, not individual elements in the list. Additionally, when describing embodiments of this application, the word "may" is used to mean "one or more embodiments of this application." And the term "exemplary" is intended to refer to an example or illustration.

[0027] As used herein, the terms “basically,” “approximately,” and similar terms are used as terms of approximation rather than terms of degree, and are intended to describe inherent biases in measured or calculated values ​​that will be recognized by those skilled in the art.

[0028] Unless otherwise specified, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. It should also be understood that terms (e.g., those defined in common dictionaries) shall be interpreted as having the meaning consistent with their meaning in the context of the relevant art and shall not be interpreted in an idealized or overly formal sense unless expressly so specified herein.

[0029] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0030] The steps described in the specification and the flowcharts in the accompanying drawings of this invention are not necessarily to be strictly followed according to the step numbers; the execution order of the steps can be changed. Furthermore, certain steps can be omitted, multiple steps can be combined into one step, and / or one step can be broken down into multiple steps.

[0031] The first embodiment of the present invention provides a device for measuring the deformation of a shape memory alloy spring, such as... Figure 1 As shown, it includes:

[0032] A fluid storage container 7 is used to store cryogenic fluids, wherein the cryogenic fluids cause the ambient temperature inside the fluid storage container 7 to reach 77K;

[0033] The fixing bracket 3 is set inside the fluid storage container 7 and is used to fix the shape memory alloy spring 2 in the vertical direction;

[0034] Displacement sensor 8 is located at the top of shape memory alloy spring 2 and is used to record the deformation of shape memory alloy spring 2 after the fluid is injected into the fluid storage container 7 from room temperature to low temperature.

[0035] In one embodiment, the device may further include a stopwatch 6, which in some embodiments can be used to record the time taken for the shape memory alloy spring 2 to change from its normal temperature state to the time taken for cryogenic fluid to be injected into the fluid storage container 7.

[0036] In one embodiment, the device may further include: a weight 4 and a pressure sensor 5;

[0037] Specifically, pressure sensor 5 is positioned below the fluid storage container 7, and weight 4 is located on pressure sensor 5. It is used to measure the preload of the shape memory alloy spring 2. Pressure sensor 5 measures the preload generated by the weight 4 acting on the shape memory alloy spring 2. Adjusting the number of weights 4 changes the preload at both ends of the shape memory spring, inducing low-temperature deformation of the shape memory alloy spring 2, and analyzing the effect of preload on the deformation of the shape memory alloy spring 2.

[0038] In one embodiment, the device may further include: a support frame 1 for mounting the pressure sensor 5 and the displacement sensor 8.

[0039] For example, the displacement sensor 8 includes, but is not limited to, a contactable, gear-driven displacement sensor 8 whose probe can reach the shape memory alloy spring 2; or a non-contact laser displacement sensor.

[0040] In one embodiment, the cryogenic fluid can be at least one of liquid nitrogen and liquid argon.

[0041] In one embodiment, the fluid storage container 7 may be made of a rigid material with low thermal conductivity, which can continuously replenish the cryogenic fluid to prolong the cryogenic phase change time; the weight 4 and the spring holder 3 may be made of materials with low thermal expansion coefficients, including but not limited to Kovar materials, to reduce the measurement error of the deformation of the shape memory alloy spring 2.

[0042] For example, the fixing frame 3 can be selected as a spring fixing frame 3 according to actual needs; in this embodiment, the central rod of the fixing frame 3 has an adjustable length, which facilitates the positioning of the memory alloy spring 2 or the weight 4 by the sensor probe or laser. The stopwatch 6 is used to record the time of the contraction process of the memory alloy spring 2.

[0043] The shape memory alloy spring deformation measuring device provided by this invention can measure the deformation of shape memory alloy springs and change the weight of the weights under a low temperature environment of about 77K, so that the test data is closer to the usage environment of shape memory alloy springs. This is beneficial to the design and analysis of shape memory alloy springs and coolers. The operation is simple and quick.

[0044] Furthermore, this embodiment employs a container capable of storing cryogenic fluids, allowing the shape memory alloy spring to remain in a constant low-temperature environment for an extended period of time.

[0045] Furthermore, in this embodiment, a non-contact displacement sensor and weights can be used to make the preload of the shape memory alloy spring adjustable.

[0046] The second embodiment of the present invention, corresponding to the first embodiment, describes a method for using a shape memory alloy spring deformation measuring device, including the following specific steps:

[0047] Step 1: Assemble the sensor. (See attached image) Figure 1 and attached Figure 2 As shown, displacement sensor 8 and pressure sensor 5 are mounted on support frame 1.

[0048] Step 2: Assemble the shape memory alloy spring. Insert the shape memory alloy spring 2 into the center rod of the spring holder 3 and install it into the cryogenic fluid storage container 7.

[0049] Step 3: Zero the reading of displacement sensor 8.

[0050] Step 4: While starting the stopwatch 6, introduce cryogenic fluid into the cryogenic fluid storage container, causing the shape memory alloy spring 2 to gradually deform at low temperature.

[0051] Step 5: The reading of displacement sensor 8 can reflect the real-time changes and stable values ​​of memory alloy spring 2. After the contraction value stabilizes, stopwatch 6 reflects the time of low-temperature deformation of memory alloy spring 2.

[0052] Step 6: After the liquid nitrogen has evaporated, use a stopwatch 6 to repeat the test after the temperature returns to normal. This will allow you to analyze the fluctuation of the deformation of the shape memory alloy spring 2.

[0053] The third embodiment of the present invention corresponds to the first embodiment. This embodiment introduces a method for using a shape memory alloy spring deformation measuring device. The present invention can be used to measure the preload of shape memory alloy springs and the corresponding change law between the preload and other parameters.

[0054] Step 1: Assemble the sensor. (See attached image) Figure 1 and attached Figure 2 As shown, displacement sensor 8 and pressure sensor 5 are mounted on support frame 1.

[0055] Step 2: Assemble the shape memory alloy spring. Insert the shape memory alloy spring 2 into the center rod of the spring holder 3 and install it into the cryogenic fluid storage container 7.

[0056] Step 3: Zero the readings of pressure sensor 5 and displacement sensor 8.

[0057] Step 4: Place weight 4. The reading of pressure sensor 5 is the preload of the shape memory alloy spring. To make the preload of the shape memory alloy spring 0N, a non-contact displacement sensor such as a laser can be used.

[0058] Step 5: Introduce cryogenic fluid into the cryogenic fluid storage container. The shape memory alloy spring 2 gradually deforms to a stable value at low temperature, and the displacement sensor 8 records the deformation.

[0059] Step 6: Replace weight 4 to change the preload. This allows for testing and analysis of the elastic deformation of the shape memory alloy spring 2 at low temperatures as a function of the preload.

[0060] Step 7: After the temperature returns to normal, replace weight 4, use stopwatch 6 to record the time, and change the preload to test and analyze the total deformation and velocity of the shape memory alloy spring 2 at low temperature as a function of the preload.

[0061] Table 1 shows the test results of the shape memory alloy spring deformation based on the third embodiment. As can be seen from Table 1, after stability training, the shape memory alloy spring deformation is better and consistent with the actual flow rate of the cooler.

[0062] Table 1 Deformation of Shape Memory Alloy Springs

[0063]

[0064] In summary, compared with the prior art, the present invention has at least the following advantages:

[0065] 1) The shape memory alloy spring deformation measuring device provided by the present invention can measure the deformation of the shape memory alloy spring and change the weight of the weight under a low temperature environment of about 77K, so that the test data is closer to the use environment of the shape memory alloy spring, which is beneficial to the design and analysis of shape memory alloy springs and coolers. The operation is simple and quick.

[0066] 2) In some embodiments of the present invention, a container capable of storing cryogenic fluid is used, so that the shape memory alloy spring can be kept in a constant low temperature environment for a long time;

[0067] 3) In some embodiments of the present invention, a non-contact displacement sensor and weights are used to achieve adjustable preload of the shape memory alloy spring.

[0068] Through the description of specific embodiments, a more in-depth and specific understanding should be gained of the technical means and effects adopted by the present invention to achieve the intended purpose. However, the accompanying drawings are only provided for reference and illustration and are not intended to limit the present invention.

Claims

1. A method of measuring the deformation of a memory alloy spring, characterized in that, include: A fluid storage container for holding a cryogenic fluid, wherein the cryogenic fluid causes the ambient temperature inside the fluid storage container to include 77K; A fixing bracket, disposed inside the fluid storage container, is used to fix the shape memory alloy spring in the vertical direction; A displacement sensor is disposed at the top of the shape memory alloy spring to record the deformation of the shape memory alloy spring from room temperature to after the cryogenic fluid is injected into the fluid storage container; Weights and pressure sensors; The pressure sensor is located below the fluid storage container, and the weight is located on the pressure sensor to measure the preload of the shape memory alloy spring. Adjusting the number of weights can change the preload at both ends of the shape memory spring, inducing low-temperature deformation of the shape memory alloy spring. The influence of the preload on the deformation of the shape memory alloy spring is analyzed, including: Step 1: Assemble the sensor; Step 2: Assemble the shape memory alloy spring; Step 3: Zero the readings of the pressure sensor and displacement sensor; Step 4: Place the weights; the pressure sensor reading is the preload of the shape memory alloy spring. Step 5: Introduce cryogenic fluid into the cryogenic fluid storage container. The shape memory alloy spring gradually deforms to a stable value at low temperature, and the displacement sensor records the deformation. Step 6: Change the weights and the preload, and test and analyze the variation of the elastic deformation of the shape memory alloy spring with the preload at low temperature. Step 7: After the temperature returns to normal, change the weights, record the time with a stopwatch, change the preload, and test and analyze the changes in the total deformation and velocity of the shape memory alloy spring with the preload at low temperature.

2. The method for measuring the deformation of a shape memory alloy spring according to claim 1, characterized in that, The method further includes a stopwatch for recording the time taken for the shape memory alloy spring to deform from room temperature to after the cryogenic fluid is injected into the fluid storage container.

3. The method for measuring the deformation of a shape memory alloy spring according to claim 1, characterized in that, The method further includes: a support frame for assembling the pressure sensor and the displacement sensor.

4. The method of claim 1, wherein the shape memory alloy spring is a Nitinol spring. The cryogenic fluid is a cryogenic working medium including at least one of liquid nitrogen and liquid argon.

5. The method for measuring the deformation of a shape memory alloy spring according to claim 1, characterized in that, The weights and the fixing frame are made of Kovar material.

6. The method for measuring the deformation of a shape memory alloy spring according to claim 1, characterized in that, The length of the central rod of the fixing frame is adjustable.

7. The method for measuring the deformation of a shape memory alloy spring according to claim 1, characterized in that, The displacement sensor and the memory alloy spring are connected in a non-contact manner.

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