A high-precision measurement device and method for the coefficient of linear expansion of solids based on magnetostrictive displacement sensing

Abstract

This invention provides a high-precision measurement device and method for the coefficient of linear expansion of solids based on magnetostrictive displacement sensing, comprising a heating device, a magnetostrictive displacement sensor, a high-precision support, a digital thermometer, and a host computer. The heating device is used to contain and control the temperature of the rod-shaped sample under test. The digital thermometer is used to measure the real-time temperature of the rod-shaped sample and upload the temperature measurement results to the host computer. The magnetostrictive displacement sensor is fixed to the outside of the heating device, and the sensor rod is made to coaxially contact the end of the rod-shaped sample under test through an expansion length transmission rod, and outputs voltage data characterizing the elongation to the host computer. The high-precision support is used to fix the magnetostrictive displacement sensor. The host computer receives the temperature measurement results and the elongation measurement results, and calculates the coefficient of linear expansion. This invention achieves high-precision, automated, and repeatable measurement of the coefficient of linear expansion of the rod-shaped sample under test within a certain temperature range.

Description

Technical Field

[0001] This invention relates to the fields of physics experiment teaching and precision measurement, and in particular to a high-precision measurement device and method for the coefficient of linear expansion of solids based on magnetostrictive displacement sensing. Background Technology

[0002] The coefficient of linear expansion of solids is a key physical quantity characterizing the thermal expansion properties of materials, and it has important applications in bridge and building structural design, precision optical instruments, electronic packaging, and high-precision mechanical structures. In engineering design, mismatched thermal expansion between different materials can easily lead to thermal stress concentration, causing structural deformation or even failure. Therefore, accurately measuring the coefficient of linear expansion of materials is an important experiment in university physics studies.

[0003] Currently, the commonly used measurement method in universities and laboratories involves using a temperature-controlled linear expansion coefficient measuring instrument with a dial gauge: the metal rod to be tested is placed in a heating chamber, heated electrically, and the micrometer is used to measure the slight elongation of the rod at different temperature points. The linear expansion coefficient is then calculated based on the initial length and temperature difference. This traditional method has the following main problems: (1) Large thermal delay interference: Temperature displays typically come from external temperature sensors in the heating device. There is a significant time delay between the actual internal temperature of the heated sample and the instrument display, which causes the elongation read at the preset temperature point to not correspond to the true equilibrium temperature, resulting in systematic errors.

[0004] (2) Errors and inefficiency of manual readings: The experiment requires the experimenter to manually read the micrometer reading at each temperature point, which is easily affected by subjective factors such as parallax and operating habits. Moreover, it cannot achieve high-density continuous sampling and can only obtain a small number of discrete data points.

[0005] (3) It is impossible to achieve synchronous and continuous temperature-displacement measurement: Traditional methods typically only record a few typical temperature points (such as 30℃, 40℃, 50℃, etc.), lacking continuous tracking of the entire heating process and failing to comprehensively analyze the material's expansion characteristics throughout the entire temperature range.

[0006] (4) The device structure has poor compatibility with new sensors: Traditional devices are mainly designed with mechanical dial indicators, which makes it difficult to directly install new electronic displacement sensors, thus limiting the introduction of higher-precision electronic measurement and automated data acquisition solutions. Summary of the Invention

[0007] This application provides a high-precision measurement device and method for the coefficient of linear expansion of solids based on magnetostrictive displacement sensing, in order to solve the problems in the background art.

[0008] Other features and advantages of this application will become apparent from the following detailed description, or may be learned in part from practice of this application.

[0009] According to a first aspect of the embodiments of this application, a high-precision measuring device for the coefficient of linear expansion of a solid based on magnetostrictive displacement sensing is provided, including a heating device, a magnetostrictive displacement sensor, a high-precision bracket, a digital thermometer, and a host computer. The heating device is used to hold the rod-shaped sample to be tested and to heat it at a controlled temperature; the heating device is provided with a probe insertion hole and a sample insertion hole; The digital thermometer is used to measure the real-time temperature of the rod-shaped sample being tested and upload the temperature measurement results to the host computer; the temperature probe of the digital thermometer is inserted into the probe insertion hole of the heating device and comes into contact with the rod-shaped sample being tested to complete the temperature measurement. The magnetostrictive displacement sensor is fixed to the outside of the heating device, so that the sensor rod is in coaxial contact with the end of the rod-shaped sample being tested. It is used to measure the elongation of the rod-shaped sample being tested during the heating process and output voltage data characterizing the elongation to the host computer. The high-precision bracket is used to fix the magnetostrictive displacement sensor, to ensure that the magnetostrictive displacement sensor is axially concentric with the rod-shaped sample being measured, and to apply preload. The host computer receives the temperature measurement results and the elongation measurement results, and calculates the coefficient of linear expansion.

[0010] According to one embodiment of this application, the heating device includes a housing, a sample holder, and a heating coil; the housing is a cylindrical cavity structure, with a sample insertion hole at the center of one end of the housing for inserting a rod-shaped sample to be tested, and a probe insertion hole in the middle of the housing for inserting a temperature measuring probe; the sample holder is disposed inside the housing for supporting the rod-shaped sample to be tested, such that the rod-shaped sample to be tested is positioned on the axis of the housing; the heating coil is arranged around the sample holder for heating the rod-shaped sample to be tested in the sample holder.

[0011] According to one embodiment of this application, the heating device includes a plurality of heating coils arranged around the sample holder, with a preset interval between each heating coil.

[0012] According to one embodiment of this application, it further includes an expansion length transmission rod. After the test rod sample is inserted into the housing, the expansion length transmission rod is inserted into the sample insertion hole and contacts the test rod sample. The probe of the magnetostrictive displacement sensor then contacts the expansion length transmission rod. The displacement of the expansion length transmission rod is the expansion length of the test rod sample.

[0013] According to one embodiment of this application, it further includes a voltage acquisition module, the input end of which is connected to the signal end of the magnetostrictive displacement sensor to receive continuous analog voltage signals; the output end of the voltage acquisition module is connected to the host computer to upload the acquired voltage data; the voltage data characterizes the elongation of the tested rod-shaped sample.

[0014] According to one embodiment of this application, the high-precision bracket is prepared by three-dimensional modeling and 3D printing, including a base, a column, and a clamp; the column is a height-adjustable structure and is fixed on the base; the clamp is disposed on the top of the column and is used to clamp the magnetostrictive sensor; after the magnetostrictive sensor is installed, the probe end of the magnetostrictive sensor contacts the expansion length transmission rod, and a predetermined pressure is set by the clamp.

[0015] According to one embodiment of this application, the process of the host computer obtaining the coefficient of linear expansion includes: Acquire temperature measurement results and voltage data; Based on the temperature sampling points, the average voltage data of N adjacent voltage data points are grouped and averaged to obtain the average voltage at each temperature; Substitute the average voltage into the calibration formula to convert it into the length change ΔL; Plot a curve with temperature T as the abscissa and ΔL as the ordinate, and perform linear fitting to obtain the fitting slope s; Calculate the linear expansion coefficient based on the fitted slope s. α = s / L 0, L 0 represents the initial length of the rod-shaped sample being tested.

[0016] According to one embodiment of this application, the calibration formula acquisition process includes: At room temperature, the rod-shaped sample to be tested is kept unheated, and the sensor output voltage is recorded. Using a standard displacement device or a displacement platform with a known range, several known displacements are applied to the magnetostrictive sensor, and the corresponding voltage values ​​are obtained. The calibration formula is obtained by fitting the known displacements with the corresponding voltage values.

[0017] According to a second aspect of the embodiments of this application, a measurement method is provided based on the high-precision measurement device for the coefficient of linear expansion of a solid based on magnetostrictive displacement sensing as described in the first aspect, comprising: One end of the rod-shaped sample to be tested is inserted into the heating device and fixed, while the other end serves as the free expansion end; the rod-shaped sample to be tested can be a solid metal sample or a non-metal sample. Next, insert the expansion length transfer rod into the heating device, so that one end of it contacts the free expansion end of the rod-shaped sample being tested, and the other end protrudes outside the heating device; The magnetostrictive displacement sensor is fixed to the outside of the heating device using a high-precision bracket, so that the end of the sensor probe contacts the expansion length transmission rod. The preload of the sensor probe and the expansion length transmission rod is adjusted by the clamp on the high-precision bracket. The signal output terminal of the magnetostrictive displacement sensor is connected to the host computer through a voltage acquisition module. Insert the probe of the digital thermometer into the probe insertion hole of the heating device and make it contact the rod-shaped sample being tested; connect the signal output terminal of the digital thermometer to the host computer. Set the target temperature for the heating device and turn on the heating to slowly raise the temperature of the sample from room temperature. Throughout the heating process, the host computer continuously reads the voltage data from the voltage acquisition module and the temperature measurement results output by the digital thermometer at a fixed sampling period, and stores them. The linear expansion coefficient of the tested rod-shaped sample was calculated based on the voltage data and temperature measurement results.

[0018] According to one embodiment of this application, the calculation of the linear expansion coefficient of the tested rod-shaped sample based on voltage data and temperature measurement results specifically includes: Based on the temperature sampling points, the average voltage data of N adjacent voltage data points are grouped and averaged to obtain the average voltage at each temperature; Substitute the average voltage into the calibration formula to convert it into the length change ΔL; Plot a curve with temperature T as the abscissa and ΔL as the ordinate, and perform linear fitting to obtain the fitting slope s; Calculate the linear expansion coefficient based on the fitted slope s. α = s / L 0, L 0 represents the initial length of the rod-shaped sample being tested.

[0019] Compared with existing technologies, the beneficial effects of adopting the above technical solution are as follows: (1) The measurement accuracy is significantly improved: the displacement resolution can reach the micrometer level by using a magnetostrictive displacement sensor; the effective number of digits of the temperature reading can reach 4 by using a platinum resistance digital thermometer; the relative error of the measured coefficient of thermal expansion of aluminum, iron and brass is about 0.03%, which is far lower than the error level of 3%-7% of the traditional method.

[0020] (2) Synchronous and continuous temperature-displacement measurement: The present invention realizes synchronous acquisition and continuous recording of displacement and temperature through the host computer, which can obtain a complete temperature-length change curve, avoiding the shortcomings of traditional methods that can only sample at discrete temperature points.

[0021] (3) High degree of automation: Through automatic processing and fitting by the host computer, the experimenters do not need to manually read and calculate, which greatly reduces human subjective error and improves experimental efficiency.

[0022] (4) Expandable structure and good adaptability: By using a 3D printed high-precision bracket, the magnetostrictive displacement sensor can be easily adapted to samples of different sizes and materials and different types of heating devices, which enhances the versatility of the system.

[0023] (5) Wide range of applications: It is not only applicable to conventional metal materials, but also successfully applied to the measurement of the linear expansion coefficient of non-metallic materials such as wood and engineering plastics, providing new experimental methods for related material research.

[0024] (6) Moderate cost and easy to promote: While maintaining high measurement performance, the structure of the device of the present invention is relatively simple, which makes it easy to promote and apply in universities and research institutes. Attached Figure Description

[0025] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0026] Figure 1 This is a schematic diagram of the overall structure of the high-precision measurement device for the coefficient of linear expansion of a solid based on magnetostrictive displacement sensing, according to an embodiment of this application.

[0027] Figure 2 This is a front view of the heating device according to an embodiment of this application.

[0028] Figure 3 This is a schematic diagram of the magnetostrictive displacement sensor and high-precision bracket structure according to an embodiment of this application.

[0029] Figure 4 This is a flowchart of the measurement method according to an embodiment of this application.

[0030] Figure 5 This is a comparison chart of the measurement method of this application embodiment and the measurement results of a traditional dial indicator. Detailed Implementation

[0031] The embodiments of this application are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar modules or modules having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application. Rather, the embodiments of this application include all variations, modifications, and equivalents falling within the spirit and scope of the appended claims.

[0032] This application proposes a high-precision measurement device for the coefficient of linear expansion of solids based on magnetostrictive displacement sensing. By improving the temperature measurement method, introducing a high-resolution magnetostrictive displacement sensor, designing a high-precision support, and implementing a host computer program, it achieves high-precision, automated, and repeatable measurement of the coefficient of linear expansion of test samples within a certain temperature range. It mainly addresses the following problems existing in the prior art: (1) The temperature delay is large and the true temperature of the sample is difficult to obtain accurately; (2) Relying on manual readings results in large errors and low efficiency; (3) It is difficult to achieve synchronous and continuous acquisition of temperature and displacement; (4) Problems such as poor compatibility with new sensors and limited measurement accuracy.

[0033] For details, please refer to Figure 1 This high-precision measurement device for the coefficient of linear expansion of solids based on magnetostrictive displacement sensing includes a heating device, a magnetostrictive displacement sensor, a high-precision bracket, a digital thermometer, and a host computer. The heating device is used to accommodate and heat the rod-shaped sample under test, and it has a pre-drilled probe insertion hole. The digital thermometer measures the real-time temperature of the rod-shaped sample and uploads the temperature measurement results to the host computer. The temperature probe of the digital thermometer is inserted into the probe insertion hole of the heating device and contacts the rod-shaped sample to complete the temperature measurement. The magnetostrictive displacement sensor is fixed to the outside of the heating device, with its probe rod coaxially contacting the end of the rod-shaped sample. It measures the elongation of the sample during heating and outputs voltage data representing the elongation to the host computer. The high-precision bracket is used to fix the magnetostrictive displacement sensor, ensuring that the sensor and the sample are axially concentric, and applies preload. The host computer receives the temperature measurement results and the elongation measurement results and calculates the coefficient of linear expansion.

[0034] Please refer to Figure 1 , Figure 2 The heating device mainly includes a housing, a sample holder, and a heating coil. The housing is a cylindrical cavity structure with a sample insertion hole at the center of one end for inserting a rod-shaped sample to be tested, and a probe insertion hole in the middle for inserting a temperature probe. The sample holder is located inside the housing to support the rod-shaped sample, ensuring that the sample is aligned with the axis of the housing. The heating coil surrounds the sample holder and heats the rod-shaped sample within it.

[0035] In this embodiment, the heating device includes multiple heating coils arranged around the sample holder, with a preset interval between each heating coil.

[0036] In one embodiment, the sample holder is a cross-shaped holder when viewed from the front, with a central opening for mounting the rod-shaped sample to be tested.

[0037] Please continue to refer to this. Figure 1 To ensure the measurement accuracy of the magnetostrictive displacement sensor, in one embodiment, an expansion length transmission rod is also provided. After the rod-shaped sample to be measured is inserted into the housing, the expansion length transmission rod is inserted into the sample insertion hole and comes into contact with the rod-shaped sample. Then, the measuring rod of the magnetostrictive displacement sensor comes into contact with the expansion length transmission rod, and the displacement of the expansion length transmission rod is the expansion length of the rod-shaped sample to be measured.

[0038] It should be noted that this high-precision solid linear expansion coefficient measuring device also includes a voltage acquisition module. The input terminal of the voltage acquisition module is connected to the signal terminal of the magnetostrictive displacement sensor to receive continuous analog voltage signals. The output terminal of the voltage acquisition module is connected to the host computer to upload the acquired voltage data. The voltage data characterizes the elongation of the measured rod-shaped sample. Both the magnetostrictive displacement sensor and the voltage acquisition module are provided with a stable DC voltage by a power supply module.

[0039] Please refer to Figure 3 In this embodiment, the high-precision support is fabricated through 3D modeling and 3D printing, and includes a base, a column, and a clamp. The column is a height-adjustable structure fixed to the base; the clamp is located on top of the column and is used to hold the magnetostrictive sensor. After the magnetostrictive sensor is installed, the end of the sensor's probe contacts the end face of the expansion length transmission rod, and a predetermined pressure is applied via the clamp. Ultimately, the high-precision support achieves axial concentricity and proper pre-pressure contact between the sensor and the sample.

[0040] A high-precision bracket ensures that the displacement sensor measures the true elongation of the sample along the axial direction, reducing additional errors caused by friction and assembly.

[0041] In one embodiment, the magnetostrictive displacement sensor is implemented using a waveguide wire and a cursor magnet structure, and its signal line is connected to a voltage acquisition module, which is connected to a host computer via RS485-USB.

[0042] In one embodiment, the digital thermometer is a platinum resistance digital thermometer, with its probe inserted inside the heating device, as close as possible to the sample, to achieve high-precision measurement of the sample temperature. The temperature measurement result is output digitally and can be transmitted to a host computer via an RS232 interface. The digital thermometer probe is inserted into the heating chamber and positioned close to the sample, enabling real-time monitoring of the actual sample temperature and significantly reducing the delay error between the displayed temperature and the sample temperature.

[0043] The host computer has pre-installed data acquisition and processing software, which can be implemented using existing software. Its implementation principle is not the focus of this invention and will not be elaborated upon here. The host computer acquires the voltage data output by the magnetostrictive displacement sensor through the voltage acquisition module, and simultaneously obtains the temperature measurement results from the digital thermometer, achieving synchronous displacement-temperature acquisition, real-time display, and storage.

[0044] Finally, the host computer uses dual serial port communication to synchronously acquire displacement voltage and temperature data. The linear expansion coefficient of the sample can then be calculated using the acquired voltage data and temperature measurement results. This involves the following steps: (1) Based on the temperature sampling points, group the adjacent N voltage data and calculate the average value of the voltage at each temperature; (2) Substitute the average voltage into the calibration formula to convert it into the length change ΔL.

[0045] For a magnetostrictive sensor, when a pulsed current propagates along the magnetostrictive waveguide and forms a helical magnetic field with the cursor magnet, a torsional wave is generated at the position of the cursor magnet. This torsional wave propagates at a constant speed and induces a voltage at the detection coil. The displacement ΔL can be obtained by measuring the time difference between the starting and ending pulses. In the actual device, the time difference is converted into an analog voltage output V proportional to the displacement through the sensor's internal electronic circuitry, satisfying:

[0046] in, k 1. k 0 represents the coefficient obtained through calibration.

[0047] Substituting the calculated average voltage into the above formula yields the change in length.

[0048] (3) Plot a curve with temperature T as the abscissa and ΔL as the ordinate, and perform linear fitting to obtain the fitting slope s.

[0049] (4) Calculate the linear expansion coefficient based on the fitted slope s. α = s / L 0, L 0 represents the initial length of the rod-shaped sample being tested.

[0050] In the above calculation process, to suppress random noise in voltage acquisition, this invention performs a certain calculation on the displacement data Δ for each temperature sampling point. L ( ΔL The average elongation at a given temperature is obtained by averaging the output voltage of the displacement sensor (after calibration and conversion). Then, a linear fit is performed with temperature as the abscissa and length change as the ordinate. Finally, the slope of the fitted line is divided by the initial length to obtain the coefficient of linear expansion of the rod-shaped sample under test.

[0051] To further illustrate the effectiveness of the high-precision measurement device for the coefficient of linear expansion of solids based on magnetostrictive displacement sensing proposed in this application, this embodiment further provides a measurement method based on the device, taking the rod-shaped sample to be tested as a brass metal sample. Figure 4 As shown, the specific measurement steps are as follows: (1) Setup of the device First, fix the heating device and insert one end of the metal sample into the heating device, leaving the other end as the free expansion end. Initial length of the metal sample. L 0 = 0.4 m.

[0052] Then, insert the expansion length transfer rod into the heating device, so that one end of it contacts the free expansion end of the metal sample, and the other end protrudes outside the heating device.

[0053] Next, the magnetostrictive displacement sensor is fixed to the outside of the heating device by a high-precision bracket, so that the end of the sensor probe contacts the expansion length transmission rod, and the preload of the sensor probe and the expansion length transmission rod is adjusted by the clamp on the high-precision bracket; the signal output terminal of the magnetostrictive displacement sensor is connected to the host computer through a voltage acquisition module.

[0054] Finally, insert the probe of the digital thermometer into the probe insertion hole of the heating device and bring it into contact with the metal sample. During insertion, place the probe as close as possible to the center of the metal sample to improve the representativeness of the sample temperature. Simultaneously, connect the signal output of the digital thermometer to the host computer.

[0055] The installation is now complete.

[0056] (2) Device calibration At room temperature, the metal sample was kept unheated, and the sensor output voltage was recorded. V 0.

[0057] Using a standard displacement device or a displacement platform with a known range, apply several known displacements to the sensor, obtain the corresponding voltage values, and fit the data to obtain the calibration formula. .

[0058] (3) Measurement steps The host computer is started to acquire data and display curves in real time. Specifically, the target temperature of the heating device is set, and heating is started to slowly raise the sample temperature from room temperature. Throughout the heating process, the host computer continuously reads and stores the voltage data from the voltage acquisition module and the temperature measurement results output by the digital thermometer at fixed sampling intervals.

[0059] Next, the linear expansion coefficient of the tested rod-shaped sample can be calculated based on the voltage data and temperature measurement results. Specifically, firstly, based on the temperature sampling points, the average voltage values ​​of N adjacent voltage data points are grouped and averaged to obtain the average voltage value at each temperature. Then, the average voltage value is substituted into the calibration formula to convert it into the length change ΔL. Next, a curve is plotted with temperature T as the abscissa and ΔL as the ordinate, and linear fitting is performed to obtain the fitting slope s. Finally, the linear expansion coefficient is calculated based on the fitting slope s. α = s / L 0, L 0 represents the initial length of the rod-shaped sample being tested.

[0060] By using the above-mentioned measuring device and method, repeated measurements were performed on metal samples such as aluminum, iron, and brass. The obtained coefficients of linear expansion were very close to the theoretical values. The relative errors of aluminum, iron, and brass were about 0.03%, which is lower than the 3%–7% of the traditional dial indicator method.

[0061] Based on the aforementioned setup, only the sample to be tested is replaced with a non-metallic sample, such as wood (e.g., pine) or engineering plastic (e.g., polyoxymethylene). The measurement steps remain the same: the non-metallic sample is prepared into a rod-shaped specimen approximately 0.4 m in length and placed in the heating chamber; the magnetostrictive displacement sensor contacts the end of the rod-shaped sample through a high-precision bracket and an expansion length transmission rod; the same host computer program is used to achieve synchronous and continuous acquisition of displacement and temperature; and the average linear expansion coefficient within the set temperature range is calculated through multi-point averaging and linear fitting.

[0062] Figure 5 The diagram shows a comparison between the measurement method of this embodiment and the measurement results of a traditional dial indicator. The experiment shows that the device proposed in this invention can stably measure the linear expansion coefficient of non-metallic materials such as pine wood and polyoxymethylene, and the deviation of repeated experiments is small, which verifies the applicability of this device in the measurement of non-metallic and flexible materials.

[0063] It should be noted that, in the description of the embodiments of the present invention, unless otherwise explicitly specified and limited, the terms "set" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the present invention based on the specific circumstances. The accompanying drawings in the embodiments are used to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0064] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A high-precision measuring device for the coefficient of linear expansion of a solid based on magnetostrictive displacement sensing, characterized in that, Includes heating device, magnetostrictive displacement sensor, high-precision bracket, digital temperature measuring instrument, and host computer; The heating device is used to hold the rod-shaped sample to be tested and to heat it at a controlled temperature; the heating device is provided with a probe insertion hole and a sample insertion hole; The digital thermometer is used to measure the real-time temperature of the rod-shaped sample being tested and upload the temperature measurement results to the host computer; the temperature probe of the digital thermometer is inserted into the probe insertion hole of the heating device and comes into contact with the rod-shaped sample being tested to complete the temperature measurement. The magnetostrictive displacement sensor is fixed to the outside of the heating device, so that the sensor rod is in coaxial contact with the end of the rod-shaped sample being tested. It is used to measure the elongation of the rod-shaped sample being tested during the heating process and output voltage data characterizing the elongation to the host computer. The high-precision bracket is used for the magnetostrictive displacement sensor to ensure that the magnetostrictive displacement sensor is axially concentric with the rod-shaped sample being measured, and to apply preload. The host computer receives the temperature measurement results and the elongation measurement results, and calculates the coefficient of linear expansion.

2. The high-precision measuring device for the coefficient of linear expansion of a solid based on magnetostrictive displacement sensing according to claim 1, characterized in that, The heating device includes a housing, a sample holder, and a heating coil. The housing is a cylindrical cavity structure. A sample insertion hole is provided at the center of one end of the housing for inserting a rod-shaped sample to be tested. A probe insertion hole is provided in the middle of the housing for inserting a temperature measuring probe. The sample holder is disposed inside the housing to support the rod-shaped sample to be tested, so that the rod-shaped sample is positioned on the axis of the housing. The heating coil is arranged around the sample holder to heat the rod-shaped sample to be tested in the sample holder.

3. The high-precision measuring device for the coefficient of linear expansion of a solid based on magnetostrictive displacement sensing according to claim 2, characterized in that, The heating device includes multiple heating coils arranged around the sample holder, with a preset interval between each heating coil.

4. The high-precision measuring device for the coefficient of linear expansion of a solid based on magnetostrictive displacement sensing according to claim 2, characterized in that, It also includes an expansion length transmission rod; after the rod-shaped sample to be tested is inserted into the housing, the expansion length transmission rod is inserted into the sample insertion hole and comes into contact with the rod-shaped sample to be tested, and the measuring rod of the magnetostrictive displacement sensor then comes into contact with the expansion length transmission rod; the displacement of the expansion length transmission rod is the expansion length of the rod-shaped sample to be tested.

5. The high-precision measuring device for the coefficient of linear expansion of a solid based on magnetostrictive displacement sensing according to claim 1, characterized in that, It also includes a voltage acquisition module, the input end of which is connected to the signal end of the magnetostrictive displacement sensor to receive continuous analog voltage signals; the output end of the voltage acquisition module is connected to the host computer to upload the acquired voltage data; the voltage data characterizes the elongation of the tested rod-shaped sample.

6. The high-precision measuring device for the coefficient of linear expansion of a solid based on magnetostrictive displacement sensing according to claim 1, characterized in that, The high-precision bracket is fabricated through 3D modeling and 3D printing, and includes a base, a column, and a clamp. The column is a height-adjustable structure and is fixed on the base. The clamp is located on the top of the column and is used to hold the magnetostrictive sensor. After the magnetostrictive sensor is installed, the end of the probe of the magnetostrictive sensor contacts the end face of the expansion length transmission rod, and a predetermined pressure is set by the clamp.

7. The high-precision measuring device for the coefficient of linear expansion of a solid based on magnetostrictive displacement sensing according to claim 5, characterized in that, The process of obtaining and calculating the coefficient of linear expansion by the host computer includes: Acquire temperature measurement results and voltage data; Based on the temperature sampling points, the average voltage data of N adjacent voltage data points are grouped and averaged to obtain the average voltage at each temperature; Substitute the average voltage into the calibration formula to convert it into the length change ΔL; Plot a curve with temperature T as the abscissa and ΔL as the ordinate, and perform linear fitting to obtain the fitting slope s; Calculate the linear expansion coefficient based on the fitted slope s. α = s / L 0, L 0 represents the initial length of the rod-shaped sample being tested.

8. The high-precision measuring device for the coefficient of linear expansion of a solid based on magnetostrictive displacement sensing according to claim 7, characterized in that, The calibration formula acquisition process includes: At room temperature, the rod-shaped sample to be tested is kept unheated, and the sensor output voltage is recorded. Using a standard displacement device or a displacement platform with a known range, several known displacements are applied to the magnetostrictive sensor, and the corresponding voltage values ​​are obtained. The calibration formula is obtained by fitting the known displacements with the corresponding voltage values.

9. A measurement method based on the high-precision measuring device for the coefficient of linear expansion of a solid based on magnetostrictive displacement sensing as described in any one of claims 1 to 8, characterized in that, include: One end of the rod-shaped sample to be tested is inserted into the heating device and fixed, while the other end serves as the free expansion end; the rod-shaped sample to be tested can be a solid metal sample or a non-metal sample. Next, insert the expansion length transfer rod into the heating device, so that one end of it contacts the free expansion end of the rod-shaped sample being tested, and the other end protrudes outside the heating device; The magnetostrictive displacement sensor is fixed to the outside of the heating device using a high-precision bracket, so that the end of the sensor probe contacts the expansion length transmission rod. The preload of the sensor probe and the expansion length transmission rod is adjusted by the clamp on the high-precision bracket. The signal output terminal of the magnetostrictive displacement sensor is connected to the host computer through a voltage acquisition module. Insert the probe of the digital thermometer into the probe insertion hole of the heating device and make it contact the rod-shaped sample being tested; connect the signal output terminal of the digital thermometer to the host computer. Set the target temperature for the heating device and turn on the heating to slowly raise the temperature of the sample from room temperature. Throughout the heating process, the host computer continuously reads the voltage data from the voltage acquisition module and the temperature measurement results output by the digital thermometer at a fixed sampling period, and stores them. The linear expansion coefficient of the tested rod-shaped sample was calculated based on the voltage data and temperature measurement results.

10. The measurement method according to claim 9, characterized in that, The calculation of the linear expansion coefficient of the tested rod-shaped sample based on voltage data and temperature measurement results specifically includes: Based on the temperature sampling points, the average voltage data of N adjacent voltage data points are grouped and averaged to obtain the average voltage at each temperature; Substitute the average voltage into the calibration formula to convert it into the length change ΔL; Plot a curve with temperature T as the abscissa and ΔL as the ordinate, and perform linear fitting to obtain the fitting slope s; Calculate the linear expansion coefficient based on the fitted slope s. α = s / L 0, L 0 represents the initial length of the rod-shaped sample being tested.

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