一种芯棒的压缩弹性模量测试装置及方法

Abstract

本发明属于压缩弹性模量测试技术领域，涉及一种芯棒的压缩弹性模量测试装置，包括试验机和放置在试验机上的压缩变形测量装置；压缩变形测量装置包括由上至下依次连接的上支撑杆、载物台和下支撑杆，载物台包括下基座、上基座和连接杆，上基座和连接杆连接；在下基座上安装有两个光栅尺，两个光栅尺连接测控系统；上支撑杆安装在上基座内，在上支撑杆内安装有可移动加载体，在可移动加载体内开有圆柱孔，在圆柱孔的底端开有半球形孔，在半球形孔内安装有平衡球；在圆柱孔内安装有加载杆，加载杆的上端伸出可移动加载体，加载杆的下端开有半球形孔，两个半球形孔形成用于容纳平衡球的空间。解决了目前压缩弹性模量测试准确度低和结果偏差大的问题。

Description

Technical Field

[0001] This invention belongs to the field of compressive modulus testing technology, specifically relating to a mandrel compressive modulus testing device and method. Background Technology

[0002] Although porcelain or glass insulators have been used in high-voltage external insulation for many years, with the increase in voltage levels, the electromechanical load on the insulators has increased, and air pollution has intensified, revealing inherent performance defects in porcelain or glass insulators during use. To overcome the inherent shortcomings of porcelain or glass insulators, improve the wet-pollution flashover voltage of insulators, and reduce the inconvenience of transportation and installation, composite insulators have seen rapid development in recent years, especially in areas with high pollution levels, where they are widely used due to their advantages such as light weight, high strength, ease of installation, and no need for zero-value testing.

[0003] The core rod is the main component of the composite insulator that bears the mechanical load. Its quality and mechanical strength have a great impact on the life of the composite insulator. Therefore, the mechanical strength parameters of the core rod are the key to evaluating the performance of the composite insulator. These parameters generally include tensile strength, bending strength, hot bending strength, shear strength, etc., as well as their corresponding tensile elastic modulus, bending elastic modulus, and compressive elastic modulus.

[0004] Currently, the accuracy of compressive modulus measurement in the insulator industry is low, with measured data exhibiting significant fluctuations and a wide range of values. Existing technology commonly uses a testing machine in conjunction with displacement measuring instruments to measure the compressive modulus. These testing machines are often common universal testing machines or electronic universal testing machines. Compression deformation is typically measured using a micrometer or supplemented by load-displacement curves recorded by the testing machine itself, and the compressive modulus is obtained through a calculation formula. For measuring the compressive modulus, the two most critical measurements are the compression load increment and the compression deformation. Currently, the measurement of compression load is relatively mature; aside from differences in the accuracy class of the testing machine itself, both hydraulic and electronic loading systems are generally reliable and mature in measuring compression load. Therefore, the greatest challenge in measuring the compressive modulus lies in measuring the compression deformation.

[0005] According to GB / T1448-2005, the instrument for measuring deformation should be placed at the midpoint of the specimen height. The specimen and deformation measurement system should be checked and adjusted to ensure the entire system is in normal working order and that the compression deformation on both sides of the specimen is relatively consistent. For mandrel materials, the compressive modulus of elasticity testing is challenging because the compressive deformation within the elastic range is extremely small, making accurate measurement difficult and subject to numerous influencing factors. These include the parallelism of the upper and lower ends of the specimen (requiring a value less than 0.1% of the specimen height), the alignment of the specimen's centerline with the centers of the upper and lower pressure plates of the testing machine, and the consistency of compression deformation on both sides of the specimen. Based on the material properties of the mandrel, the compressive modulus of elasticity is on the order of tens of GPa, while the compression deformation within the elastic range is on the order of micrometers. Since the thousandths place of a micrometer is an estimated value and not entirely accurate, a large measurement error in the compressive deformation will lead to a larger error in the calculated compressive modulus, potentially resulting in erroneous measurements. Therefore, the main drawbacks of current technology are low reliability and low accuracy in measuring compressive deformation.

[0006] It can be seen that the low accuracy and large deviation of the compressive modulus test are mainly due to two factors:

[0007] 1) Compared with the upper and lower pressure plates of general electronic universal material testing, the sample size is smaller, making it difficult to directly measure the compression deformation of the mandrel between the upper and lower pressure plates;

[0008] 2) The compression deformation of the mandrel is extremely small, resulting in low measurement accuracy. Summary of the Invention

[0009] The purpose of this invention is to provide a device and method for testing the compressive modulus of a mandrel, which solves the problems of low accuracy and large deviation in current compressive modulus testing.

[0010] This invention is achieved through the following technical solution:

[0011] A device for testing the compressive modulus of a mandrel, comprising a testing machine and a compression deformation measuring device placed on the testing machine;

[0012] The compression deformation measuring device includes an upper support rod, a stage, and a lower support rod connected from top to bottom. The stage includes a lower base, an upper base, and a connecting rod. The upper base and the connecting rod are connected. The sample to be measured is placed on the lower base. A first grating ruler and a second grating ruler are symmetrically arranged on the lower base. The first grating ruler and the second grating ruler are connected to a measurement and control system.

[0013] The upper support rod is installed inside the upper base. A movable loading body is installed inside the upper support rod. A cylindrical hole is opened inside the movable loading body. A hemispherical hole is opened at the bottom end of the cylindrical hole. A balance ball is installed inside the hemispherical hole.

[0014] A loading rod is installed inside the cylindrical hole. The upper end of the loading rod extends out of the movable loading body, and the lower end of the loading rod has a hemispherical hole. The two hemispherical holes form a space to accommodate the balance ball.

[0015] Furthermore, the testing machine adopts an electronic universal testing machine.

[0016] Furthermore, the testing machine includes a main frame, a movable loading beam, an upper pressure plate, and a lower pressure plate. The movable loading beam is located at the upper end of the main frame, the upper pressure plate is fixedly connected to the lower part of the movable loading beam, and the lower pressure plate is fixedly connected to the lower part of the main frame.

[0017] The lower support rod is coaxially connected to the lower pressure plate.

[0018] Furthermore, a locking locating ring for locking the loading rod is installed at the top of the cylindrical hole.

[0019] Furthermore, the locking positioning ring is a stepped rod, with a through hole inside the stepped rod having the same outer diameter as the loading rod.

[0020] Furthermore, the movable loading body includes a cylindrical rod and a handle, with the handle extending laterally through the lower end of the cylindrical rod;

[0021] The handle is located between the upper base and the lower base.

[0022] Furthermore, both the upper and lower bases are discs.

[0023] Furthermore, there are four connecting rods, two of which are located on one side of the lower base and the other two are located on the other side of the lower base. The probe of the first grating ruler is located between two of the connecting rods, and the probe of the second grating ruler is located between the other two connecting rods.

[0024] Furthermore, three circles of unequal diameters are prefabricated on the upper surface of the lower base.

[0025] A method for testing the compressive elastic modulus of a mandrel, comprising the following steps:

[0026] Step 1: Shake the loading rod to ensure good contact between the loading rod, the balance ball and the hemispherical hole at the bottom of the cylindrical hole. Then place the compression deformation measuring device on the testing machine, ensuring that the compression deformation measuring device is aligned with the center of the testing machine, and connect the transmission lines of the first and second grating rulers to the measurement and control system.

[0027] Step 2: Turn on the testing machine, lift the movable loading body upwards, place the mandrel sample at the center of the lower base, and lower the movable loading body until the bottom end of the movable loading body contacts the upper surface of the mandrel. At this time, the bottom end of the movable loading body contacts the measuring ends of the first and second grating rulers.

[0028] Turn on the measurement and control system and start measuring the compressive elastic modulus. The compressive load is transmitted to the loading rod, which is then transmitted to the movable loading body via the balance ball. At this time, the compressive load is finally applied to the mandrel sample through the movable loading body. When the two ends of the mandrel sample are not parallel, the balance ball ensures that the compression direction is always in the same direction as the axis of the mandrel sample.

[0029] The test of compressive modulus consists of two steps:

[0030] Step 1: Measure and record the compressive failure load value of the mandrel specimen;

[0031] Step 2: After placing other mandrel samples prepared in the same batch, the testing machine starts loading and applies the initial load. At this time, the initial values ​​of the first and second grating rulers are cleared to zero, and the compression load is increased until the applied compression load increases to 50% of the compression failure load value. Then, the compression load is stopped, and the values ​​of the two grating rulers are measured. The compression deformation is the average value of the two grating rulers, and the measurement and control system automatically obtains the compression elastic modulus.

[0032] Compared with the prior art, the present invention has the following beneficial technical effects:

[0033] This invention provides a device for testing the compressive modulus of a mandrel. The compression deformation measuring device includes an upper support rod, a stage, and a lower support rod connected sequentially from top to bottom. A cylindrical hole is formed within a movable loading body, and a hemispherical hole is formed at the bottom end of the cylindrical hole. A balance ball is installed inside the hemispherical hole. A loading rod is installed inside the cylindrical hole, with its upper end extending out of the movable loading body and its lower end forming a hemispherical hole. The two hemispherical holes form a space to accommodate the balance ball. When the two ends of the sample are slightly non-parallel, the automatic adjustment function of the balance ball ensures that the compressive load passes through the axis of the mandrel, effectively avoiding the influence of eccentricity and ensuring that the mandrel sample is axially compressed. This reduces measurement deviation problems caused by high parallelism, significantly improving test stability and reliability. Furthermore, it is convenient, fast, and efficient to use. If no adjustment is made, the compressive load deviates from the centerline of the sample, which may cause the sample to shift, making the test unreliable.

[0034] Because the mandrel sample size is too small and the upper and lower pressure plates of the testing machine are too large, this invention applies pressure through the design of a loading rod. The cross-sectional area of ​​the loading rod is not much different from the size of the mandrel sample, which can reduce the eccentricity problem caused by the misalignment of the compression load direction with the center of the mandrel sample during the test, thus reducing measurement deviation.

[0035] Traditionally, deformation is measured on one side of the specimen, without requiring measurement of deformation on both sides. This invention designs two grating rulers on the lower base, symmetrically distributed left and right. The compressive deformation is taken as the average of the sum of the two grating rulers, further reducing the measurement error of compressive deformation. This effectively reduces the problem of large single-sided measurement error in existing technologies, which leads to further amplification of the error in compressive elastic modulus. Moreover, the grating rulers have an accuracy of 0.03 micrometers, which greatly improves the measurement accuracy of small deformations and allows for real-time monitoring of the compressive deformation on both sides of the specimen, ensuring the accuracy of the testing process.

[0036] This invention features an ingeniously designed compression deformation measuring device. Its components work closely together to not only fully meet the requirements of existing standards but also further reduce the interference and impact of various uncertainties in the experimental measurement on the results. Highly practical and versatile, this measuring device can not only test the compressive modulus of a mandrel but also perform small deformation tests on other material samples (such as various types of ceramics and epoxy resins).

[0037] Furthermore, the lower base has three circular lines of unequal diameter at its center, which facilitates placing the test sample in the center. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the assembly structure of a mandrel compression modulus testing device according to the present invention;

[0039] Figure 2 This is a schematic diagram of the structure of an electronic universal testing machine;

[0040] Figure 3 This is a schematic diagram of the main structure of the compression deformation measuring device;

[0041] Figure 4 for Figure 3 Perspective view;

[0042] Figure 5 for Figure 3 Exploded view;

[0043] Figure 6 This is a schematic diagram of the structure of a movable loading body;

[0044] Figure 7 This is a schematic diagram of the loading rod structure;

[0045] Figure 8 This is a schematic diagram of the locking diameter positioning ring.

[0046] Among them, 1 is the loading rod, 2 is the locking diameter positioning ring, 3 is the movable loading body, 4 is the balance ball, 5 is the first grating ruler, 6 is the second grating ruler, 7 is the support rod, 8 is the main frame of the testing machine, 9 is the movable loading crossbeam, 10 is the upper pressure plate, 11 is the lower pressure plate, 12 is the measurement and control system, 13 is the mandrel sample, 14 is the lower base, 15 is the connecting rod, and 16 is the upper base;

[0047] 71 is the upper support rod, and 72 is the lower support rod;

[0048] 31 is a cylindrical rod, 32 is a handle, 33 is a cylindrical hole, and 34 is a hemispherical hole. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of the present invention clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention; that is, the described embodiments are only a part of the embodiments of the present invention, and not all of them.

[0050] The components described and illustrated in the accompanying drawings and embodiments of this invention can be arranged and designed in various different configurations. Therefore, the detailed description of the embodiments of the invention provided in the following drawings is not intended to limit the scope of the claimed invention, but merely to illustrate one selected embodiment of the invention. All other embodiments obtained by those skilled in the art based on the accompanying drawings and embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0051] It should be noted that the terms "comprising," "including," or any other variations are intended to cover non-exclusive inclusion, such that a process, element, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to the process, element, method, article, or apparatus. Furthermore, the terms "horizontal" and "vertical" are based on the orientation and positional relationship of the devices or components shown in the accompanying drawings and are used only for better description of the invention, not to require that the shown devices, components, or apparatus must have that specific orientation, and therefore should not be construed as limiting the invention.

[0052] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0053] like Figure 1As shown, this invention discloses a device for testing the compressive elastic modulus of a mandrel, including a testing machine and a compression deformation measuring device placed on the testing machine; the testing machine is an electronic universal testing machine, which is not much different from mainstream material testing machines on the market, and is equipped with a computer automatic measurement system, including grating ruler data acquisition, which can automatically load compression load, collect test data and perform automatic calculations according to the set program.

[0054] The main structure of the testing machine is as follows Figure 2 As shown, the testing machine includes a main frame 8, a movable loading beam 9, an upper pressure plate 10, and a lower pressure plate 11. The movable loading beam 9 is located at the upper end of the main frame 8, the upper pressure plate 10 is fixedly connected to the lower part of the movable loading beam 9, and the lower pressure plate 11 is fixedly connected to the lower part of the main frame 8.

[0055] like Figures 3-7 As shown, the compression deformation measuring device includes an upper support rod 71, a stage, and a lower support rod 72 connected sequentially from top to bottom. The stage includes a lower base 14, an upper base 16, and a connecting rod 15. The lower base 14 and the upper base 16 are connected by the connecting rod 15. The sample to be tested is placed on the lower base 14. A first grating ruler 5 and a second grating ruler 6 are symmetrically arranged on the lower base 14. The first grating ruler 5 and the second grating ruler 6 are connected to a measurement and control system 12. The upper support rod 71 is installed inside the upper base 16, and a movable loading body 3 is installed inside the upper support rod 71. Figure 6 As shown, a cylindrical hole 33 is formed inside the movable loading body 3, and a hemispherical hole 34 is formed at the bottom end of the cylindrical hole 33. A balance ball 4 is installed inside the hemispherical hole 34. A loading rod 1 is installed inside the cylindrical hole 33, and the upper end of the loading rod 1 extends out of the movable loading body 3, as shown. Figure 7 As shown, a hemispherical hole 34 is opened at the lower end of the loading rod 1, and the two hemispherical holes 34 form a space for accommodating the balance ball 4.

[0056] Introduction to the design functions of each component of the compression deformation measuring device:

[0057] Loading rod 1: Because the size of the mandrel sample 13 is too small and the upper and lower pressure plates 11 of the testing machine are too large, the present invention applies pressure through the design of the loading rod 1. The cross-sectional area of ​​the loading rod 1 is not much different from the size of the mandrel sample 13, which can reduce the eccentricity problem caused by the non-coincidence of the compression load direction with the center of the mandrel sample 13 during the test, and cause measurement deviation.

[0058] like Figure 8 As shown, the locking diameter positioning ring 2: limits the movement direction of the compression loading rod 1 and the adjusting balance ball 4, ensuring that the center of the compression load is strictly loaded in the same direction as the sample axis;

[0059] Balance ball 4: Utilizing the guiding effect of the spherical shape, when the upper and lower end faces of the sample are not parallel, the direction of the applied compressive force can be fully and moderately adjusted within a 360° sector with the axial direction as the center line. It can play a moderate adjustment role in all directions, so that the compression direction is always in the same direction as the sample axis.

[0060] The movable loading body 3: The upper part can be filled with the adjusting balance ball 4, the locking diameter positioning ring 2 and the compression loading rod 1 in sequence. The lower two ends have handles 32 that can be adjusted up and down. When the sample is installed, the movable handles 32 have space for adjustment up and down. When the sample is not parallel, it can be adjusted up and down by the movable handles 32 and adjusted left and right by the balance ball 4.

[0061] Furthermore, the two sides of the handle 32 are designed with an arc shape, which is intended to allow for front-to-back adjustment by adjusting the balance ball 4 when the two ends of the sample are not parallel. The lower surface is in contact with the upper surface of the mandrel sample 13 and the sensor probes of the two grating rulers;

[0062] Stage: such as Figure 4 As shown, there are three circular lines of unequal diameter at the center of the lower base 14, which facilitates placing the test sample in the center; there are four connecting rods 15, two of which are located on one side of the lower base 14 and the other two are located on the other side of the lower base 14. The probe of the first grating ruler 5 is located between two of the connecting rods 15, and the probe of the second grating ruler 6 is located between the other two connecting rods 15.

[0063] A space is left between the two connecting rods 15 to allow for the installation of the grating ruler, so that the grating ruler can directly measure the compression deformation at both ends of the mandrel.

[0064] The grating rulers consist of a first grating ruler (5) and a second grating ruler (6), which are symmetrically distributed left and right. This arrangement serves two purposes: firstly, it leverages the high precision of the grating rulers to address the problem of large measurement errors for small deformations; secondly, it allows for real-time monitoring of the compressive deformation on both sides of the sample, ensuring the accuracy of the test process and preventing measurement deviations caused by eccentricity. When the deviation in deformation on both sides is within a reasonable range, the compressive deformation is taken as the average of the sum of the values ​​from grating rulers 1 and 2.

[0065] The lower support rod 72 is a cylindrical rod 31, which is convenient to align with the center circle of the lower pressure plate 11 of the testing machine.

[0066] This invention designs a compression deformation testing device to be used with the mandrel sample 13, solving the problem of the smaller sample size compared to the upper and lower pressure plates 11 in electronic universal material testing. The advantages are that it ensures the mandrel sample 13 is completely axially compressed, avoiding measurement deviations caused by the parallelism of the upper and lower end faces of the sample, thus significantly improving test stability and reliability. Furthermore, the compression deformation testing device can directly measure the mandrel's compression deformation, solving the difficulty of directly measuring the mandrel's compression deformation between the upper and lower pressure plates 11, and avoiding errors caused by reduced clearance between external or tooling components when bearing compressive loads.

[0067] Two grating rulers with an accuracy of ±0.03μm are introduced to measure compressive deformation, solving the problem of large measurement errors for small deformations. The two grating rulers are symmetrically distributed left and right, allowing real-time monitoring of the compressive deformation on both sides of the sample, ensuring the accuracy of the test process and preventing measurement deviations caused by eccentricity. When the deviation of the deformation on both sides is within a reasonable range, the compressive deformation is taken as the average of the sum of grating ruler 1 and grating ruler 2, further reducing the measurement error of compressive deformation.

[0068] In the electronic universal material testing and control system 12, a program for calculating the compressive elastic modulus as specified in the standard has been developed. This program can automatically load the compressive load, collect force and deformation data, display the data curves in real time, and then automatically calculate the compressive elastic modulus result.

[0069] The specimen for measuring the compressive modulus of elasticity is typically a cuboid with dimensions of 10mm x 10mm x 30mm. The compressive modulus of elasticity is calculated by dividing the compressive stress under uniaxial compressive stress within the elastic deformation range by the compressive strain in that direction. The corresponding calculation formula is as follows:

[0070]

[0071] In the formula:

[0072] F – Compressive load, in N;

[0073] b—Sample width, in mm;

[0074] d—sample thickness, in mm;

[0075] E – compressive modulus, in MPa;

[0076] ΔF — Load increment on the initial straight segment of the load-deformation curve, in N;

[0077] ΔL — The deformation increment within the gauge length L0 corresponding to the load increment ΔF, in mm;

[0078] L0—gauge length in the compression direction of the specimen, in mm.

[0079] A method for testing the compressive elastic modulus of a mandrel, characterized by comprising the following steps:

[0080] Step 1: Shake the loading rod 1 to ensure good contact between the loading rod 1, the balance ball 4 and the hemispherical hole at the bottom of the cylindrical hole 33. Then place the compression deformation measuring device on the testing machine, ensuring that the compression deformation measuring device is aligned with the center of the testing machine, and connect the transmission lines of the first grating ruler 5 and the second grating ruler 6 to the measurement and control system 12.

[0081] Step 2: Turn on the testing machine, lift the movable loading body 3 upwards, place the mandrel sample at the center of the lower base 14, and lower the movable loading body 3 until the bottom end of the movable loading body 3 contacts the upper surface of the mandrel. At this time, the bottom end of the movable loading body 3 contacts the measuring ends of the first grating ruler 5 and the second grating ruler 6.

[0082] Turn on the measurement and control system 12 and start measuring the compressive elastic modulus. The compressive load direction is transmitted to the loading rod 1, and the loading rod 1 is transmitted to the movable loading body 3 through the balance ball 4. At this time, the compressive load is finally applied to the mandrel sample through the movable loading body 3. When the two ends of the mandrel sample are not parallel, the balance ball 4 is used to make the compression direction always in the same direction as the axis of the mandrel sample.

[0083] The test of compressive modulus consists of two steps:

[0084] Step 1: Measure the compressive failure load value of the mandrel specimen. At this time, it is not necessary to measure the compressive deformation. Record this failure load value.

[0085] Step 2: After placing other mandrel samples prepared in the same batch, the testing machine starts loading and applies an initial load (approximately 5% of the compression failure load measured in Part 1). At this time, the initial values ​​of the first grating ruler 5 and the second grating ruler 6 are reset to zero, and the compression load is continued to be increased until 50% of the compression failure load value measured in Part 1 is applied. The compression load is then stopped, and the values ​​of the two grating rulers are measured at this time. The compression deformation is taken as the average value of the two grating rulers, and the measurement and control system 12 automatically obtains the compression elastic modulus.

[0086] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A device for testing the compressive elastic modulus of a mandrel, characterized in that, Includes a testing machine and a compression deformation measuring device placed on the testing machine; The compression deformation measuring device includes an upper support rod (71), a stage, and a lower support rod (72) connected from top to bottom. The stage includes a lower base (14), an upper base (16), and a connecting rod (15). The upper base (16) and the connecting rod (15) are connected. The sample to be tested is placed on the lower base (14). A first grating ruler (5) and a second grating ruler (6) are symmetrically arranged on the lower base (14). The first grating ruler (5) and the second grating ruler (6) are connected to a measurement and control system (12). The upper support rod (71) is installed inside the upper base (16). A movable loading body (3) is installed inside the upper support rod (71). A cylindrical hole (33) is opened inside the movable loading body (3). A hemispherical hole (34) is opened at the bottom of the cylindrical hole (33). A balance ball (4) is installed inside the hemispherical hole (34). A loading rod (1) is installed inside the cylindrical hole (33). The upper end of the loading rod (1) extends out of the movable loading body (3), and the lower end of the loading rod (1) has a hemispherical hole (34). The two hemispherical holes (34) form a space for accommodating the balance ball (4). The movable loading body (3) includes a cylindrical rod (31) and a handle (32), with the handle (32) extending laterally through the lower end of the cylindrical rod (31); The handle (32) is located between the upper base (16) and the lower base (14); A locking diameter positioning ring (2) for locking the loading rod (1) is installed at the top of the cylindrical hole (33); the locking diameter positioning ring (2) is a stepped rod, and a through hole with the same outer diameter as the loading rod (1) is opened in the stepped rod. The lower surface of the handle (32) is in contact with the upper surface of the sample to be tested, the sensor probe of the first grating ruler (5), and the sensor probe of the second grating ruler (6).

2. The device for testing the compressive elastic modulus of a mandrel according to claim 1, characterized in that, The testing machine is an electronic universal testing machine.

3. The device for testing the compressive elastic modulus of a mandrel according to claim 1, characterized in that, The testing machine includes a main frame (8), a movable loading beam (9), an upper pressure plate (10), and a lower pressure plate (11). The movable loading beam (9) is located at the upper end of the main frame (8), the upper pressure plate (10) is fixedly connected to the lower part of the movable loading beam (9), and the lower pressure plate (11) is fixedly connected to the lower part of the main frame (8). The lower support rod (72) is coaxially connected to the lower pressure plate (11).

4. The device for testing the compressive elastic modulus of a mandrel according to claim 1, characterized in that, Both the upper base (16) and the lower base (14) are discs.

5. The device for testing the compressive elastic modulus of a mandrel according to claim 1, characterized in that, There are 4 connecting rods (15), 2 of which are located on one side of the lower base (14) and the other 2 are located on the other side of the lower base (14). The probe of the first grating ruler (5) is located between 2 of the connecting rods (15), and the probe of the second grating ruler (6) is located between the other 2 connecting rods (15).

6. The device for testing the compressive elastic modulus of a mandrel according to claim 1, characterized in that, Three circles of unequal diameters are pre-cast on the upper surface of the lower base (14).

7. A method for testing the compressive modulus of a mandrel based on the compressive modulus testing apparatus according to any one of claims 1-6, characterized in that, Includes the following steps: Step 1: Shake the loading rod (1) to ensure good contact between the loading rod (1), the balance ball (4) and the hemispherical hole at the bottom of the cylindrical hole (33). Then place the compression deformation measuring device on the testing machine, ensuring that the compression deformation measuring device is aligned with the center of the testing machine, and connect the transmission lines of the first grating ruler (5) and the second grating ruler (6) to the measurement and control system (12). Step 2: Open the testing machine, lift the movable loading body (3) upward, place the sample to be tested at the center of the lower base (14), and lower the movable loading body (3) until the bottom end of the movable loading body (3) contacts the upper surface of the sample to be tested. At this time, the bottom end of the movable loading body (3) contacts the measuring ends of the first grating ruler (5) and the second grating ruler (6). Turn on the measurement and control system (12) and start measuring the compressive elastic modulus. The compressive load direction is transmitted to the loading rod (1). The loading rod (1) is transmitted to the movable loading body (3) through the balance ball (4). At this time, the compressive load is finally applied to the sample to be tested through the movable loading body (3). When the two ends of the sample to be tested are not parallel, the compressive direction is always in the same direction as the axis of the sample to be tested by relying on the balance ball (4). The test of compressive modulus consists of two steps: Step 1: Measure and record the compressive failure load value of the sample to be tested; Step 2: After placing other samples prepared in the same batch into the test machine, the test machine starts to load and applies the initial load. At this time, the initial values ​​of the first grating ruler (5) and the second grating ruler (6) are cleared to zero. The compression load is increased until the applied compression load increases to 50% of the compression failure load value. Then the compression load is stopped. The values ​​of the two grating rulers are measured at this time. The compression deformation is the average value of the two grating rulers. The measurement and control system (12) automatically obtains the compression elastic modulus.

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