A step-by-step test method for measuring the Poisson's ratio of slender tubes at high temperatures

Abstract

The present invention is applicable to the fields of nuclear power and military technology, and provides a step-by-step test method for measuring the high-temperature Poisson's ratio of a slender tube, including step S10: setting and calculating a first room temperature radial parameter through a room temperature radial measurement device test; step S20: obtaining a second room temperature radial parameter through a high temperature radial measurement device test; step S30: obtaining a correction coefficient based on the first room temperature radial parameter and the second room temperature radial parameter; step S40: performing a high temperature test to obtain a radial parameter at a preset temperature, and correcting it based on the correction coefficient to obtain a corrected high temperature radial parameter; step S50: obtaining an axial elastic modulus at a preset temperature, and calculating the Poisson's ratio based on the axial elastic modulus and the corrected high temperature radial parameter. The present application splits the high temperature Poisson's ratio test of a slender tube into two independent tests through the concept of an intermediate variable, thereby solving the problem of the difficulty in efficiently and accurately measuring the Poisson's ratio at high temperatures.

Description

Technical Field

[0001] The invention relates to the fields of nuclear power and military industry, and in particular to a test method for measuring the high-temperature Poisson's ratio of a slender tube in a step-by-step manner. Background Art

[0002] Zirconium alloy slender tubes are widely used in nuclear power, military and other technical fields. They are an extremely important structural material. The safety and reliability of zirconium alloy slender tubes play an extremely important role in the normal operation of nuclear power plants, nuclear submarines, etc. Zirconium alloy slender tubes are usually used under high temperature conditions in the above-mentioned fields. Therefore, it is very necessary to accurately obtain the various mechanical parameters of zirconium alloy slender tubes under high temperature. However, Poisson's ratio is a parameter that has been highly valued by the industry in recent years. Now we need to find a simple, feasible and accurate method to test the Poisson's ratio of zirconium alloy slender tubes at high temperatures.

[0003] The difficulties in the high-temperature Poisson's ratio test of zirconium alloy slender tubes in the prior art are as follows:

[0004] (1) The lateral deformation of zirconium alloy slender tubes is relatively small, only a few microns, especially under high temperature conditions, and the measurement accuracy is low.

[0005] (2) During the high-temperature test of Poisson's ratio, it is difficult to install a high-temperature furnace and two high-temperature measuring devices at the same time.

[0006] (3) There is currently no high-precision high-temperature dual-axis measurement device on the market, and there is no way to directly measure the Poisson's ratio through a single test.

[0007] (4) The change of Poisson's ratio with temperature is very small. Usually, for every 100°C increase in temperature, the corresponding change of Poisson's ratio is 0.01-0.03. Therefore, if the measurement error of lateral strain and axial strain is slightly larger, the measured Poisson's ratio result will not reflect the impact of temperature change.

[0008] (5) Normally, high-temperature transverse (radial) measuring devices require extension measurements through high-temperature ceramic or glass rods. However, the installation process is greatly affected by human factors, and the results obtained each time are different. For example, the relative position of the measuring rod and the fixed rod in the length direction of the specimen changes, resulting in different measurement results. Summary of the invention

[0009] The purpose of the present invention is to provide a step-by-step test method for measuring the high-temperature Poisson's ratio of a slender tube to solve at least one of the above technical problems in the prior art, which mainly includes the following contents:

[0010] The present invention provides a test method for measuring the high-temperature Poisson's ratio of a slender tube in a step-by-step manner, which is characterized by comprising the following steps:

[0011] Step S10: setting and calculating a first room temperature radial parameter through a room temperature radial measurement device test;

[0012] Step S20: obtaining a second room temperature radial parameter by testing a high temperature radial measurement device;

[0013] Step S30: obtaining a correction coefficient according to the first room temperature radial parameter and the second room temperature radial parameter;

[0014] Step S40: performing a high temperature test to obtain radial parameters at a preset temperature, and correcting the radial parameters according to the correction coefficient to obtain corrected high temperature radial parameters;

[0015] Step S50: obtaining the axial elastic modulus at a preset temperature, and calculating the Poisson's ratio according to the axial elastic modulus and the corrected high-temperature radial parameter.

[0016] Furthermore, step S10 further includes:

[0017] A room temperature radial measuring device and a high-precision high temperature axial measuring device are installed on the slender tube, and an external force is applied to the slender tube by means of quasi-static force control;

[0018] Set radial parameters;

[0019] The first radial parameter at room temperature is obtained by continuously applying external force to the slender tube for multiple times.

[0020] Further, step S20 also includes:

[0021] The room temperature radial measuring device on the slender tube is removed, and a high temperature furnace is installed, and a high temperature radial measuring device and a high-precision thermocouple are installed;

[0022] The slender tube is subjected to continuous external force loading for multiple times, and the second radial parameter at room temperature is calculated.

[0023] Further, the room temperature radial measurement device test and the high temperature radial measurement device test are performed at the same temperature.

[0024] Furthermore, step S40 further includes:

[0025] Heat the high temperature furnace to a preset temperature;

[0026] The slender tube is subjected to multiple external force loadings; the radial parameters corresponding to the preset temperature are obtained and corrected to obtain the corrected high-temperature radial parameters.

[0027] Furthermore, the axial elastic modulus corresponding to the slender tube at a preset temperature is obtained by a high-precision high-temperature axial measuring device.

[0028] Furthermore, during the process of heating the high temperature furnace to a preset temperature, the external force loading applied to the slender tube is zero.

[0029] Compared with the prior art, the present invention has at least the following technical effects:

[0030] (1) The present application provides a step-by-step test method for measuring the high-temperature Poisson's ratio of a slender tube. By assuming a radial parameter, a first room-temperature radial parameter is obtained by a room-temperature radial measuring device test, and a second room-temperature radial parameter is obtained by a high-temperature radial measuring device test to obtain a correction coefficient. On this basis, radial deformation measurement and axial deformation measurement at high temperature can be performed separately to obtain the Poisson's ratio of the slender tube at high temperature. This method does not require the simultaneous measurement of two variables on the same sample at the same time, and the obtained Poisson's ratio has high accuracy. This solves the problem in the prior art that the position of the high-temperature radial extensometer changes during each installation, resulting in different strain measurement results.

[0031] (2) In the prior art, in the test of measuring the Poisson's ratio of a slender tube at high temperature, it is necessary to simultaneously install a high-temperature furnace, two high-temperature extensometers, and a thermocouple on the slender tube. However, since the temperature change is continuous, it is difficult to achieve a large uniform temperature zone. The temperature from the middle position of the slender tube between the upper and lower clamps to the clamps at both ends gradually decreases, resulting in a very small uniform temperature zone on the slender tube. Therefore, in order to measure the axial deformation and radial deformation at the same temperature, it is necessary to simultaneously install two corresponding extensometers on the same side of the uniform temperature zone of the slender tube with a very small range. However, since the volume of the extensometer is fixed, it is difficult to simultaneously achieve a uniform temperature zone with a high-temperature furnace and two high-temperature radial extensometers. In addition, when installing the high-temperature extensometer, a corresponding mounting frame needs to be set on the testing machine. Combined with the installation position and form of the high-temperature furnace, it is difficult to achieve two high-temperature extensometers in the uniform temperature zone at the same time. However, through the method of the present application, the radial deformation measurement and the axial deformation measurement under high temperature can be carried out separately, so that the two extensometers can be measured separately in the uniform temperature zone, which solves the problem in the prior art that it is difficult to simultaneously install a high-temperature furnace and two high-temperature extensometers during the test process of measuring the Poisson's ratio in a high-temperature test. At the same time, it also solves the problem in the prior art that there is no high-precision high-temperature biaxial extensometer measurement device and the Poisson's ratio cannot be directly calculated through a single test.

[0032] (3) In the method of the present application, the first room temperature radial parameter and the second room temperature radial parameter obtained under two tests are used as reference values, and the second room temperature radial parameter measured by the high temperature radial extensometer is corrected, thereby eliminating the error caused by the inherent defects of the high temperature radial extensometer itself and avoiding the error of the Poisson's ratio obtained in the test. At the same time, effective data support is provided for the analysis of mechanical properties of materials, material selection and component improvement, etc., which plays an important role in ensuring the safe operation of equipment in related fields. The measurement results are highly consistent, the temperature range that can be measured is wide, and the test is highly operable and efficient. In addition, in the prior art, since the change of Poisson's ratio with temperature is very small, under normal circumstances, the corresponding change range of Poisson's ratio for every increase of 100°C is 0.01-0.03. It can be seen that when there is a slight error in the measurement result of Poisson's ratio, the corresponding temperature change will be relatively large. In the present application, after the high temperature radial extensometer measurement is corrected, the measurement error of radial strain is reduced, so that the Poisson's ratio can accurately reflect the influence of temperature on the stress of the slender tube. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments of the present invention or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0034] Figure 1 is a flow chart of the method of the present invention;

[0035] Figure 2 This is a data diagram of the first test of the room temperature radial measurement device test in the present invention;

[0036] Figure 3 This is a second test data diagram of the room temperature radial measurement device test in the present invention;

[0037] Figure 4 This is the first test data diagram of the high temperature radial measurement device test in the present invention;

[0038] Figure 5 This is a second test data diagram of the high temperature radial measurement device test in the present invention;

[0039] Figure 6 This is the first test data diagram of the high temperature test in the present invention;

[0040] Figure 7 This is the high temperature test in the present invention, the second test data diagram;

[0041] Figure 8 This is the first test data diagram of elastic modulus measurement in the present invention;

[0042] Fig. 9 This is a second test data diagram of elastic modulus measurement in the present invention. DETAILED DESCRIPTION

[0043] The following description provides many different embodiments or examples for implementing different features of the present invention. The components and arrangements described in the following specific examples are only used to simplify the present invention and are only used as examples, not to limit the present invention.

[0044] Various aspects of the present invention will be described more fully below with reference to the accompanying drawings. However, the present invention can be embodied in many different forms and should not be construed as limited to any specific structure or function presented throughout the present invention. On the contrary, providing these aspects will make the present invention comprehensive and complete, and the present invention will fully convey the scope of the present invention to those skilled in the art. Based on the teachings herein, those skilled in the art should realize that whether any aspect disclosed herein is implemented alone or in combination with any other aspect of the present invention, the scope of the present invention is intended to cover any aspect disclosed herein. For example, any number of cameras or execution methods proposed herein can be used to implement. In addition, in addition to the multiple aspects of the present invention proposed herein, the scope of the present invention is more intended to cover cameras or methods implemented using other structures, functions, or structures and functions. It should be understood that any aspect disclosed herein can be embodied by one or more elements of the claims.

[0045] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0046] All terms (including technical and scientific terms) used herein have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification, and should not be interpreted in an idealized or overly rigid manner.

[0047] The purpose of the present invention is to provide a step-by-step test method for measuring the high-temperature Poisson's ratio of a slender tube to solve at least one of the above technical problems in the prior art, which mainly includes the following contents:

[0048] like Figure 1 As shown, the present invention provides a step-by-step test method for measuring the high-temperature Poisson's ratio of a slender tube, which is characterized by comprising the following steps:

[0049] Step S10: setting and calculating a first room temperature radial parameter through a room temperature radial measurement device test;

[0050] Step S20: obtaining a second room temperature radial parameter by testing a high temperature radial measurement device;

[0051] Step S30: obtaining a correction coefficient according to the first room temperature radial parameter and the second room temperature radial parameter;

[0052] Step S40: performing a high temperature test to obtain radial parameters at a preset temperature, and correcting the radial parameters according to the correction coefficient to obtain corrected high temperature radial parameters;

[0053] Step S50: obtaining the axial elastic modulus at a preset temperature, and calculating the Poisson's ratio according to the axial elastic modulus and the corrected high-temperature radial parameter.

[0054] Poisson's ratio refers to the ratio of the absolute value of the transverse normal strain to the axial normal strain when the material is subjected to unidirectional tension or compression. It is also called the transverse deformation coefficient. It is an elastic constant that reflects the transverse deformation of the material and its value is between 0 and 0.5. If the load is within the elastic range, the transverse strain ε x and axial strain ε y The following relationships exist:

[0055]

[0056] Among them, ν is an elastic constant of the material, called Poisson's ratio.

[0057] Before the test, it is necessary to select the slender tube for the test appropriately to obtain accurate test results. The length of the slender tube can be determined according to the size of the high-temperature furnace. For example, when the volume of the high-temperature furnace is relatively large, the length of the slender tube needs to be selected to be longer. When the volume of the high-temperature furnace is relatively small, the corresponding length of the slender tube is selected to be slightly shorter. There is no specific restriction. Normally, the overall length of the slender tube does not exceed 200mm. The reason is that when the slender tube is too long, the position of the extensometer will move significantly during the tensile test and cause instability. When the height of the high-temperature furnace exceeds 120mm, a corresponding secondary extension fixture will be set to ensure that the overall elongation of the slender tube during the stretching process will not be too large. The secondary extension fixture ensures the stability of the extensometer and the accuracy of the measurement results.

[0058] Assembly of the plug: When the secondary fixture is clamped flat, plugs need to be installed at both ends of the slender tube. The shape of the plug can be round or bullet-shaped, and the diameter of the plug is closely matched with the inner diameter of the slender tube. The reason for this setting is that the round head or bullet head is not only convenient for installation during the test, but also can prevent stress concentration from occurring at the place where the edge of the plug is connected and in contact with the slender tube; setting the diameter of the plug to be closely matched with the inner diameter of the slender tube can prevent the diameter of the plug from being larger than the inner diameter of the slender tube, which makes it difficult to install the plug in the slender tube; when the diameter of the plug is set to be smaller than the slender tube, although the plug can be easily inserted into the inner wall of the slender tube, the plug will slide into the position of the slender tube away from the port, causing the slender tube to be clamped flat.

[0059] Measurement of the size of slender tubes: Due to the small diameter of slender tubes, the wall thickness is also relatively thin. When there is a slight error in the measurement result, the corresponding cross-sectional area of ​​the slender tube will be greatly affected. Therefore, when measuring slender tubes, it is necessary to perform multiple measurements along the circumference of the slender tube, and then perform corresponding calculations to obtain results close to the actual value. It should be noted that before measurement, a large amount of material accumulation will occur at the fracture of the sample tube at the interception position. This phenomenon will have a serious impact on the measurement accuracy. In order to avoid this phenomenon, it is necessary to use fine round files or semi-circular files and other tools to grind the inside and outside of the fracture position of the slender tube before measurement to remove the material accumulation generated during cutting to ensure the measurement accuracy of subsequent tests.

[0060] Selection of different extensometers: When selecting the extensometer in the test process and before use, such as: high-precision room temperature transverse extensometer, high-precision high temperature transverse extensometer, high-precision high temperature longitudinal extensometer, the extensometer needs to be calibrated by an extensometer calibrator to ensure the accuracy of the measurement results in the test.

[0061] Before the test preparation begins, the slender tube is clamped in the upper and lower clamps of the testing machine, and the coaxiality of the upper and lower clamps is ensured to avoid the axial or radial influence of the slender tube during the subsequent test. At the same time, the room temperature radial extensometer and the high-precision high temperature longitudinal extensometer are installed, and the quasi-static force control method is used for loading. The quasi-static force control can accurately control the force to be too small, such as calculating according to the relationship between the cross section and the strength of the slender tube. The force calculated in this way can ensure that each loading is within the elastic range, avoiding the displacement control method causing the slender tube to enter plastic deformation. The wall of the slender tube is relatively thin and the force it can bear is relatively small. Therefore, the loading speed is usually controlled within 50N / S, and the acquisition rate is 10HZ. After loading to the rated force value, the same speed is used to unload back to zero point, and continuous measurements are made for multiple times, of which the first time is usually pre-loaded, so that the clamping state of the slender tube and the installation state of the extensometer can be stabilized, eliminating the imbalance factor of the initial loading of the slender tube, and the first measurement value does not participate in the subsequent calculation.

[0062] First, a room temperature radial measurement device test is carried out, and the data collected during the loading process are processed. First, a parameter E′ is preset and defined as the radial parameter. It should be noted that the radial parameter has no clear physical meaning. The radial parameter E′ can be calculated by the following formula

[0063]

[0064] Where σ is the axial stress of the slender tube, ε x Strain applied to a slender tube

[0065] Then, at room temperature, according to the measurement results obtained by multiple external force loading on the slender tube, the following formula is used to calculate:

[0066]

[0067] Among them, σ1 is the axial stress of the slender tube when it is first loaded, ε x1 is the radial strain of the slender tube when first loaded, E′ rt1 is the first room temperature radial parameter obtained by the first loading of the room temperature radial extensometer, σ2 is the axial stress of the slender tube in the second loading, ε x2 is the radial strain of the slender tube after the second loading, E′ rt2 It is the first room temperature radial parameter obtained by the second loading of the room temperature radial extensometer. The meanings of other letters are similar. i represents the serial number of the loading test, and n represents the number of loading tests.

[0068] again

[0069]

[0070] but

[0071]

[0072] Where E′ rt It represents the first room temperature radial parameter. It can be seen from the above calculation method that the first room temperature radial parameter is calculated based on the average value of the first room temperature radial parameter obtained by multiple loadings of the room temperature radial extensometer at room temperature. In addition, the first room temperature radial parameter can also be calculated based on the weighted value of the first room temperature radial parameter obtained by multiple loadings of the room temperature radial extensometer at room temperature. Here, the method for calculating the first room temperature radial parameter based on multiple loadings of the room temperature radial extensometer at room temperature is not limited here. The first room temperature radial parameter E′ obtained by the method of the present application rt It is closer to the actual measurement results, the results are more accurate, and it has a certain impact on the accuracy of subsequent test results.

[0073] Through the above-mentioned room temperature radial measurement device test, the first room temperature radial parameter is calculated and obtained first. During the test, when the slender tube is loaded with external force by quasi-static force control, it is necessary to ensure that each loading is carried out at room temperature, that is, try to ensure that each time the slender tube is loaded with external force, it is carried out at the same temperature, so that the difference between the first room temperature radial parameter results calculated each time is not large, and the first room temperature radial parameter result finally obtained is guaranteed to be closer to the actual value. The reason is that the diameter of the slender tube is small, resulting in a thin wall thickness. When there is a slight error in the measurement result, it will cause a great impact on the results of other parameters.

[0074] Under the same room temperature conditions as the room temperature radial measurement test, prepare to start the high-temperature radial measuring device test. First, make some adjustments to the device to avoid the room temperature radial extensometer from affecting the measurement results of the subsequent high-temperature radial measuring device test. First, remove the room temperature radial extensometer from the slender tube, and then install the high-temperature furnace on the slender tube. During installation, ensure that the uniform temperature zone of the high-temperature furnace is located in the middle of the slender tube. Install the high-temperature radial extensometer on the slender tube. During the installation process, pay attention to ensure that the fixing rod and the measuring rod of the measuring device are kept on the same horizontal plane. Install a high-precision thermocouple at the position where the high-temperature radial extensometer is installed. In this way, the temperature of the high-temperature furnace can be controlled in real time according to the measurement results of the high-temperature radial extensometer.

[0075] After the adjustment of the device in the high-temperature radial measuring device test is completed, the quasi-static force control method is used to continuously load the slender tube with external force for multiple times. The loading method is the same as the tensile test in the room temperature radial measuring device test. The second room temperature radial parameter is calculated based on the multiple measurement values. The method for calculating the second room temperature radial parameter in this application is as follows:

[0076]

[0077] Among them, σ1 is the axial stress of the slender tube when it is first loaded, ε x1 is the radial strain of the slender tube when first loaded, E′ ht1 is the second radial parameter at room temperature obtained by the first loading of the high temperature radial extensometer, σ2 is the axial stress of the slender tube in the second loading, and ε x2 is the radial strain of the slender tube when first loaded, E′ ht2 It is the second room temperature radial parameter obtained by the second loading of the high temperature radial extensometer. The meanings of other letters are similar. i represents the serial number of the loading test, and n represents the number of loading tests.

[0078] again

[0079]

[0080] but

[0081]

[0082] Where E' ht It represents the second room temperature radial parameter. It can be seen from the above calculation method that the second room temperature radial parameter is calculated based on the average value of the second room temperature radial parameter obtained by multiple loadings of the high-temperature radial extensometer at room temperature. In addition, the second room temperature radial parameter can also be calculated based on the weighted value of the second room temperature radial parameter obtained by multiple loadings of the high-temperature radial extensometer at room temperature. Here, the method for calculating the second room temperature radial parameter based on multiple loadings of the room temperature radial extensometer at room temperature is not limited here. The second room temperature radial parameter E' obtained by the method of the present application ht It is closer to the actual measurement results, the results are more accurate, and it has a certain impact on the accuracy of subsequent test results.

[0083] Through the above-mentioned high-temperature radial measurement device test, the second room temperature radial parameter is first calculated and obtained. During the test, when the slender tube is loaded with external force by quasi-static force control, it is necessary to ensure that each loading is carried out at room temperature, that is, try to ensure that each time the slender tube is loaded with external force, it is carried out at the same temperature, so that the difference between the second room temperature radial parameter results calculated each time is not large, and the final second room temperature radial parameter result obtained is closer to the actual value. The reason is that the diameter of the slender tube is small, resulting in a thin wall thickness. When there is a slight error in the measurement result, it will cause a great impact on the results of other parameters.

[0084] Optionally, the room temperature radial measuring device in the present application may be a room temperature radial extensometer, the high temperature axial measuring device may be a high temperature axial extensometer, and the high temperature radial measuring device may be a high temperature radial extensometer.

[0085] It should be noted that the room temperature conditions mentioned above refer to room temperature in the range of 15°-30°. Due to the factors such as the relatively small diameter and thin wall of the slender tube, the structure of the slender tube itself is sensitive to temperature changes. When the temperature exceeds the above range, the measurement results of some parameters of the slender tube will be inaccurate.

[0086] It should be noted that the slender tube used in the above-mentioned high-temperature radial measuring device test is the same as the slender tube in the room temperature radial measuring device test, that is, it can be understood that the slender tube used in the room temperature radial measuring device test is used in the high-temperature radial measuring device test, which has a great impact on the subsequent acquisition of the correction coefficient.

[0087] It can be seen from the method of obtaining the first room temperature radial parameter through the above-mentioned room temperature radial measurement device test and obtaining the second room temperature radial parameter through the high temperature radial measurement device test that the calculation of the first room temperature radial parameter and the second room temperature radial parameter in the present application are both obtained by calculating the slope. In this way, the randomness and instability brought about by simply using the ratio between point values ​​can be eliminated, which causes errors.

[0088] After calculating and obtaining the first room temperature radial parameter and the second room temperature radial parameter, a correction coefficient can be further obtained based on the two parameters obtained. In this application, it is taken into account that the technology of room temperature radial extensometer is relatively mature, and its measured accuracy is relatively high and the reuse rate is also relatively high, but the technology of high temperature radial extensometer is relatively not so mature. Therefore, in order to make the measurement results of high temperature radial extensometer accurate, at the same temperature, a room temperature radial extensometer and a high temperature radial extensometer are used to measure the axial stress and radial strain of the same slender tube after external force loading, and then the measurement results of the room temperature radial extensometer are used as reference values, and then the measurement results of the high temperature radial extensometer are corrected. The principle is that at the same temperature, for the same slender tube, the first room temperature radial parameter and the second room temperature radial parameter measured multiple times should be the same. Here, there will be the following relationship between the first room temperature radial parameter and the second room temperature radial parameter:

[0089] E′ rt =c E′ ht

[0090] but:

[0091] Where c is the correction coefficient.

[0092] According to the obtained correction coefficient, the high temperature test is further started to calculate the corrected high temperature radial parameters. First, on the basis of the high temperature radial measuring device test, the installation position and state of the high temperature radial extensometer installed during the high temperature radial measuring device test remain unchanged, and the high temperature furnace is started to heat it. During the heating process, the test machine maintains zero load control to eliminate the creep effect of the slender tube caused by the force during the heating process. After heating to the preset temperature, the slender tube is not immediately loaded with external force, but the high temperature furnace is kept warm for 15min-20min. When the external force is loaded by quasi-static force control, the loading speed is the same as that in the room temperature radial measuring device test and the high temperature radial measuring device test. This can avoid the different loading speeds and the corresponding parameter measurement results, which will lead to a large error in the final calculated Poisson's ratio. When the external force is loaded to the maximum load, it needs to be reduced. It can be reduced in real time according to the heating temperature and the yield strength of the slender tube to avoid excessive loading force, which will cause the slender tube to be loaded to plastic deformation. The radial parameters at the preset temperature and the corrected high temperature radial parameters are obtained by this method.

[0093] Get the radial parameter E' at a preset temperature:

[0094]

[0095] Then, the corrected high temperature radial parameter E' X :

[0096] E′ X =CE′

[0097] It should be noted that the preset temperature of the present application can be set to different temperatures according to different test requirements.

[0098] On the basis of the obtained corrected high-temperature radial parameters, the elastic modulus E of the slender tube in the high-temperature test is measured simultaneously to obtain the axial elastic modulus E of the slender tube at the same preset temperature.

[0099] According to the axial elastic modulus and the modified high temperature radial parameter obtained above, the method for calculating the Poisson's ratio is as follows:

[0100]

[0101]

[0102] According to the Poisson's ratio formula, we have:

[0103]

[0104] It can be seen from the above formula that when calculating the Poisson's ratio of the slender tube, the present application only needs to measure and obtain the axial elastic modulus E of the slender tube and the corrected high-temperature radial parameter. It should be noted that the elastic modulus E and the corrected high-temperature radial parameter E' in the present application are X The two variables can be measured separately, that is, there is no need to measure them simultaneously, which solves the technical problem in the prior art that there is no high-precision high-temperature biaxial extensometer that can be used to simultaneously measure the longitudinal deformation and radial deformation at high temperatures. The present application also solves the problem of inaccurate measurement results of high-temperature radial extensometers, and overcomes the problem that the results must be obtained by loading once in the Poisson's ratio measurement test of the prior art.

[0105] The present application provides a step-by-step test method for measuring the high-temperature Poisson's ratio of a slender tube. By assuming a radial parameter, a first room-temperature radial parameter is obtained through a room-temperature radial measuring device test, and a second room-temperature radial parameter is obtained through a high-temperature radial measuring device test to obtain a correction coefficient. On this basis, radial deformation measurement and axial deformation measurement at high temperature can be performed separately to obtain the Poisson's ratio of the slender tube at high temperature. This method does not require simultaneous measurement of two variables on the same sample at the same time, and the obtained Poisson's ratio has high accuracy. This solves the problem in the prior art that the position of the high-temperature radial extensometer changes during each installation, resulting in different results of measured strain.

[0106] Among them, in order to better understand that this method does not require the same sample, an example is given: for example, there are two slender tube samples A and B. It should be noted that the two slender tube samples A and B need to select slender tubes with good uniformity and small dispersion. First, the slender tube A is used to obtain the correction coefficient, and then the slender tube A is used for high temperature test. Only the high temperature radial extensometer is installed, and then a series of increasing temperature tests are carried out to obtain the corrected high temperature radial parameter E' at different preset temperatures. X Then, a high-temperature axial extensometer is installed only on the slender tube B, and then a series of high-temperature tests are carried out at the same temperature point as above to obtain the high-temperature elastic modulus E at the corresponding temperature, and then the corrected high-temperature radial parameter E′ is calculated based on the corresponding temperature. X The Poisson's ratio at the corresponding temperature can be obtained by measuring the elastic modulus E at high temperature, which saves the time of replacing the extensometer when measuring a temperature point. It also reduces the time of reheating to the preset temperature when the temperature drops during the process of opening the high-temperature furnace to replace the extensometer, greatly improving the test and calculation efficiency of the high-temperature Poisson's ratio.

[0107] In the prior art, in the test of measuring the Poisson's ratio of a slender tube under high temperature, it is necessary to simultaneously install a high-temperature furnace, two high-temperature extensometers, and a thermocouple on the slender tube. However, since the temperature change is continuous, it is difficult to achieve a large uniform temperature zone. The temperature from the middle position of the slender tube between the upper and lower clamps to the clamps at both ends gradually decreases, resulting in a very small uniform temperature zone on the slender tube. Therefore, in order to measure the axial deformation and radial deformation at the same temperature, it is necessary to simultaneously install two corresponding extensometers on the same side of the uniform temperature zone of the slender tube with a very small range. However, since the volume of the extensometer is fixed, it is difficult to achieve a uniform temperature zone with a high-temperature furnace and two high-temperature extensometers at the same time. In addition, when installing the high-temperature extensometer, a corresponding mounting frame needs to be set on the testing machine. Combined with the installation position and form of the high-temperature furnace, it is difficult to achieve two high-temperature extensometers in the uniform temperature zone at the same time. However, through the method of the present application, the radial deformation measurement and the axial deformation measurement at high temperature can be carried out separately, so that the two extensometers can be measured separately in the uniform temperature zone, which solves the problem in the prior art that it is difficult to simultaneously install a high-temperature furnace and two high-temperature radial extensometers during the test process of measuring the Poisson's ratio in a high-temperature test. At the same time, it also solves the problem in the prior art that there is no high-precision high-temperature biaxial extensometer measurement device and the Poisson's ratio cannot be directly calculated through a single test.

[0108] In the method of the present application, the first room temperature radial parameter and the second room temperature radial parameter obtained under two tests are used, and the first room temperature radial parameter measured by the room temperature radial extensometer is used as a reference value to correct the second room temperature radial parameter measured by the high temperature radial extensometer, thereby eliminating the error caused by the inherent defects of the high temperature radial extensometer itself, avoiding the error of the Poisson's ratio obtained by the test, and providing effective data support for the analysis of the mechanical properties of the material, material selection and component improvement, etc., which plays an important role in ensuring the safe operation of equipment in related fields, and the measurement results are highly consistent, the temperature range that can be measured is wide, and the test is highly operable and efficient; in addition, in the prior art, since the change of Poisson's ratio with temperature is very small, usually for every increase of 100°C, the corresponding change range of Poisson's ratio is 0.01-0.03. It can be seen that when there is a little error in the measurement result of Poisson's ratio, the corresponding temperature change will be relatively large. After the high temperature radial extensometer measurement is corrected in the present application, the measurement error of radial strain is reduced, so that the Poisson's ratio can accurately reflect the influence of temperature on the stress of the slender tube.

[0109] Furthermore, step S10 further includes:

[0110] A room temperature radial measuring device and a high-precision high temperature axial measuring device are installed on the slender tube, and an external force is applied to the slender tube by means of quasi-static force control;

[0111] Set radial parameters;

[0112] The first radial parameter at room temperature is obtained by continuously applying external force to the slender tube for multiple times.

[0113] In the above scheme, external force is applied to the slender tube by quasi-static force control. The quasi-static force control can accurately control the force, such as calculating according to the relationship between the cross-section and strength of the slender tube. The force calculated in this way can ensure that each loading is within the elastic range, thereby avoiding the displacement control method causing the slender tube to enter plastic deformation.

[0114] In this application, a radial parameter E′ is pre-set to carry out this test to obtain the Poisson's ratio, so that the high-temperature Poisson's ratio test of the slender tube can be divided into two independent tests, successfully solving the current situation that it is difficult to efficiently and accurately measure the Poisson's ratio of the slender tube at high temperature.

[0115] Optionally, the room temperature radial measuring device in the present application may be a room temperature radial extensometer, the high temperature axial measuring device may be a high temperature axial extensometer, and the high temperature radial measuring device may be a high temperature radial extensometer.

[0116] Further, step S20 also includes:

[0117] The room temperature radial measuring device on the slender tube is removed, and a high temperature furnace is installed, and a high temperature radial measuring device and a high-precision thermocouple are installed;

[0118] The slender tube is subjected to continuous external force loading for multiple times, and the second radial parameter at room temperature is calculated.

[0119] In the above scheme, after the room temperature radial measurement device is installed, the room temperature radial extensometer of the slender tube is removed to avoid the installed room temperature radial extensometer from affecting the subsequent measurement results of the slender tube, making the measurement results inaccurate. At the same time, during the installation process, the high-temperature radial extensometer and the high-precision thermocouple are installed at the same position, which improves the measurement accuracy of the high-precision thermocouple and facilitates real-time grasp and control of the temperature of the high-temperature furnace.

[0120] During the test, the slender tube needs to be continuously loaded with external force for multiple times, so as to ensure as much as possible that the measurement results in one test are measured at similar time and the same temperature, and the measured test results are highly accurate.

[0121] Further, the room temperature radial measurement device test and the high temperature radial measurement device test are performed at the same temperature.

[0122] In the above scheme, during the test process, the two tests need to be carried out at the same temperature, so that the difference between the second room temperature radial parameter results calculated each time is not large, ensuring that the final second room temperature radial parameter results are closer to the actual value. The reason is that the diameter of the slender tube is small, resulting in a thinner wall thickness. When there is a slight error in the measurement result, it will cause a great impact on the results of other parameters.

[0123] At the same time, conducting the two tests at the same temperature is also for the purpose of accurately correcting the measurement results of the high-temperature radial extensometer later. The reason is that at the same temperature, for the same slender tube, the first room temperature radial parameter and the second room temperature radial parameter measured multiple times should be the same.

[0124] Furthermore, step S40 further includes:

[0125] Heat the high temperature furnace to a preset temperature;

[0126] The slender tube is subjected to multiple external force loadings; the radial parameters corresponding to the preset temperature are obtained and corrected to obtain the corrected high-temperature radial parameters.

[0127] In the above scheme, in the high temperature test, since the measurement accuracy of the high temperature radial extensometer is not very high, the radial parameters obtained by the high temperature radial extensometer need to be corrected so that the results are closer to the actual accurate values.

[0128] Furthermore, the axial elastic modulus corresponding to the slender tube at a preset temperature is obtained by a high-precision high-temperature axial measuring device.

[0129] In the above scheme, when measuring the axial elastic modulus, the same slender tube as in the first two tests is used, preferably, a portion cut from the same slender tube, to avoid the influence of different types of slender tubes on the accuracy of the test results.

[0130] Furthermore, during the process of heating the high temperature furnace to a preset temperature, the external force loading applied to the slender tube is zero.

[0131] In the above scheme, the testing machine maintains zero load control during the heating process in order to eliminate the creep effect of the slender tube due to the force during the heating process and avoid affecting the measurement results.

[0132] In order to better understand this application, the following is an explanation with reference to specific cases:

[0133] Preparation before the test:

[0134] The parameters of the selected slender tube are as follows, in mm:

[0135] length Outer diameter 1 Outer diameter 2 Outer diameter 3 Mean outer diameter Inner diameter 1 Inner diameter 2 Inner diameter 3 Mean inner diameter Wall thickness 200 9.48 9.46 9.47 9.47 8.38 8.38 8.36 8.37 0.55

[0136] Plug: Stainless steel, length 40mm, ball head at one end

[0137] Device information:

[0138] 15KN hydraulic universal testing machine: test speed: 50N / s, force and displacement accuracy 0.5%

[0139] Room temperature radial extensometer, adjustable gauge length, range ±2mm, accuracy 0.25%

[0140] Room temperature radial extensometer, adjustable gauge length, range ±1mm, accuracy 0.25%

[0141] High temperature axial extensometer, gauge length 25mm, range ±10%, accuracy 0.25%

[0142] Step S10: Test of the room temperature radial measurement device, and the process of obtaining the first room temperature radial parameter:

[0143] At room temperature test temperature of 20℃, for the convenience of explanation, only two sets of test data under external force loading are used, and the radial parameters obtained are E'rt1=277.59GPa and E'rt2=276.29GPa, then the first radial room temperature parameter E'rt=276.9GPa, where the radial strain and axial stress results of the two measured test data are as follows Figure 2 and Figure 3 shown.

[0144] Step S20: High temperature radial measurement device test, process of obtaining the second room temperature radial parameter:

[0145] At room temperature test temperature of 20°C, the radial parameters obtained are E′ht1=272.15GPa and E′ht2=271.99GPa, then the second radial room temperature parameter is E′ht=272.1GPa, where the radial strain and axial stress results of the two measured test data are as follows: Figure 4 and Figure 5 shown.

[0146] Step S30: Obtaining a correction coefficient c=1.018 according to the first room temperature radial parameter and the second room temperature radial parameter.

[0147] Step S40: Perform a high temperature test to obtain radial parameters at a preset temperature, and correct them according to the correction coefficient to obtain corrected high temperature radial parameters. The specific values ​​are as follows:

[0148] The high temperature test temperature is 500℃, and the radial parameters obtained are E′1=141.99GPa and E′2=141.17GPa. Then the high temperature radial parameter E′ is corrected. x=144.1GPa, where the radial strain and axial stress results of the two measured test data are as follows Figure 6 and Figure 7 shown.

[0149] Step S50: Obtain the axial elastic modulus at a preset temperature, and calculate the Poisson's ratio based on the axial elastic modulus and the corrected high-temperature radial parameter. The specific values ​​are as follows:

[0150] Elastic modulus E1 = 59.14 GPa, E2 = 59.49 GPa, then the axial elastic modulus E = 59.3 GPa, Poisson's ratio v = 0.412, where the results of the axial strain and axial stress of the test data measured twice are as follows Figure 8 and Fig. 9 shown.

[0151] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

[0152] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A step-by-step test method for measuring the high-temperature Poisson's ratio of a slender tube, characterized in that: The steps include: Step S10: setting and calculating a first room temperature radial parameter through a room temperature radial measurement device test; Step S20: obtaining a second room temperature radial parameter by testing a high temperature radial measurement device; Step S30: obtaining a correction coefficient according to the first room temperature radial parameter and the second room temperature radial parameter; Step S40: performing a high temperature test to obtain radial parameters at a preset temperature, and correcting the radial parameters according to the correction coefficient to obtain corrected high temperature radial parameters; Step S50: obtaining the axial elastic modulus at a preset temperature, and calculating the Poisson's ratio according to the axial elastic modulus and the corrected high-temperature radial parameter.

2. The test method for measuring the high-temperature Poisson's ratio of a slender tube in a step-by-step manner as claimed in claim 1, characterized in that: Step S10 also includes: A room temperature radial measuring device and a high-precision high temperature axial measuring device are installed on the slender tube, and an external force is applied to the slender tube by means of quasi-static force control; Set radial parameters; The first radial parameter at room temperature is obtained by continuously applying external force to the slender tube for multiple times.

3. The test method for measuring the high-temperature Poisson's ratio of a slender tube in a step-by-step manner as claimed in claim 1, characterized in that: Step S20 also includes: The room temperature radial measuring device on the slender tube is removed, and a high temperature furnace is installed, and a high temperature radial measuring device and a high-precision thermocouple are installed; The slender tube is subjected to continuous external force loading for multiple times, and the second radial parameter at room temperature is calculated.

4. The test method for measuring the high-temperature Poisson's ratio of a slender tube in a step-by-step manner as claimed in claim 1, characterized in that: The room temperature radial measuring device test and the high temperature radial measuring device test are carried out at the same temperature.

5. The test method for measuring the high-temperature Poisson's ratio of a slender tube in a step-by-step manner as claimed in claim 3, characterized in that: Step S40 also includes: Heat the high temperature furnace to a preset temperature; The slender tube is subjected to multiple external force loadings; the radial parameters corresponding to the preset temperature are obtained and corrected to obtain the corrected high-temperature radial parameters.

6. The test method for measuring the high-temperature Poisson's ratio of a slender tube in a step-by-step manner as claimed in claim 5, characterized in that: The axial elastic modulus corresponding to the slender tube at a preset temperature is obtained by a high-precision high-temperature axial measuring device.

7. The test method for measuring the high-temperature Poisson's ratio of a slender tube in a step-by-step manner as claimed in claim 5, characterized in that: During the process of heating the high temperature furnace to a preset temperature, the external force loading applied to the slender tube is zero.

Images