A system and method for impact indentation testing under high temperature conditions.

Abstract

This invention discloses a system and method for impact indentation testing under high-temperature conditions, belonging to the field of testing and metrology. The invention uses a high-temperature resistant piezoelectric cantilever beam as an actuator, extending the high-temperature testing section (without the piezoelectric element) into a three-way high-temperature tube furnace to repeatedly perform impact indentation tests under high-temperature conditions. By combining the dynamic model of the indenter, the force signal measured by the force sensor is corrected to obtain the actual indentation load experienced by the sample during the impact indentation process. Before the test, the indenter is withdrawn a certain distance from the sample surface, allowing it to impact and indent the sample surface at maximum impact velocity. A matching three-way high-temperature tube furnace is used, with the vertical port providing a pathway for an optical displacement gauge suitable for high-temperature environments, thereby measuring the displacement generated at the free end of the high-temperature resistant piezoelectric cantilever beam during the impact indentation process. This invention is applied to impact indentation testing of engineering devices under high-temperature conditions, characterizing their dynamic mechanical properties.

Description

Technical Field

[0001] This invention belongs to the field of testing and metrology, and specifically relates to a system and method for conducting impact indentation tests in a high-temperature environment. Background Technology

[0002] With the continuous development of science and technology, the service requirements for engineering devices in fields such as national defense, military industry, and manufacturing are constantly increasing. Therefore, a series of methods are used to optimize the surface performance of these devices. For example, high-temperature and corrosion-resistant protective thermal barrier coatings are applied to the surface of turbine blades to improve their efficiency, lifespan, and stability under high-temperature conditions; physical vapor deposition technology is used on the surface of processing equipment to optimize its surface properties and prevent premature fatigue damage. These devices operate in harsh environments, often subjected to impact loads at high temperatures, leading to severe damage or even destruction of the device's surface and even internal components, rendering it unusable. Therefore, conducting impact load tests on the device surface or protective coating under high-temperature conditions is of great significance for improving the mechanical properties of the protective coating and enhancing the overall operating efficiency of the device.

[0003] Engineering devices are typically complex to fabricate and expensive. Traditional testing methods for studying the mechanical properties of materials under impact conditions involve using an air gun or weight to accelerate a conical or spherical indenter, causing it to impact and indent the sample surface. The mechanical properties of the material under impact load are then characterized by the indenter's velocity and the residual indentation on the sample surface. Although these tests have relatively mature testing standards, the testing systems are very complex and require extensive preparation before testing, resulting in low efficiency and unsuitability for testing expensive and rare engineering device materials.

[0004] An existing feasible and efficient alternative is instrumented indentation technology. This technology features minimal or even non-destructive testing, eliminates the need for large-scale sample preparation, and offers a simple and rapid testing process. Furthermore, a single test can yield a large amount of data, which can be analyzed to determine the material's mechanical properties. However, current instrumented indentation technologies often employ quasi-static loading methods, making impact indentation testing impossible. They also have stringent environmental requirements, making high-temperature testing difficult. Therefore, it is essential to develop a system and method capable of performing impact indentation tests at high temperatures, enabling efficient testing of sample materials under these conditions. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention proposes a system and method for conducting impact indentation tests under high-temperature conditions.

[0006] One object of the present invention is to provide a system for performing impact indentation testing in a high-temperature environment.

[0007] The system for impact indentation testing under high-temperature conditions according to the present invention includes: a high-temperature resistant piezoelectric cantilever beam, a three-dimensional displacement stage, a force sensor, an indenter, a three-way high-temperature tube furnace, an optical displacement gauge, and control instruments; wherein... The high-temperature resistant piezoelectric cantilever beam comprises: a high-temperature resistant material cantilever beam and a piezoelectric element; the high-temperature resistant material cantilever beam is made of a high-temperature resistant material; the piezoelectric element is disposed at the fixed end of the high-temperature resistant material cantilever beam; the portion of the high-temperature resistant material cantilever beam with the piezoelectric element constitutes the actuation part, and the portion of the high-temperature resistant material cantilever beam without the piezoelectric element constitutes the high-temperature testing part; under high-temperature conditions, the modulus of the high-temperature resistant material cantilever beam is either linearly gradient distributed along the length direction or remains constant; The fixed end of the high-temperature resistant piezoelectric cantilever beam is mounted on a three-dimensional displacement stage; A pressure head is installed at the free end of a cantilever beam made of high-temperature resistant material, and a force sensor is fixed between the free end of the cantilever beam made of high-temperature resistant material and the pressure head; The three-way high-temperature tube furnace includes a split tube furnace and a vertical through-hole; a vertical through-hole is opened on the furnace body of the split tube furnace, and an opening is cut on the side wall of the furnace tube corresponding to the vertical through-hole, so that the vertical through-hole is connected to the furnace tube through the opening; a high-temperature resistant platform is placed inside the furnace tube at the position corresponding to the vertical through-hole for mounting the sample; an optical displacement meter is installed at the top of the vertical through-hole; the distance from the tube opening of the split tube furnace to the high-temperature resistant platform is less than the length of the high-temperature test section; The piezoelectric element, three-dimensional displacement stage, optical displacement meter, and three-way high-temperature tube furnace are respectively connected to the control instrument; The high-temperature testing section of the high-temperature resistant piezoelectric cantilever beam extends into a three-way high-temperature tube furnace. A three-dimensional displacement stage is used to adjust the three-dimensional position of the high-temperature piezoelectric cantilever beam, controlling the indenter to be directly above the sample. The distance between the indenter and the sample is then determined by the damping characteristics of the high-temperature resistant material cantilever beam during free vibration. Δh = h 0 -h 1, h 1 represents the stable position of the free end of the high-temperature resistant piezoelectric cantilever beam after excitation. h 0 The initial position of the free end of the high-temperature resistant material cantilever beam is determined by the control instrument; a three-way high-temperature tube furnace is used to heat the beam to a high temperature; a DC pulse is applied as the excitation voltage to the piezoelectric element to excite the high-temperature resistant piezoelectric cantilever beam. The rapid expansion and contraction of the piezoelectric element causes the high-temperature resistant material cantilever beam to undergo rapid bending deformation, allowing the indenter at the free end to rapidly impact and press into the sample. The indenter impacts and presses into the sample surface at maximum impact velocity, achieving the maximum conversion between the indenter's kinetic energy and the plastic work of the indentation, resulting in the best impact indentation effect; an optical displacement meter measures the displacement of the indenter located at the free end of the high-temperature resistant material cantilever beam. hThe force sensor acquires the force signal of the pressure head. F Through dynamic analysis, the actual indentation load on the specimen was obtained. P = F - , The inertial force of the pressure head, m For the mass of the pressure head, The acceleration of the indenter is expressed as the displacement of the indenter. h The computer calculates the indentation load-depth curve (i.e., force-displacement curve) after the indenter impacts the specimen under high temperature conditions by performing a second derivative with respect to time, based on the actual indentation load and the displacement of the indenter.

[0008] The high-temperature resistant material cantilever beam is made of high-temperature resistant ceramic. The length of the high-temperature resistant material cantilever beam is related to its output displacement and the indentation load on the sample. If the length is too long, it cannot withstand the pressure; if the indentation load is too small, it cannot be pressed into the sample; if it is too short, it cannot reach the high-temperature zone; if it is too short, it is difficult to operate in practice and cannot isolate the high temperature. The length of the high-temperature resistant material cantilever beam is 80~100mm. The piezoelectric sheet is polarized along the thickness direction, and the direction of the electric field formed by the excitation voltage is the same as the polarization direction. The length of the piezoelectric sheet is less than 1 / 2 of the length of the high-temperature resistant material cantilever beam. If the length of the piezoelectric sheet is too long, the high-temperature test section of the high-temperature resistant piezoelectric cantilever beam will be too short, making it impossible to extend into the three-way high-temperature tube furnace, thus failing to construct a high-temperature environment for testing. If the length of the piezoelectric sheet is too short, the actuation capability of the high-temperature resistant piezoelectric cantilever beam will be poor, failing to provide sufficient output displacement, and the indenter will not be able to fully press into the sample surface. In this invention, the length of the piezoelectric sheet is set to 40~50mm. The fixed end of the high-temperature resistant piezoelectric cantilever beam is fixed to a base, which is mounted on a three-dimensional displacement stage. The three-dimensional displacement stage is precisely controlled by a computer to position the free end indenter of the high-temperature resistant piezoelectric cantilever beam on the sample. A piezoelectric element is positioned on the lower surface of the fixed end of the high-temperature resistant material cantilever beam. The contraction mode of the piezoelectric element causes the high-temperature resistant material cantilever beam to bend downwards; alternatively, the piezoelectric element can be positioned on the upper surface of the fixed end of the high-temperature resistant material cantilever beam, and the elongation mode of the piezoelectric element causes the high-temperature resistant material cantilever beam to bend downwards. The actuation effect caused by contraction is more stable than that caused by elongation; therefore, it is preferable to position the piezoelectric element on the lower surface of the fixed end of the high-temperature resistant material cantilever beam.

[0009] The optical displacement meter uses a laser interferometer or a confocal displacement meter. The three-dimensional displacement stage uses a piezoelectric displacement stage.

[0010] The split-tube furnace includes: a furnace body, a cavity, furnace tubes, a resistance wire, and a controller; wherein, a cavity is opened in the furnace body, the resistance wire is wound around the middle area of ​​the furnace tube, and the furnace tube with the resistance wire wound is inserted into the cavity; the resistance wire is connected to the controller, and the controller is connected to a computer; when the resistance wire is energized, it heats the split-tube furnace.

[0011] The control instrument includes: a computer, a charge amplifier, a signal generator, a high-voltage amplifier, and a data acquisition card. The force sensor is connected to the charge amplifier; the charge amplifier, optical displacement meter, and high-voltage amplifier are each connected to the data acquisition card; the signal generator is connected to the high-voltage amplifier, which in turn is connected to the piezoelectric element; the three-dimensional displacement stage, signal generator, and data acquisition card are all connected to the computer. The computer controls the signal generator to generate a signal, which is amplified by the high-voltage amplifier to produce a DC pulse to excite the piezoelectric element. The charge amplifier converts the charge signal collected by the force sensor into a measurable force signal. The optical displacement meter collects the displacement signal. The data acquisition card records the DC pulse from the high-voltage amplifier, the force signal collected by the charge amplifier, and the displacement signal collected by the optical displacement meter, and transmits this data to the computer. The computer then obtains the displacement of the free end of the high-temperature resistant piezoelectric cantilever beam, i.e., the displacement of the indenter. h The force signal of the pressure head is obtained from the force sensor. F Through dynamic analysis, the actual indentation load on the specimen was obtained. P = F - , The inertial force of the pressure head, m For the mass of the pressure head, The acceleration of the indenter is expressed as the displacement of the indenter. h The computer calculates the indentation load-depth curve (i.e., force-displacement curve) after the indenter impacts the specimen under high temperature conditions by performing a second derivative with respect to time, based on the actual indentation load and the displacement of the indenter.

[0012] By analyzing the curves, mechanical property parameters of the sample material, such as hardness and elastic modulus, can be extracted. Since the sample is subjected to impact indentation testing at a high temperature, the correlation between the material's mechanical properties and temperature and strain rate can be demonstrated by adjusting the temperature and impact velocity. For example, by conducting tests at different temperatures and / or different impact velocities, the mechanical property parameters of the material can be obtained from the curve analysis. The performance changes of the material under temperature and strain rate conditions can be analyzed, that is, the dynamic mechanical properties exhibited by the material under high temperature conditions. This allows for the design of the surface of devices operating under high temperature and impact conditions.

[0013] Another objective of this invention is to provide a method for conducting impact indentation tests under high-temperature conditions.

[0014] The method for conducting impact indentation testing under high-temperature conditions according to the present invention includes the following steps: 1) Place the sample on a high-temperature resistant platform inside a three-way high-temperature tube furnace; 2) The high-temperature test section of the high-temperature piezoelectric cantilever beam extends into the three-way high-temperature tube furnace. The three-dimensional position of the high-temperature piezoelectric cantilever beam is adjusted by a three-dimensional displacement stage to control the pressure head to be directly above the sample. The distance between the pressure head and the sample is controlled to be the distance calculated by the attenuation characteristics of the high-temperature piezoelectric cantilever beam during free vibration. 3) The control instrument controls the heating of the three-way high-temperature tube furnace to a high temperature; 4) A DC pulse is applied as the excitation voltage to the piezoelectric sheet to excite the high-temperature resistant piezoelectric cantilever beam, and the indenter impacts and presses into the sample surface; 5) The displacement of the indenter at the free end of the high-temperature resistant piezoelectric cantilever beam is measured by an optical displacement meter; the force signal of the indenter is collected by a force sensor. 6) The computer obtains the actual indentation load on the specimen through dynamic analysis; 7) The computer obtains the indentation load-depth curve, i.e. the force-displacement curve, generated after the indenter impacts the specimen under high temperature conditions, based on the actual indentation load and the displacement of the indenter.

[0015] In step 2), the distance between the indenter and the sample... Δh = h 0 -h 1, h 1 represents the stable position of the free end of the high-temperature resistant piezoelectric cantilever beam after excitation. h 0 This represents the initial position of the free end of the high-temperature resistant piezoelectric cantilever beam.

[0016] In step 6), the actual indentation load on the specimen P = F - , The inertial force of the pressure head, m For the mass of the pressure head, The acceleration of the indenter is expressed as the displacement of the indenter. h The result is obtained by taking the second derivative with respect to time.

[0017] Advantages of this invention: Compared to existing technologies, the innovations and advantages of this invention are as follows: It uses a high-temperature resistant piezoelectric cantilever beam as the actuator, replacing the stainless steel material of the cantilever beam with high-temperature resistant ceramic. The high-temperature test section without the piezoelectric element is inserted into a high-temperature environment, allowing repeated impact indentation tests under high-temperature conditions without damaging the actuation characteristics of the high-temperature resistant piezoelectric cantilever beam. The elastic modulus of the high-temperature resistant cantilever beam changes little with temperature; therefore, the elastic modulus of the high-temperature resistant cantilever beam inserted into the high-temperature environment can be analyzed under known test temperatures. The temperature distribution along the length of the high-temperature resistant cantilever beam is obtained through a control instrument and is considered to be either a linear gradient distribution along the length direction or constant, which helps in subsequent analysis of the dynamic characteristics of the high-temperature resistant piezoelectric cantilever beam under high-temperature conditions. A force sensor and indenter suitable for high-temperature environments are attached to the free end of the high-temperature resistant piezoelectric cantilever beam using high-temperature resistant ceramic adhesive. The force sensor records the force generated during the impact indentation process, and the force signal measured by the force sensor is corrected by combining it with the dynamic model of the indenter. The actual indentation load experienced by the sample during the impact indentation process is obtained. A DC pulse is used as the excitation voltage to excite the high-temperature piezoelectric cantilever beam. The rapid expansion and contraction deformation of the piezoelectric element drives the rapid bending deformation of the high-temperature piezoelectric cantilever beam, causing the indenter at the free end of the high-temperature piezoelectric cantilever beam to impact and indent the sample surface at a large impact velocity. Considering the attenuation characteristics of the high-temperature piezoelectric cantilever beam during free vibration, the indenter is withdrawn from the sample surface by a certain distance before the test, so that the indenter impacts and indents the sample surface at the maximum impact velocity, achieving the maximum conversion between the kinetic energy of the indenter and the plastic work of the indentation, and achieving the best impact indentation effect. A matching three-way high-temperature tube furnace is used to construct a high-temperature environment for the high-temperature piezoelectric cantilever beam. A high-temperature ceramic platform is placed in the middle of the furnace tube to hold the sample to be tested. The high-temperature test part of the high-temperature piezoelectric cantilever beam extends into the furnace tube to realize the impact indentation test under high-temperature environment. The vertical port provides a passage for an optical displacement gauge suitable for high-temperature environment to measure the displacement generated by the free end of the high-temperature piezoelectric cantilever beam during the impact indentation process. This invention is used to perform impact indentation tests on sample materials under high temperature conditions, which can characterize the dynamic mechanical properties of materials under high temperature conditions. It is of great significance for improving the mechanical properties of engineering devices that are used under high temperature and impact conditions, and improving their working efficiency and service life. Attached Figure Description

[0018] Figure 1 This is an overall schematic diagram of an embodiment of the system for performing impact indentation testing under high-temperature conditions according to the present invention; Figure 2 This is a schematic diagram of a high-temperature resistant piezoelectric cantilever beam, representing an embodiment of the system for impact indentation testing under high-temperature conditions according to the present invention. Figure 3This is a schematic diagram illustrating the measurement principle of a high-temperature resistant piezoelectric cantilever beam, representing an embodiment of the system for impact indentation testing under high-temperature conditions according to the present invention. Figure 4 This is a temperature and modulus distribution diagram of the high-temperature test section of a high-temperature resistant piezoelectric cantilever beam, which is an embodiment of the system for impact indentation testing under high-temperature conditions according to the present invention. Figure 5 This is a schematic diagram illustrating the free vibration attenuation characteristics of a high-temperature piezoelectric cantilever beam, according to an embodiment of the system for impact indentation testing under high-temperature conditions of the present invention. Figure 6 This is a schematic diagram of the impact pressing of a high-temperature piezoelectric cantilever beam, an embodiment of the system for impact pressing tests in a high-temperature environment according to the present invention. Figure 7 This is a schematic diagram of a three-way high-temperature tube furnace, which is an embodiment of the system for performing impact indentation tests in a high-temperature environment according to the present invention. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0020] like Figure 1 As shown, the system for impact indentation testing under high temperature conditions in this embodiment includes: a high-temperature resistant piezoelectric cantilever beam, a three-dimensional displacement stage, a force sensor, an indenter, a three-way high-temperature tube furnace, an optical displacement meter, and control instruments.

[0021] like Figure 2 As shown, the fixed end of the high-temperature resistant piezoelectric cantilever beam is mounted on a three-dimensional displacement stage via a base; the high-temperature resistant piezoelectric cantilever beam includes: a cantilever beam made of high-temperature resistant material and a piezoelectric sheet.

[0022] The high-temperature resistant piezoelectric cantilever beam of this invention replaces the material of the cantilever beam with high-temperature resistant ceramic instead of ordinary stainless steel; for example... Figure 3As shown, a piezoelectric element is attached to the lower surface of the fixed end of a high-temperature resistant material cantilever beam using high-temperature resistant ceramic adhesive. The contraction mode of the piezoelectric element drives the cantilever beam to bend downwards, resulting in a more stable actuation effect. The piezoelectric element is polarized along its thickness direction, and the electric field generated by the excitation voltage is in the same direction as the polarization. According to the piezoelectric effect, the piezoelectric element will contract and deform under the excitation voltage, thereby driving the high-temperature resistant material cantilever beam to bend and deform, resulting in a large output displacement at the free end. Since the piezoelectric element acts as the driving source for the high-temperature resistant piezoelectric cantilever beam, to avoid damage to the actuation characteristics of the piezoelectric element in the high-temperature testing environment, the high-temperature resistant piezoelectric cantilever beam is divided into an actuation part and a high-temperature testing part. The actuation part is the high-temperature resistant material cantilever beam with the piezoelectric element, while the high-temperature testing part is the high-temperature resistant material cantilever beam without the piezoelectric element. The high-temperature testing part is placed in a high-temperature environment, while the actuation part remains in a room-temperature environment, enabling repeated testing in a high-temperature environment without damaging the actuation characteristics of the high-temperature resistant piezoelectric cantilever beam. Using high-temperature resistant ceramics as the cantilever beam material, the modulus of the high-temperature resistant ceramics is not significantly affected by the high-temperature environment. During testing, the high-temperature test section of the high-temperature resistant piezoelectric cantilever beam is immersed in the high-temperature environment. Since a tube furnace is used for heating, the temperature distribution along the length of the high-temperature resistant material cantilever beam is determined, thus obtaining the modulus distribution along the length of the cantilever beam. Because the modulus of the high-temperature resistant ceramic is less affected by temperature, it is considered to have a linear distribution. Figure 4 As shown, this demonstrates that temperature has little impact on the accuracy of subsequent test results. E 1 and E 2 These are the corresponding ambient temperatures for high-temperature resistant ceramics. T 1 and test temperature T 2 The elastic modulus. For some high-temperature resistant ceramics, such as alumina, at the test temperature... T 2 Below melting point T m In half of the cases, the modulus can be considered approximately constant, which means... E 1 ≈ E 2 This means that the modulus remains constant along the length direction. This modulus analysis has certain reference value for subsequent analysis of the dynamic performance of high-temperature resistant piezoelectric cantilever beams under high-temperature testing environments.

[0023] The principle behind the large output displacement of a piezoelectric cantilever beam lies in the following: a piezoelectric sheet, polarized along the thickness direction, is attached to the lower surface of the high-temperature resistant material cantilever beam. A voltage in the same direction as the polarization is applied along the thickness of the piezoelectric sheet. Due to the relatively long length of the piezoelectric sheet, the expansion and contraction along its length is the primary deformation. The piezoelectric sheet, attached to the lower surface of the fixed end of the high-temperature resistant material cantilever beam, causes bending deformation, resulting in a large output displacement at the free end. A high-temperature resistant force sensor and an indenter are attached using high-temperature resistant ceramic adhesive. The force sensor is placed between the indenter and the free end to measure the force generated during the impact indentation process. To enable the indenter to impact and indent the sample surface at a faster speed, this invention proposes using a DC pulse as the excitation voltage to actuate the high-temperature resistant piezoelectric cantilever beam. Under free conditions, i.e., during the deformation process of the high-temperature resistant piezoelectric cantilever beam, the free end indenter does not contact the sample. Considering the free vibration attenuation characteristics of the high-temperature resistant piezoelectric cantilever beam, its free end displacement is as follows: Figure 5 As shown, after the vibration of the free end of the high-temperature piezoelectric cantilever beam decays under DC pulse excitation until a steady state is reached, the free end of the high-temperature piezoelectric cantilever beam is in a stable position; where displacement is the displacement generated by the free end of the high-temperature piezoelectric cantilever beam, and time is the deformation time. h 0 represents the initial position of the free end of the high-temperature piezoelectric cantilever beam; at this point, no DC pulse has been applied. h 1 represents the stable position of the free end of the high-temperature resistant piezoelectric cantilever beam after excitation. Δh The displacement of the free end of the high-temperature piezoelectric cantilever beam before and after being subjected to a DC pulse is given by... Δh = h 0 -h 1, ranging from several to tens of micrometers; t 1 The duration of the DC pulse application. t 2 This refers to the time it takes for the free vibration of the high-temperature piezoelectric cantilever beam to reach a steady state after it has finished decaying. Considering that the free end of the high-temperature piezoelectric cantilever beam has the maximum velocity during its free vibration decay process when it corresponds to the stable position, the position corresponding to the free end of the high-temperature piezoelectric cantilever beam in steady state is chosen here. A The position of the indenter impacting the specimen is chosen because it allows the indenter to reach its maximum velocity before its energy is dissipated by free vibration, maximizing the conversion between the indenter's kinetic energy and the plastic work of the indentation, resulting in the best impact indentation effect. To achieve this, only the stable position of the free end of the high-temperature piezoelectric cantilever beam needs to be determined. h After step 1, withdraw the indenter upwards from the sample surface. Δh That's it. The pressure head is positioned at the corresponding position at the free end of the high-temperature resistant piezoelectric cantilever beam. AAfter the specimen is impacted and pressed into it, the displacement of the free end is as follows: Figure 6 As shown, since the energy after the first impact indentation will continuously decrease during subsequent contact processes, only the result of the first impact indentation is considered here, and the results of subsequent rebound indentation are not taken into account. In this embodiment, the high-temperature resistant material is alumina, the length of the high-temperature resistant material cantilever beam is 100mm, the piezoelectric sheet material is PZT51, the length is 50mm, and it is attached to the lower surface of the fixed end of the high-temperature resistant material cantilever beam with high-temperature resistant ceramic adhesive. The DC pulse is 100V, and the initial position of the free end of the high-temperature resistant piezoelectric cantilever beam is set. h 0 =0, under the action of the excitation voltage, the free end of the high-temperature piezoelectric cantilever beam will produce a downward displacement. At this time, under the action of a 100V DC pulse, the estimated stable position of the free end of the high-temperature piezoelectric cantilever beam is about 30μm, that is, h 1 = -30μm, at this time Δh =30μm, meaning the initial distance between the sample and the indenter should be set to 30μm. Δh =30μm.

[0024] During impact indentation, a force sensor measures the force generated. However, due to the high speed and significant inertial effect of the impact indentation process, the signal obtained from the force sensor needs correction. Performing a dynamic analysis of the indenter here allows for the correction of the force sensor signal, thus obtaining the true indentation load on the specimen. Force analysis of the indenter is then performed. F The force signal is obtained by the force sensor. P This represents the actual indentation load experienced by the specimen. The inertial force of the pressure head, m For the mass of the pressure head, The acceleration of the indenter is expressed as the displacement of the indenter. h The result is obtained by taking the second derivative with respect to time, and then through dynamic analysis, we have... P = F - .

[0025] To provide a high-temperature environment for the high-temperature resistant piezoelectric cantilever beam, the furnace tube is still heated using traditional resistance wire and the temperature is measured via thermocouples. A high-temperature resistant ceramic platform is placed in the middle of the furnace tube to hold the sample. During the high-temperature test, the high-temperature test section of the high-temperature resistant piezoelectric cantilever beam is inserted into the furnace tube, and the position of the indenter is positioned using a three-dimensional displacement stage. The indenter is positioned at the point where it impacts the sample surface and then withdrawn a certain distance from the sample surface for the impact indentation test. After heating the furnace tube with resistance wire, the sample and the high-temperature test section are fully heated. Once preparation is complete, the impact indentation test is performed.

[0026] To measure the displacement generated at the free end of the high-temperature piezoelectric cantilever beam during impact pressing, an upward vertical opening is added in the middle of the horizontal opening. An optical displacement gauge suitable for high-temperature environments is fixed at the top of the vertical opening. An opening is cut on the upper side of the furnace tube at the corresponding position, thus providing a measurement path for the optical displacement gauge. When the impact pressing test is performed in a high-temperature environment, the optical displacement gauge can measure the displacement generated at the free end of the high-temperature piezoelectric cantilever beam through this path.

[0027] like Figure 7 As shown, the three-way high-temperature tube furnace includes a split tube furnace and a vertical port. The split tube furnace includes a furnace body, a cavity, a furnace tube, a resistance wire, and a controller. A cavity is formed within the furnace body, and the resistance wire is wound around the middle area of ​​the furnace tube, which is then inserted into the cavity. The resistance wire is connected to the controller, which is connected to a computer. A vertical port is formed on the furnace body of the split tube furnace, and an opening is cut into the side wall of the furnace tube corresponding to the vertical port, allowing the vertical port to connect to the furnace tube. A high-temperature platform is placed inside the furnace tube at the position corresponding to the vertical port for mounting the sample. An optical displacement meter is installed at the top of the vertical port. The distance from the tube opening of the split tube furnace to the high-temperature platform is less than the length of the high-temperature testing section, which extends into the furnace tube. Typical high-temperature tube furnaces can reach temperatures of 1000-1200℃. However, for the testing method of this invention, the high-temperature testing section not only includes a high-temperature resistant cantilever beam but also a pressure head, force sensor, and high-temperature resistant ceramic adhesive. Therefore, the testing temperature is limited by these components. Among these, the force sensor is more sensitive to temperature than the high-temperature resistant cantilever beam, pressure head, and high-temperature resistant ceramic adhesive; thus, the testing temperature is primarily limited by the force sensor. Currently, the upper temperature limit of relatively advanced force sensors capable of operating in high-temperature environments is 500℃. Therefore, the upper limit of the testing temperature here is limited to 300-400℃. If the upper limit of the force sensor's testing temperature can be increased, the upper limit of the testing temperature of this invention can be further improved.

[0028] The control instruments include: a computer, a charge amplifier, a signal generator, a high-voltage amplifier, and a data acquisition card. The force sensor is connected to the charge amplifier; the charge amplifier, optical displacement meter, and high-voltage amplifier are each connected to the data acquisition card; the signal generator is connected to the high-voltage amplifier, which in turn is connected to the piezoelectric element; the three-dimensional displacement stage, signal generator, and data acquisition card are all connected to the computer. The computer controls the signal generator to generate a signal, which is amplified by the high-voltage amplifier to produce a DC pulse to excite the piezoelectric element. The charge amplifier converts the charge signal collected by the force sensor into a measurable force signal. The optical displacement meter collects the displacement signal. The data acquisition card records the DC pulse from the high-voltage amplifier, the force signal collected by the charge amplifier, and the displacement signal collected by the optical displacement meter, and transmits these data to the computer. Based on the actual indentation load and the displacement of the indenter, the computer obtains the indentation load-depth curve, i.e., the force-displacement curve, generated after the indenter impacts the specimen under high-temperature conditions.

[0029] In this embodiment, the optical displacement meter is a laser interferometer; the three-dimensional displacement stage is a piezoelectric displacement stage.

[0030] The method for conducting impact indentation testing under high-temperature conditions in this embodiment includes the following steps: 1) Place the sample on a high-temperature resistant platform inside a three-way high-temperature tube furnace; 2) The high-temperature testing section of the high-temperature resistant piezoelectric cantilever beam extends into a three-way high-temperature tube furnace. The three-dimensional position of the high-temperature piezoelectric cantilever beam is adjusted using a three-dimensional displacement stage to control the indenter to be directly above the sample, and the distance between the indenter and the sample is controlled to be 20 μm. Δh = h 0 -h 1, h 1 represents the position of the free end of the high-temperature piezoelectric cantilever beam after vibration decay and reaching a steady state under DC pulse excitation. h 0 This refers to the position of the free end of the high-temperature piezoelectric cantilever beam before a DC pulse is applied. 3) The control instrument controls the three-way high-temperature tube furnace to heat to a high temperature of 300~400℃; 4) A DC pulse is applied as the excitation voltage to the piezoelectric sheet to excite the high-temperature resistant piezoelectric cantilever beam, and the indenter impacts and presses into the sample surface; 5) The displacement of the indenter at the free end of the high-temperature resistant piezoelectric cantilever beam is measured by an optical displacement meter; the force signal of the indenter is collected by a force sensor. 6) The computer obtains the actual indentation load on the specimen through dynamic analysis. P = F - ,F The force signal is obtained by the force sensor. P This represents the actual indentation load experienced by the specimen. The inertial force of the pressure head, m For the mass of the pressure head, The acceleration of the indenter is expressed as the displacement of the indenter. h The result is obtained by taking the second derivative with respect to time. 7) The computer obtains the indentation load-depth curve, i.e., the force-displacement curve, generated after the indenter impacts the specimen under high temperature conditions, based on the actual indentation load and the displacement of the indenter. By analyzing the curve, the mechanical property parameters of the specimen material, such as hardness and elastic modulus, are extracted. Since the specimen is subjected to impact indentation testing under high temperature conditions, the correlation between the material's mechanical properties and temperature and strain rate can be shown by adjusting the temperature and impact speed. For example, by conducting tests at different temperatures and / or different impact speeds, the mechanical property parameters of the material can be obtained from the curve analysis. The performance changes of the material under temperature and strain rate conditions can be analyzed, i.e., the dynamic mechanical properties exhibited by the material under high temperature conditions. This allows for the design of the surface of devices operating under high temperature and impact conditions.

[0031] Finally, it should be noted that the purpose of disclosing the embodiments is to help further understand the present invention. However, those skilled in the art will understand that various substitutions and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the present invention should not be limited to the content disclosed in the embodiments, and the scope of protection of the present invention is defined by the claims.

Claims

1. A system for conducting impact indentation tests under high-temperature conditions, characterized in that, The system includes: a high-temperature resistant piezoelectric cantilever beam, a three-dimensional displacement stage, a force sensor, a pressure head, a three-way high-temperature tube furnace, an optical displacement gauge, and control instruments; among which... The high-temperature resistant piezoelectric cantilever beam includes: a high-temperature resistant material cantilever beam and a piezoelectric element; the high-temperature resistant material cantilever beam is made of high-temperature resistant material; the piezoelectric element is set at the fixed end of the high-temperature resistant material cantilever beam to form the actuation part, and the part of the high-temperature resistant material cantilever beam without the piezoelectric element constitutes the high-temperature testing part; The fixed end of the high-temperature resistant piezoelectric cantilever beam is mounted on a three-dimensional displacement stage; A pressure head is installed at the free end of a cantilever beam made of high-temperature resistant material, and a force sensor is fixed between the free end of the cantilever beam made of high-temperature resistant material and the pressure head; The three-way high-temperature tube furnace includes a split tube furnace and a vertical port; a vertical port is opened on the furnace body of the split tube furnace, and the vertical port is connected to the furnace tube through an opening opened on the furnace tube; a high-temperature resistant platform is placed inside the furnace tube at the position corresponding to the vertical port, and the sample is placed on it; an optical displacement meter is set at the top of the vertical port. The piezoelectric element, three-dimensional displacement stage, optical displacement meter, and three-way high-temperature tube furnace are respectively connected to the control instrument; The high-temperature testing section of the high-temperature resistant piezoelectric cantilever beam extends into a three-way high-temperature tube furnace. The distance between the indenter and the sample is controlled by a three-dimensional displacement stage and is calculated based on the attenuation characteristics of the high-temperature resistant piezoelectric cantilever beam during free vibration. The three-way high-temperature tube furnace is heated to a high temperature. A DC pulse is used as the excitation voltage to excite the high-temperature resistant piezoelectric cantilever beam, and the indenter at the free end impacts and presses into the sample. An optical displacement gauge measures the displacement of the indenter, a force sensor collects the force signal of the indenter, and the actual indentation load on the sample is obtained through dynamic analysis.

2. The system according to claim 1, characterized in that, The length of the high-temperature resistant material cantilever beam is 80~100mm.

3. The system according to claim 1 or 2, characterized in that, The length of the piezoelectric element is 40~50mm.

4. The system according to claim 1, characterized in that, The optical displacement meter is either a laser interferometer or a confocal displacement meter.

5. The system according to claim 1, characterized in that, The control instrument includes: a computer, a charge amplifier, a signal generator, a high-voltage amplifier, and a data acquisition card; wherein, the force sensor is connected to the charge amplifier; the charge amplifier, optical displacement meter, and high-voltage amplifier are respectively connected to the data acquisition card; the signal generator is connected to the high-voltage amplifier, and the high-voltage amplifier is connected to the piezoelectric element; the three-dimensional displacement stage, the signal generator, and the data acquisition card are respectively connected to the computer; the computer controls the signal generator to generate a signal, the high-voltage amplifier amplifies the signal generated by the signal generator to generate a DC pulse for exciting the piezoelectric element, the charge amplifier converts the charge signal collected by the force sensor into a force signal, the optical displacement meter collects the displacement signal, and the data acquisition card records the DC pulse, force signal, and displacement signal, and transmits them to the computer.

6. The system according to claim 5, characterized in that, The computer obtains the displacement h of the indenter based on the displacement signal, and through dynamic analysis based on the force signal F, obtains the true indentation load P = F - , Let m be the inertial force of the indenter, and m be the mass of the indenter. The computer calculates the indentation load-depth curve based on the actual indentation load and the displacement of the indenter, using the acceleration of the indenter as the basis. This curve is generated when the indenter impacts the specimen under high temperature conditions.

7. The system according to claim 1, characterized in that, The distance Δh between the indenter and the sample is h0-h1, where h1 is the stable position of the free end of the high-temperature resistant piezoelectric cantilever beam after excitation, and h0 is the initial position of the free end of the high-temperature resistant piezoelectric cantilever beam.

8. A method for conducting impact indentation testing under high-temperature conditions, characterized in that, The method includes the following steps: 1) Place the sample on a high-temperature resistant platform inside a three-way high-temperature tube furnace; 2) The high-temperature test section of the high-temperature resistant piezoelectric cantilever beam extends into the three-way high-temperature tube furnace. The three-dimensional position of the high-temperature resistant piezoelectric cantilever beam is adjusted by a three-dimensional displacement stage. The pressure head is controlled to be directly above the sample, and the distance between the pressure head and the sample is controlled to be the distance calculated by the attenuation characteristics of the high-temperature resistant piezoelectric cantilever beam during free vibration. 3) The control instrument controls the heating of the three-way high-temperature tube furnace to a high temperature; 4) A DC pulse is applied as the excitation voltage to the piezoelectric sheet to excite the high-temperature resistant piezoelectric cantilever beam, and the indenter impacts and presses into the sample surface; 5) The displacement of the indenter at the free end of the high-temperature resistant piezoelectric cantilever beam is measured by an optical displacement meter; the force signal of the indenter is collected by a force sensor. 6) The computer obtains the actual indentation load on the specimen through dynamic analysis; 7) The computer obtains the indentation load-depth curve generated after the indenter impacts the specimen under high temperature conditions, based on the actual indentation load and the displacement of the indenter.

9. The method according to claim 8, characterized in that, In step 2), the distance between the indenter and the sample is Δh = h0 - h1, where h1 is the stable position of the free end of the high-temperature piezoelectric cantilever beam after excitation, and h0 is the initial position of the free end of the high-temperature piezoelectric cantilever beam.

10. The method according to claim 8, characterized in that, In step 6), the actual indentation load on the specimen is P = F - , Let m be the inertial force of the indenter, and m be the mass of the indenter. This is the acceleration of the pressure head.

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