A high temperature dynamic strain testing system and method

Abstract

This invention discloses a high-temperature dynamic strain testing system and method, relating to the field of high-temperature vibration testing and strain measurement technology. The system includes a high-temperature loading measurement unit, a signal extension shielding wire, and a signal conditioning unit. The high-temperature loading measurement unit comprises a high-temperature strain gauge and a compensation gauge respectively attached to the test specimen and the auxiliary specimen, connected via a five-wire connection through a common ground layer. The signal conditioning unit employs a symmetrically arranged dual constant current source power supply and a differential amplification structure to effectively suppress sensitivity deviation and common-mode noise interference caused by changes in lead resistance. The method accurately locates the maximum strain point through a combination of finite element simulation and experiment, and directly converts the dynamic resistance signal using constant current excitation to achieve accurate acquisition of strain signals under high-temperature vibration conditions. This invention solves the problems of significant influence of lead resistance and insufficient noise suppression capability in traditional measurements, achieving high-precision and high-reliability measurement of dynamic strain in high-temperature components such as aero-engine blades.

Description

Technical Field

[0001] This invention relates to the field of high-temperature vibration testing and strain measurement technology, and in particular to a high-temperature dynamic strain testing system and method. Background Technology

[0002] With increasingly stringent reliability requirements for high-temperature components such as aero-engine blades under extreme operating conditions, high-temperature dynamic strain testing technology has become a key means of evaluating their vibration fatigue performance. Traditional high-temperature dynamic strain measurement mainly relies on direct measurement methods using Wheatstone bridges combined with high-temperature strain gauges, or indirect measurement methods based on the room-temperature equivalence assumption. While direct measurement methods theoretically offer direct response and high accuracy, they face numerous challenges in practical high-temperature vibration environments: the high-temperature strain gauge bonding process is complex, costly, and prone to damage; changes in resistance over long distances lead to sensitivity drift and zero-point instability; and asymmetrical signal acquisition paths make it difficult to fully utilize the common-mode noise suppression capability of differential amplifiers, resulting in a decrease in signal-to-noise ratio. Indirect measurement methods, by neglecting changes in parameters such as the elastic modulus and Poisson's ratio of materials at high temperatures, fail to accurately reflect the high-temperature strain field distribution, leading to widespread skepticism regarding data reliability. Therefore, there is an urgent need to develop a system and method capable of achieving high-precision and high-stability dynamic strain measurement under high-temperature vibration environments.

[0003] CN116539260A discloses a "High-Temperature Strain Gauge Vibration Fatigue Testing Device and Method." This device, through a combination of fixtures, a high-temperature heating furnace, vibration equipment, and a data acquisition system, enables fatigue life testing of high-temperature strain gauges under vibration loads. Its core lies in using the data acquisition system to monitor the strain waveform in real time and determine whether the strain gauge has suffered fatigue failure. However, this scheme is still based on the traditional Wheatstone bridge measurement architecture, failing to address the sensitivity deviation and zero drift issues caused by changes in lead resistance. Furthermore, it does not employ a symmetrical signal path design, resulting in insufficient common-mode noise suppression capability and making it difficult to achieve accurate dynamic strain measurement in high-noise, high-interference high-temperature vibration environments.

[0004] CN115096719B proposes a "High-Temperature Two-Way Mechanical Property Testing System and Method." This system combines laser heating, non-contact strain measurement, and two-way loading to test the mechanical properties of specimens under high temperature and multi-directional loads. Its advantages include rapid heating and good observability; however, this approach is primarily geared towards static or quasi-static mechanical property testing and is not suitable for dynamic strain measurement under high-frequency vibration environments. While its non-contact measurement method avoids the high-temperature processing difficulties associated with bonded strain gauges, it is susceptible to coupling interference between displacement and temperature fields under vibration environments, making it difficult to achieve high signal-to-noise ratio dynamic strain signal acquisition. This makes it particularly unsuitable for vibration fatigue testing of small-sized, high-frequency response structures such as aero-engine blades.

[0005] Existing high-temperature dynamic strain measurement technologies generally suffer from problems such as significant influence of lead resistance, weak common-mode noise suppression, complex high-temperature patch manufacturing processes, and insufficient measurement accuracy under high-temperature and vibration coupling environments. This invention provides a high-temperature dynamic strain testing system and method that enables high-precision and high-reliability measurement of dynamic strain in high-temperature components such as aero-engine blades during vibration fatigue testing. Summary of the Invention

[0006] The purpose of this section is to outline some aspects of the embodiments of the present invention and to briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section, as well as in the abstract and title of the present application, to avoid obscuring the purpose of this section, the abstract and title of the invention. Such simplifications or omissions shall not be used to limit the scope of the present invention.

[0007] In view of the problems of existing high-temperature dynamic strain measurement technology, such as significant influence of lead resistance, weak common-mode noise suppression capability, and insufficient measurement accuracy under high-temperature environment, this invention is proposed.

[0008] Therefore, the problem to be solved by this invention is how to provide a high-precision and high-stability high-temperature dynamic strain measurement scheme to effectively suppress sensitivity deviation and zero-point drift caused by changes in lead resistance, enhance the common-mode noise suppression capability of the measurement system under high-temperature vibration environment, and achieve accurate and reliable acquisition of dynamic strain signals.

[0009] To solve the above-mentioned technical problems, the present invention provides the following technical solution: In a first aspect, embodiments of the present invention provide a high-temperature dynamic strain testing system, which includes a high-temperature loading measurement unit 101, a signal extension shielding line 102, and a signal conditioning unit 103, wherein... The high-temperature loading measurement unit 101 includes a high-temperature strain measuring plate 104 and a high-temperature strain compensation plate 105; the high-temperature strain measuring plate 104 is attached to the maximum strain position of the test specimen 206; the high-temperature strain compensation plate 105 is attached to the auxiliary test specimen 211 made of the same material as the test specimen 206 for temperature compensation. The signal conditioning unit 103 includes two symmetrically arranged current sources 107 and 108, a differential amplifier 109, and a filter 110; the current sources 107 and 108 respectively supply power to the high-temperature strain measuring plate 104 and the high-temperature strain compensation plate 105 through the signal extension shielding line 102. One end of the leads of the high-temperature strain measuring plate 104 and the high-temperature strain compensation plate 105 are combined and connected to the ground terminal of the signal conditioning unit 103 through the shielding layer of the signal extension shielding line 102. The other end of the leads of the high-temperature strain measuring plate 104 and the high-temperature strain compensation plate 105 are connected to the signal input port of the signal conditioning unit 103 through the signal extension shielding line 102 respectively. The two signal input terminals of the differential amplifier 109 are respectively connected to the signal input port, and are used to perform differential amplification processing on the signals collected by the high-temperature strain measuring instrument 104 and the high-temperature strain compensation instrument 105.

[0010] As a preferred embodiment of the high-temperature dynamic strain test system of the present invention, the signal extension shielding line 102 is a four-core shielded cable, which is connected to the high-temperature loading measurement unit 101 and the signal conditioning unit 103 by a five-wire connection method.

[0011] As a preferred embodiment of the high-temperature dynamic strain testing system of the present invention, it further includes: a vibration table 213, a vibration transmission fixture 210, a heat insulation device 209, a high-temperature furnace 201, a displacement sensor 208, and a vibration controller 207; the test specimen 206 is rigidly fixed on the vibration table 213 by the vibration transmission fixture 210 and the heat insulation device 209; the high-temperature furnace 201 is used to apply a high-temperature environment to the test specimen 206; the displacement sensor 208 collects the amplitude signal of the test specimen 206 in real time and transmits it to the vibration controller 207; the vibration controller 207 processes and calculates the signal to generate a driving signal to drive the vibration table 213 to generate vibration excitation.

[0012] In a preferred embodiment of the high-temperature dynamic strain test system of the present invention, the accompanying specimen 211 is supported and fixed by the support device 212 and placed together with the test specimen 206 into the high-temperature furnace 201, and the accompanying specimen 211 and the test specimen 206 are at the same horizontal height.

[0013] In a preferred embodiment of the high-temperature dynamic strain testing system of the present invention, the high-temperature strain measuring plate 104 and the high-temperature strain compensation plate 105 are attached in the following manner: Apply cement adhesive to the patch location to form an insulating substrate 303; High-temperature strain gauge 104 is attached to the insulating substrate 303 using high-temperature ceramic adhesive, and high-temperature tape 305 is used to fix the lead wire 302 in sections. Cement adhesive is then applied to the lead wire 302 and cured by heating.

[0014] As a preferred embodiment of the high-temperature dynamic strain test system of the present invention, the current source 107 and the current source 108 provide constant current to excite the high-temperature strain measuring plate 104 and the high-temperature strain compensation plate 105, so that the dynamic resistance change caused by the high-temperature strain plate under vibration excitation is directly converted into voltage change and collected by the signal conditioning unit 103.

[0015] As a preferred embodiment of the high-temperature dynamic strain test system of the present invention, the two signal input terminals of the differential amplifier 109 are in the same temperature environment, the two signal lines are noise-coupled in the same way, and the differential amplifier 109 performs common-mode rejection to eliminate noise through a symmetrical connection topology.

[0016] Secondly, embodiments of the present invention provide a high-temperature dynamic strain testing method, comprising: Based on the dimensions of the test specimen 206, strain gauges were selected, and finite element simulation was performed on the test specimen model to obtain the stress distribution law. Based on the stress distribution law, a region with a gentle distribution was selected, and room temperature strain gauges were attached. Small amplitude vibration excitation was carried out on the specimen at the first resonant frequency of 206 at room temperature. Signal acquisition was performed based on a Wheatstone bridge. The output results of the room temperature strain gauges were statistically analyzed and used to guide the optimization of the simulation model. The location of maximum strain is obtained based on the optimized simulation results, and the specimen 206 is marked accordingly. The high-temperature strain gauge 104 is attached to the position of maximum strain of the test specimen 206, and the high-temperature strain compensation gauge 105 is attached to the auxiliary test specimen 211 made of the same material as the test specimen 206. A high-temperature dynamic strain test system was constructed, and a symmetrical connection topology and a five-wire connection method were used to connect the high-temperature loading measurement unit 101 and the signal conditioning unit 103. A constant current source is used to power the high-temperature strain gauge 104 and the high-temperature strain compensation gauge 105. A differential amplifier 109 is used to collect dynamic strain signals and conduct amplitude-stress calibration tests. Calculate the amplitude required for the fatigue test based on the calibration results.

[0017] As a preferred embodiment of the high-temperature dynamic strain test method of the present invention, the sensitive grid size of the strain gauge is not greater than 5 mm and is not greater than 1 / 10 of the length of the test piece 206.

[0018] As a preferred embodiment of the high-temperature dynamic strain test method of the present invention, the five-wire connection method is as follows: After the lead wires 302 of the high-temperature strain gauge 104 and the high-temperature strain compensation gauge 105 are combined, they are grounded through the shielding layer of the signal extension shielding wire 102. The current source 107 and the current source 108 in the signal conditioning unit 103 are connected to the signal extension shielding line 102 through port A and port D respectively, to power the high temperature strain measuring plate 104 and the high temperature strain compensation plate 105. On the same side of the high-temperature strain measuring plate 104 and the high-temperature strain compensation plate 105, the signal extension shielding line 102 is connected to ports B and C of the signal conditioning unit 103 to collect voltage signals.

[0019] Compared with existing technologies, the advantages of this invention are as follows: The use of a symmetrical connection topology and a five-wire connection method replaces the Wheatstone bridge for measurement, eliminating sensitivity deviation and zero drift caused by changes in strain gauge resistance during high-temperature measurements; the use of a constant current source to excite the strain gauge directly converts the dynamic resistance change caused by vibration excitation into a voltage change that is collected, and the voltage drop caused by the lead resistance does not affect the voltage acquisition of the strain gauge; the symmetrical connection topology ensures that the positive and negative terminals of the differential amplifier signal input are in the same temperature environment, and the noise coupling of the two signal lines is almost identical, enabling effective common-mode suppression to eliminate noise, improving the signal-to-noise ratio of the signal measurement, and meeting the requirements for high-precision dynamic strain measurement. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein: Figure 1 This is a schematic diagram of the connection topology of a high-temperature dynamic strain testing system; Figure 2 This is a schematic diagram of the high-temperature dynamic strain testing system. Figure 3 A schematic diagram of the high-temperature strain gauge bonding method in a high-temperature dynamic strain testing system; Figure 4 This is a flowchart of the high-temperature dynamic strain test method; In the figure: High-temperature loading measurement unit 101, signal extension shielded wire 102, signal conditioning unit 103, high-temperature strain gauge 104, high-temperature strain compensation gauge 105, lead resistor 106, current source 107, current source 108, differential amplifier 109, filter 110, high-temperature furnace 201, test specimen 206, vibration controller 207, displacement sensor 208, heat insulation device 209, vibration transmission fixture 210, test specimen 211, support device 212, vibration table 213, fixed base 301, lead wire 302, insulating substrate 303, high-temperature tape 305. Detailed Implementation

[0021] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0022] Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort should fall within the scope of protection of this invention.

[0023] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0024] As mentioned in the background section, existing high-temperature dynamic strain measurement technologies have significant shortcomings in terms of lead resistance compensation, common-mode noise suppression, and adaptability to high-temperature environments. To address these issues, this invention provides a high-temperature dynamic strain testing system.

[0025] Reference Figures 1-3 , Figure 1 This is a schematic diagram of the connection topology of a high-temperature dynamic strain testing system according to an embodiment of the present invention. Figure 1 As shown, the connection topology of a high-temperature dynamic strain test system includes, from left to right, a high-temperature loading measurement unit 101, a signal extension shielding line 102, and a signal conditioning unit 103.

[0026] Specifically, in the high-temperature loading measurement unit 101, the maximum strain gauge position is obtained using the following method: Strain gauges are selected based on the blade size; generally, the sensitive grid size of the strain gauge should not exceed 5mm (usually based on no more than 1 / 10 of the blade length); finite element simulation is performed on the obtained specimen model to obtain the stress distribution law; stress distribution tests are conducted based on the law; a region with a gentle distribution is selected, and a certain number of room-temperature strain gauges are attached; small-amplitude vibration excitation is carried out at the first-order resonant frequency of the specimen at room temperature; signal acquisition is performed based on a Wheatstone bridge; the output results of the room-temperature strain gauges are statistically analyzed to guide the optimization of the simulation model; simulation analysis is carried out again based on the optimized results to determine the maximum strain gauge attachment position; and the specimen is precisely marked with lines to indicate the strain gauge attachment position.

[0027] Furthermore, in this embodiment, two high-temperature strain gauges are selected. One of them is pasted at the marked position on the test specimen and is denoted as R1 (i.e., high-temperature strain measuring gauge 104). The other is pasted on a test specimen of the same material (for temperature compensation) and is denoted as R2 (i.e., high-temperature strain compensation gauge 105).

[0028] Furthermore, such as Figure 3 As shown, the method for attaching the high-temperature strain gauge is as follows: cement adhesive is applied to the attachment position to form an insulating substrate 303; high-temperature ceramic adhesive is used to attach the high-temperature strain gauge 104 to the insulating substrate 303; high-temperature tape 305 is used to fix the lead wire 302 in sections, and cement adhesive is applied to the lead wire 302 and cured by heating.

[0029] Specifically, such as Figure 2 As shown, the system also includes a vibration table 213, a vibration transmission fixture 210, a heat insulation device 209, a high-temperature furnace 201, a displacement sensor 208, and a vibration controller 207. A high-temperature strain gauge 104 is attached to the maximum strain position of the test specimen 206; a high-temperature strain compensation gauge 105 is attached to a companion specimen 211 made of the same material as the test specimen 206 for temperature compensation; the test specimen 206 is rigidly fixed to the vibration table 213 via the vibration transmission fixture 210 and the heat insulation device 209; the high-temperature furnace 201 is used to apply a high-temperature environment to the test specimen 206; the displacement sensor 208 collects the amplitude signal of the test specimen 206 in real time and transmits it to the vibration controller 207; the vibration controller 207 processes and calculates the signal to generate a drive signal that drives the vibration table 213 to generate vibration excitation.

[0030] Furthermore, the high-temperature strain gauge 104 is powered by the signal conditioning unit 103 via the signal extension shielding cable 102. Simultaneously, the high-temperature strain gauge 104 collects dynamic strain signals and transmits them to the signal conditioning unit 103 via the signal extension shielding cable 102. The test specimen 211 is supported and fixed by the support device 212 and placed together in the high-temperature furnace, with the test specimen 211 and the test specimen 206 at the same horizontal level. The temperature compensation strain collected by the high-temperature strain compensation gauge 105 is connected to the signal conditioning unit 103 via the signal extension shielding cable 102.

[0031] Furthermore, the signal conditioning unit 103 includes two symmetrically arranged current sources 107 and 108, a differential amplifier 109, and a filter 110; the current sources 107 and 108 supply power to the high-temperature strain measuring plate 104 and the high-temperature strain compensation plate 105 respectively through the signal extension shielding line 102.

[0032] Specifically, high-temperature strain acquisition uses a five-wire connection method, such as... Figure 1As shown, one end of the leads of the high-temperature strain gauge 104 and the high-temperature strain compensation gauge 105 are combined and then connected to the ground wire via the shielding layer of the signal extension shielding cable 102 at port E of the signal conditioning unit 103. Current sources 107 and 108 in the signal conditioning unit 103 are connected to the signal extension shielding cable 102 via ports A and D, respectively, to power the high-temperature strain gauge 104 and the high-temperature strain compensation gauge 105. On the same side of the high-temperature strain gauge 104 and the high-temperature strain compensation gauge 105, they are connected to ports B and C of the signal conditioning unit 103 via the multi-core signal extension shielding cable 102.

[0033] Furthermore, the signal extension shielded cable 102 is a four-core shielded cable with a length that meets the test requirements. One end is connected to the high-temperature loading measurement unit 101, and the other end is connected to each port of the signal conditioning unit 103.

[0034] Specifically, the signal conditioning unit 103 comprises input / output ports, an amplifier, a power supply, and a filter. The input / output ports include two symmetrically arranged strain gauge power supply ports A and D, signal input ports B and C, and a ground terminal E. The signal amplification uses a differential amplifier 109 with common-mode rejection ratio, current sources 107 and 108 are symmetrically arranged constant current sources, and the filtering unit is a filter 110 with low-pass filtering function.

[0035] Furthermore, in this embodiment, a symmetrically arranged constant current source is used to excite the high-temperature strain gauge 104. The current passing through the strain gauge remains constant. The dynamic resistance change caused by the vibration excitation of the high-temperature strain gauge 104 is directly converted into a voltage change and acquired by the signal conditioning unit 103. Regardless of whether the voltage drop generated by the lead resistor 106 is at high temperature or room temperature, it does not affect the voltage acquisition of the strain gauge, thus avoiding the sensitivity deviation problem caused by the voltage drop of the lead resistor in conventional Wheatstone bridge acquisition.

[0036] Furthermore, the high-temperature strain compensation gauge 105 only collects the strain caused by the resistance change due to temperature variation, and is used to compensate for the temperature strain of the high-temperature strain measuring gauge 104. In a conventional Wheatstone bridge, the signal input of the differential signal amplifier is exposed to high temperature at one end and to normal temperature at the other end in the signal conditioning unit, which has obvious defects, and the circuit coupling noise cannot be effectively suppressed or eliminated. In this embodiment, the positive and negative terminals of the differential amplifier signal input are in the same temperature environment, and the noise coupling of the two signal lines is almost the same. The symmetrical connection topology allows the differential amplifier to perform effective common-mode rejection and noise elimination, improving the signal-to-noise ratio of the signal measurement and meeting the requirements of high-precision dynamic strain measurement.

[0037] In summary, this invention employs a symmetrical connection topology and a five-wire connection method to replace the Wheatstone bridge for measurement, eliminating sensitivity deviation and zero drift caused by changes in the resistance of the strain extension line during high-temperature measurements. A constant current source is used to excite the strain gauge, and the dynamic resistance change caused by vibration excitation is directly converted into a voltage change and acquired. The voltage drop caused by the lead resistance does not affect the voltage acquisition of the strain gauge. The symmetrical connection topology ensures that the positive and negative terminals of the differential amplifier signal input are in the same temperature environment, and the noise coupling of the two signal lines is almost identical, enabling effective common-mode suppression and noise elimination, improving the signal-to-noise ratio of the signal measurement, and meeting the requirements for high-precision dynamic strain measurement.

[0038] Example 2 Reference Figure 4 This is the second embodiment of the present invention. Figure 4 Here is a flowchart of a high-temperature dynamic strain test method according to an embodiment of the present invention, as follows: Figure 4 As shown, this embodiment provides a high-temperature dynamic strain test, including: S1: Select strain gauges according to the 206 size of the test specimen, perform finite element simulation on the test specimen model, and obtain the stress distribution law; It should be noted that the size of the strain gauge's sensitive grid is no greater than 5 mm and no greater than 1 / 10 of the length of the test specimen 206.

[0039] S2: Select a region with a gentle distribution according to the stress distribution law, attach room temperature strain gauges, and conduct small amplitude vibration excitation of the test specimen at the first resonant frequency of 206 at room temperature. Collect signals based on Wheatstone bridge, statistically analyze the output results of the room temperature strain gauges, and guide the optimization of the simulation model. S3: Obtain the location of maximum strain based on the optimized simulation results and mark the specimen 206; S4: Attach the high-temperature strain gauge 104 to the position of maximum strain on the test specimen 206, and attach the high-temperature strain compensation gauge 105 to the auxiliary test specimen 211 made of the same material as the test specimen 206. S5: Construct a high-temperature dynamic strain test system, using a symmetrical connection topology and a five-wire connection method to connect the high-temperature loading measurement unit 101 and the signal conditioning unit 103; Preferably, the five-wire connection method is as follows: one end lead 302 of the high-temperature strain gauge 104 and the high-temperature strain compensation gauge 105 are combined and grounded through the shielding layer of the signal extension shielding line 102; the current source 107 and the current source 108 in the signal conditioning unit 103 are connected to the signal extension shielding line 102 through ports A and D respectively to supply power to the high-temperature strain gauge 104 and the high-temperature strain compensation gauge 105; on the same side of the high-temperature strain gauge 104 and the high-temperature strain compensation gauge 105, the signal extension shielding line 102 is connected to ports B and C of the signal conditioning unit 103 to collect voltage signals.

[0040] S6: Power the high-temperature strain gauge 104 and the high-temperature strain compensation gauge 105 with a constant current source, and use the differential amplifier 109 to collect dynamic strain signals to carry out amplitude-stress calibration test; S7: Calculate the amplitude required for the fatigue test based on the calibration results.

[0041] In an optional embodiment, after completing the amplitude-stress calibration test, at least three sets of corresponding stress data under different amplitudes need to be obtained. Based on these test data, the least squares method is used for linear fitting to establish a linear equation for the calibration relationship between amplitude and stress. This equation is generally expressed as y=kx+b, where y is the stress, x is the amplitude, and k and b are coefficients calculated through fitting. In actual fatigue tests, the preset target test stress value is substituted into this equation to calculate the corresponding test amplitude that needs to be applied.

[0042] Example 3 This is the third embodiment of the present invention, which provides a high-temperature dynamic strain testing system. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through economic benefit calculation and simulation experiments.

[0043] Specifically, the test subject was a high-temperature resistant metal standard specimen prepared according to aviation standard HB 5277, using a single-end fixed clamping method, and the test was conducted in a high-temperature environment of 600℃. The vibration excitation was provided by an electromagnetic vibration testing system, and the first-order resonant frequency of the specimen was determined by an initial frequency sweep as the subsequent excitation frequency.

[0044] Furthermore, during the experiment, both technical solutions attached 120Ω high-temperature strain gauges to the same location on the sample, ensuring that the lead type and length were completely consistent to control variables. Existing technologies use a Wheatstone bridge based on a half-bridge for measurement, while the present invention employs a complete system using the aforementioned symmetrical topology, constant current source excitation, and five-wire connection method. After applying constant amplitude excitation at the resonant frequency, dynamic strain signals were simultaneously acquired and recorded.

[0045] Furthermore, through statistical analysis of the measurement data, the three key indicators of normalized sensitivity, zero-point drift, and coupling noise were compared, as shown in Table 1. Specific data comparisons are as follows: the normalized sensitivity of the prior art is 0.23, the zero-point drift is -137.31 microstrain, and the coupling noise is -79.3 dB; while the corresponding results of the method of this invention are 0.98, -24.58 microstrain, and -101.6 dB, respectively. Calculation of the relative deviation shows that the present invention improves the deviation of the prior art by approximately 76.53% in terms of normalized sensitivity, improves the suppression of zero-point drift by approximately 458.62%, and enhances the noise suppression capability by approximately 21.95%.

[0046] Table 1. Statistical Comparison of Measurement Data between Existing Technologies and the Invention Existing technology 0.23 -137.31uε -79.3dB This invention 0.98 -24.58uε -101.6dB Statistical bias -76.53% -458.62% -21.95% In summary, the high-temperature dynamic strain testing system provided by this invention, through its unique symmetrical connection topology, constant current source excitation, and common-mode suppression design, effectively overcomes the inherent defects of the traditional Wheatstone bridge method, such as the significant influence of lead resistance and insufficient common-mode noise suppression under high-temperature conditions. It significantly improves the stability and accuracy of the measurement signal, providing a reliable technical means for the accurate measurement of structural dynamic strain under high-temperature conditions.

[0047] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A high temperature dynamic strain testing system, characterized by: It includes a high-temperature loading measurement unit (101), a signal extension shielded wire (102), and a signal conditioning unit (103), wherein, The high-temperature loading measurement unit (101) includes a high-temperature strain measuring plate (104) and a high-temperature strain compensation plate (105); the high-temperature strain measuring plate (104) is attached to the maximum strain position of the test specimen (206); the high-temperature strain compensation plate (105) is attached to a companion specimen (211) made of the same material as the test specimen (206) for temperature compensation; The signal conditioning unit (103) includes two symmetrically arranged first current sources (107) and second current sources (108), a differential amplifier (109), and a filter (110); the first current sources (107) and the second current sources (108) respectively supply power to the high-temperature strain measuring plate (104) and the high-temperature strain compensation plate (105) through the signal extension shielding line (102); One end of the leads of the high-temperature strain measuring plate (104) and the high-temperature strain compensation plate (105) are combined and connected to the ground terminal of the signal conditioning unit (103) through the shielding layer of the signal extension shielding line (102). The other end of the leads of the high-temperature strain measuring plate (104) and the high-temperature strain compensation plate (105) are connected to the signal input port of the signal conditioning unit (103) through the signal extension shielding line (102). The two signal input terminals of the differential amplifier (109) are respectively connected to the signal input port, and are used to perform differential amplification processing on the signals collected by the high temperature strain measuring plate (104) and the high temperature strain compensation plate (105); The signal extension shielded cable (102) is a four-core shielded cable, which is connected to the high-temperature loading measurement unit (101) and the signal conditioning unit (103) using a five-wire connection method. The vibration table (213), vibration transmission fixture (210), heat insulation device (209), high temperature furnace (201), displacement sensor (208), and vibration controller (207) are used to apply a high temperature environment to the test piece (206). The test piece (206) is rigidly fixed on the vibration table (213) by the vibration transmission fixture (210) and the heat insulation device (209). The high temperature furnace (201) is used to apply a high temperature environment to the test piece (206). The displacement sensor (208) collects the amplitude signal of the test piece (206) in real time and transmits it to the vibration controller (207). The vibration controller (207) processes and calculates the signal to generate a drive signal to drive the vibration table (213) to generate vibration excitation.

2. The high temperature dynamic strain testing system of claim 1, wherein: The test specimen (211) is supported and fixed by the support device (212) and then placed together with the test specimen (206) into the high temperature furnace (201), and the test specimen (211) and the test specimen (206) are at the same level.

3. The high temperature dynamic strain testing system of claim 1, wherein: The high-temperature strain measuring plate (104) and the high-temperature strain compensation plate (105) are attached in the following manner: Apply cement adhesive to the patch location to form an insulating base (303). High-temperature strain gauge (104) is attached to the insulating substrate (303) using high-temperature ceramic adhesive, and the lead wire (302) is fixed in sections using high-temperature tape (305). Cement adhesive is then applied to the lead wire (302) and cured by heating.

4. The high temperature dynamic strain testing system of claim 1, wherein: The first current source (107) and the second current source (108) provide constant current to excite the high-temperature strain gauge (104) and the high-temperature strain compensation gauge (105), so that the dynamic resistance change caused by the high-temperature strain gauge under vibration excitation is directly converted into voltage change and collected by the signal conditioning unit (103).

5. The high temperature dynamic strain testing system of claim 1, wherein: The two signal input terminals of the differential amplifier (109) are in the same temperature environment, and the two signal lines are noise-coupled in the same way. The differential amplifier (109) can carry out common-mode rejection and noise elimination through the symmetrical connection topology.

6. A high-temperature dynamic strain testing method, based on the high-temperature dynamic strain testing system according to any one of claims 1 to 5, characterized in that: include, Based on the dimensions of the test specimen (206), strain gauges were selected, and finite element simulation was performed on the test specimen model to obtain the stress distribution law; Based on the stress distribution law, a region with a gentle distribution was selected, and room temperature strain gauges were attached. Small amplitude vibration excitation was carried out on the test specimen (206) at the first resonant frequency at room temperature. Signal acquisition was performed based on Wheatstone bridge, and the output results of the room temperature strain gauges were statistically analyzed to guide the optimization of the simulation model. The location of maximum strain is obtained based on the optimized simulation results, and the specimen (206) is marked accordingly; The high-temperature strain gauge (104) is attached to the maximum strain position of the test specimen (206), and the high-temperature strain compensation gauge (105) is attached to the auxiliary test specimen (211) made of the same material as the test specimen (206). A high-temperature dynamic strain test system was built, and a symmetrical connection topology and a five-wire connection method were used to connect the high-temperature loading measurement unit (101) and the signal conditioning unit (103). A constant current source is used to power the high-temperature strain gauge (104) and the high-temperature strain compensation gauge (105), and a differential amplifier (109) is used to collect dynamic strain signals to conduct an amplitude-stress calibration test. Calculate the amplitude required for the fatigue test based on the calibration results.

7. The high-temperature dynamic strain test method as described in claim 6, characterized in that: The sensitive grid size of the strain gauge is no greater than 5 mm and no greater than 1 / 10 of the length of the test specimen (206).

8. The high temperature dynamic strain test method of claim 6, wherein: The five-line connection method is as follows: After the lead wires (302) of the high temperature strain measuring gauge (104) and the high temperature strain compensation gauge (105) are combined, they are grounded through the shielding layer of the signal extension shielding wire (102); The first current source (107) and the second current source (108) in the signal conditioning unit (103) are connected to the signal extension shielding line (102) through port A and port D respectively, to supply power to the high temperature strain measuring plate (104) and the high temperature strain compensation plate (105); On the same side of the high-temperature strain measuring plate (104) and the high-temperature strain compensation plate (105), the voltage signal is collected by connecting the signal extension shielding line (102) to the port B and port C of the signal conditioning unit (103).

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