Temperature compensation-based laser-ultrasonic high-temperature stress on-line detection system and method

Abstract

This invention relates to a temperature-compensated laser-ultrasonic online high-temperature stress detection system and method, belonging to the field of industrial process and equipment damage detection technology. The system integrates a pulsed laser, laser interferometer, and infrared thermometer on an air-bearing vibration isolation platform via an optical path control platform to achieve grid path scanning of complex-shaped workpiece surfaces. First, the invention establishes a three-dimensional mapping database of sound velocity, stress, and temperature by performing multi-dimensional tests on the tested parts. Then, for service workpieces with existing material data, the real-time temperature and ultrasonic signals of the tested parts are simultaneously acquired, and a stress calculation algorithm is executed based on the database. This invention eliminates multi-factor interference in complex service environments, accurately plots the surface stress distribution of the tested parts, and generates a condition assessment report, providing a high-precision in-situ online assessment method for industrial process and equipment damage detection.

Description

Technical Field

[0001] This invention belongs to the field of industrial process and equipment damage detection technology, specifically relating to a temperature-compensated laser ultrasonic high-temperature stress online detection system and method. Background Technology

[0002] Traditional stress testing methods (such as patch strain gauges and X-ray diffraction) mostly rely on contact measurements or have stringent environmental requirements. They suffer from insufficient adaptability and difficulty in achieving online monitoring in complex industrial environments with high temperatures, high pressures, and corrosion. In recent years, laser ultrasonic non-destructive testing technology has rapidly developed as an emerging non-contact testing technique. It uses lasers to excite ultrasonic waves in the material under test and performs interferometric detection. Laser ultrasonic technology offers the advantage of flexibility in adapting to various conditions, shapes, and materials, enabling in-situ testing of target objects in extreme environments. It shows great potential in areas such as defect detection and material condition monitoring.

[0003] During long-term, complex service operations, industrial equipment is prone to stress concentration or deterioration of stress state in the tested parts due to thermomechanical coupling. The evolution of these stresses directly affects the safety performance and service life of the equipment. Effective and accurate online detection of the stress distribution on the surface of the tested parts can significantly improve the reliability and risk prevention capabilities of industrial equipment. However, existing laser ultrasonic stress detection technologies are mostly focused on detection under ideal laboratory conditions at room temperature. Technologies for assessing the stress state of tested parts under complex service environments are still lagging behind. Specifically: on the one hand, high-temperature environments cause drastic fluctuations in the ultrasonic velocity within materials. This temperature-induced change in sound velocity severely masks and interferes with the subtle changes in sound velocity caused by stress variations, making it difficult to accurately infer the true stress value. On the other hand, actual tested parts often have irregular and complex surface shapes, making conventional fixed detection methods difficult to adapt to their geometric characteristics, further increasing the difficulty of stable in-situ signal acquisition and full coverage of detection points. Therefore, how to eliminate multi-factor interference and achieve accurate in-situ high-temperature stress state detection of irregular tested parts under complex service environments has become a major challenge in the field of industrial process and equipment damage detection. Summary of the Invention

[0004] In view of the above-mentioned problems in the prior art, the purpose of the present invention is to provide a temperature-compensated laser ultrasonic high-temperature stress online detection system and method.

[0005] This invention provides the following technical solution: a temperature-compensated laser ultrasonic high-temperature stress online detection system, comprising an air-floating vibration isolation platform, an optical path control platform, a pulsed laser, a laser interferometer, an infrared thermometer, and a PC. The pulsed laser, laser interferometer, and infrared thermometer are integrated on the optical path control platform, which is located on the air-floating vibration isolation platform. The pulsed laser emits an excitation beam that irradiates the surface of the part under test to excite an ultrasonic signal. The laser interferometer irradiates a detection beam that irradiates the surface of the part under test to collect ultrasonic vibration signals. The infrared thermometer simultaneously collects real-time temperature signals of the detection area. The PC controls the synchronous operation of the excitation, detection, and temperature measurement components through a control synchronizer and acquires digital ultrasonic and temperature signals through a data acquisition card. Under the control of the PC, the optical path control platform drives the pulsed laser, laser interferometer, and infrared thermometer to scan the surface of the part under test according to a set grid path.

[0006] In a preferred embodiment of the present invention, the air-bearing vibration isolation platform is connected to a regulated air source to eliminate vibration interference from the on-site environment; the pulsed laser is connected to a laser power supply; and the control synchronizer and data acquisition card are connected to a PC via an electrical / gas power supply line, an acquisition circuit, or a control circuit, respectively.

[0007] The temperature-compensated laser-ultrasound online high-temperature stress detection method, using the aforementioned laser-ultrasound detection system, includes the following steps: Step 1: First, integrate the pulsed laser, laser interferometer, and infrared thermometer onto the optical path control platform. Adjust the detection optical axis of the laser interferometer and the temperature measurement optical axis of the infrared thermometer so that they intersect at the same position on the surface of the part being measured, ensuring that the detection point of the ultrasonic signal and the temperature monitoring point strictly coincide.

[0008] Step 2: The PC sets the laser's trigger pulse frequency, the data acquisition card's sampling rate, and the initial coordinates of the optical path control platform via the control synchronizer. Based on the geometric model of the part being measured, the scanning grid step size is preset in the software.

[0009] Step 3: Install the test part with unknown material properties onto the stress loading device, and attach a resistance ceramic heating plate to the back or side of the test part to simulate the real thermo-mechanical coupling condition of the test part.

[0010] Step 4: Use a PC to control the heating plate to perform isothermal step heating, and set the current temperature node to T. i The real-time temperature of the surface of the part being tested is monitored by an infrared thermometer until the temperature fluctuation stabilizes within a preset minimum error range, thus completing the preparation for thermal equilibrium at the current temperature.

[0011] Step 5: At the current temperature node T iWhile maintaining a constant stress level, the driving stress loading device applies a gradient stress σ of the current level to the tested part. j The feedback signal from the stress sensor ensures that the load reaches the preset value and remains under pressure, thus eliminating interference from mechanical relaxation on sound velocity measurement.

[0012] Step 6: At the current temperature T i With stress σ j Under dual steady-state conditions, the PC-driven optical path control platform performs gridded scanning according to a preset two-dimensional coordinate system. Specifically, the optical path control platform drives the excitation beam and the detection / temperature measurement components at a set spatial step size. It moves along a preset path within the target area of ​​the part being measured. When the probe / temperature measuring optical axis reaches each planned grid node (x... k ,y k At this time, the PC sends a pulse trigger signal through the control synchronizer, and the system synchronously completes the emission and excitation of the pulsed laser, the ultrasonic detection of the laser interferometer, and the local temperature sampling of the infrared thermometer. Subsequently, the PC records the spatial coordinates (x, y) of this node. k ,y k ), current steady-state conditions (T) i ,σ j The corresponding original ultrasonic wave data is arrayed, bound, and stored until the scan covers the entire preset test area.

[0013] Step 7: After completing the current mesh scan, automatically change the stress to the next level σ. j+1 Then, repeat steps 5 and 6 until all stress gradients at the current temperature have been detected. Afterward, change the temperature to the next node T. i Repeat steps 4 to 6 until the entire temperature and stress domains are covered, forming a multidimensional calibration raw dataset.

[0014] Step 8: Based on the Murnaghan nonlinear elastic constitutive model, perform physical back-calculation on the calibration data. By analyzing the linear shift rate of sound velocity with stress, extract the second-order elastic constants (Lame constants λ, μ) and third-order elastic constants (Murnaghan constants l, m, n) of the material, thereby explaining the physical mechanism by which the microscopic nonlinear response of the material causes the sound velocity to change with stress.

[0015] Step 9: Using the physical constants extracted in Step 5, fit the zero-stress sound velocity regression curve v0(T) as a function of temperature. i ) and acoustic elastic coefficient curve K(T) i These parameters are stored in the PC's calibration database as vector matrices, and the temperature-compensated sound velocity-stress inversion equation is established: σ=(v measured -v0(Ti )) / K(T i ).

[0016] Step 10: In the field industrial service environment, import the calibration database into the PC, control the optical path control platform to move to the initial measurement point (x0, y0), and the infrared thermometer synchronously collects the current service temperature T. actual The laser component acquires ultrasonic signals, and the PC extracts the sound time and calculates the current sound velocity v. actual The optical path control platform moves the laser and temperature measurement components along a preset grid path. The PC drives the actuators via a control synchronizer to complete the synchronous excitation and detection of each node.

[0017] Step 11: At each detection node, the system synchronously acquires the real-time service temperature T. i And ultrasonic signals. The PC first extracts the velocity of sound v, which is currently affected by the temperature field disturbance. actual Subsequently, the system makes real-time calls to the database related to T. actual Substituting the corresponding compensation parameters v0 and K into the inversion equation, the interference of sound velocity fluctuations is eliminated, and the true stress value σ is calculated. actual .

[0018] Step 12: After completing the full-field scan, the PC matches the stress values ​​of each node with their spatial coordinates to construct a stress distribution matrix. The system automatically generates a three-dimensional stress distribution cloud map of the measured surface and identifies stress concentration areas.

[0019] In a preferred embodiment of the present invention, the laser excitation and detection process in steps 6 and 10 is as follows: After the optical path control platform is hovered and stabilized, the infrared thermometer prioritizes synchronously acquiring the local steady-state temperature of the node, while the laser interferometer emits a continuous probe beam, continuously illuminating and focusing on the detection point position of the node; subsequently, the PC sends a main trigger command to the data acquisition card through the control synchronizer, causing the data acquisition card to enter the pre-trigger recording state first and begin recording the reference back noise signal of the interferometer; after the data acquisition card starts recording or after a preset hardware delay, the control synchronizer triggers the pulsed laser to emit a nanosecond-level laser pulse to the preset excitation point, which excites ultrasonic waves based on the thermoelastic effect; the ultrasonic waves propagate to the detection point on the surface or inside of the tested part, and the resulting small high-frequency vibrations on the surface are captured in real time by the laser interferometer in the irradiation state and converted into electrical signals that are completely recorded by the data acquisition card; at this point, the PC records the spatial coordinates (x, y) of the node. k ,y k The temperature, stress state, and complete ultrasonic waveform are arrayed and bound for storage. Then, the optical path control platform moves to the next node until the full-area mesh scan under this steady state is completed.

[0020] In a preferred embodiment of the present invention, the detailed transformation logic for the sound velocity acquisition and stress inversion processes in steps 4, 6, and 10 is as follows to eliminate global path accumulation error:

[0021] The raw data acquired by the laser interferometer is a voltage signal reflecting the vibration displacement of particles on the surface of the measured part. Since the single-point measurement method can only obtain the macroscopic average sound velocity in the interval from the excitation point to the detection point, it cannot accurately reflect the local stress concentration under complex working conditions. Therefore, this system uses the differential time-of-flight algorithm to extract the true local sound velocity.

[0022] Specifically, in the optical path scanning plan, the detection sequence of the probe points starts from the reference monitoring point closest to the excitation point and proceeds in small increments along the direction of ultrasonic propagation. The PC first identifies the synchronization trigger signal time t. start Subsequently, for the (k-1)th monitoring point and the kth monitoring point (the current point to be measured) adjacent to each other on the propagation path, the PC extracts the characteristic time t of the ultrasonic wave arriving at these two locations using either a cross-correlation algorithm or the envelope peak method. arrival,k-1 With t arrival,k .

[0023] Let ∆L be the fixed, tiny spatial step size between these two adjacent monitoring points. Then, the transit time difference of the ultrasound within this local tiny interval is: .

[0024] Thus, the cumulative interference from the front-end propagation path is eliminated, and the real-time sound velocity v corresponding precisely to the local area where the k-th monitoring point is located is calculated. i .

[0025] In a preferred embodiment of the present invention, the three-dimensional mapping relationship between sound velocity, stress, and temperature in step 6 and the stress calculation algorithm in step 11 are based on the Murnaghan nonlinear elastic constitutive model. This model, by introducing third-order elastic constants, reveals the acoustic response characteristics of the tested part under the coupled action of a high-temperature thermal field and a stress field from a microscopic physical mechanism perspective. Its specific logic is as follows: Unlike traditional linear theories that only consider the second-order Lamé constants (λ, μ), this invention preferably employs the strain energy density function Փ expansion that includes the Murnaghan third-order elastic constants (l, m, n). Here, l reflects the sensitivity of volume change to the stress field, m reflects the coupling effect between shear deformation and volume change, and n reflects the contribution of pure shear deformation to the nonlinear response. The introduction of the third-order constants aims to accurately capture the minute sound velocity shift generated by laser ultrasound under stress, which is a physical prerequisite for achieving high-precision stress detection. Acoustic elastic coefficient shift mechanism under high-temperature conditions: In the complex service environment detection of this invention, the acoustoelastic coefficient K is not a constant value, but a function of temperature T, K(T). According to the Hughes-Kelly acoustoelastic equation, the longitudinal wave velocity V... L The quantitative relationship with stress σ is modulated by both second- and third-order elastic constants. Since λ, μ, l, m, and n all drift with temperature T, the acoustic elastic coefficient K(T) exhibits a significant temperature dependence. ; ; .

[0026] In a preferred embodiment of the present invention, for test parts with known material properties and whose Murnaghan constitutive constants and acoustoelastic characteristics have been pre-calibrated, the PC contains a complete calibration database for that material. In this application scenario, after completing steps 1 and 2 of system deployment and parameter initialization, the system can directly skip the thermo-coupling calibration process from steps 3 to 9 and proceed directly to step 10 to perform adaptive scanning of irregular surfaces on-site. In step 11, it can directly call v0(T) from the existing database. i ) and K(T i The parameters are used to complete real-time temperature compensation and stress calculation.

[0027] The specific stress inversion algorithm model is as follows: ; Among them, v actual The local real sound velocity of the current node is acquired synchronously; T actual The local real-time service temperature of the current node is synchronously collected by the infrared thermometer (5); v0(T) actual To retrieve data from the calibration database related to temperature T actual The corresponding zero-stress reference sound velocity; K(T) actual To retrieve data from the calibration database related to temperature T actual The corresponding acoustoelastic coefficient modulated by Murnaghan's third elastic constant.

[0028] By employing the above-described technology, the beneficial effects of the present invention compared to the prior art are as follows: 1) This invention integrates an infrared thermometer and laser ultrasonic detection, and utilizes a pre-established temperature compensation calibration database to call compensation parameters corresponding to the current service temperature in real time during in-situ detection. This effectively eliminates the interference of sound velocity fluctuations caused solely by high temperature in complex service environments and solves the problem of stress inversion distortion caused by high temperature.

[0029] 2) This invention utilizes an optical path control platform to drive a pulsed laser, a laser interferometer, and an infrared thermometer to scan along a preset grid path, overcoming the limitations of conventional fixed detection methods that are difficult to adapt to complex geometric shapes, and realizing adaptive path planning and non-contact full-coverage detection of irregularly shaped test parts.

[0030] 3) Based on the Murnaghan nonlinear elastic constitutive model and the Hughes-Kelly acoustoelastic equation, this invention accurately describes the microscopic nonlinear acoustic response characteristics of materials under the coupling effect of high-temperature thermal field and stress field by introducing third-order elastic constants. Compared with the traditional linear theory that only considers second-order constants, it improves the physical accuracy and detection precision of stress inversion.

[0031] 4) This invention coordinates the synchronous operation of the excitation, detection and temperature measurement components by controlling the synchronizer, and completes the automatic acquisition and array binding storage of digital signals by combining the data acquisition card. It realizes the full-process automation from grid scanning and synchronous data acquisition to the generation of three-dimensional stress distribution cloud map, which meets the needs of industrial sites for in-situ, online and non-destructive evaluation of key equipment components. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the connection and optical path principle of the online detection system of the present invention; Figure 2 This is a schematic diagram of the process for establishing a three-dimensional mapping relationship for the tested part in this invention; Figure 3 This is a schematic diagram of the distribution and scanning path of multiple stress monitoring points on the surface of the tested part in this invention; Figure 4 This is a schematic diagram of the process for on-site in-situ online testing and stress calculation of the tested part in this invention; Figure 5 This is a schematic diagram of the distribution of detection points on the surface of the part being tested and the scanning path in this invention. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0034] Conversely, this invention encompasses any substitutions, modifications, equivalent methods, and solutions made within the spirit and scope of the invention as defined in the claims. Furthermore, to provide a better understanding of the invention, certain specific details are described in detail below. However, those skilled in the art will fully understand the invention even without these detailed descriptions.

[0035] Example 1: A temperature-compensated laser-ultrasonic online high-temperature stress detection system, such as... Figure 1 As shown.

[0036] This device includes an air-float vibration isolation platform 2, on which an optical path control platform 1 is installed. The air-float vibration isolation platform 2 is connected to a regulated air source for vibration reduction.

[0037] A pulsed laser 3, a laser interferometer 4, and an infrared thermometer 5 are arranged on the side facing the part 11 under test. The pulsed laser 3 is connected to a laser power supply 15. The pulsed laser 3 is aligned with the surface of the part 11 under test to form an excitation optical path 6, the laser interferometer 4 is aligned with the surface of the part 11 under test to form an interference optical path 7, and the infrared thermometer 5 is aligned with the surface of the part 11 under test to form a temperature measuring optical path 8.

[0038] On the other side of the testing system, a stress loading device 9 is provided. The part to be tested 11 is vertically mounted on the stress loading device 9, and a resistance ceramic heating plate 10 is attached to the side of the part to be tested 11.

[0039] The pulsed laser 3, laser interferometer 4, and infrared thermometer 5 are all connected to the control synchronizer 14 via a control circuit. The laser interferometer 4 is connected to the data acquisition card 12 via a data acquisition circuit. Both the control synchronizer 14 and the data acquisition card 12 are connected to the PC 13. The PC 13 is also connected to the resistance ceramic heating plate 10 and the stress loading device 9 via a control circuit.

[0040] Example 2: A temperature-compensated online laser-ultrasonic high-temperature stress calibration method, such as... Figure 2 As shown in Figure 3, this embodiment details how to establish a high-precision temperature compensation calibration database using the device provided by this invention for an industrial alloy material undergoing initial testing.

[0041] Step 1: Hardware integration and environment initialization. For example... Figure 1As shown, the pulsed laser 3, laser interferometer 4, and infrared thermometer 5 are first integrated onto the optical path control platform 1, and this platform is then mounted on the surface of the air-bearing vibration isolation platform 2. The laser power supply 15 and the regulated gas source are connected to ensure that the system's environmental noise is controlled. The part to be tested 11 is mounted on the stress loading device 9, and a resistance ceramic heating plate 10 is attached to its back.

[0042] Step 2: PC 13 adjusts the displacement of optical path control platform 1 via synchronizer 14, ensuring that the detection point of laser interferometer 4 and the monitoring point of infrared thermometer 5 are spatially perfectly aligned. This is preset in the software as follows... Figure 3 The grid scanning path shown is configured with scanning step sizes of ∆x and ∆y, and the sampling frequency of the data acquisition card 12 is also set.

[0043] The hardware configuration and software scanning parameters corresponding to this step can be found in Table 1. Table 1 Initial Hardware and Scan Parameter Settings

[0044] Step 3: According to Figure 2 The process involves PC 13 controlling heating plate 10 to heat the part 11 under test to the first temperature node T. i The surface temperature field is monitored in real time by an infrared thermometer 5 until the temperature fluctuation in the detection area stabilizes within a preset error range (3%), thus completing the preparation for thermal equilibrium at the current temperature.

[0045] Step 4: At the current temperature T i Under constant conditions, the driving stress loading device 9 applies a gradient stress σ of the current level to the tested part 11. j Sensor feedback ensures the load reaches a preset value and remains under pressure for 1–3 minutes, preferably 2 minutes, to eliminate interference from mechanical relaxation on sound velocity measurement.

[0046] Step 5: Press the optical path control platform 1 Figure 3 Path movement, when the monitoring points of infrared thermometer 5 and laser interferometer 4 reach the grid node (x) k ,y k After stabilization, the infrared thermometer 5 prioritizes acquiring the local temperature; then the PC drives the data acquisition card 12 into a pre-trigger recording state; next, the pulsed laser 3 is triggered to emit nanosecond pulses to excite ultrasonic waves; finally, the laser interferometer 4 captures the surface vibration signal and records it by the data acquisition card 12. At this point, the PC has arrayed and bound the coordinates, temperature, stress, and original waveform for storage.

[0047] Step 6: After completing the current mesh scan, iteratively change the stress level σ. j+1 Or temperature node T i+1Repeat steps 3 to 5 until the entire temperature and stress domains are covered, forming a calibration dataset containing multiple sets of waveform data.

[0048] Step 7: Extract the ultrasonic velocity v of the dataset under each state. ij Based on the Murnaghan nonlinear elastic constitutive model, the shift of the material's second-order elastic constants (λ, μ) and third-order elastic constants (l, m, n) with temperature is analyzed, revealing the physical nature of the sensitivity of sound velocity to stress.

[0049] Step 8: Fit the zero-stress sound velocity regression curve v0(T) as a function of temperature. i ) and acoustic elastic coefficient curve K(T) i ), store it in the database, and generate the temperature compensation inversion equation σ=(v measured -v0(T i )) / K(T i ).

[0050] Taking 6061 aluminum alloy as an example, the temperature, stress, and sound velocity data recorded during the calibration process, as well as the inversion results calculated from them, are detailed in Table 2: Table 2. Online calibration data for temperature-compensated laser-ultrasonic high-temperature stress.

[0051] Example 3: A temperature-compensated laser-ultrasonic online high-temperature stress detection method, such as... Figure 4 , 5 As shown in the figure. This embodiment details how to use an existing calibration database to perform rapid in-situ stress state assessment of test parts with complex geometries in industrial settings.

[0052] Step 1: As Figure 4 As shown, the testing system is deployed in the field environment. The corresponding material calibration database established in Example 1 is imported into PC 13. Since the material properties of the tested part 11 are known, the calibration step is skipped in this example.

[0053] Step 2: For example Figure 5 The irregularly shaped surface of the part being measured is shown. The PC 13 plans an adaptive scanning mesh path based on its geometric contour. The control synchronizer 14 drives the optical path control platform 1 to move to the initial measurement point (x) on the surface of the part being measured. i ,y i ).

[0054] Step 3: The system adopts the same timing control logic as in Example 1: the infrared thermometer 5 synchronously collects the current real-time service temperature T at the detection point. iThe pulsed laser 3 excites the ultrasonic signal, the laser interferometer 4 captures the surface vibration waveform caused by stress and temperature, and the data acquisition card 12 completes the digital recording.

[0055] Step 4: The system uses the differential time-of-flight algorithm to calculate the local precise sound velocity v by combining the transit time difference ∆t between adjacent monitoring points with the step size ∆L. i PC 13 is based on the measured temperature T i Retrieve the matching compensation parameter v0(T) from the database. i ) and K(T i Substituting this into the inversion equation σ=(v i -v0(T i )) / K(T i This eliminates the interference of sound velocity fluctuations caused by high temperature and calculates the true stress value.

[0056] Step 5: Repeat the above steps to complete. Figure 5 All grid nodes shown are inspected. PC 13 performs three-dimensional mapping between the spatial coordinates of each node and its stress value, drawing a three-dimensional stress distribution cloud map on the surface of the tested part 11. Finally, the system identifies stress concentration areas and generates an equipment health assessment report, completing the in-situ online inspection.

[0057] Taking a 6061 aluminum alloy workpiece as an example, the temperature at each node, local sound velocity, and stress values ​​obtained from database inversion during the field inspection process in Example 3 are detailed in Table 3: Table 3. Online detection data of high-temperature stress by laser-ultrasound with temperature compensation

[0058] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A temperature-compensated laser ultrasonic high-temperature stress online detection system, comprising an optical path control platform (1), an air-bearing vibration isolation platform (2), and a PC (13); characterized in that, The optical path control platform (1) is set on the air-floating vibration isolation platform (2). The optical path control platform (1) is equipped with a pulsed laser (3), a laser interferometer (4), and an infrared thermometer (5). The pulsed laser (3), the laser interferometer (4), and the infrared thermometer (5) are respectively aligned with the surface of the part under test (11) to form corresponding excitation optical path (6), interference optical path (7), and temperature measurement optical path (8). The PC (13) controls the synchronous operation of the pulse laser (3), laser interferometer (4) and infrared thermometer (5) through the control synchronizer (14), and acquires digital ultrasonic signals and temperature signals through the data acquisition card (12); and the PC (13) controls the movement of the optical path control platform (1), driving the pulse laser (3), laser interferometer (4) and infrared thermometer (5) to scan the surface of the part under test (11) along the set grid path.

2. The online laser ultrasonic high-temperature stress detection system based on temperature compensation according to claim 1, characterized in that, The air-floating vibration isolation platform (2) is connected to a regulated air source; the pulsed laser (3) is connected to a laser power supply (15); the control synchronizer (14) and the data acquisition card (12) are respectively connected to the PC (13) through circuits.

3. The online laser ultrasonic high-temperature stress detection system based on temperature compensation according to claim 1, characterized in that, When calibrating unknown material properties, the system also includes a stress loading device (9) and a resistance ceramic heating plate (10); the part to be tested (11) is mounted on the stress loading device (9), and the resistance ceramic heating plate (10) is attached to its side or back; the PC (13) is connected to the resistance ceramic heating plate (10) and the stress loading device (9) through a control circuit.

4. A temperature-compensated laser-ultrasonic online high-temperature stress detection method using the online detection system described in any one of claims 1-3, characterized in that, Includes the following steps: Step 1: Integrate the pulsed laser (3), laser interferometer (4) and infrared thermometer (5) on the optical path control platform (1), and adjust the detection optical axis of the laser interferometer (4) and the temperature measurement optical axis of the infrared thermometer (5) so that they intersect in space at the same position on the surface of the part to be measured (11). Step 2: Set the trigger pulse frequency of the laser, the sampling rate of the data acquisition card (12) and the initial coordinates of the optical path control platform, and preset the scanning grid step size according to the geometric model of the part under test (11); Step 3: If the material is unknown, the part to be tested (11) is mounted on the stress loading device (9), and a resistance ceramic heating plate (10) is attached to the part to be tested (11). Step 4: Control the heating plate (10) to perform isothermal step heating, raising the temperature to temperature node T. i And monitor the temperature until the temperature fluctuation stabilizes within the preset error range; Step 5: At the current temperature node T i While keeping the stress constant, apply the current grade of gradient stress σ to the tested part (11). j And maintain pressure; Step 6: At the current temperature T i With stress σ j Under the dual steady state, the driving optical path control platform (1) performs a gridded scan according to the preset two-dimensional coordinate system, and at each grid node (x k ,y k Simultaneously, pulsed laser emission excitation, ultrasonic shape detection, and local temperature sampling are completed at the location, and the spatial coordinates and steady-state conditions (T) are recorded. i ,σ j It is stored in conjunction with the original ultrasonic waveform data; Step 7: Change the stress level or temperature node, and repeat steps 4 to 6 to cover the entire temperature range and the entire stress range to form a multidimensional calibration raw dataset. Step 8: Based on the Murnaghan nonlinear elastic constitutive model, back-calculate the calibration data to extract the second-order and third-order elastic constants of the material; Step 9: Fit the zero-stress sound velocity regression curve v0(T) as a function of temperature. i ) and acoustic elastic coefficient curve K(T) i ), and establish the sound velocity-stress inversion equation for temperature compensation; step 10: In the field industrial service environment, import the calibration database and control the optical path control platform (1) to move according to the preset grid path, and synchronously collect the real-time service temperature T at each detection node. actual and ultrasound signals; Step 11: Extract the true sound velocity v of the current node affected by the temperature field disturbance. actual Call the database with T actual The corresponding compensation parameters v0 and K are substituted into the inversion equation to eliminate sound velocity fluctuation interference, and the true stress value σ is calculated. actual ; Step 12: After completing the full field scan, match the stress values ​​of each node with the spatial coordinates, construct the stress distribution matrix, and generate a three-dimensional stress distribution cloud map of the surface of the tested part (11).

5. The online laser ultrasonic high-temperature stress detection method based on temperature compensation according to claim 4, characterized in that, In steps 6 and 10, after the optical path control platform (1) hovers and stabilizes, the infrared thermometer (5) first synchronously collects the local steady-state temperature of the node, and at the same time, the laser interferometer (4) emits a continuous detection beam; then the PC (13) sends a main trigger command to the data acquisition card (12) through the control synchronizer (14), so that the data acquisition card (12) enters the pre-trigger recording state; after a preset hardware delay, the control synchronizer (14) triggers the pulse laser (3) to emit a nanosecond-level laser pulse; the ultrasonic wave propagates to the detection point and causes surface vibration, which is captured by the laser interferometer (4) and converted into an electrical signal and recorded by the data acquisition card (12).

6. The online laser ultrasonic high-temperature stress detection method based on temperature compensation according to claim 4, characterized in that, In step 6, the specific process of calculating the local sound speed using the differential time-of-flight algorithm is as follows: The detection sequence of the detection points starts from the reference monitoring point closest to the excitation point and proceeds in small increments along the direction of ultrasonic propagation. For the (k-1)th and kth monitoring points adjacent to each other on the propagation path, the characteristic time t of the ultrasonic wave reaching these two positions is extracted using a cross-correlation algorithm or the envelope peak method. arrival,k-1 With t arrival,k Based on a fixed spatial step size ΔL between adjacent monitoring points, the real-time sound velocity v of the corresponding local interval is calculated. i .

7. The online laser ultrasonic high-temperature stress detection method based on temperature compensation according to claim 4, characterized in that, In step 8, the Murnaghan nonlinear elastic constitutive model introduces a third-order elastic constant and combines it with the second-order Lamé constant. Based on the Hughes-Kelly acoustic elastic equation, a functional relationship between the acoustic elastic coefficient and temperature is established to quantify the acoustic response characteristics of the material under the coupling effect of high-temperature thermal field and stress field.

8. The online laser ultrasonic high-temperature stress detection method based on temperature compensation according to claim 4, characterized in that, In step 11, the real-time stress inversion algorithm model is a sound velocity-stress inversion equation based on temperature compensation. The measured sound velocity is calculated by calling the zero-stress reference sound velocity and acoustic elastic coefficient corresponding to the real-time service temperature of the current node.

9. The online laser ultrasonic high-temperature stress detection method based on temperature compensation according to claim 4, characterized in that, For the test part (11) with known material properties, after completing steps 1 and 2, the pre-stored calibration database is directly retrieved, skipping the calibration process from steps 3 to 9, and directly proceeding to step 10 to perform on-site testing.

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