Method for detecting mechanical properties of thick-walled precision forgings

Abstract

The present application relates to thick-walled forgings nondestructive testing and performance characterization technical field, disclose a kind of thick-walled precision forgings mechanical property detection method, method includes: engine cooperates with shear wave echo signal and longitudinal wave sound velocity, determine residual stress interference factor, and utilize interference factor to compensate or calibrate the absolute time difference of shear wave, to decouple and obtain a microstructure anisotropy index, and then determine mechanical property index, the present application utilizes the physical difference of longitudinal wave and shear wave to residual stress and microstructure response characteristics, by decoupling operation, microstructure anisotropy index is effectively separated from stress interference signal, so as to exclude the interference of residual stress.

Description

Technical Field

[0001] This invention relates to a method for testing the mechanical properties of thick-walled precision forgings, belonging to the field of non-destructive testing and performance characterization technology for thick-walled forgings. Background Technology

[0002] Currently, the service safety of thick-walled precision forgings in critical load-bearing components such as nuclear power pressure vessels and large steam turbine rotors is crucial to the operation of the entire system. The long-standing quality control standard in this field relies on destructive mechanical testing of sacrificial test bars. These test bars are those that undergo furnace heat treatment along with the forging body and are ultimately used for destructive mechanical testing. The purpose is to use the performance data of the test bar to represent the performance of the forging body. However, this industry-reliant core assumption—that the test bar and the body are equivalent in performance—is not physically equivalent. Due to geometric size effects, the cooling rate and stress evolution of thick-walled forgings (especially their core) during heat treatment, particularly quenching, are drastically different from those of small-sized test bars. This leads to unpredictable differences between the actual material structure and mechanical properties of the forging body, especially impact toughness, and the test data from the test bar.

[0003] Meanwhile, existing non-destructive testing methods, such as conventional ultrasonic testing, are designed to detect large discontinuous defects, such as cracks or inclusions. However, the measurement signals they use are not sensitive to the continuous evolution of material microstructure caused by the differences in heat treatment and forging processes, such as preferred grain orientation or residual stress distribution. To control the performance uncertainties caused by these process differences at their source, much research in this field has focused on improving the forging and heat treatment processes themselves, achieving desired low-stress or high-performance states through specific process paths. For example, Chinese invention patent CN101537466B discloses a high-performance... The proposed method for producing aluminum alloy rings with low residual stress relies on a specific process flow combining upsetting, ring rolling, and subsequent high-temperature water quenching with axial cold compression deformation. The technical approach involves pre-setting a set of process parameters to statistically control residual stress and mechanical properties. However, this process-path-dependent solution assumes that the process can be reproduced by a benchmark, but it avoids the unavoidable process fluctuations and size effects in the actual production of thick-walled forgings. Furthermore, it does not provide an in-situ, non-destructive testing method to verify whether residual stress has been effectively eliminated and whether the microstructure has reached its optimal state.

[0004] Therefore, the technical problem to be solved by this invention is how to provide a non-destructive, in-situ quantitative characterization of the anisotropic state inside a thick-walled forging body, and thereby establish a detection system related to key mechanical properties. Summary of the Invention

[0005] This invention provides a method for testing the mechanical properties of thick-walled precision forgings. Its main purpose is to solve the problem that existing technologies cannot non-destructively and quantitatively characterize the anisotropic state of the body of thick-walled forgings in situ, thus making it impossible to accurately evaluate their true mechanical properties.

[0006] To achieve the above objectives, the present invention provides a method for testing the mechanical properties of thick-walled precision forgings, the method comprising the following steps:

[0007] Step a: Excite shear wave pulses to the test area of ​​the forging through the broadband shear wave probe module and collect the echo signal. The echo signal contains fast wave echo peaks and slow wave echo peaks due to the acoustic anisotropy present in the forging.

[0008] Step b: Measure the longitudinal wave velocity of the forging in the test area along at least two orthogonal directions using a longitudinal wave probe module;

[0009] Step c involves connecting the acoustic birefringence solution engine to the broadband shear wave probe module and the longitudinal wave probe module. This is used to: calculate the absolute time difference between the fast wave echo peak and the slow wave echo peak based on the echo signal; determine the residual stress interference factor based on the longitudinal wave velocity; compensate or calibrate the absolute time difference based on the residual stress interference factor to decouple and obtain microstructure anisotropy indices; and determine the mechanical properties of the forging in the test area based on the microstructure anisotropy indices and the calibration model.

[0010] Preferably, in step c, the calibration model is established by performing destructive mechanical tests and birefringence measurements on the sacrificial test bar used for destructive testing. The calibration model is used to correlate the destructive test data of the sacrificial test bar with the microstructure anisotropy index.

[0011] Preferably, in step b, the longitudinal wave probe module is also used to measure the thickness of the forging in the area to be measured, and the acoustic birefringence calculation engine is also used to: normalize the microstructure anisotropy index based on the thickness before determining the mechanical performance index.

[0012] Preferably, the longitudinal wave probe module is used to measure thickness, specifically by measuring the longitudinal wave flight time. The acoustic birefringence calculation engine is also used to calculate the thickness L based on the longitudinal wave flight time and the known longitudinal wave velocity. The acoustic birefringence calculation engine is used to perform normalization processing, specifically by calculating the normalized anisotropy B, which follows the formula B = Δt / L, where Δt is the microstructure anisotropy index and L is the longitudinal wave velocity used to calculate the thickness.

[0013] Preferably, in step c, the acoustic birefringence calculation engine is also used to: measure the first amplitude of the fast echo peak and the second amplitude of the slow echo peak from the echo signal; calculate the attenuation anisotropy index based on the relationship between the first amplitude and the second amplitude; and determine the second mechanical property index of the forging related to the microscopic discontinuity in the test area based on the attenuation anisotropy index.

[0014] Preferably, in step c, the acoustic birefringence solving engine is also used to: extract the backscattering time window signal located after the shear wave pulse and before the fast wave echo peak from the echo signal, perform a statistical analysis algorithm on the backscattering time window signal to calculate the grain size characterization parameter, and determine the grain size of the forging in the test area based on the grain size characterization parameter.

[0015] Preferably, in step a, the broadband shear wave probe module is an electromagnetic acoustic transducer used to excite shear wave pulses under non-contact or dry coupling conditions.

[0016] Preferably, in step c, the calibration model is used to establish a quantitative correlation between the microstructure anisotropy index and the impact toughness or fatigue resistance of the forging.

[0017] Preferably, in step c, the acoustic birefringence calculation engine is also used to: determine the principal axis direction of residual stress in the test area of ​​the forging by analyzing the polarization information of the fast wave echo peak and the slow wave echo peak.

[0018] Preferably, in step c, the acoustic birefringence solution engine is used to calculate the absolute time difference, specifically by performing a signal processing based on a cross-correlation algorithm or a peak fitting algorithm on the echo signal to calculate the peak time of the fast wave echo peak and the slow wave echo peak, and to calculate the difference between the peak times.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] 1. By coordinating the broadband shear wave probe module and the longitudinal wave probe module, the physical mechanism of the difference between the longitudinal wave velocity and the shear wave velocity in response to the microstructure and residual stress of materials is utilized. The calculation engine is configured to calculate the interference factor contributed by residual stress based on the longitudinal wave velocity information, and use this interference factor to compensate or calibrate the mixed time difference information contained in the shear wave echo signal. This enables the separation and extraction of microstructure anisotropy indicators from the stress interference background. The final mechanical performance indicators are free from the interference of residual stress state, and the characterization results have a more direct and reliable physical correlation with the material microstructure.

[0021] 2. By enhancing the functionality of the acoustic birefringence calculation engine, the information in a single echo signal can be reused. While calculating the first mechanical performance index based on the time difference between the fast and slow echo peaks, the engine is also configured to calculate the second mechanical performance index characterizing attenuation anisotropy by utilizing the relationship between the fast and slow amplitudes in the same signal. This approach utilizes the different manifestations of the same physical phenomenon in the time and amplitude domains to obtain two types of information about the material's sound velocity anisotropy and attenuation anisotropy from a single acquisition, providing richer dimensions for evaluating forging performance.

[0022] 3. By coordinating the configuration of the longitudinal wave probe module, the uncertainty of the acoustic path caused by the complex curved surface or variable cross section of the forging is solved. The longitudinal wave probe module is used to measure the actual propagation acoustic path of the shear wave pulse in the area to be measured in situ. The acoustic birefringence calculation engine is configured to use the measured acoustic path to normalize the calculated absolute time difference of the fast and slow waves, thereby outputting an anisotropy index that eliminates the influence of geometric dimensions. This mechanism makes the accuracy of the detection results no longer dependent on the precise prior knowledge of the thickness of the forging, enabling the system to adapt to geometrically non-ideal working conditions and to have the ability to continuously scan the surface of the forging to obtain the anisotropic distribution. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the detection process for the coordinated decoupling of stress interference according to the present invention;

[0024] Figure 2 This is a comparison chart showing the effect of residual stress on total time difference and microstructure indices in this invention;

[0025] Figure 3 This is a schematic diagram of the system architecture and data flow of the detection system of the present invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0027] This invention provides a method for testing the mechanical properties of thick-walled precision forgings, the method comprising the following steps:

[0028] Step a: Excite shear wave pulses to the test area of ​​the forging through the broadband shear wave probe module and collect the echo signal. The echo signal contains fast wave echo peaks and slow wave echo peaks due to the acoustic anisotropy present in the forging.

[0029] Step b: Measure the longitudinal wave velocity of the forging in the test area along at least two orthogonal directions using a longitudinal wave probe module;

[0030] Step c involves connecting the acoustic birefringence solution engine to the broadband shear wave probe module and the longitudinal wave probe module. This is used to: calculate the absolute time difference between the fast wave echo peak and the slow wave echo peak based on the echo signal; determine the residual stress interference factor based on the longitudinal wave velocity; compensate or calibrate the absolute time difference based on the residual stress interference factor to decouple and obtain microstructure anisotropy indices; and determine the mechanical properties of the forging in the test area based on the microstructure anisotropy indices and the calibration model.

[0031] Preferably, in step c, the calibration model is established by performing destructive mechanical tests and birefringence measurements on the sacrificial test bar used for destructive testing. The calibration model is used to correlate the destructive test data of the sacrificial test bar with the microstructure anisotropy index.

[0032] Preferably, in step b, the longitudinal wave probe module is also used to measure the thickness of the forging in the area to be measured, and the acoustic birefringence calculation engine is also used to: normalize the microstructure anisotropy index based on the thickness before determining the mechanical performance index.

[0033] Preferably, the longitudinal wave probe module is used to measure thickness, specifically by measuring the longitudinal wave flight time. The acoustic birefringence calculation engine is also used to calculate the thickness L based on the longitudinal wave flight time and the known longitudinal wave velocity. The acoustic birefringence calculation engine is used to perform normalization processing, specifically by calculating the normalized anisotropy B, which follows the formula B = Δt / L, where Δt is the microstructure anisotropy index and L is the longitudinal wave velocity used to calculate the thickness.

[0034] Preferably, in step c, the acoustic birefringence calculation engine is also used to: measure the first amplitude of the fast echo peak and the second amplitude of the slow echo peak from the echo signal; calculate the attenuation anisotropy index based on the relationship between the first amplitude and the second amplitude; and determine the second mechanical property index of the forging related to the microscopic discontinuity in the test area based on the attenuation anisotropy index.

[0035] Preferably, in step c, the acoustic birefringence solving engine is also used to: extract the backscattering time window signal located after the shear wave pulse and before the fast wave echo peak from the echo signal, perform a statistical analysis algorithm on the backscattering time window signal to calculate the grain size characterization parameter, and determine the grain size of the forging in the test area based on the grain size characterization parameter.

[0036] Preferably, in step a, the broadband shear wave probe module is an electromagnetic acoustic transducer used to excite shear wave pulses under non-contact or dry coupling conditions.

[0037] Preferably, in step c, the calibration model is used to establish a quantitative correlation between the microstructure anisotropy index and the impact toughness or fatigue resistance of the forging.

[0038] Preferably, in step c, the acoustic birefringence calculation engine is also used to: determine the principal axis direction of residual stress in the test area of ​​the forging by analyzing the polarization information of the fast wave echo peak and the slow wave echo peak.

[0039] Preferably, in step c, the acoustic birefringence solution engine is used to calculate the absolute time difference, specifically by performing a signal processing based on a cross-correlation algorithm or a peak fitting algorithm on the echo signal to calculate the peak time of the fast wave echo peak and the slow wave echo peak, and to calculate the difference between the peak times.

[0040] Example 1: This example demonstrates the specific operation of the technical solution in a particular testing scenario. In the in-service testing of a large steam turbine rotor forging, the forging, due to long-term operation under high temperature and high stress conditions, exhibits uncertainties regarding the residual stress state and microstructure evolution related to material toughness in its critical core region. This region is a high-risk area for fatigue crack initiation. If conventional shear wave birefringence technology is used for single-parameter measurement, the testing system can only output the proportions of the residual stress component contributed by stress overload risk and the microstructure component contributed by the material's inherent toughness in an absolute time difference value, leading to physical ambiguity in the test results. To solve this measurement ambiguity problem, the thick-walled precision forging mechanical property testing system of this invention is used to perform in-situ characterization of the critical region of the rotor. The broadband shear wave probe module excites shear wave pulses and acquires echo signals. The acoustic birefringence calculation engine calculates the absolute time difference based on these echo signals. Subsequently, longitudinal waves... The probe module measures the longitudinal wave velocity along two orthogonal directions in the same test area. The acoustic birefringence calculation engine determines the residual stress interference factor based on the longitudinal wave velocity. The collaborative intervention of this longitudinal wave probe module provides the calculation engine with a physical reference for separating mixed signals. The calculation engine then executes a compensation or calibration algorithm, using the residual stress interference factor to perform baseline subtraction on the total absolute time difference. The acoustic birefringence calculation engine finally outputs two decoupled physical quantities in parallel: a high-amplitude residual stress interference factor and a medium-amplitude microstructure anisotropy index. The synergistic operation of longitudinal wave velocity measurement, which is insensitive to microstructure anisotropy, and shear wave time difference measurement, which is sensitive to both, solves the inherent contradiction that traditional single-parameter detection cannot distinguish between stress and microstructure contributions. The detection system is no longer limited to measuring a vague sum value, but redefines the problem as separating the signal by physical factors, providing the rotor with a dual, clear, and quantifiable safety assessment basis regarding stress state and material toughness.

[0041] Example 2: This example objectively verifies the technical effectiveness of the detection system of this invention compared to conventional ultrasonic birefringence technology in distinguishing residual stress interference and accurately characterizing microstructure anisotropy (toughness) within the framework of testing or analyzing materials by measuring their chemical or physical properties. Four groups of thick-walled forging samples with known initial state properties were prepared in the experiment, as follows: Sample A (low toughness, low stress): Low impact toughness was obtained by using an inappropriate heat treatment process (slow quenching), and sufficient annealing was performed to eliminate most of the residual stress; Sample B (low toughness, high stress): The same inappropriate heat treatment process as Sample A (low toughness) was used, but a high level of internal residual stress was introduced by subsequent mechanical loading; Sample C (high toughness, low stress): High impact toughness was obtained by using the same standard heat treatment process (standard quenching and tempering), and sufficient annealing was performed (low stress); Sample D (high toughness, high stress): The same standard heat treatment process as Sample C (high toughness) was used, and high residual stress similar to that of Sample B was introduced.

[0042] The experiment involved destructive testing of four groups of specimens to obtain their true mechanical performance benchmarks. Charpy V-notch impact tests were conducted on samples taken from the same location of each specimen to measure their actual impact toughness, a value primarily determined by the material's microstructure. A control group was set up for non-destructive testing comparison with the experimental group of this invention. The control group simulated conventional techniques: using only a broadband shear wave probe module to test the four groups of specimens, measuring and recording their (total) absolute time difference (Δt), a value resulting from the combined superposition of microstructure and residual stress effects. The experimental group of this invention employed the system: simultaneously using a broadband shear wave probe module and a longitudinal wave probe module to test the four groups of specimens. An acoustic birefringence calculation engine acquired shear wave echoes to calculate Δt and acquired longitudinal wave velocity in orthogonal directions. Based on the difference in longitudinal wave velocity, the engine calculated a residual stress interference factor and used this factor to compensate for or calibrate the total absolute time difference Δt, ultimately decoupling and outputting the microstructure anisotropy index (Δt). texture All ultrasonic measurements were performed at room temperature (20°C) using the same ultrasonic pulse transceiver (sampling frequency 100 MSa / s) and the same coupling agent to eliminate interference from environmental and instrument fluctuations. The measurement data are summarized in Table 1.

[0043] Table 1: Comparison of detection data between the control group and the experimental group of this invention

[0044]

[0045] Data analysis revealed that the data (Δt) from the control group using conventional techniques exhibited highly inconsistent results, failing to establish a valid correlation with the actual impact toughness benchmark. As shown in Table 1, the Δt value (39.1 ns) of sample B (low toughness, 41.5 J) was actually higher than that of sample C (high toughness, 112.1 J) (34.5 ns). This was because the high residual stress in sample B severely interfered with the Δt value, leading to distorted measurement results. The data from the experimental group of this invention showed a clear positive correlation with the actual impact toughness (benchmark). Referring to Table 1, the acoustic birefringence calculation engine utilized the residual stress interference factor to eliminate... Besides stress interference, low-toughness specimens A (7.9 ns) and B (8.4 ns) both exhibited low index values, while high-toughness specimens C (33.7 ns) and D (32.9 ns) both exhibited high index values. This index is completely consistent with the high-low distribution of the specimens' actual impact toughness (41.5-44.8 J vs 108.6-112.1 J). Experimental data confirms that the detection system of this invention, through the coordinated detection of the longitudinal wave probe module and the broadband shear wave probe module, and utilizing the acoustic birefringence calculation engine to perform physical decoupling, obtains the microstructure anisotropy index (Δt). texture This effectively avoids interference from residual stress measurement and can objectively reflect the mechanical properties of the thick-walled forging body determined by its microstructure.

[0046] Example 3: This example combines Figures 1 to 3 This document describes a method for testing the mechanical properties of thick-walled precision forgings, such as... Figure 1 As shown, the longitudinal wave probe module is used to measure the longitudinal wave velocity and forging thickness in orthogonal directions, while the broadband shear wave probe module is used to excite shear waves and acquire echo signals. The longitudinal wave velocity is used to determine the residual stress interference factor, a process based on longitudinal wave velocity calculation in orthogonal directions. The echo signal is used to calculate the absolute time difference, based on the fast and slow echo peaks. Thickness information is fed into a normalization process, which eliminates the influence of geometric dimensions based on the measured thickness. The interference factor and absolute time difference are fed into a compensation or calibration step, using the interference factor to adjust the absolute time difference. Decoupling is performed to output the decoupled time difference; the normalization step outputs the normalized result, which, together with the decoupled time difference, is used to obtain the microstructure anisotropy index, i.e., a pure index that has eliminated stress and geometric interference. On the other hand, a calibration model is established through destructive testing of sacrificial test bars. This calibration model is used as the model input. Finally, the microstructure anisotropy index and the calibration model are used to determine the mechanical performance index. This determination process correlates the anisotropy index and the calibration model to output the mechanical performance index, such as impact toughness or fatigue resistance.

[0047] like Figure 2As shown in the figure, the horizontal axis represents residual stress in megapascals (MPa), and the vertical axis represents time difference in nanoseconds (ns). The figure shows three data curves: the curve representing the total absolute time difference Δt (ns) shows an increasing trend with increasing residual stress (MPa); the curve representing the residual stress contribution component (ns) also shows an increasing trend with increasing residual stress; and the curve representing the microstructure anisotropy index Δt... texture The curve for (ns) remains nearly constant under different residual stress levels; for example... Figure 3 As shown, the integrated testing probe combines longitudinal wave and shear wave modules. It acts on the tested forging, such as a steam turbine rotor, through raw acoustic coupling and collects raw acoustic signals, which are then sent to a portable testing host. The portable testing host contains an acoustic birefringence solution engine, i.e., the core analysis software, and a calibration model, i.e., a configuration database. The calibration model is loaded into the solution engine, and the host transmits the results to a data analysis workstation. The data analysis workstation stores and archives the results and finally outputs a mechanical performance index test report.

[0048] Example 4: This example describes a standardized engineering procedure for offline calibration of an acoustic birefringence calculation engine to eliminate measurement uncertainties before testing or analyzing materials by measuring their chemical or physical properties. The challenge of this procedure is that the engine must establish a physical model to quantitatively remove stress interference from the total shear wave time, i.e., to repair the uncertainty of the decoupling algorithm, before it can use this pure index to establish a calibration model with the final mechanical properties (such as impact toughness) (i.e., to repair modeling uncertainties). The initial state of this procedure is defined as follows: the object of action is a set of 10 sacrificial test bars covering different toughness levels corresponding to different heat treatment processes, and at least one of them is denoted as stress. The calibration test bar underwent thorough annealing to eliminate initial stress. The enabling environment included a material testing machine with load application and monitoring capabilities and an accuracy better than 1 km, as well as the detection system of this invention, including a longitudinal wave probe module with a center frequency of 5 MHz and a broadband shear wave probe module of 2.5 MHz. The first stage of the calibration procedure was used to establish a decoupling algorithm model, and its operation flow is as follows: the stress calibration test bar was installed on the material testing machine; under zero load (σ = 0 MPa), the initial residual stress interference factor (F0, theoretical value close to 0) and the initial absolute time difference (Δt0) were measured and recorded using this system. Δt0 was calibrated as the pure microstructure anisotropy index Δt of the test bar. texture_base A series of gradient uniaxial tensile stresses (σ) are applied to the test bar along its axial direction. i The load is controlled within the elastic range of the material, such as 0 MPa, 50 MPa, 100 MPa, 150 MPa up to 250 MPa; at each stress σ iWith a constant load under horizontal conditions, the longitudinal wave probe module is synchronously driven to measure the longitudinal wave velocity along and perpendicular to the stress direction, and the residual stress interference factor F under this stress level is calculated. i It also drives the broadband shear wave probe module to measure the total absolute time difference Δt. i , Δt σi =Δt i -Δt texture_base The acoustic birefringence solution engine collects all (F i , Δt σi The data pairs were used, and based on the principle of acoustoelasticity, least squares linear fitting was performed on these data points to establish Δt. σ =k•F σ The physical model is defined, where k is the acoustoelastic scaling factor characterizing the material, determined through fitting; thus, the compensation or calibration algorithm within the engine is determined as Δt. texture =Δt total -k•F σ , where Δt total F is the total time difference at any point to be measured. σ It is the residual stress disturbance factor, Δt texture It is the final output of the microstructure anisotropy index.

[0049] The second stage of the calibration procedure is used to establish a mechanical property calibration model: the operation objects are all 10 sacrificial test bars; for each test bar (all under a known zero stress state), the system of this invention is used for testing, and its Δt is measured. total F σ (At this time F) σ (Approaching 0); the acoustic birefringence solution engine applies the Δt established in the first stage. texture =Δt total -k•F σ The algorithm calculates the microstructure anisotropy index Δt for each test bar after stress interference has been eliminated. texture These 10 test bars were subjected to destructive impact tests according to the 3 / 00 standard to obtain their respective actual impact toughness values ​​(J); the engine collected 10 sets (Δt) texture The system takes data pairs (J) and performs regression analysis on these data points to establish the final calibration model. This model can be selected as a polynomial fit or an exponential fit, and its specific form (e.g.) and coefficients a, b, c are uniquely determined by the calibration data. By executing the above two-stage calibration procedure, the decoupling algorithm and performance calibration model inside the acoustic birefringence solution engine are given reproducible engineering entities. In subsequent in-situ testing, the system can output reliable mechanical performance indicators that exclude stress interference based on the objective model.

[0050] Example 5: This example describes a set of pre-calibration steps performed by the thick-walled precision forging mechanical property testing system of the present invention in field testing tasks, specifically for forgings with complex geometries, such as variable wall thickness nozzles, and operating under non-standard temperature conditions. This calibration eliminates measurement deviations introduced by temperature variations and geometric thickness uncertainties. Before starting large-area scanning, the operator selects a reference area on the forging with a known and low stress state, and uses a longitudinal wave probe module to measure the bottom echo flight time t of the longitudinal wave in this reference area. L Combined with the known thickness L at this point from the design drawings or other thickness measurement methods ref The longitudinal wave velocity v at the current operating temperature is calculated. L_current Its calculation follows v L_current =2L ref / t L The acoustic birefringence solution engine retrieves this v L_current The value is used to correct the internally stored acoustic elastic proportionality coefficient k and the mechanical performance calibration model J = f(Δt). texture The temperature dependence of the system is verified by performing a complete decoupled measurement in the reference region to confirm the anisotropy index Δt of the output microstructure. texture The system's field baseline is confirmed by conforming to the expected material condition of the reference area.

[0051] After baseline confirmation, the system enters a geometrically normalized scanning mode for complex curved surfaces. When the probe moves to any point on the forging surface, the longitudinal wave probe module measures the longitudinal wave flight time t at that point. L_i The acoustic birefringence solution engine utilizes calibrated v L_current The thickness L at that point is calculated in real time. i =v L_current ×t L_i / 2; Following this, the broadband shear wave probe module and the longitudinal wave probe module work together to measure and calculate the total time difference Δt at this point. total_i and residual stress interference factor F σ_i The engine performs a normalization decoupling operation B. i = (Δt) total_i -k•F σ_i） / L i , where Δt total_i F represents the total time difference at that point. σ_i L is the residual stress interference factor, k is the calibrated acoustoelastic proportionality coefficient, and L is the residual stress interference factor. i The thickness at this point yields a normalized microstructure anisotropy B, which has eliminated stress and geometric interferences. i ; The B iThe value is then input into the calibration model J = f(B), and the mechanical performance index at the test point is finally output; the probe here can be an integrated probe that integrates longitudinal wave and shear wave transducers.

[0052] Example 6: This example describes a calibration procedure for an acoustic birefringence calculation engine for testing or analyzing a second mechanical property index related to microscopic discontinuities in materials by measuring the chemical or physical properties of the materials. This procedure aims to establish a reproducible quantitative correlation between attenuation anisotropy indices and actual physical damage. The initial state is defined as follows: the test object is a set of five forging calibration specimens with uniform metallographic structure and grain size, but which have been introduced with microscopic discontinuities and microcracks of different densities or preferred orientations through pre-fabrication processes, such as incomplete annealing after cold working or fatigue loading in a specific direction. The enabling environment includes a high-resolution scanning electron microscope (SEM) and accompanying image analysis software (for quantitative statistics of microscopic damage), as well as the detection system of this invention.

[0053] The calibration procedure is as follows: Destructive metallographic analysis is performed on five calibration samples to obtain baseline values. This involves using a SEM at a specified magnification (e.g., 5000x) to photograph key sections of the samples, and then using image analysis software to statistically determine the statistical parameters (D) of the microscopic discontinuities of each sample. micro This parameter can be the number of microcracks per unit area or the sum of their projected lengths in a specific direction; secondly, before destructive analysis, the broadband shear wave probe module of the system of this invention is used to detect the same location on each sample, and the acoustic birefringence calculation engine is instructed to perform attenuation anisotropy analysis; the engine measures the first amplitude A of the fast wave echo peak from the same echo signal acquired. fast The second amplitude A of the slow wave echo peak slow And calculate a decay anisotropy index α aniso This indicator can be defined as α. aniso =20log 10 (A fast / A slow Finally, the engine collected 5 sets (α) aniso D micro Data pairs were analyzed, and α was established through regression analysis. aniso With D micro A quantitative calibration model between them enables the system to perform subsequent in-situ detection by measuring α. aniso To non-destructively evaluate the microscopic discontinuities of forgings.

[0054] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention.

[0055] Finally, 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.

Claims

1. A method for testing the mechanical properties of thick-walled precision forgings, characterized in that, The method includes the following steps: Step a: Excite shear wave pulses to the test area of ​​the forging through the broadband shear wave probe module and collect the echo signal. The echo signal contains fast wave echo peaks and slow wave echo peaks due to the acoustic anisotropy present in the forging. Step b: Measure the longitudinal wave velocity of the forging in the test area along at least two orthogonal directions using a longitudinal wave probe module; Step c involves connecting the acoustic birefringence solution engine to the broadband shear wave probe module and the longitudinal wave probe module. This is used to: calculate the absolute time difference between the fast wave echo peak and the slow wave echo peak based on the echo signal; determine the residual stress interference factor based on the longitudinal wave velocity; compensate or calibrate the absolute time difference based on the residual stress interference factor to decouple and obtain microstructure anisotropy indices; and determine the mechanical properties of the forging in the test area based on the microstructure anisotropy indices and the calibration model.

2. The method for testing the mechanical properties of thick-walled precision forgings according to claim 1, characterized in that, In step c, the calibration model is established by performing destructive mechanical tests and birefringence measurements on the sacrificial test bar used for destructive testing. The calibration model is used to correlate the destructive test data of the sacrificial test bar with the microstructure anisotropy index.

3. The method for testing the mechanical properties of thick-walled precision forgings according to claim 1, characterized in that, In step b, the longitudinal wave probe module is also used to measure the thickness of the forging in the area to be measured, and the acoustic birefringence calculation engine is also used to normalize the microstructure anisotropy index based on the thickness before determining the mechanical performance index.

4. The method for testing the mechanical properties of thick-walled precision forgings according to claim 3, characterized in that, The P-wave probe module is used to measure thickness, specifically by measuring the P-wave flight time. The acoustic birefringence calculation engine is also used to calculate the thickness L based on the P-wave flight time and the known P-wave sound velocity. The acoustic birefringence calculation engine is used to perform normalization processing, specifically by calculating the normalized anisotropy B, which follows the formula B = Δt / L, where Δt is the microstructure anisotropy index and L is the thickness calculated by the P-wave sound velocity.

5. The method for testing the mechanical properties of thick-walled precision forgings according to claim 1, characterized in that, In step c, the acoustic birefringence calculation engine is also used to: measure the first amplitude of the fast echo peak and the second amplitude of the slow echo peak from the echo signal; calculate the attenuation anisotropy index based on the relationship between the first amplitude and the second amplitude; and determine the second mechanical property index of the forging related to the micro-discontinuity in the test area based on the attenuation anisotropy index.

6. The method for testing the mechanical properties of thick-walled precision forgings according to claim 1, characterized in that, In step c, the acoustic birefringence solving engine is also used to: extract the backscattering time window signal located after the shear wave pulse and before the fast wave echo peak from the echo signal, perform a statistical analysis algorithm on the backscattering time window signal to calculate the grain size characterization parameters, and determine the grain size of the forging in the test area based on the grain size characterization parameters.

7. The method for testing the mechanical properties of thick-walled precision forgings according to claim 1, characterized in that, In step a, the broadband shear wave probe module is an electromagnetic acoustic transducer used to excite shear wave pulses under non-contact or dry coupling conditions.

8. The method for testing the mechanical properties of thick-walled precision forgings according to claim 1, characterized in that, In step c, the calibration model is used to establish a quantitative correlation between microstructure anisotropy indices and the impact toughness or fatigue resistance of the forging.

9. The method for testing the mechanical properties of thick-walled precision forgings according to claim 1, characterized in that, In step c, the acoustic birefringence calculation engine is also used to: determine the principal axis direction of residual stress in the test area of ​​the forging by analyzing the polarization information of the fast wave echo peak and the slow wave echo peak.

10. The method for testing the mechanical properties of thick-walled precision forgings according to claim 1, characterized in that, In step c, the acoustic birefringence solution engine is used to calculate the absolute time difference. Specifically, it performs signal processing on the echo signal based on a cross-correlation algorithm or a peak fitting algorithm to calculate the peak time of the fast wave echo peak and the slow wave echo peak, and calculates the difference between the peak times.

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