Residual stress detection method and residual stress detection system

Abstract

The residual stress detection method comprises the following steps: carrying out residual stress scanning on the surface of a to-be-detected component by using an ultrasonic stress detection method so as to determine one or more high residual stress areas on the surface of the to-be-detected component; and performing residual stress gradient detection on the one or more high residual stress areas by using an eddy current stress detection method to determine the residual stress gradient of the one or more high residual stress areas. The invention further discloses a residual stress detection system comprising the ultrasonic eddy current integrated probe. The embodiment of the invention can improve the detection efficiency and the detection precision.

Description

Technical Field

[0001] This application belongs to the field of nondestructive testing, and particularly relates to a residual stress detection method and a residual stress detection system. Background Art

[0002] Many components of aeroengines have strict requirements for fatigue life. These components usually introduce residual stress through surface strengthening to improve the fatigue life of parts. The numerical value and distribution of residual stress have a great impact on the fatigue life of parts. Therefore, obtaining information on the residual stress on the surface of parts is of great significance for predicting the life of engine parts.

[0003] Currently, the commonly used residual stress detection methods are divided into destructive testing and nondestructive testing. The former requires drilling holes in the component to be tested, which is unacceptable for expensive engine components. The commonly used method for the latter is X-ray diffraction method. However, the penetration ability of X-rays for nickel-based alloys is limited, and it can only measure the depth of about 5μm, unable to fully evaluate the distribution of residual stress on the surface layer of the component. Moreover, some nondestructive testing schemes can only measure the average value of residual stress within a certain depth range and cannot measure the gradient distribution of residual stress.

[0004] Furthermore, the spot size of X-ray irradiation is about 1mm, which cannot meet the detection efficiency required for large-area scanning.

[0005] Therefore, a solution is needed to improve the residual stress detection of components. Summary of the Invention

[0006] One or more embodiments of this specification achieve the above object through the following technical solutions.

[0007] In one aspect, a residual stress detection method is provided, including:

[0008] Using an ultrasonic stress detection method to perform a residual stress scan on the surface of the component to be tested to determine one or more high residual stress regions on the surface of the component to be tested; and

[0009] Using an eddy current stress detection method to perform a residual stress gradient detection on the one or more high residual stress regions to determine the residual stress gradient of the one or more high residual stress regions.

[0010] In one embodiment, performing residual stress scanning includes: performing step scanning on the surface of the component to be inspected in a first direction with a first step length to obtain the acoustic time difference at multiple points in the first direction, and obtaining a residual stress distribution cloud map in the first direction based on the acoustic time difference at the multiple points; performing step scanning on the surface of the component to be inspected in a second direction perpendicular to the first direction with a second step length to obtain the acoustic time difference in the second direction, and obtaining a residual stress distribution cloud map in the second direction based on the acoustic time difference in the second direction; and determining the one or more high residual stress areas based on the residual stress distribution cloud maps in the first direction and the second direction.

[0011] In one embodiment, the method includes: loading the tensile specimen corresponding to the component to be tested step by step, measuring a plurality of different stress levels S i The acoustic time t of LCR wave propagation for a certain distance i , and with zero stress sound time t 0 The acoustic time difference Δt under the corresponding stress level is obtained by subtraction. i Based on the multiple different stress levels S i The acoustic time difference Δt i To establish a functional relationship between the acoustic time difference and the stress level; and using the functional relationship, based on the acoustic time difference at a point on the surface of the component to be tested, obtain the residual stress at the point, so as to obtain a residual stress distribution cloud diagram.

[0012] In one embodiment, the residual stress gradient detection includes: using an eddy current probe to measure and calibrate a first standard test block and a second standard test block, so as to establish calibration vectors α and β in an impedance plane according to the measurement results, wherein the conductivity of the first standard test block is σ 1 The conductivity of the second standard test block is σ 2 , where σ 1 ≤σ≤σ 2 ; Perform frequency sweep detection on the component to be tested at a frequency of 0.1-100MHz to obtain the frequency f n The measured coordinate point (x n ,y n ), and take the calibration vectors α and β as the basis to convert (x n ,y n ) is converted to (α n ,β n ) coordinates, and then according to σ 1 , σ 2 The relationship between α and β is used to obtain the frequency f n The conductivity σ(f n ); σ(f n ) is converted to conductivity and d n The relationship between Γ(dn ), where d n is the depth that the lower eddy current can reach, d n the conductivity Γ at the depth position n =(Γ(d dn )v n -Γ(d n )v n-1 ) / (v n-1 -v n ), where v n-1 is f n the distribution volume of the lower eddy current, that is, the distribution volume when the eddy current reaches d n depth, d n =d n +Δd, Δd is the thickness of the superalloy material layer that can be regarded as the equalization of residual stress, v n-1 is the distribution volume when the eddy current reaches d n-1 depth; providing the corresponding relationship τ(Γ) between the conductivity and elastic stress of the superalloy, and obtaining the residual stress value τ(Γ n-1 ) at each depth value d n to obtain the gradient distribution of residual stress. dn )

[0013] In one embodiment, the method further includes:

[0014] the step of setting non-conductive calibration gaskets on the surfaces of the first standard test block and the second standard test block, and the calibration vectors α and β are established according to the four measurement points obtained by directly contacting and measuring the first standard test block, the second standard test block with the eddy current probe and measuring the first standard test block, the second standard test block with the non-conductive calibration gasket as a barrier.

[0015] In one embodiment, the ultrasonic stress detection method and the eddy current stress detection method are performed using the same integrated probe, and the integrated probe includes a wedge block, and the bottom of the wedge block includes an eddy current planar detector located in the center and two ultrasonic transducers located on both sides of the eddy current planar detector.

[0016] In one embodiment, the method further includes: constructing a subsurface three-dimensional residual stress field map of the entire component to be detected based on the residual stress distribution contour maps in the first direction and the second direction and the residual stress gradient in the one or more high residual stress regions.

[0017] In one embodiment, the method further includes: regularly obtaining the subsurface three-dimensional residual stress field map of the entire component to be detected to construct a three-dimensional residual stress field evolution map evolving with time.

[0018] On the other hand, a residual stress detection system is also disclosed, including an ultrasonic eddy current integrated probe. The ultrasonic eddy current integrated probe includes an eddy current probe located at the center of the bottom, and two ultrasonic transducers located on both sides of the eddy current probe. The two ultrasonic transducers are used to perform the ultrasonic stress detection method as described in the embodiments of this specification, and the eddy current probe is used to perform the eddy current stress detection method as described in the embodiments of this specification.

[0019] In one embodiment, the ultrasonic eddy current integrated probe is in the form of a wedge block, and the wedge block is modified to adapt to the shape of the surface of the component to be detected.

[0020] One or more embodiments of this specification can achieve at least one of the following technical effects:

[0021] It can perform non-destructive testing;

[0022] By combining ultrasonic and eddy current testing, high detection accuracy in high stress areas can be achieved while performing large area scanning.

[0023] Through ultrasonic testing, the detection efficiency is improved, and through eddy current testing, the detection accuracy is improved.

[0024] Through eddy current testing, three-dimensional detection of residual stress can be achieved.

[0025] Through four-point calibration, the detection error caused by the lift-off of the eddy current probe can be eliminated, and the detection accuracy can be improved.

[0026] Through the ultrasonic eddy current integrated probe, there is no need to replace the probe in the two detection modes, and the consistency of detection parameters can be maintained, improving the detection efficiency and detection accuracy;

[0027] The detection accuracy can be improved through probe shaping. Description of the Drawings

[0028] The above invention content and the following specific implementation manners will be better understood when read in conjunction with the drawings. It should be noted that the drawings are only examples of the claimed invention. In the drawings, the same reference numerals represent the same or similar elements.

[0029] Figure 1 A schematic diagram showing a system for detecting residual stress according to an embodiment of this specification.

[0030] Figure 2 A front view and a top view showing a probe for detecting residual stress according to an embodiment of this specification.

[0031] Figure 3 A schematic diagram showing a general method for detecting residual stress according to an embodiment of this specification.

[0032] Figure 4 Schematic diagram showing a standard test block according to an embodiment of the present specification.

[0033] Figure 5 Schematic diagram showing the electro-elastic calibration in the impedance plane according to an embodiment of the present specification.

[0034] Figure 6 Schematic diagram showing a tensile test piece and a probe calibration area according to an embodiment of the present specification.

[0035] Figure 7 Schematic diagram showing the correlation between acoustic time difference, conductivity and applied stress according to an embodiment of the present specification.

[0036] Figure 8 Schematic diagram showing the process of step-by-step scanning for performing ultrasonic residual stress scanning according to an embodiment of the present specification. Detailed implementation manners

[0037] The content of the following detailed implementation manners is sufficient for any person skilled in the art to understand the technical content of one or more embodiments of the present specification and implement them accordingly. According to the specification, claims and drawings disclosed in the present specification, a person skilled in the art can easily understand the objectives and advantages related to one or more embodiments of the present specification.

[0038] It should be understood that the description of the embodiments is merely illustrative and not any limitation to the present disclosure and its application or use. In the present disclosure, means, components or operations known to those of ordinary skill in the relevant art may not be described, but when appropriate, the description of the corresponding means, components or operations should be regarded as being included in the present disclosure.

[0039] Unless otherwise clearly stated, the relative arrangement of components, the relative order of operations, the composition of materials, numerical expressions and values set forth in these embodiments should be construed as merely exemplary and not as limitations. Unless otherwise clearly stated, words such as "first", "second", etc. used in the present disclosure do not imply any order or importance, but are only used to distinguish different parts.

[0040] In the present disclosure, "upper", "lower", "left", "right", "front", "rear", etc. are only used to represent relative position relationships. When the absolute position of the object being described changes, the relative position relationship may also change accordingly.

[0041] In the present disclosure, when it is described that a specific component is above, below or in a similar relationship to a first component, it does not imply that the specific component is directly above, directly below, etc. the first component, and it does not exclude the possibility of there being intermediate components between the specific component and the first component.

[0042] In the present disclosure, when it is described that a specific component is located between a first component and a second component, it does not exclude the possibility that there is an intermediate component between the specific component and the first component.

[0043] In the present disclosure, when it is described that a specific component is connected or coupled to other components, it does not mean that the specific component or other components are directly connected or coupled, and it does not exclude the possibility that there is an intermediate component between the specific component and the first component.

[0044] Unless otherwise defined in the present disclosure, all terms used in the present disclosure shall be interpreted in accordance with the meanings understood by those of ordinary skill in the art to which the present disclosure pertains.

[0045] In the present disclosure, a civil aircraft is taken as an example of an aircraft. However, it should be understood that the aircraft in this specification is not limited to civil aircraft. On the contrary, the aircraft in this specification may include various flying vehicles for various purposes, including manned aircraft and unmanned aircraft, including military aircraft and civil aircraft, including airplanes and other forms of aircraft, and so on.

[0046] Accordingly, in the present disclosure, an aeroengine refers to an engine used to provide power for an aircraft. Unless otherwise specified, the engine is not limited to a specific type of engine.

[0047] See Figure 1 , which shows a schematic diagram of a system 100 for detecting residual stress according to an embodiment of this specification.

[0048] As Figure 1 shown, and referring to Figure 2 , the system 100 may include a probe 102. In the embodiment of this specification, the probe 102 is an ultrasonic eddy current integrated probe. The probe 102 can perform ultrasonic stress detection (for example, the ultrasonic stress detection described in the embodiment of this specification), and can also perform eddy current stress detection (for example, the eddy current stress detection described in the embodiment of this specification). Therefore, the ultrasonic eddy current integrated probe 102 is particularly suitable for implementing the embodiments of this specification. Integrating the ultrasonic stress detection function and the eddy current stress detection function on a single probe can eliminate the need to replace the probe when performing the two detection methods, thereby improving the operation efficiency. More importantly, since the ultrasonic stress detection and the eddy current stress detection can be performed at exactly the same position and with exactly the same parameters (for example, the degree of fit between the probe and the surface of the component to be detected is exactly the same, the temperature is the same, and other environmental parameters are also the same), the accuracy of the detection is improved.

[0049] However, it should be understood that the system 100 can also perform other residual stress detection methods.

[0050] In addition to the probe 102, the system 100 may include other components, such as components for ultrasonic stress detection and components for eddy current detection respectively, as well as components for performing functions such as data analysis processing, signal generation and transmission.

[0051] As Figure 1 shown, the system 100 may include a function generator 104 for generating the required frequencies and waveforms, an ultrasonic signal amplifier 106 for amplifying ultrasonic signals, an oscilloscope 108 for displaying ultrasonic waveforms for analysis, an impedance analyzer 110 for performing impedance analysis required for eddy current stress detection, and a computer 112 for controlling the operation of each component and performing analysis on each data, etc. In particular, hereinafter, the operations of the embodiments of this specification may be implemented by the computer 112. The computer 112 may be various forms of computing devices. The system 100 may further include other required components (not shown).

[0052] Preferably, after all the devices of the system 100 are connected, each device may be turned on for a period of time (for example, one hour) for preheating to enable each device to reach thermal stable equilibrium, so as to improve the measurement accuracy.

[0053] See Figure 2 , which shows the front view and top view of the probe 102 for detecting residual stress according to the embodiments of this specification.

[0054] In one example, the probe 102 is in the form of a wedge block. A wedge block as shown in the front view above, or other styles of wedge blocks, may be adopted. In addition to the wedge block, the ultrasonic-eddy current integrated probe may also adopt other shapes. Figure 2

[0055] In one example, the main body of the probe is made of a resin material, but any other suitable material suitable for the probe may also be adopted.

[0056] In one example, the probe is shaped to fit the shape of the surface of the component to be detected. For example, considering the skin effect of ultrasonic and eddy current high-frequency signals, the probe shape can be adapted to the surface shape. By shaping, the surface of the probe can be made to fit the surface of the component to be detected more closely, thereby improving the measurement accuracy.

[0057] As Figure 2 shown in the front view above and the top view below, and referring to Figure 1 ​, the probe 102 includes an eddy current probe 202 located at the center of the bottom, and two ultrasonic transducers 204 and 206 located on both sides of the eddy current probe. Preferably, the eddy current probe 202 is a high-frequency eddy current probe, and its frequency range is preferably 0.1 - 80 MHz, but is not limited thereto. The two ultrasonic transducers 204 and 206 can be used as a transmitting transducer for longitudinal wave incidence and a receiving transducer for longitudinal wave reception, respectively.

[0058] As Figure 2 shown in the top view below, in the middle of the two ultrasonic transducers 204 and 206, and as part of the eddy current probe 202, is the eddy current detection area 208. The two ultrasonic transducers serve as the ultrasonic signal transmitting area 210 and the receiving area 212, respectively.

[0059] As Figure 2 shown in the front view above, due to the characteristics of the ultrasonic stress detection method itself, it can only detect a relatively small thickness, as Figure 2 shown by the ultrasonic detection thickness 214.

[0060] Refer to Figure 3 , which shows a schematic diagram of a general method 300 for detecting residual stress according to an embodiment of this specification. It should be understood that this method is to explain various aspects that may be involved in the embodiments of this specification as a whole, so as to understand the context of the embodiments of this specification as a whole, and one or more of its operations are not necessary in all embodiments.

[0061] As Figure 3 shown, the method 300 may include: in operation 302, performing an elastic limit measurement on the test piece. Through the elastic limit measurement experiment, the loading range of the acoustoelastic calibration test can be determined.

[0062] Specifically, under room temperature conditions, a mechanical testing machine can be used to uniformly load the processed tensile test piece, measure the force-displacement curve of the material, determine the proportional limit of the material, and then determine the elastic stress range with better linearity as the loading range of the acoustoelastic calibration test.

[0063] It should be understood that other known methods for determining the elastic stress range in the art can be used to determine the range as this loading range. In addition, in many cases, the previously prepared test pieces and the elastic stress range set by the implementer or a third party can be directly used. Therefore, this operation is not necessary. Alternatively, this operation can be completely omitted.

[0064] The method 300 may include: in operation 304, performing zero stress calibration.

[0065] A test block can be selected and pre-treated. Generally, the selected test block can be made of a material having the same microstructure as the component to be detected.

[0066] In one example, stress annealing treatment can be performed on the test block. This annealing can be carried out, for example but not limited to, in reference to the standard GH / T 16923. Through the annealing treatment, it can be ensured that the metallographic structure of the test block is basically the same as the material structure state of the component.

[0067] In one example, aging stress relief treatment can be performed on the test block. This treatment can be carried out, for example but not limited to, in reference to the standard GH / T 25712. Through the stress relief treatment, the stress of the test block can be approximated to zero.

[0068] After performing (or not performing in some cases) the above-mentioned treatment on the test block, an ultrasonic probe (or the ultrasonic stress detection function of the ultrasonic eddy current integrated probe as in the embodiments of this specification) can be used to detect the test block, so as to obtain the acoustic time t under the zero-stress state. 0 ; This acoustic time t 0 Can be used as a reference during subsequent ultrasonic detection.

[0069] In addition, an eddy current probe (or the eddy current stress detection function of the ultrasonic eddy current integrated probe as in the embodiments of this specification) can be used to detect the test block, so as to obtain the conductivity value σ under the zero-stress state. 0 This conductivity value σ 0 Can be used as a reference during subsequent eddy current detection.

[0070] Other conceivable methods other than those described above can be used to achieve zero-stress calibration.

[0071] Method 300 may include: at operation 306, electroelastic calibration can be performed. In the embodiments of this specification, an electroelastic calibration method is proposed, and the process of this method is as follows:

[0072] Standard test blocks can be prepared. Generally, this standard test block can use a material having the same microstructure as the component to be detected, and then this material can be cut into a plurality of test blocks with specified sizes. For example, several cube test blocks can be obtained by wire cutting. The specified size is, for example but not limited to, 30mm * 30mm * 20mm. The test block can be polished to a roughness R a <1μm.

[0073] Vacuum solution treatment can be performed on the test block. Subsequently, vacuum aging heat treatment can be performed on different test blocks under different aging conditions. For example, according to the first aging temperature T °C of the standard heat treatment process for the material preparation, vacuum aging heat treatment with a temperature of T ± 50m (m is an integer and m ≥ 5) and a time of t ± 2^n (m is an integer and m ≥ 5) can be performed on each solution-treated test block. One test block is treated with each aging condition (m, n). In this way, a total of 4mn test blocks with gradually changing conductivity can be finally obtained.

[0074] Subsequently, a first standard test block and a second standard test block are selected. Preferably, the two selected standard test blocks are respectively test blocks with electrical conductivities greater than and lower than that of the component to be measured.

[0075] See Figure 4 , which shows a schematic diagram of a standard test block according to an embodiment of the present specification.

[0076] For example, assume that the deep electrical conductivity of the material of the component to be measured, i.e., the electrical conductivity in the natural stress-free state, is σ. Before the detection, first provide a first standard test block 402 with an electrical conductivity of σ 1 and a second standard test block 404 with an electrical conductivity of σ 2 , such that σ 1 ≤σ≤σ 2 . In a preferred embodiment, σ, σ 1 , σ 2 satisfy: σ - 0.2 ≤ σ 1 ≤ σ - 0.1, σ + 0.1 ≤ σ 2 ≤ σ + 0.2, where the values of the electrical conductivity are all in IACS%. In different embodiments, according to the different alloy components to be measured, the value of σ can be measured and obtained by using a commercial electrical conductivity probe at a frequency of 480 kHz on a 0-stress standard test block specially made of the superalloy.

[0077] Next, measurement calibration is performed. The eddy current probe (for example, the eddy current probe 202 described above, or other suitable eddy current probes) is respectively abutted against the surfaces of the first standard test block 402 and the second standard test block 404 for measurement.

[0078] Reference can be made to Figure 5 , which shows a schematic diagram of four-point calibration in the impedance plane according to an embodiment of the present specification. As shown in the figure, by measuring on the surfaces of the first standard test block 402 and the second standard test block 404, measurement points a(x 1 , y 1 ), b(x 2 , y 2 ) in the impedance plane are obtained. In some preferred embodiments, in addition to direct measurement, a non-conductive calibration gasket 406 with a thickness of s is provided on the surfaces of the first standard test block 402 and the second standard test block 404, and measurement is performed again with the non-conductive calibration gasket 406 as a barrier, and measurement points c(x 3 , y 3 ), d(x 4 , y 4)。The non-conductive calibration gasket 406 is set to calibrate the situation where the eddy current probe cannot closely adhere to the surface of the component to be detected. The non-conductive calibration gasket 406 simulates the situation where there is an air barrier between the eddy current probe and the component to be detected. In some embodiments, the thickness s of the non-conductive calibration gasket 406 is set to 20 μm - 100 μm, and 30 μm is usually selected. The calibration vectors α and β in the impedance plane are constructed using four points a, b, c, and d. For example, α and β can be the connection directions of any two groups of points among the four points a, b, c, and d that do not form a parallel relationship. For accurate calculation and measurement, the included angle between α and β should be close to 90°. In some embodiments, if the non-conductive calibration gasket 406 is not set, the c and d coordinates are both recorded as (0, 0).

[0079] It can be envisioned that if there is no residual stress in the component to be detected and the gap between the component to be detected and the probe is between 0 and s, assuming that the point on the component to be detected has a measured result at frequency f n as the coordinate point (x n ,y n ) in the impedance plane, then this point falls within the region enclosed by the four points a, b, c, and d. Through basic linear algebra calculations, (x n ,y n ) can be converted into the coordinates (α n ,β n ) based on the calibration vectors α and β. In the process of constructing the calibration vectors α and β, the relationships between σ 1 , σ 2 and α, β are also established, that is, the conductivity corresponding to each coordinate point in the impedance plane can be obtained. After converting (x n ,y n ) into (α n ,β n ), the conductivity σ(f n ) corresponding to the data measured by the probe at frequency f n =K a α n +K b β n +K c can also be solved, where K a , K b , K c are constants.

[0080] For example, in an embodiment where the non-conductive calibration gasket 406 is not set, let α=(x 1 ,y 1 ), β=(x 2 ,y 2 ), and the coordinates of the measurement point x(x n ,y n ) after conversion are (αn , β n ), that is, the vector from the origin to x(x n , y n ) is x = α n α + β n β, and it is known that α corresponds to σ 1 , and β corresponds to σ 2 , so σ(f n ) = α n σ 1 + β n σ 2 .

[0081] The eddy current probe can be fixed in the central area of the tensile test piece, that is, the probe calibration area 602 (as Figure 6 shown), and the tensile test piece is subjected to uniform quasi-static loading within the elastic range (for example, the elastic range determined above) using a mechanical testing machine, as Figure 6 shown by the arrow. At the same time, the conductivity values at different stress levels S i (for example, i≥10 different stress levels can be taken to establish the relationship between conductivity and stress) are recorded. Repeated tensile tests can be carried out, and the conductivity σ i,j corresponding to different impedances is measured each time (where j is the number of measurements). Repeated measurements can be taken (for example, the number of measurements j≥5) and the average value of the measured conductivity σ i,j is obtained in order to plot a coordinate graph of the tensile stress value and the conductivity, as Figure 7 shown, to obtain the linear relationship between the conductivity (σ) and the elastic stress (τ): During the plotting process, the conductivity value σ 0 in the zero-stress state can be used.

[0082] However, it should be understood that the above embodiments are only preferred examples of electroelastic calibration. The embodiments of this specification are not limited to the electroelastic calibration method as described above, but other electroelastic calibration methods known or conceivable to those skilled in the art can be used.

[0083] Method 300 may include: at operation 308, acoustic elastic calibration can be performed.

[0084] Specifically, the process is as follows:

[0085] The tensile specimen corresponding to the component to be detected can be loaded step by step. At this time, the acoustic time t i for the LCR wave to propagate a fixed length at multiple different stress levels S i can be measured, and the difference is taken with the zero-stress acoustic time t 0 to obtain the acoustic time difference Δt i at the corresponding stress level.

[0086] Based on the multiple different stress levels S i of the acoustic time difference Δt i to establish a functional relationship between the acoustic time difference and the stress level. For example, this functional relationship can be a linear relationship. For example, such as Figure 7 shown.

[0087] After determining this functional relationship, this functional relationship can be used to obtain the residual stress at a point on the surface of the component to be detected based on the acoustic time difference at the point, as will be described later.

[0088] It should be understood that although various preparation steps and calibration steps are described above, these steps are not necessary. In some embodiments, only one calibration is required, and the calibration does not need to be performed again during subsequent detection processes. In some embodiments, calibration data (such as a functional relationship) provided by a third party can be used, so that the above preparation and calibration processes can be omitted.

[0089] Method 300 may include, in operation 310, using an ultrasonic stress detection method to perform a residual stress scan on the surface of the component to be detected to determine one or more high residual stress regions on the surface of the component to be detected. Preferably, this ultrasonic stress detection method can be performed using the residual stress detection system 100 described in the embodiments of the present specification.

[0090] For example, refer to Figure 8 , which shows a schematic diagram of a step scan process for performing an ultrasonic residual stress scan according to an embodiment of the present specification.

[0091] First, a step scan can be performed on the surface of the component to be detected in a first direction (such as the X direction in Figure 8 ) with a first step size to obtain the acoustic time differences at multiple points in the first direction. For example, by using the functional relationship obtained in operation 308 above, the residual stresses at multiple points in this first direction can be obtained. For example, by combining the residual stresses at multiple points during the step scan, a residual stress distribution contour map can be obtained.

[0092] Similarly, a step scan can be performed on the surface of the component to be detected in a second direction perpendicular to the first direction (such as the Y direction in Figure 8 ) with a second step size to obtain the acoustic time differences in the second direction, and a residual stress distribution contour map in the second direction can be obtained based on the acoustic time differences in the second direction.

[0093] Taking a flat component as an example, as Figure 7 shown, the length and width of the probe are L and W respectively. A C-scan is performed on the entire surface. First, the X direction is used as the step direction, and the step sizes in the X and Y directions respectively satisfy S X ≤L / 2, SY ≤W / 2. By reducing the step size, the surface resolution of the detection can be improved. Taking Figure 8 the entire area is scanned in the manner shown, and the acoustic time difference Δt in the X direction can be obtained X , and then, through the formula τ x =Δt X ×K 2 the calculation can obtain the distribution cloud map of the residual stress τ in the X direction x .

[0094] Subsequently, the probe can be rotated 90 degrees and the entire surface can be scanned with the Y direction as the step direction, and the distribution cloud map of the residual stress τ in the Y direction can be obtained similarly Y .

[0095] Based on the distribution cloud maps of the residual stress in the first direction and the second direction, one or more high residual stress regions (such as Figure 8 regions A and B in

[0096] can be determined. Method 300 may include, in operation 312, using an eddy current stress detection method to perform a residual stress gradient detection on one or more high residual stress regions to determine the residual stress gradient of the one or more high residual stress regions. Preferably, the eddy current stress detection method can be performed using the residual stress detection system 100 described in the embodiments of the present specification.

[0097] The process of the residual stress gradient detection is as follows:

[0098] The probe is moved to the high residual stress regions (such as Figure 7 regions A and B in n ), and the component to be detected is scanned within a specified frequency range (such as a frequency range of 0.1 MHz - 100 MHz) to obtain a series of frequency-conductivity data sets {f n , σ(f

[0099] Next, the conductivity at a specific depth is obtained through inverse calculation. Since the eddy current has a certain distribution volume v inside the component to be detected at the frequency f n , the corresponding conductivity σ(f n ) is the average value of the conductivity within v n . Let the depth that the eddy current can reach at the frequency f n be d n , then the relationship between the frequency and the conductivity σ(f n ) can be further converted into the relationship between the depth and the conductivity Γ(d n ), and the frequency-conductivity data set {f n , σ(f n , σ(f n)} can be converted into a depth-conductivity data set {d n , Γ(d n )}. Suppose the residual stress value within the thickness range of Δd can be approximately regarded as the same, then the conductivity Γ n at d dn can be calculated by Γ dn = (Γ(d n )v n - Γ(d n-1 )v n-1 ) / (v n - v n-1 ), where d n = d n-1 + Δd. Since d n and f n are in one-to-one correspondence, so d n and v n are also in one-to-one correspondence. For the corresponding d n-1 , there is also a corresponding distribution volume v n-1 . This process is equivalent to performing a differential calculation at d n , thereby converting the depth-conductivity data set {d n , Γ(d n )} into a conductivity gradient data set {d n , Γ dn}. In some embodiments, the range of Δd is 5 μm - 200 μm. In the region near the surface layer, the value of Δd is smaller, for example, it can be taken as 10 μm. In the deep layer region, the value of Δd is larger, for example, it can be taken as 200 μm. The value of Δd actually determines the measurement resolution. For the workpieces undergoing surface strengthening processing, the residual stress gradient in the surface layer is larger, and the residual stress gradient in the deep layer is relatively smaller. In some embodiments, the distribution volume v n of the eddy current at different frequencies f n can be retrieved from a pre-established database, or can be obtained by computer simulation calculation, by establishing an eddy current model and integrating the eddy current isodensity curve.

[0100] Finally, according to the corresponding relationship τ(Γ) between the conductivity of the material of the component to be detected and the elastic stress measured, the elastic stress value corresponding to each depth d n is obtained, and an elastic stress gradient data set {d n , τ(Γ dn )} is obtained. Through this data set, the elastic stress value at any depth within the measurement range can be obtained. Among them, τ(Γ) can be obtained by referring to the material property manual, or can be calibrated by a specially conducted tensile test for the relationship between conductivity and elastic stress. The two can be, for example, in a linear relationship, τ(Γ dn ) = K 1 (Γ dn - Γ0 ), where K 1 is a calibration constant. This calibration constant K 1 can be obtained as described above in operation 306, or can be obtained by other means; Γ 0 is the conductivity at zero stress obtained by measuring a zero-stress specimen.

[0101] By measuring at each depth in the high-stress region, the residual stress gradient in the high-stress region can be determined.

[0102] The above calculation and storage processes can all be automatically completed by a computer (e.g., Figure 1 the computer 112 shown) of the residual stress detection system through a built-in program. In some embodiments, it can also be manually analyzed and calculated in the same way using general data processing software for the data collected by the eddy current probe.

[0103] In the embodiments of this specification, by combining ultrasonic scanning detection of the surface (utilizing the characteristics of large ultrasonic scanning range, high surface scanning efficiency, but small detection depth) and eddy current detection of the high-stress region (utilizing the characteristics of deeper eddy current scanning detection depth and higher detection resolution), the three-dimensional residual stress of the entire component can be efficiently determined, thereby quickly, accurately, and three-dimensionally locating the high residual stress region.

[0104] In a preferred embodiment, the component to be detected is made of a nickel-based superalloy, such as a nickel-based single crystal alloy, etc. Nickel-based superalloys for aviation do not have ferromagnetism and will not interfere with the eddy current detection process. In other embodiments, it can also be used to detect the residual stress of other superalloy parts such as titanium alloys.

[0105] Method 300 may further include: in operation 314, a subsurface three-dimensional residual stress field map of the entire component to be detected can be constructed based on the residual stress distribution contour maps in the first and second directions and the residual stress gradients of one or more high residual stress regions.

[0106] For example, post-processing software (including but not limited to Excel, Tecplot, etc.) can be used to construct a subsurface three-dimensional residual stress field map of the entire component using the residual stress distribution contour maps and residual stress gradients obtained from surface scanning and gradient scanning.

[0107] Method 300 may further include: in operation 316, the subsurface three-dimensional residual stress field map of the entire component to be detected can be obtained regularly to construct an evolving three-dimensional residual stress field map over time. Through the evolving three-dimensional residual stress field map, the change in residual stress of each part of the component over time can be seen, so that the health condition of each part of the component can be judged more accurately, and further the remaining life of each part of the component can be predicted.

[0108] It should be appreciated that one or more operations in the above method may be omitted, and the order of one or more operations may be changed, or one or more operations may be performed in parallel.

[0109] It should be understood that the various embodiments in this specification are described in a progressive manner. For the same or similar parts between the various embodiments, reference can be made to each other, and the key point of each embodiment is to illustrate the differences from other embodiments. In particular, for the device and system embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and for the relevant parts, reference can be made to the description of the method embodiments.

[0110] It should be understood that the specific embodiments of this specification have been described above. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recited in the claims may be performed in a different order than in the embodiments and still achieve the desired result. Additionally, the processes depicted in the figures do not necessarily require the particular order or sequential order shown to achieve the desired result. In certain embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0111] It should be understood that an element described herein in the singular form or shown as only one in the figures does not represent limiting the quantity of that element to one. In addition, modules or elements described or shown herein as separate may be combined into a single module or element, and a module or element described or shown herein as a single one may be split into multiple modules or elements.

[0112] In this specification, unless otherwise defined, "nearly", "almost", "substantially" (as used) means a deviation of no more than 10%; preferably, a deviation of no more than 5%; more preferably, a deviation of no more than 1%.

[0113] It should also be understood that the terms and expressions used herein are only for description, and one or more embodiments of this specification should not be limited to these terms and expressions. Using these terms and expressions does not mean excluding any equivalent features of the illustration and description (or parts thereof), and it should be recognized that various modifications that may exist should also be included within the scope of the claims. Other modifications, variations, and substitutions may also exist. Accordingly, the claims should be regarded as covering all such equivalents.

[0114] Similarly, it should be noted that although described with reference to current specific embodiments, those of ordinary skill in the art in this technical field should recognize that the above embodiments are only used to illustrate one or more embodiments of this specification, and various equivalent changes or substitutions can be made without departing from the spirit of the present invention. Therefore, as long as the changes and modifications of the above embodiments are within the scope of the spirit of the present invention, they will fall within the scope of the claims of this application.

Claims

1. A method for detecting residual stress, characterized in that, comprising: using an ultrasonic stress detection method to perform a residual stress scan on the surface of a component to be detected to determine one or more high residual stress regions on the surface of the component to be detected; and using an eddy current stress detection method to perform a residual stress gradient detection on the one or more high residual stress regions to determine the residual stress gradient of the one or more high residual stress regions.

2. The method according to claim 1, characterized in that, performing the residual stress scan includes: performing a step-by-step scan on the surface of the component to be detected at a first step size in a first direction to obtain the acoustic time differences at multiple points in the first direction, and obtaining a residual stress distribution contour map in the first direction based on the acoustic time differences at the multiple points; performing a step-by-step scan on the surface of the component to be detected at a second step size in a second direction perpendicular to the first direction to obtain the acoustic time differences in the second direction, and obtaining a residual stress distribution contour map in the second direction based on the acoustic time differences in the second direction; and determining the one or more high residual stress regions based on the residual stress distribution contour maps in the first direction and the second direction.

3. The method according to claim 2, characterized in that, comprising: Gradually load the tensile specimen corresponding to the component to be detected, and measure multiple different stress levels S i The acoustic time t for the LCR wave to propagate a fixed length at the following i , and subtract the acoustic time t 0 at zero stress to obtain the acoustic time difference Δt at the corresponding stress level i ; Based on the multiple different stress levels S i the acoustic time difference Δt i to establish the functional relationship between the acoustic time difference and the stress level; and using the functional relationship to obtain the residual stress at a point on the surface of the component to be detected based on the acoustic time difference at the point, so as to obtain a residual stress distribution contour map.

4. The method according to claim 1, characterized in that, performing the residual stress gradient detection includes: Use an eddy current probe to measure and calibrate the first standard specimen and the second standard specimen, so as to establish calibration vectors α and β in the impedance plane according to the measurement results, where the conductivity of the first standard specimen is σ 1 and the conductivity of the second standard specimen is σ 2 , where σ 1 ≤σ≤σ 2 ; The component to be detected is subjected to frequency sweep detection at a frequency of 0.1 - 100 MHz to obtain a frequency f n The measured coordinate point (x n , y n ) in the lower impedance plane. Based on the calibration vectors α and β, (x n , y n ) is converted to (α n , β n ) coordinates. Then, according to the relationship between σ 1 , σ 2 and α, β, the conductivity σ(f n ) corresponding to the detection value of the eddy current probe at frequency f n ) is obtained; Convert σ(f n ) to the relationship Γ(d n ) between conductivity and d n , where d n is the depth that eddy currents can reach at frequency f n , and the conductivity Γ n at depth position d dn = (Γ(d n )v n - Γ(d n-1 )v n-1 ) / (v n - v n-1 ), where v n is the distribution volume of eddy currents at f n , that is, the distribution volume when eddy currents reach depth d n , d n = d n-1 + Δd, Δd is the thickness of the superalloy material layer that can be regarded as having uniform residual stress, and v n-1 is the distribution volume when eddy currents reach depth d n-1 ; Provide the corresponding relationship τ(Γ) between the electrical conductivity and the elastic stress of the superalloy, and obtain the residual stress value τ(Γ n at each depth value d dn ), so as to obtain the gradient distribution of the residual stress.

5. The method according to claim 4, characterized in that, further comprising: a step of setting non-conductive calibration gaskets on the surfaces of the first standard test block and the second standard test block, and the calibration vectors α and β are established according to four measurement points obtained by directly contacting and measuring the first standard test block and the second standard test block with the eddy current probe respectively and measuring the first standard test block and the second standard test block with the non-conductive calibration gasket as a barrier.

6. The method according to claim 1, characterized in that, the ultrasonic stress detection method and the eddy current stress detection method are performed using the same integrated probe, and the integrated probe includes a wedge block, and the bottom of the wedge block includes an eddy current planar detector at the center and two ultrasonic transducers on both sides of the eddy current planar detector.

7. The method according to claim 2, characterized in that, further comprising: constructing a subsurface three-dimensional residual stress field map of the entire component to be detected based on the residual stress distribution contour maps in the first direction and the second direction and the residual stress gradient of the one or more high residual stress regions.

8. The method according to claim 7, characterized in that, further comprising: regularly obtaining the subsurface three-dimensional residual stress field map of the entire component to be detected to construct a three-dimensional residual stress field evolution map evolving with time.

9. A residual stress detection system, characterized in that, Comprising an ultrasonic eddy current integrated probe, the ultrasonic eddy current integrated probe includes an eddy current probe located at the center of the bottom, and two ultrasonic transducers located on both sides of the eddy current probe. The two ultrasonic transducers are used to perform the ultrasonic stress detection method according to any one of claims 1-8, and the eddy current probe is used to perform the eddy current stress detection method according to any one of claims 1-8.

10. The residual stress detection system according to claim 9, characterized in that the ultrasonic eddy current integrated probe is in the form of a wedge block, and the wedge block is modified to adapt to the shape of the surface of the component to be detected.

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