Method and apparatus for ultrasonic characterization of metal fatigue damage

Abstract

The application discloses a metal fatigue damage ultrasonic characterization method and device, a plurality of metal fatigue samples with different cycle times are processed, ultrasonic detection technology is used to sequentially obtain detection signal amplitudes corresponding to different cycle times, and a corresponding relationship between normalized ultrasonic signal amplitudes and cycle times is obtained; a corresponding relationship between normalized ultrasonic signal amplitudes and yield strengths is drawn by combining the obtained corresponding relationship between metal fatigue sample yield strengths and cycle times; a least square method is used to fit the relationship curve, a quantitative relationship expression between the normalized ultrasonic signal amplitudes and the yield strengths is obtained, and finally, ultrasonic characterization of metal fatigue damage is realized. The application provides an ultrasonic characterization method for metal fatigue damage, overcomes the problems of long test cycle, high cost and poor representativeness in the loss evaluation of metal fatigue damage, and realizes high-sensitivity and high-efficiency characterization and evaluation of metal fatigue damage.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of ultrasonic nondestructive evaluation, and particularly relates to an ultrasonic characterization method and device for metal fatigue damage. BACKGROUND

[0002] Metal fatigue refers to a phenomenon that under the action of cyclic stress or strain, metal materials or components occur damage accumulation, crack initiation and propagation under a stress level far less than the tensile strength or yield strength, and finally lead to fracture. The damage process is often difficult to be directly observed by naked eye, and has a significant impact on the mechanical properties of the material, so it is of great significance to detect and characterize the metal fatigue.

[0003] For the evaluation of metal fatigue, there are mainly two categories of destructive evaluation methods and nondestructive evaluation methods. The destructive evaluation method usually needs to destroy part or all of the test piece, and evaluates the fatigue damage degree by directly observing or measuring the internal structure and performance. This method needs to destroy the test piece, and has long test cycle and high cost, belongs to the category of sampling inspection, and cannot represent the fatigue damage condition of the whole sample. The nondestructive evaluation method can evaluate the fatigue damage degree by detecting the external or internal physical properties of the test piece without destroying it. In particular, the ultrasonic characterization method for metal fatigue damage has the advantages of high sensitivity, wide application range, high efficiency, repeatability and safety, and is an ideal method for evaluating metal fatigue damage. SUMMARY

[0004] The purpose of the present application is to provide an ultrasonic characterization method and device for metal fatigue damage, which aims to overcome the problems of long test cycle, high cost and poor representativeness in destructive evaluation of metal fatigue damage, and realize high sensitivity and efficient characterization and evaluation of metal fatigue damage.

[0005] In order to achieve the above purpose, the present application adopts the following technical solutions:

[0006] An ultrasonic characterization method for metal fatigue damage, comprising the following steps:

[0007] 1) Prepare a standard tensile specimen of metal material, and perform stress-strain experiment on a tensile testing machine to obtain the stress-strain curve of the metal material, as well as the yield strength and tensile strength parameters;

[0008] 2) Process a plurality of metal specimens of the same specification, set the fatigue load, stress ratio and cycle number of the fatigue experiment according to the metal material performance parameters obtained in step 1), and perform cyclic loading on the metal specimens on a metal fatigue testing machine to obtain a plurality of metal fatigue specimens with different cycle numbers;

[0009] 3) using the ultrasonic probe to test the prepared metal fatigue samples of different cycle times, and recording the ultrasonic detection signal amplitudes corresponding to different cycle times in turn;

[0010] 4) taking the ultrasonic detection signal amplitude of the intact metal fatigue sample as a reference, normalizing the ultrasonic signal amplitudes of the metal fatigue samples of different cycle times obtained in step 3);

[0011] 5) performing stress-strain experiments on the metal fatigue samples of different cycle times obtained in step 2) to obtain the yield strength-cycle time correspondence of the metal fatigue samples;

[0012] 6) based on the yield strength-cycle time correspondence obtained in step 5), combining the normalized ultrasonic signal amplitude-cycle time correspondence, obtaining the normalized ultrasonic signal amplitude-yield strength correspondence; using the least square method to fit the correspondence, obtaining the quantitative relationship expression of the normalized ultrasonic signal amplitude and the yield strength.

[0013] The further improvement of the present application is that the same position of the side surface of the metal sample in step 2) is processed with an artificial notch to accelerate the formation process of metal fatigue and ensure that the fatigue of different metal samples occurs at the same position.

[0014] The further improvement of the present application is that the shape of the artificial notch can be U-shaped or V-shaped, and the specific shape is determined according to the fatigue failure form of the metal part to be characterized.

[0015] The further improvement of the present application is that after the metal sample in step 2) is subjected to different cycle times of fatigue test, the artificial notch on the side surface of the sample is completely processed, and the size of each metal sample after processing is ensured to be the same, thereby obtaining metal fatigue samples of different cycle times.

[0016] The further improvement of the present application is that the minimum cycle time in step 2) is zero, and the maximum cycle time satisfies that no macroscopic crack appears at the fatigue position.

[0017] The further improvement of the present application is that the ultrasonic probe in step 3) is a transmitting-receiving probe combination or a pulse reflection single probe; the detection wave type of the transmitting-receiving probe combination is surface wave or lamb wave, and the detection wave type of the pulse reflection single probe can be longitudinal wave.

[0018] The further improvement of the present application is that the amplitude normalization processing method in step 4) is:

[0019]

[0020] In the formula, is the normalized amplitude, isc The ultrasonic signal amplitude of each cycle is is the ultrasonic signal amplitude of the intact metal fatigue specimen.

[0021] A further improvement of the present invention is that the number of cycles in step 5) and step 6) are both logarithmic.

[0022] A further improvement of the present invention is that the quantitative relationship expression between the normalized ultrasonic signal amplitude and the yield strength in step 6) is used to quantitatively evaluate the degree of fatigue damage based on the normalized ultrasonic signal amplitude.

[0023] An ultrasonic characterization device for metal fatigue damage, characterized by comprising:

[0024] Curve parameter acquisition module, used to obtain the stress-strain curve, yield strength and tensile strength parameters of metal materials;

[0025] The fatigue test module is used to obtain the metal material performance parameters obtained by the curve parameter acquisition module, set the fatigue load, stress ratio and cycle number of the fatigue test, perform cyclic loading on the metal sample, and obtain several metal fatigue samples with different cycle numbers;

[0026] Ultrasonic testing module, used to perform ultrasonic testing on prepared metal fatigue specimens with different cycle times, and record the ultrasonic testing signal amplitudes corresponding to different cycle times in sequence;

[0027] A normalization processing module is used to normalize the ultrasonic signal amplitudes of metal fatigue specimens of different cycles obtained by the ultrasonic testing module based on the ultrasonic detection signal amplitude of the intact metal fatigue specimen;

[0028] The stress-strain experiment module is used to perform stress-strain experiments on metal fatigue specimens with different cycle times obtained by the fatigue test module to obtain the corresponding relationship between the yield strength and cycle times of the metal fatigue specimens;

[0029] The normalization processing module is used to obtain the normalized ultrasonic signal amplitude-yield strength correspondence relationship based on the yield strength-cycle number correspondence relationship obtained by the stress-strain experiment module and the normalized ultrasonic signal amplitude-cycle number correspondence relationship; the least squares method is used to fit the correspondence relationship to obtain the quantitative relationship expression between the normalized ultrasonic signal amplitude and yield strength.

[0030] Compared with the prior art, the present invention has at least the following beneficial technical effects:

[0031] The application provides a metal fatigue damage ultrasonic characterization method and device, a plurality of metal fatigue samples with different cycle times are processed, ultrasonic detection technology is used to obtain detection signal amplitudes corresponding to different cycle times in sequence, and a corresponding relationship between normalized ultrasonic signal amplitudes and cycle times is obtained; the obtained yield strength-cycle time relationship of the metal fatigue sample is combined to obtain a corresponding relationship between the normalized ultrasonic signal amplitudes and the yield strength; a least square method is used to fit the relationship curve to obtain a quantitative relationship expression between the normalized ultrasonic signal amplitudes and the yield strength, and finally the ultrasonic characterization of the metal fatigue damage is realized. The application provides an ultrasonic characterization method for metal fatigue damage, and has the characteristics of high sensitivity, high efficiency, high repeatability and high safety. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 A metal fatigue damage ultrasonic characterization method flow chart is provided in the application;

[0033] Figure 2 A normalized ultrasonic signal amplitude-cycle time corresponding relationship diagram of the metal fatigue damage ultrasonic characterization method is provided in the application;

[0034] Figure 3 A yield strength-cycle time corresponding relationship diagram of the metal fatigue damage ultrasonic characterization method is provided in the application;

[0035] Figure 4 A normalized ultrasonic signal amplitude-yield strength relationship diagram of the metal fatigue damage ultrasonic characterization method is provided in the application;

[0036] Figure 5 A structural block diagram of the metal fatigue damage ultrasonic characterization device is provided in the application. DETAILED DESCRIPTION

[0037] In the following, only certain exemplary embodiments are simply described. As those skilled in the art can recognize, the described embodiments can be modified in various different ways without departing from the spirit or scope of the application. Therefore, the drawings and the description are considered to be essentially exemplary rather than limiting.

[0038] It should be understood that when used in the specification and the appended claims, the terms "comprise" and "include" indicate the presence of described features, integers, steps, operations, elements, and / or components, but do not exclude one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0039] It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used in this specification and the appended claims, the singular forms "a," "an" and "the" include plural referents unless the context clearly dictates otherwise.

[0040] It is further to be understood that the term "and / or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items, and that the term "at least one of' encompasses one or more items.

[0041] Various structural schematic diagrams according to the disclosed embodiments of the present application are shown in the accompanying drawings. These diagrams are not drawn to scale in which certain details are exaggerated for clarity and others omitted. The shapes and relative sizes of the various regions, layers, and elements illustrated in the figures are exemplary only and can vary in actual implementation depending on, for example, manufacturing techniques and tolerances, and design choices. The skilled person can design alternative regions / layers with different shapes, sizes, relative positions according to actual needs.

[0042] Embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0043] Embodiment 1

[0044] As shown in Figures 1-4 The present application provides a method for ultrasonic characterization of metal fatigue damage, comprising the following steps:

[0045] 1) Prepare a standard tensile specimen of a metal material, and perform a stress-strain experiment on a tensile testing machine to obtain a stress-strain curve of the metal material, as well as yield strength and tensile strength parameters;

[0046] 2) Process a plurality of metal specimens of the same specification, set fatigue load, stress ratio and cycle number for the fatigue experiment according to the metal material performance parameters obtained in step 1), and perform cyclic loading on the metal specimens on a metal fatigue testing machine to obtain a plurality of metal fatigue specimens of different cycle numbers;

[0047] 3) Perform ultrasonic testing on the prepared metal fatigue specimens of different cycle numbers using an ultrasonic probe, and record the ultrasonic detection signal amplitudes corresponding to different cycle numbers in turn;

[0048] 4) Take the ultrasonic detection signal amplitude of the intact metal fatigue specimen as a reference, and normalize the ultrasonic signal amplitudes of the metal fatigue specimens of different cycle numbers obtained in step 3);

[0049] 5) stress-strain experiments are performed on the metal fatigue samples of different cycle numbers obtained in step 2) to obtain the yield strength-cycle number correspondence of the metal fatigue samples;

[0050] 6) based on the yield strength-cycle number correspondence obtained in step 5), the normalized ultrasonic signal amplitude-yield strength correspondence is obtained in combination with the normalized ultrasonic signal amplitude-cycle number correspondence; the least square method is used to fit the correspondence to obtain the quantitative relationship expression of the normalized ultrasonic signal amplitude and the yield strength.

[0051] Example 2

[0052] As Figures 1-4 shown, the present application provides an ultrasonic characterization method for metal fatigue damage, comprising the following steps:

[0053] Step 1, according to the material grade of the component to be detected for fatigue damage, a standard tensile specimen of the corresponding material grade is prepared according to GB / T 228.1, and stress-strain experiments are performed on a tensile testing machine to obtain the stress-strain curve of the metal material, as well as the yield strength, tensile strength and other performance parameters.

[0054] Step 2, process several metal samples of the same specification, set the fatigue load, stress ratio and cycle number of the fatigue experiment according to the metal material performance parameters obtained in step 1, and perform cyclic loading on the metal samples on a metal fatigue testing machine to obtain several metal fatigue samples of different cycle numbers.

[0055] Preferably, the cross-sectional shape of the metal sample can be rectangular, square, etc., and the length and cross-sectional dimension should be able to enable the ultrasonic probe to be stably coupled to the surface thereof and not affect the accurate measurement of the ultrasonic detection signal amplitude.

[0056] Preferably, artificial notches are processed at the same position on the side surface of the several metal samples to accelerate the formation process of metal fatigue and ensure that fatigue occurs at the same position on different metal samples. The shape of the artificial notch can be U-shaped or V-shaped, and the specific shape is determined according to the fatigue failure form of the metal component to be characterized.

[0057] Preferably, after the metal sample is subjected to fatigue testing of different cycle numbers, the artificial notch on the side surface of the sample is completely processed, and the size of each metal sample after processing is ensured to be the same, thereby obtaining metal fatigue samples of different cycle numbers.

[0058] Preferably, the minimum cycle number is zero, and the maximum cycle number should satisfy that no macroscopic cracks appear at the fatigue position.

[0059] Step 3, using an ultrasonic probe to test the prepared metal fatigue samples of different cycle times, and record the corresponding ultrasonic detection signal amplitude of different cycle times in turn.

[0060] Preferably, the ultrasonic probe can be a transmitting-receiving probe combination, or a pulse reflection single probe. The detection wave type of the transmitting-receiving probe combination can be surface wave or lamb wave, and the detection wave type of the pulse reflection single probe can be longitudinal wave.

[0061] Step 4, taking the ultrasonic detection signal amplitude of the intact metal fatigue sample (i.e. cycle time 0) as the reference, the ultrasonic signal amplitudes of the metal fatigue samples of different cycle times obtained in step 3 are normalized.

[0062] Preferably, the amplitude normalization processing method is:

[0063]

[0064] In the formula, is the normalized amplitude, is the ultrasonic signal amplitude of the cycle time, c is the ultrasonic signal amplitude of the intact metal fatigue sample.

[0065] Step 5, stress-strain experiments are performed on the metal fatigue samples of different cycle times obtained in step 2 to obtain the yield strength-cycle time correspondence of the metal fatigue samples.

[0066] Step 6, based on the yield strength-cycle time correspondence obtained in step 5, combined with the normalized ultrasonic signal amplitude-cycle time correspondence, the normalized ultrasonic signal amplitude-yield strength correspondence is obtained. The least square method is used to fit the correspondence, and the quantitative relationship expression of the normalized ultrasonic signal amplitude and the yield strength is obtained, and the degree of fatigue damage is quantitatively evaluated.

[0067] Preferably, the cycle times in steps 5 and 6 are taken as logarithms.

[0068] Example 3

[0069] Taking GTD450 martensitic stainless steel commonly used in heavy-duty gas turbine compressor blades as an example, the ultrasonic characterization method of metal fatigue damage is as follows:

[0070] 1) According to GB / T 228.1, prepare GTD450 standard tensile specimens. To ensure the accuracy of the results, at least 3 sets of tensile specimens should be prepared, and stress-strain experiments should be performed on a tensile testing machine to obtain the average yield strength and tensile strength of the GTD450 tensile specimens.

[0071] ​2) Process at least 10 groups of metal samples of the same specification for fatigue test. The cross-sectional shape of the metal sample is rectangular, and the length should be able to make the ultrasonic probe stably coupled to its surface without affecting the accurate measurement of the ultrasonic detection signal amplitude. According to the relevant requirements of GB / T 37306.1 and GB / T 3075, combined with the yield strength of GTD450 material obtained, set the fatigue load, stress ratio and cycle number of the fatigue test.

[0072] 3) Process V-shaped artificial notches at the same position on the side of each metal sample to ensure that fatigue occurs at the same position on different metal samples. Load 10 groups of metal samples on the metal fatigue testing machine for different cycle numbers, and completely process the artificial notches on the side of the obtained samples to ensure that the outer dimensions of the 10 groups of metal samples after processing are the same, and obtain 10 groups of metal fatigue samples with different cycle numbers. At least one of the 10 groups of fatigue samples has not been subjected to fatigue cycles, and the fatigue sample with the maximum cycle number should not appear macroscopic cracks.

[0073] 4) Use a transmitting and receiving ultrasonic probe to transmit and receive surface waves at the fatigue position of the metal fatigue sample, and perform ultrasonic testing on the prepared metal fatigue samples with different cycle numbers, and record the ultrasonic detection signal amplitudes corresponding to different cycle numbers in turn.

[0074] 5) Take the ultrasonic detection signal amplitude of the intact metal fatigue sample (i.e. cycle number 0) as the reference, and normalize the ultrasonic signal amplitudes of the metal fatigue samples with different cycle numbers to obtain the corresponding relationship between the normalized ultrasonic signal amplitude and the cycle number, wherein the cycle number is taken as the logarithm.

[0075] The amplitude normalization processing method is:

[0076]

[0077] In the formula, is the normalized amplitude, is the ultrasonic signal amplitude of the cycle number, c is the ultrasonic signal amplitude of the intact metal fatigue sample.

[0078] 6) According to GB / T 228.1, perform stress-strain experiments on 10 groups of metal fatigue samples with different cycle numbers to obtain the corresponding relationship between the yield strength of the GTD450 material metal fatigue sample and the cycle number (the cycle number is taken as the logarithm). Combined with the corresponding relationship between the normalized ultrasonic signal amplitude and the cycle number, obtain the corresponding relationship between the normalized ultrasonic signal amplitude and the yield strength.

[0079] ​7) The least square method is used to fit the normalized ultrasonic signal amplitude-yield strength corresponding relationship, and a quantitative relationship expression of the normalized ultrasonic signal amplitude and the yield strength is obtained, and the degree of fatigue damage is quantitatively evaluated.

[0080] The quantitative relationship expression is constructed as follows:

[0081]

[0082] In the formula, a 0, a 1, …, a m is a coefficient of the quantitative relationship expression, σ is the yield strength.

[0083] The residual sum of squares calculation formula is as follows:

[0084]

[0085] In the formula, S r is the residual sum of squares, n is the number of metal fatigue samples, A nori is the normalized ultrasonic signal amplitude of the m-th metal fatigue sample. i The value of is obtained by finding the minimum value of the residual sum of squares, and the quantitative relationship expression is obtained.

[0086] a 0, a 1, …, a m

[0087] Example 4

[0088] As shown in Figure 5 , the application provides a metal fatigue damage ultrasonic characterization device, which comprises:

[0089] A curve parameter acquisition module is configured to obtain a stress-strain curve of a metal material, and yield strength and tensile strength parameters.

[0090] A fatigue test module is configured to set a fatigue load, a stress ratio and a cycle number of a fatigue test according to the metal material performance parameters obtained by the curve parameter acquisition module, and perform cyclic loading on a metal sample to obtain metal fatigue samples with different cycle numbers.

[0091] An ultrasonic test module is configured to perform ultrasonic testing on the prepared metal fatigue samples with different cycle numbers, and sequentially record ultrasonic detection signal amplitudes corresponding to different cycle numbers.

[0092] ​​The first normalization processing module is configured to normalize the ultrasonic signal amplitudes of the metal fatigue samples with different cycle times obtained by the ultrasonic testing module based on the ultrasonic testing signal amplitude of the intact metal fatigue sample.

[0093] The stress-strain experiment module is configured to perform a stress-strain experiment on the metal fatigue samples with different cycle times obtained by the fatigue test module to obtain a yield strength-cycle time correspondence of the metal fatigue samples.

[0094] The second normalization processing module is configured to obtain a normalized ultrasonic signal amplitude-yield strength correspondence based on the yield strength-cycle time correspondence obtained by the stress-strain experiment module and the normalized ultrasonic signal amplitude-cycle time correspondence, and to obtain a quantitative relationship expression between the normalized ultrasonic signal amplitude and the yield strength by fitting the correspondence using a least square method.

[0095] The basic principle and main features of the present application and the advantages of the present application are shown and described above, and it is obvious for those skilled in the art that the present application is not limited to the details of the above exemplary embodiments, and the present application can be realized in other specific forms without departing from the spirit or essential characteristics of the present application. Therefore, the embodiments should be regarded as exemplary and non-limiting, and the scope of the present application is defined by the appended claims rather than the above description, and it is intended to encompass all changes falling within the meaning and scope of the equivalent elements of the claims. Any reference signs in the claims should not be regarded as limiting the claims involved.

[0096] In addition, it should be understood that although the present specification is described in terms of embodiments, not every embodiment contains only one independent technical solution, and the description of the specification is only for the sake of clarity, and those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be properly combined to form other embodiments that those skilled in the art can understand. The above is only to illustrate the technical idea of the present application, and cannot limit the protection scope of the present application, and any modification made on the basis of the technical solutions according to the present application falls within the protection scope of the claims of the present application.

Claims

1. A method for ultrasonic characterization of metal fatigue damage, characterized in that: The following steps are involved: 1) Prepare standard tensile specimens of metal materials and conduct stress-strain experiments on a tensile testing machine to obtain the stress-strain curve, yield strength, and tensile strength parameters of the metal materials; 2) Processing a number of metal specimens of the same specifications, setting the fatigue load, stress ratio, and number of cycles of the fatigue test based on the metal material performance parameters obtained in step 1), and subjecting the metal specimens to cyclic loading on a metal fatigue testing machine to obtain a number of metal fatigue specimens with different numbers of cycles; 3) Use an ultrasonic probe to perform ultrasonic testing on the prepared metal fatigue specimens with different cycle times, and record the ultrasonic detection signal amplitudes corresponding to different cycle times in sequence; 4) Based on the ultrasonic detection signal amplitude of the intact metal fatigue specimen, the ultrasonic signal amplitudes of the metal fatigue specimens with different cycle times obtained in step 3) are normalized; 5) performing stress-strain experiments on the metal fatigue specimens obtained in step 2) with different cycle times to obtain the corresponding relationship between the yield strength and cycle times of the metal fatigue specimens; 6) Based on the yield strength-cycle number correspondence obtained in step 5), combined with the normalized ultrasonic signal amplitude-cycle number correspondence, the normalized ultrasonic signal amplitude-yield strength correspondence is obtained; the correspondence is fitted using the least squares method to obtain a quantitative relationship expression between the normalized ultrasonic signal amplitude and yield strength.

2. The ultrasonic characterization method for metal fatigue damage according to claim 1, characterized in that: In step 2), artificial grooves are machined on the same position on the side surfaces of several metal specimens to accelerate the formation process of metal fatigue and ensure that fatigue of different metal specimens occurs at the same position.

3. The ultrasonic characterization method for metal fatigue damage according to claim 2, characterized in that: The shape of the artificial groove can be U-shaped or V-shaped, and the specific shape is determined according to the fatigue failure mode of the metal component to be characterized.

4. The ultrasonic characterization method for metal fatigue damage according to claim 1, characterized in that: After the metal specimens in step 2) have undergone fatigue tests of different cycles, the artificial grooves on the sides of the specimens are completely machined away, and it is ensured that the external dimensions of each metal specimen after machining are the same, thereby obtaining metal fatigue specimens of different cycles.

5. The ultrasonic characterization method for metal fatigue damage according to claim 1, characterized in that: The minimum number of cycles in step 2) is zero, and the maximum number of cycles satisfies the requirement that no macro cracks appear at the fatigue position.

6. The ultrasonic characterization method for metal fatigue damage according to claim 1, characterized in that: The ultrasonic probe in step 3) is a combination of a transmitting and receiving probe, or a single pulse reflection probe; the detection waveform of the combination of a transmitting and receiving probe is surface wave or lambda wave, and the detection waveform of the single pulse reflection probe can be longitudinal wave.

7. The ultrasonic characterization method for metal fatigue damage according to claim 1, characterized in that: The amplitude normalization processing method in step 4) is: Where, is the normalized amplitude, for c The ultrasonic signal amplitude of each cycle is is the ultrasonic signal amplitude of the intact metal fatigue specimen.

8. The ultrasonic characterization method for metal fatigue damage according to claim 1, characterized in that: The number of cycles in steps 5) and 6) is logarithmic.

9. The ultrasonic characterization method for metal fatigue damage according to claim 1, characterized in that: The quantitative relationship expression between the normalized ultrasonic signal amplitude and the yield strength in step 6) is used to quantitatively evaluate the degree of fatigue damage based on the normalized ultrasonic signal amplitude.

10. An ultrasonic characterization device for metal fatigue damage, characterized in that: include: Curve parameter acquisition module, used to obtain the stress-strain curve, yield strength and tensile strength parameters of metal materials; The fatigue test module is used to obtain the metal material performance parameters obtained by the curve parameter acquisition module, set the fatigue load, stress ratio and cycle number of the fatigue test, perform cyclic loading on the metal sample, and obtain several metal fatigue samples with different cycle numbers; Ultrasonic testing module, used to perform ultrasonic testing on prepared metal fatigue specimens with different cycle times, and record the ultrasonic testing signal amplitudes corresponding to different cycle times in sequence; A normalization processing module is used to normalize the ultrasonic signal amplitudes of metal fatigue specimens of different cycles obtained by the ultrasonic testing module based on the ultrasonic detection signal amplitude of the intact metal fatigue specimen; The stress-strain experiment module is used to perform stress-strain experiments on metal fatigue specimens with different cycle times obtained by the fatigue test module to obtain the corresponding relationship between the yield strength and cycle times of the metal fatigue specimens; The normalization processing module is used to obtain the normalized ultrasonic signal amplitude-yield strength correspondence relationship based on the yield strength-cycle number correspondence relationship obtained by the stress-strain experiment module and the normalized ultrasonic signal amplitude-cycle number correspondence relationship; the least squares method is used to fit the correspondence relationship to obtain the quantitative relationship expression between the normalized ultrasonic signal amplitude and yield strength.

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