Ultrasonic characterization method and device for metal fatigue damage

Abstract

According to the ultrasonic characterization method and device for the metal fatigue damage, a plurality of metal fatigue samples with different circulation cycles are machined, detection signal amplitudes corresponding to the different circulation cycles are sequentially obtained through an ultrasonic detection technology, and the corresponding relation between the normalized ultrasonic signal amplitudes and the circulation cycles is obtained; a normalized ultrasonic signal amplitude-yield strength corresponding relation is made by combining the obtained metal fatigue sample yield strength-cycle number corresponding relation; and fitting the relation curve by adopting a least square method to obtain a quantitative relation expression of the normalized ultrasonic signal amplitude and the yield strength, and finally realizing the ultrasonic characterization of the metal fatigue damage. The invention provides an ultrasonic characterization method for metal fatigue damage, solves the problems of long test period, high cost and low representativeness during metal fatigue damage lossy evaluation, and realizes high sensitivity and efficient characterization and evaluation of metal fatigue damage.

Description

Technical Field

[0001] The invention belongs to the field of ultrasonic nondestructive evaluation, and in particular relates to an ultrasonic characterization method and device for metal fatigue damage. Background Art

[0002] Metal fatigue refers to the phenomenon that under cyclic stress or strain, metal materials or components accumulate damage, cracks initiate and expand at stress levels far less than their tensile strength or yield strength, and eventually break. The damage process is often difficult to observe directly with the naked eye, and has a significant impact on the mechanical properties of the material, so its detection and characterization are of great significance.

[0003] The evaluation of metal fatigue is mainly divided into two categories: destructive evaluation methods and non-destructive evaluation methods. Destructive evaluation methods usually require the destruction of part or all of the test piece, and the degree of fatigue damage is evaluated by directly observing or measuring its internal structure and performance. This method requires the destruction of the test piece, and the test cycle is long and the cost is high. It belongs to the category of sampling inspection and cannot represent the fatigue damage of the sample as a whole. Non-destructive evaluation methods can evaluate the degree of fatigue damage by detecting its external or internal physical properties without destroying the test piece. In particular, the ultrasonic characterization method of metal fatigue damage has the advantages of high sensitivity, wide application range, high efficiency, repeatability and safety. It is an ideal method for metal fatigue damage evaluation. Summary of the invention

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

[0005] In order to achieve the above object, the present invention adopts the following technical solution: An ultrasonic characterization method for metal fatigue damage comprises the following steps: 1) Prepare standard tensile specimens of metal materials and conduct stress-strain experiments on a tensile testing machine to obtain stress-strain curves, yield strength and tensile strength parameters of metal materials; 2) Processing a number of metal specimens of the same specification, setting the fatigue load, stress ratio and cycle number of the fatigue test according to the metal material performance parameters obtained in step 1), and cyclically loading the metal specimens on a metal fatigue testing machine to obtain a number of metal fatigue specimens with different cycle numbers; 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 turn; 4) Taking the ultrasonic detection signal amplitude of the intact metal fatigue specimen as a reference, normalize the ultrasonic signal amplitudes of the metal fatigue specimens with different cycle times obtained in step 3); 5) Perform stress-strain experiments on the metal fatigue specimens with different cycle times obtained in step 2) 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 the yield strength.

[0006] A further improvement of the present invention is that in step 2), artificial grooves are processed at the same position on the side surfaces of several metal samples to accelerate the formation process of metal fatigue and ensure that fatigue of different metal samples occurs at the same position.

[0007] A further improvement of the present invention is 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 form of the metal component to be characterized.

[0008] A further improvement of the present invention is that after the metal specimens in step 2) have been subjected to fatigue tests of different cycles, the artificial grooves on the sides of the specimens are completely machined away, and the dimensions of each metal specimen after machining are ensured to be the same, thereby obtaining metal fatigue specimens of different cycles.

[0009] A further improvement of the present invention is that the minimum cycle number in step 2) is zero, and the maximum cycle number satisfies that no macro cracks appear at the fatigue position.

[0010] A further improvement of the present invention is that the ultrasonic probe in step 3) is a one-transmit-one-receive probe combination, or a pulse reflection single probe; the one-transmit-one-receive probe combination detects a surface wave or a lambda wave, and the pulse reflection single probe detects a longitudinal wave.

[0011] A further improvement of the present invention is that the amplitude normalization processing method in step 4) is:

[0012] In the formula, is the normalized amplitude, for c The amplitude of the ultrasonic signal of each cycle is is the ultrasonic signal amplitude of the intact metal fatigue specimen.

[0013] A further improvement of the present invention is that the number of cycles in step 5) and step 6) are both logarithmic.

[0014] 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 according to the normalized ultrasonic signal amplitude.

[0015] An ultrasonic characterization device for metal fatigue damage, characterized by comprising: 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 through 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; The ultrasonic testing module is used to perform ultrasonic testing on the 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 the yield strength.

[0016] Compared with the prior art, the present invention has at least the following beneficial technical effects: The present invention provides an ultrasonic characterization method and device for metal fatigue damage. By processing a number of metal fatigue specimens with different cycles, ultrasonic detection technology is used to sequentially obtain the detection signal amplitudes corresponding to different cycles, and the normalized ultrasonic signal amplitude-cycle correspondence relationship is obtained; combined with the obtained metal fatigue specimen yield strength-cycle relationship, the normalized ultrasonic signal amplitude-yield strength correspondence relationship is obtained; the relationship curve is fitted using the least squares method to obtain a quantitative relationship expression between the normalized ultrasonic signal amplitude and the yield strength, and finally the ultrasonic characterization of metal fatigue damage is realized. The present invention provides an ultrasonic characterization method for metal fatigue damage, which has the characteristics of high sensitivity, high efficiency, high repeatability and high safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a flow chart of an ultrasonic characterization method for metal fatigue damage of the present invention; Figure 2 A corresponding relationship diagram of normalized ultrasonic signal amplitude-cycle number of an ultrasonic characterization method for metal fatigue damage of the present invention; Figure 3 A yield strength-cycle number correspondence diagram of an ultrasonic characterization method for metal fatigue damage of the present invention; Figure 4 A normalized ultrasonic signal amplitude-yield strength relationship diagram of an ultrasonic characterization method for metal fatigue damage of the present invention; Figure 5 The present invention is a structural block diagram of an ultrasonic characterization device for metal fatigue damage. DETAILED DESCRIPTION

[0018] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0019] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0020] It should also be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0021] It should be further understood that the term "and / or" used in the present description and the appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0022] Various structural schematic diagrams of the embodiments disclosed in the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0023] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0024] Example 1 like Figure 1 to Figure 4 As shown, the present invention provides an ultrasonic characterization method for metal fatigue damage, comprising the following steps: 1) Prepare standard tensile specimens of metal materials and conduct stress-strain experiments on a tensile testing machine to obtain stress-strain curves, yield strength and tensile strength parameters of metal materials; 2) Processing a number of metal specimens of the same specification, setting the fatigue load, stress ratio and cycle number of the fatigue test according to the metal material performance parameters obtained in step 1), and cyclically loading the metal specimens on a metal fatigue testing machine to obtain a number of metal fatigue specimens with different cycle numbers; 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 turn; 4) Taking the ultrasonic detection signal amplitude of the intact metal fatigue specimen as a reference, normalize the ultrasonic signal amplitudes of the metal fatigue specimens with different cycle times obtained in step 3); 5) Perform stress-strain experiments on the metal fatigue specimens with different cycle times obtained in step 2) 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 the yield strength.

[0025] Example 2 like Figure 1 to Figure 4 As shown, the present invention provides an ultrasonic characterization method for metal fatigue damage, comprising the following steps: Step 1: According to the material grade of the component to be tested for fatigue damage, prepare a standard tensile specimen of the corresponding material grade according to GB / T 228.1, and perform a stress-strain experiment on a tensile testing machine to obtain the stress-strain curve of the metal material, as well as performance parameters such as yield strength and tensile strength.

[0026] Step 2: Process several metal specimens of the same specification, set the fatigue load, stress ratio and cycle number of the fatigue test 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 several metal fatigue specimens with different cycle numbers.

[0027] Preferably, the cross-sectional shape of the metal sample may be rectangular, square, etc., and its length and cross-sectional dimensions should enable the ultrasonic probe to be stably coupled to its surface without affecting the accurate measurement of the amplitude of the ultrasonic detection signal.

[0028] Preferably, the same position on the side of several metal samples is processed with artificial grooves to accelerate the formation process of metal fatigue and ensure that fatigue of different metal samples occurs at the same position. The shape of the artificial groove 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.

[0029] Preferably, after the metal specimens have been subjected to fatigue tests of different cycles, the artificial grooves on the sides of the specimens are completely machined away, and it is ensured that the outer dimensions of each metal specimen after machining are the same, thereby obtaining metal fatigue specimens of different cycles.

[0030] Preferably, the minimum number of cycles is zero, and the maximum number of cycles should be such that no macro cracks appear at the fatigue position.

[0031] Step 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.

[0032] Preferably, the ultrasonic probe can be a combination of a transmitter and a receiver probe, or a single pulse reflection probe. The detection waveform of the combination of a transmitter and a receiver probe can be a surface wave or a lambda wave, and the detection waveform of the single pulse reflection probe can be a longitudinal wave.

[0033] Step 4: Taking the ultrasonic detection signal amplitude of the intact metal fatigue specimen (i.e., the cycle number is 0) as a reference, the ultrasonic signal amplitudes of the metal fatigue specimens with different cycle numbers obtained in step 3 are normalized.

[0034] Preferably, the amplitude normalization processing method is:

[0035] In the formula, is the normalized amplitude, for c The amplitude of the ultrasonic signal of each cycle is is the ultrasonic signal amplitude of the intact metal fatigue specimen.

[0036] Step 5: Perform stress-strain experiments on the metal fatigue specimens with different cycle times obtained in step 2 to obtain the corresponding relationship between the yield strength and the cycle times of the metal fatigue specimens.

[0037] Step 6: Based on the yield strength-cycle number correspondence obtained in step 5, combined with the normalized ultrasonic signal amplitude-cycle number correspondence, obtain the normalized ultrasonic signal amplitude-yield strength correspondence. The least squares method is used to fit the correspondence to obtain a quantitative relationship expression between the normalized ultrasonic signal amplitude and the yield strength, and the degree of fatigue damage is quantitatively evaluated.

[0038] Preferably, the number of cycles in step 5 and step 6 are both logarithmic.

[0039] Example 3 Taking GTD450 martensitic stainless steel commonly used in heavy-duty gas turbine compressor blades as an example, the ultrasonic characterization method of its metal fatigue damage is as follows: 1) Prepare GTD450 standard tensile specimens according to GB / T 228.1. To ensure the accuracy of the results, at least 3 groups of tensile specimens should be prepared, and stress-strain experiments should be carried out on a tensile testing machine to obtain the average yield strength and tensile strength of GTD450 tensile specimens.

[0040] 2) Process at least 10 groups of metal specimens of the same specifications for fatigue testing. The cross-sectional shape of the metal specimen is rectangular, and the length should be able to stably couple the ultrasonic probe 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 obtained GTD450 material yield strength, set the fatigue load, stress ratio and cycle number of the fatigue test.

[0041] 3) V-shaped artificial grooves are processed at the same position on the side of each metal specimen to ensure that fatigue of different metal specimens occurs at the same position. 10 groups of metal specimens are loaded with different cycles on the metal fatigue testing machine, and the artificial grooves on the sides of the obtained specimens are completely processed to ensure that the outer dimensions of the 10 groups of metal specimens after processing are the same, and 10 groups of metal fatigue specimens with different cycles are obtained. At least one of the 10 groups of fatigue specimens has not been fatigue cycled, and the fatigue specimen with the maximum cycle should not have macro cracks.

[0042] 4) A transmit-receive ultrasonic probe is used to transmit and receive surface waves at the fatigue position of the metal fatigue specimen, and ultrasonic tests are performed on the prepared metal fatigue specimens with different cycle times, and the ultrasonic detection signal amplitudes corresponding to different cycle times are recorded in turn.

[0043] 5) Taking the ultrasonic detection signal amplitude of the intact metal fatigue specimen (i.e., the cycle number is 0) as a reference, the ultrasonic signal amplitudes of the metal fatigue specimens with different cycle numbers are normalized to obtain the corresponding relationship between the normalized ultrasonic signal amplitude and the cycle number, where the cycle number is taken as the logarithm.

[0044] The amplitude normalization processing method is:

[0045] In the formula, is the normalized amplitude, for c The amplitude of the ultrasonic signal of each cycle is is the ultrasonic signal amplitude of the intact metal fatigue specimen.

[0046] 6) According to GB / T 228.1, stress-strain tests were conducted on 10 groups of metal fatigue specimens with different cycles to obtain the corresponding relationship between yield strength and cycle number of GTD450 material metal fatigue specimens (logarithm of cycle number). Combined with the corresponding relationship between normalized ultrasonic signal amplitude and cycle number, the corresponding relationship between normalized ultrasonic signal amplitude and yield strength was obtained.

[0047] 7) The least squares method is used to fit the normalized ultrasonic signal amplitude-yield strength correspondence relationship, and the quantitative relationship expression between the normalized ultrasonic signal amplitude and the yield strength is obtained to quantitatively evaluate the degree of fatigue damage.

[0048] Construct a quantitative relationship expression:

[0049] In the formula, a 0 , a 1 , …, a m is the coefficient of the quantitative relationship expression, σ is the yield strength.

[0050] The residual sum of squares is calculated as:

[0051] In the formula, S r is the residual sum of squares, n is the number of metal fatigue specimens, A nori For the i Normalized ultrasonic signal amplitude of a metal fatigue specimen.

[0052] By finding the minimum value of the residual sum of squares, we can obtain a 0 , a 1 , …, a m , thereby obtaining a quantitative relationship expression.

[0053] Example 4 like Figure 5 As shown, the present invention provides an ultrasonic characterization device for metal fatigue damage, comprising: 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 through 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; The ultrasonic testing module is used to perform ultrasonic testing on the prepared metal fatigue specimens with different cycle times, and record the ultrasonic testing signal amplitudes corresponding to different cycle times in sequence; A first normalization processing module is used to normalize the ultrasonic signal amplitudes of the 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 second 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 the yield strength.

[0054] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the attached claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention. Any figure mark in the claims should not be regarded as limiting the claims involved.

[0055] In addition, it should be understood that although this specification is described in accordance with the implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation modes that can be understood by those skilled in the art. The above content is only to illustrate the technical idea of ​​the present invention, and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution according to the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

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 stress-strain curves, yield strength and tensile strength parameters of metal materials; 2) Processing a number of metal specimens of the same specification, setting the fatigue load, stress ratio and cycle number of the fatigue test according to the metal material performance parameters obtained in step 1), and cyclically loading the metal specimens on a metal fatigue testing machine to obtain a number of metal fatigue specimens with different cycle numbers; 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 turn; 4) Taking the ultrasonic detection signal amplitude of the intact metal fatigue specimen as a reference, normalize the ultrasonic signal amplitudes of the metal fatigue specimens with different cycle times obtained in step 3); 5) Perform stress-strain experiments on the metal fatigue specimens with different cycle times obtained in step 2) 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 the yield strength.

2. The ultrasonic characterization method for metal fatigue damage according to claim 1, characterized in that: In step 2), artificial grooves are processed at the same position on the side of several metal samples to accelerate the formation process of metal fatigue and ensure that fatigue of different metal samples 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 form 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 been subjected to fatigue tests of different cycles, the artificial grooves on the sides of the specimens are completely machined away, and it is ensured that the outer 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 and lamb 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: In the formula, is the normalized amplitude, for c The amplitude of the ultrasonic signal 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 step 5) and step 6) are both 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 according to 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 through 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; The ultrasonic testing module is used to perform ultrasonic testing on the 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 the yield strength.

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