A method, device and equipment for predicting a fatigue small crack threshold value and a storage medium

Abstract

The application discloses a fatigue small crack threshold value prediction method and device, equipment and a storage medium, and relates to the technical field of material science and engineering, and the method comprises the following steps: performing a high-cycle fatigue test on a to-be-predicted material to obtain a fatigue limit, an initial crack size and a fatigue small crack propagation form of the to-be-predicted material; determining a dimensionless stress intensity factor according to the initial crack size and the fatigue small crack propagation form; and predicting a fatigue small crack threshold value of the to-be-predicted material based on the fatigue limit, the initial crack size and the dimensionless stress intensity factor. Therefore, the fatigue small crack threshold value can be efficiently and low-costly obtained.

Description

Technical Field

[0001] This application relates to the field of materials science and engineering application technology, and in particular to a method, apparatus, device and storage medium for predicting fatigue small crack threshold values. Background Technology

[0002] Fatigue fracture is one of the main fracture modes of aero-engine materials, making the prediction of fatigue fracture behavior a major research direction for scholars and experts. The description of fatigue crack propagation using fracture mechanics concepts is typically based on the results of laboratory fatigue tests, using specimens containing long cracks tens of millimeters in length. However, for some engineering components controlled by fatigue failure, such as turbine disks and blades in aero-engines, the design requires understanding the propagation characteristics of very small-scale fatigue cracks.

[0003] Currently, the fatigue small crack threshold value of materials is mainly obtained through experimental methods. It typically requires half a month to a month of testing to obtain a crack propagation rate of 10-1. -7 The data around mm / cycle is used to fit the stress intensity factor range corresponding to the rate, which is the fatigue crack threshold value. However, this method is time-consuming and costly. Summary of the Invention

[0004] Therefore, the main objective of this application is to provide a method, apparatus, device, and storage medium for predicting fatigue small crack threshold values, with the aim of achieving rapid and low-cost prediction of fatigue small crack threshold values.

[0005] The first aspect of this application provides a method for predicting fatigue small crack threshold values, the method comprising:

[0006] High-cycle fatigue tests are conducted on the material to be predicted in order to obtain the fatigue limit, initial crack size and fatigue small crack propagation mode of the material to be predicted.

[0007] The dimensionless stress intensity factor is determined by the initial crack size and the fatigue small crack propagation mode.

[0008] The fatigue small crack threshold value of the material to be predicted is based on fatigue limit, initial crack size, and dimensionless stress intensity factor.

[0009] In some implementations of the first aspect of this application, high-cycle fatigue testing is performed on the material to be predicted, including:

[0010] High-cycle fatigue tests were conducted on the material to be predicted in order to obtain stress-life data of the material to be predicted.

[0011] The stress-life curve is obtained by fitting the stress-life data;

[0012] In the stress-life curve, the fatigue strength corresponding to the preset life value is determined as the fatigue limit.

[0013] In some implementations of the first aspect of this application, the preset lifetime value is 10. 7 .

[0014] In some implementations of the first aspect of this application, high-cycle fatigue testing is performed on the material to be predicted, including:

[0015] High-cycle fatigue tests were conducted on the material to be predicted in order to obtain the fatigue fracture morphology of the material.

[0016] The fatigue origin shape, fatigue origin size distribution, and fatigue microcrack propagation mode of the material to be predicted are determined based on the fatigue fracture morphology.

[0017] The initial crack size of the material to be predicted is determined based on the shape and size distribution of the fatigue source.

[0018] In some implementations of the first aspect of this application, the initial crack size can also be obtained by performing non-destructive testing on the material to be predicted.

[0019] In some implementations of the first aspect of this application, the fatigue small crack threshold value of the material to be predicted is predicted by the following formula:

[0020]

[0021] Where, ΔK th Δσ represents the fatigue small crack threshold value. e Indicates the fatigue limit, a i denoted by , where f represents the initial crack size and f represents the dimensionless stress intensity factor.

[0022] A second aspect of this application provides a fatigue small crack threshold prediction device, the device comprising:

[0023] The fatigue testing module is used to perform high-cycle fatigue tests on the material to be predicted in order to obtain the fatigue limit, initial crack size and fatigue small crack propagation mode of the material to be predicted.

[0024] The parameter determination module is used to determine the dimensionless stress intensity factor based on the initial crack size and the fatigue small crack propagation mode.

[0025] The numerical prediction module is used to predict the fatigue small crack threshold value of the material to be predicted based on the fatigue limit, initial crack size, and dimensionless stress intensity factor.

[0026] In some implementations of the second aspect of this application, the fatigue testing module is specifically used for:

[0027] The high-cycle fatigue test is performed on the material to be predicted to obtain stress-life data of the material to be predicted;

[0028] The stress-life curve is obtained by fitting the stress-life data;

[0029] In the stress-life curve, the fatigue strength corresponding to the preset life value is determined as the fatigue limit.

[0030] In some implementations of the second aspect of this application, the fatigue testing module is specifically used for:

[0031] High-cycle fatigue tests were performed on the material to be predicted to obtain the fatigue fracture morphology of the material to be predicted.

[0032] Based on the fatigue fracture morphology, the fatigue origin shape, fatigue origin size distribution, and fatigue microcrack propagation mode of the material to be predicted are determined.

[0033] The initial crack size of the material to be predicted is determined based on the shape of the fatigue source and the size distribution of the fatigue source.

[0034] A third aspect of this application provides a fatigue small crack threshold prediction device, which includes a memory and a processor. The processor is used to execute a program stored in the memory and run a fatigue small crack threshold prediction method as provided in any of the first aspects of this application.

[0035] The fourth aspect of this application provides a readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the various steps of the fatigue small crack threshold prediction method as provided in any of the first aspects of this application.

[0036] The technical solution provided in this application has the following beneficial effects:

[0037] First, high-cycle fatigue tests are conducted on the test samples to obtain the fatigue limit, initial crack size, and fatigue small crack propagation mode. Then, based on the fatigue small crack propagation mode and initial crack size, the dimensionless stress intensity factor is further determined. Finally, based on the fatigue limit, initial crack size, and dimensionless stress intensity factor, the fatigue small crack threshold value is predicted according to the formula, thereby achieving efficient and low-cost prediction of the fatigue small crack threshold value. Attached Figure Description

[0038] Figure 1 A flowchart illustrating a fatigue small crack threshold prediction method provided in this application embodiment;

[0039] Figure 2 A flowchart illustrating a fatigue small crack threshold prediction method provided in this application embodiment;

[0040] Figure 3 The SN curve of a GH4169 alloy single-sided notched tensile specimen;

[0041] Figure 4 A schematic diagram of the macroscopic morphology of fatigue fracture surface and crack propagation of GH4169 alloy;

[0042] Figure 5 This is a diagram showing the initial crack size distribution of the fatigue source in GH4169 alloy.

[0043] Figure 6 Fatigue crack propagation curve for fatigue microcrack propagation in GH4169 alloy;

[0044] Figure 7 A schematic diagram of a fatigue small crack threshold prediction device provided in an embodiment of this application;

[0045] Figure 8 This is a schematic diagram of a fatigue small crack threshold prediction device provided in an embodiment of this application. Detailed Implementation

[0046] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0047] The terms "first," "second," "third," "fourth," etc., used in the specification, claims, and accompanying drawings of this application, are used, if present, to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data used in this way can be interchanged where appropriate so that the embodiments described herein can be implemented in a sequence other than that illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0048] See Figure 1 As shown in the figure, this application provides a method for predicting the fatigue small crack threshold value, which specifically includes the following steps:

[0049] S101: Conduct high-cycle fatigue tests on the material to be predicted to obtain the fatigue limit, initial crack size, and fatigue small crack propagation mode of the material to be predicted.

[0050] In the embodiments of this application, the material to be predicted for high-cycle fatigue testing is a uniformly structured metallic material. Specifically, the material to be predicted can be a uniformly structured metallic aerospace material, which can also be called a sample material, or simply a sample.

[0051] High-cycle fatigue testing, also known as SN testing, is a test method that tests the fatigue life of a material by applying cyclic stress to it. This test can determine the stress intensity that a specific material can withstand under different stress ratios and different number of cycles.

[0052] Fatigue limit refers to the stress level at which a material under test can withstand a certain number of cycles without fracturing under a given stress. For example, the material under test can withstand 10 cycles. 6 Stress can be applied without causing cracks, and the cycle count is 10. 7 If the applied stress causes cracks, then the number of cycles is 10. 6 The corresponding stress intensity is the fatigue limit.

[0053] The initial crack size refers to the size of a crack that has not yet begun to propagate in the material after a high-cycle fatigue test. In a high-cycle fatigue test, a material will develop an initial crack after a certain number of cyclic stresses under certain stress conditions. This initial crack can then propagate until the material fractures. Here, the initial crack size is the size of the initial crack. Since cracks may occur inside or on the surface of the specimen, the initial crack size can be the size of a crack on the surface or inside the specimen. It should be noted that the initial crack size exhibits similar behavior under different stress ratios, thus possessing a certain degree of universality. Furthermore, the initial crack size can be obtained through different technical means, such as non-destructive testing, fatigue fracture analysis, or direct definition. It should be noted that in the subsequent embodiments of this application, the initial crack size is obtained based on fatigue fracture analysis, but this application is not limited to obtaining the initial crack size solely through fatigue fracture analysis.

[0054] The fatigue microcrack propagation mode refers to the manifestation of the initiating crack after high-cycle fatigue testing. The crack propagation mode varies for different materials under fatigue load. For example, fatigue cracks in Al alloy plate specimens usually start on the specimen surface or at the edges of the specimen surface, that is, the fatigue microcrack propagation mode is surface crack or corner crack. On the other hand, fatigue cracks in high-temperature alloy rod specimens usually start inside the specimen, and their fatigue microcrack propagation mode is elliptical or circular internal crack.

[0055] It should be noted that the fatigue limit is derived from the statistical analysis of the limit at which a specimen does not develop a fatigue fracture under cyclic stress during high-cycle fatigue testing. After undergoing a certain number of cycles under specific stress conditions, the specimen will develop a fatigue fracture. The initial crack size and the propagation pattern of small fatigue cracks are obtained by observing the fatigue fracture surface. Based on the fatigue limit, initial crack size, and the propagation pattern of small fatigue cracks, the microstructure and fatigue loss mechanism of the material to be predicted can be comprehensively considered.

[0056] S102: Determine the dimensionless stress intensity factor by using the initial crack size and the fatigue small crack propagation mode.

[0057] In the embodiments of this application, the dimensionless stress intensity factor is a parameter characterizing the stress field at the crack tip, used to reflect the degree of stress concentration at the crack tip. This stress intensity factor is related to the geometry, size, and location of the crack, as well as the magnitude and direction of the external load. The composition of the finite-size influence of the crack body (including the shape and size of the material to be predicted), the crack shape and size, the loading method, and the load / displacement boundary conditions are characterized by the dimensionless stress intensity factor. The loading method refers to the conditions for pre-setting a fatigue small crack threshold value. For example, to predict the fatigue small crack threshold value under room temperature and a stress ratio of -1, then this stress ratio of -1 is the loading method. The load / displacement boundary conditions are related to the shape and size of the material to be predicted. It should be noted that the finite-size influence of the crack body, the loading method, and the load / displacement boundary conditions are common knowledge formulas, and the determination method of the dimensionless intensity factor can be found in the "Stress Intensity Factor Handbook".

[0058] Here, determining the dimensionless stress intensity factor through initial crack size and fatigue small crack propagation mode does not imply that the dimensionless stress intensity factor can be determined solely by the initial crack size and fatigue small crack propagation mode. Rather, it should be understood as obtaining the initial crack size and fatigue small crack propagation mode through high-cycle fatigue testing, and then determining the dimensionless stress intensity factor. Specifically, the shape and size of the material to be predicted, and the load / displacement boundary conditions related to the shape and size of the material to be predicted, are obtained based on existing conditions; that is, the shape and size and load / displacement boundary conditions can be determined based on the existing material to be predicted. The loading method is a pre-set prediction condition that can be flexibly set according to different needs. The fatigue small crack propagation mode and initial crack size, however, need to be obtained through high-cycle fatigue testing. Therefore, in the process of determining the dimensionless stress intensity factor, in addition to the pre-determined size and shape of the material to be predicted, the loading method, and the load / displacement boundary conditions, it is also necessary to further obtain the initial crack size and fatigue small crack propagation mode, as well as the size and shape of the crack, through high-cycle fatigue testing.

[0059] In this embodiment, the dimensionless stress intensity factor is specifically calculated by: selecting the appropriate dimensionless stress intensity factor formula based on the influence of the finite size of the crack body, the recording method, and the load / displacement boundary composition, and then calculating the dimensionless stress intensity factor. It should be noted that different materials and different fatigue small crack propagation modes have their corresponding calculation formulas, which can be found in the "Stress Intensity Factor Handbook". By selecting the appropriate stress intensity factor calculation formula according to different fatigue small crack propagation modes, the stress intensity factor for the corresponding fatigue small crack propagation mode can be calculated.

[0060] Furthermore, the purpose of determining the dimensionless stress intensity factor in this application embodiment is that, since fatigue microcracks are typically three-dimensional microcracks, this application introduces a dimensionless stress intensity factor that is not used in fatigue long crack threshold prediction to further correct the threshold value of fatigue microcracks. The selection of the expression for this dimensionless stress intensity factor is related to the crack geometry, loading method, and composition of the load / displacement boundary; for details, please refer to the "Stress Intensity Factor Handbook".

[0061] S103: Based on fatigue limit, initial crack size and dimensionless stress intensity factor, predict the fatigue small crack threshold value of the material to be predicted according to the formula.

[0062] Traditional fatigue crack propagation curves contain a low-velocity propagation region with a vertical asymptote. The stress intensity factor value corresponding to this asymptote is called the fatigue crack propagation stress intensity factor threshold, or simply the fatigue crack threshold. Since most high-temperature alloys exhibit a fatigue small crack effect—that is, the propagation rate of small cracks is higher than that of long cracks, and the threshold value of small cracks is lower than that of long cracks—it is also called the fatigue small crack threshold. In the embodiments of this application, the fatigue small crack threshold is predicted using the determined fatigue limit, initial crack size, and dimensionless stress intensity factor.

[0063] In some implementations of this application, the fatigue small crack threshold value of the specimen is predicted using the following formula:

[0064]

[0065] Where, ΔK th Δσ represents the fatigue small crack threshold value. e Indicates the fatigue limit, a i denoted by , where f represents the initial crack size and f represents the dimensionless stress intensity factor.

[0066] exist Figure 1The illustrated process first involves conducting high-cycle fatigue tests on the test samples to obtain the fatigue limit, initial crack size, and fatigue small crack propagation mode. Then, the corresponding dimensionless stress intensity factor is determined based on the initial crack size and fatigue small crack propagation mode. Finally, the fatigue small crack threshold value is predicted based on the fatigue limit, initial crack size, and dimensionless stress intensity factor, thus achieving efficient and low-cost prediction of the fatigue small crack threshold value.

[0067] See Figure 2 As shown, this application embodiment further provides a method for predicting fatigue small crack threshold values. Figure 1 Based on the illustrated process, a further detailed description of its specific process may include the following steps:

[0068] S201: Conduct high-cycle fatigue tests on the material to be predicted to obtain stress-life data.

[0069] In the embodiments of this application, stress-life data refers to multiple stress-life data pairs statistically obtained during the high-cycle fatigue test of the specimen, wherein each stress-life data pair represents the fatigue life of the specimen under a certain stress condition.

[0070] S202: Fit the stress-life data to obtain the stress-life curve.

[0071] In the embodiments of this application, the stress-life curve refers to a curve used to reflect the stress-life relationship. The stress-life curve can be obtained by fitting stress-life data using standard methods, such as the American MMPDS standard method and the Chinese GJB / Z18A standard method. Among them, the three-parameter power function method is mainly selected for processing a single stress-life curve.

[0072] S203: In the stress-life curve, determine the fatigue strength corresponding to the preset life value as the fatigue limit.

[0073] In the embodiments of this application, the stress-life curve reflects different lifespans corresponding to different fatigue strengths, and each lifespan in the curve corresponds to a specific fatigue strength. The preset lifespan value refers to the number of cycles required to extend the material's service life, considering both material safety and economy. The preset lifespan value can be determined based on factors such as the material's operating environment and working conditions. In some implementations of this application, the preset lifespan value can be 10. 7 .

[0074] S204: Perform high-cycle fatigue tests on the material to be predicted to obtain the fatigue fracture morphology of the material to be predicted.

[0075] In the embodiments of this application, fatigue fracture morphology refers to the surface morphology of the fatigue fracture surface produced by the high-cycle fatigue test of the sample. The fatigue fracture morphology can be observed by high-magnification optical instruments such as electron microscopes or acoustic instruments such as ultrasonic probes.

[0076] S205: Determine the fatigue origin shape, fatigue origin size distribution, and fatigue small crack propagation mode of the material to be predicted based on the fatigue fracture morphology.

[0077] In the embodiments of this application, the fatigue source shape refers to the geometric shape of the initiation position of fatigue cracks in the sample material. The fatigue source size distribution refers to the size distribution of cracks at the fatigue source location in the sample material. The fatigue small crack propagation form is the fatigue crack manifestation form, such as surface cracks, corner cracks, elliptical or circular internal cracks, etc. At the same time, the fatigue small crack propagation form can also reflect the propagation law of crack length and depth. For example, when the fatigue small crack propagation form is a circular internal crack, the propagation amplitude of crack length and depth is similar.

[0078] This application utilizes instruments to observe and analyze the fatigue fracture morphology to determine the location of the fatigue origin in the specimen. Based on this location, the shape of the fatigue origin and its size distribution can be further determined. By observing the remaining cracks starting from the fatigue origin location, the propagation pattern of small fatigue cracks in the specimen can be clearly identified.

[0079] S206: Determine the initial crack size of the material to be predicted based on the shape and size distribution of the fatigue source.

[0080] Specifically, the initial crack size is determined based on the Murakami inclusion equivalent projected area model. This Murakami model can equate different fatigue source shapes to corresponding crack shapes. For example, if the fatigue source is a square inclusion, the initial crack can be equated to a circular crack; if the fatigue source is an elongated inclusion, the initial crack can be equated to an elliptical crack. Furthermore, depending on the actual shape of different fatigue sources, the initial crack can be equated to an elliptical crack with different major and minor axes. In addition to equating the initial crack to the corresponding fatigue crack shape, the Murakami model can also calculate the equivalent crack size using formulas. Therefore, the initial crack size refers to the size of the equivalent crack shape.

[0081] S207: Determine the dimensionless stress intensity factor by using the initial crack size and the fatigue small crack propagation mode.

[0082] In the embodiments of this application, the specific implementation of S207 is the same as that of S102, and will not be described in detail here.

[0083] S208: Based on fatigue limit, initial crack size, and dimensionless stress intensity factor, predict the fatigue small crack threshold value of the material to be predicted according to the formula.

[0084] In the embodiments of this application, the specific implementation of S208 is the same as that of S103, and will not be described in detail here.

[0085] exist Figure 2 The process described involves several steps. First, a high-cycle fatigue test is conducted on the material to be predicted to obtain its fatigue fracture morphology. Then, based on the fracture morphology, the shape of the fatigue origin, the size distribution of the fatigue origin, and the propagation mode of small fatigue cracks are determined. The initial crack size is then determined based on the shape and size distribution of the fatigue origin, thus obtaining the small fatigue crack propagation mode and the initial crack size. Next, a dimensionless stress intensity factor is obtained using the initial crack size and the small fatigue crack propagation mode. Finally, based on the fatigue limit, the initial crack size, and the dimensionless stress intensity factor, the fatigue small crack threshold value of the material is predicted using a formula. Overall, this application utilizes high-cycle fatigue testing, a more mature and cost-effective experimental technique and data processing method, to obtain the initial crack size and the small fatigue crack propagation mode of the material. Obtaining the fatigue limit through the stress-life curve has statistical significance. The fatigue small crack threshold value predicted by this method is more statistically significant and better characterizes the material properties compared to fatigue crack threshold values ​​obtained through single or multiple traditional tests. Furthermore, this application comprehensively considers the microstructure and the entire fatigue process of aerospace materials, and provides a simpler and more statistically significant method for predicting the fatigue small crack threshold value of the normal stress ratio of metallic materials.

[0086] The effectiveness of the fatigue small crack threshold prediction method provided in this application will be demonstrated below in the context of a practical application scenario.

[0087] Taking a GH4169 alloy single-sided notched tensile (SENT) specimen at room temperature as an example, with a specimen width of 12 mm, a specimen thickness of 3 mm, and a notch radius of 3 mm, the fatigue small crack threshold value of the GH4169 alloy SENT specimen can be predicted through the following steps:

[0088] Step 1: Obtain stress-life data of the specimen through high-cycle fatigue testing. Fit the test data according to standard methods to obtain the fatigue limit Δσ of the material. e The stress-life data (SN data) and curves of the GH4169 alloy SENT specimens at room temperature are shown in [reference needed]. Figure 3As shown, the data was processed using the three-parameter power function method recommended in standard GJB / Z18A-2020 "Data Processing and Expression of Mechanical Properties of Metallic Materials" to obtain the fitting formula for the stress-life curve. Based on this formula, the fatigue limit σe under two stress ratios was calculated. The fatigue life was 10 under the condition R = 0.1. 7 The corresponding fatigue strength σ e,max The pressure is 218 MPa, and 260 MPa under the condition of R = 0.5.

[0089] Step 2: Obtain the fatigue fracture morphology of the specimen through high-cycle fatigue testing. Observe and analyze the fatigue fracture morphology to determine the location of the fatigue initiation point and obtain information on its shape and size distribution. The initial crack size 'a' is obtained from the shape and size distribution of the fatigue initiation point. i The fatigue crack propagation morphology can be used to obtain the fatigue microcrack propagation pattern, which indicates the ratio between crack propagation length a and depth b. Based on the actual fatigue microcrack propagation pattern of the material, the stress intensity factor F can be calculated. I .

[0090] Specifically, the fatigue small crack propagation mode and fracture mechanism of the GH4169 alloy SENT specimens are described in [reference needed]. Figure 4 As shown, in Figure 4 In the diagram, the square at the bottom represents the fatigue origin. The fatigue crack propagation direction eventually extends into the fast propagation zone (Fsat crack growth zone), and continues to propagate to the final failure zone. Fatigue cracks originate from inherent defects in the material, with the fatigue origin located at the surface region of the notch root. From the perspective of fatigue striations, the fatigue crack propagates in an approximately semi-circular shape, meaning the length and depth of the crack are similar. Furthermore, to determine the crack shape, the test can be stopped at a certain lifespan, and the specimen can be stretched to break, observing the shape of the boundary between fatigue propagation and tensile stress at the fracture surface.

[0091] The fatigue fracture morphology of the specimens was observed, and the size of the fatigue initiation was statistically analyzed. Based on the equivalent area method of the Murakami model, the fatigue initiation was equivalent to a semi-circular crack, and the initial crack size was calculated. The initial fatigue crack size distribution of the GH4169 alloy SENT specimen is shown below. Figure 5 As shown, the initial crack size is distributed in the range of 5 to 20 μm. In this embodiment of the application, the median value is taken, that is, the initial crack size of the GH4169 alloy SENT sample is determined to be 8.5 μm.

[0092] Based on the fatigue fracture morphology and fatigue crack propagation mode, it can be seen that the fatigue crack is a semi-circular crack that starts at the root of the notch. According to the calculation formula of the dimensionless stress intensity factor of the SENT specimen given in the "Stress Intensity Factor Handbook", the dimensionless stress intensity factor f is calculated to be 3.56.

[0093] Step 3: For the GH4169 alloy SENT sample, under the condition of R = 0.1, σ e,max The pressure is 218 MPa; under the condition R = 0.5, σ e,max With a strength of 260 MPa and an initial crack size of 8.5 μm, the fatigue small crack threshold value of the SENT specimen was calculated using the prediction formula. The crack propagation threshold values ​​under the conditions of R = 0.1 and R = 0.5 were obtained as follows: and

[0094] To further verify the implementation effect, fatigue small crack tests were conducted under the same conditions in this application embodiment. The results are shown below. Figure 6 Experimental results show that the fatigue small crack threshold value R = 0.1 is approximately 3.15 MPa, and R = 0.5 is approximately 2.21 MPa. Comparing the calculated values ​​from the model with the experimental values, the error of the results is within a reasonable range. This proves that the method provided in this application can predict the fatigue small crack threshold value, and is simpler and less costly.

[0095] See Figure 7 As shown in the figure, this application provides a fatigue small crack threshold prediction device, which includes:

[0096] The fatigue test module 701 is used to perform high-cycle fatigue tests on the material to be predicted in order to obtain the fatigue limit, initial crack size and fatigue small crack propagation mode of the material to be predicted.

[0097] The parameter determination module 702 is used to determine the dimensionless stress intensity factor by means of the initial crack size and the fatigue small crack propagation mode.

[0098] The numerical prediction module 703 is used to predict the fatigue small crack threshold value of the material to be predicted based on the fatigue limit, initial crack size and dimensionless stress intensity factor.

[0099] In some implementations of the embodiments of this application, the fatigue testing module is specifically used for:

[0100] High-cycle fatigue tests were conducted on the material to be predicted in order to obtain stress-life data of the material to be predicted.

[0101] The stress-life curve is obtained by fitting the stress-life data;

[0102] In the stress-life curve, the fatigue strength corresponding to the preset life value is determined as the fatigue limit.

[0103] In some implementations of the embodiments of this application, the preset lifetime value is 10. 7 .

[0104] In some implementations of the embodiments of this application, the fatigue testing module is specifically used for:

[0105] High-cycle fatigue tests were conducted on the material to be predicted in order to obtain the fatigue fracture morphology of the material.

[0106] The fatigue origin shape, fatigue origin size distribution, and fatigue microcrack propagation mode of the material to be predicted are determined based on the fatigue fracture morphology.

[0107] The initial crack size of the material to be predicted is determined based on the shape and size distribution of the fatigue source.

[0108] In some implementations of the embodiments of this application, the initial crack size can also be obtained by performing non-destructive testing on the material to be predicted.

[0109] In some implementations of the embodiments of this application, and in some implementations of the first aspect of this application, the fatigue small crack threshold value of the material to be predicted is predicted by the following formula:

[0110]

[0111] Where, ΔK th Δσ represents the fatigue small crack threshold value. e Indicates the fatigue limit, a i denoted by , where f represents the initial crack size and f represents the dimensionless stress intensity factor.

[0112] like Figure 8 As shown in the figure, this application embodiment also provides a fatigue small crack threshold prediction device, including: a memory 801 and a processor 802;

[0113] Among them, memory 801 is used to store programs;

[0114] The processor 802 is used to execute a program in memory to implement the various steps of the method provided in the embodiments of this application.

[0115] This application also provides a readable storage medium storing a computer program thereon. When the computer program is executed by a processor, it implements the various steps of the fatigue small crack threshold prediction method provided in this application.

[0116] Finally, it should be noted that in the embodiments of this application, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0117] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for predicting the threshold value of fatigue small cracks, characterized in that, The method includes: High-cycle fatigue tests are performed on the material to be predicted in order to obtain the fatigue limit, initial crack size and fatigue small crack propagation mode of the material to be predicted. The dimensionless stress intensity factor is determined by the initial crack size and the fatigue small crack propagation mode. Based on the fatigue limit, the initial crack size, and the dimensionless stress intensity factor, the fatigue small crack threshold value of the material to be predicted is predicted according to the formula. The fatigue microcrack threshold value of the material to be predicted is predicted using the following formula: Among them, the Represents the fatigue small crack threshold value, the This represents the fatigue limit, the Indicates the initial crack size, the f This represents the dimensionless stress intensity factor.

2. The method according to claim 1, characterized in that, The high-cycle fatigue test on the material to be tested includes: The high-cycle fatigue test is performed on the material to be predicted to obtain stress-life data of the material to be predicted; The stress-life curve is obtained by fitting the stress-life data; In the stress-life curve, the fatigue strength corresponding to the preset life value is determined as the fatigue limit.

3. The method according to claim 2, characterized in that, The preset lifespan value is 10. 7 .

4. The method according to claim 1, characterized in that, The high-cycle fatigue test on the material to be tested includes: High-cycle fatigue tests were performed on the material to be predicted to obtain the fatigue fracture morphology of the material to be predicted. Based on the fatigue fracture morphology, the fatigue origin shape, fatigue origin size distribution, and fatigue microcrack propagation mode of the material to be predicted are determined. The initial crack size of the material to be predicted is determined based on the shape of the fatigue source and the size distribution of the fatigue source.

5. The method according to claim 1, characterized in that, The initial crack size can also be obtained by performing non-destructive testing on the material to be predicted.

6. A fatigue small crack threshold prediction device, characterized in that, The device includes: The fatigue testing module is used to perform high-cycle fatigue tests on the material to be predicted in order to obtain the fatigue limit, initial crack size and fatigue small crack propagation mode of the material to be predicted. The parameter determination module is used to determine the dimensionless stress intensity factor based on the initial crack size and the fatigue small crack propagation mode. The numerical prediction module is used to predict the fatigue small crack threshold value of the material to be predicted based on the fatigue limit, the initial crack size, and the dimensionless stress intensity factor, according to a formula. The fatigue microcrack threshold value of the material to be predicted is predicted using the following formula: Among them, the Represents the fatigue small crack threshold value, the This represents the fatigue limit, the Indicates the initial crack size, the f This represents the dimensionless stress intensity factor.

7. The apparatus according to claim 6, characterized in that, The fatigue testing module is specifically used for: The high-cycle fatigue test is performed on the material to be predicted to obtain stress-life data of the material to be predicted; The stress-life curve is obtained by fitting the stress-life data; In the stress-life curve, the fatigue strength corresponding to the preset life value is determined as the fatigue limit.

8. A fatigue small crack threshold prediction device, characterized in that, The device includes a memory and a processor, the processor being configured to execute a program stored in the memory to run the fatigue small crack threshold prediction method as described in any one of claims 1 to 5.

9. A readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements each step of the fatigue small crack threshold prediction method as described in any one of claims 1 to 5.

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