High-temperature fatigue life prediction method based on EIFS

Abstract

The invention provides a high-temperature fatigue life prediction method based on EIFS, and relates to the technical field of reliability design. The method comprises the following steps: acquiring first test data for performing a crack propagation test and a high-cycle fatigue test on a smooth component, and second test data for performing a test on a notched component; according to the first test data and the second test data, the equivalent initial defect size of the smooth component and the equivalent initial defect size of the notched component are determined; according to the second test data, the equivalent stress strength factor difference value and the fatigue crack propagation rate of the notched component under the high-temperature condition are obtained; fitting a function relationship among the fatigue crack propagation rate, the equivalent stress strength factor difference value and the crack size to obtain a crack propagation function; and based on the crack propagation function and the equivalent initial defect size and the limit crack size of the notched component, the predicted fatigue life of the notched component under the high-temperature condition is determined. According to the invention, accurate high-temperature fatigue life prediction can be realized.

Description

Technical Field

[0001] The present disclosure relates to the technical field of reliability design, and in particular to a method, device, and electronic equipment for predicting high-temperature fatigue life based on EIFS. Background Art

[0002] In reliability and durability design, it is usually necessary to predict the fatigue life of mechanical components on aircraft, automobiles, and ships, so as to formulate reasonable maintenance and replacement cycles or service life and eliminate safety hazards.

[0003] When a crack initiates on a component, the driving force for crack propagation is different under different environments. Among them, the driving force for crack propagation under high temperature environment is more complex than that under normal temperature environment. For example, oxidation inside the structural organization under high temperature environment has a greater impact on crack propagation. The fatigue life prediction method for normal temperature is not suitable for high temperature fatigue life prediction. Therefore, it is difficult for related technologies to achieve accurate high temperature fatigue life prediction. Summary of the invention

[0004] The present disclosure provides a high temperature fatigue life prediction method, device, and electronic device based on EIFS, so as to improve the accuracy of high temperature fatigue life prediction at least to a certain extent.

[0005] According to a first aspect of the present disclosure, a high-temperature fatigue life prediction method based on EIFS is provided, comprising: obtaining first test data of crack growth test and high-cycle fatigue test on a smooth component, and second test data of crack growth test and high-cycle fatigue test on a notched component; the second test data comprises test data under high-temperature conditions; according to the first test data and the second test data, determining the equivalent initial defect size of the smooth component and the equivalent initial defect size of the notched component; according to the second test data, obtaining the difference in equivalent stress intensity factor and fatigue crack growth rate of the notched component under high-temperature conditions; The equivalent stress intensity factor difference is the difference between the effective value of the equivalent stress intensity factor and the threshold value of the equivalent stress intensity factor that comprehensively considers various types of crack extension driving forces in the notched component; the crack extension function is obtained by fitting the functional relationship between the fatigue crack extension rate, the equivalent stress intensity factor difference, and the crack size of the notched component under high temperature conditions; the crack extension function represents the functional relationship between the fatigue crack extension rate and the crack size; based on the crack extension function, the equivalent initial defect size and the limit crack size of the notched component, the predicted fatigue life of the notched component under high temperature conditions is determined.

[0006] According to a second aspect of the present disclosure, a high-temperature fatigue life prediction device based on EIFS is provided, comprising: a test data acquisition module, configured to acquire first test data of a crack extension test and a high-cycle fatigue test on a smooth component, and second test data of a crack extension test and a high-cycle fatigue test on a notched component; the second test data includes test data under high temperature conditions; a first determination module, configured to determine the equivalent initial defect size of the smooth component and the equivalent initial defect size of the notched component according to the first test data and the second test data; a second determination module, configured to obtain the equivalent stress intensity factor difference and fatigue stress intensity factor of the notched component under high temperature conditions according to the second test data. crack growth rate; the equivalent stress intensity factor difference is the difference between the effective value of the equivalent stress intensity factor and the threshold value of the equivalent stress intensity factor that comprehensively considers various types of crack growth driving forces in the notched component; a third determination module is configured to obtain a crack growth function by fitting the functional relationship between the fatigue crack growth rate, the equivalent stress intensity factor difference, and the crack size of the notched component under high temperature conditions; the crack growth function represents the functional relationship between the fatigue crack growth rate and the crack size; a fourth determination module is configured to determine the predicted fatigue life of the notched component under high temperature conditions based on the crack growth function, the equivalent initial defect size and the limit crack size of the notched component.

[0007] According to a third aspect of the present disclosure, a computer program product is provided, including a computer program, wherein when the computer program is executed by a processor, the method of the first aspect and possible implementations thereof are implemented.

[0008] According to a fourth aspect of the present disclosure, an electronic device is provided, comprising: a processor; and a memory for storing executable instructions of the processor; wherein the processor is configured to execute the method of the above-mentioned first aspect and its possible implementation methods by executing the executable instructions.

[0009] The technical solution disclosed in this disclosure has the following beneficial effects:

[0010] A method for predicting the fatigue life of components under high temperature conditions is provided. On the basis of determining the EIFS, the effects of various types of crack propagation driving forces in the component are considered, and the full cycle of crack propagation from the EIFS to the limit crack size is predicted. The accuracy is high and less test data is required. In particular, this scheme is suitable for notched components containing air film pore structures, and can predict the high temperature fatigue life of notched components based on different pore making processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1A flowchart of a high temperature fatigue life prediction method based on EIFS in this exemplary embodiment is shown.

[0012] Figure 2 A schematic diagram showing a method of preparing a notched member and a smooth member according to this exemplary embodiment.

[0013] Figure 3 A schematic diagram showing the relationship between fatigue strength and fracture mechanics in this exemplary embodiment is shown.

[0014] Figure 4A ΔK of the notched component based on the EDM process in this exemplary embodiment is shown th,l Distribution map.

[0015] Figure 4B ΔK of the notched member based on the LDM process in this exemplary embodiment is shown th,l Distribution map.

[0016] Figure 5 The ΔK of the notched component based on different hole making processes in this exemplary embodiment is shown. th,l and survival rate.

[0017] Figure 6 The fatigue limit diagrams of the smooth component and the notched component based on the two hole making processes of EDM and LDM in this exemplary embodiment are shown.

[0018] Figure 7 A straight line fitting graph of the survival rate and the fatigue limit in this exemplary embodiment is shown.

[0019] Figure 8 A diagram showing the fracture morphology of a smooth member in this exemplary embodiment is shown.

[0020] Fig. 9 A schematic diagram showing a fatigue source region ellipse and an equivalent circle in this exemplary embodiment.

[0021] Fig.10 A relationship diagram is shown between the major-minor axis ratio of the fatigue source region ellipse and the ratio of the stress intensity factor K of cracks of different geometric forms in this exemplary embodiment.

[0022] Fig.11 A graph of crack growth in this exemplary embodiment is shown.

[0023] Fig. 12A The EIFS values ​​at different survival rates in this exemplary embodiment are shown.

[0024] Fig. 12B The linear description of the notched component based on the EDM process in this exemplary embodiment at different survival rates and crack geometry correction factors is shown.

[0025] Fig. 12C The linear description of the notched component based on the LDM process in this exemplary embodiment at different survival rates and crack geometry correction factors is shown.

[0026] Fig.13A A schematic diagram showing a component geometric coordinate system and a crack random propagation surface in this exemplary embodiment.

[0027] Fig. 13B A schematic diagram showing the crack tip local coordinate system in this exemplary embodiment.

[0028] Fig. 13C A schematic diagram showing a crystal slip plane in this exemplary embodiment.

[0029] Fig.14 A schematic diagram showing COD in this exemplary embodiment.

[0030] Fig.15 A schematic diagram showing the probability distribution of parameters such as the intrinsic crack extension threshold value and the long crack extension threshold value in this exemplary embodiment.

[0031] Fig.16 A schematic diagram showing the method of fitting a crack growth curve using a power function in this exemplary embodiment is shown.

[0032] Fig.17A A schematic diagram showing a dislocation slip plane in this exemplary embodiment.

[0033] Fig. 17B A schematic diagram showing a plastic zone in this exemplary embodiment.

[0034] Fig. 17C A schematic diagram showing a crack initiation region in this exemplary embodiment.

[0035] Fig.17D and Fig.17E The strain measurement results of the notched component based on the EDM and LDM hole making processes in this exemplary embodiment are respectively shown.

[0036] Fig.18 A schematic diagram showing elastic moduli of members in this exemplary embodiment is shown.

[0037] Fig.19 Schematic diagram showing crack morphology and elemental analysis in this exemplary embodiment.

[0038] Fig. 20A A fitting schematic diagram showing the first functional relationship in this exemplary embodiment.

[0039] Fig. 20B A fitting schematic diagram showing the second functional relationship in this exemplary embodiment is shown.

[0040] Fig.21 The results of predicting fatigue life in this exemplary embodiment are shown.

[0041] Fig. 22 A schematic structural diagram of a high temperature fatigue life prediction device based on EIFS in this exemplary embodiment is shown.

[0042] Fig.23 A schematic structural diagram of an electronic device in this exemplary embodiment is shown. DETAILED DESCRIPTION

[0043] Exemplary embodiments of the present disclosure will be described more fully hereinafter with reference to the accompanying drawings.

[0044] The accompanying drawings are schematic illustrations of the present disclosure and are not necessarily drawn to scale. Some of the block diagrams shown in the accompanying drawings may be functional entities and do not necessarily correspond to physically or logically independent entities. The embodiments can be implemented in various forms and should not be construed as being limited to the examples set forth herein. The features, structures, or characteristics described in the present disclosure may be combined in one or more embodiments in any suitable manner. In the description below, many specific details are provided to provide a full description of the embodiments of the present disclosure. However, those skilled in the art should appreciate that one or more specific details may be omitted when implementing the technical solution of the present disclosure, or other materials, methods, components, devices, steps, etc. may be used to replace one or more specific details.

[0045] The exemplary embodiment of the present disclosure provides a high-temperature fatigue life prediction method based on EIFS. EIFS (Equivalent Initial Flaw Size) is a hypothetical crack size, assuming that the hypothetical crack exists in the structural details before being put into use. The EIFS distribution has the following characteristics: the EIFS distribution depends only on material properties, processing technology and assembly status, and does not depend on the use conditions (such as spectrum or stress level). The data under different use conditions can be inferred to be the same EIFS distribution (i.e., "universal EIFS distribution"); the EIFS distribution is not a real physical defect or crack distribution in the original material, but a mathematical representative of the original fatigue quality. After a certain period of hypothetical crack expansion from the EIFS distribution, it is consistent with the real crack expansion.

[0046] Figure 1 An exemplary process of a high temperature fatigue life prediction method based on EIFS is shown, which may include the following steps S110 to S150:

[0047] Step S110, obtaining first test data of crack growth test and high cycle fatigue test on smooth components, and second test data of crack growth test and high cycle fatigue test on notched components; the second test data includes test data under high temperature conditions.

[0048] Step S120, determining an equivalent initial defect size of a smooth component and an equivalent initial defect size of a notched component according to the first test data and the second test data;

[0049] Step S130, obtaining the equivalent stress intensity factor difference and fatigue crack growth rate of the notched component under high temperature conditions according to the second test data; the equivalent stress intensity factor difference is the difference between the equivalent stress intensity factor effective value and the equivalent stress intensity factor threshold value that comprehensively considers various types of crack growth driving forces in the notched component;

[0050] Step S140, obtaining a crack growth function by fitting the functional relationship between the fatigue crack growth rate, the difference in equivalent stress intensity factor, and the crack size of the notched component under high temperature conditions; the crack growth function represents the functional relationship between the fatigue crack growth rate and the crack size;

[0051] Step S150, predicting the fatigue life of the notched component under high temperature conditions based on the crack growth function, the equivalent initial defect size and the limit crack size of the notched component.

[0052] based on Figure 1 The method shown provides a method for predicting the fatigue life of components under high temperature conditions. On the basis of determining the EIFS, the effects of various types of crack propagation driving forces in the component are considered, and the full cycle of crack propagation from the EIFS to the limit crack size is predicted. The accuracy is high and less test data is required. In particular, this scheme is suitable for notched components containing air film pore structures, etc., and can predict the high temperature fatigue life of notched components based on different pore making processes.

[0053] Below Figure 1 Provide detailed instructions for each step.

[0054] In step S110, first test data of crack growth test and high cycle fatigue test on smooth component and second test data of crack growth test and high cycle fatigue test on notched component are obtained; the second test data includes test data under high temperature conditions.

[0055] Among them, the notch refers to a discontinuous area on the outer surface of a component, such as a hole. There is a notch on the outer surface of the notched component, such as a component that simulates the air film hole structure of an aviation turbine blade, and the notch is an air film hole. Due to the structural mutation of the notch part, stress concentration is easily caused, which affects the original fatigue quality of the component. Correspondingly, the smooth component is a component without a notch. In this exemplary embodiment, the notched component and the smooth component are made of the same material and have the same or similar profile and size. For example, the notched component and the smooth component are made of the same metal or alloy material, are both rectangular in shape, and have the same length, width, and height. The difference is that there is an opening (i.e., a notch) on the outer surface of the notched component, and the outer surface of the smooth component is smooth and complete. This makes it easy to compare the test results of the notched component with the smooth component to calculate the notch effect. The notch obtained in the notched component can be prepared based on different hole making processes, such as EDM (electric spark) process, LDM (laser) process, etc.

[0056] Figure 2 The schematic diagram of preparing the test component is shown. my country's second-generation nickel-based single crystal high-temperature alloy DD6 is used as the component material. After the unprocessed blank material is subjected to standard heat treatment, two forms of flat plate parts are respectively prepared to ensure equal orientation at one time, including pure rectangular flat plate and dog-bone flat plate, so that as many test components as possible can be prepared on the same limited size blank material. Flat plate parts without openings are prepared as smooth components, and flat plate parts with openings (such as simulated air film holes) are prepared as notched components. The hole making process can adopt EDM and LDM. For example, the thickness of the rectangular flat plate can be designed to be 0.8mm, the diameter of the air film hole can be 0.8mm, the thickness of the dog-bone flat plate can be designed to be 1.0mm, and the diameter of the air film hole can be 0.5mm.

[0057] Crack extension test refers to applying cyclic stress to component specimens to observe crack extension. The difference between high cycle fatigue test and crack extension test is the number of cyclic stresses applied. The number of cyclic stresses in crack extension test is usually 10. 5 The number of cycles of high cycle fatigue test is usually 10 7 Table 1 shows the conditions of crack growth test and high cycle fatigue test. For example, three kinds of specimens can be prepared. Plate 1 is a rectangular plate specimen with holes, including rectangular plate specimens with EDM holes and rectangular plate specimens with LDM holes. Plate 2 is a dog-bone-shaped plate specimen with holes, using LDM hole making process. Plate 3 is a smooth dog-bone-shaped plate specimen. maxRepresents stress amplitude, that is, the maximum stress in cyclic loading. For notched components, a cyclic stress with a stress amplitude of 160-240MPa is applied at room temperature, with a frequency of 78Hz. High temperature conditions are 900℃ and 980℃, with stress amplitudes of 580MPa and 550MPa respectively applied at a frequency of 5Hz. For smooth components, a cyclic stress with a stress amplitude of 350-450MPa is applied at room temperature, with a frequency of 78Hz. A stress ratio of 0.1 is used under all conditions, that is, the ratio of the minimum stress to the maximum stress of cyclic loading is 0.1. For each test condition, multiple valid specimens can be set to repeat the test to ensure the stability and accuracy of the test results.

[0058] Table 1

[0059]

[0060]

[0061] During the test, the crack extension of the component loaded with cyclic stress is detected, and the test data is recorded. Among them, the test data for the smooth component (such as plate 3) is the first test data, which may include the test data under normal temperature conditions. The test data for the notched component (such as plate 1 and plate 2) is the second test data, which may include the test data under high temperature conditions and the test data under normal temperature conditions.

[0062] Continue to refer Figure 1 In step S120, the equivalent initial defect size of the smooth component and the equivalent initial defect size of the notched component are determined according to the first test data and the second test data.

[0063] In one embodiment, the determining of the equivalent initial defect size of the smooth component and the equivalent initial defect size of the notched component based on the first test data and the second test data may include the following steps:

[0064] According to the first test data and the second test data, the long crack extension threshold value of the notched component, the long crack extension threshold value of the smooth component, the fatigue limit, and the fatigue source zone ellipse geometric parameters are obtained;

[0065] According to the long crack extension threshold value and fatigue limit of the smooth component, the equivalent initial defect size of the smooth component is determined;

[0066] According to the geometric parameters of the fatigue source area ellipse of the smooth component, the equivalent circle parameters of the fatigue source area are determined;

[0067] The fatigue notch factor of the notched component is determined according to the equivalent circle parameters of the fatigue source area, the geometric parameters of the ellipse of the fatigue source area, and the equivalent initial defect size of the smooth component;

[0068] The equivalent initial defect size of the notched component is determined according to the long crack growth threshold value of the notched component, the geometric shape factor, the fatigue notch factor and the equivalent initial defect size of the smooth component.

[0069] Among them, the nucleation and expansion of cracks can generally be described according to the Griffith condition. The elastic relationship between the crack size a (generally refers to the crack length, that is, the size of the crack along its expansion direction) and the required stress σ can be referred to the following formula:

[0070]

[0071] E represents elastic modulus (MPa); q represents surface energy (J·m -2 ).

[0072] The stress intensity factor is a physical quantity that reflects the strength of the elastic stress field at the crack tip, and its unit is MPa·m 1 / 2 The crack extension threshold refers to the stress intensity factor alternating value at which a cracked component will not undergo fatigue extension under alternating loads, expressed as ΔK. th In this exemplary embodiment, two crack extension thresholds are considered, namely, the intrinsic crack extension threshold and the crack extension threshold. th,eff denoted by ΔK, and the long crack extension threshold th,l express.

[0073] Assuming there is a critical crack a 0 , so that the actual crack size a 0 When a>a 0 When , the crack extension threshold is independent of the crack size. 0 Generally, it refers to the stage of small crack extension. The stress state at this time is difficult to be fully described by linear elasticity. For simplicity, the fatigue limit of different crack sizes can be described linearly, referring to the following formula:

[0074]

[0075] Based on the interpretation model of the KT diagram (Kitagawa-Takahashi diagram) of linear elastic fracture mechanics, it is proposed that the 0,l For the transition crack size, it reflects the phenomenon that the fatigue limit increases as the crack decreases. Refer to the following formula:

[0076]

[0077] Among them, ΔK th,l Indicates the long crack extension threshold (MPa·m 0.5 );Δσ​​e represents fatigue limit (MPa); Y represents crack geometry correction factor.

[0078] When the crack size a is significantly smaller, Δσ th =Δσ e , Y = 1. At the same time, a 0,l It can be regarded as the critical value for continuous crack extension. The following relationship exists:

[0079]

[0080] Based on this, since the material cannot withstand high stress, local plastic damage occurs under repeated fatigue loads, and strain gradients are generated by dislocation accumulation, slip bands, intrusion and extrusion, resulting in local stress concentration and internal stress. This explains why when the crack (or equivalent defect) size is smaller than a 0,l , and the nominal stress is greater than Δσ e Obviously, the crack extension threshold value requires the condition in this area (crack size is less than a 0,l , and the nominal stress is greater than Δσ e Therefore, there may be another ratio ΔK in the small crack growth stage. th,l A smaller threshold, namely the intrinsic crack extension threshold ΔK th,eff .

[0081] Figure 3 The relationship between fatigue strength and fracture mechanics is described through multiple related curve graphs. Figure 3 The da / dN-ΔK curve in the figure describes the expansion of the long crack stage, and moves it forward in the direction of the short crack. Based on the changes in mechanical behavior at different crack extension stages, the crack extension successively goes through three stages: microstructural short crack, mechanical short crack and long crack, as shown in the three stages of the KT diagram. In stage I, the crack size is limited to a microscale, and the crack size is generally arranged in the order of microstructural characteristics such as grain size. Within this scale range, the microstructure becomes the dominant force in crack extension, and the corresponding crack driving force (or crack driving load) can be described by microstructural fracture mechanics. When the microstructure is not sufficient to inhibit crack extension, such as when the crack exceeds 1-2 grain sizes (as shown in stage II in the KT diagram), the crack extension is dominated by the surrounding grains, and the plastic zone size is too large, so most small cracks cannot be ignored. When the crack size is less than a 0,l When ΔK of linear elastic fracture mechanics is not applicable th,l concept.

[0082] The microstructural mechanism has an important influence on the fatigue crack growth of high temperature alloys. In the case of relatively small defects, it is necessary to consider the shorter fatigue crack growth. In addition to the influence of the plastic zone and the crack tip microstructure, the biggest difference between long cracks and short cracks is the influence of the closure effect. When solving the EIFS value using fracture mechanics methods, the small crack plastic zone is involved, and the solution of the true stress intensity factor requires correction of the crack size. Figure 3 It can be seen from the cyclic R curve that if a short microstructural crack is to expand, it must overcome the inherent crack extension threshold of the material and structure, that is, the intrinsic crack extension threshold ΔK th,eff , can enter stage II. In polycrystalline materials, a 0,l It can be regarded as a characteristic size and the boundary point of long and short cracks, but this value is not conservative. Cracks must first resist the influence of microstructure, such as grain boundaries. At the same time, this is also the dividing point between macro cracks and micro cracks. For nickel-based single crystal materials (without grains), the characteristic size cannot be expressed by grain size. Under the action of internal stress, cracks smaller than the limit crack size can still be 10 7 If the limit crack size can be overcome, a 0 To describe EIFS, in order to solve the problem of initial damage evaluation of different hole making. When the crack size is small, the plastic zone is easier to form. Generally speaking, under the same stress intensity factor, the plastic zone of a short crack is about 8 times that of a long crack, and may even be equivalent to the size of a short crack. It can be seen that the plastic zone plays an important role in the stress field of the elastic zone. The intrinsic crack extension threshold value and the long crack crack extension threshold value are introduced at the two dividing points of the entire crack, corresponding to the crack extension resistance curve (R curve). According to the different stress fields, a 0 point as the limit state of the elastoplastic description.

[0083] Long crack extension threshold ΔK th,l Can be used as a material parameter, ΔK at room temperature th,l Can be used to calculate EIFS for smooth members.

[0084] Figure 4A The ΔK of the notched component based on the EDM process is shown eq -da / dN curve, Figure 4B The ΔK of the notched component based on the LDM process is shown eq -da / dN curve. The horizontal axis in the figure is the equivalent stress intensity factor ΔK eq (MPa·m 0.5 ), which can be obtained by the stress (such as stress amplitude σ max) and the size of the notched component, the ordinate is the fatigue crack growth rate da / dN (mm / cycle), that is, the crack growth length of each cycle of loading stress. The second test data can include the fatigue crack growth rate corresponding to different equivalent stress intensity factors, that is, Figure 4A or Figure 4B The figure shows the data of each valid sample tested at different stress amplitudes under normal temperature conditions, such as "180-1" represents the data of valid sample 1 tested at a stress amplitude of 180 MPa. The figure also shows the fitting zone and fitting curve based on the survival rate (Ps). The fitting curve is an exponential fitting curve with an error band of 30% and a survival rate of 50%.

[0085] In order to establish a probability-based statistical model, the second test data with fatigue crack growth rate within a preset value range can be fitted. The preset value range can be determined according to specific needs, and can be a relatively ideal value range for fatigue crack growth rate, such as 10 -7 -10 -6 mm / cycle. For example, the fatigue crack growth rate is 10 -7 -10 -6 The second test data within mm / cycle were fitted to obtain the long crack extension threshold values ​​of notched components based on EDM process and LDM process respectively. Figure 4A The ΔK of the notched component based on the EDM process is shown th,l Distribution map. Figure 4B The ΔK of the notched component based on the LDM process is shown th,l Distribution map.

[0086] Refer to the above Figure 4A or Figure 4B As shown in the figure, based on the second test data under normal temperature, different equivalent stress intensity factors ΔK under normal temperature are obtained. eq The corresponding fatigue crack growth rate da / dN. The second test data with fatigue crack growth rate within the preset value range is selected for fitting, and the long crack growth threshold value ΔK of the notched component under different survival rates at room temperature is obtained. th,l , ΔK of notched components based on different hole making processes th,l The curve of survival rate can be referred to Figure 5 shown.

[0087] In order to make full use of the data, the crack growth data of notched components under normal temperature conditions are used to calculate the long crack growth threshold value of smooth components, which can simplify the test process. Due to the dispersion of the test results and the size of the hole edge influence zone, the long crack growth threshold value under a higher survival rate (such as 99.9%) is generally selected as the long crack growth threshold value of the smooth component. For example, the ΔK obtained under different survival rates th，l Satisfies the three-parameter Weibull (Weibull 3P) probability distribution, refer to the following formula:

[0088]

[0089] Among them, P represents the survival rate (i.e., probability), α, β, and γ are the parameters of the three-parameter Weibull probability distribution, and the values ​​of α, β, and γ can be obtained by minimum variance fitting, as shown in Table 2. As mentioned above, the long crack extension threshold value ΔK of the smooth component under normal temperature conditions can be obtained at a survival rate of 99% th,l,smooth About 1.93MPa·m 0.5 .

[0090] Table 2

[0091]

[0092] In one embodiment, a smooth component can be tested at room temperature, and the first test data can be fitted to obtain the long crack extension threshold value ΔK of the smooth component. th,l .

[0093] The fatigue limit is described below.

[0094] The EIFS value of components with gaps (such as air film holes) is 0,l Small enough to ensure structural safety, assuming smooth components After transformation, the safe EIFS can be obtained as The corresponding safety fatigue limit is solved as follows:

[0095]

[0096] The above formula can be further rewritten as:

[0097] Δσ 0 =A·a m (7)

[0098] Where A is a constant closely related to the material. Taking the logarithm of equations (6) and (7) and taking the derivative of lna, we get:

[0099]

[0100] Furthermore, the following relationship can be obtained:

[0101]

[0102] when a=a 0 hour, To determine the fatigue limit actually corresponding to the crack size, equation (6) can be rewritten as:

[0103]

[0104] Through a large number of test results, we can get the value of m to be -1 / 3 or -1 / 6.

[0105] The geometric parameters of the fatigue source area ellipse are explained below.

[0106] In the early stage of hole making, the early extension of microcracks is strongly affected by the crack-free microstructure of the material. The survival rate can be introduced to obtain the PSN (survival rate-stress amplitude-life) curve, which can better reflect the data discreteness compared to the SN curve. In order to remove the interference of factors such as the original material processing factors and the geometric dimensions of the components, the fatigue limit test of the smooth component under normal temperature conditions was carried out using the lifting method to obtain the fatigue limit of the smooth component.

[0107] Figure 6 The fatigue limit diagrams of smooth components and notched components based on EDM and LDM hole making processes are shown. The solid line in the middle of the figure is the fatigue limit fitting line of the notched component based on the EDM process at different survival rates, from bottom to top, they are the fatigue limits at three survival rates of 99.99%, 50%, and 0.01%. The dotted line in the middle of the figure is the fatigue limit fitting line of the notched component based on the LDM process at different survival rates, from bottom to top, they are the fatigue limits at three survival rates of 99.99%, 50%, and 0.01%. Reference Figure 6 As shown, at 50% survival rate, the Δσ of the smooth member e is 377.6MPa (L s horizontal line), under the same test environment, the fatigue limits of notched components based on EDM and LDM processes at 99.99% survival rate and 95% confidence level are 55.113MPa and 47.0MPa respectively; while at 50% survival rate and 95% confidence level, the Δσ of notched components based on the two processes is e 59.2MPa and 47.6MPa respectively (L e and L l horizontal line). Assuming that the fatigue life at the same stress level satisfies the normal distribution, considering five survival rates of 0.01%, 20%, 50%, 80% and 99.99%, the relationship between the survival rate and the fatigue limit is obtained by linear fitting, which can be referred to Figure 7 It can be seen that the survival rate and fatigue limit roughly satisfy the linear relationship, and the fitting curves are y=65.235-10.523x and y=51.368-5.062x, respectively, and the range of EDM is greater than that of LDM.

[0108] Based on the linear expression of stress intensity factor, for any object with a surface crack of size a, the uniaxial remote tensile stress σ perpendicular to the crack plane is ∞ The stress intensity factor can be written as F is the geometric correction factor of the actual specimen. For cracks in the notch stress field, the stress intensity solution is asymptotically the same as that of surface cracks in smooth solids, except that the distal stress is modulated by the stress concentration factor K. t =σ max / σ ∞ is amplified. Therefore, when a→0, there is the following relationship:

[0109]

[0110] Among them, F 0 Represents the geometric factor of cracks on the surface of smooth components. For cracks located in the notch stress field, the asymptotic solution of the geometric factor F is:

[0111] F=F 0 K t (12)

[0112] When the crack extends beyond the notch stress field, the stress intensity factor dominated by the far-end stress field can be expressed by formula (13):

[0113]

[0114] Where d is the notch depth. The following formula (14) can be further obtained:

[0115]

[0116] Where F ∞ is the reference geometric factor. When d / a<<1, F can asymptotically approach a constant, i.e., F=F 0 At this time, the upper and lower bounds of the geometric factor F are F 0 , F 0 K t Using these asymptotic solutions, a simple formula for the geometric factor F caused by the notch root can be established for any size.

[0117] For the through crack at the root of the notch, the geometric factor F is limited by the upper and lower asymptotes, so that 1 <F / F 0 <K t . The geometric factor F can be written as:

[0118]

[0119] Where D is the “equivalent” surface crack depth, which can be determined by the following formula:

[0120]

[0121] in,

[0122] The general formula for the asymptotic solution of the stress intensity factor can be expressed as:

[0123]

[0124] It should be noted that after the notch is introduced, the fatigue limit of smooth components and notched components can no longer be simply calculated based on K t calculation, because the "similarity" of the surface of the highly stressed material cannot be satisfied. The fatigue notch factor is defined as K f , that is, the effective stress concentration factor, the specific expression is:

[0125]

[0126] Among them, σ smooth,e represents the fatigue limit of smooth components, σ notch,e Represents the fatigue limit of a notched component.

[0127] In order to consider the fatigue notch effect, the smooth component is assumed to have a semicircular micro-notch with a length of the same order of magnitude as the EIFS. The following is a detailed discussion of the fatigue notch factor using the asymptotic stress intensity factor solution and the ElFS model. Considering the asymptotic solution of the notch crack, when the applied stress intensity factor is equal to the stress intensity factor threshold, the smooth component reaches the fatigue limit σ smooth,e , introducing the finite geometry correction factor, the following relationship exists:

[0128]

[0129] Where a represents the conservative EIFS crack size for smooth components (mm); d r Indicates the equivalent size of micro-defects in the fatigue source area of ​​smooth components (mm); α 0 The geometric correction factor representing the crack size a+d in a finite-size component can be obtained through the fracture mechanics handbook or finite element calculation.

[0130] Similarly, the fatigue limit σ of a notched component is notch，e and stress intensity factor threshold value K th，notch With the following connections:

[0131]

[0132] Where, d n Indicates the actual gap size.

[0133] Combining equations (18) to (20), we can obtain:

[0134]

[0135] It should be understood that the EIFS is usually several orders of magnitude smaller than the specimen size (e.g., micrometers versus millimeters or higher), and equation (21) can be simplified to:

[0136]

[0137] when When the equivalent size of micro-defect is much larger than EIFS, K f =1, then the notch effect can be ignored; when That is, the equivalent size of micro defects is much smaller than EIFS, K f =K t .

[0138] The geometric parameters of the fatigue source area ellipse are explained below.

[0139] Figure 8 The fracture morphology of a smooth component is shown. It can be seen that the overall fracture presents three clear fracture ranges: the fatigue source area where the geometric size changes suddenly, the crack extension area (with obvious fatigue lines) and the instantaneous tensile fracture area (protruding ductile fracture surface). The fatigue source area can be approximated as an ellipse or semi-ellipse (such as Figure 8 The fatigue source area is approximated as a semi-ellipse in the method, and the geometric parameters of the fatigue source area ellipse are obtained by measuring the geometric dimensions of the fatigue source area. The geometric parameters of the fatigue source area ellipse may include the length of the major semi-axis and the minor semi-axis of the fatigue source area ellipse, the ratio of the major axis to the minor axis, etc.

[0140] The inclusion area (or micro-defect) of the fatigue source zone can be approximated as an ellipse or a semi-ellipse, that is, the actual "EIFS" is in a two-dimensional state. The ellipse or semi-ellipse can be approximately converted into an equivalent circle, and the parameters of the equivalent circle can be determined to achieve EIFS "equivalence".

[0141] In one embodiment, the fatigue source area ellipse geometric parameters include: the length of the major semi-axis and the minor semi-axis when the fatigue source area is approximated as an ellipse or a semi-ellipse; the fatigue source area equivalent circle parameters include: the equivalent circle radius.

[0142] refer to Fig. 9 As shown in Figure 1, an elliptical crack with a minor semi-axis a and a major semi-axis c is embedded in an infinite solid and subjected to a uniform tension σ perpendicular to the fatigue source plane (xz plane). The geometric correction factor for a crack size of a+d is F(α0 ), according to the Stress Intensity Factor Handbook, the stress intensity factor of a semi-elliptical crack can be:

[0143]

[0144] The above formula can be simplified as:

[0145]

[0146] According to the equal area formula, α 0 It can be expressed as (a / r) 2 , then the ratio of the stress intensity factors of the two geometric forms of ellipse and equivalent circle is:

[0147]

[0148] refer to Fig.10 As shown in the figure, the stress intensity factors K of cracks with different geometric forms are compared. The results show that the maximum ratio between the two is about 1.091. 0 =0.489; at the same time, α 0 When the change range is between 0.2 and 1, K 椭 / K 圆 The ratio value changes within 9.1%. 0 The actual value can be determined by 圆 and the crack radius r (i.e., equivalent circle radius) after crack size reduction, and regard it as d r .

[0149] For notched components, the original KT diagram obtained using smooth components cannot describe the crack initiation and propagation behavior, because the initiation and propagation of cracks are not only affected by the defects of the material itself, but also by the stress concentration of geometric dimensions. Fig.11 As shown, the inherent defects of the material are regarded as a 0,l , when there is a sharp central crack, a 0,l It can reflect the crack initiation behavior of the component. Under the effect of the notch, without considering the fatigue sensitivity, the equivalent defect value of the notched component can be further expressed as:

[0150]

[0151] in, is the fatigue notch factor, which includes the inherent defect factor Y of the material and the actual geometric factor of the notch (before cracks appear) And a 0,l It is obtained when Y is 1.

[0152] In one embodiment, the fatigue notch factor of a notched component may be calculated by the following formula:

[0153]

[0154] Wherein, F(a) represents fatigue notch factor, a represents crack size, c represents notch size, such as the radius of the notch of a circular hole, W represents the width of the notched component, such as the size of the notched component along the crack propagation direction, and l=a+c.

[0155] In one embodiment, the above-mentioned determination of the equivalent initial defect size of the notched component according to the long crack extension threshold value of the notched component, the geometric shape factor, the fatigue notch factor, and the equivalent initial defect size of the smooth component may include the following steps:

[0156] According to the long crack extension threshold value and material properties of the notched component, the intrinsic crack extension threshold value of the notched component is determined;

[0157] The equivalent initial defect size of the notched component is determined according to the intrinsic crack growth threshold value of the notched component, the geometric shape factor, the fatigue notch factor and the equivalent initial defect size of the smooth component.

[0158] Among them, when considering the non-conservative EIFS value of the real sample, the following relationship exists:

[0159]

[0160] By using the in-plane (intrinsic) fatigue limit Δσ smooth,e and the strongest microstructural barrier size d ph The functional relationship is defined as the minimum intrinsic resistance to microcrack propagation (microstructure threshold ΔK th,eff ), refer to the following function expression:

[0161]

[0162] In order to consider the temperature sensitivity of the nickel-based single crystal microstructure, and the two phases are cut differently according to the temperature, the d dh It can be defined as the size of the matrix phase or reinforcement phase at different temperatures, depending on which component phase the dislocation appears first. Further, it can be concluded that:

[0163]

[0164] Among them, ΔK th,eff Indicates the intrinsic crack extension threshold of the notched component, ΔK th,l represents the long crack extension threshold of notched components, d ph It represents the strongest microstructural obstacle size determined by the material properties of the notched component. For example, for nickel-based single crystals, this size can be the matrix phase or the strengthening phase size.0,l represents the transition crack size determined by the smooth component. The intrinsic crack extension threshold of the notched component can be calculated by formula (30).

[0165] refer to Fig.11 As shown in Figure 2, the modified KT of the real specimen can be described as a parallel segment, which represents the difference in macro crack nucleation under the effect of the notch-crack coupling coefficient. For an ideal pure notch structure, the critical notch depth a for long crack initiation is p is ΔK th,l With Δσ smooth，e / K t The intersection line of , that is:

[0166]

[0167] The actual critical notch depth is:

[0168]

[0169] Considering the notch sensitivity during crack propagation, the critical notch depth a for long crack initiation is p is ΔK th,l With Δσ smooth,\ λ / K t The intersection line of is shown in Figure 13. At this time, equations (31) and (32) can be rewritten as:

[0170]

[0171] Since the size of the plastic zone of the crack in this scale range cannot be ignored, for the sake of simplification, the crack tip plastic zone in the two-dimensional mode can be modified to meet the linear elastic fracture mechanics conditions. d It can be solved through experiments and numerical solutions, and the degree of agreement is very high. The surface of the component will produce greater plasticity than the interior. When the plane stress state of two-dimensional anisotropic material (z = 0), the stress and displacement on both sides of the hole can be determined by the following formula:

[0172]

[0173] When the structure and load are symmetrical about the x-axis and y-axis, the above formula can be further expressed as:

[0174]

[0175] According to the finite element results of nickel-based single crystals combined with the Dugdale model and the Antolovich model, the following relationship is obtained:

[0176]

[0177] In one embodiment, the above-mentioned determination of the equivalent initial defect size of the notched component according to the intrinsic crack extension threshold value of the notched component, the geometric shape factor, the fatigue notch factor, and the equivalent initial defect size of the smooth component may include the following steps:

[0178] Determine the safe fatigue limit of the smooth component based on the equivalent initial defect size and fatigue limit of the smooth component;

[0179] The equivalent initial defect size of a notched component is calculated using the following formula:

[0180]

[0181] Among them, EIFS mod,notch represents the equivalent initial defect size of the notched component, K t / λ represents the fatigue notch factor of notched components, ΔK th,eff represents the intrinsic crack extension threshold of the notched component, η represents the plastic zone correction coefficient of the notched component, Δσ 0 represents the safety fatigue limit of the smooth component, and F(aη) represents the geometric shape factor of the notched component, which can be calculated by formula (27).

[0182] By further deducing formula (37), we can get:

[0183]

[0184] It should be noted that ΔK th,eff It is essentially the basic property of the material. For the same process, ΔK th,eff It can be regarded as unchanged, but for different processes and different temperatures, especially in the evaluation of notched (air film hole) components prepared by different hole making processes, the material properties of the hole edge change, resulting in ΔK th,eff The EIFS of the notched component determined at room temperature can be used to further infer the ΔK under different temperature conditions. th,eff .

[0185] Fig. 12A The EIFS values ​​at different survival rates are shown. Fig. 12B The linear description of notched components based on EDM process at different survival rates and crack geometry correction factors is shown. Fig. 12C The linear description of notched components based on LDM process at different survival rates and crack geometry correction factors is shown. Fig. 12AAs shown in the figure, the EIFS values ​​of notched components prepared by the two hole-making processes of EDM and LDM are quite different. Under the conditions of 95% guarantee rate and 50% survival rate, the EIFS value of EDM is about 0.022mm, while that of LDM is about 0.047mm. According to the test data satisfying different survival rates (0-100%), the EIFS value of EDM is between 0.0188-0.0273mm, while that of LDM is between 0.0423-0.0530mm. When a certain stress is applied, the calculated EIFS interval range will be further narrowed, and the interval changes of EDM and LDM are roughly within 0.01mm. It should be noted that when considering three stress levels (stress level changes by more than 20%), the interval peaks (maximum and minimum values) of EIFS are only expanded by about 2%, respectively. Compared with the common calculation method that the EIFS value is closely related to the stress magnitude, this change trend can be ignored. Under different survival rates, the EIFS value satisfies a strong linear relationship with the survival rate and the crack geometry correction factor, and the crack geometry correction factor also changes only slightly (e.g. Fig. 12B After determining the specific correlation function, it is more valuable to predict the universality of EIFS in engineering practice.

[0186] Continue to refer Figure 1 In step S130, based on the second test data, the equivalent stress intensity factor difference and fatigue crack growth rate of the notched component under high temperature conditions are obtained; the equivalent stress intensity factor difference is the difference between the effective value of the equivalent stress intensity factor that comprehensively considers various types of crack growth driving forces in the notched component and the threshold value of the equivalent stress intensity factor.

[0187] In this exemplary embodiment, the stress intensity factor under the action of various types of crack extension driving forces in the component is comprehensively considered and expressed as the equivalent stress intensity factor K eq , and calculate the parameters related to the stress intensity factor, such as the effective value of the equivalent stress intensity factor, the threshold value of the equivalent stress intensity factor, etc. The equivalent stress intensity factor is explained below.

[0188] Fig.13A The schematic diagram of the component geometric coordinate system and the crack random extension surface is shown. According to the simulation results of the anisotropic stress intensity factor, the stress function expression of the local three-dimensional crack tip in the component geometric coordinate system is:

[0189]

[0190] Among them, σ ij (r,θ) represents the stress tensor in the component geometric coordinate system, r is the distance to the crack tip on the vertical plane, and θ is the angle of the crack propagation direction; f ij(θ), g ij (θ), h ij (θ) is a geometric function used to define the geometric angle dependence of the stress field; K I , K Ⅱ , K Ⅲ is the stress intensity factor of pure type I (tensile), type II (shear) and type III (tear). Ω(K ￡ ,K ￡￡ ,K ￡I￡ ,θ) are three different stress intensity factor functions. The stress tensor depends on the local polar coordinates r and θ at the crack tip. By calculating the stress intensity factor, the stress fields at the pure mode I (tensile) crack, mode II (shear) crack, and mode III (tear) crack tips are superimposed to obtain the three-dimensional stress field at the crack tip.

[0191] The distance between a point on the crack random extension surface and the crack front is r', and its spatial position can be determined by the angles α, β, and γ between the three coordinate axes. Ignoring the change of the stress field along the z-axis in a small range, the distance r' on the crack random extension surface can be projected onto the crack vertical surface, and the corresponding relationship is as follows:

[0192]

[0193] We can further get:

[0194] θ=arctan(cosβ / cosγ) (41)

[0195] Substituting equations (40) and (41) into equation (39), the stress field at the crack tip on the crack random extension surface is:

[0196]

[0197] The stress field on the crack random extension surface can be used to obtain the shear stress intensity factor in different directions. The unit normal vector on the crack random extension surface is regarded as n, the unit vector on the plane is s, and the shear unit vector is t. According to the spatial relationship, t = n × s can be obtained. It should be noted that the vector s can be projected onto the three coordinate axes of the geometric coordinate system in space, and its component matrix is ​​(s x ,s y ,s z ).

[0198] After the crack appears as a crystal surface crack, the equivalent stress intensity factor k I , k Ⅱ , k Ⅲ will appear at the same time, corresponding to the three directions of crystal slip (or the three principal axes of the local slip coordinate system, with the coordinate axes denoted as m, n, and z). Fig. 13B As shown, kI is the crystal plane normal vector n driving force, k Ⅱ is the action of vector s on the crystal surface, k Ⅲ is the action of vector t. Therefore, in the slip system (SS) ω The vectors n, s, and t can be regarded as the unit normal vector (SN)n of the crystal slip plane (SP) ω , slip direction unit vector (SD) m ω and z ω (z ω =n ω ×m ω ).

[0199] According to the slip coordinate system on the crystal plane, the decomposed shear stress and normal stress can be calculated as:

[0200]

[0201] At this point, the following relationship exists:

[0202]

[0203]

[0204] Stress intensity factor k of crystal slip plane I , k Ⅱ , k Ⅲ Conventional stress intensity factor K for the plane perpendicular to the crack I , K Ⅱ , K Ⅲ Between, satisfy Multiple relationship, that is:

[0205]

[0206] The octahedral slip system is generally regarded as a potential crystal plane crack after the crack transforms from a Mode I crack. Considering that the crystal crack is driven on the {111} slip plane, and considering that the driving force of the oblique crack is affected by τ rss and τ rns The equivalent stress intensity factor k of the crystal slip plane is eq Can Fig. 13C A schematic diagram of the crack tip coordinate system x'-y'-z' is shown. In the crack tip coordinate system, the y' axis is parallel to the crystal plane normal vector n ω , then δ = 0. The equivalent stress intensity factor k of the crystal slip plane eq It can be expressed as follows:

[0207]

[0208] On a certain crystal plane, according to the singularity of the stress field at the crack tip, θ→0, then the following relationship exists:

[0209]

[0210] Therefore, the equivalent stress intensity factor of the entire crack process can be uniformly expressed as formula (11):

[0211]

[0212] Among them, a p is the length in the direction perpendicular to the loading axis, a T is the crack size when Mode I is transformed to Stage I. In this exemplary embodiment, parameters related to the stress intensity factor can be calculated based on equation (49).

[0213] From the above, we can see that there may be different types of crack growth driving forces in the component, and the fatigue crack growth rate will be affected by these factors. The following is an analysis.

[0214] After crack initiation, at different temperatures, crack propagation along the crystal plane and amorphous plane presents two modes, which are closely related to the structure of the component, test temperature, and crystal orientation. Generally speaking, at low temperatures, crystal cracks propagate along the octahedral slip plane, while at high temperatures, cracks propagate in an I-type "opening". Taking nickel-based single crystal alloy as an example, its fatigue failure is driven by the decomposed shear stress acting on the specified slip plane in front of the crack tip, rather than the maximum principal stress of the polycrystal. The most typical driving force for crack propagation in nickel-based single crystals is the shear stress intensity factor and the octahedral equivalent factor, as well as a mixed description of these two factors. The stress intensity factor is controlled by linear elasticity, and there is an obvious "small crack effect". In addition, the short crack growth rate under high temperature conditions is significantly higher than the short crack growth rate under low temperature conditions. Based on the crack propagation mechanism, when calculating or predicting the fatigue crack growth rate, the sum law of crack propagation controlled by mechanical factors and environmental factors can be considered.

[0215] Due to the so-called environmentally assisted cracking in polycrystalline high-temperature alloys, the fatigue crack growth rate is accelerated by several orders of magnitude under long-term loading and air conditions. The main mechanisms are: stress-assisted grain boundary oxidation and dynamic oxidation. In addition to these two ubiquitous mechanisms, another oxygen-related fatigue mechanism is sometimes considered in single-crystal high-temperature alloys - the oxidation-induced crack closure effect (or simply the oxidation closure effect). Compared with vacuum conditions, the propagation rate of near-threshold cracks is greatly slowed down. An oxide with a thickness equivalent to the crack opening displacement (COD) is believed to be formed in the crack, thereby reducing the effective value of the stress intensity range factor and the crack growth rate. The schematic diagram of crack opening during fatigue loading can be referred to. Fig.14As shown. Experimental observations show that in high temperature environments, cracks are crowned, and oxygen fills the entire crack, causing crack tip passivation. Usually, the oxides in the cracks are considered to be formed by "micro-oxidation", which means that the oxides are constantly broken and reformed under cyclic loads, forming a continuous external oxide layer. When the loading frequency is changed, high-frequency tests are more likely to cause the oxides to break repeatedly, resulting in partial oxidation closure. Low-frequency tests are conducive to the formation of thick and continuous oxides.

[0216] refer to Fig.14 As shown in the figure, for the continuous oxidation-induced crack closure effect, the following simplified assumptions can be made: ①δ max It is only related to the maximum load and is not affected by oxidation. ② Assuming that the oxide is a rigid body, δ min Equal to the thickness of the external oxide layer. ③ The thickness of the external oxide layer is the average oxide thickness within 10μm behind the crack tip. Oxygen intrudes into the material to form an internal oxide layer, which has little effect on crack opening. According to the oxide thickness, the effective value of the stress intensity range factor is calculated as follows:

[0217] ΔK eff =K max -K i (50)

[0218] Among them, K max is the stress intensity factor under maximum load, K i is the oxidation closure stress intensity factor, which can be the stress intensity factor when the crack flank contacts the oxide.

[0219] Generally speaking, when the crack surface contacts the oxide, there is a slope change in the cyclic strain-stress during the unloading stage. The stress intensity factor corresponding to the inflection point is K i Since the local crack closure has little effect on the overall mechanical response of the material, especially in the initial stage of the crack growth test, the inflection point is difficult to distinguish. This inflection point is exactly the point where the oxide contacts the crack surface. If the COD at this point can be measured, K can be calculated. i However, reference Fig.14 As shown in the figure, due to the intrusion of oxygen, the crack tip is blunted and forms a unique round shape, which is different from the normal sharp crack tip. Therefore, it is difficult to accurately calculate the COD using the calculation method for the sharp crack tip. For example, the method using the 90° intersection line may overestimate the COD. Fig.14 Schematic diagram of evaluating COD. Considering the initial contact between the crack surface and the oxide, the COD 10 μm behind the crack tip can be calculated by the following formula:

[0220]

[0221] Here, δ CODis the thickness of the outer oxide layer at 10 μm, L Oxi Indicates the length of the external oxide layer, which can be measured by SEM (scanning electron microscope) and other equipment. COD With L Oxi , and then calculate δ Oxi . Further, establish δ Oxi With K i The relationship between K i , refer to the following formula:

[0222]

[0223]

[0224] Where m is related to the material yield strength σ Y (unit: MPa) and ultimate tensile strength σ U (unit: MPa) related parameters; E' is Young's modulus under plane stress (unit: GPa).

[0225] Therefore, the actual δ can be obtained by measuring the closed oxide thickness at 10 μm at the crack tip. Oxi , and K calculated on this basis i and ΔK eff .

[0226] In one embodiment, the difference in equivalent stress intensity factor of a notched component under high temperature conditions can be determined by:

[0227] According to the second test data, determine the effective value of the equivalent stress intensity factor of the notched component under high temperature conditions, as well as the long crack extension threshold value and the intrinsic crack extension threshold value under high temperature conditions;

[0228] According to the long crack extension threshold value and intrinsic crack extension threshold value of the notched component under high temperature conditions, the equivalent stress intensity factor threshold value of the notched component under high temperature conditions is obtained;

[0229] Based on the difference between the effective value of the equivalent stress intensity factor and the threshold value of the equivalent stress intensity factor, the difference value of the equivalent stress intensity factor is obtained.

[0230] Among them, based on the above analysis, the fatigue crack growth rate can be expressed by the following formula:

[0231]

[0232] C and m are coefficients and can be obtained through fitting. eq,eff is the effective value of the equivalent stress intensity factor (unit: MPa·m 1 / 2), is the effective value of the stress intensity factor that comprehensively considers the driving forces of various types of crack growth in notched components. ΔK th,eq is the threshold value of equivalent stress intensity factor (unit: MPa·m 1 / 2 ), is the threshold range for considering the variation of the length and short cracks of EIFS. ΔK eq,eff -ΔK th,eq is the difference of equivalent stress intensity factor.

[0233] The following first explains how to determine the threshold value of the equivalent stress intensity factor.

[0234] In one embodiment, obtaining the threshold value of the equivalent stress intensity factor of the notched component under high temperature conditions according to the long crack extension threshold value and the intrinsic crack extension threshold value of the notched component under high temperature conditions may include the following steps:

[0235] According to the difference between the long crack extension threshold value and the intrinsic crack extension threshold value of the notched component under high temperature conditions, the transition stress intensity factor threshold value of the notched component under high temperature conditions is obtained;

[0236] According to the intrinsic crack extension threshold value, transition stress intensity factor threshold value and equivalent initial defect size of the notched component under high temperature conditions, the equivalent stress intensity factor threshold value of the notched component under high temperature conditions is determined.

[0237] Among them, the threshold value of equivalent stress intensity factor ΔK th，eq The calculation can refer to the following formula:

[0238] ΔK th,eq =ΔK th，eff +ΔK th，change {1-exp[-k(a-EIFS notch,mod )]} (55)

[0239]

[0240] Among them, ΔK th,l is the long crack extension threshold, ΔK th,eff is the intrinsic crack extension threshold, ΔK th,change is the threshold value of the transition stress intensity factor, a represents the crack size, and d is the strongest microstructural barrier size. In order to consider the temperature sensitivity of the nickel-based single crystal microstructure, and the two phases are cut differently according to the temperature, d here can be defined as the size of the matrix phase or the strengthening phase at different temperatures, which depends on which component phase the dislocation appears first. EIFS notch,modIt should be understood that in order to determine the threshold value of the equivalent stress intensity factor of the notched component under high temperature conditions, in the above formula, it is necessary to obtain the long crack extension threshold value, the intrinsic crack extension threshold value, the equivalent initial defect size and other parameters under high temperature.

[0241] It should be noted that due to the inherent characteristics of the material and uncontrollable factors during the test, Fig.15 As shown in the figure, the original damage state (such as the size of the fatigue source area, the difference in stress concentration, etc.) and fatigue limit (such as Δσ e , Δσ th etc.), crack extension threshold (such as ΔK th,l , ΔK th,eff etc.) all have a certain probability (represented by P) distribution.

[0242] In one embodiment, the long crack extension threshold value can be obtained by ASTM E399 standard (standard for plane strain fracture toughness of metal materials). Based on the test research, the results show that the lognormal distribution, normal distribution and generalized extreme value distribution are within the range of 0.85, where the P value of the Weibull distribution is KS The value is significantly enhanced. In other words, the Weibull distribution is more suitable for describing ΔK th,l discrete case.

[0243] At this time, the fatigue limit size that changes with the increase of crack size in stage II can be expressed as:

[0244]

[0245] Based on formula (57), the ΔK of the material can be th,l , ΔK th,eff Distributed, smooth member EIFS (or a 0 ) value, calculate Δσ th (P). Vice versa, Δσ can be obtained directly from the experiment th (P), ΔK is calculated by formula (57) th,l or ΔK th,eff The fatigue crack growth rate fitting form considering the probability distribution also has a certain probability distribution, such as Fig.16 As shown in Figure 2, the upper and lower limits of the power function fitting curve are obtained according to the different survival rates of the samples, and are extended to EIFS and the ultimate crack length, respectively.

[0246] According to formula (57), when a = EIFS, that is, Δa = 0, Δσ th (P) only with ΔK in the long crack stage th,l (P) correlation, Δσ th (P) can be determined from the PSN curve, ΔKth,l (P) can be obtained from the crack extension curve measured experimentally.

[0247] In one embodiment, considering that in Δσ th (P) and ΔK th,l In the relationship of (P), there is also a variable a, which also satisfies the probability distribution. Therefore, formulas (38) and (54) can be further rewritten as:

[0248]

[0249]

[0250] In one embodiment, the second test data includes the elastic modulus around the notch of the notched component under high temperature conditions. The in-situ strain results can be measured around the notch (such as 0.1 mm from the notch edge) using DIC (Digital Image Correlation) technology and analyzed and calculated. Accordingly, the long crack extension threshold value of the notched component under high temperature conditions can be determined by the following method:

[0251] According to the above elastic modulus, the yield strength of the notched component under high temperature conditions, and the fatigue crack growth rate, the long crack growth threshold value of the notched component under high temperature conditions is determined.

[0252] Among them, the crack growth data observed under high temperature conditions is unstable. Fig.17A As shown, to determine the ΔK of high temperature materials th,l (P), considering a dislocation with a distance of ρ from the crack tip and an angle of ψ, the dislocation movement rate under shear stress τ is v. Based on the Yokobori model, the maximum force that drives the crack to extend is generally the external force f τ and the image force f i , other forces caused by surface energy can be ignored. Since the long crack extension threshold region shows I-type crack extension, the expressions of these two forces are:

[0253]

[0254] Assumptions Fig.17A In the case of nickel-based single crystal FCC (face-centered cubic) structure, spontaneous dislocations will occur at the crack tip under repeated fatigue loads. The radius of the crack tip at the crack root opening is equal to 2n|b|, where n is the number of dislocations and b is the Burgers vector. The fatigue crack growth rate is equal to δ / 2. Fig. 17B and Fig. 17C As shown, the following relationship exists:

[0255]

[0256] In the initial crack growth stage, in order to further consider the strain hardening caused by temperature, it can be considered that the following relationship is satisfied:

[0257]

[0258] Furthermore, the crack extension direction caused by slip at the crack tip may be at an angle of 45° to the crack propagation direction, such as Fig. 17B As shown. Under plane stress state, the crack tip displacement can refer to the following formula:

[0259]

[0260] When the temperature rises, the elongation of the single crystal material increases rapidly, and the yield strength σ y Can be replaced by σ 0.2 , so the above formula can be rewritten as:

[0261]

[0262] The fatigue crack growth rate is 10 -7 ΔK in mm / cycle I Considered as the threshold value of mode I long crack extension, σ 0.2 It can be set as the yield strength of 0.2% elongation of the material that is only related to temperature. According to the elastic modulus E measured around the notch, the long crack extension threshold ΔK can be indirectly solved th,l . Fig.17D and Fig.17E The strain measurement results of notched components based on EDM and LDM hole making processes are shown respectively. Fig.18 The elastic modulus of the specimen under high temperature conditions and the long crack extension threshold ΔK considering the measurement error are shown. th,l The distribution of different samples can be obtained by ΔK th,l The calculation results are shown in Table 3.

[0263] Table 3

[0264]

[0265] Intrinsic crack extension threshold ΔK th,eff The same can be obtained through a crack extension test cyclic fracturing program. In one embodiment, the intrinsic crack extension threshold value can also be calculated by the following formula:

[0266]

[0267] Where Z(R) is the crack opening description equation, R is the stress ratio, and A and B are obtained by fitting. A can also be the Newman coefficient. A and B are used to describe the closure state of the crack. Z(R) can be calculated by the following formula:

[0268]

[0269]

[0270] Among them, σ max is the maximum test stress, σ Y is the material yield strength, σ U is the ultimate tensile strength, are material constants, ε is the material fitting parameter, and its value range is 1 to 3.

[0271] For nickel-based single crystal high-temperature alloys, the intrinsic crack extension threshold and elastic modulus satisfy the following relationship:

[0272]

[0273] Among them, ΔK th,eff (P) represents the intrinsic crack extension threshold value that satisfies a certain probability distribution, and E(P) represents the elastic modulus of the component that satisfies a certain probability distribution. The above formula can be used to calculate the intrinsic crack extension threshold value of a smooth component or a notched component under normal temperature or high temperature conditions.

[0274] Representative oxidation penetration under high temperature conditions (such as 900℃, 980℃) can be referred to Fig.19 As shown, at the geometric outline of the crack with multi-source cracking at the notch edge, the corresponding energy spectra of the elements Ni, Co, Al, Ta, W, O, and Cr can be seen. There are two different oxide layers, the outer layer is rich in Cr, and the inner layer is rich in Al. In between, there is a thin but measurable Ta and W-rich oxide layer. In addition, the local magnified SEM image provides evidence of the γ' to γ ​​phase transformation induced by the diffusion of Al atoms to form Al-rich oxides. This leads to the formation of a γ' phase consumption area and a change in the microstructure of γ' / γ below the oxide layer (close to the crack surface, beyond the crack tip and near the surface area). In addition, the presence of a clear internal oxide layer at the crack tip was observed to lead to crack closure, which confirms the above Fig.14 Part of the theoretical model.

[0275] Components with the same surface roughness and the same hole making process are considered to have the same EIFS, and the effect of temperature on the plastic zone can be ignored. According to formula (56), the ΔK of components at different temperatures that meet different survival rates can be calculated: th,eff and fatigue limit Δσ e Consider only EIFS 95 / 95When the temperature is 900℃, the ΔK of the EDM and LDM of the flat plate 1 sample is th,eff They are 4.748 and 4.923 (in MPa·m 1 / 2 ), while the LDM sample of plate 2 was 4.697 and 5.030 (in MPa·m 1 / 2 ), the hole edge crack length is within the range of 1.5 mm to meet the linear crack extension range.

[0276] When the long crack extension threshold and the intrinsic crack extension threshold of the notched component under high temperature conditions are determined, the transition stress intensity factor threshold of the notched component under high temperature conditions can be obtained by subtracting the two. Then, the intrinsic crack extension threshold and the transition stress intensity factor threshold of the notched component under high temperature conditions and the equivalent initial defect size of the notched component are substituted into formula (55) to calculate the equivalent stress intensity factor threshold ΔK th,eq .

[0277] The above describes how to determine the threshold value of the equivalent stress intensity factor. In one embodiment, the second test data includes crack tip opening parameters of the notched component under high temperature conditions; the effective value of the equivalent stress intensity factor of the notched component under high temperature conditions is determined by:

[0278] According to the crack tip opening parameters, the yield strength, ultimate tensile strength and Young's modulus of the notched component under plane stress, the oxidation closure stress intensity factor of the notched component under high temperature conditions is determined; the oxidation closure stress intensity factor is the stress intensity factor when the crack flank contacts the oxide;

[0279] The effective value of the equivalent stress intensity factor is determined based on the stress intensity factor of the notched component under maximum load and the oxidation closure stress intensity factor under high temperature conditions.

[0280] Among them, reference Fig.14 According to formula (51), the crack tip opening parameters can include the thickness of the external oxide layer and the length of the external oxide layer, which can be measured by experiments. For example, when a crack propagation test and a high cycle fatigue test are performed on a notched component under high temperature conditions, the crack tip can be observed at different stages, and the thickness of the external oxide layer δ 10 μm behind the crack tip can be measured at the stage of crack tip passivation. COD , and the entire external oxide layer length l, δ is calculated by formula (51) Oxi , and then calculate the oxidation closure stress intensity factor K by formula (52) and (53) i Then, through formula (50), K eff Replace with K eq The effective value of the equivalent stress intensity factor ΔK is obtained by combining the above methods.eq,eff .

[0281] Continue to refer Figure 1 In step S140, a crack extension function is obtained by fitting the functional relationship between the fatigue crack extension rate, the difference in equivalent stress intensity factor, and the crack size of the notched component under high temperature conditions; the crack extension function represents the functional relationship between the fatigue crack extension rate and the crack size.

[0282] In one embodiment, the above-mentioned method of fitting the functional relationship between the fatigue crack growth rate, the difference in equivalent stress intensity factor, and the crack size of the notched component under high temperature conditions to obtain the crack growth function may include the following steps:

[0283] The first functional relationship is obtained by fitting the functional relationship between the difference of equivalent stress intensity factor and the crack size of the notched component under high temperature conditions;

[0284] By fitting the functional relationship between the fatigue crack growth rate and the difference of the equivalent stress intensity factor, a second functional relationship is obtained;

[0285] Combining the first functional relationship and the second functional relationship, a crack extension function is obtained.

[0286] Among them, due to ΔK eq,eff According to the finite element calculation, it cannot be reflected by a specific function expression. In order to reflect the difference in equivalent stress intensity factor (ΔK eq,eff -ΔK th,eq ) and the crack size a, and the calculated result is fitted with a third-order function. The crack extension data of different stresses under the same process can be unified, and the crack extension description model in this exemplary embodiment is used to make EIFS notch,mod =EIFS 95 / 95 , perform exponential fitting on logarithmic coordinates, and the fitting results can be referred to Fig. 20A As shown, the first functional relationship is obtained. Fig. 20A In the figure, EDM Plate1-3 900℃ indicates that the plate 1 component is prepared based on the EDM hole making process, and the effective sample 3 is tested under the high temperature condition of 900℃. ①②③④ are four conditional fracture modes, and the goodness of fit is 0.99. Similarly, the functional relationship between the fatigue crack growth rate and the difference in equivalent stress intensity factor can be fitted, and the fitting results can be referred to Fig. 20B As shown, the second functional relationship is obtained. Fig. 20B ①②③ are three stress intensity factor calculation modes.

[0287] from Fig. 20A It can be seen that the difference in equivalent stress intensity factor (ΔK eq,eff -ΔKth,eq ) and crack size a can be used to describe the propagation of all crack paths. However, the separation degree of the LDM specimen of plate 2 at 900°C is larger than that of the other three forms. This is mainly because it directly initiates the crack from the crystal surface until it breaks, which results in a relatively smaller crack driving force at the beginning of the crack. In other words, the energy required for the initiation of pure crystal surface cracks is less than that of type I cracks. Fig. 20B It can be seen that the difference between fatigue crack growth rate da / dN and equivalent stress intensity factor (ΔK eq,eff -ΔK th,eq ) is also strongly related. The crack growth rate of the LDM specimen of plate 2 at 900°C is roughly at the same level as that of the other three forms. This further illustrates that the crack driving force of nickel-based single crystals is significantly different under different geometric component forms and temperatures. I , K II and K III The combined ΔK eq,eff It can accurately reflect the crack extension, especially the extension of small cracks. III Accounting for ΔK eq,eff The proportion of K is close to 40%, which is roughly consistent with the I The proportions are similar. After changing the size, Plate 1 and Plate 2 have a more obvious size effect, showing inconsistent crack extension. Although the crack extension path and material strength have changed significantly at 980℃ and 900℃, the fatigue crack growth rate has not changed significantly, which may be due to the fact that the influence of high-temperature oxidation on crack behavior is not much different under high temperature conditions.

[0288] By combining the first functional relationship and the second functional relationship, the functional relationship between the fatigue crack growth rate da / dN and the crack size a, that is, the crack growth function, can be obtained.

[0289] Continue to refer Figure 1 In step S150, based on the crack growth function, the equivalent initial defect size and the limit crack size of the notched component, the predicted fatigue life of the notched component under high temperature conditions is determined.

[0290] In one embodiment, the above-mentioned determination of the predicted fatigue life of the notched component under high temperature conditions based on the crack growth function, the equivalent initial defect size and the limit crack size of the notched component may include the following steps:

[0291] Taking the equivalent initial defect size of the notched component as the lower limit of integration and the ultimate crack size of the notched component as the upper limit of integration, the crack propagation function is integrated to obtain the predicted fatigue life of the notched component under high temperature conditions.

[0292] Among them, the crack extension function is the fatigue crack growth rate expressed with the crack size as the independent variable. The calculation of fatigue life can refer to the following formula:

[0293]

[0294] Among them, a c Indicates the limiting crack size, which can be obtained by microscopic observation or by calculation of fracture toughness.

[0295] The equivalent initial defect size of the notched component is taken as the lower limit of integration, and the ultimate crack size of the notched component is taken as the upper limit of integration. The crack extension function is integrated to calculate the fatigue life of the full crack extension cycle as the predicted fatigue life. The prediction result has a high accuracy.

[0296] Fig.21 The comparison diagram of predicted fatigue life and experimental fatigue life is shown. When the oxidation correction effect is not introduced, the error between the test data and the predicted results of the improved KT diagram method is within the range of 5 times the dispersion band, and most of them are within the range of 4 times. Compared with the life prediction results proposed by the existing TTCI (Time To Crack Initiation) method, the dispersion of this scheme is smaller (there are obvious upper and lower error lines in the figure) and the data is more concentrated. This is mainly because the solution of the improved EIFS fully takes into account the local ΔK th,eff , which can be directly linked to the overall macroscopic mechanics of the structure, which is different from the inverse calculation of ΔK from crack growth data. th,l It can also be further pointed out that the transition stress intensity factor threshold value ΔK th,change As the crack length increases, the introduction of the integrand (i.e., crack extension function) gradually offsets the dramatic change in fatigue life caused by the direct change in the lower limit of the integral. After the introduction of the oxidation correction effect, the oxidation closure effect acts on the crack tip to reduce the effective stress intensity factor of crack extension, thereby reducing the fatigue crack extension rate and increasing the fatigue life. It can be seen from the figure that the prediction results are greatly improved, and the errors between the test data and the prediction results are all within the 4-fold dispersion range, and most of them are within the 3-fold range.

[0297] also, Fig.21The fatigue life prediction results for normal temperature conditions are also shown. It can be seen that the fatigue life prediction error band of the specimens based on EDM and LDM hole making processes under normal temperature conditions is within a 2-fold range. A very important factor in obtaining this result is that the crack observation results under normal temperature are accurate and the environment is relatively simple relative to high temperature. The EIFS determined at normal temperature may fluctuate in a high temperature environment due to changes in the environment. For example, creep-like effects may occur under long-term action, causing stress relaxation and thus affecting the crack propagation rate. After the environment is added, it may also cause damage coupling to the original component, etc. Nevertheless, this exemplary embodiment determines the EIFS through a smooth specimen, and then determines the normal temperature EIFS of the notched component, and finally predicts the method of high temperature fatigue life, which provides a new idea and achieves good accuracy.

[0298] The exemplary embodiment of the present disclosure also provides a high temperature fatigue life prediction device based on EIFS. Fig. 22 As shown, the apparatus 2200 may include the following program modules:

[0299] The test data acquisition module 2210 is configured to acquire first test data of a crack growth test and a high cycle fatigue test on a smooth component, and second test data of a crack growth test and a high cycle fatigue test on a notched component; the second test data includes test data under high temperature conditions;

[0300] A first determination module 2220 is configured to determine an equivalent initial defect size of a smooth component and an equivalent initial defect size of a notched component according to the first test data and the second test data;

[0301] The second determination module 2230 is configured to obtain the equivalent stress intensity factor difference and fatigue crack growth rate of the notched component under high temperature conditions according to the second test data; the equivalent stress intensity factor difference is the difference between the equivalent stress intensity factor effective value and the equivalent stress intensity factor threshold value that comprehensively considers various types of crack growth driving forces in the notched component;

[0302] The third determination module 2240 is configured to obtain a crack growth function by fitting the functional relationship between the fatigue crack growth rate, the difference of the equivalent stress intensity factor, and the crack size of the notched component under high temperature conditions; the crack growth function represents the functional relationship between the fatigue crack growth rate and the crack size;

[0303] The fourth determination module 2250 is configured to determine the predicted fatigue life of the notched component under high temperature conditions based on the crack growth function, the equivalent initial defect size and the limit crack size of the notched component.

[0304] The specific details of each part of the above-mentioned device have been described in detail in the implementation method of the method part. The undisclosed details can be found in the implementation method of the method part, so they will not be repeated here.

[0305] It should be noted that, although several modules or units of the device for action execution are mentioned in the above detailed description, this division is not mandatory. In fact, according to the exemplary embodiments of the present disclosure, the features and functions of two or more modules or units described above can be embodied in one module or unit. Conversely, the features and functions of one module or unit described above can be further divided into multiple modules or units to be embodied.

[0306] The exemplary embodiments of the present disclosure also provide a computer program product. The computer program product includes a computer program, and when the computer program is executed by a processor, the high temperature fatigue life prediction method based on EIFS is implemented.

[0307] In one embodiment, the computer program product may be a tangible product containing a computer program, such as a computer-readable storage medium storing a computer program. The readable storage medium may be a storage medium based on electrical, magnetic, optical, electromagnetic, infrared, or other signals, including but not limited to: random access memory (RAM), read-only memory (ROM), magnetic tape, floppy disk, flash memory (Flash), mechanical hard disk (HDD), solid-state drive (SSD), and the like. Exemplarily, the computer program product may be implemented as a non-volatile storage medium storing a computer program, such as a read-only memory, a NAND flash memory, and the like.

[0308] In one embodiment, the computer program product may be an intangible product including a computer program. Exemplarily, the computer program product may be implemented as a virtual digital product, such as a digital file storing an executable file, an installation package, etc. of the computer program.

[0309] The code of the computer program can be written in one or more programming languages. Programming languages ​​such as C language, Java, C++, etc. The program code can be executed entirely on the user computing device, or partially on the user computing device, or as a separate software package, or partially on the user computing device and partially on a remote computing device, or entirely on a remote computing device or server. In the case of a remote computing device, the remote computing device can be connected to the user computing device through any type of network, such as a local area network (LAN), a wide area network (WAN), etc., or can be connected to an external computing device (e.g., an Internet connection provided by an operator).

[0310] The computer program may be carried or transmitted via electrical, magnetic, optical, electromagnetic, infrared, or other signals. The electronic device may convert the signal carrying the computer program into a digital signal, thereby running the computer program. When the computer program is run on an electronic device, its code is used to enable the electronic device to execute (more specifically, the processor of the electronic device may execute) the method steps of various exemplary embodiments of the present disclosure, such as the above-mentioned high temperature fatigue life prediction method based on EIFS.

[0311] The exemplary embodiments of the present disclosure also provide an electronic device. The electronic device may include a processor and a memory. The memory stores executable instructions of the processor, such as a computer program. The processor executes the method steps of various exemplary embodiments of the present disclosure by executing the executable instructions. In addition, the electronic device may also include a display for displaying a graphical user interface.

[0312] Reference below Fig.23 , the electronic device is exemplarily described in the form of a general-purpose computing device. It should be understood that Fig.23 The electronic device 2300 shown is merely an example and should not limit the functions and scope of use of the embodiments of the present disclosure.

[0313] like Fig.23 As shown, the electronic device 2300 may include: a processor 2310 , a memory 2320 , a bus 2330 , an I / O (input / output) interface 2340 , a network adapter 2350 , and a display 2360 .

[0314] The memory 2320 may include a volatile memory, such as a RAM 2321, a cache unit 2322, and may also include a non-volatile memory, such as a ROM 2323. The memory 2320 may also include one or more program modules 2324, such program modules 2324 include but are not limited to: an operating system, one or more application programs, other program modules, and program data, each of which or a combination thereof may include the implementation of a network environment. For example, the program module 2324 may include each module in the above-mentioned device.

[0315] Processor 2310 may include one or more processing units, for example: processor 2310 may include AP (Application Processor), modem processor, GPU (Graphics Processing Unit), ISP (Image Signal Processor), controller, encoder, decoder, DSP (Digital Signal Processor), baseband processor and / or NPU (Neural-Network Processing Unit), etc.

[0316] The processor 2310 may be used to execute executable instructions stored in the memory 2320 , such as executing the above-mentioned high temperature fatigue life prediction method based on EIFS.

[0317] The bus 2330 is used to realize the connection between different components of the electronic device 2300, and may include a data bus, an address bus, and a control bus.

[0318] The electronic device 2300 can communicate with one or more external devices 2400 (eg, a keyboard, a mouse, an external controller, etc.) through an I / O interface 2340 .

[0319] The electronic device 2300 can communicate with one or more networks through the network adapter 2350. For example, the network adapter 2350 can provide mobile communication solutions such as 3G / 4G / 5G, or wireless communication solutions such as wireless LAN, Bluetooth, near field communication, etc. The network adapter 2350 can communicate with other modules of the electronic device 2300 through the bus 2330.

[0320] The electronic device 2300 may display a graphical user interface through the display 2360 .

[0321] although Fig.23 Not shown, other hardware and / or software modules may also be provided in the electronic device 2300, including but not limited to: microcode, device drivers, redundant processors, external disk drive arrays, RAID systems, tape drives, and data backup storage systems, etc.

[0322] As can be seen from the above, the technical solution of the present disclosure can be implemented as a method, an apparatus, a system, a computer program product, a storage medium, an electronic device, etc. Those skilled in the art can understand that various aspects of the present disclosure can be specifically implemented in the following forms, namely: a complete hardware implementation, a complete software implementation (including firmware, microcode, etc.), or an implementation combining hardware and software, such as being respectively referred to as a "circuit", "module" or "system".

[0323] It should be understood that the present disclosure is not limited to the specific method steps or structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from the scope thereof. Those skilled in the art will easily think of other embodiments based on the specific embodiments provided by the present disclosure. Therefore, the specific embodiments provided by the present disclosure are only exemplary, and the scope and spirit of the present disclosure are indicated by the claims, and any variations, uses or adaptive changes of the present disclosure should be covered, which follow the general principles of the present disclosure and include common knowledge or customary technical means in the technical field that are not disclosed in the present disclosure.

Claims

1. A high temperature fatigue life prediction method based on EIFS, characterized in that: include: Acquire first test data of crack growth test and high cycle fatigue test on smooth components, and second test data of crack growth test and high cycle fatigue test on notched components; the second test data includes test data under high temperature conditions; Determining an equivalent initial defect size of the smooth component and an equivalent initial defect size of the notched component according to the first test data and the second test data; According to the second test data, the difference of equivalent stress intensity factor and fatigue crack growth rate of the notched component under high temperature conditions are obtained; the difference of equivalent stress intensity factor is the difference between the effective value of equivalent stress intensity factor and the threshold value of equivalent stress intensity factor taking into account the driving forces for various types of crack growth in the notched component; A crack extension function is obtained by fitting the functional relationship between the fatigue crack extension rate, the difference in equivalent stress intensity factor, and the crack size of the notched component under high temperature conditions; the crack extension function represents the functional relationship between the fatigue crack extension rate and the crack size; Based on the crack growth function, the equivalent initial defect size and the limit crack size of the notched component, the predicted fatigue life of the notched component under high temperature conditions is determined.

2. The method according to claim 1, characterized in that The difference in equivalent stress intensity factor of the notched component under high temperature conditions is determined by the following method: Determine, based on the second test data, the effective value of the equivalent stress intensity factor of the notched component under high temperature conditions, as well as the long crack extension threshold value and the intrinsic crack extension threshold value under high temperature conditions; According to the long crack extension threshold value and the intrinsic crack extension threshold value of the notched component under high temperature conditions, the equivalent stress intensity factor threshold value of the notched component under high temperature conditions is obtained; The equivalent stress intensity factor difference is obtained based on the difference between the equivalent stress intensity factor effective value and the equivalent stress intensity factor threshold value.

3. The method according to claim 2, characterized in that The second test data includes the crack tip opening parameters of the notched component under high temperature conditions; the effective value of the equivalent stress intensity factor of the notched component under high temperature conditions is determined by the following method: According to the crack tip opening parameters, the yield strength, ultimate tensile strength and Young's modulus under plane stress of the notched component, the oxidation closure stress intensity factor of the notched component under high temperature conditions is determined; the oxidation closure stress intensity factor is the stress intensity factor when the crack flank contacts the oxide; The effective value of the equivalent stress intensity factor is determined according to the stress intensity factor of the notched component under maximum load and the oxidation closure stress intensity factor under high temperature conditions.

4. The method according to claim 2, characterized in that: The second test data includes the elastic modulus around the notch of the notched component under high temperature conditions; the long crack extension threshold of the notched component under high temperature conditions is determined by the following method: The long crack extension threshold value of the notched component under high temperature conditions is determined based on the elastic modulus, the yield strength of the notched component under high temperature conditions, and the fatigue crack extension rate.

5. The method according to claim 2, characterized in that: The equivalent stress intensity factor threshold value of the notched component under high temperature conditions is obtained according to the long crack extension threshold value and the intrinsic crack extension threshold value of the notched component under high temperature conditions, including: According to the difference between the long crack extension threshold value and the intrinsic crack extension threshold value of the notched component under high temperature conditions, a transition stress intensity factor threshold value of the notched component under high temperature conditions is obtained; According to the intrinsic crack extension threshold value, transition stress intensity factor threshold value of the notched component under high temperature conditions, and the equivalent initial defect size of the notched component, the equivalent stress intensity factor threshold value of the notched component under high temperature conditions is determined.

6. The method according to claim 1, characterized in that The crack extension function is obtained by fitting the functional relationship between the fatigue crack extension rate, the equivalent stress intensity factor difference, and the crack size of the notched component under high temperature conditions, including: By fitting the functional relationship between the difference in the equivalent stress intensity factor and the crack size of the notched component under high temperature conditions, a first functional relationship is obtained; By fitting the functional relationship between the fatigue crack growth rate and the difference between the equivalent stress intensity factors, a second functional relationship is obtained; The crack extension function is obtained by combining the first functional relationship and the second functional relationship.

7. The method according to claim 1, characterized in that The method of determining the predicted fatigue life of the notched component under high temperature conditions based on the crack growth function, the equivalent initial defect size and the limit crack size of the notched component comprises: The equivalent initial defect size of the notched component is taken as the lower limit of integration, the limit crack size of the notched component is taken as the upper limit of integration, the crack propagation function is integrated, and the predicted fatigue life of the notched component under high temperature conditions is obtained.

8. The method according to claim 1, characterized in that: The determining, based on the first test data and the second test data, the equivalent initial defect size of the smooth component and the equivalent initial defect size of the notched component comprises: According to the first test data and the second test data, a long crack extension threshold value of the notched component, a long crack extension threshold value of the smooth component, a fatigue limit, and a fatigue source zone ellipse geometric parameter are obtained; Determining the equivalent initial defect size of the smooth component according to the long crack extension threshold value and fatigue limit of the smooth component; Determining the equivalent circle parameters of the fatigue source area according to the ellipse geometric parameters of the fatigue source area of ​​the smooth component; Determining the fatigue notch factor of the notched component according to the fatigue source area equivalent circle parameter, the fatigue source area ellipse geometric parameter, and the equivalent initial defect size of the smooth component; The equivalent initial defect size of the notched component is determined according to the long crack extension threshold value of the notched component, the geometric shape factor, the fatigue notch factor, and the equivalent initial defect size of the smooth component.

9. A high temperature fatigue life prediction device based on EIFS, characterized in that: include: A test data acquisition module is configured to acquire first test data of a crack extension test and a high cycle fatigue test on a smooth component, and second test data of a crack extension test and a high cycle fatigue test on a notched component; the second test data includes test data under high temperature conditions; A first determination module is configured to determine an equivalent initial defect size of the smooth component and an equivalent initial defect size of the notched component according to the first test data and the second test data; A second determination module is configured to obtain an equivalent stress intensity factor difference and a fatigue crack growth rate of the notched component under high temperature conditions according to the second test data; the equivalent stress intensity factor difference is a difference between an effective value of an equivalent stress intensity factor and a threshold value of an equivalent stress intensity factor that comprehensively considers various types of crack growth driving forces in the notched component; A third determination module is configured to obtain a crack extension function by fitting the functional relationship between the fatigue crack extension rate, the equivalent stress intensity factor difference, and the crack size of the notched component under high temperature conditions; the crack extension function represents the functional relationship between the fatigue crack extension rate and the crack size; The fourth determination module is configured to determine the predicted fatigue life of the notched component under high temperature conditions based on the crack growth function, the equivalent initial defect size and the limit crack size of the notched component.

10. An electronic device, characterized in that: include: processor; A memory, configured to store executable instructions of the processor; The processor is configured to perform the method according to any one of claims 1 to 8 by executing the executable instructions.

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