High temperature fatigue life prediction method based on eifs

Abstract

The disclosure 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 of crack propagation test and high-cycle fatigue test on a smooth member, and second test data of test on a notched member; determining equivalent initial defect sizes of the smooth member and the notched member according to the first test data and the second test data; obtaining an equivalent stress intensity factor difference and a fatigue crack propagation rate of the notched member under a high-temperature condition according to the second test data; fitting a function relationship among the fatigue crack propagation rate, the equivalent stress intensity factor difference and a crack size to obtain a crack propagation function; and determining a predicted fatigue life of the notched member under the high-temperature condition based on the crack propagation function, the equivalent initial defect size of the notched member and a limit crack size. The disclosure can realize accurate high-temperature fatigue life prediction.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of reliability design, and particularly relates to an EIFS-based high-temperature fatigue life prediction method and device and electronic equipment. BACKGROUND

[0002] In reliability and durability design, it is usually necessary to predict the fatigue life of mechanical components on an airplane, a car or a ship, so as to make a reasonable maintenance, replacement cycle or service life, and eliminate safety hazards.

[0003] When a crack is initiated on a component, the driving force of crack propagation is different under different environments. Compared with a normal temperature environment, the driving force of crack propagation under a high-temperature environment is more complex. For example, oxidation inside a structure and organization has a great influence on crack propagation under a high-temperature environment. The fatigue life prediction method for a normal temperature environment is not applicable to high-temperature fatigue life prediction. Therefore, the related art is difficult to achieve accurate high-temperature fatigue life prediction. SUMMARY

[0004] The present disclosure provides an EIFS-based high-temperature fatigue life prediction method and device and electronic equipment to at least improve the accuracy of high-temperature fatigue life prediction.

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

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

[0007] According to a third aspect of the present disclosure, a computer program product is provided, comprising a computer program, which, when executed by a processor, implements the method of the first aspect and possible implementation manners thereof.

[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 first aspect and possible implementation manners thereof by executing the executable instructions.

[0009] The technical solution of the present disclosure has the following beneficial effects:

[0010] A method for predicting the fatigue life of a member under high-temperature conditions is provided, which, based on the determination of EIFS, considers the effects of various types of crack propagation driving forces in the member, predicts the whole period of crack propagation from EIFS to the limit crack size, has high accuracy, and requires less test data. In particular, the present solution is applicable to notched members containing gas film hole structures and the like, and can be used for high-temperature fatigue life prediction of notched members based on different hole forming processes. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1A flow chart showing a method for predicting high temperature fatigue life based on EIFS in the present exemplary embodiment.

[0012] Figure 2 A schematic diagram showing a preparation of a notched component and a smooth component in the present exemplary embodiment.

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

[0014] Figure 4A A plot showing a ΔK distribution of a notched component based on an EDM process in the present exemplary embodiment. th,l

[0015] Figure 4B A plot showing a ΔK distribution of a notched component based on an LDM process in the present exemplary embodiment. th,l

[0016] Figure 5 A plot showing a ΔK distribution of a notched component based on different hole making processes in the present exemplary embodiment. th,l

[0017] Figure 6 A plot showing a fatigue limit of a smooth component and a notched component based on both EDM and LDM hole making processes in the present exemplary embodiment.

[0018] Figure 7 A plot showing a linear fitting of survival rate and fatigue limit in the present exemplary embodiment.

[0019] Figure 8 A fracture morphology plot of a smooth component in the present exemplary embodiment.

[0020] Figure 9 A schematic diagram showing a fatigue source zone ellipse and an equivalent circle in the present exemplary embodiment.

[0021] Figure 10 A plot showing a relationship between a fatigue source zone ellipse aspect ratio and a crack stress intensity factor K ratio of different geometrical forms in the present exemplary embodiment.

[0022] Figure 11 A plot showing a crack propagation curve in the present exemplary embodiment.

[0023] Figure 12A EIFS values at different survival rates in the present exemplary embodiment.

[0024] Figure 12B A linear description of a notched component based on an EDM process at different survival rates and a crack geometry correction factor in the present exemplary embodiment. ​​​

[0025] Figure 12C A linear description of the crack geometry modifier at different survival rates and for the notched component based on the LDM process in the present exemplary embodiment is shown.

[0026] Figure 13A A schematic diagram of the component geometry coordinate system and the random crack propagation plane in the present exemplary embodiment is shown.

[0027] Figure 13B A schematic diagram of the local coordinate system at the crack tip in the present exemplary embodiment is shown.

[0028] Figure 13C A schematic diagram of the crystal slip plane in the present exemplary embodiment is shown.

[0029] Figure 14 A schematic diagram of the COD in the present exemplary embodiment is shown.

[0030] Figure 15 A schematic diagram of the probability distribution of the intrinsic crack propagation threshold, the long crack propagation threshold, and other parameters in the present exemplary embodiment is shown.

[0031] Figure 16 A schematic diagram of fitting the crack propagation curve in the form of a power function in the present exemplary embodiment is shown.

[0032] Figure 17A A schematic diagram of the dislocation slip plane in the present exemplary embodiment is shown.

[0033] Figure 17B A schematic diagram of the plastic zone in the present exemplary embodiment is shown.

[0034] Figure 17C A schematic diagram of the crack initiation zone in the present exemplary embodiment is shown.

[0035] Figure 17D and Figure 17E Strain measurement results for the notched component based on the EDM and LDM hole-making processes in the present exemplary embodiment are shown.

[0036] Figure 18 A schematic diagram of the component elastic modulus in the present exemplary embodiment is shown.

[0037] Figure 19 A schematic diagram of the crack morphology and element analysis in the present exemplary embodiment is shown.

[0038] Figure 20A A fitting schematic diagram of the first functional relationship in the present exemplary embodiment is shown.

[0039] Figure 20B A fitting schematic diagram of the second functional relationship in the present exemplary embodiment is shown.

[0040] Figure 21 Results of predicting fatigue life in the present exemplary embodiment are shown.

[0041] Figure 22 A structure schematic diagram of an EIFS-based high-temperature fatigue life prediction device in the present exemplary embodiment is shown.

[0042] Figure 23 A structure schematic diagram of an electronic device in the present exemplary embodiment is shown. DETAILED DESCRIPTION

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

[0044] The accompanying drawings, which are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this application, illustrate certain non-limiting embodiments of the present disclosure. In the drawings, some embodiments are shown in cross-section, and in plan, which are schematic illustrations. Identical or similar elements are referred to with identical or similar reference numerals throughout the specification. The illustrations presented are not necessarily drawn to scale. Some of the blocks in the diagrams can be functional blocks that can not necessarily correspond to physical or logical 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 can be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of the embodiments of the present disclosure. One skilled in the relevant art, however, will recognize that the embodiments of the present disclosure can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail in order to avoid obscuring aspects of the present disclosure.

[0045] An EIFS-based high-temperature fatigue life prediction method is provided in the exemplary embodiments of the present disclosure. 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, and the EIFS distribution has the following characteristics: the EIFS distribution only depends on material properties, processing technology and assembly state, and does not depend on the use conditions (such as spectrum or stress level), and data under different use conditions can be deduced to the same EIFS distribution (i.e., "universal EIFS distribution"); the EIFS distribution is not the real physical defect or crack distribution in the original material, but a mathematical representative quantity of the original fatigue quality, and after a certain time of hypothetical crack propagation from the EIFS distribution, it is consistent with the real crack propagation.

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

[0047] Step S110: Obtain first test data for crack propagation test and high cycle fatigue test on smooth component, and second test data for crack propagation test and high cycle fatigue test on notched component; the second test data includes test data under high temperature conditions.

[0048] Step S120: Determine 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.

[0049] Step S130: Based on the second experimental data, obtain the equivalent stress strength factor difference and fatigue crack propagation rate of the notched component under high temperature conditions; the equivalent stress strength factor difference is the difference between the effective value of the equivalent stress strength factor and the threshold value of the equivalent stress strength factor, which comprehensively considers the driving forces of various types of crack propagation in the notched component.

[0050] Step S140: By fitting the functional relationship between fatigue crack propagation rate, equivalent stress strength factor difference, and crack size of notched components under high temperature conditions, a crack propagation function is obtained; the crack propagation function represents the functional relationship between fatigue crack propagation rate and crack size.

[0051] Step S150: Based on the crack propagation function, the equivalent initial defect size and the ultimate crack size of the notched component, predict the fatigue life of the notched component under high temperature conditions.

[0052] based on Figure 1 The method described provides a way to predict the fatigue life of components under high-temperature conditions. Based on the determined EIFS (Extended Intensity Forearm Size), it considers the effects of various types of crack propagation driving forces within the component and predicts the entire life cycle of crack propagation from EIFS to the ultimate crack size. It has high accuracy and requires less experimental data. In particular, this method is applicable to notched components including film pore structures, and can predict the high-temperature fatigue life of notched components based on different hole-making processes.

[0053] The following is about Figure 1 Each step in the process will be explained in detail.

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

[0055] The notch refers to a discontinuous region on the outer surface of the component, such as a hole or the like. The outer surface of the notched component has a notch, such as a component simulating the film hole structure of an aero turbine blade, and the notch is a 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 notched component. In the example embodiment, the notched component and the smooth component are of the same material and have the same or similar profile and size. For example, the notched component and the smooth component are of the same metal or alloy material, are cuboids, and have equal length, width and height. The difference is that the outer surface of the notched component has an opening (i.e. a notch), and the outer surface of the smooth component is smooth and complete. In this way, the test results of the notched component and the smooth component can be compared to calculate the notch effect. The notch of 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 A schematic diagram of preparing test components is shown. The second generation of nickel-based single crystal superalloy DD6 in China is used as the component material. After standard heat treatment of the unprocessed blank material, two types of flat plates are prepared respectively to ensure the same orientation, including pure rectangular flat plates and dog bone-shaped flat plates, so that more test components can be prepared on the same limited size of blank material. The flat plate without opening is prepared as a smooth component, and the flat plate with opening (such as simulating a film hole) is prepared as a notched component, and the hole making process can adopt EDM and LDM. For example, the thickness of the rectangular flat plate can be designed as 0.8 mm, and the diameter of the film hole is 0.8 mm. The thickness of the dog bone-shaped flat plate is 1.0 mm, and the diameter of the film hole is 0.5 mm.

[0057] The crack propagation test refers to applying a cyclic stress to the component sample and observing the crack propagation. The difference between the high cycle fatigue test and the crack propagation test lies in the number of times of applying the cyclic stress. The number of times of cyclic stress of the crack propagation test is usually 10 5 orders of magnitude, and the number of times of cyclic stress of the high cycle fatigue test is usually 10 7 orders of magnitude. Table 1 shows the conditions of the crack propagation test and the high cycle fatigue test. For example, three samples can be prepared, flat plate 1 is a rectangular flat plate sample with holes, including an EDM opening rectangular flat plate sample and an LDM opening rectangular flat plate sample, flat plate 2 is a dog bone-shaped flat plate sample with holes, and the LDM hole making process is used, and flat plate 3 is a smooth dog bone-shaped flat plate sample. σ maxrepresents the stress amplitude, i.e. the maximum stress in the cyclic loading. For the notched specimens, cyclic stresses with stress amplitudes of 160-240 MPa at room temperature, and stress amplitudes of 580 MPa and 550 MPa at high temperatures of 900 °C and 980 °C, respectively, were applied at a frequency of 78 Hz for the notched specimens and at a frequency of 5 Hz for the smooth specimens. For the smooth specimens, cyclic stresses with stress amplitudes of 350-450 MPa at room temperature were applied at a frequency of 78 Hz. A stress ratio of 0.1 was used in all cases, i.e. the ratio of the minimum stress to the maximum stress in the cyclic loading was 0.1. For each test condition, a number of valid specimens can be provided 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 propagation of the specimen under the cyclic stress is detected, and the test data is recorded. The test data of the smooth specimen (e.g. plate 3) is the first test data, which can include the test data at room temperature. The test data of the notched specimen (e.g. plate 1, plate 2) is the second test data, which can include the test data at high temperature, and can also include the test data at room temperature.

[0062] With reference to the foregoing Figure 1 In step S120, the equivalent initial defect size of the smooth specimen and the equivalent initial defect size of the notched specimen are determined according to the first test data and the second test data.

[0063] In an embodiment, the determination of the equivalent initial defect size of the smooth specimen and the equivalent initial defect size of the notched specimen according to the first test data and the second test data can include the following steps:

[0064] According to the first test data and the second test data, the long crack propagation threshold value of the notched specimen, the long crack propagation threshold value, the fatigue limit, and the fatigue source area elliptical geometric parameter of the smooth specimen are obtained;

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

[0066] According to the fatigue source area elliptical geometric parameter of the smooth specimen, the equivalent circle parameter of the fatigue source area is determined;

[0067] According to the equivalent circle parameter of the fatigue source area, the fatigue source area elliptical geometric parameter, and the equivalent initial defect size of the smooth specimen, the fatigue notch factor of the notched specimen is determined;

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

[0069] Wherein, the nucleation and propagation of the crack can be generally described according to the Griffith condition, and the elastic relationship between the crack size a (generally referring to the crack length, i.e. the size of the crack along its propagation direction) and the required stress σ can be referred to the following formula:

[0070]

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

[0072] The stress intensity factor is a physical quantity reflecting the strength of the elastic stress field at the crack tip, and the unit is MPa·m 1 / 2 . The crack propagation threshold value refers to the stress intensity factor alternating value of the member with a crack under alternating load, which will not cause fatigue propagation, and is represented by ΔK th . In the example embodiment, two crack propagation threshold values are considered, which are the intrinsic crack propagation threshold value represented by ΔK th,eff , and the long crack propagation threshold value represented by ΔK th,l .

[0073] It is assumed that there is a critical crack a0, so that when the actual crack size a < a0, the crack propagation threshold value decreases with the decrease of the crack size, and when a > a0, the crack propagation threshold value is independent of the crack size. Further, a < a0 generally represents the small crack propagation stage, and the stress state at this time is difficult to be completely described by linear elasticity. In order to simplify, the fatigue limit of different crack sizes can be described linearly, and the following formula is referred to:

[0074]

[0075] Based on the interpretation model of the K-T diagram (Kitagawa-Takahashi diagram) of linear elastic fracture mechanics, it is proposed to take any hypothetical crack size a 0,l as the transition crack size, which reflects the phenomenon that the fatigue limit increases with the decrease of the crack, and the following formula is referred to:

[0076]

[0077] Wherein, ΔK th,l represents the long crack propagation threshold value (MPa·m 0.5 ); Δσ e represents the fatigue limit (MPa); and Y represents the crack geometry correction factor.

[0078] When the crack size a is significantly smaller than a th = Δσ e , Y = 1. Meanwhile, a 0,l can be regarded as the critical value of crack continuous propagation. There is the following relationship:

[0079]

[0080] Based on this, due to the inability of the material to withstand high stress, local plastic damage occurs under repeated fatigue load, strain gradient is generated by dislocation accumulation, slip band, intrusion and extrusion, resulting in local stress concentration to form internal stress. This explains why damage still occurs and the component is destroyed when the crack (or equivalent defect) size is smaller than a 0,l , and the nominal stress is greater than Δσ e . Obviously, the required conditions for crack propagation threshold cannot be met in this area (the area where the crack size is smaller than a 0,l , and the nominal stress is greater than Δσ e ). Therefore, there may be another threshold value smaller than ΔK th,l , that is, the intrinsic crack propagation threshold ΔK th,eff , in the small crack propagation stage.

[0081] Figure 3 The relationship between fatigue strength and fracture mechanics is described by multiple related graphs. Figure 3 The da / dN-ΔK curve in the long crack stage is extended to the short crack direction, and based on the changes in the mechanical behavior of different crack propagation stages, the crack propagation goes through three stages of microstructure short crack, mechanical short crack and long crack, as shown in the three stages of K-T diagram. In stage I, the crack size is limited to a small scale, and the crack size is generally arranged in the order of microstructure characteristics such as grain size. In this scale range, microstructure becomes the dominant factor of crack propagation, and the corresponding crack driving force (or crack driving load) can be described by microstructure fracture mechanics. When the microstructure is not enough to inhibit crack propagation, such as when the crack exceeds 1-2 grain sizes (as shown in stage II of the K-T diagram), the crack propagation is dominated by the surrounding grains, and the plastic zone size is too large to be ignored for small cracks. When the crack size is smaller than a 0,l , the ΔK th,l concept of linear elastic fracture mechanics does not apply.

[0082] Microstructure mechanism has important influence on fatigue crack propagation of superalloy. In the case of relatively small defects, short fatigue crack propagation needs to be considered. In addition to the influence of plastic zone and microstructure at crack tip, the biggest difference between long and short cracks is the influence of closure effect. When solving EIFS value by using fracture mechanics method, the plastic zone of small crack is involved, and the crack size needs to be corrected for solving true stress intensity factor. From the cyclic R curve of Figure 3 , it can be seen that short crack of microstructure must overcome the inherent crack propagation threshold value of material and structure, i.e. intrinsic crack propagation threshold value ΔK th,eff , to enter the stage II. In polycrystalline material, a 0,l can be regarded as a characteristic size, which is the boundary point between long and short cracks, but the value is not conservative. The crack first needs to resist the influence of microstructure such as grain boundary. At the same time, it is also the demarcation point between macroscopic crack and microscopic crack. For nickel-based single crystal material (no grain), the characteristic size cannot be represented by grain size. Under the action of internal stress, the crack smaller than the limit crack size can still break within 10 7 cycles. If the limit crack size can be overcome, a0 can be used to describe EIFS, so as to solve the evaluation problem of different hole-making initial damage. When the crack size is small, the plastic zone is more likely to form. Generally speaking, the plastic zone of short crack is about 8 times that of long crack under the same stress intensity factor, or even equivalent to the size of a short crack. Therefore, the plastic zone plays an important role in the elastic stress field which cannot be ignored. At the two demarcation points of the whole crack, the intrinsic crack propagation threshold value and the long crack crack propagation threshold value are introduced respectively, which corresponds to the crack propagation resistance curve (R curve). According to the difference of stress field, a0 point is taken as the limit state of elastic-plastic description.

[0083] The long crack propagation threshold value ΔK th,l can be regarded as a material parameter, and ΔK th,l at room temperature can be used to calculate the EIFS of smooth component.

[0084] Figure 4A The ΔK eq -da / dN curve of notched component based on EDM process is shown, Figure 4B The ΔK eq -da / dN curve of notched component based on LDM process is shown. The abscissa in the figure is equivalent stress intensity factor ΔK eq (MPa·m 0.5 ), which can be obtained by crack propagation test and 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), i.e. the crack growth length per cycle of loading stress. The second test data can include the fatigue crack growth rates corresponding to different equivalent stress intensity factors, i.e. the data points in Figure 4A or Figure 4B . The figure shows the data of each valid sample tested with different stress amplitudes at room temperature, for example, "180-1" represents the data of valid sample 1 tested with a stress amplitude of 180 MPa. The figure also shows the fitting zone and the fitting curve based on the survival rate (Ps), and the fitting curve is an exponential form 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 the fatigue crack growth rate in a preset numerical range can be fitted, and the preset numerical range can be determined according to specific requirements, which can be a relatively ideal numerical range of the fatigue crack growth rate, such as 10 -7 -10 -6 mm / cycle. For example, the second test data with the fatigue crack growth rate in the range of 10 -7 -10 -6 mm / cycle is fitted to obtain the long crack growth threshold of the notched component based on the EDM process and the LDM process, respectively. Figure 4A The ΔK th,l distribution diagram of the notched component based on the EDM process is shown. Figure 4B The ΔK th,l distribution diagram of the notched component based on the LDM process is shown.

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

[0087] In order to make full use of the data, the crack propagation data of the notched component at room temperature is used to calculate the long crack propagation threshold of the smooth component, so as to simplify the test process. Due to the dispersion of the test results and the size of the hole edge influence zone, the long crack propagation threshold at a relatively high survival rate (such as 99.9%) is generally selected as the long crack propagation threshold of the smooth component. Exemplarily, the ΔK th，l satisfies the three-parameter Weibull (Weibull 3P) probability distribution, as shown in the following formula:

[0088]

[0089] wherein P represents the survival rate (i.e. probability), and α, β, γ are parameters of the three-parameter Weibull probability distribution, and the values of α, β, γ can be obtained by least square fitting, as shown in Table 2. As described above, the long crack propagation threshold ΔK th,l,smooth of the smooth component at room temperature can be obtained at a survival rate of 99% and is about 1.93 MPa·m 0.5 .

[0090] Table 2

[0091]

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

[0093] The fatigue limit is described below.

[0094] The EIFS value of the notched component (such as the gas film hole) is smaller than a 0,l , which can ensure the safety of the structure, and the safety fatigue limit of the hypothetical smooth component is After transformation, the safe EIFS can be obtained as and the corresponding safe fatigue limit is:

[0095]

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

[0097] Δσ0=A·a m (7)

[0098] wherein A is a constant closely related to the material. The logarithm of formula (6) and (7) is taken, and the derivative of lna is obtained as:

[0099]

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

[0101]

[0102] When a = a0, To determine the actual fatigue limit corresponding to the crack size, equation (6) can be rewritten as:

[0103]

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

[0105] The fatigue source area elliptical geometry parameters are described below.

[0106] In the early stage of hole making, the early propagation of micro-cracks is strongly affected by the microstructure of the material without cracks. The survival rate can be introduced to obtain the P-S-N (survival rate-stress amplitude-life) curve, which can better reflect the data dispersion compared to the S-N curve. In order to separate the original material processing factors and component geometric size factors, the fatigue limit test of smooth components under normal temperature conditions is carried out by the lifting method, and the fatigue limit of smooth components is obtained.

[0107] Figure 6 The fatigue limit diagram of smooth components and notched components based on EDM and LDM hole making processes is shown. The solid line in the middle of the figure is the fatigue limit fitting line of notched components based on EDM process under different survival rates, from bottom to top, the fatigue limit under 99.99%, 50%, and 0.01% survival rates, respectively. The dashed line in the middle of the figure is the fatigue limit fitting line of notched components based on LDM process under different survival rates, from bottom to top, the fatigue limit under 99.99%, 50%, and 0.01% survival rates, respectively. Referring to Figure 6 It is shown that under 50% survival rate, the Δσ e of the smooth component is 377.6 MPa (L s horizontal line in the figure), and under the same test environment, the fatigue limits of notched components based on EDM and LDM processes under 99.99% survival rate and 95% confidence are 55.113 MPa and 47.0 MPa, respectively; and under 50% survival rate and 95% confidence, the Δσ e of notched components of the two processes are 59.2 MPa and 47.6 MPa (L e and L l horizontal lines in the figure), respectively. Assuming that the fatigue life under the same stress level satisfies the normal distribution, considering five survival rates of 0.01%, 20%, 50%, 80%, and 99.99%, the relationship between survival rate and fatigue limit can be obtained by linear fitting, which can be referred to Figure 7The survival rate and fatigue limit approximately 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 surface crack of size a, under uniaxial remote tensile stress σ ∞ The stress intensity factor can be written as F is the geometric correction factor of the actual sample. For cracks in the notch stress field, the stress intensity solution is asymptotically the same as that of the surface crack in a smooth solid, except that the far-field stress is amplified by the stress concentration factor K t = σ max / σ ∞ Therefore, when a→0, the following relationship holds:

[0109]

[0110] where F0 represents the geometric factor of the surface crack of the smooth member. For cracks located in the notch stress field, the asymptotic solution of the geometric factor F is:

[0111] F = F0K t (12)

[0112] When the crack propagates beyond the notch stress field, the far-field stress field dominates the stress intensity factor, which can be expressed by equation (13):

[0113]

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

[0115]

[0116] In the equation, F ∞ is the reference geometric factor, and when d / a << 1, F can asymptotically approach a constant, i.e. F = F0. At this time, the upper and lower bounds of the geometric factor F are F0, F0K t respectively. Using these asymptotic solutions, a simple formula for the geometric factor F caused by the root of the notch of any size can be established.

[0117] For a through crack located at the root of the notch, the "equivalent" surface crack depth, the geometric factor F is limited by the upper and lower asymptotes, so that 1<F / F0<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 equation:

[0120]

[0121] where,

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

[0123]

[0124] It should be noted that after introducing the notch, the fatigue limit of the smooth component and the notched component cannot be simply determined according to K t , because the high-stress material surface "similarity" cannot be met. The fatigue notch factor is defined as K f , that is, the effective stress concentration coefficient, and the specific expression is:

[0125]

[0126] where σ smooth,e represents the fatigue limit of the smooth component, and σ notch,e represents the fatigue limit of the notched component.

[0127] In order to consider the fatigue notch effect, it is assumed that the smooth component has 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 value, the smooth component reaches the fatigue limit σ smooth,e , and a finite geometry correction factor is introduced, which has the following relationship:

[0128]

[0129] where a represents the conservative EIFS crack size (mm) of the smooth component; d r represents the equivalent size (mm) of the micro-defects in the fatigue source area of the smooth component; and a0 represents the geometry correction coefficient of the crack size a+d in the finite size component, which can be obtained by the handbook of fracture mechanics or finite element calculation.

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

[0131]

[0132] where d n represents the actual notch size.

[0133] Substitute equations (18) to (20), we can get:

[0134]

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

[0136]

[0137] When , i.e. the equivalent size of the micro-defects is much larger than the EIFS, K f = 1, at which time the notch effect can be ignored; when , i.e. the equivalent size of the micro-defects is much smaller than the EIFS, K f = K t .

[0138] The elliptical geometric parameters of the fatigue source area are described below.

[0139] Figure 8 The fracture morphology of the smooth member is shown, and it can be seen that the overall fracture presents clear three fracture ranges: the fatigue source area at the geometric size mutation, the crack propagation area (with obvious fatigue stripes), and the instantaneous fracture and tearing area (the protruding ductile fracture surface). The fatigue source area can be approximated as an ellipse or a semi-ellipse (e.g. the fatigue source area is approximated as a semi-ellipse in Figure 8 ), and the elliptical geometric parameters of the fatigue source area are obtained by measuring the geometric size of the fatigue source area, etc. The elliptical geometric parameters of the fatigue source area can include the lengths of the major and minor axes of the ellipse, the ratio of the major and minor axes, etc.

[0140] The inclusion area (or micro-defects) of the fatigue source area can be approximated as an ellipse or a semi-ellipse, i.e. the actual "EIFS" is in a two-dimensional state, the ellipse or semi-ellipse is approximated as an equivalent circle, the equivalent circle parameters are determined, and the "equivalence" of the EIFS is realized.

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

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

[0143]

[0144] The above equation can be simplified as:

[0145]

[0146] According to the area equivalence formula, a0can be expressed as (a / r) 2 The stress intensity factor ratio of the ellipse and the equivalent circle is:

[0147]

[0148] Reference Figure 10 The results show that the maximum ratio of Kand Kis about 1.091, and a0= 0.489 at this time. At the same time, when a0changes between 0.2 and 1, the ratio of K 椭 / K 圆 changes within 9.1%. By observing the actual value of a0of the smooth component, K 圆 and the crack radius r (i.e., the equivalent circle radius) after the dimension reduction of the crack size can be determined, and they can be regarded as d r .

[0149] For notched components, the original K-T diagram obtained by using smooth components cannot describe the crack initiation and propagation behavior of the component, because the crack initiation and propagation is not only affected by the material defects, but also by the stress concentration caused by the geometric size. Reference Figure 11 The inherent defects of the material are regarded as a 0,l When there is a central sharp crack, a 0,l can reflect the crack initiation behavior of the component. Under the action of the notch, the equivalent defect value of the notched component can be further expressed as:

[0150]

[0151] wherein, is the fatigue notch factor, which includes the inherent defect factor Y of the material and the actual geometric factor of the notch (before the crack appears) and a 0,l is obtained when Y is 1.

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

[0153]

[0154] where F(a) represents a fatigue notch factor, a represents a crack size, c represents a notch size, such as a radius of a circular notch, and W represents a width of the notched component, which can be a dimension of the notched component in a direction of crack propagation, and l = a + c.

[0155] In one embodiment, determining the equivalent initial flaw size of the notched component from the long crack propagation threshold value of the notched component, the geometry factor, the fatigue notch factor, and the equivalent initial flaw size of the smooth component can include the following steps:

[0156] determining the intrinsic crack propagation threshold value of the notched component from the long crack propagation threshold value of the notched component and the material properties of the notched component;

[0157] determining the equivalent initial flaw size of the notched component from the intrinsic crack propagation threshold value of the notched component, the geometry factor, the fatigue notch factor, and the equivalent initial flaw size of the smooth component.

[0158] where the following relationship holds when considering the non-conservative EIFS value of the real specimen:

[0159]

[0160] The minimum intrinsic resistance to microcrack propagation (microstructural threshold AK th,eff ) is defined as a function of the plane (intrinsic) fatigue limit AS smooth,e and the most resistant microstructural obstacle size d ph , and is given by the following functional expression:

[0161]

[0162] To account for the temperature sensitivity of the nickel-based single crystal microstructure, and to cut two phases differently according to temperature, d dh may be defined as the size of the matrix phase or the strengthening phase at different temperatures, depending on which component phase the dislocation first appears in. Further, it can be derived that:

[0163]

[0164] where AK th,eff represents the intrinsic crack propagation threshold value of the notched component, AK th,l represents the long crack propagation threshold value of the notched component, d ph represents the most resistant microstructural obstacle size determined from the material properties of the notched component, such as the size of the matrix phase or the strengthening phase for a nickel-based single crystal, and a 0,l represents a transition crack size determined from the smooth component. The intrinsic crack propagation threshold value of the notched component can be calculated by equation (30).

[0165] Reference Figure 11 As shown in Fig. 13, the modified K-T of real specimen can be described as a parallel segment, which represents the difference of macro-crack nucleation under the effect of notch crack coupling coefficient. For ideal pure notch structure, the critical notch depth a p is the intersection of ΔK th,l and Δσ smooth，e / K t , i.e.:

[0166]

[0167] The actual critical notch depth is:

[0168]

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

[0170]

[0171] Since the plastic zone size of crack in this scale range cannot be ignored, in order to simplify, the plastic zone at the crack tip in two-dimensional mode can be modified to meet the conditions of linear elastic fracture mechanics. The effective plastic zone size r d of nickel-based single crystal material can be solved by experiment and numerical solution, and the coincidence degree is very high. The surface of the component will produce more plastic than the inside, and when the two-dimensional anisotropic material is in plane stress state (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 and y axes, the above formula can be further expressed as:

[0174]

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

[0176]

[0177] In one embodiment, determining the equivalent initial flaw size of the notched component based on the intrinsic crack propagation threshold value, the geometric factor, the fatigue notch factor of the notched component, and the equivalent initial flaw size of the smooth component can include the following steps:

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

[0179] calculating the equivalent initial flaw size of the notched component by the following equation:

[0180]

[0181] where EIFS mod,notch represents the equivalent initial flaw size of the notched component, K t / λ represents the fatigue notch factor of the notched component, ΔK th,eff represents the intrinsic crack propagation threshold value of the notched component, η represents the plastic zone correction factor of the notched component, Δσ0 represents the safe fatigue limit of the smooth component, and F(aη) represents the geometric factor of the notched component, which can be calculated by equation (27).

[0182] Further derivation of equation (37) can be obtained as follows:

[0183]

[0184] It should be noted that ΔK th,eff is essentially a basic property of the material, and for the same process, ΔK th,eff can be considered as constant, 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 at the hole edge change, resulting in inconsistent ΔK th,eff , at this time, it needs to be evaluated separately, and the EIFS of the notched component determined under normal temperature conditions can be used to further deduce ΔK th,eff under different temperature conditions.

[0185] Figure 12A EIFS values under different survival rates are shown, Figure 12B linear descriptions of the notched components based on the EDM process under different survival rates and crack geometry correction factors are shown, Figure 12C linear descriptions of the notched components based on the LDM process under different survival rates and crack geometry correction factors are shown. As Figure 12AAs shown, the EIFS values of the notched components prepared by EDM and LDM are quite different, and the EIFS value of EDM is about 0.022 mm and that of LDM is about 0.047 mm at 95% assurance rate and 50% survival rate. According to the test data meeting different survival rates (0-100%), the EIFS value of EDM is between 0.0188-0.0273 mm, and the EIFS value of LDM is between 0.0423-0.0530 mm. When a certain stress is applied, the interval range of the calculated EIFS will be further reduced, and the interval change of EDM and LDM is approximately within 0.01 mm. It should be noted that when considering three stress levels (the stress level changes more than 20%), the interval peak value (maximum value and minimum value) of EIFS only increases by about 2%, which can be ignored compared with the common calculation method that the EIFS value is closely related to the stress size. Under different survival rates, the EIFS value and the survival rate and the crack geometry correction factor meet a strong linear relationship, and the crack geometry correction factor also only changes slightly (for example, F is maintained at about 1.53 in Figure 12B the above). After determining the specific correlation function, it is more valuable to predict the universality of EIFS for engineering practice.

[0186] With reference to Figure 1 , in step S130, according to the second test data, the equivalent stress intensity factor difference and the fatigue crack propagation rate of the notched component under high temperature condition are obtained; 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 considering various types of crack propagation driving forces in the notched component.

[0187] In the present exemplary embodiment, the stress intensity factors under the action of various types of crack propagation driving forces in the component are considered comprehensively, and are expressed as the equivalent stress intensity factor K eq , and the stress intensity factor related parameters such as the equivalent stress intensity factor effective value and the equivalent stress intensity factor threshold value are calculated. The equivalent stress intensity factor is described below.

[0188] Figure 13A A schematic diagram of the component geometric coordinate system and the random crack propagation 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] where σ ij (r, θ) represents the stress tensor in the component geometric coordinate system, r is the distance to the crack tip in the vertical plane, and θ is the included angle of the crack propagation direction; f ij(θ), g ij (θ), h ij (θ) is a geometric function used to define the geometric angular dependence of the stress field; K I K Ⅱ K Ⅲ These are the stress intensity factors for pure Type I (tensile), Type II (shear), and Type III (tear) stresses. 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 factors, the stress fields at the tips of pure Type I (tensile) cracks, Type II (shear) cracks, and Type III (tear) cracks are superimposed to obtain the three-dimensional stress field at the crack tip.

[0191] A point on the random crack propagation surface is 100° away from the crack tip. Its spatial position can be determined by the angles α, β, and γ between it and the three coordinate axes. Ignoring the stress field variation along the z-axis within a small range, the distance r' on the random crack propagation surface can be projected onto the crack perpendicular plane, as shown below:

[0192]

[0193] Furthermore, we can obtain:

[0194] θ=arctan(cosβ / cosγ) (41)

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

[0196]

[0197] The shear stress intensity factor in different directions can be obtained from the stress field on the random crack propagation surface. Let the unit normal vector on the random crack propagation surface be n, the unit vector on the plane be s, and the shear unit vector be t. According to spatial relationships, t = n × s. It is important to note that the vector s can be projected onto the three coordinate axes of the geometric coordinate system, and its component matrix is ​​(s... x ,s y ,s z ).

[0198] After the crystal plane crack appears, the equivalent stress intensity factor k I k Ⅱ k Ⅲ They will appear simultaneously, corresponding to the three directions of crystal slip (or the three principal axes of the local slip coordinate system, denoted as m, n, and z). (See reference) Figure 13B As shown, kI The driving force is the normal vector n of the crystal plane, k Ⅱ For a crystal plane acting on vector s, k Ⅲ This is due to the action of vector t. Therefore, in the slip frame (SS)... ω Vectors n, s, and t can be considered as the unit normal vectors (SN) of the crystal slip plane (SP). ω unit vector of slip direction (SD) m ω and z ω (z ω =n ω ×m ω ).

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

[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 perpendicular to the crack plane I K Ⅱ K Ⅲ Between, satisfy Multiple relationship, that is:

[0205]

[0206] Octahedral slip systems are generally considered as potential crystal plane cracks after the crack transforms from a Mode I crack. The crystal crack is considered to be driven on the {111} slip plane, and the driving force of the oblique crack is considered to be τ. rss and τ rns The combined effect results in the equivalent stress intensity factor k of the crystal slip plane. eq Can be Figure 13C A schematic diagram of the crack tip coordinate system x'-y'-z' is shown. Since the y' axis is parallel to the crystal plane normal vector n in the crack tip coordinate system... ω Then δ = 0. The equivalent stress intensity factor k of the crystal slip plane. eq It can be represented as follows:

[0207]

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

[0209]

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

[0211]

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

[0213] As can be seen from the above, there can be different types of crack propagation driving forces in the component, and the fatigue crack propagation rate will be affected by these factors. The following is analyzed.

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

[0215] Due to the so-called environmental assisted cracking in polycrystalline superalloys, the fatigue crack propagation rate is accelerated by several orders of magnitude under long time loading and air conditions. Its main mechanism is: stress assisted grain boundary oxidation and dynamic oxidation. In addition to the two mechanisms commonly existing, another oxygen-related fatigue mechanism of single crystal superalloy is sometimes considered, that is, the oxidation-induced crack closure effect (or simply referred to as the oxidation closure effect). Compared with the vacuum condition, the propagation speed of the near-threshold crack is greatly slowed down. The oxide with a thickness equivalent to the crack opening displacement (COD) is considered to form inside the crack, thereby reducing the effective value of the stress intensity range factor and the crack propagation rate. The crack opening schematic diagram during fatigue loading can be referred to as Figure 14As shown in the diagram, experimental observations indicate that the cracks at high temperatures exhibit a circular crown shape, with oxygen filling the entire crack and causing the crack tip to become blunt. Typically, the oxides within the crack are considered to be formed by "fretting oxidation," meaning that the oxides continuously fracture and reform under cyclic loading, thus forming a continuous external oxide layer. When the loading frequency is changed, high-frequency tests more easily cause the oxides to repeatedly fracture, resulting in partial oxide closure. Low-frequency tests, on the other hand, are more conducive to the formation of thick and continuous oxides.

[0216] refer to Figure 14 As shown, for the continuous oxidation-induced crack closure effect, the following simplified assumptions can be made: ①δ max It depends only on the maximum load and is not affected by oxidation. ② Assuming the oxide is a rigid body, δ min This is equal to the thickness of the external oxide layer. ③ The thickness of the external oxide layer is taken as the average oxide thickness within 10 μm after the crack tip. Oxygen intrusion into the material forms an internal oxide layer, which has little impact on crack opening. Based on the oxide thickness, the effective value of the stress intensity range factor is calculated using the following formula:

[0217] ΔK eff =K max -K i (50)

[0218] Among them, K max K is the stress intensity factor under maximum load. i This is the stress intensity factor for oxidation closure, which can be the stress intensity factor when the crack flank comes into contact with oxide.

[0219] Generally, when the crack surface contacts oxides, the cyclic strain-stress during the unloading phase exhibits a slope change. The stress intensity factor corresponding to the inflection point is K. i Because the closure of local cracks has a relatively small impact on the overall mechanical response of the material, especially in the initial stage of crack propagation tests, the inflection point is difficult to distinguish. This inflection point is precisely 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 Figure 14 As shown, due to oxygen intrusion, the crack tip becomes blunt and forms a unique round shape, unlike a normal sharp crack tip. Therefore, calculation methods for sharp crack tips are difficult to accurately calculate COD; for example, using the 90° intersection line method may overestimate COD. (Reference) Figure 14 A schematic diagram for evaluating COD is shown. Considering the initial contact between the crack surface and the oxide, the COD at 10 μm behind the crack tip can be calculated by the following formula:

[0220]

[0221] Here, δ CODL is the thickness of the external oxide layer at 10 μm Oxi represents the length of the external oxide layer, which can be measured by a SEM (scanning electron microscope) or the like COD L is the thickness of the external oxide layer at 10 μm Oxi , and then δ Oxi is calculated. Further, the relationship between δ Oxi and K i is established, so that K i is solved, with reference to the following formula:

[0222]

[0223]

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

[0225] Thus, according to the measured thickness of the closed oxide at 10 μm of the crack tip, the actual δ Oxi can be obtained, and on this basis, K i and ΔK eff can be calculated.

[0226] In one embodiment, the difference between the equivalent stress intensity factors of the notched member under high temperature conditions can be determined in the following manner:

[0227] According to the second test data, the equivalent stress intensity factor effective value of the notched member under high temperature conditions, and the long crack propagation threshold value and the intrinsic crack propagation threshold value of the notched member under high temperature conditions are determined;

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

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

[0230] wherein based on the above analysis, the fatigue crack propagation rate can be represented by the following formula:

[0231]

[0232] C and m are coefficients, which can be obtained by fitting. ΔK eq,eff is the equivalent stress intensity factor effective value (unit: MPa·m 1 / 2), is the effective value of stress intensity factor considering various types of crack propagation driving forces in the notched component. ΔK th,eq is the equivalent stress intensity factor threshold value (unit: MPa·m 1 / 2 ), is the threshold value range considering the long-short crack variation of EIFS. ΔK eq,eff - ΔK th,eq is the equivalent stress intensity factor difference value.

[0233] First, how to determine the equivalent stress intensity factor threshold value is described below.

[0234] In an embodiment, the equivalent stress intensity factor threshold value of the notched component under high temperature conditions is obtained according to the long crack propagation threshold value of the notched component under high temperature conditions and the intrinsic crack propagation threshold value, which can include the following steps:

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

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

[0237] The equivalent stress intensity factor threshold value ΔK th，eq can be calculated according to the following formula:

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

[0239]

[0240] wherein, ΔK th,l is the long crack propagation threshold value, ΔK th,eff is the intrinsic crack propagation threshold value, ΔK th,change is the transition stress intensity factor threshold value, a represents the crack size, and d is the strongest microstructure obstacle size. d is defined as the size of the matrix phase or the strengthening phase at different temperatures, which depends on whether the dislocation first appears in which component phase, considering the temperature sensitivity of the microstructure of the nickel-based single crystal, and the d here can be defined as the size of the matrix phase or the strengthening phase at different temperatures. EIFS notch,modThis represents the equivalent initial defect size of the notched component. It should be understood that, in order to determine the equivalent stress strength factor threshold value of the notched component under high-temperature conditions, the above formula requires parameters such as the long crack propagation threshold value, the intrinsic crack propagation threshold value, and the equivalent initial defect size at high temperatures.

[0241] It should be noted that due to the intrinsic properties of the material and uncontrollable factors during the testing process, reference... Figure 15 As shown, the actual assessed original damage state (such as the size of the fatigue initiation zone, differences in stress concentration, etc.) and fatigue limit (such as Δσ) are different. e , Δσ th etc.), crack propagation threshold (e.g., ΔK) th,l ΔK th,eff All of these (e.g., P) have a certain probability distribution.

[0242] In one implementation, the long crack propagation threshold can be obtained using the ASTM E399 standard (Standard for Determination of Plane Strain Fracture Toughness of Metallic Materials). Based on test studies, the results show that the values ​​are within the range of 0.85 for log-normal, normal, and generalized extreme value distributions, where the P value of the Weibull distribution is... KS The value magnitude is significantly enhanced. In other words, the Weibull distribution is better suited to describe ΔK. th,l The discrete case.

[0243] At this point, the fatigue limit magnitude that varies with crack size in stage II can be expressed as:

[0244]

[0245] Based on formula (57), the ΔK of the material can be calculated. th,l ΔK th,eff The EIFS (or a0) values ​​of the distributed, smooth components are used to calculate Δσ. th (P). Conversely, Δσ can be obtained directly from the experiment. th (P), ΔK is calculated using formula (57). th,l or ΔK th,eff The fatigue crack propagation rate fitting form considering the probability distribution also has a certain probability distribution, such as... Figure 16 As shown, 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] From formula (57), we can obtain that when a = EIFS, that is, Δa = 0, Δσ th (P) Only related to ΔK in the long crack stage th,l (P) related, Δσ th (P) can be determined from the PSN curve, ΔK th,l(P) can be obtained from the crack growth curve measured by the test.

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

[0248]

[0249]

[0250] In one embodiment, the second test data includes the elastic modulus of the notched member around the notch under high temperature conditions. The DIC (Digital Image Correlation) technique can be used to measure the in-situ strain results around the notch (e.g., at a distance of 0.1 mm from the notch edge) and to analyze and calculate. Correspondingly, the long crack propagation threshold of the notched member under high temperature conditions can be determined by the following method:

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

[0252] Where the crack propagation data observed under high temperature conditions is unstable. Referring to Figure 17A , to determine the ΔK th,l (P) of the high temperature material, considering the dislocation distance from the crack tip as ρ and the angle ψ with the dislocation movement rate v under shear stress τ, based on the Yokobori model, the maximum force to drive crack propagation is generally the external force f τ and the mirror force f i . Other forces caused by surface energy can be ignored. Since it behaves as I-type crack propagation in the long crack propagation threshold region, the expressions of the two forces are:

[0253]

[0254] Assuming Figure 17A satisfies ψ = 0° and φ = 90°, for the FCC (Face-Centered Cubic) structure of the nickel-based single crystal, under repeated fatigue load, spontaneous dislocation will occur at the crack tip. In this way, the crack tip radius at the opening of the crack root is equal to 2n|b|, n is the number of dislocations, and b is the Burgers vector, then the fatigue crack propagation rate is equal to δ / 2. As shown in Figure 17B and Figure 17C , there is the following relationship:

[0255]

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

[0257]

[0258] Further, the crack tip extension direction caused by slip can be at an angle of 45° with the crack propagation direction, as shown in Figure 17B Under a plane stress state, the crack tip displacement can be referenced to the following formula:

[0259]

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

[0261]

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

[0263] Table 3

[0264]

[0265] The intrinsic crack propagation threshold value ΔK th,eff can also be obtained through the crack propagation test cyclic cracking program. In an embodiment, the intrinsic crack propagation threshold value can also be calculated by the following formula:

[0266]

[0267] wherein Z(R) is a crack opening description equation, R is a stress ratio, and A and B are obtained by fitting. A can also be a 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] Where, σ max To determine the maximum stress in the test, σ Y σ is the yield strength of the material. U ε represents the ultimate tensile strength, and all are material constants. ε is a material fitting parameter with a value range of 1 to 3.

[0271] For nickel-based single-crystal superalloys, the intrinsic crack propagation threshold and elastic modulus satisfy the following relationship:

[0272]

[0273] Where ΔK th,eff (P) represents the intrinsic crack propagation 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 propagation threshold value of smooth or notched components under normal temperature or high temperature conditions.

[0274] For representative oxidation permeation under high-temperature conditions (such as 900℃, 980℃), please refer to [reference needed]. Figure 19 As shown, energy dispersive spectroscopy (EDS) spectra of the corresponding elements Ni, Co, Al, Ta, W, O, and Cr can be observed at the crack geometry of the multi-origin crack at the notch edge. Two distinct oxide layers exist: the outer layer is rich in Cr, while the inner layer is rich in Al. Between them lies a thin but measurable Ta- and W-rich oxide layer. Furthermore, the magnified SEM images provide evidence of a γ'-γ phase transition induced by Al atom diffusion to form Al-rich oxides. This leads to the formation of a γ' phase consumption region and changes in the microstructure of the γ' / γ layer below the oxide layer (near the crack face, beyond the crack tip, and in the near-surface region). Additionally, the observation of a distinct internal oxide layer at the crack tip leading to crack closure confirms the above findings. Figure 14 Partial 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 with different survival rates can be calculated. th,eff and fatigue limit Δσ e Considering only EIFS 95 / 95 At 900℃, the ΔK values ​​of the EDM and LDM of plate sample 1 are... th,eff The values ​​are 4.748 and 4.923 (unit: MPa·m). 1 / 2), and 4.697 and 5.030 (in units of MPa-m 1 / 2 ), and the hole edge crack length is in the range of 1.5 mm to satisfy the linear crack propagation interval.

[0276] In the case of determining the long crack propagation threshold value of the notched member at high temperature and the intrinsic crack propagation threshold value, the difference between the two can be obtained as the transition stress intensity factor threshold value of the notched member at high temperature. Then, the intrinsic crack propagation threshold value of the notched member at high temperature, the transition stress intensity factor threshold value, and the equivalent initial defect size of the notched member are brought into formula (55) to calculate the equivalent stress intensity factor threshold value ΔK th,eq .

[0277] The above explains how to determine the equivalent stress intensity factor threshold value. In an embodiment, the second test data includes a crack tip opening parameter of the notched member at high temperature; and an equivalent stress intensity factor effective value of the notched member at high temperature, which is determined by the following way:

[0278] According to the crack tip opening parameter, the yield strength, the ultimate tensile strength, and the Young's modulus of the notched member under plane stress, the oxidation closure stress intensity factor of the notched member at high temperature is determined; the oxidation closure stress intensity factor is the stress intensity factor when the crack flanks contact the oxide;

[0279] According to the stress intensity factor under the maximum load of the notched member at high temperature and the oxidation closure stress intensity factor, the equivalent stress intensity factor effective value is determined.

[0280] wherein the reference Figure 14 and formula (51), the crack tip opening parameter can include the external oxide layer thickness and the external oxide layer length, which can be measured by test. For example, the crack propagation test and the high cycle fatigue test of the notched member at high temperature can be observed at different stages, and the external oxide layer thickness δ COD at 10 μm behind the crack tip and the entire external oxide layer length l at the stage of crack tip blunting are measured, and δ Oxi is calculated by formula (51). Then, the oxidation closure stress intensity factor K i is calculated by formula (52) and (53). Further, by formula (50), K eff is replaced by K eq , and the equivalent stress intensity factor effective value ΔK eq,eff is obtained by simultaneous solution.

[0281] With reference to the foregoing Figure 1In step S140, the crack propagation function is obtained by fitting the function relationship between the fatigue crack propagation rate, the equivalent stress intensity factor difference, and the crack size of the notched member under high temperature conditions. The crack propagation function represents the function relationship between the fatigue crack propagation rate and the crack size.

[0282] In one embodiment, the crack propagation function obtained by fitting the function relationship between the fatigue crack propagation rate, the equivalent stress intensity factor difference, and the crack size of the notched member under high temperature conditions can include the following steps:

[0283] A first function relationship is obtained by fitting the function relationship between the equivalent stress intensity factor difference and the crack size of the notched member under high temperature conditions.

[0284] A second function relationship is obtained by fitting the function relationship between the fatigue crack propagation rate and the equivalent stress intensity factor difference.

[0285] The crack propagation function is obtained by combining the first function relationship and the second function relationship.

[0286] In the formula, ΔK eq,eff According to the finite element calculation, it is impossible to reflect the relationship between the equivalent stress intensity factor difference (ΔK eq,eff -ΔK th,eq ) and the crack size a by a specific function expression. In order to reflect the relationship between the equivalent stress intensity factor difference (ΔK notch,mod -ΔK 95 / 95 ) and the crack size a, the calculated results are fitted by a third-order function. The crack propagation data under different stresses under the same process can be unified, and the crack propagation description model in the present exemplary embodiment is used to set EIFS Figure 20A The first function relationship is obtained by fitting the results in logarithmic coordinates in an exponential form. Figure 20A In the formula, EDM Plate1-3 900℃ represents the flat plate 1 member based on the EDM hole making process, effective sample 3, tested under high temperature conditions at 900℃. ①②③④ are four kinds of conditions of fracture mode, and the goodness of fit is 0.99. Similarly, the function relationship between the fatigue crack propagation rate and the equivalent stress intensity factor difference can be fitted, and the fitting results can be referred to in Figure 20B The second function relationship is obtained. Figure 20B In the formula, ①②③ are three kinds of stress intensity factor calculation modes.

[0287] As can be seen from Figure 20A , the equivalent stress intensity factor difference (ΔK eq,eff -ΔK th,eqThe third order function relationship between the crack size a can be used to describe the whole crack path propagation, however, the separation degree of the LDM specimen of the flat plate 2 at 900℃ is larger than the other three forms, which is mainly due to that it directly cracks on the crystal surface until fracture, which can cause relatively less crack driving force required in the initial stage of the crack, in other words, the energy required for pure crystal surface crack initiation is relatively less than the I type crack. It can be seen from Figure 20B that the exponential relationship between the fatigue crack propagation rate da / dN and the equivalent stress intensity factor difference (ΔK eq,eff -ΔK th,eq ) is also relatively strong, and the crack propagation rate of the LDM specimen of the flat plate 2 at 900℃ is roughly at the same level as the other three forms, which further illustrates that the crack driving force of the nickel-based single crystal under different geometric component forms and temperatures is significantly different. Considering the ΔK I resulted from the joint action of K II , K III and K eq,eff under oxidation, it can accurately reflect the crack propagation, especially the propagation in the small crack stage. At this time, the proportion of K III in ΔK eq,eff is close to 40%, which is generally comparable to the proportion of K I at room temperature. The flat plate 1 and the flat plate 2 have a relatively obvious size effect after changing the size, showing the inconsistency of crack propagation. Although the crack propagation path and the material strength change significantly at 980℃ and 900℃, the fatigue crack propagation rate does not change significantly, which may be due to the fact that the influence of high-temperature oxidation on the crack behavior is not significantly different at high temperature.

[0288] By combining the first function relationship and the second function relationship, the function relationship between the fatigue crack propagation rate da / dN and the crack size a, i.e., the crack propagation function, can be obtained.

[0289] With reference to Figure 1 , in step S150, based on the crack propagation function, the equivalent initial defect size of the notched component and the limit crack size, the predicted fatigue life of the notched component under high-temperature conditions is determined.

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

[0291] integrating the crack propagation function with the equivalent initial defect size of the notched component as the lower limit of integration and the limit crack size of the notched component as the upper limit of integration to obtain the predicted fatigue life of the notched component under high-temperature conditions.

[0292] Wherein, the crack propagation function is the fatigue crack propagation rate represented by the crack size as the independent variable, and the fatigue life calculation can refer to the following formula:

[0293]

[0294] Wherein, a c represents the limit crack size, which can be observed by a microscope or calculated by fracture toughness.

[0295] The equivalent initial defect size of the notched member is taken as the lower limit of integration, and the limit crack size of the notched member is taken as the upper limit of integration, and the crack propagation function is integrated, thereby calculating the fatigue life of the whole cycle of crack propagation as the predicted fatigue life. The prediction result has high accuracy.

[0296] Figure 21 A comparison chart of predicted fatigue life and test fatigue life is shown. Without introducing oxidation correction effect, the error between the test data and the prediction results of the improved K-T 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, crack initiation time) method, the dispersion of the present scheme is smaller (there are obvious upper and lower error lines in the figure), and the data is more concentrated. Mainly because the improved EIFS solution fully considers the local ΔK th,eff of the structure, and can be directly related to the macro mechanics of the whole structure, which is more stable than ΔK th,l reflected from the crack propagation data. It can be further pointed out that the transition stress intensity factor threshold ΔK th,change gradually changes with the increase of crack length, and after introducing the integral function (i.e. crack propagation function), the sharp change of fatigue life caused by the direct change of the lower limit of integration can be gradually offset. After introducing the oxidation correction effect, the oxidation closure effect acting on the crack tip reduces the effective stress intensity factor of crack propagation, thereby reducing the fatigue crack propagation rate and increasing the fatigue life. As can be seen from the figure, the prediction result is greatly improved, the error between the test data and the prediction result is within the range of 4 times the dispersion band, and most of them are within the range of 3 times.

[0297] In addition, Figure 21The fatigue life prediction results under normal temperature conditions are also shown. It can be seen that the fatigue life prediction error bands of the samples based on EDM and LDM drilling processes under normal temperature conditions are within 2 times. A very important factor for obtaining this result is that the crack observation results under normal temperature conditions are accurate and the environment is relatively high. The EIFS determined under normal temperature conditions may fluctuate due to changes in the environment under high temperature conditions, such as creep-like effects caused by long-term effects, which in turn affect the crack propagation rate, and the environment may also cause damage to the original component coupling and the like. However, the method of the present exemplary embodiment determines the EIFS of the smooth specimen, and then determines the normal temperature EIFS of the notched component, and finally predicts the high temperature fatigue life, which provides a new idea and achieves good accuracy.

[0298] The exemplary embodiments of the present disclosure also provide an EIFS-based high temperature fatigue life prediction device. Referring to Figure 22 As shown, the device 2200 can include the following program modules:

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

[0300] The first determination module 2220 is 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;

[0301] The second determination module 2230 is configured to obtain the equivalent stress intensity factor difference and the fatigue crack propagation 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 effective value of the equivalent stress intensity factor and the threshold value of the equivalent stress intensity factor considering various types of crack propagation driving forces in the notched component;

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

[0304] The specific details of each part of the above-mentioned device have been described in detail in the method section of the implementation plan. For any undisclosed details, please refer to the implementation plan of the method section, and therefore will not be repeated here.

[0305] It should be noted that although several modules or units for the device used to perform actions have been mentioned in the detailed description above, this division is not mandatory. In fact, according to exemplary embodiments of this 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 and embodied by multiple modules or units.

[0306] Exemplary embodiments of this disclosure also provide a computer program product. The computer program product includes a computer program that, when executed by a processor, implements the above-described EIFS-based high-temperature fatigue life prediction method.

[0307] In one embodiment, the computer program product can be a tangible product containing a computer program, such as a computer-readable storage medium storing the computer program. The readable storage medium can 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, hard disk drive (HDD), solid-state drive (SSD), etc. For example, the computer program product can be implemented as a non-volatile storage medium storing the computer program, such as read-only memory, NAND flash memory, etc.

[0308] In one implementation, the computer program product can be an intangible product containing a computer program. For example, the computer program product can be implemented as a virtual digital product, such as an executable file, installation package, or other digital file storing the computer program.

[0309] Computer program code can be written in one or more programming languages. Examples of programming languages ​​include C, Java, and C++. Program code can execute entirely on the user's computing device, partially on the user's computing device, or as a standalone software package. It can also execute partially on the user's computing device and partially on a remote computing device, or entirely on a remote computing device or server. In cases involving remote computing devices, the remote computing device can be connected to the user's computing device via any type of network, such as a local area network (LAN) or a wide area network (WAN), or it can be connected to an external computing device (e.g., via an internet connection provided by a mobile network operator).

[0310] The computer program can be carried or transferred by an electric, magnetic, optical, electromagnetic, infrared or the like signal. The electronic device can convert the signal carrying the computer program into a digital signal, and then run the computer program. When the computer program is run on the electronic device, its code is used to make the electronic device perform (more specifically, can make the processor of the electronic device perform) 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 can include a processor and a memory. The memory stores executable instructions of the processor, such as a computer program. The processor performs the method steps of various exemplary embodiments of the present disclosure by executing the executable instructions. In addition, the electronic device can also include a display for displaying a graphical user interface.

[0312] The electronic device is exemplarily illustrated in the form of a general computing device below. Figure 23 It should be understood that, Figure 23 The displayed electronic device 2300 is only an example and should not limit the function and use range of the embodiments of the present disclosure.

[0313] As Figure 23 shown, the electronic device 2300 can 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 can include a volatile memory, such as a RAM 2321, a cache unit 2322, and a non-volatile memory, such as a ROM 2323. The memory 2320 can also include one or more program modules 2324, which include but are not limited to: an operating system, one or more application programs, other program modules, and program data, each of which or some combination thereof can include the implementation of a network environment. For example, the program modules 2324 can include the modules in the above-described apparatus.

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

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

[0317] The bus 2330 is configured to realize the connection between different components of the electronic device 2300, and can 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 (such as a keyboard, a mouse, an external controller, etc.) through the I / O interface 2340.

[0319] The electronic device 2300 can communicate with one or more networks through the network adapter 2350, such as a network adapter 2350 that can provide a mobile communication solution such as 3G / 4G / 5G, or provide a wireless communication solution such as a wireless local area network, 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 can display a graphical user interface through the display 2360.

[0321] Although Figure 23 Figure 23 Other hardware and / or software modules can 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 solutions of the present disclosure can be implemented as a method, an apparatus, a system, a computer program product, a storage medium, an electronic device, and the like. Those skilled in the art can understand that each aspect of the present disclosure can be implemented in the following forms: a complete hardware implementation, a complete software implementation (including firmware, microcode, etc.), or a combination of hardware and software aspects, such as a "circuit", a "module", or a "system".

[0323] It should be understood that the present disclosure is not limited to the particular examples of methods steps or structures described above and shown in the drawings, as various modifications and changes can be made thereto without departing from its scope. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the methods provided herein. Therefore, the specific embodiments provided in this disclosure are illustrative only and not intended to limit the scope of the disclosure, which is to be measured solely by reference to the claims, and any variations or modifications thereof, which come within the spirit and scope of the disclosure, along with their equivalents, are intended to be embraced by the claims.

Claims

1. A method for high-temperature fatigue life prediction based on EIFS, characterized by, The method comprises the following steps: obtaining first test data of crack propagation test and high-cycle fatigue test of a smooth component, and second test data of crack propagation test and high-cycle fatigue test of a notched component; the second test data comprises test data under high-temperature conditions; determining equivalent initial defect sizes of the smooth component and the notched component according to the first test data and the second test data; obtaining an equivalent stress intensity factor difference value and a fatigue crack propagation rate of the notched component under high-temperature conditions according to the second test data; the equivalent stress intensity factor difference value is a difference between an effective value of the equivalent stress intensity factor and a threshold value of the equivalent stress intensity factor of various types of crack propagation driving forces in the notched component; obtaining a crack propagation function by fitting a functional relationship among the fatigue crack propagation rate, the equivalent stress intensity factor difference value and a crack size of the notched component under high-temperature conditions; the crack propagation function represents a functional relationship between the fatigue crack propagation rate and the crack size; determining a predicted fatigue life of the notched component under high-temperature conditions based on the crack propagation function, the equivalent initial defect sizes of the notched component and a limit crack size.

2. The method of claim 1, wherein, The equivalent stress intensity factor difference value of the notched component under high-temperature conditions is determined by the following steps: determining an effective value of the equivalent stress intensity factor of the notched component under high-temperature conditions, and a long crack propagation threshold value and an intrinsic crack propagation threshold value of the notched component under high-temperature conditions according to the second test data; obtaining a threshold value of the equivalent stress intensity factor of the notched component under high-temperature conditions according to the long crack propagation threshold value and the intrinsic crack propagation threshold value of the notched component under high-temperature conditions; obtaining the equivalent stress intensity factor difference value based on a difference between the effective value of the equivalent stress intensity factor and the threshold value of the equivalent stress intensity factor.

3. The method of claim 2, wherein, The second test data comprises a crack tip opening parameter 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 steps: determining an oxidation closure stress intensity factor of the notched component under high-temperature conditions according to the crack tip opening parameter, a yield strength, a limit tensile strength and a Young's modulus under plane stress of the notched component; the oxidation closure stress intensity factor is a stress intensity factor when a crack flank contacts an oxide; determining the effective value of the equivalent stress intensity factor according to a stress intensity factor under a maximum load and the oxidation closure stress intensity factor of the notched component under high-temperature conditions.

4. The method of claim 2, wherein, The second test data comprises an elastic modulus around a notch of the notched component under high-temperature conditions; the long crack propagation threshold value of the notched component under high-temperature conditions is determined by the following steps: determining the long crack propagation threshold value of the notched component under high-temperature conditions according to the elastic modulus, a yield strength of the notched component under high-temperature conditions and the fatigue crack propagation rate.

5. The method of claim 2, wherein, The equivalent stress intensity factor threshold value of the notched component under high temperature condition is obtained according to the long crack propagation threshold value and the intrinsic crack propagation threshold value of the notched component under high temperature condition, and includes: The transition stress intensity factor threshold value of the notched component under high temperature condition is obtained according to the difference between the long crack propagation threshold value and the intrinsic crack propagation threshold value of the notched component under high temperature condition; The equivalent stress intensity factor threshold value of the notched component under high temperature condition is determined according to the intrinsic crack propagation threshold value and the transition stress intensity factor threshold value of the notched component under high temperature condition, and the equivalent initial defect size of the notched component.

6. The method of claim 1, wherein, The crack propagation function is obtained by fitting the functional relationship between the fatigue crack propagation rate, the equivalent stress intensity factor difference value and the crack size of the notched component under high temperature condition, and includes: The first functional relationship is obtained by fitting the functional relationship between the equivalent stress intensity factor difference value and the crack size of the notched component under high temperature condition; The second functional relationship is obtained by fitting the functional relationship between the fatigue crack propagation rate and the equivalent stress intensity factor difference value; The crack propagation function is obtained by combining the first functional relationship and the second functional relationship.

7. The method of claim 1, wherein, The predicted fatigue life of the notched component under high temperature condition is determined based on the crack propagation function, the equivalent initial defect size of the notched component and the limit crack size, and includes: The predicted fatigue life of the notched component under high temperature condition is obtained by integrating the crack propagation function with the equivalent initial defect size of the notched component as the lower limit of integration and the limit crack size of the notched component as the upper limit of integration.

8. The method of claim 1, wherein, 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, and include: The long crack propagation threshold value of the notched component, the long crack propagation threshold value of the smooth component, the fatigue limit and the fatigue source area ellipse geometric parameter of the smooth component are obtained according to the first test data and the second test data; The equivalent initial defect size of the smooth component is determined according to the long crack propagation threshold value and the fatigue limit of the smooth component; The fatigue source area equivalent circle parameter is determined according to the fatigue source area ellipse geometric parameter of the smooth component; The fatigue notch factor of the notched component is determined 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 propagation threshold value, the geometric shape factor, the fatigue notch factor of the notched component and the equivalent initial defect size of the smooth component.

9. An apparatus for high-temperature fatigue life prediction based on EIFS, characterized by, It includes: The test data acquisition module is configured to acquire first test data of crack propagation test and high cycle fatigue test on a smooth component, and second test data of crack propagation test and high cycle fatigue test on a notched component; the second test data includes test data under high temperature condition; a first determining module configured to determine an equivalent initial defect size of the smooth member and an equivalent initial defect size of the notched member according to the first test data and the second test data; a second determining module configured to obtain an equivalent stress intensity factor difference and a fatigue crack propagation rate of the notched member under high temperature condition 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, which are comprehensively considered for various types of crack propagation driving forces within the notched member; a third determining module configured to obtain a crack propagation function by fitting a functional relationship among the fatigue crack propagation rate, the equivalent stress intensity factor difference, and a crack size of the notched member under high temperature condition; the crack propagation function represents a functional relationship between the fatigue crack propagation rate and the crack size; a fourth determining module configured to determine a predicted fatigue life of the notched member under high temperature condition based on the crack propagation function, the equivalent initial defect size of the notched member, and a limit crack size.

10. An electronic device, comprising: comprise: a processor; a memory for storing executable instructions of the processor; wherein the processor is configured to execute the method according to any one of claims 1 to 8 by executing the executable instructions.

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