Metal material fatigue crack propagation life prediction method based on crack propagation entropy

Abstract

The application discloses a metal material fatigue crack propagation life prediction method based on crack propagation entropy, and comprises the following steps: defining a local area as a thermodynamic system; obtaining stress tensor, strain tensor and temperature evolution data in a plastic zone of a crack tip under an initial crack length, and calculating time entropy production rate and cycle entropy production rate; increasing crack length increment or cycle life increment; calculating cycle entropy production rate of the plastic zone of the crack tip after crack propagation; repeatedly implementing the crack propagation process and corresponding calculation until fracture failure or the crack propagation reaches a given length; establishing a cycle entropy production rate and cycle life function relationship, calculating crack propagation entropy at different crack propagation moments; constructing entropy production-damage parameters, establishing an entropy production-damage parameter and life consumption evolution law, and predicting crack propagation life based on the evolution law. The method is suitable for low-cycle and high-cycle fatigue crack propagation life prediction of metal materials, and has important theoretical research significance and engineering application value.

Description

TECHNICAL FIELD

[0001] The present application relates to metal material crack propagation life analysis, and in particular to a metal material fatigue crack propagation life prediction method based on crack propagation entropy. BACKGROUND

[0002] Structural fatigue caused by cyclic loading is one of the most common failure forms in engineering structures, and the essence of fatigue is an irreversible thermodynamic dissipation process, in which the structural damage of metal materials continuously accumulates with the continuous loading of cyclic loading until the structure fails. During the fatigue damage accumulation process of metal materials, the input of mechanical energy causes irreversible energy dissipation, which increases the irreversibility of the thermodynamic system, and the irreversibility of the damage accumulation process can be quantified by the entropy production of thermodynamics. Therefore, the entropy production of thermodynamics can be used as a measure of material fatigue damage.

[0003] At present, the idea of studying fatigue problems based on the theory of entropy production of thermodynamics has attracted widespread attention from scholars. However, existing related researches mainly focus on the failure life of fracture, especially the analysis of crack initiation life, and rarely concern the life prediction of crack propagation stage. The existing research on crack initiation life based on the entropy production of thermodynamics mainly includes two types: one is to measure the macroscopic temperature field evolution of the fatigue sample during the fatigue test, to indirectly represent the entropy production data of the crack initiation stage, and to analyze the crack initiation life based on the entropy production of thermodynamics; the other is to read the nominal stress and nominal strain data on the loading equipment, and to calculate the entropy production of the crack initiation stage combined with the temperature data of the fatigue sample, and then to analyze the crack initiation life. The above-mentioned crack initiation life analysis method based on the entropy production of thermodynamics does not concern the stress field and strain field information of the fatigue sample, and cannot reasonably reflect the mechanical response of the fatigue sample under cyclic loading.

[0004] In addition, the existing fatigue life research based on the theory of entropy production of thermodynamics does not involve crack propagation life analysis. In the research of crack initiation life, a specific gauge length section is usually analyzed, and it is considered that the stress and strain states of each point in the gauge length section are consistent. However, in the research of crack propagation, there is plastic deformation in the local area of the crack tip of the sample, and the other parts of the sample are still in the elastic state without yielding, which makes the existing research method of entropy production of thermodynamics have limitations in the research of crack propagation life.

[0005] Therefore, for the prediction and analysis of metal material crack propagation life, the present application proposes to use the concept of crack propagation entropy to describe the thermodynamic entropy production of metal materials in the crack propagation process, to extend the research of fatigue problems based on the theory of entropy production of thermodynamics to the field of metal material crack propagation, and to propose a metal material fatigue crack propagation life prediction method based on crack propagation entropy, which has important theoretical research significance and engineering application value. SUMMARY

[0006] The purpose of the present application is to provide a metal material fatigue crack propagation life prediction method based on crack propagation entropy, which can study the crack propagation problem of metal materials based on thermodynamic theory and predict the crack propagation life by using crack propagation entropy. The present application adopts the following technical scheme:

[0007] A metal material fatigue crack propagation life prediction method based on crack propagation entropy, comprising the following steps:

[0008] Step 1: define the local area containing the crack itself and the possible position of the plastic zone of the crack tip as a thermodynamic system;

[0009] Step 2: obtain the stress tensor, strain tensor and temperature evolution data in the plastic zone of the crack tip of the metal material under the action of cyclic load at the initial crack length through theoretical analysis, simulation or experiment, and calculate the time entropy production rate and the cyclic entropy production rate in the plastic zone of the crack tip based on the stress tensor, strain tensor and temperature evolution data;

[0010] Step 3: through theoretical analysis, simulation or experiment, the crack propagation Δa crack length increment or ΔN cycle life increment, and determine the corresponding ΔN cycle life increment or Δa crack length increment of the crack propagation;

[0011] Step 4: after the crack propagation Δa crack length increment or ΔN cycle life increment, obtain the stress tensor, strain tensor and temperature evolution data in the plastic zone of the crack tip of the metal material under the action of cyclic load, and calculate the time entropy production rate and the cyclic entropy production rate in the plastic zone of the crack tip corresponding to the crack length;

[0012] Step 5: repeat steps 3-4 until the metal material fails or the crack propagates to a given length;

[0013] Step 6: combine the cycle life increment data of the crack propagation to each crack length, and establish the function relationship between the cycle entropy production rate and the cycle life in whole or in segments, and sum or integrate the cycle entropy production rate to calculate the crack propagation entropy at different times;

[0014] Step 7: based on the crack propagation entropy, build the entropy production-damage parameter of the crack propagation process of the metal material, establish the evolution law of the entropy production-damage parameter and the life consumption, and predict the crack propagation life of the metal material based on the evolution law of the entropy production-damage parameter and the life consumption.

[0015] Further, in the step 1, the crack itself and the plastic zone of the crack tip always remain in the selected thermodynamic system during the entire crack propagation process.

[0016] Further, the stress tensor, strain tensor and temperature evolution data in the steps 2, 4 can be obtained by any one of the following methods or a combination of several methods: theoretical formula calculation, numerical simulation or fatigue experiment, to obtain the stress tensor, strain tensor and temperature evolution data in the plastic zone of the crack tip of the metal material under cyclic loading conditions.

[0017] Further, the time entropy production rate in the steps 2, 4 is calculated based on the obtained stress tensor, strain tensor and temperature evolution data, and is derived from the thermodynamic theory analysis by using the following formula to calculate the unit volume time entropy production rate of the microelement in the plastic zone of the crack tip:

[0018]

[0019] wherein, is the time entropy production rate, σ, T are the stress tensor, strain tensor change rate and temperature, and the mathematical form of the stress tensor and strain tensor change rate is different in the three-dimensional crack propagation problem and the two-dimensional crack propagation problem.

[0020] Further, the cyclic entropy production rate in the steps 2, 4 is obtained by selecting one or more load cycles, integrating the time entropy production rate in the loading time corresponding to the selected load cycle number by volume or area, and averaging the integral value over the selected load cycle number to obtain the unit volume cyclic entropy production rate:

[0021]

[0022] wherein, dω represents the time entropy production rate corresponding to the microelement volume or microelement area, Ω represents the volume or area of the plastic zone of the crack tip, is the cyclic entropy production rate, represents the specific volume entropy production in a single load cycle, and n and t(n) represent the selected load cycle number and the corresponding loading time, respectively, wherein n is a positive integer.

[0023] Further, the step 3 uses any one of the following methods or a combination of several methods: theoretical formula calculation, numerical simulation or fatigue experiment, to realize the crack propagation Δa crack length increment or ΔN cycle life increment, and determine the corresponding crack propagation ΔN cycle life increment or Δa crack length increment by the method used, to obtain the Δa-ΔN data corresponding to the crack propagation.

[0024] Furthermore, in step 5, any one or a combination of methods, such as theoretical formula calculation, numerical simulation, or fatigue experiment, is used to repeatedly implement the crack propagation in step 3 and the time entropy yield and cycle entropy yield calculation in step 4 until the metal material fractures or fails, or the crack length reaches a certain given length. When repeating step 3, the magnitude of the crack length increment Δa or the cycle life increment ΔN is allowed to vary during the repeated implementation process and is not required to be a constant value. The magnitude of Δa or ΔN can be changed according to the implementation requirements.

[0025] Furthermore, in step 6, the cyclic entropy yield is summed or integrated to calculate the crack propagation entropy at different times of crack propagation:

[0026] or

[0027] Among them, s g (N i The crack propagation time is N. i The crack propagation entropy at time N represents the crack propagation from the initial time to a cycle life of N. i The cumulative thermodynamic entropy production over time, where N0 is the initial crack propagation lifetime. and These represent cycle lifetimes of N and N, respectively. k and, N k+1 Cyclic entropy production rate, ΔN k+1 This indicates the crack's lifespan from cycle life N. k Extended to a cycle life of N k+1 The corresponding cycle lifetime increment, where k is a natural number less than i.

[0028] Furthermore, in step 7, the crack propagation entropy s at different times of crack propagation is... g (N) and the critical crack propagation entropy of metallic materials s c Constructing Entropy Production-Damage Parameters Wherein the critical crack propagation entropy s c It is the crack propagation entropy at the moment of crack propagation failure; based on the entropy production-damage parameter D s With lifespan consumption Based on the evolutionary data, the evolutionary laws governing lifetime consumption and entropy production-damage parameters are established, i.e. Crack propagation life can then be predicted using the following formula:

[0029]

[0030] Where N is the entropy production-damage parameter D s The corresponding cycle life, N f The crack propagation failure life.

[0031] Further, the step 7, for steel or aluminum alloy, the life consumption and the entropy production-damage parameter D s there is an approximate linear relationship between, namely Where k is a constant related to material properties, load; for nickel-based superalloy, the life consumption and the entropy production-damage parameter D s there is an approximate exponential relationship between, namely Where a, b and c are constants related to material properties, load.

[0032] The beneficial effects of the present application are:

[0033] (1) versatility: the present application based on the crack propagation entropy of metal material fatigue crack propagation life prediction method is suitable for metal material low cycle fatigue, high cycle fatigue in the crack propagation life analysis, the applicable temperature environment range is extensive.

[0034] (2) high efficiency: the crack propagation entropy calculation described in the present application can avoid redundant numerical simulation analysis and experimental data processing, improve the efficiency of metal material crack propagation life prediction analysis.

[0035] (3) economy: using the crack propagation life prediction method proposed in the present application, the demand for computer computing power of numerical simulation can be reduced, and the demand for continuous work of measuring equipment of crack propagation experiment can be reduced. BRIEF DESCRIPTION OF DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present application, the drawings needed in the embodiments will be briefly introduced below, and the features and advantages of the present application will be more clearly understood by referring to the drawings. The drawings are schematic and should not be understood as any limitation on the present application. For those skilled in the art, other drawings can be obtained without creative labor on the basis of these drawings. Among them:

[0037] Figure 1 The flow chart of the present application.

[0038] Figure 2 The three-dimensional crack propagation process of metal material is shown in the figure, and the label explanation is as follows: 1-three-dimensional crack propagation sample model; 2-thermodynamic system; 3-fatigue crack; 4-plastic zone at crack tip; 5-cyclic load; 6-stress state of microelement in plastic zone at crack tip.

[0039] Figure 3This is a schematic diagram of the two-dimensional crack propagation process in metallic materials. The labels in the diagram are as follows: 1-Two-dimensional crack propagation specimen model; 2-Thermodynamic system; 3-Fatigue crack; 4-Plastic zone at crack tip; 5-Cyclic load; 6-Stress state of micro-elements in the plastic zone at crack tip.

[0040] Figure 4 This is a schematic diagram of the cycle entropy production rate versus cycle lifetime function curve. In the figure, N0 is the initial lifetime of crack propagation, and N... f The failure life is the time required for crack propagation.

[0041] Figure 5 This is a schematic diagram illustrating the linear evolution relationship between lifetime consumption and entropy production-damage parameters.

[0042] Figure 6 This is a schematic diagram illustrating the exponential evolution of lifetime consumption and entropy production-damage parameters. Detailed Implementation

[0043] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0044] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0045] like Figure 1 As shown, a method for predicting fatigue crack propagation life of metallic materials based on crack propagation entropy includes the following steps:

[0046] Step 1: Define the local region containing the crack itself and the possible path of the plastic zone at the crack tip as a thermodynamic system;

[0047] The crack propagation process in metallic materials is essentially an irreversible thermodynamic process. Therefore, when studying crack propagation in metallic materials within the framework of thermodynamic theory, the object of study, namely the thermodynamic system, should be clearly defined first.

[0048] Crack is a macroscopic representation of material fatigue damage, so the defined thermodynamic system needs to include the crack itself. During the crack propagation of metal materials, the fatigue damage of the material mainly occurs in the local plastic zone near the crack tip, and the thermodynamic entropy production related to the damage is also concentrated in this area. Therefore, when defining the thermodynamic system, the plastic zone at the crack tip should always be included in the thermodynamic system, and attention should be paid to the characteristics of the plastic zone moving with the crack propagation. Therefore, in order to facilitate the thermodynamic research on the crack propagation problem of metal materials and reduce unnecessary analysis, the local area containing the crack itself and the possible position of the plastic zone at the crack tip should be defined as the thermodynamic system, and during the crack propagation process, the crack itself and the plastic zone at the crack tip should always be in the defined thermodynamic system, as shown in Figure 2 、 Figure 3 In addition, in order to facilitate analysis, the local area should not be too large.

[0049] Step 2: Obtain the stress tensor, strain tensor and temperature evolution data in the plastic zone at the crack tip of the metal material under cyclic loading through theoretical analysis, simulation or experiment, and calculate the time entropy production rate, cyclic entropy production rate in the plastic zone at the crack tip based on the stress tensor, strain tensor and temperature evolution data;

[0050] Any method or combination of several methods can be used to obtain the stress tensor, strain tensor and temperature evolution data in the plastic zone at the crack tip of the metal material under cyclic loading.

[0051] Based on the obtained stress tensor, strain tensor and temperature evolution data, the following formula is used to calculate the unit volume time entropy production rate of the microelement in the plastic zone at the crack tip through thermodynamic theoretical analysis:

[0052]

[0053] where, is the time entropy production rate, σ、 T are the stress tensor, strain tensor change rate and temperature respectively.

[0054] For three-dimensional crack propagation problems, σ、 has the following mathematical form:

[0055]

[0056]

[0057] where x, y and z represent the coordinate axes of the three-dimensional rectangular coordinate system.

[0058] For two-dimensional crack propagation problems, σ、 has the following mathematical form:

[0059]

[0060]

[0061] wherein x and y represent the coordinate axis direction of a two-dimensional rectangular coordinate system.

[0062] By selecting one or more load cycles, the time entropy production rate is volume integrated or area integrated over the loading time corresponding to the selected number of load cycles, and the integral value is averaged over the selected number of load cycles to obtain the cyclic entropy production rate per unit volume:

[0063]

[0064] wherein dω represents the time entropy production rate corresponding to the microelement volume or microelement area, Ω represents the volume or area of the plastic zone at the crack tip, is the cyclic entropy production rate, represents the specific volume entropy production within a single load cycle, and n and t(n) represent the selected number of load cycles and the corresponding loading time, respectively, wherein n is a positive integer.

[0065] Step 3: Through theoretical analysis, simulation or experiment, the crack length increment Δa or the cycle life increment ΔN is obtained, and the corresponding ΔN cycle life increment or Δa crack length increment of the crack propagation is determined;

[0066] Any method or combination of several methods is used to calculate the crack length increment Δa or the cycle life increment ΔN, and the corresponding crack length increment Δa or cycle life increment ΔN of the crack propagation is determined by the method used, and the Δa-ΔN data corresponding to the crack propagation are obtained.

[0067] Step 4: After the crack length increment Δa or the cycle life increment ΔN, the stress tensor, strain tensor and temperature evolution data in the plastic zone at the crack tip of the metal material subjected to cyclic loading are obtained, and the time entropy production rate and the cyclic entropy production rate in the plastic zone at the crack tip corresponding to the crack length are calculated;

[0068] The stress tensor, strain tensor and temperature evolution data in the plastic zone at the crack tip after the crack length increment Δa or the cycle life increment ΔN are obtained by the method described in step 2, and the time entropy production rate and the cyclic entropy production rate in the plastic zone at the crack tip are calculated by the formula described in step 2.

[0069] Step 5: Repeat steps 3-4 until the metal material fails or the crack propagates to a given length;

[0070] Any one method or combination of several methods of theoretical formula calculation, numerical simulation or fatigue experiment is adopted to repeatedly implement the crack propagation in step 3, the calculation of time entropy production rate and cycle entropy production rate in step 4 until the metal material is broken or the crack length reaches a given length. When step 3 is repeatedly implemented, the size of crack length increment Δa or cycle life increment ΔN is allowed to change during the repeated implementation and does not require to be a constant value all the time. The size of Δa or ΔN can be changed according to the implementation requirements.

[0071] Step 6: Based on the cycle life increment data of the crack propagation to each crack length, the function relationship between cycle entropy production rate and cycle life is established as a whole or in segments, and the cycle entropy production rate is summed or integrated to calculate the crack propagation entropy at different times of crack propagation;

[0072] Based on the cycle life increment data of the crack propagation to each crack length, the function relationship between cycle entropy production rate and cycle life is established as a whole or in segments, that is, The function relationship is shown in the following formula (1): Figure 4 Based on the function relationship, the crack propagation entropy s at different times of crack propagation can be obtained by summing or integrating the cycle entropy production rate g (N):

[0073] or wherein s g (N i ) is the crack propagation entropy at the time when the crack propagation reaches the cycle life N i , which represents the cumulative thermodynamic entropy production of the crack from the initial time to the cycle life N i , N0 is the initial life of crack propagation, and represent the cycle entropy production rates at the cycle lives of N, N k and N k+1 , respectively, ΔN k+1 represents the cycle life increment corresponding to the crack propagation from the cycle life N k to the cycle life N k+1 , and k is a natural number less than i.

[0074] Step 7: Based on the crack propagation entropy, the entropy production-damage parameter of the crack propagation process of the metal material is constructed, the evolution law of the entropy production-damage parameter and life consumption is established, and the crack propagation life prediction of the metal material is carried out based on the evolution law of the entropy production-damage parameter and life consumption.

[0075] Based on the crack propagation entropy s g (N) at different times of crack propagation and the critical crack propagation entropy s cEstablishment of entropy production-damage parameter Wherein the critical crack propagation entropy s c is the crack propagation entropy corresponding to the crack propagation failure time, which can be obtained by experimental critical crack propagation entropy data.

[0076] Based on the evolution data of entropy production-damage parameter D s and life consumption , the evolution law of life consumption and entropy production-damage parameter is established, that is Wherein N is the corresponding cycle life when the entropy production-damage parameter is D s , N f is the crack propagation failure life, it needs to be clear that the specific form of the evolution law exists linear, exponential and other forms due to the difference of material properties. For example, for steel or aluminum alloy materials, there is an approximate linear relationship between life consumption and entropy production-damage parameter D s , that is Wherein k is a constant related to material properties, load, etc., as shown in Figure 5 . And for nickel-based superalloy materials, there is an approximate exponential relationship between life consumption and entropy production-damage parameter D s , that is Wherein a, b and c are constants related to material properties, load, etc., as shown in Figure 6 .

[0077] Thus, the evolution law of entropy production-damage parameter D s and life consumption and entropy production-damage parameter is established , and then the crack propagation life can be predicted by the following formula:

[0078]

[0079] Through the above description, the metal material fatigue crack propagation life prediction method based on crack propagation entropy can predict the low cycle fatigue and high cycle fatigue crack propagation life of metal materials, improve the crack propagation life prediction and analysis efficiency, reduce the demand for computer computing power of numerical simulation, and reduce the demand for continuous work of loading equipment and measuring equipment of crack propagation experiment.

[0080] The above only describes the preferred embodiments of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for predicting fatigue crack propagation life of metallic materials based on crack propagation entropy, characterized in that, Includes the following steps: Step 1: Define the local region containing the crack itself and the possible path of the plastic zone at the crack tip as a thermodynamic system; Step 2: Obtain stress tensor, strain tensor and temperature evolution data in the plastic zone at the crack tip when subjected to cyclic loading at the initial crack length of the metallic material through theoretical analysis, simulation or experiment, and calculate the time entropy production rate and cyclic entropy production rate in the plastic zone at the crack tip based on the stress tensor, strain tensor and temperature evolution data. Step 3: Through theoretical analysis, simulation, or experimentation, determine the crack propagation Δ a Crack length increment or Δ N Cycle life increment, and determine the Δ corresponding to the crack propagation in this segment. N Cycle life increment or Δ a Crack length increment; Step 4: Crack propagation Δ a Crack length increment or Δ N After the cycle life increment, the stress tensor, strain tensor and temperature evolution data in the plastic zone at the crack tip are obtained when the metal material is subjected to cyclic loading. The time entropy production rate and cyclic entropy production rate of the plastic zone at the crack tip corresponding to the crack length are calculated. Step 5: Repeat steps 3-4 until the metal material fractures or the crack extends to a given length; Step 6: Combining the incremental data of cycle life when the crack extends to each crack length, establish the relationship between the cycle entropy yield and the cycle life function as a whole or in segments, and sum or integrate the cycle entropy yield to calculate the crack propagation entropy at different times of crack propagation. Step 7: Construct entropy production-damage parameters for the crack propagation process of metallic materials based on crack propagation entropy, establish the evolution law of entropy production-damage parameters and lifetime consumption, and predict the crack propagation lifetime of metallic materials based on the evolution law of entropy production-damage parameters and lifetime consumption. The time entropy yield in steps 2 and 4 is calculated using the following formula based on the obtained stress tensor, strain tensor, and temperature evolution data, derived through thermodynamic theory analysis: in, For time entropy productivity, , , T These are the stress tensor, the rate of change of the strain tensor, and temperature, respectively, and the mathematical forms of the stress tensor and the rate of change of the strain tensor are different in the three-dimensional crack propagation problem and the two-dimensional crack propagation problem. In steps 2 and 4, the cyclic entropy yield is obtained by selecting one or more load cycles, integrating the time entropy yield over the loading time corresponding to the selected load cycle number using either volume or area integration, and then averaging this integral value over the selected load cycle number to obtain the cyclic entropy yield per unit volume. in, Represents time entropy productivity The corresponding infinitesimal volume or infinitesimal area, This indicates the volume or area of ​​the plastic zone at the crack tip. Cyclic entropy production rate, representing the specific volumetric entropy production within a single load cycle. n and t ( n The numbers ) represent the selected load cycle number and the corresponding loading time, respectively. n Take a positive integer; Step 6 involves summing or integrating the cyclic entropy yield to calculate the crack propagation entropy at different times of crack propagation: or in, For crack propagation to cycle life of The crack propagation entropy at time t represents the crack propagation from the initial time to the cycle life of t. The cumulative thermodynamic entropy production over time, For crack propagation initial life, , and These represent cycle lifespans of 1000 and 1000, respectively. N , and, Cyclic entropy production rate at time Indicates the crack's lifespan from cycle life Extended to a cycle life of The corresponding cycle lifetime increment, where k is a natural number less than i; Step 7 is based on the crack propagation entropy at different times of crack propagation. Critical crack propagation entropy of metallic materials s c Constructing Entropy Production-Damage Parameters Among them, the critical crack propagation entropy It is the crack propagation entropy at the moment of crack propagation failure; based on entropy production-damage parameters. With lifespan consumption Based on the evolutionary data, the evolutionary laws governing lifetime consumption and entropy production-damage parameters are established, i.e. The crack propagation life can then be predicted using the following formula: in, N The entropy production-damage parameter is The corresponding cycle life, The failure life is the time required for crack propagation.

2. The method according to claim 1, characterized in that, In step 1, the crack itself and the plastic zone at the crack tip remain within the selected thermodynamic system throughout the entire crack propagation process.

3. The method according to claim 1, characterized in that, The stress tensor, strain tensor, and temperature evolution data in steps 2 and 4 can be obtained by any method or a combination of several methods, including theoretical formula calculation, numerical simulation, or fatigue experiment, to obtain the stress tensor, strain tensor, and temperature evolution data in the plastic zone at the crack tip of the metallic material under cyclic loading conditions.

4. The method according to claim 1, characterized in that, Step 3 involves using any one or a combination of methods from theoretical formula calculations, numerical simulations, or fatigue experiments to achieve crack propagation Δ. a Crack length increment or Δ N Cycle life increment, and the corresponding crack propagation Δ determined by the method employed. N Cycle life increment or Δ a The crack length increment is used to obtain the Δ corresponding to the crack propagation of that segment. a -Δ N data.

5. The method according to claim 1, characterized in that, Step 5 involves repeating the crack propagation calculations in Step 3 and the time entropy yield and cyclic entropy yield calculations in Step 4 using any one or a combination of theoretical formula calculations, numerical simulations, or fatigue experiments, until the metallic material fractures or the crack length reaches a given length. When repeating Step 3, the crack length increment Δ... a Or cycle life increment Δ N The size of Δ is allowed to vary during repeated implementations and is not required to remain constant. It can be changed according to implementation needs. a or Δ N Size.

6. The method according to claim 1, characterized in that, Step 7, for steel or aluminum alloy, lifespan consumption With entropy production-damage parameter There exists an approximately linear relationship between them, that is... ,in k It is a constant related to material properties and load; for nickel-based superalloys, lifespan consumption... With entropy production-damage parameter There exists an approximately exponential relationship between them, that is... ,in a , b and c It is a constant related to material properties and load.

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