Reliability evaluation method and system based on cumulative damage-damage threshold interference

Abstract

This invention discloses a reliability evaluation method and system based on cumulative damage-damage threshold interference, relating to the fields of creep-fatigue damage evaluation and reliability assessment. It establishes a creep-fatigue damage accumulation criterion for the target material considering mechanical property degradation; uses multi-source uncertainties under creep-fatigue loading as input to a finite element model, and determines the probabilistic damage distribution in weak point regions through the creep-fatigue damage model; quantifies the dispersion of mechanical property degradation and determines the probabilistic damage threshold distribution under different damage levels; calculates reliability using cumulative damage-damage threshold interference theory, and plots a three-dimensional creep-fatigue reliability grading evaluation chart with mechanical property degradation to determine the damage level and remaining safe life of the structural material. By establishing a three-dimensional creep-fatigue reliability grading evaluation chart, the creep-fatigue reliability and remaining safe life of in-service components can be assessed more accurately.

Description

Technical Field

[0001] This invention relates to the field of low-cycle fatigue and creep-fatigue reliability assessment, and more specifically to a damage classification and reliability evaluation method and system based on cumulative damage-damage threshold interference theory, especially for identifying the damage level of component materials used in high-temperature environments and the remaining safe life of high-reliability components, applicable to the evaluation and maintenance of high-temperature structural integrity. Background Technology

[0002] With the implementation of dual-carbon goals, critical components such as gas turbines, aero engines, and nuclear reactor vessels are exposed to extremely harsh service environments. The long-term reliable operation and maintenance of component materials has become one of the main bottlenecks restricting the development of these critical components. Low-cycle fatigue during start-up and shutdown and creep-fatigue interaction during stable operation are key factors limiting component lifespan and reliability. Furthermore, the mechanical properties of component materials gradually degrade with prolonged service life. However, probabilistic fatigue and creep-fatigue analyses do not consider the impact and uncertainties of mechanical property degradation. Therefore, current design criteria based on initial mechanical properties may introduce non-conservative risks into component damage assessment and reliability evaluation.

[0003] In reliability analysis, commonly used interference theories are generally classified into three categories: stress-strength interference (SSI), load-life interference (LLI), and cumulative damage-damage threshold interference (CDDTI). Some studies have incorporated strength degradation models during cyclic processing into SSI theory for reliability evaluation, but this is not applicable to cyclically hardened materials with increasing strength. Fatigue life is a fundamental variable in LLI, typically obtained through PSN curves or fatigue life prediction models. Fatigue life models are faster than PSN curves, but their accuracy depends on the model selection. Mainstream life prediction models predict life using fatigue and creep damage parameters, which is fundamentally equivalent to CDDTI theory. CDDTI theory can effectively address issues such as multi-level loads, multi-damage interactions, and mechanical property degradation in damage evaluation and reliability assessment, enriching the connotation of engineering damage mechanics. Therefore, based on CDDTI interference theory, this invention proposes a damage grading and reliability evaluation method and system that considers the degradation of material mechanical properties, establishing a three-dimensional creep-fatigue reliability grading evaluation chart, which has significant value for engineering applications. Summary of the Invention

[0004] The purpose of this invention is to provide a reliability evaluation method and system based on cumulative damage-damage threshold interference. This method quantifies and correlates the degree of degradation of material mechanical properties with the reliability grading assessment, and establishes a three-dimensional creep-fatigue reliability grading assessment chart. This method can more accurately assess the creep-fatigue reliability and remaining safe life of in-service components, improve the existing high-temperature structural integrity evaluation system, and has important engineering application value.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] This invention provides a reliability evaluation method based on cumulative damage-damage threshold interferometry, the method comprising:

[0007] Multiple sets of tests are conducted on the target material. Creep damage and fatigue damage are calculated based on the creep-fatigue damage model corresponding to the target material. Mechanical property degradation parameters are calculated based on tensile plastic strain energy density. A creep-fatigue damage accumulation criterion considering mechanical property degradation is established based on the creep damage, the fatigue damage, and the mechanical property degradation parameters. The tests include interrupted creep-fatigue tests and interrupted tensile tests.

[0008] A finite element model of the target material is constructed, and the probabilistic damage distribution of the weak region of the target material is determined by combining the multi-source uncertainty factors under creep-fatigue loading.

[0009] The dispersion of the mechanical performance degradation exponent is quantified based on the test dataset composed of the mechanical performance degradation parameter and the interruption life fraction, and the probability damage threshold distribution under different damage levels is obtained based on the dispersion; the expression of the creep-fatigue damage accumulation criterion considering mechanical performance degradation includes a probability damage distribution part and a probability damage threshold distribution part.

[0010] Based on the probability damage distribution and the probability damage threshold distribution, probabilistic damage and probability damage threshold are randomly sampled, and the failure probability of the target material is calculated by applying the cumulative damage-damage threshold interference theory based on the sampled probabilistic damage and sampled probability loss threshold; the reliability of the target material is represented by the failure probability.

[0011] Based on the failure probability, the mechanical property degradation parameter, and the remaining safe life of the target material, a three-dimensional creep-fatigue reliability classification evaluation chart is drawn to reflect the mechanical property degradation.

[0012] The remaining safe life of the material to be evaluated is determined based on the three-dimensional creep-fatigue reliability grading evaluation chart, the mechanical property degradation parameters of the material to be evaluated, and the preset failure probability of the material to be evaluated; and the damage level of the material to be evaluated is determined based on the mechanical property degradation parameters and the predefined relationship between the mechanical property degradation parameters and the damage level.

[0013] Optionally, the expression for the creep-fatigue damage accumulation criterion considering mechanical property degradation is:

[0014]

[0015] in,

[0016] In the formula, D c For creep damage; D f For fatigue damage; D m U is a parameter for mechanical property degradation. T(0) U represents the tensile plastic strain energy of the undamaged material. T(N) Let n be the tensile plastic strain energy of the material in the Nth cycle; n is the damage exponent, derived from the creep damage D. c and fatigue damage D f The damage envelope is obtained from the constructed test dataset; m is the power exponent of mechanical property degradation, derived from the mechanical property degradation parameter D. m The degradation envelope is obtained by determining the evolution law of the interrupted lifetime fraction; Corresponding probability damage distribution part; 1-(D m ) m The corresponding probability damage threshold distribution part.

[0017] Optionally, a finite element model of the target material is constructed, and the probabilistic damage distribution of the weak region of the target material is determined by combining multi-source uncertainties under creep-fatigue loading, specifically including:

[0018] A finite element model of the target material is established, and a creep-fatigue constitutive model of the target material is embedded in the finite element model to obtain a first embedded finite element model;

[0019] The weak region is determined based on the first embedded finite element model combined with the stress-strain field of the target material;

[0020] The creep-fatigue damage model is embedded in the first embedded finite element model to obtain the second embedded finite element model;

[0021] The multi-source uncertainty factors are input into the second embedded finite element model to obtain the creep damage and fatigue damage of the steady-state cycle of the finite element response output;

[0022] Based on the steady-state cycle creep damage and fatigue damage from the finite element response output, the probability damage distribution of the weak point region is statistically analyzed using probabilistic methods.

[0023] Optionally, the dispersion of the mechanical performance degradation exponent is quantified based on the test dataset composed of the mechanical performance degradation parameter and the interrupted life fraction, and the probability damage threshold distribution under different damage levels is obtained based on the dispersion, specifically including:

[0024] The dispersion of the mechanical performance degradation exponent is quantified based on the experimental dataset composed of the mechanical performance degradation parameter and the interruption life fraction.

[0025] Based on the aforementioned dispersion, determine the first mean and first standard deviation of the standard normal distribution of the probabilistic damage threshold under different damage levels;

[0026] Based on the characteristic that the damage threshold is greater than 0, the standard normal distribution of the probability damage threshold is converted into a truncated normal distribution, and the second mean and the second standard deviation of the truncated normal distribution are determined based on the first mean and the first standard deviation.

[0027] The probability density function of the truncated normal distribution is determined based on the first mean and the first standard deviation; the probability damage threshold distribution is determined by the second mean, the second standard deviation, and the probability density function.

[0028] Optionally, the expression for the second mean is:

[0029]

[0030] The expression for the second standard deviation is:

[0031]

[0032] The expression for the probability density function is:

[0033]

[0034] In the formula, D crit D is the damage threshold. crit =1-(D m ) m ; φ(·) and Φ(·) are the probability density function and cumulative distribution function of the standard normal distribution; μ(D m ) is the first mean; σ(D) m () represents the first standard deviation.

[0035] Optionally, the formula for calculating the failure probability is:

[0036] P f =P(G(N)d )<0)

[0037] Among them, G(N) d ) = D crit -D(N d )

[0038] In the formula, P() represents the probability calculation method; G(N) d () represents the creep-fatigue damage accumulation criterion that considers mechanical property degradation; D crit The corresponding creep-fatigue damage accumulation criterion expression 1-(D m ) m ;D(N d The corresponding expression for the creep-fatigue damage accumulation criterion is D. c n +D f n .

[0039] Optionally, the multi-source uncertainty factors include the uncertainty of external input load, the uncertainty of basic material performance parameters, and the uncertainty of creep-fatigue damage model parameters.

[0040] The present invention also provides a reliability evaluation system based on cumulative damage-damage threshold interference, the system comprising:

[0041] The criterion construction module is used to conduct multiple sets of tests on the target material, calculate creep damage and fatigue damage based on the creep-fatigue damage model corresponding to the target material, and calculate mechanical property degradation parameters based on tensile plastic strain energy density; establish a creep-fatigue damage accumulation criterion considering mechanical property degradation based on the creep damage, the fatigue damage, and the mechanical property degradation parameters; the tests include interrupted creep-fatigue tests and interrupted tensile tests;

[0042] The probability damage distribution determination module is used to construct a finite element model of the target material and determine the probability damage distribution of the weak area of ​​the target material in combination with multi-source uncertainty factors under creep-fatigue loading.

[0043] The probability damage threshold distribution determination module is used to quantify the dispersion of the mechanical performance degradation exponent based on the test dataset composed of the mechanical performance degradation parameter and the interruption life fraction, and to obtain the probability damage threshold distribution under different damage levels based on the dispersion; the expression of the creep-fatigue damage accumulation criterion considering mechanical performance degradation includes a probability damage distribution part and a probability damage threshold distribution part.

[0044] The failure calculation module is used to randomly sample probabilistic damage and probabilistic damage threshold based on the probabilistic damage distribution and the probabilistic damage threshold distribution, and to calculate the failure probability of the target material based on the sampled probabilistic damage and sampled probabilistic loss threshold using the cumulative damage-damage threshold interference theory; the reliability of the target material is represented by the failure probability.

[0045] The reliability grading evaluation chart drawing module is used to draw a three-dimensional creep-fatigue reliability grading evaluation chart that varies with mechanical property degradation based on the failure probability, the mechanical property degradation parameter and the remaining safe life of the target material.

[0046] The reliability evaluation module is used to determine the remaining safe life of the material to be evaluated based on the three-dimensional creep-fatigue reliability grading evaluation chart, the mechanical property degradation parameters of the material to be evaluated, and the preset failure probability of the material to be evaluated; and to determine the damage level of the material to be evaluated based on the mechanical property degradation parameters and the predefined relationship between the mechanical property degradation parameters and the damage level.

[0047] Optionally, the expression for the creep-fatigue damage accumulation criterion considering mechanical property degradation is:

[0048]

[0049] in,

[0050] In the formula, D c For creep damage; D f For fatigue damage; D m U is a parameter for mechanical property degradation. T(0) U represents the tensile plastic strain energy of the undamaged material. T(N) Let n be the tensile plastic strain energy of the material in the Nth cycle; n is the damage exponent, derived from the creep damage D. c and fatigue damage D f The damage envelope is obtained from the constructed test dataset; m is the power exponent of mechanical property degradation, derived from the mechanical property degradation parameter D. m The degradation envelope is obtained by determining the evolution law of the interrupted lifetime fraction; Corresponding probability damage distribution part; 1-(D m ) m The corresponding probability damage threshold distribution part.

[0051] Optionally, the probability damage distribution determination module specifically includes:

[0052] The first embedded finite element model construction unit is used to establish the finite element model of the target material and embed the creep-fatigue constitutive model of the target material into the finite element model to obtain the first embedded finite element model;

[0053] The weak region determination unit is used to determine the weak region based on the first embedded finite element model combined with the stress-strain field of the target material;

[0054] The second embedded finite element model construction unit is used to embed the creep-fatigue damage model into the first embedded finite element model to obtain the second embedded finite element model.

[0055] The finite element response unit is used to input the multi-source uncertainty factors into the second embedded finite element model to obtain the creep damage and fatigue damage of the steady-state cycle of the finite element response output.

[0056] The probability damage distribution determination unit is used to statistically analyze the probability damage distribution of the weak point region based on the creep damage and fatigue damage of the steady-state cycles of the finite element response output using probabilistic methods.

[0057] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0058] This invention provides a reliability evaluation method and system based on cumulative damage-damage threshold interference. Based on the cumulative damage-damage threshold interference theory, it quantifies the degree of degradation of material mechanical properties and correlates it with reliability grading assessment, establishing a three-dimensional creep-fatigue reliability grading assessment map. This enables a more accurate assessment of the creep-fatigue reliability and remaining safe life of the component under test, improving the existing high-temperature structural integrity evaluation system and having significant engineering application value. Attached Figure Description

[0059] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0060] Figure 1 A flowchart of the reliability evaluation method based on cumulative damage-damage threshold interference provided in Embodiment 1 of the present invention;

[0061] Figure 2 This is a damage accumulation criterion diagram considering the degradation of material mechanical properties provided in Embodiment 1 of the present invention;

[0062] Figure 3This is a diagram of the weak point region of an aircraft turbine disk provided in Embodiment 1 of the present invention;

[0063] Figure 4 This is a probability distribution diagram of creep damage and fatigue damage in the weak area provided in Embodiment 1 of the present invention;

[0064] Figure 5 This is a probability distribution diagram of the power exponent m of mechanical property degradation provided in Embodiment 1 of the present invention;

[0065] Figure 6 This is the distribution of probabilistic damage thresholds under different degrees of mechanical property degradation provided in Embodiment 1 of the present invention;

[0066] Figure 7 This is a three-dimensional reliability grading evaluation diagram and condition assessment points for GH4169 alloy provided in Embodiment 1 of the present invention. Detailed Implementation

[0067] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0068] The purpose of this invention is to provide a reliability evaluation method and system based on cumulative damage-damage threshold interference. It constructs a creep-fatigue damage accumulation criterion that considers mechanical property degradation. When applying the cumulative damage-damage threshold interference theory, it considers the mechanical property degradation parameter. As the service time increases, the safe life defined by the reliability design curve decreases. It can accurately evaluate the reliability of materials and reasonably reflect the impact of material mechanical property degradation on component reliability evaluation.

[0069] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0070] Example 1

[0071] like Figure 1 As shown, this embodiment provides a reliable evaluation method based on the cumulative damage-damage threshold interference theory, the method comprising:

[0072] S1: Conduct multiple sets of tests on the target material, calculate creep damage and fatigue damage based on the creep-fatigue damage model corresponding to the target material, and calculate mechanical property degradation parameters based on tensile plastic strain energy density; establish a creep-fatigue damage accumulation criterion considering mechanical property degradation based on the creep damage, the fatigue damage and the mechanical property degradation parameters; the tests include interrupted creep-fatigue tests and interrupted tensile tests.

[0073] In this embodiment, the evaluation method is illustrated using an aerospace low-pressure turbine disk as an example. GH4169 alloy is used as the material of the turbine disk, and its operating temperature is 650℃. The damage model adopts the multiaxial creep fatigue damage model provided in the literature [Wang RZ, et al. Multi-axial creep-fatigue life prediction considering history-dependent damage evolution: A new numerical procedure and experimental validation[J]. Journal of the Mechanics and Physics of Solids, 2019, 131: 313-316].

[0074] Step S1 further includes:

[0075] S11: Based on the actual stress-strain curves of the tensile test after interruption, establish the material mechanical property degradation parameter D. m The equation is as follows:

[0076]

[0077] In the formula, U T(0) U represents the tensile plastic strain energy of the undamaged material. T(N) Let N be the tensile plastic strain energy of the material in the Nth cycle.

[0078] S12: Establish a creep-fatigue damage accumulation criterion that considers mechanical property degradation, as shown in the following equation:

[0079]

[0080] In the formula, D c For creep damage; D f For fatigue damage; D m The mechanical property degradation parameter is n; the damage exponent is D, which is derived from creep damage. c and fatigue damage D f The damage envelope is obtained from the constructed test dataset; m is the power exponent of mechanical property degradation, derived from the mechanical property degradation parameter D. mThe degradation envelope is obtained by determining the evolution law of the interrupted lifetime fraction; Corresponding probability damage distribution part; 1-(D m ) m The corresponding probability damage threshold distribution part.

[0081] S13: Based on the experimental dataset (D) c D f The power exponent n is obtained by determining the damage envelope, based on D. m The evolution law of interrupted lifetime fraction is used to determine the degradation envelope and obtain the power exponent m.

[0082] Experimental dataset based on GH4169 alloy (D c D f The literature [Wang RZ, et al. A modified strain energy density exhaustion model for creep-fatigue life prediction[J]. International Journal of Fatigue, 2016, 90: 12-22] indicates that when the value of n is 0.576, it provides an accurate failure estimation result with a confidence level of 89.1%. Based on the evolution law of Dm and interrupted life fraction, the degradation envelope is determined. The literature [Sun L, et al. Evaluation of fatigue and creep-fatigue damage levels on the basic baso-fenging damage mechanics approach[J]. International Journal of Fatigue, 2022, 166: 107-277] indicates that when the value of m is 0.122, the creep-fatigue damage accumulation criterion considering the degradation of the mechanical properties of GH4169 alloy is as follows: Figure 2 As shown, the safe zone defined by the damage accumulation criterion gradually decreases as the degree of material damage increases. Figure 2 D in crit It refers to 1-(D) m ) m .

[0083] S2: Construct a finite element model of the target material and determine the probabilistic damage distribution of the weak region of the target material by combining multi-source uncertainty factors under creep-fatigue loading.

[0084] Specifically, step S2 includes:

[0085] S21: Establish a finite element model of the target material, and embed the creep-fatigue constitutive model of the target material into the finite element model to obtain a first embedded finite element model. Based on the first embedded finite element model and the stress-strain field of the target material, determine the weak region.

[0086] Considering the symmetrical structure of the turbine disk, a finite element model of a 1 / 72 scale structure of the turbine disk is constructed. The embedded constitutive model includes a cyclic elastoplastic constitutive model describing fatigue behavior and a strain-strengthening constitutive model describing creep behavior. The constitutive equations disclosed in patent application CN202010289799.6 are used. The stress-strain field is used to determine the location of maximum stress in the weakest region of the component. Figure 3 As shown.

[0087] In this embodiment, a three-dimensional finite element model of the turbine disk can be established using ABAQUS software, and the creep fatigue constitutive and damage models can be embedded by writing code in Fortran language through the User Subroutine Interface (UMAT).

[0088] S22: Embed the creep-fatigue damage model into the first embedded finite element model to obtain a second embedded finite element model. Input the multi-source uncertainty factors into the second embedded finite element model to obtain the creep damage and fatigue damage in the steady-state cycles of the finite element response output. Based on the creep damage and fatigue damage in the steady-state cycles of the finite element response output, apply probabilistic methods to statistically analyze the probabilistic damage distribution of the weak point region.

[0089] After embedding the creep-fatigue damage model, 100 Latin hypercube samplings were performed on the random variables (multi-source uncertainties) to obtain 100 sets of data as input to the finite element method. The finite element response output, i.e., the creep damage and fatigue damage at steady-state cycles, was obtained. Probabilistic methods were used to statistically analyze the probabilistic damage distribution in the weak point region, such as... Figure 4 As shown. It should be noted that the number of sampling groups can be selected according to actual needs.

[0090] The multi-source uncertainties include the uncertainty of external input load, the uncertainty of basic material performance parameters, and the uncertainty of creep-fatigue damage model parameters. Based on multi-source correlation analysis, the external input load is represented as ω; the basic material performance parameters are represented as ρ, E; and the creep-fatigue damage model parameters are represented as n1, w. f,crit ,τ' f , γ' f Among them, n1 and w f,crit τ' represents the parameters of the creep damage model. f and γ' fHere are the parameters for the fatigue damage model. n1 is a model constant that fits the relationship between the failure strain energy density and the inelastic strain energy density dissipation rate function, and w... f,crit Let τ' be the critical failure strain energy density. f γ' is the shear fatigue strength coefficient. f This represents the shear fatigue toughness coefficient. The specific distribution of the random variable is shown in Table 1 below.

[0091] Table 1: Probability distribution characteristics of multi-source uncertainty

[0092]

[0093]

[0094] It should be noted that Table 1 only lists the more important representative variables, not all random variables. Other random variables can be selected according to the uncertainty factors considered in practice. This invention does not limit this.

[0095] S3: Based on the test dataset composed of the mechanical property degradation parameters and the interrupted life fraction, the dispersion of the mechanical property degradation power exponent is quantified, and the probability damage threshold distribution under different damage levels is obtained based on the dispersion; the expression of the creep-fatigue damage accumulation criterion considering mechanical property degradation includes a probability damage distribution part and a probability damage threshold distribution part.

[0096] Specifically, step S3 includes:

[0097] S31: Quantify the dispersion of the mechanical performance degradation exponent based on the experimental dataset composed of the mechanical performance degradation parameter and the interrupted life fraction. Determine the first mean μ(D) of the standard normal distribution of the probabilistic damage threshold under different damage levels based on the dispersion. m ) and the first standard deviation σ(D) m ).

[0098] The reference [Sun L, et al. Evaluation of fatigue and creep-fatigue damage levels on the basic engineering damage mechanics approach [J]. International Journal of Fatigue, 2022, 166: 107-277] indicates that under fatigue and creep-fatigue loading, D m Interruption lifetime fraction N / N f The relationship exhibits a power function, and the lower critical curve is defined as the degenerate envelope, with a corresponding power exponent of m. Based on (D m N / N fThe experimental dataset quantifies the dispersion of the power exponent m of mechanical property degradation, such as... Figure 5 As shown, 100 Latin hypercube samplings were performed on the random variable m to obtain the first mean μ(D) of the standard normal distribution of the probability damage threshold under different damage levels. m ) and the first standard deviation σ(D) m ).

[0099] S33: Based on the characteristic that the damage threshold is greater than 0, the standard normal distribution of the probability damage threshold is converted into a truncated normal distribution, and the second mean and the second standard deviation of the truncated normal distribution are determined based on the first mean and the first standard deviation.

[0100] S34: Determine the probability density function of the truncated normal distribution based on the first mean and the first standard deviation; the probability damage threshold distribution is determined by the second mean, the second standard deviation, and the probability density function. Damage threshold distributions at different damage levels are as follows: Figure 6 As shown.

[0101] The expression for the second mean is:

[0102]

[0103] The expression for the second standard deviation is:

[0104]

[0105] The expression for the probability density function is:

[0106]

[0107] In the formula, D crit D is the damage threshold. crit =1-(D m ) m ; φ(·) and Φ(·) are the probability density function and cumulative distribution function of the standard normal distribution; μ(D m ) is the first mean; σ(D) m () represents the first standard deviation.

[0108] S4: Based on the probabilistic damage distribution and the probabilistic damage threshold distribution, random sampling is performed on the probabilistic damage and probabilistic damage threshold. The cumulative damage-damage threshold interference theory is applied to calculate the failure probability of the target material based on the sampled probabilistic damage and sampled probabilistic loss threshold. A three-dimensional creep-fatigue reliability grading evaluation chart is plotted based on the failure probability, the mechanical property degradation parameter, and the remaining safe life corresponding to the target material, showing the degradation of mechanical properties. The reliability of the target material is represented by the failure probability.

[0109] Random sampling is performed on probabilistic damage and damage threshold, and the reliability P is calculated using the cumulative damage-damage threshold interference theory. f With reliability P f and remaining safe life N d Using the basic coordinate axes, and with the degradation parameter D of the material's mechanical properties as the reference, m Plot a three-dimensional creep-fatigue reliability grading evaluation diagram for the third axis as mechanical properties degrade. For example... Figure 7 As shown, reliability P f and remaining safe life N d Using the basic coordinate axes, and the material mechanical property degradation parameter D... m Draw a three-dimensional creep-fatigue reliability grading evaluation diagram for the third axis as mechanical properties degrade.

[0110] Based on the cumulative damage-damage threshold interference theory, the failure probability of the turbine disk at a given design life satisfies the following relationship:

[0111] P f =P(G(N) d )<0)

[0112] Among them, G(N) d ) = D crit -D(N d )

[0113] In the formula, P f G(N) represents the failure probability; P() represents the probability calculation method; G(N) represents the failure probability. d () represents the creep-fatigue damage accumulation criterion that considers mechanical property degradation; D crit The corresponding creep-fatigue damage accumulation criterion expression 1-(D m ) m ;D(N d The corresponding creep-fatigue damage accumulation criterion expression is in Remaining safe life N d It can also be called the design life.

[0114] S5: Determine the remaining safe life of the material to be evaluated based on the three-dimensional creep-fatigue reliability grading evaluation chart, the mechanical property degradation parameters of the material to be evaluated, and the preset failure probability of the material to be evaluated; and determine the damage level of the material to be evaluated based on the mechanical property degradation parameters and the predefined relationship between the mechanical property degradation parameters and the damage level.

[0115] D is obtained by performing tensile tests at the same temperature on the in-service structural material (the material to be evaluated). m The state point (D) is determined according to the required reliability indicators. m P fPlace the material in a three-dimensional reliability grading chart to determine the damage level and remaining safe life N of the structural material. d .

[0116] Taking a certain type of aero-engine as an example, to ensure the reliability of subsequent operation and determine its remaining safe life, its service conditions were simulated on a test bench. After running for a period of time, the engine was shut down. Using finite element software, the number of creep-fatigue cycles caused by start-up / shutdown and temperature fluctuations during service was estimated to be approximately 123 cycles. Samples were taken from the weak point area in step S21 and subjected to tensile tests at 650℃. Based on step S11, D was calculated. m Considering that the turbine disk of an aircraft engine is a critical component with high reliability requirements, the reliability index can be set at 99.8%. (D) m P f Placed in a three-dimensional reliability grading diagram, such as Figure 7 As shown, the damage level of this type of turbine disk can be determined to be Level II, and the reliability of continuing to operate for 82 cycles is 99.8%.

[0117] The relationship between predefined mechanical property degradation parameters and damage levels is shown in Table 2 below:

[0118] Table 2: Damage Level Classification of GH4169 Alloy

[0119]

[0120] In this embodiment, compared with existing prediction techniques, the present invention utilizes a three-dimensional creep-fatigue reliability grading chart to assess the damage level of materials in real time. By analyzing the position of the state point on the reliability grading chart, the remaining safe life under the required reliability index can be quickly obtained. The present invention has strong applicability; different components can utilize different damage accumulation criteria and consider multi-source uncertainties under different load conditions to perform creep-fatigue reliability assessments.

[0121] The damage classification and reliability evaluation based on the cumulative damage-damage threshold interference theory proposed in this embodiment can effectively reflect the dynamic changes of the reliability design curve of the unit component during service. It can quickly determine the remaining safe life and maintenance cycle based on the damage level, simplify the damage detection and reliability assessment process, and has important engineering application value.

[0122] Example 2

[0123] This embodiment provides a reliability evaluation system based on cumulative damage-damage threshold interferometry, the system comprising:

[0124] The criterion construction module M1 is used to conduct multiple sets of tests on the target material, calculate creep damage and fatigue damage based on the creep-fatigue damage model corresponding to the target material, and calculate mechanical property degradation parameters based on tensile plastic strain energy density; establish a creep-fatigue damage accumulation criterion considering mechanical property degradation based on the creep damage, the fatigue damage and the mechanical property degradation parameters; the tests include interrupted creep-fatigue tests and interrupted tensile tests.

[0125] The expression for the creep-fatigue damage accumulation criterion that considers mechanical property degradation is:

[0126]

[0127] in,

[0128] In the formula, D c For creep damage; D f For fatigue damage; D m U is a parameter for mechanical property degradation. T(0) U represents the tensile plastic strain energy of the undamaged material. T(N) Let n be the tensile plastic strain energy of the material in the Nth cycle; n is the damage exponent, derived from the creep damage D. c and fatigue damage D f The damage envelope is obtained from the constructed test dataset; m is the power exponent of mechanical property degradation, derived from the mechanical property degradation parameter D. m The degradation envelope is obtained by determining the evolution law of the interrupted lifetime fraction; Corresponding probability damage distribution part; 1-(D m ) m The corresponding probability damage threshold distribution part.

[0129] The probability damage distribution determination module M2 is used to construct the finite element model of the target material and determine the probability damage distribution of the weak area of ​​the target material in combination with the multi-source uncertainty factors under creep-fatigue loading.

[0130] Specifically, the probability damage distribution determination module M2 includes:

[0131] The first embedded finite element model building unit M21 is used to establish the finite element model of the target material and embed the creep-fatigue constitutive model of the target material into the finite element model to obtain the first embedded finite element model.

[0132] The weak region determination unit M22 is used to determine the weak region based on the first embedded finite element model combined with the stress-strain field of the target material.

[0133] The second embedded finite element model building unit M23 is used to embed the creep-fatigue damage model into the first embedded finite element model to obtain the second embedded finite element model.

[0134] The finite element response unit M24 is used to input the multi-source uncertainty factors into the second embedded finite element model to obtain the creep damage and fatigue damage of the steady-state cycle of the finite element response output.

[0135] The probability damage distribution determination unit M25 is used to statistically analyze the probability damage distribution of the weak point region based on the creep damage and fatigue damage of the steady-state cycle of the finite element response output using probabilistic methods.

[0136] The probability damage threshold distribution determination module M3 is used to quantify the dispersion of the mechanical performance degradation exponent based on the test dataset composed of the mechanical performance degradation parameter and the interrupted life fraction, and to obtain the probability damage threshold distribution under different damage levels based on the dispersion; the expression of the creep-fatigue damage accumulation criterion considering mechanical performance degradation includes a probability damage distribution part and a probability damage threshold distribution part.

[0137] The failure calculation module M4 is used to randomly sample the probabilistic damage and probabilistic damage threshold based on the probabilistic damage distribution and the probabilistic damage threshold distribution, and to calculate the failure probability of the target material based on the sampled probabilistic damage and sampled probabilistic loss threshold using the cumulative damage-damage threshold interference theory; the reliability of the target material is represented by the failure probability.

[0138] The reliability grading evaluation chart drawing module M5 is used to draw a three-dimensional creep-fatigue reliability grading evaluation chart that varies with mechanical property degradation based on the failure probability, the mechanical property degradation parameter, and the remaining safe life corresponding to the target material.

[0139] The reliability evaluation module M6 is used to determine the remaining safe life of the material to be evaluated based on the three-dimensional creep-fatigue reliability grading evaluation chart, the mechanical property degradation parameters of the material to be evaluated, and the preset failure probability of the material to be evaluated; and to determine the damage level of the material to be evaluated based on the mechanical property degradation parameters and the predefined relationship between the mechanical property degradation parameters and the damage level.

[0140] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple; relevant parts can be referred to the method section.

[0141] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A reliability evaluation method based on cumulative damage-damage threshold interference, characterized in that, The method includes: Multiple sets of tests are conducted on the target material. Creep damage and fatigue damage are calculated based on the creep-fatigue damage model corresponding to the target material. Mechanical property degradation parameters are calculated based on tensile plastic strain energy density. A creep-fatigue damage accumulation criterion considering mechanical property degradation is established based on the creep damage, the fatigue damage, and the mechanical property degradation parameters. The tests include interrupted creep-fatigue tests and interrupted tensile tests. A finite element model of the target material is constructed, and the probabilistic damage distribution of the weak region of the target material is determined by combining the multi-source uncertainty factors under creep-fatigue loading. The dispersion of the mechanical performance degradation exponent is quantified based on the test dataset composed of the mechanical performance degradation parameter and the interruption life fraction, and the probability damage threshold distribution under different damage levels is obtained based on the dispersion; the expression of the creep-fatigue damage accumulation criterion considering mechanical performance degradation includes a probability damage distribution part and a probability damage threshold distribution part. Based on the probability damage distribution and the probability damage threshold distribution, probabilistic damage and probability damage threshold are randomly sampled, and the failure probability of the target material is calculated by applying the cumulative damage-damage threshold interference theory based on the sampled probabilistic damage and sampled probability loss threshold; the reliability of the target material is represented by the failure probability. Based on the failure probability, the mechanical property degradation parameter, and the remaining safe life of the target material, a three-dimensional creep-fatigue reliability classification evaluation chart is drawn to reflect the mechanical property degradation. The remaining safe life of the material to be evaluated is determined based on the three-dimensional creep-fatigue reliability grading evaluation chart, the mechanical property degradation parameters of the material to be evaluated, and the preset failure probability of the material to be evaluated; and the damage level of the material to be evaluated is determined based on the mechanical property degradation parameters and the predefined relationship between the mechanical property degradation parameters and the damage level.

2. The method according to claim 1, characterized in that, The expression for the creep-fatigue damage accumulation criterion that considers mechanical property degradation is: in, In the formula, D c For creep damage; D f For fatigue damage; D m U is a parameter for mechanical property degradation. T(0) U represents the tensile plastic strain energy of the undamaged material. T(N) Let n be the tensile plastic strain energy of the material in the Nth cycle; n is the damage exponent, derived from the creep damage D. c and fatigue damage D f The damage envelope is obtained from the constructed test dataset; m is the power exponent of mechanical property degradation, derived from the mechanical property degradation parameter D. m The degradation envelope is obtained by determining the evolution law of the interrupted lifetime fraction; Corresponding probability damage distribution part; 1-(D m ) m The corresponding probability damage threshold distribution part.

3. The method according to claim 1, characterized in that, A finite element model of the target material is constructed, and the probabilistic damage distribution of the weak region of the target material is determined by combining multi-source uncertainties under creep-fatigue loading. Specifically, this includes: A finite element model of the target material is established, and a creep-fatigue constitutive model of the target material is embedded in the finite element model to obtain a first embedded finite element model; The weak region is determined based on the first embedded finite element model combined with the stress-strain field of the target material; The creep-fatigue damage model is embedded in the first embedded finite element model to obtain the second embedded finite element model; The multi-source uncertainty factors are input into the second embedded finite element model to obtain the creep damage and fatigue damage of the steady-state cycles of the finite element response output; Based on the steady-state cycle creep damage and fatigue damage from the finite element response output, the probability damage distribution of the weak point region is statistically analyzed using probabilistic methods.

4. The method according to claim 1, characterized in that, The dispersion of the mechanical performance degradation exponent is quantified based on the experimental dataset composed of the aforementioned mechanical performance degradation parameters and interrupted life fractions, and the probability damage threshold distribution under different damage levels is obtained based on the dispersion, specifically including: The dispersion of the mechanical performance degradation exponent is quantified based on the experimental dataset composed of the mechanical performance degradation parameter and the interruption life fraction. Based on the aforementioned dispersion, determine the first mean and first standard deviation of the standard normal distribution of the probabilistic damage threshold under different damage levels; Based on the characteristic that the damage threshold is greater than 0, the standard normal distribution of the probability damage threshold is converted into a truncated normal distribution, and the second mean and the second standard deviation of the truncated normal distribution are determined based on the first mean and the first standard deviation. The probability density function of the truncated normal distribution is determined based on the first mean and the first standard deviation; the probability damage threshold distribution is determined by the second mean, the second standard deviation, and the probability density function.

5. The method according to claim 4, characterized in that, The expression for the second mean is: The expression for the second standard deviation is: The expression for the probability density function is: In the formula, D crit D is the damage threshold. crit =1-(D m ) m ; φ(·) and Φ(·) are the probability density function and cumulative distribution function of the standard normal distribution; μ(D m ) is the first mean; σ(D) m () represents the first standard deviation.

6. The method according to claim 1, characterized in that, The formula for calculating the failure probability is: P f =P(G(N d )<0) Among them, G(N) d ) = D crit -D(N d ) In the formula, P() represents the probability calculation method; G(N) d () represents the creep-fatigue damage accumulation criterion that considers mechanical property degradation; D crit Corresponding to the creep-fatigue damage accumulation criterion expression 1-(D m ) m ;D(N d The corresponding expression for the creep-fatigue damage accumulation criterion is...

7. The method according to claim 1 or 3, characterized in that, The multi-source uncertainties include the uncertainty of external input loads, the uncertainty of basic material performance parameters, and the uncertainty of creep-fatigue damage model parameters.

8. A reliability evaluation system based on cumulative damage-damage threshold interference, characterized in that, The system includes: The criterion construction module is used to conduct multiple sets of tests on the target material, calculate creep damage and fatigue damage based on the creep-fatigue damage model corresponding to the target material, and calculate mechanical property degradation parameters based on tensile plastic strain energy density; establish a creep-fatigue damage accumulation criterion considering mechanical property degradation based on the creep damage, the fatigue damage, and the mechanical property degradation parameters; the tests include interrupted creep-fatigue tests and interrupted tensile tests; The probability damage distribution determination module is used to construct a finite element model of the target material and determine the probability damage distribution of the weak area of ​​the target material in combination with multi-source uncertainty factors under creep-fatigue loading. The probability damage threshold distribution determination module is used to quantify the dispersion of the mechanical performance degradation exponent based on the test dataset composed of the mechanical performance degradation parameter and the interruption life fraction, and to obtain the probability damage threshold distribution under different damage levels based on the dispersion; the expression of the creep-fatigue damage accumulation criterion considering mechanical performance degradation includes a probability damage distribution part and a probability damage threshold distribution part. The failure calculation module is used to randomly sample probabilistic damage and probabilistic damage threshold based on the probabilistic damage distribution and the probabilistic damage threshold distribution, and to calculate the failure probability of the target material based on the sampled probabilistic damage and sampled probabilistic loss threshold using the cumulative damage-damage threshold interference theory; the reliability of the target material is represented by the failure probability. The reliability grading evaluation chart drawing module is used to draw a three-dimensional creep-fatigue reliability grading evaluation chart that varies with mechanical property degradation based on the failure probability, the mechanical property degradation parameter and the remaining safe life of the target material. The reliability evaluation module is used to determine the remaining safe life of the material to be evaluated based on the three-dimensional creep-fatigue reliability grading evaluation chart, the mechanical property degradation parameters of the material to be evaluated, and the preset failure probability of the material to be evaluated; and to determine the damage level of the material to be evaluated based on the mechanical property degradation parameters and the predefined relationship between the mechanical property degradation parameters and the damage level.

9. The system according to claim 8, characterized in that, The expression for the creep-fatigue damage accumulation criterion that considers mechanical property degradation is: in, In the formula, D c For creep damage; D f For fatigue damage; D m U is a parameter for mechanical property degradation. T(0) U represents the tensile plastic strain energy of the undamaged material. T(N) Let n be the tensile plastic strain energy of the material in the Nth cycle; n is the damage exponent, derived from the creep damage D. c and fatigue damage D f The damage envelope is obtained from the constructed test dataset; m is the power exponent of mechanical property degradation, derived from the mechanical property degradation parameter D. m The degenerative envelope, determined by the evolution law of the interrupted lifetime fraction, is obtained; D c n +D f n Corresponding probability damage distribution part; 1-(D m ) m The corresponding probability damage threshold distribution part.

10. The system according to claim 8, characterized in that, The probability damage distribution determination module specifically includes: The first embedded finite element model construction unit is used to establish the finite element model of the target material and embed the creep-fatigue constitutive model of the target material into the finite element model to obtain the first embedded finite element model; The weak region determination unit is used to determine the weak region based on the first embedded finite element model combined with the stress-strain field of the target material; The second embedded finite element model construction unit is used to embed the creep-fatigue damage model into the first embedded finite element model to obtain the second embedded finite element model. The finite element response unit is used to input the multi-source uncertainty factors into the second embedded finite element model to obtain the creep damage and fatigue damage of the steady-state cycle of the finite element response output. The probability damage distribution determination unit is used to statistically analyze the probability damage distribution of the weak point region based on the creep damage and fatigue damage of the steady-state cycles of the finite element response output using probabilistic methods.

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