Welding structure reliability evaluation method based on fatigue performance margin quantification

Abstract

The invention belongs to the technical field of welding, and particularly relates to a welding structure reliability evaluation method based on fatigue performance margin quantification, which comprises the following steps: S1, acquiring related information according to fatigue failure characteristics of a welding structure, the related information comprises the amplitude of the load borne by the welding structure, the type of the load, the characteristic size of the defect / non-uniform microstructure, the depth of the defect / non-uniform microstructure and material attribute information. According to the welding structure reliability evaluation method based on fatigue performance margin quantification, metal material microstructure characteristic parameters are introduced for reliability evaluation of the fatigue performance margin of the welding structure, the influence of multi-source uncertainty factors is fully considered, and the reliability of the welding structure is evaluated by integrating measured data and an established theoretical model. Optimal distribution of uncertainty parameters is obtained under joint driving of data and the model, and then a fatigue performance margin reliability model of the welding structure is established by combining a life threshold value.

Description

Technical Field

[0001] The invention relates to the technical field of welding, and in particular to a reliability assessment method for a welding structure based on fatigue performance margin quantification. Background Art

[0002] In engineering organizations, welding is an important form of structural connection and is widely used in aerospace, shipbuilding, bridge construction, petrochemical and other fields. However, due to the inevitable defects and stress concentration in the welding process, welded structures are extremely susceptible to fatigue damage during service, resulting in a significant reduction in their reliability and service life. Fatigue damage is one of the main causes of failure of welded structures, and its occurrence and expansion process is complex and random. Therefore, accurately evaluating the fatigue performance and reliability of welded structures has become a key technical problem to ensure their safety and extend their service life.

[0003] Traditional fatigue assessment methods are mainly based on nominal stress method, hot spot stress method and fracture mechanics method. These methods can predict fatigue life to a certain extent, but when faced with complex stress states and multiple random factors, the prediction accuracy is still insufficient and has certain limitations. In recent years, with the development of engineering structure reliability theory, quantitative assessment methods based on fatigue performance margin have gradually received attention. Fatigue performance margin refers to the ability of an engineering structure to withstand additional stress or load before reaching fatigue failure, which can reflect the potential of the structure to resist fatigue damage.

[0004] For example, in the prior art, the Chinese patent "Method for Designing Mechanical Structure Performance Margin Based on Physical Modeling" (application number: CN 2023116825361) establishes the relationship between performance parameters and design parameters from a macroscopic scale, and then quantifies the performance margin and reliability of the design parameters. In addition, the Chinese patent "Method for Establishing a Reliability Margin Model for Aerospace Agency Products" (application number: CN2021100184556) establishes a reliability margin model based on environmental data. However, these models all take into account the influence of uncertainty in the microstructure of structural materials, and thus cannot more comprehensively reflect the fatigue performance of welded structures.

[0005] Therefore, the study of the reliability assessment method of welded structures based on the quantification of fatigue performance margin has important theoretical significance and engineering application value. Through this study, we can not only deepen the understanding of the fatigue behavior of welded structures, but also provide new ideas and methods for the design, manufacture and maintenance of welded structures, and ultimately achieve the goal of improving the reliability of welded structures. Summary of the invention

[0006] Based on the existing technical problems, the present invention proposes a welding structure reliability assessment method based on fatigue performance margin quantification.

[0007] The present invention proposes a method for evaluating the reliability of a welded structure based on the quantification of fatigue performance margin, comprising the following steps:

[0008] S1. Obtain relevant information based on fatigue failure characteristics of welded structures, including: load amplitude and load type borne by welded structures, characteristic size of defects / inhomogeneous microstructures, depth of defects / inhomogeneous microstructures, and material property information;

[0009] S2. Establish a fatigue index parameter Z model based on the relevant information of fatigue failure characteristics of welded structures;

[0010] S3. Establish a life prediction model for welding structures;

[0011] S4. Conduct uncertainty analysis and quantification of performance parameters in fatigue life margin model of welded structures;

[0012] S5. Determine the mean and variance of the fatigue probability life of the welded structure;

[0013] S6. Determine the life threshold N of fatigue failure of welded structures th ;

[0014] S7. Establishing the function of fatigue performance margin of welded structure;

[0015] S8. Establish a correlation model between the fatigue performance margin function and reliability of the welded structure to evaluate the reliability of the fatigue performance margin of the welded structure.

[0016] Preferably, S2 includes:

[0017] S21. Establishing fatigue index parameter Z model:

[0018]

[0019] Among them, σ a is the stress amplitude, is the characteristic size of defects or inhomogeneous microstructures, d is the depth of defects / inhomogeneous microstructures, β and α are material-related parameters, R is the stress ratio, and Y is the inclusion shape factor. For 3D inclusions including spherical inclusions and clustered inclusions, the Y value is equal to 1, while for 2D faceted inclusions, the Y value is between 0.85 and 0.95.

[0020] Among them, for 2D faceted inclusions, the Y value is preferably 0.9.

[0021] Preferably, S3 includes:

[0022] S31. Establishing a lifespan prediction model:

[0023]

[0024] Among them, A and B are fitting parameters, which are related to Z and N f The value of is related.

[0025] Preferably, the S31 includes:

[0026] S311, for N f (σ a ) to analyze the sources of uncertainty;

[0027] S312, parameters D. σ a The uncertainty of , α, and β is quantified and expressed as:

[0028] P(θ|D)=cp(D|θ)P(θ)

[0029] Among them, P(θ|D) represents the posterior distribution of the fatigue life performance margin model parameters; c is the evidence value, which plays a normalization role (ensuring that the integral of the posterior distribution is 1); P(θ) is the prior distribution, which is usually selected based on practical experience; p(D|θ) is the likelihood function, and θ represents the probability of obtaining D under the known premise.

[0030] Preferably, the S312 includes determining a likelihood function:

[0031]

[0032] Among them, y(k) is the response data of the real model, and g(k;θ) is the theoretical model data.

[0033] Preferably, S5 includes:

[0034] S51. The mean value of fatigue life is expressed as:

[0035]

[0036] S52. The variance of fatigue life is expressed as:

[0037]

[0038] Preferably, the step S6 includes obtaining the design life of the welded structure, i.e., the life threshold N, according to the service load. th .

[0039] Preferably, the S7 includes:

[0040] S71. The fatigue performance margin model of welded structure is:

[0041] m(σ a )=[N th]-N f (σ a ).

[0042] Preferably, the S71 includes determining a limit state function of a fatigue performance margin model:

[0043]

[0044] Preferably, the S8 includes:

[0045] S81. Establish a correlation model between fatigue performance margin assessment of welded structures and traditional reliability estimation:

[0046] R(σ)=Φ[β(σ)]

[0047] Where Φ(·) represents the standard normal distribution function;

[0048] S82. According to step S81, the fatigue reliability of the welded structure based on the fatigue performance margin quantification is calculated.

[0049] The beneficial effects of the present invention are:

[0050] The present invention aims at the reliability assessment of fatigue performance margin of welded structure, introduces the characteristic parameters of the microstructure of metal materials, fully considers the influence of multi-source uncertainty factors, integrates the measured data with the established theoretical model, obtains the optimal distribution of uncertainty parameters under the joint drive of data and model, and then establishes the reliability model of fatigue performance margin of welded structure in combination with the life threshold.

[0051] Compared with the prior art, the present invention aims at the reliability assessment of the fatigue performance margin of the welded structure, taking into account the coupling of the microstructure morphological characteristics and the load. It can not only be used for various types of welded structures, but also can effectively improve the life prediction accuracy of the welded components under service conditions, thereby ensuring the safe and stable operation of the entire welded component and achieving higher economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 A schematic diagram of a welded structure reliability assessment method based on fatigue performance margin quantification proposed by the present invention;

[0053] Figure 2 A schematic diagram of a socket welding structure of a welding structure reliability assessment method based on fatigue performance margin quantification proposed by the present invention;

[0054] Figure 3 It is a probability distribution diagram of uncertainty parameters of a welding structure reliability assessment method based on fatigue performance margin quantification proposed by the present invention;

[0055] Figure 4This is a schematic diagram of the variation of fatigue performance margin of a socket welded component with the number of cycles in a welding structure reliability assessment method based on fatigue performance margin quantification proposed by the present invention. DETAILED DESCRIPTION

[0056] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0057] Reference Figure 1-4 , a reliability assessment method for welded structures based on fatigue performance margin quantification, such as Figure 1 As shown, including:

[0058] Step S1: Obtain relevant information based on fatigue failure characteristics of the welded structure, including: load amplitude and load type borne by the welded structure, characteristic size of defect / inhomogeneous microstructure, depth of defect / inhomogeneous microstructure and material property information;

[0059] Step S2: Establishing fatigue index parameter Z model;

[0060] Step S3: Establishing a welding structure life prediction model;

[0061] Step S4: performing uncertainty analysis and quantification on performance parameters in the fatigue life margin model of the welded structure;

[0062] Step S5: determining the mean and variance of the fatigue probability life of the welded structure;

[0063] Step S6: determining a life threshold Nth of fatigue failure of the welded structure;

[0064] Step S7: establishing a functional function of the fatigue performance margin of the welded structure;

[0065] Step S8: Establish a correlation model between the fatigue performance margin function and reliability of the welded structure, and evaluate the fatigue performance margin reliability of the welded structure. Next, take the insertion welded structure as an example to explain this embodiment in detail.

[0066] In this embodiment, in step S2, for the socket welding structure, such as Figure 2 As shown in the figure, fatigue tests were carried out under the conditions of test temperature T = 25 °C and stress ratio R = 0.1. The applied stress amplitude was the stress amplitude σ borne by the inserted welding structure under 5 typical operating conditions. a1 , σ a2 , σ a3 , σ a4 , σ a5 . Obtain data points of different stress amplitudes and corresponding failure lives.

[0067] In step S2, the area of ​​the crack source defect of the failure fracture is measured according to the failure fracture morphology, recorded as area, and the arithmetic square root of the area is taken. As the characteristic size of the defect. Then measure the distance between the defect and the fracture surface, recorded as d. The value range of β parameter is 0~1.

[0068] In step S2, a fatigue index parameter Z is defined, and according to step S21, a fatigue index parameter Z model is established:

[0069]

[0070] Among them, σ a is the stress amplitude, is the characteristic size of defects or inhomogeneous microstructures, d is the depth of defects / inhomogeneous microstructures, β and α are material-related parameters, R is the stress ratio, and Y is the inclusion shape factor. For 3D inclusions including spherical inclusions and clustered inclusions, the Y value is equal to 1, while for 2D faceted inclusions, the Y value is between 0.85 and 0.95, wherein for 2D faceted inclusions, the Y value is preferably 0.9.

[0071] In step S3, a fatigue life prediction model is established based on the life and fatigue index parameters Z obtained at different stress amplitudes:

[0072]

[0073] Among them, A and B are fitting parameters, which are related to Z and N f The value of is related.

[0074] In step S311, the uncertainty parameter σ is determined a , D, α, β, these uncertainty parameters are assumed to be normally distributed;

[0075] In step S312, according to Bayesian theory, the posterior distribution of the uncertainty parameter is expressed as:

[0076] P(θ|D)=cp(D|θ)P(θ)

[0077] Among them, P(θ|D) represents the posterior distribution of the fatigue life performance margin model parameters; c is the evidence value, which plays a normalization role (ensuring that the integral of the posterior distribution is 1); P(θ) is the prior distribution, which is usually selected based on practical experience; p(D|θ) is the likelihood function, and θ represents the probability of obtaining D under the known premise.

[0078] In step S312, the likelihood function p(D|θ) is:

[0079]

[0080] Among them, y(k) is the response data of the real model, and g(k;θ) is the theoretical model data.

[0081] In step S312, the Monte Carlo method is used to perform random sampling on the posterior distribution of the uncertainty parameter to obtain a large amount of data;

[0082] In step S312, the distribution characteristics of the uncertainty parameter type are obtained according to the sampled data distribution.

[0083] In step S51, according to N f The distribution of fatigue life is determined to be

[0084]

[0085] In step S52, according to N f The distribution of fatigue life is determined as:

[0086]

[0087] In step S5, according to N f The mean and variance of the fatigue life are determined by Figure 3 As shown:

[0088] In step S6, the design life of the foundation welding structure is determined by determining the fatigue failure life threshold N th .

[0089] In step S71, according to the distribution of uncertainty parameters and fatigue life failure threshold, a fatigue performance margin model of the welded structure is established as

[0090] m(σ a )=[N th ]-N f (σ a ).

[0091] In step S7, a limit state function is established according to the fatigue performance margin model of the welded structure in step S71:

[0092]

[0093] In step S8, the reliability of the fatigue performance margin of the welded structure is evaluated according to the limit state function:

[0094]

[0095] The obtained fatigue performance margin reliability of the welded structure is shown in the table:

[0096]

[0097] In this embodiment, after the fatigue performance margin model of the welded structure is obtained through the above step S8, the model is used to predict the probability distribution of the fatigue performance margin of the welded structure, so as to consider the influence of the microstructure in the welded structure on the fatigue performance margin. In this embodiment, in order to verify the accuracy of the model, the actual test life distribution can also be compared with the predicted fatigue life to verify the accuracy of the fatigue performance margin reliability model of the welded structure.

[0098] The present invention aims at the reliability assessment of fatigue performance margin of welded structure, introduces the characteristic parameters of the microstructure of metal materials, fully considers the influence of multi-source uncertainty factors, integrates the measured data with the established theoretical model, obtains the optimal distribution of uncertainty parameters under the joint drive of data and model, and then establishes the reliability model of fatigue performance margin of welded structure in combination with the life threshold.

[0099] Compared with the prior art, the present invention aims at the reliability assessment of the fatigue performance margin of the welded structure, taking into account the coupling of the microstructure morphological characteristics and the load. It can not only be used for various types of welded structures, but also can effectively improve the life prediction accuracy of the welded components under service conditions, thereby ensuring the safe and stable operation of the entire welded component and achieving higher economic benefits.

[0100] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A reliability assessment method for a welded structure based on fatigue performance margin quantification, characterized in that: The following steps are involved: S1. Obtain relevant information based on fatigue failure characteristics of welded structures, including: load amplitude and load type borne by welded structures, characteristic size of defects / inhomogeneous microstructures, depth of defects / inhomogeneous microstructures, and material property information; S2. Establish a fatigue index parameter Z model based on the relevant information of fatigue failure characteristics of welded structures; S3. Establish a life prediction model for welding structures; S4. Conduct uncertainty analysis and quantification of performance parameters in fatigue life margin model of welded structures; S5. Determine the mean and variance of the fatigue probability life of the welded structure; S6. Determine the life threshold N of fatigue failure of welded structures th ; S7. Establishing the function of fatigue performance margin of welded structure; S8. Establish a correlation model between the fatigue performance margin function and reliability of the welded structure to evaluate the reliability of the fatigue performance margin of the welded structure.

2. A welding structure reliability assessment method based on fatigue performance margin quantification according to claim 1, characterized in that: The S2 includes: S21. Establish fatigue index parameter Z model: Among them, σ a is the stress amplitude, is the characteristic size of defects or inhomogeneous microstructures, d is the depth of defects / inhomogeneous microstructures, β and α are material-related parameters, R is the stress ratio, and Y is the inclusion shape factor. For 3D inclusions including spherical inclusions and clustered inclusions, the Y value is equal to 1, while for 2D faceted inclusions, the Y value is between 0.85 and 0.

95.

3. A welding structure reliability assessment method based on fatigue performance margin quantification according to claim 2, characterized in that: The S3 includes: S31. Establishing a lifespan prediction model: Among them, A and B are fitting parameters, which are related to Z and N f The value of is related.

4. A method for reliability assessment of welded structures based on fatigue performance margin quantification according to claim 3, characterized in that: The S31 includes: S311, for N f (σ a ) to analyze the sources of uncertainty; S312, parameters D. σ a The uncertainty of , α, and β is quantified and expressed as: P(θD)=cp(Dθ)P(θ) Among them, P(θD) represents the posterior distribution of the fatigue life performance margin model parameters; c is the evidence value, which plays a normalization role (ensuring that the integral of the posterior distribution is 1); P(θ) is the prior distribution, which is usually selected based on practical experience; p(Dθ) is the likelihood function, and θ represents the probability of obtaining D under the known premise.

5. A method for reliability assessment of welded structures based on fatigue performance margin quantification according to claim 4, characterized in that: The S312 includes determining a likelihood function: Among them, y(k) is the response data of the real model, and g(k;θ) is the theoretical model data.

6. A method for reliability assessment of welded structures based on fatigue performance margin quantification according to claim 5, characterized in that: The S5 includes: S51. The mean value of fatigue life is expressed as: S52. The variance of fatigue life is expressed as:

7. A welding structure reliability assessment method based on fatigue performance margin quantification according to claim 6, characterized in that: The step S6 includes obtaining the design life of the welded structure according to the service load, that is, the life threshold N th .

8. A welded structure reliability assessment method based on fatigue performance margin quantification according to claim 7, characterized in that: The S7 includes: S71. The fatigue performance margin model of welded structure is: m(s a )=[N th ]-N f (s a )。 9. A method for reliability assessment of a welded structure based on fatigue performance margin quantification according to claim 8, characterized in that: The step S71 includes determining the limit state function of the fatigue performance margin model:

10. The method for reliability assessment of a welded structure based on fatigue performance margin quantification according to claim 1, characterized in that: The S8 includes: S81. Establish a correlation model between fatigue performance margin assessment of welded structures and traditional reliability estimation: R(σ)=Φ[β(σ)] Where Φ(·) represents the standard normal distribution function; S82. According to step S81, the fatigue reliability of the welded structure based on the fatigue performance margin quantification is calculated.

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