Fatigue reliability assessment method and system based on numerical analysis adjustment coefficient

Abstract

The present invention provides a fatigue reliability assessment method and system based on a numerical analysis adjustment coefficient, comprising: S1: obtaining at least the measured stress spectrum of test point 1 and test point 2; S2: analyzing the fatigue reliability of test point 1 and test point 2; S3: calculating the stress response adjustment coefficient of test point 1 and test point 2; S4: obtaining the stress spectrum of test point 2 based on the numerical analysis adjustment coefficient; S5: checking and correcting the numerical model; S6: calculating the adjustment coefficient of the fatigue details under the structural parameters to be studied; S7: analyzing the fatigue reliability of the fatigue details under the structural parameters to be studied; the assessment method proposed in the present invention obtains the stress ratio of the assessment target under specific structural parameters and the structural parameters to be studied, i.e., the adjustment coefficient, by combining on-site measurement and numerical analysis, and corrects the numerical model through the fatigue reliability index, so as to obtain the stress time history of fatigue details of different structural parameters under operating conditions, thereby realizing fatigue reliability assessment.

Description

Technical Field

[0001] The present invention belongs to the field of fatigue performance evaluation, and in particular relates to a fatigue reliability evaluation method and system based on a numerical analysis adjustment coefficient. Background Art

[0002] A key step in fatigue analysis of engineering structures is determining the fatigue stress spectrum. The stress history obtained from field tests can effectively assess the reliability of fatigue details. However, this method can only be used to test completed structures, i.e., with specific structural parameters, and cannot assess fatigue reliability under designs with other structural parameters.

[0003] Although the analysis of structural parameters can be assisted by numerical analysis or model tests, it is difficult to obtain the stress history under operational traffic conditions. Only force analysis or fatigue assessment based on deterministic methods can be carried out, but fatigue reliability assessment cannot be performed.

[0004] In recent years, some scholars have proposed using random sampling methods to extract load spectra, and then combining them with numerical analysis to obtain stress history. Although this method can carry out fatigue reliability assessment under different structural parameters, its stress data cannot objectively reflect the effects of operational traffic flow. At the same time, the load spectrum type also has limitations. A load spectrum that may be suitable for a certain project may not be used for another project. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention proposes a fatigue reliability assessment method based on a numerical analysis adjustment coefficient. By combining on-site measurements and numerical analysis, the stress ratio of the assessment target under specific structural parameters and the structural parameters to be studied, i.e., the adjustment coefficient, can be obtained. By correcting the numerical model through the fatigue reliability index, the stress history of fatigue details of different structural parameters under operating conditions can be obtained, thereby realizing efficient fatigue reliability assessment.

[0006] One aspect of the present invention provides a fatigue reliability assessment method based on a numerical analysis adjustment coefficient, comprising the following steps: S1: obtaining at least the measured stress spectrum of test point 1 and test point 2; S2: analyzing the fatigue reliability of test point 1 and test point 2; S3: calculating the stress response adjustment coefficient of test point 1 and test point 2; S4: obtaining the stress spectrum of test point 2 based on the numerical analysis adjustment coefficient; S5: checking and correcting the numerical model; S6: calculating the adjustment coefficient of the fatigue details under the structural parameters to be studied; S7: analyzing the fatigue reliability of the fatigue details under the structural parameters to be studied; the present invention proposes a fatigue reliability assessment method based on a numerical analysis adjustment coefficient. By combining on-site measurement and numerical analysis, the stress ratio of the assessment target under specific structural parameters and the structural parameters to be studied, that is, the adjustment coefficient, can be obtained, and the numerical model can be corrected by the fatigue reliability index, so that the stress time history of fatigue details of different structural parameters under operating conditions can be obtained, thereby realizing efficient assessment of fatigue reliability.

[0007] Preferably, S1 further includes: on-site strain testing, obtaining the stress history of test point 1 and test point 2 under the action of operational load, and converting the stress history into a stress spectrum by rain flow counting method.

[0008] Preferably, S2 further includes: establishing a fatigue limit state equation, calculating the probability statistical information of the action effect and fatigue resistance respectively, and drawing a relationship curve between the fatigue reliability index of the test point 1 and the test point 2 and the service time.

[0009] Preferably, S3 also includes: establishing a numerical model based on the actual engineering structure, extracting the stress responses of test point 1 and test point 2 under the same load, denoted as σ1 and σ2 respectively, and then the stress response adjustment coefficient k0 of test point 2 relative to test point 1 is expressed as: k0 = σ2 / σ1.

[0010] Preferably, S4 further includes: taking test point 1 as a reference, multiplying the measured stress history of test point 1 by the proportional factor k0 to obtain the converted stress history of test point 2, recorded as numerical analysis point 2, and obtaining the stress spectrum after processing by the rain flow counting method.

[0011] Preferably, S5 further includes: drawing a fatigue reliability index curve under the stress spectrum of the numerical analysis point 2, and comparing the fatigue reliability indexes of the numerical analysis point 2 and the test point 2.

[0012] Preferably, the fatigue reliability index further includes: determining the target reliability index based on engineering importance to achieve the measured fatigue life L2 and the numerical analysis fatigue life of the target reliability The error e of the numerical model is corrected to make the fatigue life prediction error e lower than the acceptable value of 5% in engineering applications. The error e is expressed as:

[0013] Preferably, S6 further includes: performing stress response analysis of fatigue details under the structural parameters to be studied based on the revised numerical model to obtain corresponding adjustment coefficients; and repeating S4 to extract stress spectra.

[0014] Preferably, S7 further includes: obtaining the stress spectrum of the test point 2 based on the numerical analysis adjustment coefficient, and according to the established fatigue limit state equation; and repeating S2 to solve the fatigue reliability index and predict the fatigue life.

[0015] One aspect of the present invention provides a fatigue reliability assessment system based on numerical analysis adjustment coefficients, using any of the fatigue reliability assessment methods described above.

[0016] According to the fatigue reliability assessment method and system of the present invention, an adjustment coefficient can be obtained based on numerical analysis, and structural parameter analysis of fatigue reliability can be efficiently carried out in combination with on-site actual measurements. In the reliability analysis of engineering structures, various forms of action effects such as internal force, deformation, and stress can be obtained based on numerical analysis. The reliability assessment under different structural parameters can be carried out using the method proposed in this technical solution, which can improve the efficiency of fatigue reliability assessment and save costs.

[0017] The beneficial effects of adopting the above technical solution are:

[0018] 1. By combining measured data with numerical model analysis, accurate assessment of fatigue reliability can be achieved, thus providing a scientific basis for the safe operation of engineering structures.

[0019] 2. By analyzing the fatigue detailed stress response under different structural parameters, we can guide the optimal design of engineering structures, improve their fatigue life and reduce the risk of structural failure.

[0020] 3. By modifying the numerical model and taking into account engineering importance, the accuracy of fatigue life prediction can be improved, thereby more accurately evaluating the fatigue performance of the structure and its remaining life.

[0021] 4. Through the analysis of fatigue reliability indicators and the prediction of fatigue life, corresponding maintenance management strategies can be formulated to repair or reinforce the structure in a timely manner, extend its service life and reduce maintenance costs.

[0022] 5. Through comprehensive evaluation of fatigue reliability indicators and fatigue life prediction, the safety of engineering structures can be improved and their stability and reliability in long-term operation can be guaranteed. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0024] Figure 1 This is a flow chart of a fatigue reliability assessment method based on numerical analysis adjustment coefficients provided by an embodiment of the present invention;

[0025] Figure 2 This is a stress time history diagram of test points 1-12 provided by an embodiment of the present invention;

[0026] Figure 3 This is a stress time history diagram of test points 2-12 provided by an embodiment of the present invention;

[0027] Figure 4 This is a stress cloud diagram of test points 1-12 provided by an embodiment of the present invention;

[0028] Figure 5 This is a stress cloud diagram of test points 2-12 provided by an embodiment of the present invention;

[0029] Figure 6 This is a stress time history diagram of numerical analysis points 2-12 provided by an embodiment of the present invention;

[0030] Figure 7 is a schematic diagram of fatigue reliability indicators provided by an embodiment of the present invention; DETAILED DESCRIPTION

[0031] The following describes embodiments of the present invention in detail, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and are not to be construed as limiting the present invention.

[0032] In one example, in order to improve the evaluation efficiency of the fatigue reliability of engineering structures, the fatigue reliability evaluation method based on numerical analysis adjustment coefficient proposed in the present invention mainly proposes a method for obtaining the stress history of fatigue details with different structural parameters under operating conditions. Based on the stress history of fatigue details under specific structural parameters obtained by existing field measurements, numerical analysis is carried out to obtain the stress response adjustment coefficients of fatigue details with different structural parameters, and the field-measured stress history of fatigue details under the structural parameters to be studied is calculated. According to the stress history, the load spectrum is extracted, the fatigue reliability index is calculated, and the numerical model is corrected accordingly.

[0033] The method can evaluate fatigue reliability under various structural parameters, improving the reliability and efficiency of engineering design. The invention has important guiding significance for the structural design of bridge engineering, industrial plant, shipbuilding engineering, mechanical engineering and other projects.

[0034] Specifically, the fatigue reliability assessment method based on numerical analysis adjustment coefficient includes the following implementation steps:

[0035] S1: Obtain the measured stress spectra of at least test point 1 and test point 2.

[0036] Specifically, two strain test points are selected at the fatigue details of the engineering structure and named as test point 1 and test point 2. It should be noted that test point 1 and test point 2 should represent key stress points that may appear on the engineering structure, such as connectors, cantilevered parts or other stress concentration areas. Strain measuring instruments are used to perform stress tests on test points 1 and test points 2, and real-time data collection is performed to record the strain time history of test points 1 and test points 2 under the action of structural operating loads. Data processing, including data smoothing, noise removal and other operations, is performed to ensure the reliability and accuracy of the data.

[0037] It can be understood that the rain flow counting method is used to convert complex stress or strain time history data into equivalent stress or strain cycle numbers, which is convenient for fatigue life prediction and reliability analysis. The rain flow counting method is usually used to deal with the complex load history of actual engineering structures, making it applicable to the standard method of fatigue life prediction.

[0038] The measured stress time history data are converted into corresponding stress cycle sequences using the rainflow counting method. The amplitude range and number of each cycle are identified and recorded, and a stress spectrum is established, which includes the number of cycles and amplitude range at each stress level.

[0039] S2: Analyze the fatigue reliability of test points 1 and 2.

[0040] Specifically, based on the measured stress spectra of test points 1 and 2, as well as the material properties and geometric parameters of the engineering structure, a fatigue limit state equation is established. This equation is used to describe the boundary state of failure of the engineering structure under fatigue load.

[0041] Using the probabilistic unified method, the effects of test points 1 and 2 at different service times are calculated based on the measured stress spectra and loading frequencies of test points 1 and 2 to understand the fatigue load effects borne by the structure at different working times, calculate the corresponding fatigue resistance, and determine the probabilistic statistical information of the effects and fatigue resistance based on reliability theory. The relationship curve of the fatigue reliability index of test points 1 and 2 as the service time of the engineering structure is plotted to understand the changing trend of the fatigue reliability of the engineering structure over time.

[0042] S3: Calculate the stress response adjustment coefficients of test point 1 and test point 2.

[0043] Specifically, a numerical model of the structure is established based on the actual engineering structure and known load conditions.

[0044] The positions of test points 1 and 2 are specified in the numerical model, and the corresponding stress analysis is performed. The stress response data of test points 1 and 2 under the same load are extracted and recorded as σ1 and σ2 respectively. The stress response adjustment coefficient k0 of test point 2 relative to test point 1 is calculated. The stress response adjustment coefficient k0 is expressed as: k0 = σ2 / σ1, which is used to quantify the stress response difference between test points 1 and 2.

[0045] S4: Obtain the stress spectrum of test point 2 based on the numerical analysis adjustment coefficient.

[0046] Specifically, test point 1 is selected as the reference point, and according to the previously calculated stress corresponding adjustment coefficient k0, the measured stress history of test point 1 is multiplied by the proportional factor k0 to obtain the converted stress history of test point 2. The converted stress history of test point 2 is named numerical analysis point 2, and the conversion and comparative analysis of the stress history data from test point 1 to test point 2 are realized. The converted stress history data of test point 2 are processed by the rain flow counting method, which helps to convert complex stress history data into equivalent fatigue cycles.

[0047] Based on the data processed by the rain flow counting method, the stress spectrum of the numerical analysis point 2 is generated, which reflects the stress change of the test point 2 under actual working conditions.

[0048] S5: Check and modify the numerical model.

[0049] Specifically, based on the stress spectrum data of numerical analysis point 2 obtained previously, the fatigue reliability index curve under the stress spectrum of numerical analysis point 2 is drawn. The stress spectrum data of numerical analysis point 2 is used, combined with the fatigue life prediction method and the reliability analysis model, to calculate the fatigue reliability index of numerical analysis point 2. The fatigue reliability index curve of numerical analysis point 2 is compared with the fatigue reliability index curve of test point 2, and the reliability change trends of the two under the same working conditions are compared, and the difference in structural fatigue performance represented by the difference is analyzed.

[0050] Based on the importance and safety requirements of the engineering structure, the target reliability index is determined. It is conceivable that the reliability index that meets the actual needs of the project is specified considering the special properties and practical environment of the engineering structure.

[0051] Based on the measured fatigue life L2 and numerical analysis fatigue life Calculate the fatigue life error e between the two. The expression of fatigue life error e is: Based on the calculated fatigue life error e, the numerical model is modified so that its fatigue life prediction error e is lower than the acceptable value of 5% for engineering applications. The parameters and assumptions of the numerical model are adjusted to reduce the error of fatigue life prediction and improve the accuracy and reliability of the model.

[0052] Verify whether the revised numerical model meets the reliability requirements of engineering applications, and analyze the difference between the revised fatigue life prediction results and the measured fatigue life.

[0053] S6: Calculate the adjustment coefficient of fatigue details under the structural parameters to be studied.

[0054] Specifically, according to the different value ranges of the structural parameters to be studied, the corresponding fatigue detail parameters are set, such as material strength, structural geometry, loading frequency, etc.

[0055] Using the revised numerical model, the stress response analysis of fatigue details under the structural parameters to be studied is carried out to obtain new stress history data. Based on the new stress history data, the corresponding adjustment coefficients are calculated. These adjustment coefficients will reflect the degree of influence of different structural parameters on the stress response.

[0056] Based on the revised numerical model and the obtained adjustment coefficient, they were applied to the previous S4 to obtain the corresponding adjusted stress time history data. The adjusted stress time history data were processed by the rain flow counting method to obtain the corresponding stress spectrum.

[0057] S7: Analyze the fatigue reliability of fatigue details under the structural parameters to be studied.

[0058] Specifically, based on the adjustment coefficient obtained in the numerical analysis, the stress spectrum data of the test point 2 is obtained, and the stress spectrum of the test point 2 is calculated and extracted using the adjusted numerical analysis results.

[0059] According to the fatigue limit state equation established previously, the stress spectrum data of test point 2 is substituted into the equation for analysis. Based on the fatigue limit state equation, the fatigue performance of the structure under actual working conditions is evaluated and the fatigue life is predicted.

[0060] Based on the results of applying the fatigue limit state equation, the fatigue reliability index of test point 2 is solved using the corresponding reliability analysis method.

[0061] According to the solution of fatigue reliability index, the fatigue life of test point 2 under actual working conditions is predicted.

[0062] This example examines an orthotropic steel bridge structure, conducting an on-site strain test of the notch details under actual traffic loads. Two test points, designated as test points 1-12 and 2-12, correspond to 10 mm and 12 mm thick diaphragms, respectively.

[0063] The stress history of test points 1-12 and test points 2-12 is as follows: Figure 2 and Figure 3 As shown, they are recorded as test points 1-12 and test points 2-12 respectively. A refined finite element analysis model is established through ANSYS. The stress cloud diagrams of test points 1-12 and test points 2-12 are obtained by numerical analysis as shown below. Figure 4 and Figure 5 As shown in Figure 2, the nominal stresses used for fatigue assessment under load are 70.1 MPa and 63.3 MPa respectively (6 mm away from the stress concentration point of the structural details).

[0064] Furthermore, taking the test point 1-12 as the benchmark, the adjustment coefficient k0=0.90, and multiplying the measured stress time history of the test point 1-12 by the adjustment coefficient k0, the stress time history of the test point 2-12 after numerical analysis conversion can be obtained, which is recorded as the numerical analysis point 2-12, as shown in FIG. Figure 6 As shown, the stress spectrum can be obtained by using the rain flow counting method.

[0065] By conducting fatigue reliability analysis based on reliability theory, the fatigue reliability indicators under the above three stress time histories can be obtained. Figure 7 The relationship between the fatigue reliability index of test points 1-12, test points 2-12 and numerical analysis points 2-12 and service time is given.

[0066] Furthermore, according to the importance of the project, the fatigue reliability index is taken as 3.72, and the failure probability is 10 -4 It can be seen that compared with the fatigue evaluation life of test point 2-12, the fatigue life error of numerical analysis point 2-12 is 3.75%, which is less than 5% and meets the requirements.

[0067] It should be pointed out that if the fatigue life prediction error is greater than 5%, the finite element model needs to be adjusted, such as the mesh unit size, load application method, and boundary conditions, until the fatigue life prediction error is finally reduced to less than 5%. The numerical model is accurate enough to meet the requirements of engineering applications.

[0068] It is conceivable that in this example, the numerical analysis model can be used to further solve the stress response under other structural details or different structural parameters, obtain the adjustment coefficient, extract the stress spectrum, calculate the fatigue reliability index, and predict the fatigue life.

[0069] In summary, the technical solution proposed in this invention can efficiently perform fatigue reliability analysis of structural parameters by deriving adjustment coefficients based on numerical analysis and combining them with field measurements. In reliability analysis of engineering structures, numerical analysis can be used to determine various effects such as internal forces, deformations, and stresses. The proposed method can be used to conduct reliability assessments under different structural parameters, improving the efficiency of fatigue reliability assessments and saving costs.

[0070] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0071] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A fatigue reliability assessment method based on numerical analysis adjustment coefficient, characterized in that: include: S1: Obtain the measured stress spectra of at least test point 1 and test point 2; S2: Analyze the fatigue reliability of test points 1 and 2; S3: Calculate the stress response adjustment coefficients of test point 1 and test point 2; Among them, a numerical model is established according to the actual engineering structure, and the stress response data of test point 1 and test point 2 under the same load are extracted and recorded as 、 , calculate the stress response adjustment coefficient of test point 2 relative to test point 1 , stress response adjustment coefficient Expressed as: ; S4: Obtain the stress spectrum of test point 2 based on the numerical analysis adjustment coefficient; S5: Check and modify the numerical model; S6: Calculate the adjustment coefficient of fatigue details under the structural parameters to be studied; S7: Analyze the fatigue reliability of fatigue details under the structural parameters to be studied.

2. The fatigue reliability evaluation method according to claim 1, characterized in that: The S1 also includes: On-site strain testing was performed to obtain the stress time histories at test points 1 and 2 under operational loads, and the stress time histories were converted into stress spectra using the rainflow counting method.

3. The fatigue reliability evaluation method according to claim 1, characterized in that: S2 also includes: The fatigue limit state equation is established, the probability statistical information of the action effect and fatigue resistance are calculated respectively, and the relationship curve between the fatigue reliability index of test point 1 and test point 2 and the service time is plotted.

4. The fatigue reliability evaluation method according to claim 1, characterized in that: The S4 also includes: Taking test point 1 as the benchmark, multiply the measured stress history of test point 1 by the proportional factor , the converted stress time history of test point 2 can be obtained, which is recorded as numerical analysis point 2. The stress spectrum can be obtained after processing by the rain flow counting method.

5. The fatigue reliability evaluation method according to claim 4, characterized in that: The S5 also includes: Draw the fatigue reliability index curve under the stress spectrum of numerical analysis point 2, and compare the fatigue reliability index of numerical analysis point 2 with that of test point 2.

6. The fatigue reliability evaluation method according to claim 5, characterized in that: The fatigue reliability index also includes: Determine target reliability indicators based on engineering importance to achieve the measured fatigue life at the target reliability and numerical analysis of fatigue life Error Correct the numerical model to make its fatigue life prediction error 5% lower than the accepted value for engineering applications, the error The expression is: .

7. The fatigue reliability evaluation method according to claim 6, characterized in that: The S6 also includes: Based on the revised numerical model, the stress response analysis of fatigue details under the structural parameters to be studied is carried out to obtain the corresponding adjustment coefficients; Repeat S4 to extract the stress spectrum.

8. The fatigue reliability evaluation method according to claim 7, characterized in that: The S7 also includes: Based on the numerical analysis adjustment coefficient, the stress spectrum of test point 2 is obtained according to the established fatigue limit state equation; Repeat S2 to solve the fatigue reliability index and predict the fatigue life.

9. A fatigue reliability assessment system based on numerical analysis adjustment coefficient, characterized in that: Use the fatigue reliability evaluation method described in any one of claims 1 to 8.

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