Evaluation method for equivalent service life of wind power blade

Abstract

The invention discloses a method for evaluating the equivalent service life of a wind power blade. The method comprises the following steps: acquiring a wind power blade standard test sample; setting four-point bending fatigue experiment parameters; four-point fatigue bending experiments are carried out on the wind power blade standard test sample piece for specified times; obtaining an experimental spline; parameters of a static bending experiment are set, and the static bending performance of the experiment spline is tested; drawing a relation curve of the static bending modulus of the experimental spline and the fatigue times of the wind power blade standard test sample; and testing the static bending modulus of the wind power blade in actual service to obtain the equivalent service life of the wind power blade. According to the method, the modulus and the strength of a standard spline are obtained by designing the fatigue times of the wind power blade, then the quantitative relation between the modulus and the fatigue times is constructed, and a relation curve is obtained; by testing the bending modulus of the experimental spline and comparing the bending modulus with the modulus of the standard spline, the equivalent service life is obtained, the time consuming problem of large experimental sample piece testing is avoided, and the equivalent service life of the experimental spline can be quickly and accurately estimated.

Description

Technical Field

[0001] This application belongs to the field of wind turbine blade performance evaluation technology, and in particular relates to a method for evaluating the equivalent service life of wind turbine blades. Background Technology

[0002] Wind turbine blades are key components of wind turbine generators, playing a crucial role in capturing wind energy. In wind turbine blade design, to reduce overall blade mass, the shell typically employs a sandwich composite structure, consisting of two layers of skin (glass fiber reinforced epoxy resin) and a lightweight foam core. The lightweight foam core ensures stability, meets stiffness requirements, and reduces blade mass, while the sandwich structure transfers shear forces from the surface to the interior, thereby improving the blade's load-bearing capacity. However, wind turbine blades are subjected to complex alternating loads and harsh environments during service. The alternating tensile and compressive loads during actual operation can cause fatigue damage to the sandwich structure. Fatigue leads to microcracks in the blade matrix, causing stress concentration and further accelerating damage propagation, resulting in operational safety hazards in wind power operations. Severely damaged blades require scrapping and replacement, causing a surge in maintenance costs; the cost of a single 80-meter blade can reach 5 million to 10 million RMB. Therefore, to reduce the economic losses and safety risks caused by blade failure, evaluating the equivalent service life of the blades is particularly important.

[0003] In existing technologies, the equivalent service life of materials is mainly evaluated through fatigue testing. However, fatigue testing generally requires a lot of time, especially for full-scale testing. A full-life fatigue test of an 80-meter blade can take 18 to 24 months and is very expensive. Summary of the Invention

[0004] This application discloses a method for evaluating the equivalent service life of wind turbine blades to solve the problems in the prior art.

[0005] To achieve the above objectives, this invention provides a method for detecting high-resistance faults in a resonant grounding system of a power distribution network. The method includes the following steps: S1, obtaining a standard test sample of a wind turbine blade; S2, setting four-point bending fatigue test parameters; S3, conducting a specified number of four-point fatigue bending tests on the standard test sample of the wind turbine blade; S4, obtaining an experimental strip based on the standard test sample of the wind turbine blade; S5, setting parameters for a static bending test and testing the static bending performance of the experimental strip; S6, plotting the relationship curve between the static bending modulus of the experimental strip and the number of fatigue cycles of the standard test sample of the wind turbine blade, and obtaining the standard curves relating the bending modulus and bending strength of the original blade under a specific load to the number of fatigue cycles; S7, testing the static bending modulus of an actual wind turbine blade in service and comparing it with the standard test sample to obtain the equivalent service life of the wind turbine blade.

[0006] Optionally, step S6 includes the following steps: S601, plotting the relationship curve between the static bending modulus of the experimental spline and the fatigue number of a standard test specimen of the wind turbine blade; S602, calculating and fitting the standard curves of the relationship between the bending modulus and bending strength of the original blade under a specific load and the fatigue number based on the following formula:

[0007] y = 130 / x 2 + 20 (1)

[0008] In the formula, x is the number of fatigue cycles and y is the bending modulus;

[0009] y = 6 / x 2 + 3 (2)

[0010] In the formula, x represents the number of fatigue cycles and y represents the bending strength.

[0011] Optionally, the standard test specimen of the wind turbine blade shall meet the following conditions: Dimensions: 550mm long and 75mm wide; Orientation: weld seam is in the Y direction and groove is in the X direction.

[0012] Optionally, the four-point bending fatigue test parameters include: test standard, test environment, test equipment, and dimensions. The test standard is ASTM C393-2020, the test environment is a temperature of 23±2℃ and a humidity of 50±10%, the test equipment is a universal testing machine and a strain gauge, and the dimensions are actual measured values.

[0013] Optionally, the fatigue count ranges from 1 to 2 million times.

[0014] Compared with the prior art, the advantages or beneficial effects of the embodiments of this application are as follows:

[0015] This invention obtains the modulus and strength of a standard specimen by designing the fatigue number of wind turbine blades, and then constructs a quantitative relationship between the modulus and the fatigue number to obtain a relationship curve. By testing the bending modulus of the experimental specimen and comparing it with the modulus of the standard specimen, the equivalent service life is obtained. This effectively avoids the time-consuming problem of testing large experimental specimens and can quickly and accurately predict the equivalent service life of the experimental specimen. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 A flowchart illustrating a method for evaluating the equivalent service life of wind turbine blades provided in an embodiment of the present invention;

[0018] Figure 2 A schematic diagram of the standard test specimen for wind turbine blades provided in this application;

[0019] Figure 3 The wind turbine blade testing scheme provided in this application;

[0020] Figure 4 This is a schematic diagram of load loading provided in this application. Detailed Implementation

[0021] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0022] In the relevant description of this application, the term "and / or" is used to describe the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, B existing alone, and A and B existing simultaneously. Here, A and B can be singular or plural.

[0023] In the relevant descriptions of this application, the term "at least one" refers to one or more, while "multiple" refers to two or more. "At least one of the following" or similar descriptions refer to any combination of these items, including any combination of a single item or multiple items. For example, "at least one of A, B, or C," or "at least one of A, B, and C," both indicate one of A, B, and C, or A+B, or A+C, or B+C, or A+B+C, where A, B, and C can be single or multiple. In the relevant descriptions of this application, the order of the sequence numbers does not imply the order of execution. Some or all steps can be executed in parallel or sequentially. The execution order of each process should be specifically determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0024] In the description of this application, numerical ranges should be understood to specifically disclose each intermediate value between the upper and lower limits of the range. Each smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this application. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0025] Unless otherwise stated, the technical / scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art. While this application describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may be used in the implementation or experimentation of this application. Furthermore, all references to this application are incorporated by way of citation to disclose and describe the methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0026] refer to Figures 1-4 This application provides a method for evaluating the equivalent service life of wind turbine blades, which may include the following steps:

[0027] S1, Obtain standard test samples of wind turbine blades.

[0028] Figure 2 This is a schematic diagram of the standard test sample for wind turbine blades provided in this application, for reference only. Figure 2 In an exemplary embodiment, the standard test sample for wind turbine blades is obtained by cutting wind turbine blades, and the standard test sample for wind turbine blades must meet the following conditions:

[0029] Dimensions: Length 550mm, Width 75mm;

[0030] Direction: The weld seam is in the Y direction, and the groove direction is in the X direction.

[0031] S2, set the parameters for the four-point bending fatigue test.

[0032] In an exemplary embodiment, the four-point bending fatigue test parameters may include: test standard, test environment, test equipment, and dimensions. The test standard is ASTM C393-2020, the test environment is a temperature of 23±2℃ and a humidity of 50±10%, the test equipment is a universal testing machine and a strain gauge, and the dimensions are actual measured values.

[0033] Specifically, the testing equipment consists of an Instron 8801 universal testing machine and a Donghua DH5921B strain gauge, and the testing time for each sample (i.e., the standard test sample of the wind turbine blade) is 4 to 6 minutes.

[0034] S3 involves conducting a specified number of four-point fatigue bending tests on standard test specimens of wind turbine blades.

[0035] Specifically, the fatigue cycles obtained through the four-point fatigue bending test are shown in Table 1:

[0036] Table 1

[0037] Serial Number fatigue count spline 1 1 spline 2 2 spline 3 3 Spline 4 4 spline 5 5 Spline 6 10 Spline 7 100 Spline 8 1000 Spline 9 10000 Spline 10 100000 Spline 11 1000000 Spline 12 2000000

[0038] S4. Based on the standard test specimen of wind turbine blade, obtain the experimental spline.

[0039] S5. Set the parameters for the static bending test, setting the fatigue cycle range to 1 to 2 million cycles, and test the static bending performance of the experimental specimen. The obtained flexural modulus is shown in Table 2, and the obtained strength is shown in Table 3.

[0040] Table 2

[0041] Serial Number fatigue count Flexural modulus (MPa) Experiment 1 1 150.00 Experiment 2 2 52.50 Experiment 3 3 34.44 Experiment 4 4 28.13 Experiment 5 5 25.20 Experiment 6 10 21.30 Experiment 7 100 20.01 Experiment 8 1000 20.00 Experiment 9 10000 20.00 Experiment 10 100000 20.00 Experiment 11 1000000 20.00 Experiment 12 2000000 20.00

[0042] Table 3 Bending strength of experimental specimens

[0043]

[0044]

[0045] S6, plot the relationship curve between the static bending modulus of the experimental spline and the fatigue number of the standard test specimen of the wind turbine blade, and obtain the standard curves of the relationship between the bending modulus and bending strength of the original blade and the fatigue number under a specific load.

[0046] In an exemplary embodiment, step S6 may include the following steps: S601, plotting the relationship curve between the static bending modulus of the experimental spline and the fatigue number of a standard test specimen of the wind turbine blade; S602, calculating and fitting the standard curves of the relationship between the bending modulus and bending strength of the original blade under a specific load and the fatigue number based on the following formula:

[0047] y = 130 / x 2 + 20 (1)

[0048] In the formula, x is the number of fatigue cycles and y is the bending modulus;

[0049] y = 6 / x 2 + 3 (2)

[0050] In the formula, x represents the number of fatigue cycles and y represents the bending strength.

[0051] S7 tests the static bending modulus of the actual wind turbine blades in service and compares it with the standard test sample to obtain the equivalent service life of the wind turbine blades.

[0052] This invention obtains the modulus and strength of a standard specimen by designing the fatigue number of wind turbine blades, and then constructs a quantitative relationship between the modulus and the fatigue number to obtain a relationship curve. By testing the bending modulus of the experimental specimen and comparing it with the modulus of the standard specimen, the equivalent service life is obtained. This effectively avoids the time-consuming problem of testing large experimental specimens and can quickly and accurately predict the equivalent service life of the experimental specimen.

[0053] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0054] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of this application.

Claims

1. A method for evaluating the equivalent service life of wind turbine blades, characterized in that, The method includes the following steps: S1, Obtain standard test samples of wind turbine blades; S2, set the parameters for the four-point bending fatigue test; S3, conduct a specified number of four-point fatigue bending tests on standard test specimens of wind turbine blades; S4. Based on standard test specimens for wind turbine blades, obtain experimental splines; S5, set the parameters for the static bending test and test the static bending performance of the experimental spline; S6, plot the relationship curve between the static bending modulus of the experimental spline and the fatigue number of the standard test specimen of the wind turbine blade, and obtain the standard curves of the relationship between the bending modulus and bending strength of the original blade and the fatigue number under a specific load. S7 tests the static bending modulus of the actual wind turbine blades in service and compares it with the standard test sample to obtain the equivalent service life of the wind turbine blades.

2. The method for evaluating the equivalent service life of wind turbine blades according to claim 1, characterized in that, Step S6 includes the following steps: S601, plot the relationship curve between the static bending modulus of the experimental spline and the fatigue number of the standard test specimen of the wind turbine blade; S602, based on the following formula, calculate and fit the standard curves of the correlation between the bending modulus and bending strength of the original blade under a specific load and the number of fatigue cycles: y=130 / x 2 + 20 (1) In the formula, x is the number of fatigue cycles and y is the bending modulus; y=6 / x 2 + 3 (2) In the formula, x represents the number of fatigue cycles and y represents the bending strength.

3. The method for evaluating the equivalent service life of wind turbine blades according to claim 1, characterized in that, The standard test specimens for wind turbine blades must meet the following conditions: Dimensions: Length 550mm, Width 75mm; Direction: The weld seam is in the Y direction, and the groove direction is in the X direction.

4. The method for evaluating the equivalent service life of wind turbine blades according to claim 1, characterized in that, The four-point bending fatigue test parameters include: test standard, test environment, test equipment and dimensions. The test standard is ASTM C393-2020, the test environment is temperature 23±2℃ and humidity 50±10%, the test equipment is a universal testing machine and a strain gauge, and the dimensions are actual measured values.

5. The method for evaluating the equivalent service life of wind turbine blades according to claim 1, characterized in that, The range of fatigue counts is 1 to 2 million.

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