Method for determining opening direction of flange and method and device for evaluating fatigue of flange bolt

Abstract

The invention provides a flange opening direction determination method and a flange bolt fatigue evaluation method and device. The determination method comprises the steps of obtaining a time sequence load of a to-be-evaluated flange under an original coordinate system and an inflection point load of an external load-internal force curve of the to-be-evaluated flange; determining a plurality of to-be-evaluated directions along the circumferential direction of the to-be-evaluated flange; for each to-be-evaluated direction in the plurality of to-be-evaluated directions, determining a projection of the time sequence load in the to-be-evaluated direction as a projection time sequence load of the to-be-evaluated direction; the inflection point load of the external load-internal force curve serves as a reference, statistical processing is conducted on the projection time sequence load, a reference fatigue index of the to-be-evaluated direction is obtained, and the reference fatigue index is used for representing the opening frequency of the to-be-evaluated flange in the to-be-evaluated direction; and according to the reference fatigue index of each to-be-evaluated direction in the plurality of to-be-evaluated directions, determining one to-be-evaluated direction from the plurality of to-be-evaluated directions as the opening direction of the to-be-evaluated flange, thereby facilitating improvement of fatigue analysis accuracy.

Description

Technical Field

[0001] The present disclosure relates to the field of wind power, and more specifically, to a method for determining a flange opening direction, and a method and device for evaluating flange bolt fatigue. Background Art

[0002] In the wind turbine industry, fatigue analysis of bolts on connecting flanges currently relies on the finite element method (FEM) to calculate the internal forces of the bolts under external loads, and then calculate the equivalent fatigue load based on these internal forces. However, the FEM calculation of bolt internal forces is based on a fixed coordinate system, and the final internal force of the bolt is the direct summation of the internal forces in all directions within the fixed coordinate system. If the flange is not significantly opened, the analysis results are generally more accurate because the internal forces generally vary linearly with the external load. However, when the flange is opened, the analysis results ignore nonlinear effects and underestimate the alternating amplitude of the bolt internal forces, thus affecting the accuracy of the fatigue analysis. Therefore, analyzing the directions with the most severe or relatively severe flange opening can help improve the accuracy of the fatigue analysis. Summary of the Invention

[0003] Therefore, how to determine the direction in which the flange opening is the most serious or relatively serious is crucial to improving the accuracy of fatigue analysis.

[0004] In a general aspect, a method for determining a flange opening direction is provided, the method comprising: obtaining a time-series load of the flange to be evaluated in an original coordinate system and an inflection point load of an external load-internal force curve of the flange to be evaluated, wherein the external load-internal force curve is used to represent the relationship between the external load of the flange to be evaluated and the internal force of the flange bolts of the flange to be evaluated; determining a plurality of directions to be evaluated along the circumference of the flange to be evaluated; for each of the plurality of directions to be evaluated, determining a projection of the time-series load on the direction to be evaluated as the projected time-series load of the direction to be evaluated; performing statistical processing on the projected time-series load with reference to the inflection point load of the external load-internal force curve to obtain a reference fatigue index of the direction to be evaluated, wherein the reference fatigue index is used to represent the opening frequency of the flange to be evaluated in the direction to be evaluated; and determining a direction to be evaluated from the plurality of directions to be evaluated according to the reference fatigue index of each of the plurality of directions to be evaluated as the opening direction of the flange to be evaluated.

[0005] Optionally, the projected time series load is statistically processed with the inflection point load of the external load-internal force curve as a reference to obtain a reference fatigue index of the direction to be evaluated, including: performing cycle counting processing on the projected time series load to obtain multiple projected load cycles; for each projected load cycle in the multiple projected load cycles, when at least part of the load in the projected load cycle is greater than or equal to the inflection point load of the external load-internal force curve, determining the projected load cycle as a reference cycle; based on the determined reference cycle, performing statistical processing on the multiple projected load cycles to obtain a reference fatigue index of the direction to be evaluated.

[0006] Optionally, based on the determined reference cycle, the multiple projected load cycles are statistically processed to obtain the reference fatigue index of the direction to be evaluated, including: for each of the multiple projected load cycles, determining the equivalent fatigue of the projected load cycle, and recording the equivalent fatigue of the reference cycle as reference equivalent fatigue; for the multiple projected load cycles, determining the proportion of the reference equivalent fatigue in all equivalent fatigue as the reference fatigue index of the direction to be evaluated.

[0007] Optionally, determining the equivalent fatigue of each of the multiple projected load cycles includes: determining the load amplitude and number of cycles of the projected load cycle for each of the multiple projected load cycles; and determining the product of the exponential power of the load amplitude and the number of cycles as the equivalent fatigue of the projected load cycle.

[0008] Optionally, for each of the multiple projected load cycles, when at least part of the load in the projected load cycle is greater than or equal to the inflection point load of the external load-internal force curve, the projected load cycle is determined as a reference cycle, including: for each of the multiple projected load cycles, determining the load peak value and the load valley value in the projected load cycle; when at least one of the load peak value and the load valley value is greater than or equal to the inflection point load of the external load-internal force curve, determining the projected load cycle as the reference cycle.

[0009] In another general aspect, a flange bolt fatigue assessment method is provided, the flange bolt fatigue assessment method comprising: determining the opening direction of the flange to be assessed based on the time-series load of the flange to be assessed in the original coordinate system; constructing a spatial coordinate system based on the opening direction and axial direction of the flange to be assessed, recorded as the assessment coordinate system; converting the time-series load from the original coordinate system to the assessment coordinate system to obtain an assessment time-series load; and performing fatigue assessment on the flange bolts of the flange to be assessed based on the assessment time-series load; wherein the opening direction of the flange to be assessed is obtained by the flange opening direction determination method according to an embodiment of the present disclosure.

[0010] In another general aspect, a device for determining the opening direction of a flange is provided, the device comprising: an acquisition unit configured to acquire a time-series load of the flange to be evaluated in an original coordinate system and an inflection point load of an external load-internal force curve of the flange to be evaluated, wherein the external load-internal force curve is used to represent the relationship between the external load of the flange to be evaluated and the internal force of the flange bolts of the flange to be evaluated; a determination unit configured to determine a plurality of directions to be evaluated along the circumference of the flange to be evaluated; and a projection unit configured to determine, for each of the plurality of directions to be evaluated, the time-series load in the original coordinate system. The projection on the direction to be evaluated serves as the projected time-series load in the direction to be evaluated; the statistical unit is configured to perform statistical processing on the projected time-series load with reference to the inflection point load of the external load-internal force curve, so as to obtain a reference fatigue index in the direction to be evaluated, wherein the reference fatigue index is used to represent the opening frequency of the flange to be evaluated in the direction to be evaluated; the evaluation unit is configured to determine a direction to be evaluated from the multiple directions to be evaluated as the opening direction of the flange to be evaluated based on the reference fatigue index of each direction to be evaluated in the multiple directions to be evaluated.

[0011] Optionally, the statistical unit is further configured to: perform cycle counting processing on the projected time series load to obtain multiple projected load cycles; for each projected load cycle in the multiple projected load cycles, when at least part of the load in the projected load cycle is greater than or equal to the inflection point load of the external load-internal force curve, determine the projected load cycle as a reference cycle; based on the determined reference cycle, perform statistical processing on the multiple projected load cycles to obtain a reference fatigue index in the direction to be evaluated.

[0012] Optionally, the statistical unit is further configured to: determine the equivalent fatigue of each projected load cycle in the multiple projected load cycles, and record the equivalent fatigue of the reference cycle as reference equivalent fatigue; for the multiple projected load cycles, determine the proportion of the reference equivalent fatigue in all equivalent fatigue as the reference fatigue index of the direction to be evaluated.

[0013] Optionally, the statistical unit is further configured to: determine the load amplitude and number of cycles of the projected load cycle for each of the multiple projected load cycles; and determine the product of the exponential power of the load amplitude and the number of cycles as the equivalent fatigue of the projected load cycle.

[0014] Optionally, the statistical unit is further configured to: determine the load peak and load valley of each projected load cycle in the multiple projected load cycles; and determine the projected load cycle as the reference cycle when at least one of the load peak and the load valley is greater than or equal to the inflection point load of the external load-internal force curve.

[0015] In another general aspect, a flange bolt fatigue assessment device is provided, comprising: a determination unit configured to determine an opening direction of the flange to be assessed based on a time-series load of the flange to be assessed in an original coordinate system; a construction unit configured to construct a spatial coordinate system based on the opening direction and axial direction of the flange to be assessed, recorded as an assessment coordinate system; a conversion unit configured to convert the time-series load from the original coordinate system to the assessment coordinate system to obtain an assessment time-series load; and an assessment unit configured to perform fatigue assessment on the flange bolts of the flange to be assessed based on the assessment time-series load; wherein the opening direction of the flange to be assessed is obtained by a flange opening direction determination method according to an embodiment of the present disclosure.

[0016] In another general aspect, a computer-readable storage medium is provided, which, when instructions in the computer-readable storage medium are executed by at least one processor, causes the at least one processor to execute the flange opening direction determination method or flange bolt fatigue assessment method as described above.

[0017] In another general aspect, a computer device is provided, comprising: at least one processor; and at least one memory storing computer-executable instructions, wherein the computer-executable instructions, when executed by the at least one processor, cause the at least one processor to execute the flange opening direction determination method or flange bolt fatigue assessment method as described above.

[0018] This disclosure provides a method for determining flange opening direction and a method and apparatus for assessing flange bolt fatigue. By combining the inflection point load of the external load-internal force curve, the method assesses the opening frequency of the flange in multiple circumferential directions. The method then determines the opening direction of the flange from these multiple circumferential directions, identifying the direction in which the flange opening is most severe or relatively severe. This allows for targeted assessment during flange bolt fatigue analysis, thereby improving the accuracy of fatigue analysis.

[0019] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a schematic diagram showing a fixed blade root coordinate system in the related art;

[0021] Figure 2 is a schematic diagram showing an external load-internal force curve of a bolt in the related art;

[0022] Figure 3 is a flow chart illustrating a method for determining a flange opening direction or a method for evaluating flange bolt fatigue according to an embodiment of the present disclosure;

[0023] Figure 4 is a flowchart illustrating a method for determining a reference fatigue index according to an embodiment of the present disclosure;

[0024] Figure 5 is a schematic diagram showing the distribution of reference equivalent fatigue of a flange to be evaluated in the circumferential direction according to an embodiment of the present disclosure;

[0025] Figure 6 is a schematic diagram showing the distribution of non-reference equivalent fatigue in the circumferential direction of a flange to be evaluated according to an embodiment of the present disclosure;

[0026] Figure 7 is a schematic diagram showing the distribution of reference fatigue indicators of a flange to be evaluated in the circumferential direction according to an embodiment of the present disclosure;

[0027] Figure 8 is a flow chart illustrating a flange bolt fatigue assessment method according to an embodiment of the present disclosure;

[0028] Figure 9 is a schematic diagram illustrating an original coordinate system and an evaluation coordinate system according to an embodiment of the present disclosure;

[0029] Figure 10 is a block diagram illustrating a device for determining a flange opening direction according to an embodiment of the present disclosure;

[0030] Figure 11is a block diagram illustrating a flange bolt fatigue assessment apparatus according to an embodiment of the present disclosure;

[0031] Figure 12 is a block diagram illustrating a computer device according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0032] The following detailed description is provided to help the reader gain a comprehensive understanding of the methods, devices and / or systems described herein. However, various changes, modifications and equivalents of the methods, devices and / or systems described herein will be clear after understanding the disclosure of the present application. For example, the order of operations described herein is merely an example and is not limited to those orders set forth herein, but can be changed as will be clear after understanding the disclosure of the present application, except for operations that must occur in a specific order. In addition, for greater clarity and conciseness, descriptions of features known in the art may be omitted.

[0033] The features described herein can be implemented in different forms and should not be construed as limited to the examples described herein. Rather, the examples described herein are provided to illustrate only some of the many possible ways to implement the methods, devices, and / or systems described herein, which will become clear after understanding the disclosure of this application.

[0034] As used herein, the term "and / or" includes any one of the associated listed items and any combination of any two or more.

[0035] Although terms such as "first," "second," and "third" may be used herein to describe various members, components, regions, layers, or portions, these members, components, regions, layers, or portions should not be limited by these terms. Instead, these terms are used solely to distinguish one member, component, region, layer, or portion from another member, component, region, layer, or portion. Thus, what is referred to as a first member, first component, first region, first layer, or first portion in the examples described herein may also be referred to as a second member, second component, second region, second layer, or second portion without departing from the teachings of the examples.

[0036] In the specification, when an element (such as a layer, region, or substrate) is described as being “on,” “connected to,” or “coupled to” another element, the element may be directly “on,” “connected to,” or “coupled to” the other element, or one or more other elements may be present therebetween. Conversely, when an element is described as being “directly on,” “directly connected to,” or “directly coupled to” another element, there may be no other elements present therebetween.

[0037] The terms used herein are only used to describe various examples and are not intended to limit the disclosure. Unless the context clearly indicates otherwise, the singular is intended to include the plural. The terms "comprise," "include," and "have" indicate the presence of the recited features, quantities, operations, components, elements, and / or combinations thereof, but do not preclude the presence or addition of one or more other features, quantities, operations, components, elements, and / or combinations thereof.

[0038] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which the present disclosure pertains after understanding the present disclosure. Unless expressly defined otherwise herein, terms (such as those defined in general dictionaries) should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and the present disclosure, and should not be interpreted in an idealized or overly formal manner.

[0039] Furthermore, in describing the examples, when it is deemed that a detailed description of well-known related structures or functions would cause ambiguous interpretation of the present disclosure, such detailed description will be omitted.

[0040] In the wind turbine industry, fatigue analysis of bolts on connecting flanges currently basically uses the finite element method to calculate the force information of the bolts. When using the finite element method for calculation, it is based on a fixed coordinate system. First, the unit load of the load components in each direction under the coordinate system is applied to obtain the force information of the bolts under the unit load. Specifically, when an external force (i.e., load) acts on a mechanical part or structure, the internal part or structure will generate corresponding stress and strain to balance the external load. This internal mechanical response is usually called "internal force", and the force information refers to the information of the internal force.

[0041] Taking the bolts connecting the flange at the blade root as an example, the calculation is usually based on the fixed blade root coordinate system in the GL (Germanischer Lloyd) standard, see Figure 1, where XB is the impeller axis direction, ZB is the blade axis direction, and YB is the direction that forms a right-handed spiral system with XB and ZB. The external loads that have a greater impact on the bolts are Mx (torque in the x direction), My (torque in the y direction), and Fz (tension in the z direction) in the fixed blade root coordinate system. The unit load of each load component is the maximum value of the load component in all fatigue time series load files. For example, the external load Mx takes the maximum value of Mx in all time series as the unit load, and is divided into positive and negative. The negative one takes the maximum absolute value as the unit load. When performing finite element calculations, the unit load is divided into different parts. In this way, the force information of each bolt to be calculated under different values of the load component can be obtained (under the same external load, bolts in different positions may bear different internal forces. The force information generally extracts the internal forces of the bolt section, including the bending moments mx and my of the section and the axial force fz of the section).

[0042] After the above calculations are completed, the force information of each bolt under different values of external loads Mx, My, and Fz is obtained. The data is extracted to obtain the external load-internal force curve of each bolt in each direction, that is, the curve showing the relationship between the external load in each direction in the coordinate system and the internal force of the bolt in that direction. Figure 2 The external load-internal force curve of a bolt in the XB direction is shown as an example.

[0043] A fatigue time series load consists of instantaneous loads at each moment. For example, the loads at time t1 are Mx1, My1, and Fz1, and the loads at time t2 are Mx2, My2, and Fz2. During calculation, the load components at each moment are interpolated based on the corresponding external load-internal force curve to obtain the internal forces in each direction. These forces are then superimposed to obtain the final bolt internal force at that moment. The same calculation method is applied to other moments to obtain the time history of the internal forces for each bolt. Cycle counting (e.g., rainflow counting) can be used to decompose this history into a series of closed cycles, each with its own amplitude (stress range) and average value. Each cycle represents a load reversal, and their contribution to fatigue damage is cumulative. Based on the specific values of each cycle, the equivalent fatigue load of the internal force time history can be calculated. Additionally, the SN curve (stress-life curve) shows the cumulative number of cycles (N) that a material must endure before damage occurs, at different stress (S) levels. For each load cycle, the corresponding maximum number of cycles can be found on the SN curve using its amplitude, and the damage ratio of each cycle (i.e. the ratio of the actual number of cycles to the corresponding maximum number of cycles on the SN curve) is accumulated. If the cumulative damage value is close to or exceeds 1, it means that the bolt may have reached the limit of its fatigue life and there is a risk of fatigue failure. Fatigue analysis can also be achieved.

[0044] In the above process, the final internal force of the bolt at each moment is the direct addition of the internal forces in all directions. This is more accurate for composite loads such as when the connection flange is not opened under Mxy, because when the flange is not obviously opened, the forces on each bolt are uniform, and the external load on a single bolt is small. Figure 2 , at this time, the internal force of the bolt generally changes linearly with the external load. However, when the flange opens under the composite load, the forces on each bolt are no longer uniform. The bolts in the open position will bear a greater external load because they have to resist the greater separation force, resulting in a nonlinear relationship between the internal force and the external load. Therefore, such calculations will ignore the effects of the nonlinear relationship between the internal force and the external load, resulting in the final result not including nonlinear information, thereby underestimating the alternating amplitude of the bolt internal force, especially the alternating amplitude of the internal force of the bolt in the open position, which in turn affects the accuracy of the fatigue analysis. Therefore, if the analysis can be carried out in the direction where the flange opening is most severe or relatively severe, it will help improve the accuracy of the fatigue analysis.

[0045] However, when performing unit load finite element calculations to determine the external load-internal force curve for the bolts, the unit load calculations were based on the fixed blade root coordinate system. However, the coordinate axis orientation of this fixed blade root coordinate system is generally not in the direction where flange opening is most severe or relatively severe. Therefore, maximum or significant flange opening is generally not captured. However, flange opening is very common in finite element calculations, creating a contradiction: flange opening is permitted, but the calculation method cannot capture maximum or significant opening.

[0046] In addition, when the equivalent fatigue load is calculated based on the time-varying history of the internal force in the later stage, the final result is the equivalent fatigue load in the coordinate axis direction in the fixed blade root coordinate system. On the one hand, the equivalent fatigue load is only the linear accumulation of the amplitude after the cycle count, and does not take into account the nonlinear situation. Therefore, it does not contain nonlinear information and cannot understand the flange opening condition. On the other hand, since there are only equivalent fatigue loads in two coordinate axis directions (i.e., XB direction and YB direction) in the flange cross section, it is impossible to judge the flange opening condition in the 360° direction. Therefore, it is impossible to determine the direction that is most seriously or more seriously affected by the flange opening, and it is impossible to conduct targeted analysis in this direction. In other words, the existing equivalent fatigue load cannot characterize the flange opening condition.

[0047] An embodiment of the first aspect of the present disclosure provides a method for determining a flange opening direction. Figure 3 is a flowchart illustrating a method for determining a flange opening direction according to an embodiment of the present disclosure.

[0048] Reference Figure 3 In step S301, the time series load of the flange to be evaluated in the original coordinate system and the inflection point load of the external load-internal force curve of the flange to be evaluated are obtained.

[0049] It should be understood that the original coordinate system is a coordinate system originally used to describe time-series loads, such as the aforementioned fixed blade root coordinate system.

[0050] The external load-internal force curve is used to represent the relationship between the external load of the flange to be evaluated and the internal force of the flange bolts to be evaluated. The previous article introduced the time series load and the external load-internal force curve, which will not be repeated here. The external load-internal force curve is shown as follows: Figure 2 As shown in Figure 2, the inflection point load is the external load at the inflection point of the curve. Figure 2 When the external load Mx is less than 14,000,000, the external load and internal force are essentially linearly related. When the external load exceeds 14,000,000, the internal force changes dramatically, and the linear relationship between the external load and internal force ceases. 14,000,000 is the inflection point load. It should be noted that, while the external load-internal force curve is calculated for each coordinate axis during fatigue analysis, due to the rotational symmetry of the flange structure, the inflection point load of the external load-internal force curve is essentially the same in any circumferential direction. Therefore, to obtain the inflection point load, simply select any direction. As an example, after calculating the external load-internal force curve, the inflection point can be directly determined from the curve to obtain the inflection point load. Furthermore, during the simulation of the flange to be evaluated to determine the bolt force information, the simulation diagram of the flange to be evaluated can be observed. Therefore, the opening diagram of the flange to be evaluated under different external loads can also be observed to find the diagram where the flange opening just reaches the bolt, and the external load at this time is used as the inflection point load. This is because when the flange is opened to a lower degree, the opening has not yet reached the bolt, so that the two flange surfaces connected by the bolt are still in a state of contact near the bolt. At this time, the external load borne by the bolt still changes linearly. When the opening just reaches the bolt, the two local surfaces connected by the bolt are about to move away from each other. Once the two local surfaces move away from each other, the bolt is at the flange opening. As mentioned above, the bolt at the flange opening will bear a greater external load, resulting in a nonlinear change in the relationship between the internal force and the external load. Therefore, the moment the opening just reaches the bolt is the inflection point where the relationship between the internal force and the external load is about to change from a linear relationship to a nonlinear relationship. The external load at this time can also be regarded as the inflection point load. Of course, other reasonable methods can also be used to obtain the inflection point load, and this disclosure does not limit this.

[0051] In step S302 , a plurality of directions to be evaluated are determined along the circumference of the flange to be evaluated.

[0052] Since the opening of the flange occurs at a certain angle in its circumferential direction, by determining multiple directions to be evaluated along the circumference of the flange to be evaluated, it is possible to evaluate the opening of the flange to be evaluated in each direction to be evaluated, and then understand the direction in which the opening is most serious or relatively serious. It should be understood that the reason why it is described here as the direction in which the opening is most serious or relatively serious is that it is often impossible to accurately cover every direction in the circumference when determining the direction to be evaluated. Therefore, in theory, only the relative severity of the opening of the flange to be evaluated in these multiple directions to be evaluated can be determined, and the direction finally determined may or may not be the direction in which the opening is most serious. As an example, when determining multiple modes to be evaluated, an angular interval can be set, such as 10°, 20°, 30°, etc., and a starting position can be first determined as the first direction to be evaluated, and then a direction to be evaluated can be determined at every angular interval along the circumference of the flange to be evaluated, thereby achieving the determination of multiple directions to be evaluated. The first direction to be evaluated can be the direction of a coordinate axis in the original coordinate system, or it can be a randomly determined direction, and the present disclosure does not limit this.

[0053] As an example, when it is unclear which azimuth region or regions of the flange to be evaluated are more likely to experience flange opening, the angular interval can be a fixed value, and the angular interval value can be set to a value that is divisible by 360 (when using the angular system) or 2π (when using the radian system) so that the multiple directions to be evaluated are evenly distributed along the circumference. When it is clear which azimuth region or regions of the flange to be evaluated are more likely to experience flange opening, a relatively small angular interval can be used in this azimuth region or regions, and a relatively large angular interval can be used in other azimuth regions to increase the density of directions to be evaluated in this azimuth region or regions, thereby more accurately finding the direction with the most severe or relatively severe flange opening with the same evaluation calculation amount (that is, when the number of directions to be evaluated is the same).

[0054] In step S303 , for each of the multiple directions to be evaluated, a projection of the time series load on the direction to be evaluated is determined as the projected time series load of the direction to be evaluated.

[0055] Specifically, for the current direction to be evaluated, the load at each moment in the time series load can be projected separately. For any moment, according to the angle between the direction of each coordinate axis in the original coordinate system and the direction to be evaluated, the sum of the projections of the loads on each coordinate axis in the original coordinate system in the direction to be evaluated is calculated using trigonometric functions to obtain the projected load in the direction to be evaluated. The projected loads at each moment are then combined to obtain the projected time series load in the direction to be evaluated.

[0056] In step S304, the inflection point load of the external load-internal force curve is used as a reference, and statistical processing is performed on the projected time series load to obtain a reference fatigue index in the direction to be evaluated.

[0057] Since the inflection point load reflects the transition node of the changing relationship between the external load and the internal force, the inflection point load is used as a reference for the statistical projection of the time series load. The reference fatigue index obtained can include the nonlinear information of the flange to be evaluated, and is thus used to represent the opening frequency of the flange to be evaluated in the direction to be evaluated, that is, the proportion of the period when the flange to be evaluated is open in its entire working period.

[0058] In step S305 , one direction to be evaluated is determined from the multiple directions to be evaluated according to the reference fatigue index of each direction to be evaluated as the opening direction of the flange to be evaluated.

[0059] As an example, the direction to be evaluated with the largest reference fatigue index value among the multiple directions to be evaluated, that is, the direction to be evaluated with the highest opening frequency, may be used as the opening direction.

[0060] Due to the large number of time series loads, each with approximately 30,000 time points and typically hundreds of time series files, there is currently no suitable method to characterize the frequency of flange opening in various positions, and the accuracy of traditional methods is even more difficult to measure.

[0061] In this regard, the flange opening direction determination method according to the embodiments of the present disclosure combines the inflection point load of the external load-internal force curve to evaluate the flange opening frequency in multiple circumferential directions. This method then determines the flange opening direction from these multiple circumferential directions, thereby identifying the direction in which the flange opening is most severe or relatively severe. This allows for targeted assessment during flange bolt fatigue analysis, thereby improving the accuracy of fatigue analysis.

[0062] Next, step S304 will be further introduced.

[0063] Figure 4 is a flowchart illustrating a method of determining a reference fatigue index according to an embodiment of the present disclosure.

[0064] Reference Figure 4 In step S3041, a cycle counting process is performed on the projected time series load to obtain a plurality of projected load cycles.

[0065] In fatigue analysis, cycle counting uses methods such as the Rainflow Counting method to identify load cycles in a time-series load and calculate the size (typically expressed as the mean and amplitude of the load cycles) and number (often referred to as the number of cycles) of these cycles to assess fatigue damage and predict fatigue life under repeated loading. Cycle counting of projected time-series loads can be used to convert them into multiple projected load cycles, facilitating subsequent analysis of these multiple projected load cycles based on inflection point loads.

[0066] In step S3042, for each of the multiple projected load cycles, if at least part of the load in the projected load cycle is greater than or equal to the inflection point load of the external load-internal force curve, the projected load cycle is determined as a reference cycle.

[0067] As mentioned above, when the external load exceeds the inflection point load, the linear relationship between the external load and the internal force no longer exists. By recording the projected load cycle in which at least part of the load exceeds the inflection point load as a reference cycle, multiple projected load cycles can be classified based on whether they belong to the reference cycle.

[0068] Furthermore, since the reference cycle contains loads exceeding the inflection point load, the reference load can also be named an out-of-bounds amplitude cycle. Furthermore, since the external load and internal force no longer have a linear relationship after exceeding the inflection point load, the reference load can also be named a nonlinear amplitude cycle, and the non-reference cycle can be named a linear amplitude cycle. These are merely examples of cycle naming and have no impact on the essence of the solution.

[0069] Optionally, step S3042 includes: determining, for each of the multiple projected load cycles, a load peak value and a load valley value in the projected load cycle; and determining the projected load cycle as a reference cycle when at least one of the load peak value and the load valley value is greater than or equal to the inflection point load of the external load-internal force curve. When determining whether at least part of the load in the projected load cycle is greater than or equal to the inflection point load, by converting the determination to determining whether at least one of the load peak value and the load valley value in the projected load cycle is greater than or equal to the inflection point load, only the load values at two points in the projected load cycle need to be determined while achieving the same determination result, thereby significantly reducing the amount of calculation, helping to conserve computing resources, and improving computing efficiency.

[0070] It should be understood that the load peak is the maximum value of the corresponding projected load cycle, and the load valley is the minimum value of the corresponding projected load cycle, with the load peak being greater than the load valley. When both the load peak and the load valley are less than the inflection point load, the entire projected load cycle is less than the inflection point load and is not a reference load; when both the load peak and the load valley are greater than or equal to the inflection point load, the entire projected load cycle is greater than or equal to the inflection point load and is a reference load; when the load peak is equal to the inflection point load and the load valley is less than the inflection point load, there is a load value in the projected load cycle that is equal to the inflection point load, namely the load peak, and the projected load cycle is a reference cycle; when the load peak is greater than the inflection point load and the load valley is less than the inflection point load, the inflection point load falls between the load peak and the load valley, and there is a load value in the projected load cycle that is greater than or equal to the inflection point load and less than the load peak, and the projected load cycle is a reference cycle.

[0071] As an example, when executing this step, the load peak values and load valley values of all projected load cycles may be determined first, and then, combined with all the determined load peak values and load valley values, whether each projected load cycle is a reference cycle may be determined. Alternatively, for each projected load cycle, after the load peak value and load valley value are determined, whether the cycle is a reference cycle may be directly determined, and all projected load cycles may be traversed in this manner. This disclosure is not limited to this.

[0072] In step S3043, based on the determined reference cycle, a plurality of projected load cycles are statistically processed to obtain a reference fatigue index of the direction to be evaluated.

[0073] Optionally, step S3043 includes: determining the equivalent fatigue of each of the multiple projected load cycles, and recording the equivalent fatigue of the reference cycle as the reference equivalent fatigue; and determining the proportion of the reference equivalent fatigue in all equivalent fatigue for the multiple projected load cycles as the reference fatigue index for the direction to be evaluated. Equivalent fatigue can quantitatively represent the projected load cycle from the perspective of fatigue analysis. Compared with simply counting the proportion of the reference cycle in all projected load cycles from the perspective of the number of cycles, by calculating the equivalent fatigue of each projected load cycle, it is possible to determine whether the corresponding equivalent fatigue is the reference equivalent fatigue based on whether each projected load cycle is a reference cycle, and then calculate the proportion of the reference equivalent fatigue value in all equivalent fatigue values. This can more accurately reflect the influence of the reference cycle from the perspective of fatigue analysis, and thus make the reference fatigue index obtained thereby more reliably represent the opening frequency of the flange to be evaluated in each direction to be evaluated. At the same time, compared to traditional equivalent fatigue calculation methods that are based solely on the linear accumulation of amplitudes obtained by cycle counting, the present disclosure combines inflection point loads to perform differentiated statistics on the equivalent fatigue of different projected load cycles, taking into account the nonlinear information of flange opening. This helps to understand and evaluate the opening and closing frequencies of the flange in various directions (the closing frequency is the proportion of the period when the flange to be evaluated is closed during its entire working period, and the sum of the opening and closing frequencies is 1). In addition, compared to traditional methods that can only calculate equivalent fatigue along the coordinate axis, the present disclosure can calculate equivalent fatigue in multiple directions to be evaluated in a 360° circumferential direction, achieving a multi-faceted evaluation.

[0074] Optionally, determining the equivalent fatigue of each of the multiple projected load cycles in step S3043 includes: determining, for each of the multiple projected load cycles, a load amplitude and a number of cycles; and determining the product of an exponential power of the load amplitude and the number of cycles as the equivalent fatigue of the projected load cycle. By clearly defining a calculation method for the equivalent fatigue of the projected load cycle, reliable calculation of the equivalent fatigue can be achieved.

[0075] Specifically, if the load amplitude of the i-th reference cycle is recorded as S i , the load amplitude of the jth non-reference cycle is recorded as S j , then according to the conventional equivalent fatigue load calculation method, the reference equivalent fatigue can be expressed as The non-reference equivalent fatigue can be expressed as Where m is the fatigue equivalent index. For bolts, m=4 is generally used as the exponential value of the load amplitude. n1 is the number of reference cycles, n2 is the number of non-reference cycles; n i is the number of cycles of the i-th reference cycle, n j is the number of cycles of the jth non-reference cycle.

[0076] Since only the load amplitude and the number of cycles affect the equivalent fatigue in the projected load cycle, and the load mean has no effect on the equivalent fatigue, the projected load cycles with the same load amplitude and different load means can be merged during the calculation. In this case, n1 is the number of load amplitudes of the merged reference cycle, and n2 is the number of load amplitudes of the merged non-reference cycle; S i is the load amplitude of the ith reference cycle after merging, n i is the load amplitude S i The number of repetitions in the reference cycle is equal to the load amplitude S i The sum of the number of cycles of each reference cycle; S j is the jth load amplitude of the non-reference cycle after merging, n j is the load amplitude S j The number of repetitions in the non-reference cycle is equal to the load amplitude S j The calculation results of these two representations are consistent.

[0077] In addition, when calculating the reference fatigue index, we only care about the relative size relationship between the reference fatigue indices of each direction to be evaluated, and do not strictly care about the specific value of the reference fatigue index. By expressing the reference equivalent fatigue as And the non-reference equivalent fatigue is expressed as Then obtain the reference fatigue index This can reduce the amount of calculations that are divided by the same value (i.e. 10 7 ) and the amount of calculation generated by calculating the mth power, thereby reducing the overall amount of calculation, saving computing resources and improving computing efficiency.

[0078] It should be understood that when calculating the reference fatigue index, the aforementioned conventional equivalent fatigue load calculation method can also be used to calculate the reference equivalent fatigue and non-reference equivalent fatigue, and reasonable adjustments can be made thereon, such as adding a coefficient to adjust the specific value of the numerical value, etc. These are all implementation methods of the present disclosure and fall within the scope of protection of the present disclosure.

[0079] like Figures 5 to 7 The following diagram illustrates the distribution of reference equivalent fatigue, non-reference equivalent fatigue, and reference fatigue indices in the circumferential direction for a flange to be evaluated. It should be understood that in directions to be evaluated where no reference cycles exist, the reference equivalent fatigue value is 0, and the reference fatigue index value is also 0, indicating that the flange to be evaluated is not open in these directions. In directions where the reference equivalent fatigue and reference fatigue index values are greater than 0, the flange to be evaluated is considered open. The larger the value, the higher the frequency of flange opening and the more severe the opening. This allows identification of the directions in which the flange to be evaluated is most or relatively open.

[0080] In general, according to the embodiments of the present disclosure, Figure 4 The method for determining the reference fatigue index shown in the figure converts the projected time series load into multiple projected load cycles for each direction to be evaluated, and then classifies each projected load cycle with reference to the inflection point load of the external load-internal force curve. Based on the classification, the multiple projected load cycles are statistically processed in a differentiated manner. This can improve the operability of the statistical processing and ensure that the statistical results (i.e., the reference fatigue index of the current direction to be evaluated) can quantitatively reflect the nonlinear information in each direction to be evaluated, thereby more reliably representing the opening frequency of the flange to be evaluated in each direction to be evaluated.

[0081] An embodiment of a second aspect of the present disclosure provides a flange bolt fatigue assessment method. Figure 8 is a flowchart illustrating a flange bolt fatigue assessment method according to an embodiment of the present disclosure.

[0082] Reference Figure 8 In step S801, the opening direction of the flange to be evaluated is determined according to the time series load of the flange to be evaluated in the original coordinate system.

[0083] The opening direction of the flange to be evaluated is obtained by the method for determining the flange opening direction according to any embodiment of the first aspect of the present disclosure. Therefore, the flange bolt fatigue assessment method according to the embodiment of the second aspect of the present disclosure has all the beneficial technical effects of the method for determining the flange opening direction, which will not be repeated here.

[0084] In step S802 , a spatial coordinate system is constructed based on the opening direction and axial direction of the flange to be evaluated, and is recorded as the evaluation coordinate system.

[0085] As an example, when constructing an evaluation coordinate system based on the opening direction and axial direction of the flange to be evaluated, the same as the original coordinate system, the axial direction of the flange to be evaluated (for the connecting flange at the root of the wind turbine blade, that is, the blade axial direction) is taken as the Z direction, the opening direction of the flange to be evaluated or its opposite direction is taken as the X direction, and the direction forming a right-handed spiral system with the X direction and the Z direction is taken as the Y direction, that is, only the opening direction of the flange to be evaluated is adjusted as follows Figure 1 The XB direction and YB direction of the original coordinate system are shown.

[0086] Still Figures 5 to 7 For example, refer to Figure 9 The XB axis and the YB axis are the two coordinate axes of the original coordinate system in the flange cross section. The dotted line direction is the opening direction of the flange to be evaluated determined in step S801. The opposite direction of the dotted line direction is the X direction, and the Y direction is determined accordingly to obtain the evaluation coordinate system. This is equivalent to rotating the original coordinate system by an angle of θ in a clockwise direction to obtain the evaluation coordinate system.

[0087] In step S803 , the time series load is converted from the original coordinate system to the evaluation coordinate system to obtain the evaluation time series load.

[0088] The conversion between coordinate systems can be achieved through projection. Figure 9 , denote the time-series load components in the XB and YB directions in the original coordinate system as Mx and My, respectively, and denote the time-series load components in the X and Y directions in the evaluation coordinate system, namely the evaluation time-series load components, as Mx' and My', respectively. Then, we can obtain Mx'=Mx*cosθ-My*sinθ, and My'=Mx*sinθ+My*cosθ. The time-series load component Fz' in the Z direction in the evaluation coordinate system is the same as the time-series load component Fz in the ZB direction in the original coordinate system.

[0089] In step S804 , fatigue assessment is performed on the flange bolts of the flange to be assessed according to the assessment time series load.

[0090] This step can be implemented using existing fatigue assessment methods, which can be referred to in the previous description and will not be repeated here. It should be understood that among the flange bolts of the flange to be assessed, the flange bolts in the expansion direction are the bolts that are relatively severely affected by the flange expansion.

[0091] As an example, since the time series load used is replaced by the evaluation time series load, in order to maintain the consistency of the coordinate system, the external load-internal force curve used can also adopt the external load-internal force curve of each coordinate axis direction in the evaluation coordinate system. That is, when using the finite element method to calculate the external load-internal force curve, the unit load can be applied in the evaluation coordinate system, so that the finite element calculation is directly positioned at the position where the flange to be evaluated is most severely opened or relatively severely opened, which helps to better capture the larger opening of the flange to be evaluated in the load sequence, thereby further improving the fatigue calculation accuracy of the flange bolts. However, the existing finite element model is established based on the original coordinate system. Therefore, in order to directly use the existing finite element model, the unit load component in a certain coordinate axis direction in the evaluation coordinate system can be decomposed into different coordinate axis directions in the original coordinate system. Then, by performing finite element calculation on the decomposed load, the calculation results of the different coordinate axis directions in the original coordinate system are merged into the corresponding coordinate axis directions in the evaluation coordinate system, and the external load-internal force curve of the corresponding coordinate axis direction in the evaluation coordinate system can be obtained.

[0092] Still Figure 9 For example, the unit load component Mx' in the X direction is decomposed into the XB direction and the YB direction, and the resulting load components are Mx'*cosθ and -Mx'*sinθ respectively. The unit load component My' in the Y direction is decomposed into the XB direction and the YB direction, and the resulting load components are My'*sinθ and My'*cosθ respectively.

[0093] After that, based on the external load-internal force curve in the evaluation coordinate system and the evaluation time series load, the flange bolts of the flange to be evaluated can be fatigue evaluated and the fatigue damage of the flange bolts can be calculated.

[0094] An embodiment of the third aspect of the present disclosure provides a device for determining a flange opening direction. Figure 10 2 is a block diagram illustrating a device for determining a flange opening direction according to an embodiment of the present disclosure.

[0095] Reference Figure 10 The device 1000 for determining the flange opening direction includes an acquisition unit 1001 , a determination unit 1002 , a projection unit 1003 , a statistics unit 1004 , and an evaluation unit 1005 .

[0096] The acquisition unit 1001 can acquire the time-series load of the flange to be evaluated in the original coordinate system and the inflection point load of the external load-internal force curve of the flange to be evaluated, wherein the external load-internal force curve is used to represent the relationship between the external load of the flange to be evaluated and the internal force of the flange bolts of the flange to be evaluated.

[0097] The determining unit 1002 may determine a plurality of directions to be evaluated along the circumference of the flange to be evaluated.

[0098] The projection unit 1003 may determine, for each of the multiple directions to be evaluated, a projection of the time series load in the direction to be evaluated as the projected time series load of the direction to be evaluated.

[0099] The statistical unit 1004 can perform statistical processing on the projected time series load with reference to the inflection point load of the external load-internal force curve to obtain a reference fatigue index in the direction to be evaluated, wherein the reference fatigue index is used to represent the opening frequency of the flange to be evaluated in the direction to be evaluated.

[0100] The evaluation unit 1005 may determine one direction to be evaluated from the multiple directions to be evaluated as the opening direction of the flange to be evaluated according to the reference fatigue index of each direction to be evaluated.

[0101] Optionally, the statistical unit 1004 can also: perform cycle counting processing on the projected time series load to obtain multiple projected load cycles; for each projected load cycle in the multiple projected load cycles, when at least part of the load in the projected load cycle is greater than or equal to the inflection point load of the external load-internal force curve, determine the projected load cycle as a reference cycle; based on the determined reference cycle, perform statistical processing on the multiple projected load cycles to obtain a reference fatigue index in the direction to be evaluated.

[0102] Optionally, the statistical unit 1004 can also: determine the equivalent fatigue of the projected load cycle for each of the multiple projected load cycles, and record the equivalent fatigue of the reference cycle as the reference equivalent fatigue; for the multiple projected load cycles, determine the proportion of the reference equivalent fatigue in all equivalent fatigue as the reference fatigue index for the direction to be evaluated.

[0103] Optionally, the statistics unit 1004 may further: determine the load amplitude and the number of cycles of each projected load cycle in the multiple projected load cycles; and determine the product of the exponential power of the load amplitude and the number of cycles as the equivalent fatigue of the projected load cycle.

[0104] Optionally, the statistical unit 1004 may also: determine the load peak and load valley values in the projected load cycle for each of the multiple projected load cycles; and determine the projected load cycle as a reference cycle when at least one of the load peak and the load valley values is greater than or equal to the inflection point load of the external load-internal force curve.

[0105] An embodiment of a fourth aspect of the present disclosure provides a flange bolt fatigue assessment device. Figure 11 is a block diagram illustrating a flange bolt fatigue evaluation apparatus according to an embodiment of the present disclosure.

[0106] Reference Figure 11 The flange bolt fatigue assessment device 1100 includes a determination unit 1101 , a construction unit 1102 , a conversion unit 1103 , and an assessment unit 1104 .

[0107] The determining unit 1101 may determine the opening direction of the flange to be evaluated according to the time-series load of the flange to be evaluated in the original coordinate system.

[0108] The constructing unit 1102 may construct a spatial coordinate system based on the opening direction and the axial direction of the flange to be evaluated, which is recorded as the evaluation coordinate system.

[0109] The conversion unit 1103 may convert the time series load from the original coordinate system to the evaluation coordinate system to obtain the evaluation time series load.

[0110] The evaluation unit 1104 may perform fatigue evaluation on the flange bolts of the flange to be evaluated according to the evaluation time sequence load.

[0111] The opening direction of the flange to be evaluated is obtained by the flange opening direction determination method according to an embodiment of the present disclosure.

[0112] Regarding the apparatus in the above embodiment, the specific manner in which each unit performs operations has been described in detail in the embodiment of the method, and will not be elaborated on here.

[0113] The method for determining the flange opening direction or the method for evaluating the fatigue of flange bolts according to the embodiments of the present disclosure can be written as a computer program and stored on a computer-readable storage medium. When the instructions corresponding to the computer program are executed by a processor, the method for determining the flange opening direction or the method for evaluating the fatigue of flange bolts as described above can be implemented. Examples of computer-readable storage media include: read-only memory (ROM), random access programmable read-only memory (PROM), electrically erasable programmable read-only memory (EEPROM), random access memory (RAM), dynamic random access memory (DRAM), static random access memory (SRAM), flash memory, non-volatile memory, CD-ROM, CD-R, CD+R, CD-RW, CD+RW, DVD-ROM, DVD-R, DVD+R, DVD-RW, DVD+RW, DVD-RAM, BD-ROM, BD-R, BD-R LTH, BD-RE, Blu-ray or optical disk storage, hard disk drive (HDD), solid state drive (SSD), card storage (such as, multimedia card, secure digital (SD) card or ultra fast digital (XD) card), magnetic tape, floppy disk, magneto-optical data storage device, optical data storage device, hard disk, solid state disk and any other device, any other device configured to store the computer program and any associated data, data files and data structures in a non-transitory manner and provide the computer program and any associated data, data files and data structures to a processor or computer so that the processor or computer can execute the computer program. In one example, the computer program and any associated data, data files and data structures are distributed on a networked computer system so that the computer program and any associated data, data files and data structures are stored, accessed and executed in a distributed manner by one or more processors or computers.

[0114] Figure 12 is a block diagram illustrating a computer device according to an embodiment of the present disclosure.

[0115] Reference Figure 12 The computer device 1200 includes at least one memory 1201 and at least one processor 1202. The at least one memory 1201 stores a set of computer-executable instructions. When the computer-executable instruction set is executed by the at least one processor 1202, the method for determining the flange opening direction or the flange bolt fatigue assessment method according to the exemplary embodiment of the present disclosure is executed.

[0116] As an example, the computer device 1200 may be a PC, a tablet device, a personal digital assistant, a smart phone, or other device capable of executing the above-mentioned instruction set. Here, the computer device 1200 is not necessarily a single electronic device, but may also be any collection of devices or circuits capable of executing the above-mentioned instructions (or instruction sets) individually or in combination. The computer device 1200 may also be part of an integrated control system or system manager, or may be configured as a portable electronic device that is interconnected with a local or remote (e.g., via wireless transmission) interface.

[0117] In computer device 1200, processor 1202 may include a central processing unit (CPU), a graphics processing unit (GPU), a programmable logic device, a dedicated processor system, a microcontroller, or a microprocessor. By way of example and not limitation, the processor may also include an analog processor, a digital processor, a microprocessor, a multi-core processor, a processor array, a network processor, etc.

[0118] The processor 1202 can execute instructions or codes stored in the memory 1201, wherein the memory 1201 can also store data. Instructions and data can also be sent and received over a network via a network interface device, wherein the network interface device can use any known transmission protocol.

[0119] The memory 1201 may be integrated with the processor 1202, for example, by placing RAM or flash memory within an integrated circuit microprocessor or the like. Furthermore, the memory 1201 may comprise a separate device, such as an external disk drive, a storage array, or any other storage device usable by a database system. The memory 1201 and the processor 1202 may be operatively coupled or may communicate with each other, for example, via an I / O port, a network connection, or the like, such that the processor 1202 can access files stored in the memory.

[0120] In addition, the computer device 1200 may also include a video display (such as a liquid crystal display) and a user interaction interface (such as a keyboard, a mouse, a touch input device, etc.) All components of the computer device 1200 may be connected to each other via a bus and / or a network.

[0121] This disclosure provides a method for determining flange opening direction and a method and apparatus for assessing flange bolt fatigue. By combining the inflection point load of the external load-internal force curve, the method assesses the opening frequency of the flange in multiple circumferential directions. The method then determines the opening direction of the flange from these multiple circumferential directions, identifying the direction in which the flange opening is most severe or relatively severe. This allows for targeted assessment during flange bolt fatigue analysis, thereby improving the accuracy of fatigue analysis.

[0122] The specific implementation methods of the present disclosure have been described in detail above. Although some embodiments have been shown and described, those skilled in the art should understand that these embodiments may be modified and varied without departing from the principles and spirit of the present disclosure, the scope of which is defined by the claims and their equivalents. These modifications and variations should also be within the scope of protection of the claims of the present disclosure.

Claims

1. A method for determining the flange opening direction, characterized in that: The determination method includes: Obtaining a time-series load of the flange to be evaluated in the original coordinate system and an inflection point load of an external load-internal force curve of the flange to be evaluated, wherein the external load-internal force curve is used to represent the relationship between the external load of the flange to be evaluated and the internal force of the flange bolts of the flange to be evaluated; Determining a plurality of directions to be evaluated along the circumference of the flange to be evaluated; For each direction to be evaluated among the multiple directions to be evaluated, determining a projection of the time series load on the direction to be evaluated as the projected time series load of the direction to be evaluated; Taking the inflection point load of the external load-internal force curve as a reference, statistically processing the projected time series load to obtain a reference fatigue index in the direction to be evaluated, wherein the reference fatigue index is used to represent the opening frequency of the flange to be evaluated in the direction to be evaluated; According to the reference fatigue index of each direction to be evaluated in the multiple directions to be evaluated, one direction to be evaluated is determined from the multiple directions to be evaluated as the opening direction of the flange to be evaluated.

2. The determination method according to claim 1, wherein: The method of performing statistical processing on the projected time series load with the inflection point load of the external load-internal force curve as a reference to obtain a reference fatigue index of the direction to be evaluated includes: Performing cycle counting processing on the projected time series load to obtain a plurality of projected load cycles; for each projected load cycle of the plurality of projected load cycles, if at least a portion of the load in the projected load cycle is greater than or equal to an inflection point load of the external load-internal force curve, determining the projected load cycle as a reference cycle; Based on the determined reference cycle, the multiple projected load cycles are statistically processed to obtain a reference fatigue index in the direction to be evaluated.

3. The determination method according to claim 2, wherein: The step of performing statistical processing on the plurality of projected load cycles based on the determined reference cycle to obtain a reference fatigue index in the direction to be evaluated includes: For each of the plurality of projected load cycles, determining an equivalent fatigue of the projected load cycle, and recording the equivalent fatigue of the reference cycle as a reference equivalent fatigue; For the multiple projected load cycles, a proportion of the reference equivalent fatigue in all equivalent fatigue is determined as a reference fatigue index for the direction to be evaluated.

4. The determination method according to claim 3, wherein: The determining, for each of the plurality of projected load cycles, an equivalent fatigue of the projected load cycle, comprises: For each projected load cycle in the plurality of projected load cycles, determining a load amplitude and a cycle number of the projected load cycle; The product of the exponential power of the load amplitude and the number of cycles is determined as the equivalent fatigue of the projected load cycle.

5. The determination method according to claim 2, wherein: The step of determining, for each of the plurality of projected load cycles, the projected load cycle as a reference cycle when at least part of the load in the projected load cycle is greater than or equal to the inflection point load of the external load-internal force curve comprises: For each projected load cycle in the plurality of projected load cycles, determining a peak load value and a valley load value in the projected load cycle; In a case where at least one of the load peak value and the load valley value is greater than or equal to the inflection point load of the external load-internal force curve, the projected load cycle is determined as the reference cycle.

6. A flange bolt fatigue assessment method, characterized in that: The flange bolt fatigue assessment method comprises: Determining the opening direction of the flange to be evaluated according to the time-series load of the flange to be evaluated in the original coordinate system; Based on the opening direction and axial direction of the flange to be evaluated, a spatial coordinate system is constructed, which is recorded as the evaluation coordinate system; Converting the time series load from the original coordinate system to the evaluation coordinate system to obtain an evaluation time series load; Performing fatigue assessment on the flange bolts of the flange to be assessed according to the assessment time series load; The opening direction of the flange to be evaluated is obtained by the method for determining the flange opening direction according to any one of claims 1 to 5.

7. A device for determining the flange opening direction, characterized in that: The determining device comprises: an acquisition unit configured to acquire a time-series load of the flange to be evaluated in an original coordinate system and an inflection point load of an external load-internal force curve of the flange to be evaluated, wherein the external load-internal force curve is used to represent a relationship between an external load of the flange to be evaluated and an internal force of a flange bolt of the flange to be evaluated; a determining unit configured to determine a plurality of directions to be evaluated along the circumference of the flange to be evaluated; a projection unit configured to determine, for each of the multiple directions to be evaluated, a projection of the time series load in the direction to be evaluated as the projected time series load of the direction to be evaluated; a statistical unit configured to perform statistical processing on the projected time series load with reference to the inflection point load of the external load-internal force curve, so as to obtain a reference fatigue index in the direction to be evaluated, wherein the reference fatigue index is used to represent the opening frequency of the flange to be evaluated in the direction to be evaluated; The evaluation unit is configured to determine one direction to be evaluated from the multiple directions to be evaluated as the opening direction of the flange to be evaluated according to a reference fatigue index of each direction to be evaluated.

8. A flange bolt fatigue assessment device, characterized in that: The flange bolt fatigue assessment device comprises: a determining unit configured to determine an opening direction of the flange to be evaluated according to a time-series load of the flange to be evaluated in an original coordinate system; A construction unit is configured to construct a spatial coordinate system based on the opening direction and axial direction of the flange to be evaluated, which is recorded as an evaluation coordinate system; a conversion unit configured to convert the time series load from the original coordinate system to the evaluation coordinate system to obtain an evaluation time series load; an evaluation unit configured to perform fatigue evaluation on the flange bolts of the flange to be evaluated according to the evaluation time sequence load; The opening direction of the flange to be evaluated is obtained by the method for determining the flange opening direction according to any one of claims 1 to 5.

9. A computer-readable storage medium, characterized in that When the instructions in the computer-readable storage medium are executed by at least one processor, the at least one processor is prompted to execute the flange opening direction determination method according to any one of claims 1 to 5 or the flange bolt fatigue assessment method according to claim 6.

10. A computer device, characterized in that: include: at least one processor; at least one memory storing computer-executable instructions, When the computer executable instructions are executed by the at least one processor, the computer executable instructions prompt the at least one processor to execute the flange opening direction determination method according to any one of claims 1 to 5 or the flange bolt fatigue assessment method according to claim 6.

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