A method for calculating cooperative propagation of multiple cracks of a rotor support of a hydroelectric generating unit

Abstract

This invention provides a method for calculating the coordinated propagation of multiple cracks in a hydropower generator rotor support, comprising: S100, establishing a geometric model of the hydropower generator rotor support and determining initial defects and material property parameters; S200, generating a load spectrum based on actual operating records of the hydropower generator and applying boundary conditions; S300, dividing the load spectrum into several load cycle steps; S400, in each load cycle step, calculating the stress intensity factor at the tip of each crack under the current crack state; S500, calculating the propagation rate and direction of each crack tip, updating the geometry, length, and depth of all cracks; and aggregating cracks that meet preset conditions into new cracks; S600, repeating S400 to S500 until any crack size reaches a preset failure criterion, and using the cumulative number of load cycle steps as the predicted fatigue life. This invention significantly improves the accuracy and reliability of fatigue life prediction.

Description

Technical Field

[0001] This invention relates to the fields of structural integrity assessment, fracture mechanics and fatigue life prediction, and in particular to a calculation method for the coordinated propagation of multiple cracks in a hydropower unit rotor support with initial defects under complex loads. Background Technology

[0002] The rotor support of a hydroelectric generator unit is a key load-bearing component of a large hydroelectric generator unit. Its complex structure and enormous size subject it to complex alternating loads during unit operation, including periodic start-ups and shutdowns, load variations, and unbalanced forces. Due to factors such as material manufacturing, processing techniques, and long-term operating environment, the rotor support inevitably develops initial defects (such as microcracks, inclusions, and weld defects). Under long-term alternating loads, these initial defects can initiate and propagate into macroscopic cracks.

[0003] Existing fatigue life prediction and crack propagation calculation methods generally tend to: 1. Assuming a single principal crack: Most methods focus on the propagation of a single crack, ignoring the possibility of multiple cracks in a component and their interactions.

[0004] 2. Ignoring initial defects: Many methods start the calculation from the crack initiation stage, failing to fully consider the significant impact of minor defects that already exist in the component at the time of manufacture or in the early stages of service on subsequent crack propagation.

[0005] 3. Simplified crack interactions: Even when considering multiple cracks, simple empirical models or distance criteria are often used, which fail to accurately capture the complex synergistic effects of the stress field at the crack tip, such as the shielding effect, the reinforcement effect, and the coalescence (merging) behavior of cracks.

[0006] These limitations lead to significant uncertainties and errors in existing methods for predicting the fatigue life of large and complex components such as rotor supports. This can result in either an overestimation (posing safety hazards) or an underestimation (causing unnecessary downtime for maintenance), thus affecting the safe and stable operation and economic benefits of hydropower units. Therefore, developing a calculation method that can more accurately reflect the collaborative propagation behavior of multiple cracks with initial defects under actual operating conditions has significant theoretical and engineering application value. Summary of the Invention

[0007] This application provides a method for calculating the collaborative propagation of multiple cracks in a hydropower unit rotor support, in order to solve the problems in the background art.

[0008] Other features and advantages of this application will become apparent from the following detailed description, or may be learned in part from practice of this application.

[0009] According to a first aspect of the embodiments of this application, a method for calculating the collaborative propagation of multiple cracks in a hydropower unit rotor support is provided, including: S100. Establish the geometric model of the rotor support of the hydropower unit and determine the initial defects and material property parameters; S200. Generate a load spectrum based on the actual operation records of the hydropower unit and apply boundary conditions to the geometric model of the rotor support. S300: Divide the load spectrum into several load cycle steps and initialize the current crack state as the initial defect; S400. In each load cycle step, the stress intensity factor at each crack tip under the current crack state is calculated by finite element analysis. S500 calculates the propagation rate and direction of each crack tip based on the stress intensity factor, updates the geometry, length and depth of all cracks, and merges cracks that meet preset conditions into new cracks. S600, repeat S400~S500 until any crack size reaches the preset failure criterion, and use the cumulative number of load cycle steps as the predicted fatigue life.

[0010] According to one embodiment of this application, the applied boundary conditions include: Constraints are applied based on the actual installation and stress conditions of the rotor support; the forces caused by centrifugal force, rotor weight, and electromagnetic load are applied to the corresponding surfaces or nodes; and a corresponding temperature field is applied.

[0011] According to one embodiment of this application, the step of calculating the stress intensity factor at each crack tip under the current crack state through finite element analysis specifically includes: In the current load cycle step, the transient geometric feature parameters of adjacent cracks are extracted, including the crack feature size and the feature distance between the corresponding crack tips; The isolated stress intensity factor of all cracks without considering interactions was calculated using finite element analysis. Determine the correction factor that takes into account the interaction; Based on the correction factor, the isolated stress intensity factor is corrected, and the effective stress intensity factor of each crack after considering the multi-crack interference effect is obtained.

[0012] According to one embodiment of this application, the method for determining the correction factor includes: Construct dimensionless geometric parameters; The correction factor is determined based on the dimensionless parameter by using a pre-established empirical polynomial formula or by referring to international structural integrity assessment standards.

[0013] According to one embodiment of this application, the method for determining the correction factor includes: A large number of high-precision finite element parametric scans were performed on the typical multi-crack arrangement of the rotor support in advance, and the actual stress intensity factor was extracted and fitted into the response surface function as the correction factor.

[0014] According to one embodiment of this application, the correction factor further includes constraints on quantifying the masking and enhancement effects, specifically including: When adjacent cracks are approximately coplanar and close to each other, the tensile stress fields at the crack tips are superimposed, resulting in an enhancement effect. The constraint correction factor F>1. If the calculated correction factor does not meet the constraint, the load cycle step size is adjusted and the correction factor is recalculated. When adjacent cracks are arranged in parallel and overlapping order, local strain energy is absorbed by each other, which manifests as a shielding effect. The constraint correction factor F < 1. If the calculated correction factor does not meet the constraint, the load cycle step size is adjusted and the correction factor is recalculated. When the characteristic distance between the corresponding crack tips is greater than the preset non-interference critical distance, the correction factor F=1 is directly set, which means it degenerates into an isolated crack.

[0015] According to one embodiment of this application, the method for calculating the expansion rate and expansion direction includes: Based on the corrected stress intensity factor range, the Paris fatigue crack propagation law or other propagation models are used to calculate the propagation rate of each crack tip under the current load cycle. The direction of each crack tip propagation in the next load cycle step is determined by using the maximum circumferential stress criterion, the minimum strain energy density criterion, or the maximum energy release rate criterion.

[0016] According to one embodiment of this application, updating the geometry, length, and depth of all cracks specifically includes: Based on the calculated propagation rate, calculate the crack length increment for the current load cycle step; The geometry, length, and depth of all cracks are updated by combining the crack length increment with the determined propagation direction.

[0017] According to one embodiment of this application, the process of fusing cracks that meet preset conditions into new cracks specifically includes: When the minimum distance between two adjacent crack tips is less than a preset threshold, it is determined that crack coalescence is required. When the stress fields near the tips of two cracks reach a predetermined degree of overlap, or when calculations show that the load-bearing area between them has been completely plasticized, it is determined that crack coalescence is required. The two cracks after aggregation will be treated as a new crack, its geometry will be refitted, and it will serve as the starting state for the next load cycle step.

[0018] According to one embodiment of this application, the preset destruction criterion includes: (1) The size of any crack reaches the critical crack size; (2) The remaining load-bearing capacity of the structure is lower than the design safety margin; (3) The stiffness, displacement or strain of the component reaches the failure limit; Among them, the stiffness, displacement or strain of the components, as well as the remaining load-bearing capacity of the structure, are obtained simultaneously through finite element analysis to calculate the stress intensity factor.

[0019] Compared with existing technologies, the beneficial effects of adopting the above technical solution are as follows: 1. Significantly improved accuracy: The method of this invention fully considers the initial defects that are common in rotor supports and the complex synergistic propagation effects among multiple cracks (including stress field interaction, crack propagation direction change and crack coalescence behavior), which greatly improves the accuracy and reliability of fatigue life prediction and avoids the overestimation or underestimation of traditional methods.

[0020] 2. Enhanced safety: By more accurately predicting crack propagation and eventual failure, potential safety risks can be effectively identified, providing early warnings for timely maintenance measures, thereby ensuring the safe and stable operation of hydropower units.

[0021] 3. Optimized economic benefits: Accurate life assessment helps optimize maintenance plans, avoid unnecessary downtime, extend the service life of components, reduce maintenance costs, and improve the unit's operating efficiency and economic benefits.

[0022] 4. Wide applicability: This method is not only applicable to rotor supports of hydropower units, but its core ideas and calculation process can also be extended to the evaluation of multi-crack propagation with defects in other large and complex structural components under fatigue loads.

[0023] 5. Provides guidance for design optimization: By identifying crack propagation paths and critical areas, it provides valuable references for rotor support design improvement, material selection, and manufacturing process optimization. Attached Figure Description

[0024] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0025] Figure 1 This is a flowchart illustrating the calculation method for the collaborative propagation of multiple cracks in the rotor support of a hydropower unit, as described in this application.

[0026] Figure 2 This is a three-dimensional geometric model of the rotor support of the hydropower unit according to an embodiment of this application, and a schematic diagram of its initial defects.

[0027] Figure 3 This is a schematic diagram illustrating the stress field change at the crack tip caused by multi-crack interaction according to an embodiment of this application, wherein... Figure 3 a is a schematic diagram of the independent stress fields of two isolated cracks located far apart. Figure 3 b is a schematic diagram of the stress field superposition and distortion caused by the interaction of adjacent cracks.

[0028] Figure 4 This is a schematic diagram of the crack polymerization process according to an embodiment of this application, wherein, Figure 4 'a' represents the independent expansion phase. Figure 4 b represents the aggregation determination phase. Figure 4 c represents the reassessment phase.

[0029] Figure 5 Example diagrams of crack propagation paths and life curves calculated using the method of this application.

[0030] Figure 6 This is a schematic diagram of the structure of an electronic device according to an embodiment of this application. Detailed Implementation

[0031] The embodiments of this application are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar modules or modules having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application. Rather, the embodiments of this application include all variations, modifications, and equivalents falling within the spirit and scope of the appended claims.

[0032] To address the inaccurate predictions caused by the single-crack assumption, neglect of initial defects, and simplification of crack interactions in existing technologies, this application proposes a multi-crack collaborative propagation calculation method for hydropower unit rotor supports with initial defects. This method can effectively improve the fatigue life assessment accuracy and structural reliability of rotor supports.

[0033] Please refer to Figure 1 The calculation method for the coordinated propagation of multiple cracks in the rotor support of this hydropower unit specifically includes the following steps: S100. Establish the geometric model of the rotor support of the hydropower unit and determine the initial defects and material property parameters.

[0034] In this embodiment, a high-precision three-dimensional geometric model of the rotor support of the hydropower unit to be analyzed is established based on the actual engineering drawings and dimensions, and finite element meshing is performed. In one embodiment, a detailed three-dimensional solid geometric model of the rotor support can be established using commercial finite element software (such as ABAQUS, ANSYS, etc.) or CAD software (such as SolidWorks, Pro / E, etc.). The model should include all key structural features, connection points, and geometric discontinuities.

[0035] Furthermore, after completing the modeling, it is also necessary to accurately define initial defects in key areas of the geometric model (such as weld zones, stress concentration zones, and material discontinuity zones), such as... Figure 2 As shown. In this embodiment, the initial defect data includes data based on non-destructive testing (NDT) data, material manufacturing defect statistics, or design specifications. NDT data includes defect size, location, and type obtained from ultrasonic testing, magnetic particle testing, penetrant testing, etc. Material manufacturing defect statistics include statistical patterns of internal material defects. Design specifications include the allowable range and typical morphology of weld defects. If crack propagation needs to be predicted, n-code software is also needed to calculate the fatigue loss region to obtain defect size and location for crack implantation.

[0036] Specifically, initial defects include, but are not limited to, surface cracks (such as semi-elliptical cracks), internal cracks (such as circular or elliptical cracks), or other irregularly shaped defects. For each defect, its location coordinates (x, y, z), dimensional parameters (half-length c, depth a), shape (semi-elliptical, circular, etc.), and local orientation within the structure are precisely defined. For example, in the weld area of ​​a rotor support, multiple initial semi-elliptical surface cracks are defined.

[0037] To more realistically simulate the rotor support, it is also necessary to inject the rotor support material property parameters (such as the elastic modulus E, Poisson's ratio ν, yield strength, tensile strength, and fatigue crack propagation rate (Paris's law parameters C and m) of the rotor support into the established geometric model. These parameters are usually obtained through material testing.

[0038] S200. Generate a load spectrum based on the actual operation records of the hydropower unit and apply boundary conditions to the geometric model of the rotor support.

[0039] In this embodiment, load data of the hydropower unit rotor support under typical operating conditions (such as startup, normal operation, load changes, shutdown, short circuit, etc.) are collected and converted into a discrete cyclic load spectrum. Simultaneously, constraints are applied to the finite element model based on the actual installation and stress conditions of the rotor support, such as base fixing constraints and bearing support constraints. Centrifugal force, rotor self-weight, and forces caused by electromagnetic loads are applied to the corresponding surfaces or nodes. For thermal stress, a corresponding temperature field can be applied.

[0040] S300: Divide the load spectrum into several load cycle steps and initialize the current crack state as the initial defect.

[0041] Based on the finite element model established by S100~S200 and the determined load spectrum, the life of the rotor support can be predicted and analyzed. In this embodiment, an incremental iteration method is used to divide the load spectrum into several small load cycle steps to achieve the iterative calculation process.

[0042] S400. In each load cycle step, the stress intensity factor at each crack tip under the current crack state is calculated by finite element analysis.

[0043] When performing iterative calculations, the number of iterations N is initialized to 0, and the current crack state is set to the initial defect state determined by S100.

[0044] In the current load cycle step, stress field analysis is performed on the rotor support containing initial defects using the finite element method. For each crack tip of all initial defects (or propagated cracks) in the model, the stress intensity factor (SIF) is calculated precisely.

[0045] In this embodiment, the interaction effect between adjacent cracks is fully considered and quantified in the calculation of stress intensity factor. When multiple cracks are close to each other, the stress intensity factor at the tip of each crack is corrected by superposition principle, bilinear interpolation method or specific interaction function so that it can reflect the shielding (reducing SIF) or enhancement (increasing SIF) effect.

[0046] Specifically, static or transient structural analysis is performed using commercial finite element software (such as ABAQUS / Standard, ANSYS Mechanical, etc.). For crack tips, the following numerical fracture mechanics methods can be used for analysis: (1) Extended Finite Element Method (XFEM): It is suitable for irregular cracks and crack propagation without the need for re-meshing, and can effectively handle multi-crack problems.

[0047] (2) Submodeling: A fine mesh submodel is established in the key local area where the crack is located, while the overall model uses a coarse mesh to balance computational efficiency and accuracy.

[0048] (3) Virtual Crack Closure Technology (VCCT): The stress intensity factor is obtained by calculating the energy release rate required for a crack to propagate a small increment.

[0049] For each crack tip, its stress intensity factor ΔK can be calculated under the current load cycle step. single However, when multiple cracks are close to each other, their stress fields will affect each other, such as... Figure 3 As shown. Considering the complex coupling effect of the stress field at the tips of multiple cracks in the rotor support, directly solving the partial differential equations for multiple cracks involves a huge computational burden. To improve engineering calculation efficiency and ensure accuracy, this embodiment adopts a method of introducing a multi-crack interaction correction factor F to quantitatively correct the stress intensity factor of isolated cracks. The specific process is as follows: S401, Parameter Extraction: In the current load cycle step, extract the transient geometric feature parameters of adjacent cracks, including crack feature dimensions (such as crack depth a, surface length 2c) and the feature distance d between the corresponding crack tips; S402. Calculate the isolated stress intensity factor: Assuming that each crack exists independently in the component, calculate the isolated stress intensity factor ΔK without considering interactions using the finite element method or classical analytical formulas of fracture mechanics. single .

[0050] S403. Determine the correction factor considering interactions. This embodiment provides two methods for obtaining the correction factor, as follows: (1) Construct dimensionless geometric parameters such as distance-to-size ratio d / a or d / 2c. Based on the dimensionless parameters, determine the correction factor by using a pre-established empirical polynomial formula or by referring to international structural integrity assessment standards (such as API 579 or BS 7910), F=1+c1(d / a). -1 + c2(d / a) -2 .

[0051] (2) A large number of high-precision finite element parametric scans were performed on the typical multi-crack arrangement of the rotor support in advance, and the actual stress intensity factor was extracted and the fitted response surface function F(d, a, c, θ) was used as the correction factor.

[0052] Furthermore, this embodiment also provides a quantification method for the masking and enhancement effects regarding the correction factor. Specifically, when adjacent cracks are approximately coplanar and close to each other, the tensile stress fields at the crack tips superimpose, exhibiting an enhancement effect, thus limiting the correction factor F to > 1. If the previously calculated correction factor is less than 1, the step size ΔN of the current load cycle needs to be adjusted. When adjacent cracks are parallel and overlapping, local strain energy is mutually absorbed, exhibiting a masking effect, thus limiting the correction factor F to < 1. If the previously calculated correction factor is greater than 1, the step size ΔN of the current load cycle also needs to be adjusted. When the characteristic distance between adjacent crack tips is greater than the preset non-interference critical distance, the correction factor F is limited to 1, i.e., it degenerates into an isolated crack. In practical applications, if the characteristic distance between adjacent crack tips is greater than the preset non-interference critical distance, the correction factor F is directly set to 1, eliminating the need for the aforementioned calculation processes S402~S403, thus reducing the computational load.

[0053] Based on the determined correction factor, the isolated stress intensity factor is corrected to obtain the effective stress intensity factor ΔK considering the multi-crack interference effect. eff That is, ΔK eff = F × ΔK single .

[0054] S500 calculates the propagation rate and direction of each crack tip based on the stress intensity factor, updates the geometry, length and depth of all cracks, and merges cracks that meet preset conditions into new cracks.

[0055] Based on the determined effective stress intensity factor ΔK eff The fatigue crack propagation law equation da / dN = C(ΔK) can be used. eff ) m Calculate the propagation rate at each crack tip. Since the equation contains an exponential term m (usually m ≈ 3), the influence of the correction factor F on the final crack propagation rate is amplified to a factor of F^m. This mechanism can extremely sensitively capture minute changes in stress field interactions, fundamentally overcoming the technical bias of traditional methods that distort rotor support fatigue life predictions due to neglecting local interactions.

[0056] For determining the crack propagation direction, this embodiment uses any one of the following criteria: maximum circumferential stress criterion, minimum strain energy density criterion, or maximum energy release rate criterion, to determine the propagation direction of each crack tip in the next load cycle step. The maximum circumferential stress criterion (MTS) states that the crack tends to propagate along the direction of the maximum circumferential stress at the crack tip. The small angle of the next crack propagation is determined by calculating the stress distribution in front of the crack tip. The maximum energy release rate criterion states that the crack propagates along the direction of the maximum energy release rate.

[0057] Based on the previously calculated propagation rate da / dN, the crack length increment Δa = (da / dN) for the current load cycle step can be calculated. ΔN, where ΔN is the step size of the load cycle. The geometry, length, and depth of all cracks are updated by combining the crack length increment with the determined propagation direction.

[0058] This embodiment also provides specific multi-crack fusion criteria. When a corresponding crack meets preset conditions, a crack fusion operation needs to be performed. The specific preset conditions are: (1) When the minimum distance between two adjacent crack tips is less than a preset threshold (e.g., a multiple of the minimum crack length or the characteristic length of the material), it is determined that crack coalescence is required; (2) When the stress field near two crack tips reaches a preset overlap, or calculations show that the load-bearing area between them has been completely plasticized, it is determined that crack coalescence is required. The two merged cracks will be treated as a new crack, with its geometry, length, and depth refitted (e.g., forming a larger semi-elliptical crack), and will serve as the starting state for the next load cycle step, such as... Figure 4 As shown.

[0059] Existing technologies often rely solely on simple static geometric distances to determine crack coalescence. This embodiment innovatively introduces a composite criterion of "distance threshold + severe stress field overlap," capturing coalescence behavior based on real mechanical driving factors, significantly improving the accuracy of the determination. Furthermore, existing solutions often experience computational interruptions due to abrupt shape changes at crack contact. This embodiment, after determining coalescence, can merge multiple cracks and reconstruct them into a single, larger crack with new geometric parameters, updating this state to serve as the starting point for subsequent calculations, thus overcoming the computational bottleneck after crack connectivity.

[0060] S600, repeat S400~S500 until any crack size reaches the preset failure criterion, and use the cumulative number of load cycle steps as the predicted fatigue life.

[0061] By repeating steps S400 to S500, the geometry, length, and depth of all cracks are updated in each load cycle step. The stress intensity factor at the updated crack tip is calculated, and the latest interactions between cracks are considered. When re-performing the finite element analysis in each load cycle step, in addition to calculating the stress intensity factor at the crack tip, the displacement and strain fields of key nodes in the rotor support under the current crack geometry are simultaneously extracted. The current macroscopic stiffness of the component is calculated based on the response relationship between external load and node displacement. Simultaneously, the stress distribution of the uncracked net section is extracted, and its remaining load-bearing capacity is assessed based on the yield strength.

[0062] Each time a loop is completed, the number of loops is N+1, and it is checked whether there are cracks that reach the preset failure criterion. If not, the loop iteration continues. If it does reach the criterion, the number of loops N is output. The total time corresponding to the number of loops N is the fatigue life of the hydropower unit rotor support considering the initial defects and the synergistic propagation of multiple cracks.

[0063] In this embodiment, the preset failure criteria include: (1) the size of any crack reaches the critical crack size; (2) the remaining bearing capacity of the structure is lower than the design safety margin; and (3) the stiffness, displacement or strain of the component reaches the failure limit.

[0064] This embodiment uses an incremental iteration method. After crack coalescence and geometric reconstruction, a new finite element analysis is performed and the latest interactive stress intensity factor is calculated. This avoids overestimation or underestimation of component life by traditional methods and greatly improves prediction accuracy.

[0065] In practical applications, data generated from iterative processes, such as crack propagation paths, rates, remaining lifespan, and crack coalescence history at key components of the rotor support, are used. Post-processing software is then employed to visualize these crack propagation paths, rates, and coalescence processes. Figure 5 As shown. A detailed life assessment report is generated, including the remaining life of each critical region, the propagation history of the most dangerous crack, failure modes, etc. If material and load parameters are uncertain, a reliability assessment can be performed using Monte Carlo methods or probabilistic analysis methods to provide the structural remaining life at a specific confidence level.

[0066] At the same time, based on the assessment report, specific maintenance and repair recommendations can be made to the hydropower unit operator, which may include: areas that need to be monitored, recommended time intervals for the next non-destructive testing, whether parts need to be repaired or replaced, and recommendations for adjusting operating parameters to slow down crack propagation, etc.

[0067] Based on the above process, the present invention can accurately calculate and predict the life of multi-crack collaborative propagation behavior of rotor supports of hydropower units with initial defects, thereby providing scientific guidance for the safe operation and maintenance of hydropower units.

[0068] Based on the same technical concept, this application also provides an electronic device that can implement the calculation method for the collaborative propagation of multiple cracks in the rotor support of a hydroelectric generator provided in the above embodiments of the present invention. In one embodiment, the electronic device can be a server, a terminal device, or other electronic equipment. Figure 6 As shown, the electronic device may include: At least one processor and a memory connected to the at least one processor. In this embodiment of the invention, the specific connection medium between the processor and the memory is not limited. Figure 6The example used is the connection between the processor and memory via a bus. The bus... Figure 6 The connections between other components are indicated by thick lines and are for illustrative purposes only, not as limiting information. Buses can be categorized into address buses, data buses, control buses, etc., but for ease of representation, [the specific bus type is not shown here]. Figure 6 The processor is represented by a single thick line, but this does not imply that there is only one bus or one type of bus. Alternatively, a processor can also be called a controller; there are no restrictions on the name.

[0069] In this embodiment of the invention, the memory stores instructions executable by at least one processor. By executing the instructions stored in the memory, the at least one processor can perform the multi-crack collaborative propagation calculation method for a hydroelectric generator rotor support described above. The processor can implement... Figure 6 The functions of each module in the device shown.

[0070] The processor is the control center of the device. It can connect to various parts of the control device through various interfaces and lines. By running or executing instructions stored in memory and calling data stored in memory, it can monitor the device's various functions and process data, thereby enabling overall monitoring of the device.

[0071] In an alternative design, the processor may include one or more processing units. The processor may integrate an application processor and a modem processor, wherein the application processor primarily handles the operating system, user interface, and applications, while the modem processor primarily handles wireless communication. It is understood that the modem processor may also not be integrated into the processor. In some embodiments, the processor and memory may be implemented on the same chip; in some embodiments, they may also be implemented separately on separate chips.

[0072] The processor can be a general-purpose processor, such as a CPU, digital signal processor, application-specific integrated circuit, field-programmable array, or other programmable logic device, discrete gate or transistor logic device, or discrete hardware component, capable of implementing or executing the methods, steps, and logic block diagrams disclosed in the embodiments of this invention. The general-purpose processor can be a microprocessor or any conventional processor. The steps of the multi-crack collaborative propagation calculation method for a hydropower unit rotor support disclosed in the embodiments of this invention can be directly manifested as being executed by a hardware processor, or being executed by a combination of hardware and software modules within the processor.

[0073] Memory, as a non-volatile computer-readable storage medium, can be used to store non-volatile software programs, non-volatile computer-executable programs, and modules. Memory can include at least one type of storage medium, such as flash memory, hard disk, multimedia card, card-type memory, random access memory (RAM), static random access memory (SRAM), programmable read-only memory (PROM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), magnetic memory, magnetic disk, optical disk, etc. Memory is any other medium capable of carrying or storing desired program code in the form of instructions or data structures, and accessible by a computer, but is not limited thereto. In embodiments of the present invention, memory can also be a circuit or any other device capable of implementing storage functions, used to store program instructions and / or data.

[0074] By designing and programming the processor, the code corresponding to the multi-crack collaborative propagation calculation method for the hydropower unit rotor support described in the foregoing embodiments can be embedded into the chip, thereby enabling the chip to execute the steps of the method described in the foregoing embodiments during operation. How to design and program the processor is a technique well known to those skilled in the art, and will not be elaborated here.

[0075] Based on the same inventive concept, embodiments of the present invention also provide a storage medium storing computer instructions, which, when executed on a computer, cause the computer to perform the aforementioned calculation method for the collaborative propagation of multiple cracks in a hydropower unit rotor support.

[0076] In some alternative embodiments, the present invention also provides a method for calculating the collaborative propagation of multiple cracks in a hydropower unit rotor support, which can also be implemented as a program product including program code. When the program product is run on a device, the program code is used to cause the control device to perform the steps in the method for calculating the collaborative propagation of multiple cracks in a hydropower unit rotor support according to various exemplary embodiments of the present invention as described in this specification.

[0077] It should be noted that although several units or sub-units of the apparatus have been mentioned in the detailed description above, this division is merely exemplary and not mandatory. In fact, according to embodiments of the invention, the features and functions of two or more units described above can be embodied in one unit. Conversely, the features and functions of one unit described above can be further divided and embodied by multiple units. Furthermore, although the operation of the method of the invention is described in a specific order in the drawings, this does not require or imply that these operations must be performed in that specific order, or that all the operations shown must be performed to achieve the desired result. Additionally or alternatively, certain steps may be omitted, multiple steps may be combined into one step, and / or one step may be broken down into multiple steps.

[0078] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0079] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a server, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0080] Program code for performing the operations of this invention can be written using any combination of one or more programming languages, including object-oriented programming languages ​​such as Java and C++, as well as conventional procedural programming languages ​​such as C or similar languages. The program code can be executed entirely on the user's computing device, partially on the user's device, as a standalone software package, partially on the user's computing device and partially on a remote computing device, or entirely on a remote computing device or server.

[0081] In cases involving remote computing devices, the remote computing device can be connected to the user's computing device via any type of network, including a local area network (LAN) or a wide area network (WAN), or it can be connected to an external computing device (e.g., via the Internet using an Internet service provider).

[0082] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0083] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0084] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for calculating the coordinated propagation of multiple cracks in a hydropower unit rotor support, characterized in that, include: S100. Establish the geometric model of the rotor support of the hydropower unit and determine the initial defects and material property parameters; S200. Generate a load spectrum based on the actual operation records of the hydropower unit and apply boundary conditions to the geometric model of the rotor support. S300: Divide the load spectrum into several load cycle steps and initialize the current crack state as the initial defect; S400. In each load cycle step, the stress intensity factor at each crack tip under the current crack state is calculated by finite element analysis. S500 calculates the propagation rate and direction of each crack tip based on the stress intensity factor, updates the geometry, length and depth of all cracks, and merges cracks that meet preset conditions into new cracks. S600, repeat S400~S500 until any crack size reaches the preset failure criterion, and use the cumulative number of load cycle steps as the predicted fatigue life.

2. The calculation method for the coordinated propagation of multiple cracks in the rotor support of a hydropower unit according to claim 1, characterized in that, The applied boundary conditions include: Constraints are applied based on the actual installation and stress conditions of the rotor support; the forces caused by centrifugal force, rotor weight, and electromagnetic load are applied to the corresponding surfaces or nodes; and a corresponding temperature field is applied.

3. The calculation method for the coordinated propagation of multiple cracks in the rotor support of a hydropower unit according to claim 1, characterized in that, The calculation of stress intensity factors at the crack tips under the current crack state through finite element analysis specifically includes: In the current load cycle step, the transient geometric feature parameters of adjacent cracks are extracted, including the crack feature size and the feature distance between the corresponding crack tips; The isolated stress intensity factor of all cracks without considering interactions was calculated using finite element analysis. Determine the correction factor that takes into account the interaction; Based on the correction factor, the isolated stress intensity factor is corrected, and the effective stress intensity factor of each crack after considering the multi-crack interference effect is obtained.

4. The calculation method for the coordinated propagation of multiple cracks in the rotor support of a hydropower unit according to claim 3, characterized in that, The method for determining the correction factor includes: Construct dimensionless geometric parameters; The correction factor is determined based on the dimensionless parameter by using a pre-established empirical polynomial formula or by referring to international structural integrity assessment standards.

5. The calculation method for the coordinated propagation of multiple cracks in the rotor support of a hydropower unit according to claim 3, characterized in that, The method for determining the correction factor includes: A large number of high-precision finite element parametric scans were performed on the typical multi-crack arrangement of the rotor support in advance, and the actual stress intensity factor was extracted and fitted into the response surface function as a correction factor.

6. The calculation method for the coordinated propagation of multiple cracks in the rotor support of a hydropower unit according to claim 3, characterized in that, The correction factor also includes constraints on quantifying the masking and enhancement effects, specifically including: When adjacent cracks are approximately coplanar and close to each other, the tensile stress fields at the crack tips are superimposed, resulting in an enhancement effect. The constraint correction factor F>1. If the calculated correction factor does not meet the constraint, the load cycle step size is adjusted and the correction factor is recalculated. When adjacent cracks are arranged in parallel and overlapping order, local strain energy is absorbed by each other, which manifests as a shielding effect. The constraint correction factor F < 1. If the calculated correction factor does not meet the constraint, the load cycle step size is adjusted and the correction factor is recalculated. When the characteristic distance between the corresponding crack tips is greater than the preset non-interference critical distance, the correction factor F=1 is directly set, which means it degenerates into an isolated crack.

7. The calculation method for the coordinated propagation of multiple cracks in the rotor support of a hydropower unit according to claim 1, characterized in that, The methods for calculating the expansion rate and expansion direction include: Based on the corrected stress intensity factor range, the Paris fatigue crack propagation law or other propagation models are used to calculate the propagation rate of each crack tip under the current load cycle. The direction of each crack tip propagation in the next load cycle step is determined by using the maximum circumferential stress criterion, the minimum strain energy density criterion, or the maximum energy release rate criterion.

8. The calculation method for the coordinated propagation of multiple cracks in the rotor support of a hydropower unit according to claim 1, characterized in that, The updating of the geometry, length, and depth of all cracks specifically includes: Based on the calculated propagation rate, calculate the crack length increment for the current load cycle step; The geometry, length, and depth of all cracks are updated by combining the crack length increment with the determined propagation direction.

9. The calculation method for the coordinated propagation of multiple cracks in the rotor support of a hydropower unit according to claim 1, characterized in that, The process of fusing cracks that meet preset conditions into new cracks specifically includes: When the minimum distance between two adjacent crack tips is less than a preset threshold, it is determined that crack coalescence is required. When the stress fields near the tips of two cracks reach a predetermined degree of overlap, or when calculations show that the load-bearing area between them has been completely plasticized, it is determined that crack coalescence is required. The two cracks after aggregation will be treated as a new crack, its geometry will be refitted, and it will serve as the starting state for the next load cycle step.

10. The calculation method for the coordinated propagation of multiple cracks in the rotor support of a hydropower unit according to claim 1, characterized in that, The preset destruction criteria include: (1) The size of any crack reaches the critical crack size; (2) The remaining load-bearing capacity of the structure is lower than the design safety margin; (3) The stiffness, displacement or strain of the component reaches the failure limit; Among them, the stiffness, displacement or strain of the components, as well as the remaining load-bearing capacity of the structure, are obtained simultaneously through finite element analysis to calculate the stress intensity factor.

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