A calculation method and system for unbalanced forces caused by cracks in an aeroengine disk

Abstract

The present invention discloses a calculation method and system for unbalanced force caused by cracks in an aeroengine disk. The method includes: collecting the attribute parameters of the disk and the disk cracks; establishing a finite element model of the cracked disk based on finite element analysis software, simulating and analyzing the variation law of the maximum crack opening displacement at different rotational speeds, and establishing a functional relationship between the maximum crack opening displacement and the rotational speed under cyclic load; considering the influence of crack length and crack morphology, correcting the functional relationship; based on the obtained functional relationship, calculating the magnitude of the unbalanced force caused by the disk cracks in the form of the product of mass and radius; comparing the magnitude of the unbalance calculated by the change of the overall centroid obtained through finite element simulation, comparing the calculation results, and correcting the calculation formula for the unbalanced force caused by the disk cracks; the present invention considers the plastic deformation generated at the crack tip of the disk under fatigue load, analyzes the variation law of the unbalanced force generated by the crack under cyclic load, and is closer to the actual working conditions.

Description

Technical Field

[0001] The invention belongs to the field of mechanical engineering and relates to a method and a system for calculating unbalanced force caused by cracks in a wheel disc of an aero-engine. Background Art

[0002] The disc is the core component of an aircraft engine. Due to the high temperature, high pressure and high speed environment, cracks are easily generated at the stress concentration point, and eventually failure and damage occur. Disc failure will directly affect the reliability and maintenance cost of the engine, and even endanger the safety of the aircraft crew. In order to ensure the safe operation of aircraft engines and realize the early identification and diagnosis of disc cracks, it is necessary to study the fault mechanism of disc cracks.

[0003] In recent years, many scholars at home and abroad have conducted a large number of experiments on disk crack failures and conducted related dynamic research. Haase WC and Drumm MJ of ExSell Company in the United States established a physical model of the disk using the damping ratio, initial eccentricity and eccentricity caused by cracks as parameters under the assumption that cracks cause changes in the center of mass of the disk, and verified the physical model in a low-cycle fatigue pit test. Luo H, Rodriguez H, Hallman D and others from GE's Aero Engine Research Center and Global Research Institute conducted a project study on "Turbine disk crack detection for pre-set engine failures", extending the single-degree-of-freedom model to a multi-degree-of-freedom model, and established a multi-degree-of-freedom non-resonant turbine disk model. The effectiveness of the model was verified in a laboratory environment using a small rotor model with controllable unbalance. Jia Binghui, Feng Yong and Yan Guodong and others from Chang'an University established an aircraft engine disk rotor reduction model. On the basis of considering the thermal stress and centrifugal force of the rotor components, they focused on the impact of cracks of different depths on the tip clearance when they occur at different positions on the disk.

[0004] Most of these studies are based on the assumption that the opening of a crack in a rotor can cause unbalanced forces (Eric H. Real-time detection of developing cracks in jet engine rotors [C] / / 2000 IEEE Aerospace Conference. Proceedings (Cat. No. 00TH8484). IEEE, 2000, 6: 173-183.), which means that under the action of centrifugal force, the crack in the rotor causes the stress-strain field to distort, causing the position of the rotor's center of mass to change, causing imbalance. Among them, the key parameter for measuring the magnitude of the unbalanced force caused by cracks in the rotor is the Crack Maximum Opening Displacement (CMOD).

[0005] However, existing literature rarely considers the influence of rotational speed changes on the magnitude of the unbalanced force generated by wheel disc cracks. Wheel disc crack faults are often breathing cracks caused by low-cycle fatigue. Affected by cyclic loads, the maximum opening displacement of the crack changes with the rotational speed, and the resulting unbalanced force also varies. In addition, current calculation methods for the maximum opening displacement of cracks are all based on linear elastic fracture mechanics. However, since the wheel disc operates at high rotational speeds and bears large loads, when cracks appear on the wheel disc, a large plastic region appears at the crack tip, which will have a certain impact on the variation law of the maximum opening displacement of the crack under cyclic loads. Linear elastic fracture mechanics cannot solve this problem, so it is necessary to utilize relevant theories of elastic-plastic fracture mechanics.

[0006] Therefore, there is an urgent need for a calculation method for the unbalanced force caused by cracks in an aero-engine wheel disc under high rotational speed cyclic loads. Summary of the Invention

[0007] The purpose of the present invention is to provide a calculation method for the unbalanced force caused by cracks in an aero-engine wheel disc to solve one or more of the above-mentioned technical problems. The calculation method of the present invention utilizes relevant theories of elastic-plastic fracture mechanics to analyze the magnitude of the unbalanced force generated by wheel disc cracks under cyclic loads, which is closer to the actual working conditions and can provide theoretical guidance for the early identification and diagnosis of aero-engines.

[0008] To achieve the above object, the present invention adopts the following technical solutions: A calculation method for the unbalanced force caused by cracks in an aero-engine wheel disc, comprising the following steps:

[0009] S1, collect the attribute parameters of the wheel disc and wheel disc cracks of the aero-engine;

[0010] S2, based on the non-linear numerical simulation analysis software Abaqus, establish a finite element model of the cracked wheel disc. Specifically, a cyclic loading method is used to simulate the low-cycle fatigue process of the wheel disc, and each cycle includes three stages: loading - holding - unloading;

[0011] S3, according to the finite element model of the cracked wheel disc established in S2, simulate and analyze the variation law of the maximum opening displacement of the crack at different maximum rotational speeds, and establish a functional relationship between the maximum opening displacement of the crack and the rotational speed under cyclic loads;

[0012] S4, according to the functional relationship obtained in S3, analyze the influence of crack length and crack morphology on the variation law of the maximum opening displacement of the wheel disc crack under cyclic loads, and correct the functional relationship between the maximum opening displacement of the crack and the rotational speed;

[0013] S5, according to the corrected functional relationship between the maximum opening displacement of the crack and the rotational speed obtained in S4, simplify the crack opening shape, and calculate through the form of the product of mass and radius, and establish a calculation model for the unbalanced force caused by wheel disc cracks;

[0014] S6. Based on the finite element model of the cracked disk established in S2, the change value of the centroid offset of the disk is obtained through simulation analysis. The magnitude of the unbalance is calculated based on the change value of the centroid offset, and the unbalance force calculation model caused by the disk crack established in S5 is corrected to obtain the unbalance force caused by the disk crack.

[0015] In S1, the attribute parameters of the disk rotor system and the disk of the aero-engine include: geometric dimension parameters and material property parameters; the attribute parameters of the disk crack include: crack morphology and crack length, and the crack morphology includes circumferential crack and radial crack.

[0016] In S2, the steps for establishing the finite element model of the cracked disk include the following:

[0017] S2.1. Establish the geometric model of the cracked disk;

[0018] S2.2. Divide the finite element mesh for the geometric model, set the material properties, mesh type, analysis step type, boundary conditions, load, and output results to establish the finite element model of the cracked disk; the material properties, boundary conditions, and load are determined with reference to the actual working conditions of the engine; the output result refers to the maximum crack opening displacement in the finite element model.

[0019] In S2.2, the hexahedral eight-node element is used to perform finite mesh division on the disk. For the crack tip region with stress concentration, the mesh is divided by means of region segmentation and setting the number of seed points. In other regions of the disk, the appropriate mesh size is set by means of size control; the mesh density in the crack tip region is greater than that in other regions.

[0020] In S2.2, the nonlinear factor of elastoplastic theory is introduced in the material property setting. When analyzing the stress-strain relationship in the plastic zone, a combined kinematic hardening and isotropic hardening model is adopted. The isotropic part in the combined hardening model adopts the Voce's nonlinear isotropic hardening criterion, and the kinematic hardening part in the combined hardening model adopts the Chaboche's nonlinear kinematic hardening model with three-term back stress.

[0021] S3 specifically includes performing finite element simulation on the relationship between the maximum crack opening displacement and the rotational speed under cyclic load, obtaining the conclusion that the maximum crack opening displacement under cyclic load follows different change laws during the speed-up and speed-down processes, and using the relationship between the change amount Δu of the maximum crack opening displacement and the change amount Δω of the rotational speed to solve the functional relationship between the maximum crack opening displacement and the rotational speed by means of quadratic function fitting;

[0022] During the speed-up process, a quadratic polynomial between Δu and Δω is established through polynomial fitting; during the speed-down process, when establishing a quadratic polynomial of two parameters through polynomial fitting, the variables are transformed; finally, the functional relationship between the two variables is obtained:

[0023]

[0024] In the formula, u min is the maximum crack opening displacement at the start of speed-up; u max is the maximum crack opening displacement at the start of speed-down.

[0025] In S4, considering the influence of crack length: change the crack length to analyze the influence of crack length on the variation law of the maximum crack opening displacement under cyclic load, and it is obtained that the change amount of the maximum crack opening displacement is proportional to the crack length;

[0026] Considering the influence of crack shape: the circumferential crack is the same as the radial crack. For the speed-up process, analyze the relationship between the change amount Δu of the maximum crack opening displacement and the change amount Δω of the rotational speed; for the speed-down process, analyze the variation law with the change of Δω / ω max to obtain the functional relationship between the maximum circumferential crack opening displacement and the rotational speed:

[0027]

[0028] Among them, l is the crack length, a 3 , a 4 and b 4 are the correlation coefficients for the speed-up and speed-down processes.

[0029] In S5, calculate the equivalent unbalance amount generated by the wheel disc crack by calculating the size of the missing mass. Simplify the shape of the radial crack into an isosceles triangle to calculate the mass of the missing part caused by the crack, and simplify the shape of the circumferential crack into an ellipse to calculate the mass of the missing part caused by the crack.

[0030] Based on the concept described in the present invention, a calculation system for the unbalanced force caused by the wheel disc crack of an aero-engine is also provided, including a parameter acquisition module, a model construction module, a first calculation module, a first correction module, a second calculation module, and a second correction module;

[0031] The parameter acquisition module is used to acquire the attribute parameters of the wheel disc and the wheel disc crack of the aero-engine;

[0032] The model construction module is used for the nonlinear numerical simulation analysis software Abaqus to establish a finite element model of the wheel disc with cracks. Specifically, the cyclic loading method is adopted to simulate the low-cycle fatigue process of the wheel disc, and each cycle includes three stages: loading - holding - unloading;

[0033] The first calculation module is used to simulate and analyze the variation law of the maximum crack opening displacement at different maximum rotational speeds based on the finite element model of the cracked disk, and establish a functional relationship between the maximum crack opening displacement and the rotational speed under cyclic loading;

[0034] The first correction module is used to analyze the influence of the crack length and crack morphology on the variation law of the maximum crack opening displacement of the disk under cyclic loading according to the functional relationship obtained by the first calculation module, and correct the functional relationship between the maximum crack opening displacement and the rotational speed;

[0035] The second calculation module simplifies the crack opening shape according to the functional relationship between the maximum crack opening displacement and the rotational speed corrected by the first modification module, and calculates through the form of the product of mass and radius to establish an unbalanced force calculation model caused by the disk crack;

[0036] The second correction module simulates and analyzes the change value of the centroid offset of the disk according to the finite element model of the cracked disk, calculates the magnitude of the unbalance through the change value of the centroid offset, and corrects the unbalanced force calculation model obtained by the second calculation module to obtain the unbalanced force caused by the disk crack.

[0037] In addition, a computer device is also provided, including a processor and a memory. The memory is used to store computer-executable programs. The processor reads the computer-executable programs from the memory and executes them. When the processor executes the computer-executable programs, it can implement the calculation method for the unbalanced force caused by the disk crack of the aero-engine of the present invention.

[0038] Compared with the prior art, the present invention has the following beneficial effects: The calculation method for the unbalanced force of the aero-engine disk crack of the present invention considers the plastic deformation generated at the crack tip of the disk under fatigue loading. Based on the relevant theories of elastic-plastic fracture mechanics, through finite element simulation, it is analyzed that under cyclic loading, the crack opening has different variation laws with the rotational speed during the acceleration and deceleration processes, and then the variation law of the unbalanced force generated by the disk crack with the rotational speed is obtained. When analyzing the variation law of the maximum crack opening with the rotational speed, the influence of the crack length and crack morphology on the unbalanced force generated by the disk crack is considered, and the obtained law is extended to a more general situation, making the calculated unbalanced force more accurate and closer to the actual working conditions. In addition, the method of the present invention can obtain the magnitude of the unbalanced force of the disk crack at any rotational speed, and can provide a basis and theoretical guidance for disk crack detection and disk crack mechanism analysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is a schematic flowchart of a calculation method for the unbalanced force caused by the disk crack of an aero-engine of the present invention;

[0040] Figure 2 is a schematic diagram of the disk geometric model in an embodiment of the present invention;

[0041] Figure 3 is a schematic diagram of the finite element model mesh generation in the embodiment of the present invention;

[0042] Figure 4 is a schematic diagram of the acceleration and deceleration curve of the finite element model in the embodiment of the present invention;

[0043] Figure 5 is a schematic diagram of the curve of the maximum opening displacement of the crack varying with the rotational speed under cyclic loading in the embodiment of the present invention;

[0044] Figure 6 is a schematic diagram of the variation of Δu with Δω under cyclic loading in the embodiment of the present invention;

[0045] Figure 7 is during the deceleration process in the embodiment of the present invention varying with Δω / ω max schematic diagram;

[0046] Figure 8 is a schematic diagram of the variation of Δu / l with Δω at different crack lengths in the embodiment of the present invention;

[0047] Figure 9 is a schematic diagram of the unbalanced force caused by the crack of the disk in the embodiment of the present invention;

[0048] Figure 10 is a schematic diagram of the comparison and correction of the unbalance calculated by different calculation methods in the embodiment of the present invention. Detailed implementation manners

[0049] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and at the same time verify that the method of the present invention can represent the variation law of the unbalanced force generated by the crack of the aeroengine disk. However, this embodiment is not used to limit the present invention, but only for explanation.

[0050] Please refer to Figure 1 , a calculation method for the unbalanced force caused by the crack of the aeroengine disk in the embodiment of the present invention, includes the following steps:

[0051] Step 1), collect and input the attribute parameters of the disk and the crack of the aeroengine to provide data support for subsequent finite element modeling.

[0052] Specifically, in step 1), the input attribute parameters include the geometric dimensions of each component, material property parameters (Young's modulus, Poisson's ratio, density, shear modulus), and the disk crack parameters also include the crack shape and crack length. These parameters can be obtained through simple geometric measurements and querying materials, without obtaining parameters such as the natural frequency and transfer function of the system through complex modal experiments.

[0053] Step 2), according to the property parameters given in Step 1), establish a finite element model of a cracked disk.

[0054] The said Step 2) includes the following steps:

[0055] First step, establish a geometric model of a cracked disk, please refer to Figure 2 ;

[0056] Second step, divide the above geometric model into finite element meshes, please refer to Figure 3 , and set the material properties and mesh properties;

[0057] Third step, set the analysis step type, boundary conditions, loads and output results to obtain the variation law of the maximum opening displacement of the disk crack.

[0058] For the boundary conditions of this example, the inner ring is fixed, the applied load is the centrifugal load, and the angular velocity varies in the range of 0 - 333 rad / s (corresponding to the rotational speed range of 0 - 20000 r / min), please refer to Figure 4 . Use hexahedral eight-node elements to perform finite mesh division on the disk. For the crack tip region with stress concentration phenomenon, mesh division is carried out by means of region segmentation and setting the number of seed points, and a denser mesh is obtained in the crack tip region, while in other regions of the disk, an appropriate mesh size is set by means of size control, and the overall mesh of the disk is relatively sparse, please refer to Figure 3 .

[0059] Under cyclic loading, a plastic zone will be generated at the crack tip. The key of the present invention lies in analyzing the influence of the plastic zone on the variation law of the maximum opening displacement of the crack. Therefore, the nonlinear problem of elastoplastic theory is introduced in the setting of material properties. For a fatigue crack under cyclic loading, plastic deformation will occur at the crack tip due to the stress concentration effect. Under cyclic loading, due to the repeated plastic deformation at the crack tip, the plastic flow characteristics of the material will change. In order to analyze the stress-strain relationship in the plastic zone, a combined kinematic hardening and isotropic hardening model is adopted in the elastoplastic analysis of the present invention. The isotropic part in the combined hardening model adopts the nonlinear isotropic hardening criterion of Voce:

[0060]

[0061] where: R is the isotropic hardening stress; σ ys is the initial yield stress; ε p is the plastic strain; Q ∞ and b are the coefficients in the equation.

[0062] The kinematic hardening part in the combined hardening model adopts the Chaboche nonlinear kinematic hardening model with three back stresses, and the calculation formula of the back stress is:

[0063] α = α 1 + α 2 + α 3 (2)

[0064] In the formula:

[0065]

[0066] The yield criterion is the condition for judging whether the material enters plastic yield. The general expression of the yield criterion considering combined hardening is:

[0067] f(σ - α) = σ eq (σ - α) - (σ ys + R) (4)

[0068] In the formula: f is the plastic potential; σ is the flow stress; σ eq is the equivalent stress.

[0069] The material selected for the example is A356.0, and its material parameters are shown in Table 1:

[0070] Table 1 Mechanical property parameters of A356.0

[0071]

[0072] Step 3), according to the cracked disk finite element model established in step 2), simulate the variation of the maximum crack opening displacement of the disk with the rotational speed. Please refer to Figure 5 . It can be found from the variation curve that the maximum crack opening displacement follows different variation laws during the acceleration and deceleration processes, and the acceleration curve and deceleration curve of the maximum crack opening displacement under cyclic load do not coincide. Taking the disk model with a 10-mm radial crack as an example, it is elaborated in detail.

[0073] Further analyze the relationship between the maximum crack opening displacement and the rotational speed, analyze the relationship between the change amount Δu of the maximum crack opening displacement and the change amount Δω of the rotational speed, and obtain the relationship between Δu and Δω at different maximum rotational speeds. Please refer to Figure 6 .

[0074] According to Figure 6 the variation law of Δu with Δω during the acceleration process in (a), establish a quadratic polynomial between Δu and Δω through polynomial fitting, and the functional relationship between Δu and Δω during the acceleration process that can be directly obtained is:

[0075] Δu = a 1 Δω 2 (5)

[0076] In the formula: a 1 is the correlation coefficient during the acceleration process.

[0077] During the deceleration process, the variation law of Δu with respect to Δω is different. Therefore, it is impossible to directly establish a functional relationship between Δu and Δω as in the acceleration process. Please refer to Figure 6 the data in (b) and process it. Convert the abscissa to Δω / ω max , and convert the ordinate to where ω max is the highest rotational speed of this cyclic load. Please refer to Figure 7 . Establish a quadratic polynomial of one variable with two parameters through polynomial fitting to obtain the functional relationship between the two variables.

[0078]

[0079] In the formula: a 2 and b 2 are the correlation coefficients for the deceleration process.

[0080] Through Equation (5) and Equation (6), the variation law of the maximum crack opening displacement under cyclic load can be established as:

[0081]

[0082] In the formula, u min is the maximum crack opening displacement at the start of acceleration; u max is the maximum crack opening displacement at the start of deceleration.

[0083] Step 4): The relationship between the maximum radial crack opening displacement and the rotational speed under cyclic load established in Step 3) is obtained under the condition that the crack length remains unchanged, etc., and its applicable range is limited. Therefore, it is also necessary to determine the applicable range of this expression and correct the established functional relationship according to the influence of the crack length and crack morphology (circumferential crack, radial crack).

[0084] a. Consider the influence of crack length:

[0085] The crack length is a key factor affecting the maximum crack opening displacement. Keeping parameters such as the crack position and width unchanged, with the highest rotational speed of the cyclic load being 20,000 r / min, during the mesh generation process, keep the mesh density distribution near the crack tip similar and only change the crack length parameter to analyze the influence of the crack length on the variation law of the maximum crack opening displacement under cyclic load.

[0086] By analyzing the simulation results, it can be found that whether it is the acceleration process or the deceleration process, the curves of the change in the maximum crack opening displacement under different crack lengths have a certain proportional relationship with the crack length; the curves of Δu / l with respect to Δω under different crack lengths approximately coincide. Therefore, the change in the maximum crack opening displacement is proportional to the crack length. Please refer to Figure 8 .

[0087] Therefore, the variation law of the maximum crack opening displacement obtained in step 3) can be generalized as follows:

[0088]

[0089] b. Consider the influence of crack morphology:

[0090] The radial cracks at the edge of the disk were discussed previously. However, the analysis method can be extended to the analysis of circumferential cracks. Similar to radial cracks, during the speed-up and speed-down processes, the variation of the maximum crack opening displacement with the rotational speed follows different laws for circumferential cracks. For the speed-up process, analyze the relationship between the change in the maximum crack opening displacement Δu and the change in the rotational speed Δω. For the speed-down process, analyze the variation law with respect to the change in Δω / ω max variation.

[0091] Establish the functional relationship between Δu and Δω during the speed-up and speed-down processes respectively through polynomial fitting.

[0092]

[0093] In the formula: a 3 、a 4 and b 4 are the correlation coefficients for the speed-up and speed-down processes.

[0094] Meanwhile, combining the conclusion that the change in the maximum crack opening displacement is proportional to the crack length, from Equation (9), the functional relationship of the maximum crack opening displacement of circumferential cracks with respect to the rotational speed can be obtained as:

[0095]

[0096] Step 5), according to the functional relationship of the corrected maximum crack opening displacement with respect to the rotational speed in step 4), in the form of the product of mass and radius, calculate the magnitude of the unbalanced force generated by the disk crack.

[0097] When cracks appear on the disk, as the rotational speed increases, both radial cracks and circumferential cracks open under the action of tensile stress, resulting in a partial mass loss at the crack position. By calculating the magnitude of the missing mass, the magnitude of the equivalent unbalance generated by the disk crack can be calculated. The shape of the radial crack is simplified to an isosceles triangle; the shape of the circumferential crack is more complex and can be simplified to an ellipse. Please refer to Figure 9 . Taking a uniform disk with a thickness of h rotating at an angular velocity w as an example, calculate the generation of radial cracks and circumferential cracks respectively.

[0098] a. Unbalanced force generated by radial cracks

[0099] There is a mass defect in the radial crack part. The shape of the radial crack is approximately an isosceles triangle. The mass of the missing part caused by the radial crack (the superscript r represents the radial crack) is:

[0100]

[0101] In the formula: u is the maximum opening displacement of the radial crack; l is the crack length; ρ is the material density.

[0102] The imbalance of the disk caused by the radial crack is calculated in the form of the product of mass and radius The magnitude of is:

[0103]

[0104] The unbalanced force of the disk caused by the radial crack can be obtained as:

[0105]

[0106] b. The unbalanced force caused by the circumferential crack

[0107] The deformation shape of the circumferential crack is an ellipse, and the area of the elliptical part is u is the maximum opening displacement of the circumferential crack, and l is the length of the circumferential crack. When the circumferential crack opens under the action of an external load, the mass of the missing part caused by the crack (the superscript h represents the circumferential crack) is:

[0108]

[0109] The mass missing part caused by the circumferential crack is located at the radius r of the disk. The magnitude of the disk imbalance caused by the radial crack is calculated in the form of the product of mass and radius as:

[0110]

[0111] The unbalanced force of the disk caused by the circumferential crack can be obtained as:

[0112]

[0113] Step 6): The unbalanced force of the disk caused by the crack calculated in step 5) is based on the simplified crack shape, while the actual crack shape is quite complex. Therefore, there is a certain deviation in the calculated result. According to the data obtained from the simulation in step 2), the calculation formula for the unbalanced force of the disk caused by the crack is corrected.

[0114] Under the influence of the crack, the overall centroid of the disk will shift. The magnitude of the imbalance of the disk caused by the crack is calculated by multiplying the mass of the disk by the centroid offset as:

[0115] U c = Me c (17)

[0116] In the formula: M is the total mass of the disk; e c is the centroid offset of the disk.

[0117] Taking the finite element model of a disk with a 10-mm radial crack as an example, simulations are carried out under cyclic loads (maximum rotational speed 20,000 r / min, minimum rotational speed 0 r / min), and the change in the centroid offset of the disk during the cycle is obtained through the simulations. The unbalance caused by the radial crack is calculated respectively by formula (12) and formula (17). Please refer to Figure 10 (a) in

[0118] Since the crack shape is simplified in the calculation process of formula (12), the calculated unbalance is greater than the result obtained by calculating through the centroid offset of the disk. Formula (12) is corrected by a proportionality coefficient to obtain the following formula:

[0119]

[0120] For a comparison of the corrected calculation results, please refer to Figure 10 (b) in

[0121]

[0122] The same analysis method can be applied to the analysis of circumferential cracks. The unbalance force of the disk caused by the corrected circumferential crack is:

[0123]

[0124] In summary, since the present invention takes into account the plastic deformation generated at the crack tip of the disk under fatigue loads, is based on the relevant theories of elastic-plastic fracture mechanics, and takes into account the influence of factors such as crack length and crack shape (circumferential crack, radial crack), the obtained law is more in line with the actual working conditions, the calculation results are more accurate, and a more accurate analysis method is provided for the research on the failure mechanism of disk cracks. The method of the present invention can be used to accurately solve the unbalance force caused by disk cracks; the method of the present invention lays a theoretical foundation for disk crack detection.

[0125] Based on the concept described in the present invention, a calculation system for the unbalance force caused by disk cracks in an aeroengine is further provided, including a parameter acquisition module, a model construction module, a first calculation module, a first correction module, a second calculation module, and a second correction module;

[0126] The parameter acquisition module is used to acquire the attribute parameters of the disk and disk cracks of the aircraft engine;

[0127] The model construction module is used for the nonlinear numerical simulation analysis software Abaqus to establish a finite element model of the cracked disk. Specifically, a cyclic loading method is adopted to simulate the low-cycle fatigue process of the disk, and each cycle includes three stages: loading - holding - unloading;

[0128] The first calculation module is used to simulate and analyze the variation law of the maximum crack opening displacement at different maximum rotational speeds based on the finite element model of the cracked disk, and establish a functional relationship between the maximum crack opening displacement and the rotational speed under cyclic loading;

[0129] The first correction module is used to analyze the influence of the crack length and crack morphology on the variation law of the maximum crack opening displacement of the disk crack under cyclic loading according to the functional relationship obtained by the first calculation module, and correct the functional relationship between the maximum crack opening displacement and the rotational speed;

[0130] The second calculation module simplifies the crack opening shape according to the functional relationship between the maximum crack opening displacement and the rotational speed corrected by the first modification module, and calculates through the form of the product of mass and radius to establish an unbalanced force calculation model caused by the disk crack;

[0131] The second correction module simulates and analyzes the change value of the centroid offset of the disk according to the finite element model of the cracked disk, calculates the magnitude of the unbalance through the change value of the centroid offset, and corrects the unbalanced force calculation model obtained by the second calculation module to obtain the unbalanced force caused by the disk crack.

[0132] Optionally, the present invention also provides a computer device, including a processor and a memory. The memory is used to store computer-executable programs. The processor reads part or all of the computer-executable programs from the memory and executes them. When the processor executes part or all of the computer-executable programs, it can implement the calculation method described in the present invention.

[0133] A program capable of executing the method described in the present application can be written in a computer programming language. The computer program can be in the form of source code, object code, executable file or some intermediate form. The computer programming language can be C++, Java, Fortran, C# or Python.

[0134] The computer device described above can be a laptop computer, a tablet computer, a desktop computer, a mobile phone or a workstation.

[0135] The processor can be a central processing unit (CPU), a digital signal processor (DSP), an application specific integrated circuit (ASIC) or a field programmable gate array (FPGA).

[0136] For the memory described in the present invention, it can be an internal storage unit of a laptop, a tablet computer, a desktop computer, a mobile phone or a workstation, such as a memory or a hard disk; or an external storage unit can be adopted, such as a mobile hard disk or a flash card.

[0137] A computer-readable storage medium may include a computer storage medium and a communication medium. The computer storage medium includes volatile and non-volatile, removable and non-removable media implemented by any method or technology for storing information such as computer-readable instructions, data structures, program modules or other data. The computer-readable storage medium may include: read-only memory (ROM, Read Only Memory), random access memory (RAM, Random Access Memory), solid state drives (SSD, Solid State Drives) or optical discs, etc. Among them, the random access memory may include resistive random access memory (ReRAM, Resistance).

[0138] In addition, the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art can still modify the specific implementation manners of the present invention or make equivalent replacements. Any such modifications or equivalent replacements that do not depart from the spirit and scope of the present invention are within the scope of the claims of the present invention pending approval.

Claims

1. A calculation method for the unbalanced force caused by cracks in an aero-engine disk, characterized in that, it includes the following steps: S1. Collect the attribute parameters of the disk and the cracks in the disk of the aero-engine; S2. Based on the non-linear numerical simulation analysis software, establish a finite element model of the cracked disk. Specifically, the cyclic loading method is adopted to simulate the low cycle fatigue process of the disk. Each cycle includes three stages: loading - holding - unloading; S3. Based on the finite element model of the cracked disk established in S2, simulate and analyze the variation law of the maximum crack opening displacement at different maximum rotational speeds, and establish the functional relationship between the maximum crack opening displacement and the rotational speed under cyclic load; specifically, conduct finite element simulation on the relationship between the maximum crack opening displacement and the rotational speed under cyclic load, and obtain the conclusion that the maximum crack opening displacement under cyclic load follows different variation laws during the acceleration and deceleration processes. Utilize the change amount of the maximum crack opening displacement and the change amount of the rotational speed, and solve the functional relationship between the maximum crack opening displacement and the rotational speed by quadratic function fitting; During the speed-up process, a quadratic polynomial between and is established by polynomial fitting; during the speed-down process, when establishing a quadratic polynomial of two parameters by polynomial fitting, the variables are transformed; finally, the functional relationship between the two variables is obtained: In the formula, is the maximum crack opening displacement at the start of speed increase; is the maximum crack opening displacement at the start of speed decrease; S4. According to the functional relationship obtained in S3, analyze the influence of the crack length and crack morphology on the variation law of the maximum opening displacement of the disk crack under cyclic load, and correct the functional relationship between the maximum opening displacement of the crack and the rotational speed; S5. According to the corrected functional relationship between the maximum opening displacement of the crack and the rotational speed obtained in S4, simplify the crack opening shape, calculate through the form of the product of mass and radius, and establish a calculation model for the unbalanced force caused by the disk crack; S6. According to the finite element model of the cracked disk established in S2, through simulation analysis, obtain the change value of the centroid offset of the disk, calculate the magnitude of the unbalance through the change value of the centroid offset, and correct the calculation model for the unbalanced force caused by the disk crack established in S5 to obtain the unbalanced force caused by the disk crack.

2. The calculation method for the unbalanced force caused by cracks in an aero-engine disk according to claim 1, characterized in that, in S1, the attribute parameters of the disk of the aero-engine include: geometric dimension parameters and material property parameters; the attribute parameters of the disk crack include: crack morphology and crack length, and the crack morphology includes circumferential cracks and radial cracks.

3. The calculation method for the unbalanced force caused by cracks in an aero-engine disk according to claim 1, characterized in that, in S2, the steps for establishing a finite element model of the cracked disk include: S2.

1. Establish a geometric model of the cracked disk; S2.

2. Divide the finite element mesh for the geometric model, set the material properties, mesh type, analysis step type, boundary conditions, loads and output results to establish a finite element model of the cracked disk; the material properties, boundary conditions and loads are determined with reference to the actual working conditions of the engine; the output result refers to the maximum opening displacement of the crack in the finite element model.

4. The calculation method for the unbalanced force caused by cracks in an aero-engine disk according to claim 3, characterized in that, in S2.2, use hexahedral eight-node elements to perform finite mesh division on the disk. For the crack tip region with stress concentration, perform mesh division by means of region segmentation and setting the number of seed points. In other regions of the disk, set an appropriate mesh size by means of size control; the mesh density in the crack tip region is greater than that in other regions.

5. The calculation method for the unbalanced force caused by cracks in an aero-engine disk according to claim 3, characterized in that, In S2.2, the material property setting introduces the nonlinear factors of elastoplastic theory. When analyzing the stress-strain relationship in the plastic zone, a combined kinematic hardening and isotropic hardening model is adopted. For the isotropic part in the combined hardening model, the nonlinear isotropic hardening criterion of Voce is used. For the kinematic hardening part in the combined hardening model, the Chaboche nonlinear kinematic hardening model with three back stresses is used.

6. A method for calculating the unbalanced force caused by a crack in an aero-engine disk according to claim 1, characterized in that, in S4, the influence of the crack length is considered: the crack length is changed to analyze the influence of the crack length on the variation law of the maximum opening displacement of the crack under cyclic loading, and it is obtained that the variation of the maximum opening displacement of the crack is proportional to the crack length; Consider the influence of crack morphology: The circumferential crack is the same as the radial crack. For the speed-up process, analyze the change in the maximum opening displacement of the crack and the change in rotational speed relationship; For the speed-down process, analyze with The change law of the change with respect to the change, and then obtain the functional relationship between the maximum opening displacement of the circumferential crack and the rotational speed: Among them, l is the crack length, , and are the correlation coefficients related to the acceleration and deceleration processes.

7. A method for calculating the unbalanced force caused by a crack in an aero-engine disk according to claim 1, characterized in that, in S5, the equivalent unbalance amount caused by the disk crack is calculated by calculating the size of the missing mass. The shape of the radial crack is simplified to an isosceles triangle to calculate the mass of the missing part caused by the crack, and the shape of the circumferential crack is simplified to an ellipse to calculate the mass of the missing part caused by the crack.

8. A calculation system for the unbalanced force caused by a crack in an aero-engine disk, characterized in that, it includes a parameter acquisition module, a model construction module, a first calculation module, a first correction module, a second calculation module and a second correction module; The parameter acquisition module is used to acquire the attribute parameters of the disk and the disk crack of the aero-engine; The model construction module is used to establish a finite element model of the cracked disk based on the nonlinear numerical simulation analysis software. Specifically, the cyclic loading method is adopted to simulate the low cycle fatigue process of the disk. Each cycle includes three stages: loading - holding - unloading; The first calculation module is used to simulate and analyze the variation law of the maximum crack opening displacement at different maximum rotational speeds based on the finite element model of the cracked disk, and establish the functional relationship between the maximum crack opening displacement and the rotational speed under cyclic load; specifically, it includes performing finite element simulation on the relationship between the maximum crack opening displacement and the rotational speed under cyclic load, obtaining the conclusion that the maximum crack opening displacement under cyclic load follows different variation laws during the acceleration and deceleration processes, and using the change amount of the rotational speed to solve the functional relationship between the maximum crack opening displacement and the rotational speed by quadratic function fitting; During the speed-up process, a quadratic polynomial between and is established by polynomial fitting; during the speed-down process, when establishing a quadratic polynomial of two parameters by polynomial fitting, the variables are transformed; finally, the functional relationship between the two variables is obtained: In the formula, is the maximum crack opening displacement at the start of speed increase; is the maximum crack opening displacement at the start of speed decrease; The first correction module is used to analyze the influence of the crack length and crack morphology on the variation law of the maximum opening displacement of the disk crack under cyclic loading according to the function relationship obtained by the first calculation module, and correct the function relationship between the maximum opening displacement of the crack and the rotational speed; The second calculation module simplifies the crack opening shape according to the function relationship between the maximum opening displacement of the crack varying with the rotational speed corrected by the first modification module, and calculates through the form of the product of mass and radius, and establishes a calculation model for the unbalanced force caused by the disk crack; The second correction module simulates and analyzes the change value of the centroid offset of the disk according to the finite element model of the cracked disk, calculates the size of the unbalance amount through the change value of the centroid offset, corrects the unbalanced force calculation model obtained by the second calculation module, and obtains the unbalanced force caused by the disk crack.

9. A computer device, characterized in that, it includes a processor and a memory. The memory is used to store computer-executable programs. The processor reads the computer-executable programs from the memory and executes them. When the processor executes the computer-executable programs, it can implement the method for calculating the unbalanced force caused by the crack in the aero-engine disk according to any one of claims 1 to 7.

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