Aviation wheel fatigue life analysis method

Abstract

The invention discloses an aviation airplane wheel fatigue life analysis method, and belongs to the technical field of airplane structural part fatigue life finite element analysis. The method comprises the following steps: constructing an airplane wheel numerical model based on entity structure parameters of an airplane wheel; the airplane wheel numerical model is simplified; stress spectrum calculation is conducted on the airplane wheel numerical model through finite element software, and stress values of all nodes on the airplane wheel are obtained when the airplane wheel rolls by one circle under the fatigue load spectrum; based on the symmetry characteristic of the airplane wheel, the number of rolling turns, namely the number of cycles, of the airplane wheel in one take-off and landing life period under different working conditions is obtained; and evaluating the fatigue life of the airplane wheel based on the cycle times under different working conditions. The problems that an existing method is high in calculation cost and cannot accurately guide calculation and analysis of the fatigue life of the aviation aircraft wheel are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of finite element analysis of fatigue life of aircraft structural parts, and in particular relates to a method for analyzing fatigue life of aircraft wheels. Background Art

[0002] With the development of aircraft wheel design technology and the improvement of aircraft wheel material level, the life of aircraft wheels is required to be longer and longer. At present, the life of civil aircraft wheels has reached more than 10,000 take-offs and landings. It is increasingly necessary to estimate the life in the product design stage. In recent years, fatigue cracks have occasionally occurred in aircraft wheels in service in the field. The previous calculation methods with poor accuracy, long cycle and low efficiency have gradually failed to meet the urgency of model development. Therefore, it is increasingly necessary to seek a life estimation method with relatively accurate calculation accuracy and fast calculation method.

[0003] With the continuous development of computer technology and finite element analysis software (CAE software), it is possible to use CAE software to replace traditional theoretical calculations. Since CAE software can simulate the structure and load conditions of the wheel more completely and realistically, it is possible to calculate the wheel stress spectrum. Compared with the traditional empirical method to determine the wheel stress obtained by the dangerous section, the result is more reliable. In addition, based on the calculated stress spectrum, combined with the life analysis software (CAF software), the life size of all positions of the entire wheel can also be obtained. Fe-Safe software is an advanced fatigue durability analysis and signal processing software. It is recognized as the world's most accurate fatigue analysis software. In our company, Fe-Safe software has been successfully used for many years in the fatigue life estimation of aircraft wheels.

[0004] The theoretical basis of the wheel fatigue life analysis method based on Abaqus and fe-safe software for the estimation of the life of our company's aircraft wheels is Miner's linear damage theory. The biggest problem with this method is that the accuracy of the stress spectrum is related to the number of nodes and the mesh density. The larger the mesh density, the closer it is to the true value, but the corresponding calculation cost is higher. It is impossible to accurately guide the calculation and analysis of the fatigue life of aircraft wheels, and thus it is impossible to achieve the design of long-life aircraft wheels. Summary of the invention

[0005] Technical issues to be solved:

[0006] In order to avoid the shortcomings of the prior art, the present invention provides an aircraft wheel fatigue life analysis method. On the basis of the existing wheel fatigue life estimation method, combined with the axisymmetric characteristics of the wheel, the Fe-Safe software Rotate module is used to estimate the life of the wheel single-point loading stress data, and compared with the cyclic loading method. The results show that the method of the present invention greatly improves the efficiency and accuracy of aircraft wheel fatigue estimation. Therefore, the present invention solves the problems that the existing method has a high calculation cost and cannot accurately guide the calculation and analysis of aircraft wheel fatigue life.

[0007] The technical solution of the present invention is: a method for analyzing the fatigue life of an aircraft wheel, the specific steps of which are as follows:

[0008] Based on the physical structural parameters of the wheel, a numerical model of the wheel is constructed;

[0009] Simplifying the numerical model of the wheel;

[0010] The stress spectrum of the wheel numerical model is calculated by finite element software to obtain the stress value of each node on the wheel when the wheel rolls one circle under the fatigue load spectrum.

[0011] Based on the symmetry of the wheel, the number of rolling circles of the wheel in a take-off and landing life cycle under different working conditions, that is, the number of cycles, is obtained;

[0012] The wheel fatigue life is evaluated based on the number of cycles under different working conditions.

[0013] A further technical solution of the present invention is: the method for constructing a numerical model of a wheel is to firstly design a three-dimensional model of the wheel using three-dimensional modeling software, and then import the three-dimensional model of the wheel into finite element software for calculation to obtain a numerical model of the wheel.

[0014] A further technical solution of the present invention is: the method for simplifying the numerical model of the wheel is to delete the parts with large stress concentration in the numerical model of the wheel, and the parts with large stress concentration include fillets, chamfers and small holes.

[0015] A further technical solution of the present invention is: the stress spectrum calculation is to use finite element software to perform static stress calculation of the wheel numerical model:

[0016] Setting the load, setting the load module of the finite element software according to the actual fatigue load of the wheel, and applying the set load to the numerical model of the wheel;

[0017] Set boundary conditions to constrain the six degrees of freedom of the wheel numerical model in the X, Y, and Z directions, keeping it immobile;

[0018] The fatigue load spectrum is set, and the numerical model of the wheel is divided into M positions along the circumferential direction. When setting the load, a rigid plate is established as a virtual ground, and the rigid plate is rotated 1 / M degrees each time to load the tire of the numerical model of the wheel. When loading, the load remains unchanged, and the loading angle changes from 0-2π, and the loading direction of the load also changes accordingly, ensuring that the load is loaded once at each of the M array blocks, thereby simulating the load effect of a wheel rolling one circle.

[0019] A new job is established in the finite element software, and the calculation is performed using the numerical model of the wheel as the data source to obtain the stress value of each node on the wheel when the wheel rolls one circle under the fatigue load spectrum.

[0020] A further technical solution of the present invention is: the method for obtaining the number of cycles is:

[0021] The FE-safe / Rotate module is used to import the stress value of each node on the wheel when the wheel rolls one circle under the fatigue load spectrum, and the symmetric characteristic parameters of the wheel numerical model are set in the load module;

[0022] In Fe-safe, the stress result of the i-th working condition 1-N is defined as a cycle, and the number of rolling circles within the next take-off and landing life under the corresponding load is defined as the number of cycles.

[0023] A further technical solution of the present invention is: the method for evaluating the fatigue life of the wheel is:

[0024] The total damage degree at the dangerous section of the wheel under a certain working condition is calculated as follows:

[0025]

[0026] Where: N i N is the number of cycles of various stress values ​​appearing at the dangerous section of the wheel under the load of the i-th working condition during a take-off and landing life, that is, the number of rolling circles under the corresponding load during a take-off and landing life; oi is the number of cycles corresponding to each stress value on the SN curve of the material at the critical section of the wheel;

[0027] The total damage degree to the dangerous section of the wheel under all working conditions is calculated as:

[0028]

[0029] Where: n represents the number of different stress values ​​appearing at the dangerous section of the wheel within a life cycle under this load state.

[0030] During a take-off and landing life, the fatigue life estimation formula of the wheel is as follows:

[0031]

[0032] Where: N p Indicates the safe life of the wheel; T means one takeoff and landing; S F Represents the wheel design fatigue dispersion coefficient.

[0033] A further technical solution of the present invention is: F The value is 4.

[0034] Beneficial Effects

[0035] The beneficial effect of the present invention is that the present invention adopts a single-point loading fatigue estimation method based on Abaqus and fe-safe software, which can greatly improve the efficiency and accuracy of aircraft wheel fatigue estimation. On the one hand, in the early stage of product design, the fatigue life analysis of aircraft wheels can be carried out by finite element analysis, the weak points of the wheel structure can be determined, and the aircraft wheels can be improved and corresponding structural optimization measures can be taken before the test, thereby improving the development cycle; on the other hand, the results can be predicted before the product test, reducing the economic losses caused by test failures and shortening the cycle of repeated tests. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of cyclic loading load of the present invention;

[0037] Figure 2 It is a schematic diagram of cyclic loading stress of the present invention;

[0038] Figure 3 It is a schematic diagram of the change of stress with time in the present invention;

[0039] Figure 4 It is a schematic diagram of the life distribution obtained by cyclic loading of the complete model of the present invention. DETAILED DESCRIPTION

[0040] The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0041] When evaluating the life of an aircraft wheel based on the wheel fatigue life analysis method, the accuracy of the stress spectrum is related to the number of nodes and the grid density. The larger the grid density, the closer it is to the true value, but the corresponding calculation cost is higher. The present invention provides an aircraft wheel fatigue life analysis method, and the specific steps are as follows:

[0042] Step 1: Construct a numerical model of the wheel based on the physical structural parameters of the wheel;

[0043] Step 2: Simplify the numerical model of the wheel;

[0044] Step 3: Calculate the stress spectrum of the wheel numerical model using finite element software to obtain the stress value of each node on the wheel when the wheel rolls one circle under the fatigue load spectrum;

[0045] Step 4: Based on the symmetric characteristics of the wheel, the number of rolling circles of the wheel in a take-off and landing life cycle under different working conditions, that is, the number of cycles, is obtained;

[0046] Step 5: Perform wheel fatigue life assessment based on the number of cycles under different operating conditions.

[0047] The present invention discloses a novel aircraft wheel fatigue life analysis method, which is used to carry out aircraft wheel fatigue life analysis, establish a complete wheel model, and then perform 360° cyclic loading on the wheel by manual / automatic methods to avoid cracks or fatigue problems in aircraft wheel structural parts caused by fatigue life analysis problems.

[0048] The above technical solution is further described below with reference to the accompanying drawings and examples:

[0049] This embodiment provides a novel aircraft wheel fatigue life analysis method, which is a wheel cyclic fatigue life estimation method based on Abaqus and fe-safe software. The specific steps are as follows:

[0050] Step 1: Create a 3D solid model

[0051] CATIA 3D modeling software is used according to the actual size of the wheel. For a single-web wheel assembly, the main components of the wheel are composed of a hub, a rim and a half retaining ring, and the hub generally has 9 lightening holes. Since the overall structure of the wheel assembly is a circular array structure, the wheel assembly is divided into M equal parts, and a 3D wheel model is established in ABAQUS to obtain a 3D solid model of the wheel.

[0052] Step 2: Simplify the 3D solid model

[0053] When the established three-dimensional solid model of the wheel has areas with large stress concentration such as fillets, chamfers and small holes, the three-dimensional solid model is simplified. The specific simplification operation is: deleting the fillets, chamfers and small holes in the three-dimensional solid model.

[0054] When the three-dimensional solid model is included in the simulation software calculation, the presence of large stress concentration areas such as fillets, chamfers and small holes will result in a large amount of calculation, and even the fatigue life calculation cannot be realized. Therefore, the three-dimensional solid model needs to be simplified to reduce the amount of calculation while ensuring the accuracy of the calculation results.

[0055] When the established three-dimensional solid model of the wheel does not have areas with large stress concentration such as fillets, chamfers and small holes, go directly to the next step.

[0056] At this point, a simplified three-dimensional solid model of the wheel structure is obtained.

[0057] Step 3: Stress spectrum calculation

[0058] The stress spectrum calculation is to use Abaqus software to perform static stress calculation of the aircraft wheel model. The simplified three-dimensional solid model and the unsimplified three-dimensional solid model are imported into the ABAQUS finite element analysis software, and the real fatigue load spectrum of the wheel structure is applied to the simplified three-dimensional solid model through the ABAQUS software LOAD module.

[0059] The so-called boundary conditions during calculation are applied through the ABAQUS software LOAD module to eliminate various degrees of freedom to facilitate calculation. In this embodiment, the reference points of the two bearings are fixed to simulate the fixation of the landing gear shaft to the bearings during the actual loading process, eliminating 6 degrees of freedom of the finite element model of the wheel assembly to ensure the convergence of the finite element model of the wheel assembly.

[0060] The so-called fatigue load spectrum setting refers to the cyclic loading fatigue algorithm, which mainly divides the model into M positions in the circumferential direction. When setting the load, a rigid plate is established as a virtual ground, and the load is loaded on the tire of the aircraft wheel at 1 / M degrees of rotation of the ground each time. When loading, the load size remains unchanged, the loading angle changes from 0-2π, and the loading direction of the load also changes accordingly, ensuring that the load is loaded once at each array block, thereby simulating the load effect of a wheel rolling one circle.

[0061] Create a new job through the job module of ABAQUS finite element software, and use the simplified three-dimensional solid model finite element model of the aircraft wheel as the calculation data source. Submit the simplified three-dimensional finite element model of the aircraft wheel for calculation. After the calculation is completed, it is convenient to obtain the stress size of each node on the aircraft wheel when the aircraft wheel rolls one circle under the fatigue load spectrum.

[0062] Step 4: Number of cycles under different working conditions

[0063] The life estimation is a post-processing of static stress calculation using Fe-safe software. In Fe-safe software, the wheel is subjected to cyclic load loading over a time history according to the use condition of one rotation, and the final life result of the aircraft wheel is obtained. It is mainly divided into the following steps:

[0064] 1) Import .odb file;

[0065] Use the FE-safe / Rotate module to import the stress calculation results in step 3, and set the symmetry characteristic parameters of the three-dimensional simplified wheel model in the ABAQUS software LOAD module.

[0066] 2) Life analysis: Read in the time history set in the analysis step of step 3 stress spectrum calculation.

[0067] In Fe-safe, the stress result of the i-th working condition 1-N read from the Abaqus results is defined as a cycle, and the number of rolling circles of a take-off and landing under the corresponding load is defined as the number of cycles.

[0068] Step 5: Wheel Fatigue Life Assessment

[0069] According to the number of cycles under different working conditions in step 4, calculate the wheel fatigue damage degree. The so-called wheel fatigue damage degree refers to the fatigue damage caused to the wheel by different loads acting on the wheel. The calculation formula is:

[0070]

[0071] Where: N i is the number of cycles of various stress values ​​appearing at the dangerous section of the wheel under the load of the i-th working condition during a service life (generally refers to a take-off and landing of the aircraft);

[0072] N oi It is the number of cycles corresponding to each stress value on the SN curve of the material at the critical section of the wheel. The SN curve is a curve that uses the fatigue strength of the standard specimen of the material as the ordinate and the logarithm of the fatigue life lg N as the abscissa to represent the relationship between the fatigue strength and fatigue life of the standard specimen under certain cycle characteristics, also known as the stress-life curve

[0073] Therefore, the total damage degree to the dangerous section of the wheel under this load spectrum state is:

[0074]

[0075] Where: n represents the number of different stress values ​​appearing at the dangerous section of the wheel within a life cycle under this load state.

[0076] When the aircraft takes off and lands, the wheels are subjected to loads of different magnitudes. Therefore, the fatigue life estimation formula of the wheels within a service life is:

[0077]

[0078] Where: N p The safe life of the wheel;

[0079] T is one take-off and landing;

[0080] S F is the wheel design fatigue dispersion coefficient, which is generally taken as 4;

[0081] D i is the total damage degree at the dangerous section of the wheel under a certain load;

[0082] n represents the number of different stress values ​​appearing at the dangerous section of the wheel within a life cycle under this load condition.

[0083] Embodiment 1: A three-dimensional solid model of an aircraft wheel and a three-dimensional simplified finite element model of an aircraft wheel are obtained through steps 1 and 2. According to the stress spectrum obtained in step 3, the calculation result of step 3 is brought into step 4 to obtain the number of cycles of the three-dimensional simplified model of the wheel under different working conditions of the stress load spectrum; finally, through step 5, the fatigue life is obtained to be 2800 landings; after the factory test, it is known that the fatigue life of the aircraft wheel is 2950 landings. The error between the finite element simulation analysis result of the fatigue life of an aircraft wheel carried out by this aircraft wheel fatigue life analysis method and the factory fatigue test result is 10.2%. The small error proves the applicability, accuracy and reliability of the aircraft wheel fatigue life calculation method, and provides a new method for calculating the fatigue life of an aircraft wheel.

[0084] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and intent of the present invention.

Claims

1. A method for analyzing the fatigue life of an aircraft wheel, characterized in that The specific steps are as follows: Based on the physical structural parameters of the wheel, a numerical model of the wheel is constructed; Simplifying the numerical model of the wheel; The stress spectrum of the wheel numerical model is calculated by finite element software to obtain the stress value of each node on the wheel when the wheel rolls one circle under the fatigue load spectrum. Based on the symmetry of the wheel, the number of rolling circles of the wheel in a take-off and landing life cycle under different working conditions, that is, the number of cycles, is obtained; The wheel fatigue life is evaluated based on the number of cycles under different working conditions.

2. The method for analyzing the fatigue life of an aircraft wheel according to claim 1, characterized in that: The method for constructing the numerical model of the wheel is to firstly design the three-dimensional model of the wheel using three-dimensional modeling software, and then import the three-dimensional model of the wheel into finite element software for calculation to obtain the numerical model of the wheel.

3. The method for analyzing fatigue life of an aircraft wheel according to claim 2, characterized in that: The method for simplifying the numerical model of the wheel is to delete the parts with large stress concentration in the numerical model of the wheel, and the parts with large stress concentration include fillets, chamfers and small holes.

4. The method for analyzing fatigue life of an aircraft wheel according to claim 1, characterized in that: The stress spectrum calculation is to use finite element software to perform static stress calculation of the wheel numerical model: Setting the load, setting the load module of the finite element software according to the actual fatigue load of the wheel, and applying the set load to the numerical model of the wheel; Set boundary conditions to constrain the six degrees of freedom of the wheel numerical model in the X, Y, and Z directions, keeping it immobile; The fatigue load spectrum is set, and the numerical model of the wheel is divided into M positions along the circumferential direction. When setting the load, a rigid plate is established as a virtual ground, and the rigid plate is rotated 1 / M degrees each time to load the tire of the numerical model of the wheel. When loading, the load remains unchanged, and the loading angle changes from 0-2π, and the loading direction of the load also changes accordingly, ensuring that the load is loaded once at each of the M array blocks, thereby simulating the load effect of a wheel rolling one circle. A new job is established in the finite element software, and the calculation is performed using the numerical model of the wheel as the data source to obtain the stress value of each node on the wheel when the wheel rolls one circle under the fatigue load spectrum.

5. The method for analyzing aircraft wheel fatigue life according to claim 4, characterized in that: The method for obtaining the number of cycles is: The FE-safe / Rotate module is used to import the stress value of each node on the wheel when the wheel rolls one circle under the fatigue load spectrum, and the symmetric characteristic parameters of the wheel numerical model are set in the load module; In Fe-safe, the stress result of the i-th working condition 1-N is defined as a cycle, and the number of rolling circles within the next take-off and landing life under the corresponding load is defined as the number of cycles.

6. The method for analyzing aircraft wheel fatigue life according to claim 5, characterized in that: The method for evaluating the wheel fatigue life is: The total damage degree at the dangerous section of the wheel under a certain working condition is calculated as follows: Where: N i N is the number of cycles of various stress values ​​appearing at the dangerous section of the wheel under the load of the i-th working condition during a take-off and landing life, that is, the number of rolling circles under the corresponding load during a take-off and landing life; oi is the number of cycles corresponding to each stress value on the SN curve of the material at the critical section of the wheel; The total damage degree to the dangerous section of the wheel under all working conditions is calculated as: Where: n represents the number of different stress values ​​appearing at the dangerous section of the wheel within a life cycle under this load state. During a take-off and landing life, the fatigue life estimation formula of the wheel is as follows: Where: N p Indicates the safe life of the wheel; T means one takeoff and landing; S F Represents the wheel design fatigue dispersion coefficient.

7. The method for analyzing aircraft wheel fatigue life according to claim 6, characterized in that: The S F The value is 4.

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