CN114925559B - Method for evaluating residual bearing capacity of helicopter tail transmission shaft after breakdown - Google Patents
Method for evaluating residual bearing capacity of helicopter tail transmission shaft after breakdown Download PDFInfo
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Abstract
The application discloses a method for evaluating residual bearing capacity of a helicopter tail transmission shaft after the helicopter tail transmission shaft is punctured, which comprises the following steps: step 1, carrying out penetration dynamics analysis on a tail transmission shaft punctured by a small object by adopting penetration dynamics, and establishing a penetration-torsion buckling integrated model; step 2, performing critical torsional buckling analysis on the penetration-torsional buckling integrated model by adopting a finite element linear eigenvalue analysis method, and calculating a first-order instability mode of the tail transmission shaft; and 3, multiplying the first-order instability mode by a proportionality coefficient, coupling and binding nodes on two end faces of the tail transmission shaft with the circle centers of the two end faces respectively by adopting a nonlinear post-buckling analysis method, applying a displacement load on the circle center of the free end of the tail transmission shaft, calculating a load-displacement curve, and recording the load corresponding to the peak value in the load-displacement curve as the predicted failure load of the tail transmission shaft. Through the technical scheme in the application, the accuracy of failure load evaluation after the helicopter tail transmission shaft is punctured is improved.
Description
Technical Field
The application relates to the technical field of helicopter transmission systems, in particular to a method for evaluating residual bearing capacity of a helicopter tail transmission shaft after the helicopter tail transmission shaft is punctured.
Background
The helicopter may be hit by flying birds, stones, bullets and other objects in the air during the flight process, and particularly, the tail transmission shaft in the transmission system of the helicopter can cause the falling of the helicopter and the casualties of people if the tail transmission shaft is damaged and failed after being hit. In order to ensure that the helicopter tail transmission shaft still has enough mechanical strength after being hit by an object, the helicopter tail transmission shaft needs to be analyzed for residual bearing capacity urgently. Because the helicopter tail transmission shaft is mainly under the action of torsional load in the running process and has the characteristic of being long and thin due to the shape, the failure mode of the helicopter tail transmission shaft is mainly represented as torsional buckling failure.
At present, although a plurality of researches are carried out on the torsional buckling of a key structural part of a helicopter, the torsional buckling analysis of a tail transmission shaft after a small object is hit is not reported. After a small object hits and damages a tail transmission shaft of the helicopter, the torsional buckling of the small object is actually subjected to penetration-torsional buckling integrated analysis, and the small object has special difficulty compared with other types of penetration damages.
Firstly, after a small object hits and damages a tail transmission shaft of a helicopter, a three-dimensional finite element model similar to the actual working condition needs to be established by torsional buckling finite element analysis, particularly a grid model of a local damage area needs to be kept highly consistent with the actual damage working condition. However, after the tail transmission shaft is hit, damage conditions such as curling and warping easily occur in a local area around a damaged hole, a three-dimensional model similar to the actual condition is difficult to directly establish through finite element software, and the three-dimensional model is obtained through penetration dynamic simulation calculation and optimization;
secondly, after the tail transmission shaft is hit by a small object, a large amount of distortion and failure grids are generated around the damaged hole after dynamic simulation, and finite element software buckling analysis cannot be directly carried out;
thirdly, after the tail transmission shaft is hit by a small object, the requirements on the quality of grids in the penetration process are very high, and the grids which are locally encrypted are required to be adapted to penetration and torsional buckling analysis;
finally, the critical point of the tail transmission shaft, where the nonlinear buckling failure occurs, cannot be directly obtained and needs to be indirectly derived through an image method, and the position of the inflection point is difficult to determine.
Therefore, the analysis of the remaining bearing capacity of the helicopter tail drive shaft after being hit and damaged by a small object is substantially very difficult.
Disclosure of Invention
The purpose of this application lies in: how to analyze the residual bearing capacity of the helicopter tail transmission shaft after being hit and damaged by a small object ensures that the tail transmission shaft can still bear larger torsional load after breakdown so as to improve the safety performance of the helicopter.
The technical scheme of the application is as follows: the method for evaluating the residual bearing capacity of the helicopter tail transmission shaft after being punctured is provided, and comprises the following steps: step 1, carrying out penetration dynamics analysis on a tail transmission shaft which is punctured by a small object by adopting penetration dynamics, and establishing a penetration-torsion buckling integrated model; step 2, performing critical torsional buckling analysis on the penetration-torsional buckling integrated model by adopting a finite element linear characteristic value analysis method, and calculating a first-order instability mode of the tail transmission shaft; and 3, multiplying the first-order instability mode by a proportionality coefficient, coupling and binding nodes on two end faces of the tail transmission shaft with the centers of the two end faces respectively by adopting a nonlinear post-buckling analysis method, applying a displacement load on the center of the free end of the tail transmission shaft, calculating a load-displacement curve, and recording a load corresponding to a peak value in the load-displacement curve as a predicted failure load of the tail transmission shaft, wherein two ends of the tail transmission shaft are respectively a free end and a fixed end.
In any one of the above technical solutions, further, in step 1, the method specifically includes: step 11, carrying out numerical simulation calculation on a small object hitting penetration process of the tail transmission shaft by adopting penetration dynamics, and calculating damage of the small object penetration to the tail transmission shaft, wherein in the numerical simulation calculation process, firstly, first grid division is carried out on the punctured tail transmission shaft, a grid encryption area is determined by taking the incident position of the small object as the center and taking the preset length as the radius, and then, second grid division is carried out on the grid encryption area; step 12, determining a finite element model for hitting the damaged tail transmission shaft according to the calculated damage of the tail transmission shaft; and step 13, carrying out grid screening on the finite element model, deleting abnormal grids, and recording the screened finite element model as an invasion-torsion buckling integrated model.
In any of the above technical solutions, further, the abnormal mesh at least includes a discrete mesh, an interference mesh and a distortion mesh, where a mesh with a mesh aspect ratio greater than a distortion threshold is denoted as a distortion mesh, and a value of the distortion threshold is 5.
In any of the above technical solutions, further, before step 2, the method includes: defining boundary conditions of the penetration-torsional buckling integrated model, and coupling and binding nodes on two end faces of a tail transmission shaft in the penetration-torsional buckling integrated model with circle centers of the two end faces respectively.
In any of the above technical solutions, further, a value of the proportionality coefficient is 0.01.
In any of the above technical solutions, further, the displacement load applied to the center of the free end is a torsional angular displacement load.
The beneficial effect of this application is:
according to the technical scheme, critical torsional buckling analysis is carried out on an established penetration-torsional buckling integrated model by utilizing a finite element linear eigenvalue analysis method to obtain a first-order instability mode, a displacement loading mode is introduced in the process of a nonlinear post-buckling analysis method, nodes on two end faces of a tail transmission shaft are respectively coupled and bound with the circle center of the tail transmission shaft, and then a certain amount of torsional angular displacement load is added to the circle center of a free end of the transmission shaft to obtain a predicted failure load with high precision, so that the safety performance of a helicopter is improved.
The advantages of the technical scheme in the application are as follows:
1. the helicopter tail transmission shaft residual bearing capacity prediction method aims at the structural safety problem of the helicopter transmission system, and the residual bearing capacity of the helicopter tail transmission shaft after the small object is hit is predicted, so that a foundation is laid for the small object hit resistance strength design, and the safety performance of the helicopter is improved.
2. Aiming at the problem that local defects around damaged holes of a helicopter tail transmission shaft are difficult to model, a penetration dynamics analysis method is adopted, a penetration-torsion buckling integrated model is built, distortion, dispersion and interference grids are specially processed, a finite element three-dimensional model which is highly consistent with the actual damage working condition is obtained, and a foundation is laid for accurately predicting the critical buckling load (failure load) of the tail transmission shaft in the follow-up process.
3. Aiming at the problem that the critical buckling point of finite element nonlinear buckling analysis of the tail transmission shaft of the helicopter is difficult to determine, the method based on the displacement loading mode is introduced by respectively coupling and binding the nodes on the two end surfaces of the tail transmission shaft with the circle centers of the two end surfaces, and under the loading mode, the critical buckling point (the inflection point of a curve) of the tail transmission shaft is closer to the failure load of an experiment, the position of the critical buckling point on the curve is more prominent, and the method is helpful for calculating the accurate prediction failure load.
Drawings
The advantages of the above and/or additional aspects of the present application will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
fig. 1 is a schematic flow chart of a method for evaluating remaining bearing capacity after a helicopter tail drive shaft is broken down according to an embodiment of the present application;
FIG. 2 is a software screenshot schematic of a simulation model of a tail drive shaft according to an embodiment of the present application;
FIG. 3 is a software screenshot of critical buckling torsional loading results of a tail drive shaft according to an embodiment of the present application;
FIG. 4 is a graphical illustration of non-linear buckling failure load results for a tail drive shaft according to an embodiment of the present application;
FIG. 5 is a graph illustrating the non-linear buckling failure loading results under a conventional torque loading mode.
Detailed Description
In order that the above objects, features and advantages of the present application can be more clearly understood, the present application will be described in further detail with reference to the accompanying drawings and detailed description. It should be noted that the embodiments and features of the embodiments of the present application may be combined with each other without conflict.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application, however, the present application may be practiced in other ways than those described herein, and therefore the scope of the present application is not limited by the specific embodiments disclosed below.
Experiments show that the size of a hole after a small object hits the tail transmission shaft is locally damaged, the influence on overall rigidity is small, and therefore the failure of the tail transmission shaft still belongs to torsional buckling failure. Therefore, the residual bearing capacity of the tail transmission shaft researched by the embodiment after breakdown mainly refers to the torsional buckling limit strength after breakdown damage, namely (nonlinear buckling) failure load.
As shown in fig. 1, the present embodiment provides a method for evaluating remaining bearing capacity after a helicopter tail transmission shaft is broken down, including:
specifically, after the tail transmission shaft is hit by a small object, a hole with a certain size is left on the pipe wall. If a three-dimensional torsional buckling model is formed by cutting a hole with the same size as that of a small object hitting the hole on the pipe wall, complex deformation conditions such as pipe wall warping and curling left by the small object in the penetration process cannot be considered. These buckling deformations may have a large influence on the torsional buckling limit load.
Therefore, the embodiment provides an integration modeling method of penetration-torsional buckling, which can consider complex shapes such as warping and irregular boundaries caused by actual small object hitting.
Firstly, carrying out numerical simulation calculation on the small object hitting penetration process of the tail transmission shaft by adopting penetration dynamics, and calculating the damage of the small object penetration to the tail transmission shaft.
In the process of simulating small object penetration to the tail transmission shaft, the metal material fails under the environments of large strain, high strain rate and high temperature. In order to truly reflect the damage and deformation of the material, a JOHNSON-COOK model is selected to simulate the material characteristics of a small object and tail transmission in the research process. The experimental results and the numerical model results are combined, and the small object is found to have basically unchanged shape in the penetration process. In this embodiment, in order to ensure the accuracy of the simulation and save the computation time of the finite element model, a rigid body model is used to make an equivalent to a small object material.
Defining unit types, discretizing a tail transmission shaft and a small object by using an SOLID164 eight-node hexahedron unit, and adopting a single-point integral algorithm to meet the calculation of a large deformation process;
establishing a solid model, wherein the outer radius of the tail transmission shaft is 57.2mm, the inner radius is 55.6mm, the thickness is 1.6mm, and the length is 3085mm; and a three-dimensional Lagrange calculation method is adopted for grid division, and the reasonable grid size is beneficial to reducing the calculation time of the model.
In the embodiment, in order to determine the optimal size of the grid, the influence of different grid sizes on the damage morphology of the tail transmission shaft is researched, and finally the grid with the size of 0.7mm can be determined, so that the penetration process can be accurately simulated, and meanwhile, the calculation time can be remarkably reduced.
Because the size of the small object is far smaller than that of the tail transmission shaft, the local grid of the hitting area of the small object needs to be encrypted to be below the size of the small object. But the size of the mesh encryption area needs to be set scientifically. According to the embodiment, the incident positions respectively extend outwards by 20mm and the areas are used as grid encryption areas, and the comparison experiment results show that the processing mode can effectively reflect the damage appearance of the tail transmission shaft and save the model calculation time.
Therefore, in the process of carrying out numerical simulation calculation, 0.7mm is taken as the side length, first grid division is carried out on the punctured tail transmission shaft, the incident position of a small object is taken as the center, a grid encryption area is determined by taking the preset length of 20mm as the radius, then second grid division is carried out on the grid encryption area, and the grid side length of the first grid division is larger than the grid side length of the second grid division.
Then, defining impact collision contact between the small object and the tail transmission shaft by adopting a surface-to-surface erosion contact algorithm; setting the initial speed of the small object to be 500m/s, setting the incident position to be the middle edge position of the tail transmission shaft, and setting the angle to be 45 degrees; setting output time, output related parameters and the like according to the output requirement; outputting the model after ANSYS pretreatment as an LS-DYNA readable file (ASCII code format K file), modifying the K file by using UltraEdit software according to the selected material model and the measured material parameters, and finally calling an LS-DYNA solver to solve; and after the solution is completed, visualizing and analyzing the result through an LS-PREPOST post-processor.
Secondly, determining a finite element model of the damaged tail transmission shaft hit by a small object by adopting a finite element analysis method according to the calculated damage of the tail transmission shaft, and keeping the complete damage appearance.
And finally, carrying out grid screening on the finite element model, deleting abnormal grids, and recording the screened finite element model as a penetration-torsion buckling integrated model, wherein the abnormal grids at least comprise discrete grids, interference grids and distortion grids.
Specifically, a result file output by adopting the penetration-torsion buckling integrated simulation modeling contains a large number of distortion, dispersion and interference grids, so that the compatibility inspection of the finite element grids is not met, and the subsequent finite element critical buckling analysis cannot be directly carried out. Therefore, a large amount of intractable discrete, interference and distorted grids in the grid model after the small object is hit need to be processed, and meanwhile, the grid quality inspection is completed, so that the three-dimensional damage finite element model which meets the grid compatibility inspection after the small object is hit is formed.
In this embodiment, the discrete grid is a grid which is hit by a small object around the damaged hole and is not in contact with the tail transmission shaft any more after flying, that is, a grid which is not in contact with the tail transmission shaft any more after hitting. The interference grid is a grid in which two or more grids overlap in the same space.
And importing the output result file (an ASCII code format K file) into finite element preprocessing software, screening out a large number of distortion, dispersion and interference grids obtained after early-stage penetration analysis, wherein the length-width ratio of a distortion grid is larger than 5, then separating the screened unqualified grids, carrying out grid quality inspection, and finally obtaining a three-dimensional finite element model after passing inspection as shown in figure 2.
And 2, performing critical torsional buckling analysis on the penetration-torsional buckling integrated model by adopting a finite element linear characteristic value analysis method, and calculating a first-order instability mode of the tail transmission shaft.
On the basis of the penetration-torsion buckling integrated model containing the complex damage morphology, material properties, analysis steps, constraints, initial torsion loads and boundary conditions of the tail transmission shaft are defined, and the compatibility of the finite element mesh is checked again.
Particularly, unlike the finite element model obtained by the conventional modeling method, the load cannot be applied to the end face of the tail propeller shaft because the grid model of the tail propeller shaft, which has locally irregular holes and an irregular overall shape, is processed at this time instead of the geometric model.
Therefore, before defining boundary conditions, the nodes of the two end surfaces of the tail transmission shaft are respectively coupled and bound with the circle centers of the nodes, so that the constraint and the load applied to the end surfaces of the shaft can be transferred to the circle centers of the two end surfaces, and the end surfaces can be loaded.
And then, carrying out critical torsional buckling analysis on the grid model with the local damage holes after the small object is penetrated by adopting a finite element linear eigenvalue analysis method, calculating to obtain an eigenvalue and a first-order instability mode of the tail transmission shaft, and multiplying the input initial load by the calculated eigenvalue to obtain the critical torsional buckling load of the transmission shaft with the complex damage morphology after the small object is penetrated.
Outputting and guiding a finite element model subjected to the grid compatibility inspection into ABAQUS in the form of an inp file, selecting a linear elastic material model for the material property of the tail transmission shaft, and summarizing and analyzing the tensile test results of a plurality of tail transmission shaft test pieces to obtain the material parameters, wherein the tensile test results are shown in the following table:
TABLE 1 Material parameters of test pieces
TABLE 2 test shaft Material plasticity parameters
| Stress | Plastic strain |
| 341.5 | 0 |
| 360 | 0.00417 |
| 380 | 0.01263 |
| 400 | 0.02387 |
| 420 | 0.0373 |
| 440 | 0.05557 |
| 460 | 0.0828 |
| 480 | 0.18257 |
A buckling analysis module in finite element software is utilized to analyze linear characteristic values of the tail transmission shaft, and a mode with one fixed end and the other free end is selected as a boundary condition.
In order to simulate the actual working condition of loading the load to the shaft end face, two end faces of the cylindrical shell model are coupled with the circle centers of the two end faces respectively, so that the load can be transferred by applying the load to the circle center of the free end.
In the present embodiment, in order to reduce the amount of calculation while ensuring the calculation accuracy, a C3D8R unit is employed.
Since the nonlinear buckling analysis of the tail transmission shaft needs to be performed on the basis of the critical buckling analysis in the last step, a displacement field of a first-order instability mode obtained by solving the critical buckling analysis needs to be input into the nonlinear buckling analysis as an initial analysis model.
The method can be realized by inserting a keyword node file on top of end step in an inp file, global = yes; and U, outputting the node displacement to a displacement field of a first-order instability mode in the form of a file.
After submitting the operation, the characteristic value and the instability mode of the tail transmission shaft can be obtained, the result is shown in fig. 3, the input initial load is multiplied by the calculated characteristic value to obtain the critical torsion buckling load, and the critical buckling load of the tail transmission shaft containing the local complex damage morphology after being hit by a small object with the 45-degree angle of the middle edge position and the speed of 500m/s is calculated according to the output result and is 2783Nm.
And 3, multiplying the first-order instability mode by a proportionality coefficient, coupling and binding nodes on two end faces of the tail transmission shaft with the circle centers of the two end faces respectively by adopting a nonlinear post-buckling analysis method, applying a displacement load on the circle center of the free end of the tail transmission shaft, calculating a load-displacement curve, and recording a load corresponding to a peak value in the load-displacement curve as a predicted failure load of the tail transmission shaft, wherein the two ends of the tail transmission shaft are respectively a free end and a fixed end.
Preferably, the displacement load applied to the center of the free end is a torsional angular displacement load.
Specifically, because a certain geometric or dimensional defect often exists in an actually produced shaft, and the problem that the rigidity of the established lossless finite element shaft model is too large often results in that the predicted value of the nonlinear buckling failure load is higher than the actual value, a certain initial geometric defect needs to be applied to the finite element model at first.
And (3) multiplying a first-order instability mode obtained by critical buckling analysis by a small proportionality coefficient to serve as an initial defect, introducing the initial defect into nonlinear post-buckling analysis, replacing a buckling analysis step with a general static analysis step, and considering the problem of geometric nonlinearity caused by large deformation.
The first-order buckling mode obtained by the critical buckling analysis can be multiplied by a small scale factor such as 0.01 and used as an initial defect to be introduced into the nonlinear post-buckling analysis.
The traditional torsional buckling analysis generally adopts a torque loading mode, the size of the torsional buckling analysis is continuously increased along with the increase of a corner, an unloading process is generated at the moment of torsional instability of a shaft, the load corresponding to a point with a suddenly reduced slope of a torque-corner image is taken as the critical torsional buckling load of the shaft in the past, but the region of slope transition in an actual image is large, and the position of an inflection point is difficult to accurately derive, so that the predicted nonlinear buckling load and the actual error are large.
Based on this, this embodiment provides a displacement loading mode, in which nodes on two end surfaces of the tail transmission shaft are respectively coupled and bound with the center of the circle, a certain amount of torsional angular displacement load is added to the center of the circle of the free end to serve as a loading point in an analysis process, the moment and the rotation angle of each analysis step of the loading point are output, and a load-displacement image (curve) of the loading point is derived.
Aiming at the problems of curling, warping and residual stress around the hole after the impact, 150-200Mpa compressive stress needs to be applied to the curled and warped grids around the damaged hole of the tail transmission shaft. In addition, the nonlinear buckling of the tail shaft involves the problem of large mechanical deformation because the geometric nonlinear analysis module needs to be opened. Replacing the 'Buckle' analysis step with a general 'Static' analysis step, opening geometric nonlinear analysis and damping control, using a displacement loading mode, setting the load to be 0.4 radian, keeping the unit type, the material property, the constraint and the boundary condition unchanged, outputting the moment and the corner of a loading point, tracking and outputting a load-displacement path, and outputting in the form of an image.
As shown in fig. 4, as the torsional angular displacement load of the end face of the transmission shaft increases, the torque applied to the end face of the tail transmission shaft, which is fed back and output according to finite element calculation, increases continuously, that is, the curve increases continuously. When the load on the end face of the tail transmission shaft is larger than the nonlinear buckling instability load, an obvious unloading process can occur, namely the tail transmission shaft can continue to generate torsional deformation only by relatively small torque. The load-displacement curve shows that the torque applied to the end face of the output tail transmission shaft is reduced to a certain degree along with the increase of the torsional angular displacement load applied to the end face of the tail transmission shaft. Therefore, the peak value of the load-displacement curve is the nonlinear buckling instability load of the tail transmission shaft. According to the image result of the load-displacement curve and the historical output data of the torque in the ABAQUS, the nonlinear buckling instability load of the tail transmission shaft with the local complex damage morphology after the small object is hit at a 45-degree angle of the middle edge position at a speed of 500m/s is about 2450Nm.
When the tail transmission shaft with the complex damage morphology is buckled and unstabilized after a small object is hit, an obvious unloading (descending) process is carried out on the output load-displacement image, and at the moment, the peak value of the load is the predicted value of the nonlinear buckling failure load of the tail transmission shaft and is also the buckling failure load of the tail transmission shaft.
As shown in fig. 5, for the case of performing the predictive failure load analysis by using the conventional torque loading method, as the torque applied to the end face of the tail propeller shaft is increased, the torsion angle of the end face of the tail propeller shaft is increased slowly, that is, the curve is increased slowly. When the torque received by the end face of the tail transmission shaft is larger than the nonlinear buckling instability load of the tail transmission shaft, the tail transmission shaft can be continuously twisted only by relatively small torque, but the applied torque is that the input variable is only increased continuously, so that the torsion angle of the end face of the tail transmission shaft is increased suddenly along with the slow increase of the torque received by the end face of the tail transmission shaft on the image of the load-displacement curve, namely the curve rises suddenly. It is because this ramp rate transition typically has an arc transition, making it difficult to accurately obtain a particular transition point, and the accuracy of predicting the failure load of the tail drive shaft is low. Therefore, compared with the traditional method for analyzing the predicted failure load based on the torque loading mode, the result of the predicted failure load obtained in the embodiment is more accurate.
The technical scheme of the application is explained in detail in the above with reference to the accompanying drawings, and the application provides a method for evaluating the residual bearing capacity of a helicopter tail transmission shaft after the helicopter tail transmission shaft is punctured, which comprises the following steps: step 1, carrying out penetration dynamics analysis on a tail transmission shaft which is punctured by a small object by adopting penetration dynamics, and establishing a penetration-torsion buckling integrated model; step 2, performing critical torsional buckling analysis on the penetration-torsional buckling integrated model by adopting a finite element linear characteristic value analysis method, and calculating a first-order instability mode of the tail transmission shaft; and 3, multiplying the first-order instability mode by a proportionality coefficient, coupling and binding nodes on two end faces of the tail transmission shaft with the circle centers of the two end faces respectively by adopting a nonlinear post-buckling analysis method, applying a displacement load on the circle center of the free end of the tail transmission shaft, calculating a load-displacement curve, and recording a load corresponding to a peak value in the load-displacement curve as a predicted failure load of the tail transmission shaft, wherein the two ends of the tail transmission shaft are respectively a free end and a fixed end. Through the technical scheme in this application, improved the accuracy of helicopter tail transmission shaft breakdown back failure load aassessment, helped promoting the security performance of helicopter.
The steps in the present application may be sequentially adjusted, combined, and subtracted according to actual requirements.
The units in the device can be merged, divided and deleted according to actual requirements.
Although the present application has been disclosed in detail with reference to the accompanying drawings, it is to be understood that such description is merely illustrative and not restrictive of the application of the present application. The scope of the present application is defined by the appended claims and may include various modifications, adaptations, and equivalents of the subject invention without departing from the scope and spirit of the present application.
Claims (5)
1. A method for evaluating residual bearing capacity of a helicopter tail transmission shaft after breakdown is characterized by comprising the following steps:
step 1, carrying out penetration dynamics analysis on a tail transmission shaft which is punctured by a small object by adopting penetration dynamics, and establishing a penetration-torsion buckling integrated model;
step 11, carrying out numerical simulation calculation on the small object hit penetration process of the tail transmission shaft by adopting penetration dynamics, calculating the damage of the small object penetration to the tail transmission shaft,
in the process of carrying out numerical simulation calculation, firstly carrying out first grid division on the punctured tail transmission shaft, determining a grid encryption area by taking the incident position of the small object as a center and a preset length as a radius, and then carrying out second grid division on the grid encryption area;
step 12, determining a finite element model for hitting the damaged tail transmission shaft according to the calculated damage of the tail transmission shaft;
step 13, carrying out grid screening on the finite element model, deleting abnormal grids, and recording the screened finite element model as the penetration-torsion buckling integrated model;
step 2, performing critical torsional buckling analysis on the penetration-torsional buckling integrated model by adopting a finite element linear eigenvalue analysis method, and calculating a first-order instability mode of the tail transmission shaft;
and 3, multiplying the first-order instability mode by a proportionality coefficient, coupling and binding nodes on two end faces of the tail transmission shaft with the centers of the two end faces respectively by adopting a nonlinear post-buckling analysis method, applying a displacement load on the center of a free end of the tail transmission shaft, calculating a load-displacement curve, and recording a load corresponding to a peak value in the load-displacement curve as a predicted failure load of the tail transmission shaft, wherein two ends of the tail transmission shaft are respectively a free end and a fixed end.
2. The method for evaluating the residual carrying capacity after the helicopter tail transmission shaft is broken down according to claim 1, wherein the abnormal grids at least comprise a discrete grid, an interference grid and a distortion grid, wherein the grid with the grid aspect ratio larger than a distortion threshold value is taken as the distortion grid, and the value of the distortion threshold value is 5.
3. The method for evaluating the residual bearing capacity of the helicopter tail drive shaft after being broken down according to claim 1, wherein before the step 2, the method comprises the following steps:
defining boundary conditions of the penetration-torsional buckling integrated model, and coupling and binding nodes on two end faces of a tail transmission shaft in the penetration-torsional buckling integrated model with circle centers of the two end faces respectively.
4. The method for evaluating the residual bearing capacity of the helicopter tail transmission shaft after being broken down according to claim 1, wherein the value of the proportionality coefficient is 0.01.
5. The method for evaluating the residual bearing capacity of the helicopter tail drive shaft after being punctured as claimed in claim 1, wherein the displacement load applied to the center of the free end is a torsional angular displacement load.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202210430330.9A CN114925559B (en) | 2022-04-22 | 2022-04-22 | Method for evaluating residual bearing capacity of helicopter tail transmission shaft after breakdown |
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| CN202210430330.9A CN114925559B (en) | 2022-04-22 | 2022-04-22 | Method for evaluating residual bearing capacity of helicopter tail transmission shaft after breakdown |
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| WO2016141725A1 (en) * | 2015-03-12 | 2016-09-15 | 中车青岛四方机车车辆股份有限公司 | Local structure instability finite element simulation apparatus for high-speed train body and method therefor |
| CN113806868A (en) * | 2021-09-17 | 2021-12-17 | 湖南大学 | Helicopter tail transmission shaft bullet impact damage resistance tolerance analysis method |
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| WO2016141725A1 (en) * | 2015-03-12 | 2016-09-15 | 中车青岛四方机车车辆股份有限公司 | Local structure instability finite element simulation apparatus for high-speed train body and method therefor |
| CN113806868A (en) * | 2021-09-17 | 2021-12-17 | 湖南大学 | Helicopter tail transmission shaft bullet impact damage resistance tolerance analysis method |
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| 基于非线性屈曲分析的井架承载能力评估方法;许茂等;《石油机械》;20100910(第09期);1-6 * |
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