CN115235764B - A self-excited vibration test method for a helicopter supercritical floating spline shaft - Google Patents
A self-excited vibration test method for a helicopter supercritical floating spline shaft Download PDFInfo
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- G01M13/00—Testing of machine parts
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- G01N3/32—Investigating strength properties of solid materials by application of mechanical stress by applying repeated or pulsating forces
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Abstract
本发明公开了一种直升机超临界浮动花键轴的自激振动试验方法，其通过对台架试验的试验器进行改进，设计了模拟安装支座来模拟直升机尾传动系统浮动花键的实际安装结构，以满足尾轴自激振动试验条件，通过台架试验即可获得超临界浮动花键轴自激振动的边界条件，可以进一步明确浮动花键超临界尾轴的动态特性，自激振动边界更加清晰，为后期铁鸟试验或外场飞行试验提供了进一步的安全保障，且试验流程具有可操作性和可判断性，如果出现尾轴自激振动问题，可大大缩短排故周期、降低排故成本，为直升机超临界浮动花键轴的自激振动试验提供了一种安全、可靠的试验流程。
The invention discloses a self-excited vibration test method for a supercritical floating spline shaft of a helicopter. The tester of a bench test is improved, and a simulated installation support is designed to simulate the actual installation structure of the floating spline of a helicopter tail transmission system, so as to meet the self-excited vibration test conditions of the tail shaft. The boundary conditions of the self-excited vibration of the supercritical floating spline shaft can be obtained through the bench test, and the dynamic characteristics of the floating spline supercritical tail shaft can be further clarified. The self-excited vibration boundary is clearer, which provides further safety guarantee for the subsequent iron bird test or field flight test. The test process is operable and predictable. If the problem of self-excited vibration of the tail shaft occurs, the troubleshooting cycle can be greatly shortened and the troubleshooting cost can be reduced. A safe and reliable test process is provided for the self-excited vibration test of the supercritical floating spline shaft of the helicopter.
Description
Technical Field
The invention relates to the technical field of helicopter transmission system test experiments, in particular to a self-excitation vibration test method of a supercritical floating spline shaft of a helicopter.
Background
The main function of the tail transmission shafting of the helicopter is to transmit the tail transmission output power of the main reducer to the middle reducer and transmit the output power of the middle reducer to the tail reducer, and the tail transmission shafting is an important component of a transmission system of the helicopter. In recent years, along with further improvement of tactical indexes of helicopters, a supercritical tail shaft with a floating spline connection structure becomes an advanced transmission system design concept, the tail shaft is simple in structure, good in maintainability and high in reliability, floating splines are lubricated by grease, front and rear cylindrical surfaces are centered, and generally work for a long time above a first-order critical rotating speed, and a structural diagram is shown in fig. 1. When the floating spline structure of the tail shaft is in an abnormal working state, for example, the spline matching surface or the positioning surface is poor in lubrication, so that the friction force in the spline is increased, self-excited vibration is induced to increase, the abrasion of the spline matching surface is increased, the self-excited vibration is further increased, the local temperature of the matching part is increased repeatedly, lubricating grease is dried, the self-excited vibration is gradually dispersed, and the amplitude of the tail shaft is excessively large to break, so that the flight safety of a helicopter is seriously affected. Therefore, to realize long-time safe operation of the supercritical tail transmission shaft of the helicopter, one of the main factors affecting the operation safety of the supercritical tail shaft, namely the problem of self-excited vibration divergence of the supercritical tail shaft with a floating spline structure, must be solved.
At present, a bench test mainly developed by a helicopter tail transmission shaft comprises a critical rotation speed test and a supertorsion test, wherein the test is generally carried out on an electric power closed tester or a mechanical power closed tester, flanges at two ends of a tail shaft are connected with test equipment through a laminated coupler, the test is carried out at a certain torque and rotation speed, a vibration test system is utilized to obtain a tail shaft Bode diagram, the working rotation speed safety margin of the supercritical shaft is determined, and meanwhile, the supertorsion test with a certain cycle time number is carried out under a specified lamination installation deflection angle, so that the structural integrity and durability of the tail shaft are verified. In addition, according to the requirements of helicopter development specifications, an iron bird test or an actual flight test is the most ideal research means on the real ground, but the iron bird test and the test flight test have large risks, high cost and long time, and cannot be used as test conditions for researching self-excited vibration, so that the application of the method is limited. Thus, no relevant self-excited vibration verification test is specified for the supercritical tail shaft containing the floating spline, nor is no relevant test method available, whether bench test or bird test.
Aiming at the research of the supercritical tail shaft self-excitation vibration with floating splines, the method has the advantages that the starting of China is late, the mechanism research is not perfect, the test research in the aspect is less, at present, only a few test devices with simple functions are used for verifying and calculating simulation results, a simulation test piece or a scaling piece is mainly adopted for testing, meanwhile, boundary conditions are simplified, the test working condition is single, the test load under the actual boundary conditions still cannot be simulated, how to effectively develop the supercritical shaft self-excitation vibration test research, the test method is standardized, the self-excitation vibration divergence boundary is touched, and the method is very important for inhibiting the supercritical tail shaft self-excitation vibration.
Disclosure of Invention
The invention provides a self-excited vibration test method of a supercritical floating spline shaft of a helicopter, which aims to solve the technical problem that the boundary condition of the self-excited vibration of the supercritical floating spline shaft cannot be obtained by the existing test method.
According to one aspect of the invention, there is provided a self-excited vibration test method of a supercritical floating spline shaft of a helicopter, comprising the following steps:
Designing a simulation mounting support for mounting the tail transmission output pinion assembly so as to simulate the actual mounting structure of the floating spline of the tail transmission system of the helicopter;
The simulated mounting support and the supercritical tail shaft are connected in series in a tester;
Arranging a test sensor and setting various parameter limit values in a tester test system;
And carrying out a tail shaft self-excitation vibration test to obtain the boundary condition of the supercritical floating spline shaft self-excitation vibration.
Further, the tail transmission pinion assembly comprises a pinion output shaft, a case assembly, a roller bearing and a ball bearing, the front end of the pinion output shaft is supported on the roller bearing, the rear end of the pinion output shaft is supported on the ball bearing, the ball bearing is mounted on the case assembly, the simulation mounting support comprises a case body, a case cover, a lubricating oil nozzle, an expansion sleeve flange and a sealing end cover, the case body and the case cover are in split design and are fixedly connected up and down, the roller bearing and the case assembly are mounted between the case body and the case cover, the case assembly is fixedly connected with the rear end faces of the case body and the case body to realize axial fixation of the tail transmission pinion assembly, the roller bearing is in small clearance fit with the case body and the case cover, the lubricating oil nozzle is mounted on the case cover and extends into a cavity formed by encircling the case cover and the case body, an oil return port is formed in the side face of the bottom of the case body and is used for being connected with an external lubricating oil system, the cylindrical face of the expansion sleeve flange is matched with the cylindrical face of the pinion output shaft so as to realize friction transmission torsion, and the sealing end cover is fixedly mounted on the front end cover and the case body.
Further, the process of arranging the test sensor includes the following:
at least two groups of temperature indicating sheets are stuck on the inner cylindrical surface of the flange plate, which is transmitted from the tail, corresponding to the spline contact position, three-way vibration sensors are arranged at the simulation mounting support and the bearing support, a horizontal/vertical laser displacement sensor and a rotating speed sensor are arranged at the 1/2 length of the supercritical tail shaft, and thermocouples are stuck at the outer ring of the support bearing.
Further, the process of developing the tail shaft self-excitation vibration test to obtain the boundary condition of the supercritical floating spline shaft self-excitation vibration comprises the following steps:
developing a modal test to identify modal parameters including natural frequencies, damping ratios, and modal shapes;
Developing a rotation speed debugging test to verify whether the working state of the tail shaft is normal;
Performing operation test according to the test load spectrum to obtain test data of self-excited vibration of the tail shaft;
Developing a poor lubrication state test on the basis of the operation test to quantitatively judge the lubrication grease state of the spline during self-excited vibration mutation;
performing a durability abrasion test based on the lubricating grease state determined by the poor lubrication state test, and determining the boundary values of acceleration and displacement of self-excited vibration of the tail shaft;
And checking the abrasion condition of the spline and the positioning section after the durability abrasion test by using a body-viewing mirror, measuring the matching size of the spline and the positioning section, and determining the boundary condition of self-excited vibration of the tail shaft.
Further, the process of developing the modal test to identify the modal parameters includes the following:
the acceleration sensor is arranged at a certain measuring point of the tail shaft, the pulse force hammer is utilized to sequentially hammer to generate multi-point excitation, and a pulse excitation signal generated by the pulse force hammer and a response signal measured by the acceleration sensor are collected for analysis so as to identify modal parameters.
Further, the process of developing the rotational speed debugging test to verify whether the working state of the tail shaft is normal includes the following steps:
Starting from zero rotation speed, gradually increasing the rotation speed to 120% of rated rotation speed at intervals of 10% of rated rotation speed, stably running for 3 minutes in each rotation speed state, recording the vibration fundamental frequency and total quantity of the simulated installation support corresponding to each rotation speed state point and the displacement fundamental frequency and total quantity of the tail shaft, entering the next step if the vibration fundamental frequency and total quantity are not exceeded, and repeatedly executing a rotation speed debugging test after further eliminating influence factors causing excessive vibration if the vibration is exceeded, so that the vibration is normal in an actual simulation state.
Further, the process of performing operation test according to the test load spectrum to obtain test data of the self-excited vibration of the tail shaft comprises the following steps:
Running tests are carried out according to test load spectrums to simulate the rotating speed and load of the tail shaft in an actual working state, each test state is stable for 3 minutes, specific numerical values of fundamental frequency and self-excited vibration in each test state are recorded, the test is repeated for three times, the maximum value of each test state is taken as vibration data when the tail shaft works normally, meanwhile, the temperature change condition of a bearing is recorded, a flange plate temperature indicating piece is taken down after each test, and the highest temperature of a spline part in the whole process is recorded.
Further, the process of developing a poor lubrication state test on the basis of an operation test to quantitatively judge the grease state of the spline when self-excited vibration is suddenly changed comprises the following steps:
And reducing the smearing amount of the lubricating grease at the spline and the positioning surface by taking 10% of the total weight as an interval, repeating the test procedure of the operation test to perform the poor lubrication state test, comparing the test result of the poor lubrication state test with the test result of the operation test, judging whether the self-excited vibration of the tail shaft is suddenly changed, stopping the poor lubrication state test to enter the next step if the self-excited vibration is suddenly changed, further reducing the smearing amount of the lubricating grease if the self-excited vibration is not suddenly changed, and repeating the poor lubrication state test until the self-excited vibration is suddenly changed.
Further, the process of determining the boundary values of acceleration and displacement of the self-excited vibration of the tail shaft by performing a durability wear test based on the grease state determined by the poor lubrication state test comprises the following steps:
and (3) selecting the last lubricating grease smearing amount in the poor lubrication state test and a plurality of test programs in a load spectrum causing self-excited vibration mutation as test conditions, developing a floating spline durability abrasion test under the mounting deflection angle of the laminated coupling specified by the tail shaft super-torsion test, paying attention to the vibration, displacement, spline and bearing temperature change conditions of the tail shaft in the test process, simultaneously detecting the abrasion conditions of the spline and the positioning section in each cycle, and stopping the test when the self-excited vibration is further increased and exceeds 50% of the mutation value in the poor lubrication state test.
Further, the boundary conditions of the self-excited vibration of the tail shaft comprise a displacement value and a vibration value corresponding to the self-excited vibration when the durability abrasion test is stopped, and the matching dimension measurement result of the spline and the positioning section after the durability abrasion test.
The invention has the following effects:
According to the self-excitation vibration test method for the supercritical floating spline shaft of the helicopter, provided by the invention, the simulated mounting support for mounting the tail transmission output pinion assembly is designed so as to reliably support the floating spline structure, and the actual mounting structure of the floating spline of the tail transmission system of the helicopter can be simulated so as to meet the self-excitation vibration test conditions of the tail shaft. And then, the simulated mounting support and the supercritical tail shaft are connected in series in a tester, and then a test sensor is arranged so as to measure test parameters in the test process, parameter limit values are set in a test system of the tester, and finally, a tail shaft self-excited vibration test is carried out so as to obtain the boundary condition of the self-excited vibration of the supercritical floating spline shaft. According to the self-excited vibration test method, the tester for the bench test is improved, the simulated mounting support is designed to simulate the actual mounting structure of the floating spline of the tail transmission system of the helicopter so as to meet the self-excited vibration test conditions of the tail shaft, the boundary conditions of the self-excited vibration of the supercritical floating spline shaft can be obtained through the bench test, the dynamic characteristics of the supercritical tail shaft of the floating spline can be further clarified, the self-excited vibration boundary is clearer, further safety guarantee is provided for the later-stage bird test or the external-field flight test, the test flow has operability and judgeability, if the problem of the self-excited vibration of the tail shaft occurs, the troubleshooting period can be greatly shortened, the troubleshooting cost can be reduced, and the safe and reliable test flow is provided for the self-excited vibration test of the supercritical floating spline shaft of the helicopter.
In addition to the objects, features and advantages described above, the present invention has other objects, features and advantages. The present invention will be described in further detail with reference to the drawings.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the application. In the drawings:
FIG. 1 is a schematic structural view of a floating spline structure.
Fig. 2 is a flow chart of a method of self-excited vibration testing of a supercritical floating spline shaft of a helicopter in accordance with a preferred embodiment of the invention.
FIG. 3 is a schematic illustration of the mounting of the tail transfer output pinion assembly to a simulated mounting bracket in a preferred embodiment of the invention.
FIG. 4 is a schematic illustration of the mounting structure of a simulated mounting support and supercritical tail shaft in series in an electric power seal tester in accordance with a preferred embodiment of the present invention.
Fig. 5 is a schematic view of the sub-flow of step S4 in fig. 2.
Detailed Description
Embodiments of the invention are described in detail below with reference to the attached drawing figures, but the invention can be practiced in a number of different ways, as defined and covered below.
As shown in fig. 2, a preferred embodiment of the present invention provides a self-excited vibration test method for a supercritical floating spline shaft of a helicopter, comprising the following steps:
S1, designing a simulation mounting support for mounting a tail transmission output pinion assembly so as to simulate an actual mounting structure of a floating spline of a helicopter tail transmission system;
s2, connecting the simulation mounting support and the supercritical tail shaft in series in a tester;
s3, arranging a test sensor and setting various parameter limit values in a tester test system;
And S4, carrying out a tail shaft self-excitation vibration test to obtain the boundary condition of the supercritical floating spline shaft self-excitation vibration.
It can be appreciated that according to the self-excitation vibration test method of the supercritical floating spline shaft of the helicopter, through designing the simulation mounting support for mounting the tail transmission output pinion assembly so as to reliably support the floating spline structure, the actual mounting structure of the floating spline of the tail transmission system of the helicopter can be simulated so as to meet the self-excitation vibration test conditions of the tail shaft. And then, the simulated mounting support and the supercritical tail shaft are connected in series in a tester, and then a test sensor is arranged so as to measure test parameters in the test process, parameter limit values are set in a test system of the tester, and finally, a tail shaft self-excited vibration test is carried out so as to obtain the boundary condition of the self-excited vibration of the supercritical floating spline shaft. According to the self-excited vibration test method, the tester for the bench test is improved, the simulated mounting support is designed to simulate the actual mounting structure of the floating spline of the tail transmission system of the helicopter so as to meet the self-excited vibration test conditions of the tail shaft, the boundary conditions of the self-excited vibration of the supercritical floating spline shaft can be obtained through the bench test, the dynamic characteristics of the supercritical tail shaft of the floating spline can be further clarified, the self-excited vibration boundary is clearer, further safety guarantee is provided for the later-stage bird test or the external-field flight test, the test flow has operability and judgeability, if the problem of the self-excited vibration of the tail shaft occurs, the troubleshooting period can be greatly shortened, the troubleshooting cost can be reduced, and the safe and reliable test flow is provided for the self-excited vibration test of the supercritical floating spline shaft of the helicopter.
It will be appreciated that in the step S1, structural modifications are required to the existing electric power seal tester or mechanical power seal tester to satisfy the tail shaft self-excited vibration test conditions. As shown in fig. 3, the tail transfer pinion assembly includes a pinion output shaft supported at a front end thereof on a roller bearing and at a rear end thereof on a ball bearing mounted on a case assembly, the roller bearing and the ball bearing. The simulation installing support comprises a box body, a box cover, a lubricating oil nozzle, an expansion sleeve flange and a sealing end cover, wherein the box body and the box cover are in an upper-lower split design and are fixedly connected, and specifically, the box body and the box cover are positioned through positioning pins on two sides and are fixedly connected through four M20 bolts. The roller bearing and the casing component are installed between the box body and the box cover, the casing component is fixedly connected with the rear end faces of the box body and the box body so as to realize axial fixation of the tail transmission output pinion component, and specifically, the casing component is fixed on the rear end faces of the box cover and the box body through 8M 12 bolts, and the roller bearing is in small clearance fit with the box body and the box cover so as to meet the requirements of a bearing manual. The oil nozzle is arranged on the box cover and extends into a cavity formed by surrounding the box cover and the box body, and is used for lubricating the roller bearing and the ball bearing, an oil return port is formed in the side face of the bottom of the box body and is used for being connected with an external oil system, the oil enters the oil supply port and then is divided into two paths, the roller bearing and the ball bearing are lubricated through small holes on two sides of the oil nozzle respectively, and the oil is pumped back to the external oil system through the oil return port. The outer cylindrical surface of the expansion sleeve flange is matched with the inner hole cylindrical surface of the pinion output shaft, a certain moment is applied to a round of inner hexagonal bolt of the expansion sleeve according to design requirements, and then interference fit is formed between the round of inner hexagonal bolt and the inner hole of the pinion output shaft, so that friction torque transmission is realized. The sealing end cover is fixedly arranged on the front end surfaces of the box body and the box cover so as to improve the sealing performance. The rear end of the pinion output shaft is connected with the tail transmission flange plate through a floating spline, wherein the rear end of the pinion output shaft is provided with an internal spline, and the tail transmission flange plate is provided with an external spline. Through improving the experimental tester of bench test, designed the actual mounting structure that simulate the floating spline of helicopter tail transmission system to satisfy tail shaft self-excitation vibration test condition.
It will be appreciated that in step S2, the pinion output shaft is connected to the tail transfer out flange via floating splines, and the tail transfer out flange is connected to the supercritical tail shaft via a laminated coupling, thereby connecting the simulated mounting support and the supercritical tail shaft in series in the tester. Wherein the tester adopts an electric power closed tester or a mechanical power closed tester. Preferably, as shown in fig. 4, the simulated mounting support and the supercritical tail shaft are connected in series in the electric power closed tester, and then the whole tester system is installed and aligned. The electric power sealing tester adopts a driving motor as power, the output rotating speed of the driving motor is regulated through a variable frequency speed regulator to regulate the rotating speed of the supercritical tail shaft, and the power of the driving motor is transmitted to the supercritical tail shaft through a front speed increasing gear box for testing. The torque load of the tester is applied by the loading motor at the other end, the electric power emitted by the loading motor can be adjusted by changing the exciting current of the loading motor, the electric power output by the loading motor generates a resisting moment on a motor rotor, the torque load can be applied to the supercritical tail shaft, and meanwhile, the power output by the loading motor can be fed back to the front dragging motor or the power grid through the electric power sealing system. The simulated mounting support, the front speed increasing gear box and the rear speed reducing gear box are lubricated by an external lubrication system, and a lubricating system loop is provided with a lubricating oil pressure sensor and a lubricating oil temperature sensor.
It will be appreciated that the process of disposing the test sensor in step S3 specifically includes the following:
at least two groups of temperature indicating sheets are stuck on the inner cylindrical surface of the flange plate, which is transmitted from the tail, corresponding to the spline contact position, three-way vibration sensors are arranged at the simulation mounting support and the bearing support, a horizontal/vertical laser displacement sensor and a rotating speed sensor are arranged at the 1/2 length of the supercritical tail shaft, and thermocouples are stuck at the outer ring of the support bearing.
Specifically, at least two groups of temperature indicating sheets are stuck at the contact positions of corresponding splines on the inner cylindrical surface of the tail transmission flange plate (as shown in fig. 1), the temperature of the splines in the test process can be measured, three-way vibration sensors are arranged at the simulated mounting support and the bearing support, vibration values in the horizontal direction, the vertical direction and the axial direction can be measured, a horizontal/vertical laser displacement sensor and a rotating speed sensor are arranged at the 1/2 length of the supercritical tail shaft, the vertical displacement, the horizontal displacement and the rotating speed of the supercritical tail shaft in the test process can be measured, thermocouples are stuck at the outer ring of the support bearing, and the temperature change condition of the bearing can be monitored in the test process.
And then, opening a tester control system and a testing system, setting various parameter limiting values of the tester, including torque, rotating speed, displacement, vibration, lubricating oil pressure and lubricating oil temperature of a lubricating system and the like, and confirming that the preparation work before various tests is finished, thereby having safety test conditions.
It will be appreciated that, as illustrated in fig. 5, the step S4 specifically includes the following:
step 41, carrying out a modal test to identify modal parameters, wherein the modal parameters comprise natural frequency, damping ratio and modal shape;
step S42, developing a rotation speed debugging test to verify whether the working state of the tail shaft is normal;
step S43, performing operation test according to the test load spectrum to obtain test data of self-excited vibration of the tail shaft;
S44, developing a poor lubrication state test on the basis of an operation test to quantitatively judge the lubrication grease state of the spline during self-excited vibration mutation;
step S45, performing a durability abrasion test based on the lubricating grease state determined by the poor lubrication state test, and determining the boundary value of the acceleration and displacement of the self-excited vibration of the tail shaft;
and S46, checking the abrasion condition of the spline and the positioning section after the durability abrasion test by using a body-vision mirror, measuring the matching size of the spline and the positioning section, and determining the boundary condition of self-excited vibration of the tail shaft.
It can be understood that in the invention, firstly, mode parameters including natural frequency, damping ratio and mode vibration mode are identified through a mode test, a basis is provided for the safe development of a rotating speed test, then the rotating speed test is developed to verify whether the working state of the tail shaft is normal, the vibration rule of the tail shaft in the working rotating speed range is obtained by touching, then the running test is carried out to simulate the rotating speed and load of the tail shaft in the actual working state, specific test data of the self-excited vibration of the tail shaft are obtained, then the lubrication failure state test is carried out on the basis of the running test, the self-excited vibration mutation verification is carried out, the spline lubricating grease state during mutation is quantitatively judged, the endurance wear test is carried out on the basis of the lubricating grease state determined by the lubrication failure test, the durability and the structural integrity of the tail shaft are further verified, the boundary value of the self-excited vibration acceleration and displacement of the tail shaft is determined, finally, the abrasion condition of a spline and a locating section after the test is further determined through size detection and visual inspection, the boundary condition of the self-excited vibration of the tail shaft is finally obtained, the dynamic characteristics of the tail shaft can be further clearly floated, the self-excited vibration boundary is more clear, the self-excited vibration boundary of the tail shaft is ensured, the self-excited vibration failure test or the self-excited vibration critical operation process is greatly shortened, and the flying process can be further shortened, and the vibration critical vibration test has a vibration critical process can be greatly run is shortened, and the vibration test has the reliability is greatly run.
It will be appreciated that the step S41 specifically includes the following:
The method comprises the steps of developing a modal test, arranging an acceleration sensor at a certain measuring point of a tail shaft by using modal test software, sequentially hammering by using a pulse force hammer to generate multi-point excitation, collecting a pulse excitation signal generated by the pulse force hammer and a response signal measured by the acceleration sensor for analysis, wherein the analysis process specifically comprises FFT analysis, transfer function calculation and the like so as to identify modal parameters, and the modal parameters mainly comprise natural frequency, damping ratio and modal vibration mode.
It will be appreciated that the step S42 specifically includes the following:
And (3) carrying out a rotation speed debugging test, namely starting from zero rotation speed, gradually increasing the rotation speed to 120% of rated rotation speed at intervals of 10% of rated rotation speed, and stably operating each rotation speed state for 3 minutes, wherein when the rotation speed is increased to be close to the rotation speed corresponding to the natural frequency obtained in the step (S41), the rotation speed is quickly passed, no stay is carried out, meanwhile, the vibration fundamental frequency and total quantity of a simulated mounting support corresponding to each rotation speed state point and the vibration fundamental frequency and total quantity of a tail shaft displacement are recorded, if the vibration fundamental frequency and total quantity are not exceeded, the next step is carried out, if the vibration fundamental frequency and total quantity are not exceeded, the influence factors causing the excessive vibration are further eliminated, and then the rotation speed debugging test is repeatedly carried out, so that the vibration is ensured to be normal in an actual simulation state. The factors causing excessive vibration include mechanical installation, unbalance of bolts, internal negative pressure at spline matching positions, a testing system and the like.
It will be appreciated that the step S43 specifically includes the following:
Running tests are carried out according to test load spectrums to simulate the rotating speed and the load of the tail shaft in the actual working state, each test state is stable for 3 minutes, fundamental frequency vibration and self-excitation vibration of the tail shaft are concerned, specific numerical values of the fundamental frequency vibration and the self-excitation vibration in each test state are recorded, the tests are repeated for three times, the maximum value of each test state is taken as vibration data when the tail shaft works normally, meanwhile, the temperature change condition of a bearing is recorded, a flange plate temperature indicating piece is taken down after each test, and the highest temperature of a spline part in the whole process is recorded. The test load spectrum comprises test loads in various working states such as starting, slow ground, slow air, flat flight, climbing, turning, descending and the like, and each working state is controlled by a test program.
It will be appreciated that the step S44 specifically includes the following:
And (3) reducing the grease smearing quantity at the spline and the positioning surface by taking 10% of the total weight as an interval, repeatedly executing the test procedure in the step S43 to perform the poor lubrication state test, comparing the test result of the poor lubrication state test with the test result of the operation test, judging whether the self-excited vibration of the tail shaft is suddenly changed, stopping the poor lubrication state test to enter the next step if the self-excited vibration is suddenly changed, and further reducing the grease smearing quantity if the self-excited vibration is not suddenly changed, and repeatedly executing the step S44 until the self-excited vibration is suddenly changed.
It will be appreciated that the self-exciting vibration of the floating spline tail drive shaft referred to in this invention includes the following concepts:
(1) When the tail transmission shaft passes through the 1 st order critical rotation speed and a certain condition is met between the external damping and the internal damping (spline tooth surface friction and positioning surface friction), the system may generate self-excited vibration;
(2) When the tail transmission shaft is in a supercritical working state and the internal friction damping is smaller than the external damping, the transmission shaft generates self-excited vibration, but the vibration amplitude of the transmission shaft is in a certain range at the moment, so that a stable limit ring can be formed;
(3) When the tail transmission shaft is in a supercritical working state and the internal friction damping is larger than the external damping, the vibration of the transmission shaft breaks through a limit ring, the vibration amplitude is increased sharply, self-excited vibration divergence occurs, and a destabilization phenomenon occurs.
The self-excited vibration means that a subharmonic wave exists all the time in the running process of the tail shaft, the frequency of the subharmonic wave is the same as the first-order natural frequency of the tail shaft, the corresponding displacement value and vibration acceleration under the self-excited vibration frequency can have abrupt changes in order of magnitude, and particularly, the displacement is the most obvious. For example, in a certain load state, the displacement or acceleration corresponding to the self-excited vibration frequency of a point or points at the tail shaft is changed by orders of magnitude compared with the test result in the step S43, if the displacement is changed from 0.1mm to 1mm and the vibration acceleration is changed from 0.03g to 0.3g, the self-excited vibration of the tail shaft is judged to be suddenly changed.
It will be appreciated that the step S45 specifically includes the following:
and (3) selecting the last lubricating grease smearing amount in the step (S44) and a plurality of test programs in a load spectrum causing self-excited vibration mutation as test conditions, developing a floating spline durability wear test under the mounting deflection angle of the laminated coupling specified by the tail shaft super-torsion test, paying attention to the vibration, displacement, spline and bearing temperature change conditions of the tail shaft in the test process, simultaneously detecting the wear conditions of the spline and the positioning section in each cycle, and stopping the test when the self-excited vibration is further increased and exceeds 50% of the mutation value in the step (S44).
It will be appreciated that in said step S46, the wear conditions of the spline and the positioning segment after the endurance wear test are checked with a body-vision mirror, and the mating dimensions of the spline and the positioning segment are measured, and the maximum temperatures of the temperature indicating plate and the thermocouple are recorded, so that the boundary conditions of the self-excited vibration of the tail shaft can be determined.
Optionally, the boundary condition of the self-excited vibration of the tail shaft is checked by taking three parameters, namely a displacement value and a vibration value corresponding to the self-excited vibration when the durability abrasion test is stopped and a matching dimension measurement result of the spline and the positioning section after the durability abrasion test, as the standard, and any parameter is out of limit and the test is stopped immediately. And the inspection result of the stereoscopic vision mirror, the temperature indicating piece and the thermocouple value are only used as references, for example, obvious scratches, pits or temperature exceeding limit values and other phenomena appear on the inspection spline and the positioning surface of the stereoscopic vision mirror, the test can be stopped, and the rest of the stereoscopic vision mirror is processed according to actual conditions, so that the test safety is not affected. And in the follow-up process, boundary conditions obtained by a bench test are strictly referred to when an iron bird test or an outfield flight test is carried out, so that the smooth development of the whole machine test can be ensured.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (7)
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