阅读说明：本技术 叶片振动疲劳试验方法和系统、控制装置和存储介质 (Blade vibration fatigue test method and system, control device and storage medium ) 是由 赵琳 贾林 卢沉琪 范志强 黎胜权 黄振东 王海涛 于 2020-06-08 设计创作，主要内容包括：本公开涉及一种叶片振动疲劳试验方法和系统、控制装置和存储介质。该叶片振动疲劳试验方法包括：对安装状态下的发动机叶片进行振动谐响应数值分析,确定低应力梯度区域；在发动机叶片低应力梯度区域布置应变片,将应变片的应变信号用于振动控制,实现应变闭环控制。本公开通过低梯度应变监测可以实现对应变信号长期稳定的控制,极大提高了试验的测试精度和稳定性,应变闭环控制疲劳试验方法更适用于复合材料叶片的疲劳试验。(The disclosure relates to a blade vibration fatigue test method and system, a control device and a storage medium. The blade vibration fatigue test method comprises the following steps: carrying out vibration harmonic response numerical analysis on the engine blade in the mounting state to determine a low stress gradient region; and arranging a strain gauge in a low stress gradient area of the engine blade, and using a strain signal of the strain gauge for vibration control to realize strain closed-loop control. According to the method, the strain signal can be stably controlled for a long time through low-gradient strain monitoring, the testing precision and stability of the test are greatly improved, and the strain closed-loop control fatigue test method is more suitable for the fatigue test of the composite material blade.)

1. A blade vibration fatigue test method is characterized by comprising the following steps:

carrying out vibration harmonic response numerical analysis on the engine blade in the mounting state to determine a low stress gradient region;

and arranging a strain gauge in a low stress gradient area of the engine blade, and using a strain signal of the strain gauge for vibration control to realize strain closed-loop control.

2. The blade vibration fatigue testing method of claim 1, further comprising:

determining the proportional relation between the low stress gradient point and the maximum stress point of the blade;

and (4) according to the proportional relation between the maximum stress point and the low gradient point, converting the given strain value into the strain of the maximum stress point, and recording the fatigue test result and the cycle number.

3. The blade vibration fatigue test method according to claim 1 or 2, wherein the arranging of the strain gauge in the low stress gradient area of the engine blade and the using of the strain signal of the strain gauge for vibration control comprises:

arranging a plurality of strain gauges in a low stress gradient area of an engine blade, and collecting multi-path strain signals;

and (4) screening optimal strain data in real time as a control feedback signal by adopting a multipoint minimum standard deviation control mode.

4. The blade vibration fatigue testing method according to claim 3, wherein the arranging of the strain gauge in the low stress gradient area of the engine blade and the using of the strain signal of the strain gauge for vibration control further comprises:

and comparing the control feedback signal with the previous round of control signal to generate a current round of control signal so as to realize strain closed-loop control.

5. The blade vibration fatigue test method according to claim 3, wherein the real-time screening of the optimal strain data as the control feedback signal by using the multipoint minimum standard deviation control method comprises:

for each strain gauge, determining an average strain value and a standard deviation of strain signals acquired for multiple times in a preset time period;

and selecting the strain data corresponding to the strain gauge with the minimum standard deviation as a strain control feedback signal.

6. The blade vibration fatigue testing method of claim 5, further comprising, after determining, for each strain gauge, an average strain value and a standard deviation of the strain signals acquired a plurality of times within a predetermined time period:

judging whether a plurality of strain gauges have dead spots or not;

under the condition that dead spots exist in a plurality of strain gauges, the dead spots are removed, and then the step of determining the average strain value and the standard deviation of the strain signals acquired for multiple times in a preset time period is executed for each strain gauge;

and when no defect point exists in the plurality of strain gauges, selecting the strain data corresponding to the strain gauge with the minimum standard deviation as a strain control feedback signal.

7. The blade vibration fatigue testing method of claim 6, wherein the determining whether there is a dead spot in the plurality of strain gauges includes:

determining a strain signal value of each strain gauge and a strain signal mean value of all strain points;

for each strain gauge, judging whether the absolute value of the difference value between the strain signal value and the strain signal mean value is greater than a preset threshold value;

under the condition that the absolute value of the difference value between the strain signal value of one strain gauge and the mean value of the strain signals is greater than a preset threshold value, judging that the strain gauge is a dead pixel;

and under the condition that the absolute value of the difference value between the strain signal value of each strain gauge and the mean value of the strain signals is not greater than a preset threshold value, judging that no dead pixel exists in the plurality of strain gauges.

8. The blade vibration fatigue test method according to claim 1 or 2, further comprising:

controlling a vibration table to perform a low-magnitude sine frequency sweep test on the blade, controlling the acceleration of the table top, measuring the natural frequency of the blade, and setting the frequency band range of a band-pass filter;

and controlling the vibration table to apply a low-magnitude fixed-frequency vibration test to the blade to observe the signal quality after filtering.

9. The blade vibration fatigue test method according to claim 1 or 2, further comprising:

and controlling the vibration table to gradually load exciting force, carrying out a resonance residence test under the condition that the control point strain of the blade reaches a given strain value, and starting cycle counting.

10. The blade vibration fatigue testing method of claim 9, further comprising:

monitoring the change of the resonant frequency of the blade, adjusting the excitation frequency of the vibration table to be consistent with the resonant frequency of the blade in real time under the condition that the blade structure is damaged, and controlling the strain to be kept in a given strain value state by adjusting the excitation energy of the vibration table.

11. The blade vibration fatigue testing method of claim 10, further comprising:

recording the current vibration cycle times under the condition that the vibration exciting frequency of the vibration table is reduced to the set failure criterion frequency of the blade with cracks and the blade failure, and controlling the vibration table to stop working;

and under the condition that the current vibration cycle number reaches a given target cycle number but the resonance frequency is not reduced to the failure criterion frequency, controlling the vibration table to automatically stop.

12. A control device, comprising:

the low stress gradient region determining module is used for carrying out vibration harmonic response numerical analysis on the engine blade in the mounting state and determining a low stress gradient region;

and the closed-loop control module is used for arranging a strain gauge in a low stress gradient area of the engine blade, and using a strain signal of the strain gauge for vibration control to realize strain closed-loop control.

13. The control device according to claim 12, wherein the control device is configured to perform operations for implementing the blade vibration fatigue test method according to any one of claims 2 to 11.

14. A control device, comprising:

a memory to store instructions;

a processor for executing the instructions to cause the control device to perform operations to implement the blade vibration fatigue testing method of any of claims 1-11.

15. A blade vibration fatigue testing system comprising a control device according to any of claims 12-14.

16. The blade vibration fatigue test system of claim 15, further comprising a test fixture, a vibration table, a power amplifier, a signal generator, a strain conditioning front end, and a data collector.

17. The blade vibration fatigue testing system of claim 16, wherein the strain conditioning front end comprises a bridge, a strain amplifier, and a band pass filter.

18. A computer readable storage medium storing computer instructions which, when executed by a processor, carry out a blade vibration fatigue testing method according to any one of claims 1-11.

Technical Field

The disclosure relates to the field of engines, in particular to a blade vibration fatigue test method and system, a control device and a storage medium.

Background

The blades are key parts of the aero-engine, have great influence on the overall performance of the engine, particularly the safety and the reliability, and have a large number of rotor blades and severe working conditions. According to statistics, the blade vibration fault accounts for about one third of the structural faults of the aircraft engine, and most of the blade faults such as cracks, breakage and the like are caused by blade vibration. Therefore, the design of the blade and the accurate acquisition of the test data are of great importance. At present, all the vibration fatigue tests for testing the blades of the aircraft engines in various domestic colleges are executed according to HB-5277 vibration fatigue test method for the blades and materials of the engines. The method is compiled in 1984 and is suitable for measuring the fatigue performance of the metal blades and materials of the engine under the vibration stress. As the efficiency of the engine is improved year by year, the application proportion of the composite material on the engine is also gradually improved, and HB-5277 is not completely suitable for the vibration fatigue test of the composite material blade.

HB-5277 "Engine blade Flat and Material vibration fatigue test method" stipulates that the blade is excited by a fixed blade tip amplitude to reach a fixed stress level until the blade fails in advance or goes beyond by calibrating the linear proportional relationship between the blade tip amplitude of a metal material blade and the maximum stress of the blade.

Disclosure of Invention

The inventor carries out fatigue tests on OGV (outlet guide vane) composite material vanes of certain types of engines to find that: if the strain of a strain monitoring point is kept unchanged in most of the blades, the amplitude of the blades is reduced along with the increase of the number of test cycles, the amplitude of the blade tip of the blades and the strain of the monitoring point are in a nonlinear condition, and the blade tip amplitude initially calibrated cannot be used as a control quantity to excite the blades for a long time.

In view of at least one of the above technical problems, the present disclosure provides a blade vibration fatigue test method and system, a control device, and a storage medium, which can precisely control a vibration fatigue test of a composite blade.

According to one aspect of the present disclosure, there is provided a blade vibration fatigue test method, including:

carrying out vibration harmonic response numerical analysis on the engine blade in the mounting state to determine a low stress gradient region;

and arranging a strain gauge in a low stress gradient area of the engine blade, and using a strain signal of the strain gauge for vibration control to realize strain closed-loop control.

In some embodiments of the present disclosure, the blade vibration fatigue testing method further comprises:

determining the proportional relation between the low stress gradient point and the maximum stress point of the blade;

and (4) according to the proportional relation between the maximum stress point and the low gradient point, converting the given strain value into the strain of the maximum stress point, and recording the fatigue test result and the cycle number.

In some embodiments of the disclosure, the arranging the strain gauge in the low stress gradient region of the engine blade, and the using the strain signal of the strain gauge for vibration control includes:

arranging a plurality of strain gauges in a low stress gradient area of an engine blade, and collecting multi-path strain signals;

and (4) screening optimal strain data in real time as a control feedback signal by adopting a multipoint minimum standard deviation control mode.

In some embodiments of the disclosure, the arranging the strain gauge in the low stress gradient region of the engine blade, and using the strain signal of the strain gauge for vibration control further includes:

and comparing the control feedback signal with the previous round of control signal to generate a current round of control signal so as to realize strain closed-loop control.

In some embodiments of the present disclosure, the selecting, in real time, optimal strain data as a control feedback signal by using a multipoint minimum standard deviation control method includes:

for each strain gauge, determining an average strain value and a standard deviation of strain signals acquired for multiple times in a preset time period;

and selecting the strain data corresponding to the strain gauge with the minimum standard deviation as a strain control feedback signal.

In some embodiments of the present disclosure, after determining, for each strain gauge, an average strain value and a standard deviation of strain signals acquired a plurality of times within a predetermined time period, the blade vibration fatigue test method further includes:

judging whether a plurality of strain gauges have dead spots or not;

under the condition that dead spots exist in a plurality of strain gauges, the dead spots are removed, and then the step of determining the average strain value and the standard deviation of the strain signals acquired for multiple times in a preset time period is executed for each strain gauge;

and when no defect point exists in the plurality of strain gauges, selecting the strain data corresponding to the strain gauge with the minimum standard deviation as a strain control feedback signal.

In some embodiments of the present disclosure, the determining whether there is a dead pixel in the plurality of strain gauges includes:

determining a strain signal value of each strain gauge and a strain signal mean value of all strain points;

for each strain gauge, judging whether the absolute value of the difference value between the strain signal value and the strain signal mean value is greater than a preset threshold value;

under the condition that the absolute value of the difference value between the strain signal value of one strain gauge and the mean value of the strain signals is greater than a preset threshold value, judging that the strain gauge is a dead pixel;

and under the condition that the absolute value of the difference value between the strain signal value of each strain gauge and the mean value of the strain signals is not greater than a preset threshold value, judging that no dead pixel exists in the plurality of strain gauges.

In some embodiments of the present disclosure, the blade vibration fatigue testing method further comprises:

controlling a vibration table to perform a low-magnitude sine frequency sweep test on the blade, controlling the acceleration of the table top, measuring the natural frequency of the blade, and setting the frequency band range of a band-pass filter;

and controlling the vibration table to apply a low-magnitude fixed-frequency vibration test to the blade to observe the signal quality after filtering.

In some embodiments of the present disclosure, the blade vibration fatigue testing method further comprises:

and controlling the vibration table to gradually load exciting force, carrying out a resonance residence test under the condition that the control point strain of the blade reaches a given strain value, and starting cycle counting.

In some embodiments of the present disclosure, the blade vibration fatigue testing method further comprises:

monitoring the change of the resonant frequency of the blade, adjusting the excitation frequency of the vibration table to be consistent with the resonant frequency of the blade in real time under the condition that the blade structure is damaged, and controlling the strain to be kept in a given strain value state by adjusting the excitation energy of the vibration table.

In some embodiments of the present disclosure, the blade vibration fatigue testing method further comprises:

recording the current vibration cycle times under the condition that the vibration exciting frequency of the vibration table is reduced to the set failure criterion frequency of the blade with cracks and the blade failure, and controlling the vibration table to stop working;

and under the condition that the current vibration cycle number reaches a given target cycle number but the resonance frequency is not reduced to the failure criterion frequency, controlling the vibration table to automatically stop.

According to another aspect of the present disclosure, there is provided a control apparatus including:

the low stress gradient region determining module is used for carrying out vibration harmonic response numerical analysis on the engine blade in the mounting state and determining a low stress gradient region;

and the closed-loop control module is used for arranging a strain gauge in a low stress gradient area of the engine blade, and using a strain signal of the strain gauge for vibration control to realize strain closed-loop control.

In some embodiments of the present disclosure, the control device is configured to perform operations for implementing the blade vibration fatigue test method according to any of the embodiments described above.

According to another aspect of the present disclosure, there is provided a control apparatus including:

a memory to store instructions;

a processor for executing the instructions to cause the control device to perform operations to implement the blade vibration fatigue test method according to any of the embodiments described above.

According to another aspect of the present disclosure, there is provided a blade vibration fatigue testing system, including the control device according to any one of the above embodiments.

In some embodiments of the present disclosure, the blade vibration fatigue test system further includes a test fixture, a vibration table, a power amplifier, a signal generator, a strain conditioning front end, and a data collector.

In some embodiments of the present disclosure, the strain conditioning front end comprises a bridge, a strain amplifier, and a band pass filter.

According to another aspect of the present disclosure, a computer-readable storage medium is provided, wherein the computer-readable storage medium stores computer instructions which, when executed by a processor, implement the blade vibration fatigue testing method according to any of the above embodiments.

According to the method, the strain signal can be stably controlled for a long time through low-gradient strain monitoring, the testing precision and stability of the test are greatly improved, and the strain closed-loop control fatigue test method is more suitable for the fatigue test of the composite material blade.

Drawings

In order to more clearly illustrate the embodiments of the present disclosure or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present disclosure, and other drawings can be obtained by those skilled in the art without creative efforts.

FIG. 1 is a schematic diagram of HB-5277 metal material vibration fatigue test.

FIG. 2 is a schematic view of some embodiments of a blade vibration fatigue testing system of the present disclosure.

FIG. 3 is a schematic view of some embodiments of a blade vibration fatigue testing method of the present disclosure.

FIG. 4 is a schematic illustration of a first order stress distribution cloud for a composite blade according to some embodiments of the present disclosure.

FIG. 5 is a schematic diagram of a multi-point minimum standard deviation control method in some embodiments of the present disclosure.

FIG. 6 is a schematic view of additional embodiments of a blade vibration fatigue testing method of the present disclosure.

FIG. 7 is a schematic diagram of some embodiments of control devices of the present disclosure.

FIG. 8 is a schematic view of other embodiments of a control device of the present disclosure.

Detailed Description

The technical solutions in the embodiments of the present disclosure will be clearly and completely described below with reference to the drawings in the embodiments of the present disclosure, and it is obvious that the described embodiments are only a part of the embodiments of the present disclosure, and not all of the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. All other embodiments, which can be derived by a person skilled in the art from the embodiments disclosed herein without making any creative effort, shall fall within the protection scope of the present disclosure.

The relative arrangement of the components and steps, the numerical expressions, and numerical values set forth in these embodiments do not limit the scope of the present disclosure unless specifically stated otherwise.

Meanwhile, it should be understood that the sizes of the respective portions shown in the drawings are not drawn in an actual proportional relationship for the convenience of description.

Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail but are intended to be part of the specification where appropriate.

In all examples shown and discussed herein, any particular value should be construed as merely illustrative, and not limiting. Thus, other examples of the exemplary embodiments may have different values.

It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, further discussion thereof is not required in subsequent figures.

FIG. 1 is a schematic diagram of HB-5277 metal material vibration fatigue test. The control mode adopted in fig. 1 is single-point amplitude control, and the blade is excited by using the fixed blade tip amplitude to reach the fixed stress level until the blade fails in advance or goes out by calibrating the linear proportional relationship between the blade tip amplitude of the metal material blade and the maximum stress of the blade.

The inventor conducts fatigue test on OGV composite material blades of certain engines, and finds that the composite material blades have the condition that the blade tip amplitude and the strain of a monitoring point show a nonlinear proportional relationship along with the increase of the fatigue cycle times in the high-cycle fatigue test process, and the initially calibrated amplitude can not be used as the vibration control input any more, so that the condition that fatigue test control is conducted by monitoring the blade tip amplitude of the blades in HB-5277 engine blade plane and material vibration fatigue test method is not suitable for the fatigue test of the composite material blades any more. The present disclosure needs to develop a vibration fatigue test method suitable for accurately controlling a composite blade.

The present disclosure proposes to replace the tip amplitude control method in HB5277 by a strain closed-loop control method, which faces many difficulties: firstly, the maximum strain of a stress concentration area is difficult to accurately measure, and the strain at the position is large, so that the service life of a strain gauge is short, and the strain gauge cannot be used for long-time fatigue test control; secondly, the strain gauge is not as stable as an acceleration sensor, a laser displacement sensor and the like, is easy to damage, and generates the condition of sudden change of strain data, thereby causing test error control; thirdly, the layering composite material blade is easy to delaminate but still does not lose efficacy, and the surface strain at the delamination part is gradually reduced; and fourthly, after the strain gauge is electrified, even if the test piece is not subjected to external force, the strain can be gradually increased along with the increase of time, thereby realizing the zero drift phenomenon. And fifthly, when the composite material blade fatigue test is carried out, the strain signal is found to contain higher-order harmonic components of a plurality of excitation frequencies, so that the measured strain is much higher than the actual strain value, and the strain signal is distorted due to zero drift or the higher-order harmonic components.

In view of at least one of the above technical problems, the present disclosure provides a blade vibration fatigue test method and system, a control device, and a storage medium, and the present disclosure is explained by the above embodiments of the present disclosure.

FIG. 2 is a schematic view of some embodiments of a blade vibration fatigue testing system of the present disclosure. As shown in fig. 2, the blade vibration fatigue test system of the present disclosure may include a test fixture 11, a vibration table 12, a power amplifier 13, a signal generator 14, a strain conditioning front end 15, a data collector 16, and a control device 17, wherein:

in some embodiments of the present disclosure, the vibration fatigue test may be a test for acquiring vibration parameters of a test piece, such as fatigue limit, fatigue life, and the like.

At present, a data acquisition unit 16 used with a vibration table 12 does not have a function of directly acquiring strain, so a signal conditioning front end 15 is required to amplify a weak strain signal into a voltage signal for the data acquisition unit to read.

In some embodiments of the present disclosure, as shown in fig. 2, the strain conditioning front end 15 may include a bridge 151, a strain amplifier 152, and a band pass filter 153, wherein:

in some embodiments of the present disclosure, the bridge 151 may be a measuring bridge, which may be a wheatstone bridge, with different bridge connections (1/4 bridge, half bridge, or full bridge) being selected as desired. The bridge 151 converts the strain gauge deformation into an electrical signal, and the electrical signal generated due to the small strain gauge deformation is weak, so that the weak electrical signal needs to be amplified by the strain amplifier 152. The gain output voltage of the strain amplifier 152 should satisfy the operating voltage (5V to 10V) of the data collector. The strain amplifier 152 should have independent multi-path amplification circuitry to measure multiple channel strain data simultaneously.

In some embodiments of the present disclosure, the band pass filter 153 may be an analog band pass filter. The analog band-pass filter is used for filtering out a zero drift low-frequency signal of the strain gauge, a high-order harmonic signal of an excitation frequency and high-frequency noise interference in a circuit, and the accuracy of strain measurement is guaranteed.

In some embodiments of the disclosure, the filtering mode suggests selecting a butterworth filter with more than 3 orders, the upper limit and the lower limit of the filtering frequency are based on the excitation frequency, the upper limit is at least capable of filtering out second-order harmonic components of the excitation frequency, the lower limit is capable of filtering out zero-drift low-frequency signals, and meanwhile, an external display terminal observes a strained spectrum curve to adjust the filtering bandwidth to eliminate interference signals.

As shown in FIG. 2, the blade 18 to be tested may be a composite blade.

As shown in FIG. 2, in the present disclosure, a plurality of strain gauges 19 are arranged in a low stress gradient region of a composite material blade, a proportional relationship between a low stress gradient point and a maximum stress point of the blade is obtained by utilizing finite element harmonic response calculation, and the composite material blade 18 is rigidly fixed on the vibration table 12 through a clamp 11.

The strain amplifier 152 is configured to amplify weak multi-path strain signals into multi-path voltage signals that can be received by the data acquisition unit 16, screen optimal strain data in real time as a control feedback signal by using a multi-point minimum standard deviation control method, compare the optimal strain data with a previous round of control signal to generate a current round of control signal Ci, and input the control signal Ci to the vibration table 12 after passing through the signal generator 14 and the power amplifier 13, thereby implementing strain closed-loop control.

In some embodiments of the present disclosure, closed-loop control refers to a control relationship in which the output being controlled is returned to the input being controlled in a manner and exerts a controlling influence on the input.

Based on the blade vibration fatigue test system provided by the embodiment of the disclosure, aiming at the problem that the amplitude strain relationship in the composite material blade fatigue test presents nonlinearity along with the increase of the test period, the strain closed-loop control method is provided to replace the blade tip amplitude control method in HB5277, and the vibration fatigue test system of the strain closed-loop control is established.

The structure and function of each component module in the blade vibration fatigue testing system of the disclosure in the embodiment of fig. 2 are described below with reference to the embodiments of the blade vibration fatigue testing method and the control device of the disclosure.

FIG. 3 is a schematic view of some embodiments of a blade vibration fatigue testing method of the present disclosure. Preferably, the present embodiment may be performed by the blade vibration fatigue test system of the present disclosure or the control device of the present disclosure. The method may comprise the steps 31 and 32, wherein:

and 31, carrying out vibration harmonic response numerical analysis on the engine blade in the mounting state, and determining a low stress gradient region.

In some embodiments of the present disclosure, step 31 may comprise: and (3) carrying out vibration harmonic response numerical analysis on the composite material blade in the mounting state to obtain a stress distribution cloud chart of the blade, selecting a low stress gradient region, and obtaining the proportional relation between the maximum stress point and the low gradient point according to the low gradient point strain equivalent conversion, wherein the low stress gradient region is shown in figure 4.

FIG. 4 is a schematic illustration of a first order stress distribution cloud for a composite blade according to some embodiments of the present disclosure. As shown in fig. 4, the maximum strain point is at the leading edge root position (position 1), where the stress gradient is large, and if a strain gage is placed there, the stress measured is actually an average stress value. To avoid the above situation, the strain gauge is arranged at the position 2 of the second largest region with small gradient, and the strain value of the region 2 is controlled below 2000 mu epsilon, so as to ensure the service life (> 3 multiplied by 10) of the strain gauge under the environment of high cycle fatigue load⁷Number of cycles). And (3) obtaining a strain proportion coefficient k of the position 1 and the position 2 and a strain epsilon of the tested and measured position 2 through finite element numerical simulation calculation, and converting an actual maximum stress value epsilon' at the position 1 into a formula (1).

ε′＝kε (1)

And 32, arranging a strain gauge in a low stress gradient area of the engine blade, and using a strain signal of the strain gauge for vibration control to realize strain closed-loop control.

In some embodiments of the present disclosure, step 32 may comprise: step 321 and step 322, wherein:

step 321, arranging a plurality of strain gauges in a low stress gradient area of the engine blade, and collecting multi-path strain signals.

And 322, screening optimal strain data in real time as a control feedback signal in a multipoint minimum standard deviation control mode.

FIG. 5 is a schematic diagram of a multi-point minimum standard deviation control method in some embodiments of the present disclosure. As shown in fig. 5, the multipoint minimum standard deviation control method (e.g., step 322) of the present disclosure may include:

for each strain gauge, an average strain value and a standard deviation of the strain signals acquired a plurality of times within a predetermined time period are determined, step 51.

In some embodiments of the present disclosure, step 51 may comprise: arranging a plurality of strain gauges in a region with small strain gradient (such as a region 2 in FIG. 4), and selecting M strain gauges as monitoring points; the strain values of the monitoring points are basically consistent or have small relative deviation, and the strain measurement value of the monitoring points is recorded as epsilon_iCalculating the average strain of each strain signal in the previous delta t time in real time(see equations (2), (3)) and the standard deviation σ_i(see equation (4)).

In the formula (2), N is the number of points collected by the ith strain channel within a preset time period delta t;average strain of the ith strain channel in the time delta t; epsilon_ijThe real-time strain of the ith strain channel in the j time is obtained.

N＝f_s×Δt (3)

In the formula (3), f_sIs the sampling frequency.

And step 52, judging whether the plurality of strain gauges have bad points or not. If there is a dead spot in the plurality of strain gauges, go to step 53; otherwise, in the case where there is no bad spot in the plurality of strain gauges, step 54 is performed.

In some embodiments of the present disclosure, the step 52 may include: determining the strain signal value of each strain gauge at the current moment and the strain signal mean value of all strain points; for each strain gauge, judging whether the absolute value of the difference value between the strain signal value and the strain signal mean value is greater than a preset threshold value; under the condition that the absolute value of the difference value between the strain signal value of one strain gauge and the mean value of the strain signals is greater than a preset threshold value, judging that the strain gauge is a dead pixel; and under the condition that the absolute value of the difference value between the strain signal value of each strain gauge and the mean value of the strain signals is not greater than a preset threshold value, judging that no dead pixel exists in the plurality of strain gauges.

In some embodiments of the present disclosure, the step 52 may include: before generating the control signal at the next moment, strain dead spots (poor contact, broken connecting lines, infirm sticking and the like) which possibly occur need to be removed, and strain channels do not enter the subsequent strain control signal screening range any more after the strain dead spots are removed. The principle of dead pixel judgment can be the PauTa criterion, see formula (5).

Because the strain change degree of the low-gradient region of the blade is very small, each path of strain can be approximately considered to be in the same stress level, the monitoring strain can be influenced by factors such as control and interference and has small-amplitude change, and the monitoring strain belongs to random variables. According to the PauTa criterion, when the residual error of a sample follows a normal distribution, the probability of the occurrence of the sample with the error greater than 3 sigma is less than 0.003, and the sample can be considered as a dead pixel in the data. Whereby a strain channel x that exceeds the 3 sigma criterion can be assigned_iAnd eliminating the channel, and taking the channel out of the monitoring strain. The judgment criterion is shown in formula (5):

x if formula (5) is satisfied_iFor bad spots, it should be removed.

In equation (5):for M channel strains x_iThe mean value of (a); σ is M channel strain x_iStandard deviation of (2).

In step 53, the dead pixel is removed, and then step 51 is executed.

Step 54, for each strain gauge, judging the standard deviation sigma of the strain signal of the strain gauge_iWhether or not it is the minimum standard deviation. Standard deviation sigma of strain signal in the strain gauge_iIn the case of the minimum standard deviation, step 55 is executed; otherwise, the standard deviation sigma of the strain signal in the strain gauge_iIn the case where it is not the minimum standard deviation, step 56 is performed.

And step 55, participating in control, namely selecting the strain data corresponding to the strain gauge with the minimum standard deviation as a strain control feedback signal.

And step 56, participating in monitoring. That is, the strain signal of the strain gauge is continuously monitored.

The above embodiments of the present disclosure may dynamically select the strain data with the minimum standard deviation of the strain monitoring points as the strain control signal. According to the embodiment of the disclosure, the control strain selected each time can be always the channel with the minimum strain fluctuation through the method of minimum standard deviation strain control, and if the current control strain performance is unstable or damaged, the embodiment of the disclosure can dynamically select the most stable strain channel in real time to replace, so that the overall control of the system is not influenced, and the stability of test control is greatly improved. If the strain is controlled in a single point by adopting the traditional method, once the strain gauge is damaged, the vibration controller may continue the test by taking the wrong strain value as the control, and the accuracy of the test is greatly influenced.

Aiming at the characteristics that a strain gauge is short in service life and easy to damage and unstable in performance and the layering problem of a layered composite material is easy to occur, the embodiment of the disclosure provides a multi-point minimum standard deviation control method and a low gradient point strain equivalent conversion method, and long-term stable control on a strain signal can be realized through three aspects of minimum strain standard deviation control, low gradient strain monitoring and dead point elimination, so that the test precision and stability of the test are greatly improved.

FIG. 6 is a schematic view of additional embodiments of a blade vibration fatigue testing method of the present disclosure. Preferably, the present embodiment may be performed by the blade vibration fatigue test system of the present disclosure or the control device of the present disclosure. The method may comprise steps 61-67, wherein:

and 61, carrying out vibration harmonic response numerical analysis on the engine blade in the mounting state, and determining a low stress gradient area.

In some embodiments of the present disclosure, step 61 may comprise: and (3) carrying out vibration harmonic response numerical analysis on the composite material blade in the mounting state to obtain a stress distribution cloud chart of the blade, selecting a low stress gradient area, and obtaining a proportional relation between the maximum stress point and the low gradient point according to low gradient point strain equivalent conversion as shown in fig. 4.

And step 62, arranging a strain gauge in a low stress gradient area of the engine blade.

In some embodiments of the present disclosure, step 62 may comprise: a plurality of strain gauges are adhered to a selected low stress gradient area of the blade, as shown in fig. 4, the blade is rigidly fixed on a vibration table 12 through a clamp, a lead of the strain gauge is connected to a strain conditioning front end 15, and a strain amplifier 152 amplifies weak multi-path strain signals into voltage signals which can be received by a vibration controller.

And step 63, controlling the vibration table 12 to perform a low-magnitude sine frequency sweep test on the blade.

In some embodiments of the present disclosure, step 63 may comprise: the control device controls the vibration table 12 to perform low-magnitude sine frequency sweep test on the blade, controls the acceleration of the table top, measures the natural frequency of the blade, sets the frequency band range of the band-pass filter 153, and suggests that the frequency range is +/-20% of the excitation natural frequency; meanwhile, the vibration table 12 applies a low-magnitude fixed-frequency vibration test to observe the signal quality after filtering.

And step 64, using the strain signal of the strain gauge for vibration control to realize strain closed-loop control.

In some embodiments of the present disclosure, step 64 may comprise: the control device controls the vibration table 12 to carry out sinusoidal excitation at the natural frequency of the composite material blade, the control point is the low-gradient region strain of the blade, and the multi-path strain signals are monitored simultaneously; by adopting a multipoint minimum standard deviation control method, as shown in fig. 5, optimal strain data is screened in real time to serve as a control feedback signal and is compared with a previous round of control signal to generate a current round of control signal Ci, the control signal is transmitted to a signal generator by a control device and is input to a vibration table 12 after passing through a power amplifier 13, and strain closed-loop control is realized; the vibration table 12 is gradually loaded with an exciting force, and when the control point strain of the blade reaches a given strain value, a resonance dwell test is performed, and cycle counting is started.

In step 65, the blade resonance frequency is monitored for changes.

In some embodiments of the present disclosure, step 65 may comprise: monitoring the change of the resonant frequency of the blade, wherein when the blade structure is damaged, the natural frequency of the blade structure is reduced, and the control device adjusts the excitation frequency of the vibration table 12 to be consistent with the resonant frequency of the blade in real time; and controlling the strain to be kept in a given strain value state by adjusting the excitation energy of the vibration table 12.

And step 66, recording the current vibration cycle number.

In some embodiments of the present disclosure, step 66 may include: when the excitation frequency of the vibration table 12 is reduced to a set criterion of crack occurrence and blade failure of the composite material blade, the control device records the current vibration cycle number and stops the vibration table 12; when the given target number of cycles is reached, but the resonant frequency does not drop to the failure criterion frequency, the machine is automatically stopped.

Step 67, determine the strain at the point of maximum stress.

In some embodiments of the present disclosure, step 67 may comprise: and (4) calculating the strain of the maximum stress point according to the proportional relation between the maximum stress point and the low gradient point by the given strain value, recording the fatigue test result and the cycle number, and repeating the steps 62 to 66 to perform the fatigue test of the next blade.

The embodiment of the disclosure provides a strain closed-loop control fatigue test and a method suitable for a composite material blade, and the vibration fatigue test of the composite material blade can be more accurately carried out.

According to the embodiment of the disclosure, the whole-course strain closed-loop control can be realized, unattended operation in a test can be realized, and the test effect is improved.

The embodiment of the disclosure provides a minimum standard deviation control method and a low gradient point strain equivalent conversion method, so that the test precision of the test is greatly improved.

The strain closed-loop control fatigue test method disclosed by the embodiment of the disclosure has universality and is also suitable for metal material blades.

The strain closed-loop control fatigue test method disclosed by the embodiment of the disclosure can be suitable for a vibration fatigue test of an engine blade (such as an aircraft engine blade).

FIG. 7 is a schematic diagram of some embodiments of control devices of the present disclosure. As shown in fig. 7, a control apparatus of the present disclosure (e.g., the control apparatus 17 of the embodiment of fig. 2) may include a low stress gradient region determination module 171 and a closed-loop control module 172, wherein:

the low stress gradient region determination module 171 is configured to perform a vibration harmonic response numerical analysis on the engine blade in the mounted state to determine a low stress gradient region.

And the closed-loop control module 172 is used for arranging a strain gauge in a low stress gradient region of the engine blade, and using a strain signal of the strain gauge for vibration control to realize strain closed-loop control.

In some embodiments of the present disclosure, the closed-loop control module 172 may be configured to arrange a plurality of strain gauges in a low stress gradient region of the engine blade, and collect multiple strain signals; adopting a multipoint minimum standard deviation control mode to screen optimal strain data in real time as a control feedback signal; and comparing the control feedback signal with the previous round of control signal to generate a current round of control signal so as to realize strain closed-loop control.

In some embodiments of the present disclosure, the closed-loop control module 172 may be configured to determine, for each strain gauge, an average strain value and a standard deviation of a strain signal acquired multiple times within a predetermined time period, in a multi-point minimum standard deviation control manner, and in a real-time screening of optimal strain data as a control feedback signal; judging whether a plurality of strain gauges have dead spots or not; under the condition that bad spots exist in a plurality of strain gauges, the bad spots are removed, and then the operation of determining the average strain value and the standard deviation of the strain signals acquired for multiple times in a preset time period for each strain gauge is executed; and when no defect point exists in the plurality of strain gauges, selecting the strain data corresponding to the strain gauge with the minimum standard deviation as a strain control feedback signal.

In some embodiments of the present disclosure, the closed-loop control module 172, in determining whether there is a dead spot in the plurality of strain gauges, may be configured to determine a strain signal value of each strain gauge and a strain signal mean of all strain points; for each strain gauge, judging whether the absolute value of the difference value between the strain signal value and the strain signal mean value is greater than a preset threshold value; under the condition that the absolute value of the difference value between the strain signal value of one strain gauge and the mean value of the strain signals is greater than a preset threshold value, judging that the strain gauge is a dead pixel; and under the condition that the absolute value of the difference value between the strain signal value of each strain gauge and the mean value of the strain signals is not greater than a preset threshold value, judging that no dead pixel exists in the plurality of strain gauges.

In some embodiments of the present disclosure, the control device of the present disclosure may also be used to control the vibration table to perform a low-magnitude sine frequency sweep test on the blade, control the acceleration of the table, measure the natural frequency of the blade, and set the frequency band range of the band-pass filter; and controlling the vibration table to apply a low-magnitude fixed-frequency vibration test to the blade to observe the signal quality after filtering.

In some embodiments of the present disclosure, the control device of the present disclosure may further be configured to control the vibration table to gradually load an excitation force, and perform a resonance dwell test to start cycle counting when the control point strain of the blade reaches a given strain value.

In some embodiments of the present disclosure, the control device of the present disclosure may also be configured to monitor changes in the resonant frequency of the blade, adjust the excitation frequency of the vibration table to be consistent with the resonant frequency of the blade in real time in the event of structural damage to the blade, and maintain the control strain in a given strain value state by adjusting the excitation energy of the vibration table.

In some embodiments of the disclosure, the control device of the disclosure may be further configured to record the current vibration cycle number and control the vibration table to stop working when the vibration excitation frequency of the vibration table is reduced to a set failure criterion frequency for cracking of the blade and failure of the blade; and under the condition that the current vibration cycle number reaches a given target cycle number but the resonance frequency is not reduced to the failure criterion frequency, controlling the vibration table to automatically stop.

In some embodiments of the present disclosure, the control device may be configured to perform operations for implementing the blade vibration fatigue testing method according to any of the embodiments described above (e.g., any of fig. 3-6).

The above embodiments of the present disclosure may dynamically select the strain data with the minimum standard deviation of the strain monitoring points as the strain control signal. According to the embodiment of the disclosure, the control strain selected each time can be always the channel with the minimum strain fluctuation through the method of minimum standard deviation strain control, and if the current control strain performance is unstable or damaged, the embodiment of the disclosure can dynamically select the most stable strain channel in real time to replace, so that the overall control of the system is not influenced, and the stability of test control is greatly improved. If the strain is controlled in a single point by adopting the traditional method, once the strain gauge is damaged, the vibration controller may continue the test by taking the wrong strain value as the control, and the accuracy of the test is greatly influenced.

According to the embodiment of the disclosure, a plurality of strain gauges can be arranged in the low stress gradient area of the composite material blade, and the optimal strain data is screened in real time as a control feedback signal in the modes of low gradient point strain equivalent conversion, minimum strain standard deviation control and dead pixel elimination, so that strain closed-loop control is realized.

FIG. 8 is a schematic view of other embodiments of a control device of the present disclosure. As shown in fig. 8, a control apparatus of the present disclosure (e.g., control apparatus 17 of the embodiment of fig. 2) may include a memory 178 and a processor 179, wherein:

memory 178 for storing instructions.

A processor 179 for executing the instructions to cause the control device 17 to perform operations for implementing the blade vibration fatigue testing method as described in any of the embodiments above (e.g., any of the embodiments of fig. 3-6).

Aiming at the characteristics that a strain gauge is short in service life and easy to damage and unstable in performance and the layering problem of a layered composite material is easy to occur, the embodiment of the disclosure provides a multi-point minimum standard deviation control method and a low gradient point strain equivalent conversion method, and long-term stable control on a strain signal can be realized through three aspects of minimum strain standard deviation control, low gradient strain monitoring and dead point elimination, so that the test precision and stability of the test are greatly improved.

According to another aspect of the present disclosure, a computer-readable storage medium is provided, wherein the computer-readable storage medium stores computer instructions, which when executed by a processor, implement the blade vibration fatigue testing method according to any of the embodiments described above (e.g., any of the embodiments of fig. 3-6).

The embodiment of the disclosure provides a strain closed-loop control fatigue test mode suitable for the composite material blade, and the vibration fatigue test of the composite material blade can be more accurately carried out.

According to the embodiment of the disclosure, the whole-course strain closed-loop control can be realized, unattended operation in a test can be realized, and the test effect is improved.

The embodiment of the disclosure can utilize a minimum standard deviation control method and a low gradient point strain equivalent conversion method, thereby greatly improving the test precision of the test.

The strain closed-loop control fatigue test method disclosed by the embodiment of the disclosure has universality and is also suitable for metal material blades.

The above-described embodiments of the present disclosure may be applicable to vibration fatigue testing of engine blades (e.g., aircraft engine blades).

The control devices described above may be implemented as a general purpose processor, a Programmable Logic Controller (PLC), a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any suitable combination thereof, for performing the functions described herein.

Thus far, the present disclosure has been described in detail. Some details that are well known in the art have not been described in order to avoid obscuring the concepts of the present disclosure. It will be fully apparent to those skilled in the art from the foregoing description how to practice the presently disclosed embodiments.

It will be understood by those skilled in the art that all or part of the steps for implementing the above embodiments may be implemented by hardware, or may be implemented by a program instructing relevant hardware to implement the above embodiments, where the program may be stored in a computer-readable storage medium, and the above-mentioned storage medium may be a read-only memory, a magnetic disk, an optical disk, or the like.

The description of the present disclosure has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the disclosure in the form disclosed. Many modifications and variations will be apparent to practitioners skilled in this art. The embodiment was chosen and described in order to best explain the principles of the disclosure and the practical application, and to enable others of ordinary skill in the art to understand the disclosure for various embodiments with various modifications as are suited to the particular use contemplated.