Fatigue test device for engine blade

Abstract

The invention provides a fatigue test device for an engine blade, which is used for applying non-interfering high and low cycle combined loads to the engine blade to simulate a fatigue load borne by the engine blade during working, and comprises a vacuum test cabin, an engine blade, a first driving device, a second driving device, a third driving device, a fourth driving device and a fourth driving device, and is characterized in that the engine blade is rotatably hung at the top of the vacuum test cabin; the actuator comprises laminated piezoelectric patches which are adhered to a plurality of preset positions on the surface of the engine blade, and each laminated piezoelectric patch on the preset position comprises a plurality of layers of piezoelectric patches which are electrically connected in parallel; the laminated piezoelectric patch array is externally connected with a power supply so as to apply a target excitation vibration mode to the engine blade while the engine blade rotates; and the vibration meter is used for collecting and feeding back the vibration response of the engine blade so as to execute the fatigue test analysis of the engine blade.

Description

TECHNICAL FIELD

[0001] The present application relates to an engine blade test device, in particular to a fatigue test device for an engine blade. BACKGROUND

[0002] In an aero-engine, the fan blade is the first component of the front end of the large-bypass-ratio turbofan engine, and its fatigue fracture failure is one of the common failure faults of the engine. The fan blade fracture failure will directly affect the normal operation of the engine and even endanger the flight safety. In the process of take-off-cruise-landing of the airplane, the fan blade simultaneously bears a large amplitude and low frequency periodic load (i.e. low cycle load) caused by the rotating centrifugal force, and a high frequency and small amplitude vibration load (i.e. high cycle load) caused by system vibration and instantaneous airflow disturbance. The two kinds of loads simultaneously act on the fan blade, which is different from the pure low cycle load or the pure high cycle load, and generates a fatigue effect caused by the high-low cycle combined load, i.e. high-low cycle fatigue. Therefore, the high cycle fatigue or the low cycle fatigue alone as the basis for the blade strength design and life estimation cannot effectively reflect the damage of the blade in the actual work, and the high-low cycle fatigue must be taken as the basis for the strength design and life estimation.

[0003] The airworthiness regulations of the civil aviation engine have clearly stated that the life evaluation must include the combined effect of the high cycle fatigue and the low cycle fatigue, and the blade fatigue test result is the main basis for determining the blade life. Since it is difficult to accurately simulate the combined stress environment of the high cycle fatigue and the low cycle fatigue of the fan blade in the work, there is an urgent need for an exciting mode which can flexibly simulate the real working environment of the blade, can provide the exciting load varying with space and time to the blade, and the exciting load and the blade rotating speed are independent of each other and are not affected by the blade rotating speed.

[0004] The existing technology generally applies periodic excitation to the rotating blade through oil or gas as the exciting medium to achieve the test purpose of exciting the fan blade. However, this method will cause the high cycle load to be coupled with the rotating speed of the blade, and when the gas excitation or liquid excitation is applied to the blade, the original vacuum environment will be destroyed, resulting in rotating speed fluctuation, which will also affect the actual loading effect. Another exciting mode which can effectively apply the low cycle load and the high cycle load to the blade without interference is to use piezoelectric patches, but the problem is that in order to obtain a higher exciting force, the input voltage of the single-layer piezoelectric patch needs to be adjusted to close to the maximum value, even up to 1500V. However, it is found in the test that such high voltage will cause electromagnetic interference to the surrounding equipment, resulting in that the strain gauge used for vibration measurement cannot work normally, and the MFC power supply slide ring is easily broken down, which causes trouble to the test.

[0005] In order to overcome the above-mentioned defects of the prior art, the technical field urgently needs a fatigue test device for engine blades for applying high-low cycle composite loads that do not interfere with each other to the engine blades to simulate the fatigue loads suffered by the engine blades during operation, and by reasonably designing the output loads of each excitation point, the required output excitation of a single excitation point can be effectively reduced, the required external voltage input is further reduced, the occurrence of electromagnetic interference is reduced, and the test is more accurate. SUMMARY

[0006] The following presents a simplified summary of one or more aspects in order to provide a basic understanding of such aspects. This summary is not an extensive overview of all contemplated aspects, and is intended to neither identify key or critical elements of all aspects nor delineate the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that is presented later.

[0007] In order to overcome the above-mentioned defects of the prior art, the present application provides a fatigue test device for engine blades for applying high-low cycle composite loads that do not interfere with each other to the engine blades to simulate the fatigue loads suffered by the engine blades during operation, the fatigue test device comprising: a vacuum test chamber, the engine blades being rotatably hoisted at the top of the vacuum test chamber; an actuator, the actuator comprising a plurality of stacked piezoelectric patches attached to a plurality of predetermined positions on the surface of the engine blades, each stacked piezoelectric patch at the predetermined position comprising a plurality of layers of electrically parallel piezoelectric patches, the stacked piezoelectric patch array being externally connected to a power supply to apply a target excitation mode to the engine blades while rotating; and a vibration meter for collecting and feeding back the vibration response of the engine blades to perform fatigue test analysis of the engine blades.

[0008] In an embodiment, preferably, the plurality of predetermined positions on the surface of the engine blades where the stacked piezoelectric patches are arranged are determined based on strain energy level selection in a blade software simulation target mode cloud map.

[0009] In an embodiment, preferably, the stacked piezoelectric patches are made of composite fiber piezoelectric material, and a plurality of the stacked piezoelectric patches are attached to a plurality of the predetermined positions on the front and back surfaces of the engine blades to form the stacked piezoelectric patch array.

[0010] In an embodiment, preferably, the number of layers of single-layer patches and the size and direction of the output excitation of each of the plurality of stacked piezoelectric patches at the plurality of predetermined positions on the surface of the engine blades are determined according to the different target excitation modes of the engine blades.

[0011] In an embodiment, preferably, the engine blade fatigue test device provided by the present application further comprises a processor, a digital circuit component, an analog signal generator and a power amplifier connected in sequence, wherein the processor outputs a control signal of the engine blade, the control signal is converted into a digital signal by the digital circuit component, and then transmitted to the analog signal generator to be converted into an analog signal, and the analog signal is amplified by the power amplifier and then output to the plurality of laminated piezoelectric patches.

[0012] In an embodiment, preferably, the processor is further configured to compensate and adjust the output of the laminated piezoelectric patches according to the difference between the actual response and the target response of the engine blade collected and fed back by the vibration tester.

[0013] In an embodiment, preferably, the engine blade fatigue test device provided by the present application further comprises a data acquisition component for inputting the vibration signal of the engine blade collected by the vibration tester into the processor after being converted into a digital signal.

[0014] In an embodiment, preferably, the engine blade fatigue test device provided by the present application further comprises a mounting seat, a tool shaft and a plurality of slip rings mounted on the top of the vacuum test chamber, wherein the slip rings are used to transmit electrical signals to the rotating engine blade. BRIEF DESCRIPTION OF DRAWINGS

[0015] The above features and advantages of the present application can be better understood by reading the following detailed description of embodiments of the present application in conjunction with the drawings, in which:

[0016] Figure 1 is a device structure schematic diagram of an engine blade fatigue test device according to an embodiment of the present application.

[0017] For the sake of clarity, a brief description of the reference signs is given below:

[0018] 1 processor

[0019] 2 digital circuit component

[0020] 3 analog signal generator

[0021] 4 power amplifier

[0022] 5 vacuum test chamber

[0023] 6 mounting seat

[0024] 7 static ring mounting frame

[0025] 8 first slip ring

[0026] 9 tool shaft

[0027] 10 Simulated fan discs

[0028] 11 Fan blades

[0029] 12-layer piezoelectric patch

[0030] 13 Strain gauges

[0031] 14 Second slip ring

[0032] 15 Data Acquisition Components

[0033] 16 Strain Acquisition Line

[0034] 17. Signal transmission line Detailed Implementation

[0035] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Although the description of the present invention is presented in conjunction with preferred embodiments, this does not mean that the features of the invention are limited to these embodiments. On the contrary, the purpose of describing the invention in conjunction with embodiments is to cover other options or modifications that may be derived based on the claims of the present invention. To provide a thorough understanding of the invention, many specific details will be included in the following description. The invention may also be implemented without using these details. Furthermore, to avoid confusion or obscuring the focus of the invention, some specific details will be omitted in the description.

[0036] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0037] Furthermore, the terms "upper," "lower," "left," "right," "top," "bottom," "horizontal," and "vertical" used in the following description should be understood as the orientations shown in the relevant paragraphs and accompanying drawings. These relative terms are for illustrative purposes only and do not imply that the described apparatus must be manufactured or operated in a specific orientation, and therefore should not be construed as limiting the invention.

[0038] It is to be understood that, although terms such as "first", "second", "third", etc. can be used herein to describe various components, regions, layers and / or sections, these components, regions, layers and / or sections should not be limited by these terms, and these terms are merely used to distinguish different components, regions, layers and / or sections. Therefore, the first components, regions, layers and / or sections discussed below can be referred to as the second components, regions, layers and / or sections without departing from some embodiments of the present application.

[0039] In order to overcome the above-mentioned defects existing in the prior art, the present application provides a fatigue test device for engine blades, which is used to apply high-low cycle composite loads that do not interfere with each other to the engine blades to simulate the fatigue loads suffered by the engine blades during operation. By reasonably designing the output loads of each excitation point, the required output excitation of a single excitation point can be effectively reduced, the required external voltage can be further reduced, the occurrence of electromagnetic interference phenomenon can be reduced, and the test can be more accurate.

[0040] Figure 1 The device structure schematic diagram of the fatigue test device for engine blades is shown according to an embodiment of the present application.

[0041] Reference can be made in combination with Figure 1 The fatigue test device for engine blades provided by the present application is used to apply high-low cycle composite loads that do not interfere with each other to the engine blades to simulate the fatigue loads suffered by the engine blades during operation. The fatigue test device can include: a vacuum test cabin 5, the engine fan blades 11 can be rotatably hoisted at the top of the vacuum test cabin 5; an actuator, the actuator includes a plurality of stacked piezoelectric patches 12 attached to the surface of the engine fan blades 11 at a plurality of preset positions, each stacked piezoelectric patch 12 at the preset position includes a plurality of electrically connected piezoelectric patches in parallel, and the stacked piezoelectric patch array is connected to an external power supply to apply a target excitation vibration mode to the engine fan blades 11 while rotating; and a vibration measuring instrument, which is used to collect and feedback the vibration response of the engine fan blades 11 to perform fatigue test analysis of the engine fan blades.

[0042] In the fatigue test device for engine blades provided by the present application, a plurality of stacked piezoelectric patches are used to form an array to convert electrical energy into vibration energy, excite the fan blades to vibrate in a preset vibration mode, and simulate high cycle load excitation. The high cycle load and the low cycle load generated by the rotation of the fan blades together can successfully simulate the high-low cycle composite load excitation suffered by the fan blades in the working state. The piezoelectric laminated patch is composed of a plurality of piezoelectric patches connected in electrical parallel. Therefore, under the condition that the output excitation force is the same, the required external voltage of the stacked piezoelectric patch is significantly lower than the required voltage of the single-layer piezoelectric patch, which can be as low as Meanwhile, the use of the laminated piezoelectric patch array causes the fan blade to be excited at multiple points, and by reasonably designing the output load of each exciting point, the output excitation required by a single exciting point can be effectively reduced, further reducing the external voltage required for input and reducing the occurrence of electromagnetic interference.

[0043] In a preferred embodiment, the plurality of preset positions on the surface of the engine blade at which the laminated piezoelectric patch is arranged are determined based on the strain energy level in the target mode shape cloud map obtained by blade software simulation.

[0044] Before the test, simulation analysis is performed to determine the blade mode shape that needs to be focused on in the engine operating speed range, for example, the first two modes are generally the main modes. According to the simulation results, the laminated patch can be installed at the position with large strain energy in the mode shape during the test, so as to make the amplitude of the target mode shape reach the amplitude required for fatigue test. Preferably, the patch takes into account the characteristics of the first and second modes at the same time, and the patch position is not adjusted during the process from low speed to high speed. However, the excitation output by each laminated patch can be adjusted for the first mode and the second mode, respectively.

[0045] Preferably, in an embodiment, the engine blade fatigue test device provided by the present application comprises a plurality of laminated piezoelectric patches made of composite fiber piezoelectric material, and the plurality of laminated piezoelectric patches are respectively attached to the plurality of preset positions on the front and back surfaces of the engine blade to form the laminated piezoelectric patch array.

[0046] The laminated piezoelectric patch can be composed of a plurality of layers of piezoelectric material with high electromechanical coupling performance, and preferably, composite fiber piezoelectric material can be used. Composite fiber piezoelectric material is a new type of smart material that takes into account both performance and applicability. On the one hand, it has good flexibility; on the other hand, it has stronger actuation effect than piezoelectric polymers and even piezoelectric ceramics, can load a larger range of actuation voltage, and has the advantages of high output frequency response, fast dynamic response, large load, stable performance, no heating, no noise, and small external force interference. The laminated composite fiber piezoelectric patch not only has similar advantages to the single-layer fiber piezoelectric patch in terms of dynamic response characteristics, but also requires a smaller voltage to achieve the same actuation effect, thereby further reducing the external voltage required for input, reducing the occurrence of electromagnetic interference, and making the test results more accurate.

[0047] More preferably, in an embodiment, the number of layers of the laminated piezoelectric patch at the plurality of preset positions on the surface of the engine blade, and the size and direction of the excitation output by each of the plurality of laminated piezoelectric patches are determined based on the different target excitation modes of the engine blade.

[0048] For example, the number of monolithic piezoelectric layers can be varied, the thickness of the individual piezoelectric patches can be in the range of 0.75mm to 1.5mm, and the composite piezoelectric material has excellent conformability, which facilitates the surface bonding with the fan blade.

[0049] In an embodiment, the excitation system of the active piezoelectric branch circuit based on the array of laminated piezoelectric patches can provide a spatially and temporally varying excitation load to the blade, which is independent of the rotational speed of the blade, and the input voltage is significantly lower than the voltage required for single-layer piezoelectric patch excitation. The excitation mode can flexibly simulate the real working environment of the blade, and the experiment can be easily carried out.

[0050] Further, in this embodiment, during the high-low cycle composite fatigue test, the fan blade is mounted on a rotating test bench and rotated at a predetermined speed to simulate the low-cycle excitation received by the blade during engine operation. At the same time, the array composed of multiple laminated piezoelectric patches is attached to the fan blade at the preset positions optimized by the previous simulation. Preferably, the positions of each excitation point in the laminated piezoelectric patch array can be optimized according to the target excitation mode, and the size and direction of the excitation output by each excitation point can be designed for different target order modes, so as to achieve the effect of mutual cooperation and coordinated excitation of each excitation point.

[0051] Referring to the embodiment shown in Figure 1 , Figure 1 The fatigue test device for the engine blade provided by the present application can further include a processor 1, a digital circuit component 2, an analog signal generator 3, and a power amplifier 4 connected in sequence. The control signal of the engine blade output by the processor 1 is converted into a digital signal by the digital circuit component 2, and then transmitted to the analog signal generator 3 to be converted into an analog signal. The analog signal is amplified by the power amplifier 4 and then output to the multiple laminated piezoelectric patches 12.

[0052] The processor herein can be a computer, a computer, or other device component with corresponding computing power, which is loaded with a data processing program. The data processing program can receive the input blade response signal, process it through a control algorithm, and output the target excitation waveform and current / voltage signal. At the same time, in order to ensure the consistency of the excitation load output by the actuator during the high-low cycle composite fatigue test, the data processing program should have a compensation function to timely correct the size of the output signal.

[0053] It can be understood that the external circuit provides an active piezoelectric branch circuit for the laminated piezoelectric patch with an external power supply. The active piezoelectric branch circuit can generate a control signal according to the sensor signal and the control law, and then apply it to the laminated patch actuator after amplification, thereby achieving the purpose of excitation. Preferably, the active piezoelectric branch circuit uses a digital acquisition card and an output card to realize programmable inductance and negative capacitance.

[0054] Meanwhile, in the fatigue testing device for engine blades provided by the present invention, the vibration meter can be a laser vibration meter, or a strain gauge, a high-speed camera, etc.

[0055] Furthermore, in a preferred embodiment, such as Figure 1 As shown, the fatigue testing device for engine blades provided by the present invention may further include a data acquisition component 15, which is used to convert the vibration signal of the engine blade acquired by the vibration meter into a digital signal and input it into the processor.

[0056] Furthermore, in one embodiment of the present invention, the processor of the engine blade fatigue testing device provided by the present invention is further configured to adjust the output of the stacked piezoelectric patch according to the gap between the actual response and the target response of the engine blade collected and fed back by the vibration meter.

[0057] For example, the output load of the stacked piezoelectric patch array can be controlled based on the target excitation mode shape of the fan blades and the optimized excitation strategy. A vibration meter detects the actual response of the excited fan blades and feeds it back to the processor in real time. Then, based on the difference between the actual and target responses of the blades, the electrical signals input to the stacked piezoelectric patch actuator array are adjusted to compensate for and adjust the load, ensuring the continuous stability of the excitation system's output load, thereby simulating the high-cycle load on the blades during engine operation.

[0058] In one embodiment of the present invention, the fatigue testing device for engine blades provided by the present invention may further include a mounting base 6, a tooling shaft 9 and a plurality of slip rings that are fitted and installed on the top of the vacuum test chamber. The slip rings are used to transmit electrical signals to the rotating engine blades.

[0059] The following is combined Figure 1 The assembly structure and working principle of the fatigue testing device for engine blades provided by this invention will be described in detail.

[0060] like Figure 1 As shown, the fan blade 11 is rotatably mounted in the vacuum test chamber 5, and its rotational speed is configured to the speed required for the test, thereby applying a low-cycle load to the blade. The mounting components between the fan blade 11 and the vacuum test chamber 5 may also include a mounting base 6, a stationary ring mounting bracket 7, a first slip ring 8, a tooling shaft 9, and a simulated fan disk 10. These components cooperate to allow the fan blade to be rotatably suspended from the top of the vacuum test chamber 5.

[0061] Before the experiment, the active control model and related control parameters of the fan blades can be set in advance in the data processing program of processor 1. The data processing program in processor 1 can be a control program developed based on LabVIEW, Simulink or other software tools, which can generate the corresponding current control signal according to the voltage signal and the predetermined volt-ampere characteristic equation.

[0062] After the test starts, the processor 1 outputs the current control signal to the digital circuit assembly 2 through the cable, the digital circuit assembly 2 can be composed of an NI mainboard and the like, and then outputs a digital signal according to a preset circuit, and transmits the digital signal to the analog signal generator 3 through the cable, converts the digital signal into an analog signal, and finally outputs a preset excitation waveform and voltage signal through the power amplifier 4, and the excitation waveform and voltage signal are connected to the analog fan disc 10 in the vacuum rotating test bed through the first slip ring 8. Figure 1 The signal transmission line 17 in the middle blue color finally transmits to the plurality of laminated piezoelectric patches 12 arranged on the fan blade 11, and excites the fan blade 11 to vibrate.

[0063] In this embodiment, a strain gauge-based vibration meter is used, that is, a strain gauge 13 is arranged on the fan blade 11 at a position corresponding to a sensitive response position of each vibration mode, and the vibration signal obtained is transmitted to the data acquisition assembly 15 through the red strain acquisition line 16 and the second slip ring 14, and then converted into a digital signal and input into the processor 1, so as to provide an input for the data processing program. Figure 1

[0064] After the data processing program in the processor 1 receives the vibration response signal, the current signal input into the digital circuit assembly 2 is adjusted according to the difference between the actual response of the fan blade 11 and the target response, so as to ensure that the load output by the laminated piezoelectric patch 12 is continuously stable, and the high-cycle load on the blade during the simulation of the engine working is simulated.

[0065] The actuator based on the laminated piezoelectric patch array and the active piezoelectric branch circuit can provide a spatially and temporally varying excitation load to the fan blade 11, and the excitation load is independent of the blade rotating speed and is not affected by the blade rotating speed, so that the excitation mode of the actual working environment of the blade can be flexibly simulated; and the input voltage is significantly lower than the voltage required for single-layer piezoelectric patch excitation, which is more conducive to experimental research and is helpful for life prediction of key components of an aero-engine.

[0066] Although the above-described methods are illustrated and described as a series of acts for the sake of simplicity, it should be understood and appreciated that the methods are not limited by the order of acts, as some acts may, in accordance with one or more embodiments, occur in different orders and / or concurrently with other acts from that shown and described herein. And / or, depending on the embodiment, various elements of the methods could be implemented in hardware, software, or both.

[0067] ​The previous description of the disclosure is provided to enable any person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other variations without departing from the spirit or scope of the disclosure. Thus, the disclosure is not intended to be limited to the examples described herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A fatigue testing apparatus for engine blades, used to apply non-interfering high- and low-cycle combined loads to the engine blades to simulate the fatigue loads experienced by the engine blades during operation, the fatigue testing apparatus comprising: A vacuum test chamber, wherein the engine blades are rotatably suspended from the top of the vacuum test chamber; An actuator, comprising stacked piezoelectric patches attached to a plurality of preset positions on the surface of the engine blade, each of the preset positions comprising multiple layers of piezoelectric patches connected in parallel, the stacked piezoelectric patch array being connected to an external power supply to apply a target excitation mode to the engine blade while it rotates; as well as A vibration meter is used to collect and feedback the vibration response of the engine blades in order to perform fatigue test analysis of the engine blades.

2. The fatigue testing apparatus as described in claim 1, characterized in that, The stacked piezoelectric patches are arranged at multiple preset positions on the surface of the engine blade, and the selection is based on the strain energy level in the target vibration mode cloud map simulated by the blade software.

3. The fatigue testing apparatus as described in claim 2, characterized in that, The stacked piezoelectric patch is made of composite fiber piezoelectric material, and multiple stacked piezoelectric patches are respectively pasted at multiple preset positions on the front and back sides of the engine blade to form the stacked piezoelectric patch array.

4. The fatigue testing apparatus as described in claim 2, characterized in that, The number of layers of the stacked piezoelectric patches at multiple preset positions on the surface of the engine blade, as well as the magnitude and direction of the excitation output by each of the multiple stacked piezoelectric patches, are determined by optimization based on the different target excitation modes of the engine blade.

5. The fatigue testing apparatus as described in claim 1, characterized in that, It also includes a processor, a digital circuit component, an analog signal generator, and a power amplifier connected in sequence. The control signal of the engine blade output by the processor is converted into a digital signal by the digital circuit component and then transmitted to the analog signal generator to be converted into an analog signal. The analog signal is amplified by the power amplifier and then output to the plurality of stacked piezoelectric patches.

6. The fatigue testing apparatus as described in claim 5, characterized in that, The processor is also configured to compensate for and adjust the output of the stacked piezoelectric patch based on the difference between the actual response and the target response of the engine blade, which is collected and fed back by the vibration meter.

7. The fatigue testing apparatus as described in claim 6, characterized in that, It also includes a data acquisition component, used to convert the vibration signal of the engine blade collected by the vibration meter into a digital signal and then input it into the processor.

8. The fatigue testing apparatus as described in claim 1, characterized in that, It also includes a mounting base, tooling shaft and multiple slip rings that are installed on the top of the vacuum test chamber, the slip rings being used to transmit electrical signals to the rotating engine blades.

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