CN105547619A - Method and system for testing high-order modal frequency and high-order modal damping of thin wall member - Google Patents

Abstract

The invention provides a method and system for testing high-order modal frequencies and damping of thin-walled components, including: performing theoretical calculations on modal frequencies and mode shapes of thin-walled components, and obtaining the number of high-order modal frequencies and their corresponding modal shapes The position and distribution of nodes, nodal lines, and pitch circles; determine the high-order modal frequency of thin-walled components and the constraint boundary conditions required for damping tests; perform high-order modal frequency tests of thin-walled components; conduct high-order modal damping tests of thin-walled components. The invention uses a piezoelectric ceramic exciter to excite the thin-walled component at high frequency, which solves the problem that traditional excitation equipment cannot effectively excite the high-order mode of the thin-walled component. The high-order modal damping of this type of structure can be obtained effectively by using the frequency-domain bandwidth method, which solves the problems existing in the application of the traditional frequency-domain damping test method in thin-walled structures. The test system adopted is easy to build, the test method steps are concise and clear, the repeatability is good, and the test accuracy is high.

Description

A method and system for testing high-order modal frequency and damping of thin-walled components

technical field

The invention belongs to the technical field of vibration testing, in particular to a method and system for testing high-order modal frequencies and damping of thin-walled components.

Background technique

Modal frequency and damping are important dynamic parameters of thin-walled components, and it is of great engineering and academic significance to accurately obtain its modal frequency and identify its damping. Thin-walled components represented by blades, disks, bushings, thin-walled drums, etc. usually work in the environment of multi-field coupling excitation, and are often excited to high-order modal frequencies (above 6kHz), and the corresponding high-order modes are simultaneously It also has the characteristics of dense frequency distribution, small vibration, rich local vibration, and complex stress distribution, which are usually difficult to obtain through traditional excitation equipment testing. For the damping test of thin-walled components, scholars and researchers generally use two methods: the free vibration attenuation method in the time domain and the half-power bandwidth method in the frequency domain. The principle of the time-domain free vibration attenuation method is simple, but its original data is the time history of the structural vibration response, which inevitably includes the influence of background noise, and the accuracy of the damping test will be difficult to guarantee. The frequency-domain half-power bandwidth method is only applicable to the situation where the modal distribution is scattered and the formant waveform in the frequency spectrum is ideal. When the distance between two formant peaks of adjacent orders is relatively close, the frequency value near the half-power point may be very large It is difficult to find, which will affect the test accuracy of damping. In addition, in the practical research of vibration testing of thin-walled components, it is also found that there are often nonlinear characteristics of stiffness in complex boundary or coating damping applications, which will also increase the difficulty of damping identification and limit the traditional half-power bandwidth in the frequency domain application of the law. In view of these characteristics of thin-walled components, the traditional modal frequency and damping test methods have been unable to accurately obtain the high-order modal frequencies and damping of thin-walled components.

Contents of the invention

The object of the present invention is to provide a method and system for testing high-order modal frequency and damping of thin-walled components.

Technical scheme of the present invention is:

A method for testing high-order modal frequencies and damping of thin-walled components, comprising the following steps:

Step 1: Carry out theoretical calculation of modal frequency and mode shape for thin-walled components, and obtain the number of high-order modal frequencies and the positions and distributions of nodes, nodal lines, and pitch circles corresponding to the mode shapes;

Step 2: Determine the high-order modal frequency of thin-walled components and the constraint boundary conditions required for damping tests;

Step 3: Carry out high-order modal frequency test of thin-walled components;

Step 3.1: Set the basic parameters required for the high-order modal frequency test, including: the sensitivity of the piezoelectric ceramic vibrator, the sensitivity of the laser Doppler vibrometer, the sampling frequency, the frequency resolution, and the signal type of the signal generator;

The signal type of the signal generator is a periodic buzzer pulse excitation signal, and a hanning window is added to the signal for processing, and a hanning window is also added to the response signal.

Step 3.2: Determine the number, position and excitation voltage of the corresponding excitation points of the piezoelectric ceramic vibrator through experiments;

Step 3.3: Use the piezoelectric ceramic exciter to vibrate the thin-walled components, obtain multiple frequency response functions and multiple coherence functions of the thin-walled components, and determine the confidence interval of the aggregated frequency response function by the aggregated coherence function, Obtain the higher-order modal frequencies of thin-walled members within this confidence interval;

Step 4: Conduct high-order modal damping test of thin-walled components;

Step 4.1: Set the basic parameters required for the high-order modal damping test, including: frequency sweep interval and frequency sweep rate;

Step 4.2: Obtain the frequency-domain response signal under frequency-sweep excitation by using the time-divided FFT transformation method;

Step 4.3: Use the frequency domain bandwidth method to select the bandwidth value, identify and obtain a certain high-order modal damping of thin-walled components, and sequentially test to obtain other high-order modal damping.

The step 3.2 is specifically carried out as follows:

Step 3.2.1: Refer to the theoretical calculation results of modal frequency and mode shape, preliminarily determine the number, location and excitation voltage of excitation points on the surface of thin-walled components;

Step 3.2.2: Set the excitation voltage of the piezoelectric ceramic drive power supply to three levels of high, medium, and low, and carry out the experiment under the condition that the number of excitation points is one, that is, the number of high-order modal frequencies obtained by referring to step 1 , to judge whether the high-order modal frequency of the thin-walled component can be effectively excited. If the excitation voltage corresponding to the high level cannot effectively excite the high-order modal frequency of the thin-walled component, increase the number of excitation points or change the position of the excitation point until the obtained The number of high-order modal frequencies is greater than or equal to the number of high-order modal frequencies obtained in step 1, and the number, location and excitation voltage of the corresponding excitation points of the piezoelectric ceramic vibrator are determined.

The step 3.3 is specifically carried out as follows:

Step 3.3.1: Test to obtain multiple frequency response functions and multiple coherence functions of thin-walled components, respectively obtain the time-domain waveform of the excitation signal and the time-domain waveform of the response signal, and further obtain one or more excitation signals relative to the response The frequency response function and coherence function of the signal;

Step 3.3.2: sum and average the frequency response function and coherence function of each excitation signal relative to the response signal, and calculate the aggregate frequency response function and aggregate coherence function;

Step 3.3.3: Determine the confidence interval of the aggregated frequency response function from the aggregated coherence function. If the coherence coefficient of the aggregated coherence function in a certain sampling frequency range is greater than or equal to 0.8, then the sampling frequency range is the aggregated frequency response function. confidence interval;

Step 3.3.4: Within the confidence interval of the lumped frequency response function, obtain the higher-order modal frequencies of the thin-walled components through modal identification.

The step 4.2 is specifically carried out as follows:

Step 4.2.1: Data preprocessing: remove the DC component and smooth the obtained original frequency sweep signal;

Step 4.2.2: Divide the time period: divide the entire time domain response into several time periods, and convert the original frequency sweep signal into time domain response signals within several time periods;

Step 4.2.3: Time-frequency transformation: perform FFT transformation on the time-domain response signal of each time period, and perform windowing and filtering processing, and convert the time-domain response signal of each period into a frequency-domain response signal;

Step 4.2.4: Draw the frequency domain response curve: In the entire frequency sweep interval, the frequency after FFT transformation of each time period is used as the x-axis, and the frequency domain response peak value of different time periods is used as the y-axis, which is smoothed by interpolation After that, the frequency domain response curve of the original frequency sweep signal is drawn.

The identification formula of the higher-order modal damping of the thin-walled member is as follows:

$\mathrm{<span\; class="notranslate">\; \&xi;</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}\sqrt{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}}$

Among them, ω _n and ξ are the high-order modal frequency and high-order modal damping ratio respectively, ω ₁ and ω ₂ are the frequency points on the left and right sides of ω _n respectively, and r is the bandwidth value.

The thin-walled member high-order modal frequency and damping test system adopted by the method includes:

A signal generator for generating a low-voltage excitation signal;

A multi-channel piezoelectric ceramic drive power supply that converts low-voltage excitation signals into high-voltage excitation signals;

A piezoelectric ceramic exciter that excites thin-walled components according to a high-voltage excitation signal;

Laser Doppler vibrometer to test the response signal of thin-walled components;

Data acquisition equipment for collecting excitation force signals and response signals;

A computer to set the high-order modal frequencies and basic parameters required for damping tests, obtain the high-order modal frequencies of thin-walled components within the confidence interval of the aggregated frequency response function determined by the lumped coherence function, and identify and obtain the high-order modal damping of thin-walled components;

The output end of the signal generator is connected to the input end of the multi-channel piezoelectric ceramic drive power supply, the output end of the multi-channel piezoelectric ceramic drive power supply is connected to the input end of the piezoelectric ceramic exciter, and the piezoelectric ceramic exciter is attached to the thin-walled member On the surface, the output end of the laser Doppler vibrometer is connected to the input end of the data acquisition device, and the output end of the data acquisition device is connected to the input end of the computer.

Beneficial effect:

The method of the present invention solves the problem of high-order modal frequency and damping testing of thin-walled components through the built test system. The device and method have the following technical advantages:

(1) The piezoelectric ceramic exciter is used to excite the thin-walled components at high frequency, which solves the problem that the traditional excitation equipment cannot effectively excite the high-order modes of the thin-walled components.

(2) The high-order modal frequency test procedure adopted can obtain the high-order modal frequency of thin-walled components with high precision.

(3) The high-order modal damping of this type of structure can be obtained effectively by using the frequency-domain bandwidth method, which solves the problems existing in the application of the traditional frequency-domain damping test method in thin-walled structures.

(4) The test system adopted is easy to build, the test method steps are concise and clear, the repeatability is good, and the test accuracy is high.

Description of drawings

Fig. 1 is a thin-walled component high-order modal frequency and damping test system structural block diagram of the specific embodiment of the present invention;

Fig. 2 is the frequency response function and the coherence function of the thin-walled member obtained by piezoelectric ceramic excitation according to the specific embodiment of the present invention;

Fig. 3 is the frequency domain response graph of the third-order frequency sweep signal of the thin-walled cylindrical shell 3 response points of the specific embodiment of the present invention;

Fig. 4 is a schematic diagram of a test thin-walled cylindrical shell according to a specific embodiment of the present invention, wherein, 1-vibration measuring point, 2-annular pressure plate, 3-M8 bolt, 4-base, 5-piezoelectric ceramic exciter, 6 - Thin-walled cylindrical shell structures;

Fig. 5 is a flow chart of high-frequency modal frequency testing and damping identification of a thin-walled cylindrical shell excited by piezoelectric ceramics according to a specific embodiment of the present invention.

detailed description

The specific implementation manners of the present invention will be described in detail below in conjunction with the accompanying drawings.

The high-order modal frequency and damping test system for thin-walled components used in this embodiment, as shown in Figure 1, includes:

A signal generator for generating a low-voltage excitation signal;

A multi-channel piezoelectric ceramic drive power supply that converts low-voltage excitation signals into high-voltage excitation signals;

A piezoelectric ceramic exciter that excites thin-walled components according to a high-voltage excitation signal;

Laser Doppler vibrometer to test the response signal of thin-walled components;

Data acquisition equipment for collecting excitation force signals and response signals;

A computer to set the high-order modal frequencies and basic parameters required for damping tests, obtain the high-order modal frequencies of thin-walled components within the confidence interval of the aggregated frequency response function determined by the lumped coherence function, and identify and obtain the high-order modal damping of thin-walled components;

The output end of the signal generator is connected to the input end of the multi-channel piezoelectric ceramic drive power supply, the output end of the multi-channel piezoelectric ceramic drive power supply is connected to the input end of the piezoelectric ceramic exciter, and the piezoelectric ceramic exciter is attached to the thin-walled member On the surface, the output end of the laser Doppler vibrometer is connected to the input end of the data acquisition device, and the output end of the data acquisition device is connected to the input end of the computer.

The signal generator is used to send a variety of analog signals such as sine, frequency sweep, random, and periodic buzzer pulses. In this embodiment, the signal source of the LMSSCADAS acquisition controller is used as the signal generator. The LMSSCADAS acquisition controller includes 16 data acquisition channels and 2 standard signal sources, so it has the functions of data acquisition and signal generator at the same time, and can send out various analog signals such as sine, frequency sweep, random, and periodic buzzer pulses.

The piezoelectric ceramic driving power supply is used to provide high stability and high resolution voltage for the piezoelectric ceramic exciter. The shell structure may have the problem of insufficient excitation energy. The selected Rhvd3c110v driving power supply has the function of driving three piezoelectric ceramic exciters at the same time, and is connected to the output terminal of the signal generator through the BNC connector. The analog excitation signal can be amplified by 24 times, and the piezoelectric ceramic can work in the positive voltage range by setting the bias voltage. Its voltage output resolution is 5mV, the maximum output power is 100W, and the output voltage can be monitored in real time through the LCD display.

The thin-walled member in this embodiment is a thin-walled cylindrical shell structure, and the piezoelectric ceramic exciter is used to stick on the surface of the thin-walled member and vibrate it. In order to avoid adding too much additional mass to the thin-walled cylindrical shell structure Affected, should choose the smaller size of the piezoelectric ceramic exciter. At the same time, in order to have a larger excitation amplitude, the thickness of the laminated ceramic sheets should be as large as possible. After comparing the actual test results, the piezoelectric ceramic vibrator is selected from the P-885.10 of the German PI company. Its dimensions are 5×5×9mm, the capacitance is 0.6uf, and it only weighs 2g. It can withstand the bias voltage of 2.5V to 100V. Under the excitation of 25kHz, the maximum displacement vibration response is close to 0.65um, and the vibration excitation can be realized in the frequency range of 0.1k ~ 20kHz, which can effectively meet the high frequency excitation of thin-walled components above 6kHz need.

The laser Doppler vibrometer is used to obtain the vibration response signal of the thin-walled component, and transmit the vibration response signal to the data acquisition analyzer. The laser Doppler vibrometer used in this embodiment is PolytecPDV-100, the minimum resolution of the vibration velocity is 0.02μm/s, the working distance is 0.15m-30m, and the frequency range is 1Hz-22KHZ.

The data acquisition device is a 16-channel LMSSCADAS MobileFront-End, which is used to collect the excitation force signal of the piezoelectric ceramic vibrator and the response signal obtained by the laser Doppler vibrometer test, and send it to the computer.

The computer stores, displays, and analyzes the test data in time and frequency domain. The DELLM6400 high-performance notebook computer is selected in this embodiment.

In this embodiment, the test object is a thin-walled cylindrical shell structural member 6 as shown in FIG. Use the ring pressure plate 2 to fix its mounting edge on the fixture through 8 M8 bolts 3 to simulate the fixed support-free boundary condition, and the M8 bolts on the fixture are tightened on the base 4 with a uniform specified torque through a torque wrench. The electric ceramic vibrator 5 is pasted on the surface of the thin-walled cylindrical shell structure 6, and the response signal is collected by a laser Doppler vibrometer at the vibration measurement point 1.

Table 1 Dimensional parameters of thin-walled cylindrical shell structures

Table 2 Material parameters of thin-walled cylindrical shell structures

The thin-walled component high-order modal frequency and damping test method of this embodiment, as shown in Figure 5, includes the following steps:

Step 1: Carry out theoretical calculations of modal frequency and mode shape for the thin-walled cylindrical shell structure, and obtain the number of high-order modal frequencies and the positions and distributions of nodes, nodal lines, and pitch circles corresponding to the mode shapes;

Select the frequency lower limit f _l of the high-order modal frequency of the thin-walled cylindrical shell structure. When the modal frequency is greater than or equal to the frequency lower limit f _l , it is the high-order modal frequency. When the modal frequency is smaller than the frequency lower limit f _l , it is the low frequency. modal frequency (selection of the lower limit frequency). At the same time, in the range of low-order modal frequencies and high-order modal frequencies, the theoretical calculation of the modal frequencies of thin-walled cylindrical shell structural members is carried out by analytical or finite element methods to obtain the number of high-order modal frequencies, and to grasp the modal vibrations. The positions and distributions of nodes, pitch lines, and pitch circles corresponding to the model.

Step 2: Determine the high-order modal frequency of thin-walled components and the constraint boundary conditions required for damping tests;

In the free state test, the thin-walled component under test needs to be suspended by a rubber rope; in the constrained state test, the thin-walled component needs to be clamped effectively by the clamp, and the maximum torque value of the M8 bolt is determined by the torque wrench, and it can be effectively clamped. Tighten the tested shell (for the 12.9 grade bolts used in the fixture, the final tightening torque value is 40Nm). It is guaranteed that the modal frequency and damping parameters will not be disturbed and affected by boundary conditions during the test, and have good repeatability and consistency.

Step 3: Carry out high-order modal frequency test of thin-walled components;

Step 3.1: Set the basic parameters required for the high-order modal frequency test, including: the sensitivity of the piezoelectric ceramic vibrator, the sensitivity of the laser Doppler vibrometer, the sampling frequency, the frequency resolution, and the signal type of the signal generator;

Set the sensitivity of piezoelectric ceramic vibrator and laser Doppler vibrometer to 11.4mV/Pa and 40000mV/(m/s) respectively.

Refer to the finite element analysis results to determine the test frequency band of high-frequency modal frequencies, and determine the sampling frequency used in the test according to Shannon's theorem.

The signal type of the signal generator is a periodic buzzer pulse excitation signal, and the signal is processed with a hanning window, and the response signal is also added with a hanning window to reduce the impact of leakage errors.

Step 3.2: Determine the number, position and excitation voltage of the corresponding excitation points of the piezoelectric ceramic vibrator through experiments;

Step 3.2.1: Refer to the theoretical calculation results of modal frequency and mode shape, preliminarily determine the number, location and excitation voltage of excitation points on the surface of thin-walled components;

Since the laser Doppler vibrometer is a precise and expensive instrument, usually the number of laser vibration measuring points is only determined as one, and the laser Doppler vibrometer is arranged at the position where the vibration response of the thin-walled component is larger; then, A piezo exciter is placed at the root of the housing.

Step 3.2.2: Set the excitation voltage of the piezoelectric ceramic drive power supply to three levels of high, medium, and low, and carry out the experiment under the condition that the number of excitation points is one, that is, the number of high-order modal frequencies obtained by referring to step 1 , to judge whether the high-order modal frequency of the thin-walled component can be effectively excited. If the excitation voltage corresponding to the high level cannot effectively excite the high-order modal frequency of the thin-walled component, increase the number of excitation points or change the position of the excitation point until the obtained The number of high-order modal frequencies is greater than or equal to the number of high-order modal frequencies obtained in step 1, and the number, location and excitation voltage of the corresponding excitation points of the piezoelectric ceramic vibrator are determined.

Step 3.3: Use the piezoelectric ceramic exciter to vibrate the thin-walled components, obtain multiple frequency response functions and multiple coherence functions of the thin-walled components, and determine the confidence interval of the aggregated frequency response function by the aggregated coherence function, Obtain the higher-order modal frequencies of thin-walled members within this confidence interval;

Step 3.3.1: The signal generator sends an analog signal and is amplified by the piezoelectric ceramic drive power supply, drives the piezoelectric ceramic vibrator to vibrate the thin-walled components, and the data acquisition equipment collects the vibration response obtained by the laser Doppler vibrometer signal, the computer obtains multiple frequency response functions and multiple coherence functions of thin-walled components, respectively obtains the time-domain waveform of the excitation signal and the time-domain waveform of the response signal, and further obtains the frequency of one or more excitation signals relative to the response signal Ring function and coherence function, as shown in Figure 2;

Step 3.3.2: sum and average the frequency response function and coherence function of each excitation signal relative to the response signal, and calculate the aggregate frequency response function and aggregate coherence function;

Step 3.3.3: Determine the confidence interval of the aggregated frequency response function from the aggregated coherence function. If the coherence coefficient of the aggregated coherence function in a certain sampling frequency range is greater than or equal to 0.8, then the sampling frequency range is the aggregated frequency response function. confidence interval;

Step 3.3.4: Within the confidence interval of the lumped frequency response function, the high-order modal frequency f _n of the thin-walled component is obtained through modal identification methods such as the single-degree-of-freedom peak method.

The modal frequencies of the thin-walled cylindrical shell in the range of 0-12kHz obtained under the excitation of the piezoelectric ceramic vibrator are shown in Table 3.

Table 3 The modal frequencies of thin-walled cylindrical shells obtained under the excitation of piezoelectric ceramics in the range of 0-12kHz

Step 4: Conduct high-order modal damping test of thin-walled components;

Step 4.1: Set the basic parameters required for the high-order modal damping test, including: frequency sweep interval and frequency sweep rate;

Determine the frequency sweep start frequency and end frequency according to the frequency sweep interval criterion. The frequency sweep interval criterion can be described as:

First of all, it is necessary to ensure the start frequency f ₁ and end frequency f ₂ of the frequency sweep interval and a certain modal frequency f _n of the thin-walled cylindrical shell structure, as well as the front and rear modal frequencies f _n-1 and f _{n +1} needs to satisfy the formula (1), and at the same time, determine the specific values of the start frequency f ₁ and the end frequency f ₂ according to the formula (2).

f _n-1 < f ₁ ≤ f _n ≤ f ₂ < f _n+1 (1)

f ₁ =(0.8～0.85)f _n (2)

f ₂ =(1.15～1.2) f _n

Determine the frequency sweep rate required to test a certain high-order modal damping: Because the sweep frequency is too fast, it may include the influence of transient vibration, resulting in errors in the final damping results. Therefore, before carrying out the frequency sweep test, it is necessary to compare the frequency results corresponding to the maximum value of the frequency spectrum curve of the vibration response signal obtained at several frequency sweep rates. If the above frequency results corresponding to certain speed parameters are very close, you can choose One of them is used as the sweep rate for the test.

Step 4.2: Use the time-segmented FFT transformation method to obtain the frequency domain response signal under the frequency sweep excitation, as shown in Figure 3;

Step 4.2.1: Data preprocessing: remove the DC component and smooth the obtained original frequency sweep signal, remove the burrs in the time domain signal, reduce the influence of interference factors, and make the original frequency sweep signal obtained by the test as close as possible to its actual value;

Step 4.2.2: Divide time segments: Divide the entire time domain response into several time segments, and convert the original frequency sweep signal into time domain response signals within several time segments; the more time segments are divided, the subsequent obtained frequency domain response The higher the accuracy of the curve.

Step 4.2.3: Time-frequency transformation: perform FFT transformation on the time-domain response signal of each time period, and perform windowing and filtering processing, and convert the time-domain response signal of each period into a frequency-domain response signal;

Step 4.2.4: Draw the frequency domain response curve: In the entire frequency sweep interval, the frequency after FFT transformation of each time period is used as the x-axis, and the frequency domain response peak value of different time periods is used as the y-axis, which is smoothed by interpolation After that, the frequency domain response curve of the original frequency sweep signal is drawn.

Step 4.3: Use the frequency domain bandwidth method to select the bandwidth value, identify and obtain a certain high-order modal damping of thin-walled components, and sequentially test to obtain other high-order modal damping.

Assume that the motion of the thin-walled component under test is x(t) under the excitation of a certain piezoelectric ceramic exciter, m, c, k are the mass, damping and stiffness of the system, the excitation type is simple harmonic excitation, and the excitation amplitude is F ₀ , the excitation frequency is ω, then its motion equation can be expressed as:

$\mathrm{<span\; class="notranslate">\; m</span>}\stackrel{<span\; class="notranslate">\; \&CenterDot;\&CenterDot;</span>}{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; c</span>}\stackrel{<span\; class="notranslate">\; \&CenterDot;</span>}{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; k</span>}\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\mathrm{<span\; class="notranslate">\; the\; s</span>}\mathrm{<span\; class="notranslate">\; i</span>}\mathrm{<span\; class="notranslate">\; no</span>}\mathrm{<span\; class="notranslate">\; \&omega;</span>}\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

Its steady-state response amplitude is

$\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; k</span>}}{\sqrt{{<span\; class="notranslate">\; \&lsqb;</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&omega;</span>}<span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&rsqb;</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{<span\; class="notranslate">\; \&lsqb;</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&xi;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&omega;</span>}<span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&rsqb;</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

where ω _n and ξ are the modal frequency and modal damping ratio of a certain order, respectively.

Let λ=ω/ω _n be the frequency ratio, and solve the formula (4) to get

$\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; x</span>}\mathrm{<span\; class="notranslate">\; k</span>}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\sqrt{{<span\; class="notranslate">\; \&lsqb;</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&omega;</span>}<span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&rsqb;</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{<span\; class="notranslate">\; \&lsqb;</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&xi;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&omega;</span>}<span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&rsqb;</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; \&beta;</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&xi;</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

Take two frequency points ω ₁ , ω ₂ around ω _n , and ensure that the dimensionless amplitudes corresponding to ω ₁ , ω ₂ are equal, that is, β ₁ = β ₂ , β ₁ , β ₂ and the maximum dimensionless amplitude The ratio of β _max is r (0<r<1), that is, β ₁ = β ₂ = rβ _max , then

$\frac{\mathrm{<span\; class="notranslate">\; r</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&xi;</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\sqrt{{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&xi;</span>}\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span>$

further available

${\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 4</span>}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; \&xi;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&PlusMinus;</span>\mathrm{<span\; class="notranslate">\; 4</span>}\mathrm{<span\; class="notranslate">\; r</span>}\mathrm{<span\; class="notranslate">\; \&xi;</span>}\sqrt{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; \&xi;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}}{\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; )</span>$

When ξ<<1, the ξ ² term can be ignored, then the formula (6) can be further simplified as

${\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&ap;</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&PlusMinus;</span>\mathrm{<span\; class="notranslate">\; 4</span>}\mathrm{<span\; class="notranslate">\; r</span>}\mathrm{<span\; class="notranslate">\; \&xi;</span>}\sqrt{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}}{\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&PlusMinus;</span>\mathrm{<span\; class="notranslate">\; 4</span>}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; \&xi;</span>}\sqrt{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 9</span>}<span\; class="notranslate">\; )</span>$

The corresponding two solutions are

${\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 4</span>}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; \&xi;</span>}\sqrt{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 10</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 4</span>}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; \&xi;</span>}\sqrt{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 11</span>}<span\; class="notranslate">\; )</span>$

Subtracting the squares of the two solutions yields

${\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; 8</span>}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; \&xi;</span>}\sqrt{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 12</span>}<span\; class="notranslate">\; )</span>$

Simplify formula (12) to get

$\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&xi;</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 4</span>}{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\sqrt{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\sqrt{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 13</span>}<span\; class="notranslate">\; )</span>$

Adding the squares of the two solutions gives Bringing it into Equation (13), the identification formula of high-order modal damping of thin-walled components can be obtained as

$\mathrm{<span\; class="notranslate">\; \&xi;</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}\sqrt{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 14</span>}<span\; class="notranslate">\; )</span>$

Among them, ω _n and ξ are the high-order modal frequency and high-order modal damping ratio respectively, ω ₁ and ω ₂ are the frequency points on the left and right sides of ω _n respectively, and r is the bandwidth value.

Equation (14) is the principle formula for identifying a certain higher-order modal damping of thin-walled components using the frequency-domain bandwidth method. According to this formula, after selecting a reasonable bandwidth value r, a certain high-order damping of thin-walled components can be identified. Since the various modes of the thin-walled cylindrical shell structure in this embodiment are not very dense, the r value of the frequency domain bandwidth method is set as That is to obtain its modal damping for the half power bandwidth method test. However, some high-frequency natural frequencies of thin-walled components tend to be relatively close to each other, setting The frequency value near the half power point may not be found, so a new bandwidth value r needs to be set to identify the damping. The principle formula (12) for identifying a certain higher-order modal damping of thin-walled components using the frequency-domain bandwidth method is used to obtain the higher-order modal damping of thin-walled cylindrical shells in turn.

Table 4 The first 8 modal frequencies, damping ratios and variances of the thin-walled cylindrical shell structures obtained from the test

The specific examples described in this implementation mode are only examples to illustrate the implementation of the patented technical solution of the present invention. Those skilled in the technical field to which the patent of the present invention belongs can modify or supplement the described specific embodiments or replace them in similar ways, but they will not deviate from the technical solutions of the present invention or go beyond the scope defined in the appended claims.

Claims (7)

1. A thin-walled member high-order modal frequency and damping test method, is characterized in that, comprises the following steps: Step 1: Carry out theoretical calculation of modal frequency and mode shape for thin-walled components, and obtain the number of high-order modal frequencies and the positions and distributions of nodes, nodal lines, and pitch circles corresponding to the mode shapes; Step 2: Determine the high-order modal frequency of thin-walled components and the constraint boundary conditions required for damping tests; Step 3: Carry out high-order modal frequency test of thin-walled components; Step 3.1: Set the basic parameters required for the high-order modal frequency test, including: the sensitivity of the piezoelectric ceramic vibrator, the sensitivity of the laser Doppler vibrometer, the sampling frequency, the frequency resolution, and the signal type of the signal generator; Step 3.2: Determine the number, position and excitation voltage of the corresponding excitation points of the piezoelectric ceramic vibrator through experiments; Step 3.3: Use the piezoelectric ceramic exciter to vibrate the thin-walled components, obtain multiple frequency response functions and multiple coherence functions of the thin-walled components, and determine the confidence interval of the aggregated frequency response function by the aggregated coherence function, Obtain the higher-order modal frequencies of thin-walled members within this confidence interval; Step 4: Conduct high-order modal damping test of thin-walled components; Step 4.1: Set the basic parameters required for the high-order modal damping test, including: frequency sweep interval and frequency sweep rate; Step 4.2: Obtain the frequency-domain response signal under frequency-sweep excitation by using the time-divided FFT transformation method; Step 4.3: Use the frequency domain bandwidth method to select the bandwidth value, identify and obtain a certain high-order modal damping of thin-walled components, and sequentially test to obtain other high-order modal damping. 2. thin-walled member high-order modal frequency and damping test method according to claim 1, it is characterized in that, the signal type of described signal generator is periodic humming pulse excitation signal, and this signal adds hanning window processing, The response signal is also added with a hanning window. 3. The thin-walled member high-order modal frequency and damping test method according to claim 1, wherein the step 3.2 is specifically carried out as follows: Step 3.2.1: Refer to the theoretical calculation results of modal frequency and mode shape, preliminarily determine the number, location and excitation voltage of excitation points on the surface of thin-walled components; Step 3.2.2: Set the excitation voltage of the piezoelectric ceramic drive power supply to three levels of high, medium, and low, and carry out the experiment under the condition that the number of excitation points is one, that is, the number of high-order modal frequencies obtained by referring to step 1 , to judge whether the high-order modal frequency of the thin-walled component can be effectively excited. If the excitation voltage corresponding to the high level cannot effectively excite the high-order modal frequency of the thin-walled component, increase the number of excitation points or change the position of the excitation point until the obtained The number of high-order modal frequencies is greater than or equal to the number of high-order modal frequencies obtained in step 1, and the number, location and excitation voltage of the corresponding excitation points of the piezoelectric ceramic vibrator are determined. 4. The thin-walled component high-order modal frequency and damping test method according to claim 1, wherein the step 3.3 is specifically carried out as follows: Step 3.3.1: Test to obtain multiple frequency response functions and multiple coherence functions of thin-walled components, respectively obtain the time-domain waveform of the excitation signal and the time-domain waveform of the response signal, and further obtain one or more excitation signals relative to the response The frequency response function and coherence function of the signal; Step 3.3.2: sum and average the frequency response function and coherence function of each excitation signal relative to the response signal, and calculate the aggregate frequency response function and aggregate coherence function; Step 3.3.3: Determine the confidence interval of the aggregated frequency response function from the aggregated coherence function. If the coherence coefficient of the aggregated coherence function in a certain sampling frequency range is greater than or equal to 0.8, then the sampling frequency range is the aggregated frequency response function. confidence interval; Step 3.3.4: Within the confidence interval of the lumped frequency response function, obtain the higher-order modal frequencies of the thin-walled components through modal identification. 5. The thin-walled member high-order modal frequency and damping test method according to claim 1, wherein said step 4.2 is specifically carried out as follows: Step 4.2.1: Data preprocessing: remove the DC component and smooth the obtained original frequency sweep signal; Step 4.2.2: Divide the time period: divide the entire time domain response into several time periods, and convert the original frequency sweep signal into time domain response signals within several time periods; Step 4.2.3: Time-frequency transformation: perform FFT transformation on the time-domain response signal of each time period, and perform windowing and filtering processing, and convert the time-domain response signal of each period into a frequency-domain response signal; Step 4.2.4: Draw the frequency domain response curve: In the entire frequency sweep interval, the frequency after FFT transformation of each time period is used as the x-axis, and the frequency domain response peak value of different time periods is used as the y-axis, which is smoothed by interpolation After that, the frequency domain response curve of the original frequency sweep signal is drawn. 6. thin-walled component high-order modal frequency and damping test method according to claim 1, is characterized in that, the identification formula of the high-order modal damping of described thin-walled component is as follows: $\mathrm{<span\; class="notranslate">\; \&xi;</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}\sqrt{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}}$ Among them, ω _n and ξ are the high-order modal frequency and high-order modal damping ratio respectively, ω ₁ and ω ₂ are the frequency points on the left and right sides of ω _n respectively, and r is the bandwidth value. 7. The thin-walled member high-order modal frequency and damping test system adopted by the method according to claim 1, characterized in that, comprising: A signal generator for generating a low-voltage excitation signal; A multi-channel piezoelectric ceramic drive power supply that converts low-voltage excitation signals into high-voltage excitation signals; A piezoelectric ceramic exciter that excites thin-walled components according to a high-voltage excitation signal; Laser Doppler vibrometer to test the response signal of thin-walled components; Data acquisition equipment for collecting excitation force signals and response signals; A computer to set the high-order modal frequencies and basic parameters required for damping tests, obtain the high-order modal frequencies of thin-walled components within the confidence interval of the aggregated frequency response function determined by the lumped coherence function, and identify and obtain the high-order modal damping of thin-walled components; The output end of the signal generator is connected to the input end of the multi-channel piezoelectric ceramic drive power supply, the output end of the multi-channel piezoelectric ceramic drive power supply is connected to the input end of the piezoelectric ceramic exciter, and the piezoelectric ceramic exciter is attached to the thin-walled member On the surface, the output end of the laser Doppler vibrometer is connected to the input end of the data acquisition device, and the output end of the data acquisition device is connected to the input end of the computer.