CN102818686A - Modal test method for metal grid of grid-control traveling wave tube - Google Patents
Modal test method for metal grid of grid-control traveling wave tube Download PDFInfo
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Abstract
The invention discloses a modal test method for a metal grid of a grid-control traveling wave tube. The method includes the steps of firstly, arranging measuring points on a grid test piece by using a method of point-to-point excitation and single-point vibration pick-up; secondly, subjecting a grid structure to shock excitation by using a hammering method and simultaneously measuring a response of the grid structure; thirdly, sampling obtained signals through an analog/digital (A/D) converter and inputting the signals into a computer to calculate a transfer function of an excitation point and a response point to obtain the frequency of the grid; and fourthly, subjecting the grid structure to overall excitation by using a method of sound wave excitation, using a laser vibration meter to measure responses of the points, and real-timely fitting curves of the transfer function in the computer to obtain a modal shape of the grid.
Description
Technical field
The present invention relates to travelling-wave tube, relate in particular to a kind of grid-control TWT metal grid mesh modal test method.
Background technology
Travelling-wave tube is one of widely used most important electron device.Some environment for use very severes of travelling-wave tube need have very strong anti-vibration, impact property.In order to verify the resistance to shock of travelling-wave tube; Need carry out vibration test to travelling-wave tube; And modal test is the basis of other vibration testing analysis, and the modal parameter (natural frequency and the vibration shape) that detects product in the modal test is the important parameter that bears in the dynamic load structural design.
Domestic modal test only is to some big machinery structures at present; Like aircraft, automobile, boats and ships, bridge and building etc.; The structure of travelling-wave tube generally is the microstructure of more complicated, and its sealing characteristics makes that also inner modal parameter can't directly detect through finished product.More domestic units also only obtain the inner modal parameter of travelling-wave tube microstructure through the method for computer simulation emulation at present, and the complete mode verification system of a cover is not verified the accuracy of its analog result.
Travelling-wave tube internal part structure is more complicated and small, is the weak element that lost efficacy because of vibration in the travelling-wave tube like the spoke-like aperture plate, and the dynamics of this light and gentle microstructure has become the important directions of the stable and reliability consideration of travelling-wave tube.With regard to the microstructure dynamics research, mainly also depend on numerical simulation at present, also there is not the test method that microstructure dynamic characteristic parameter is analyzed that is used for of a cover system so far.
Summary of the invention
Shortcoming to prior art; The purpose of this invention is to provide a kind of grid-control TWT metal grid mesh modal test method; Be used to detect the modal parameter of microstructure electronic product; Grasp its dynamic Characteristics of Structure, check its resistance to shock, solved the microstructure of this type of travelling-wave tube vacuum electron device---the mode checking difficult problem of spoke-like metal grid mesh.
To achieve these goals, technical scheme of the present invention is: a kind of grid-control TWT metal grid mesh modal test method, and it comprises the steps: the method for (1) employing pointwise excitation, single-point pick-up, on the aperture plate test specimen, arranges measuring point; (2) give wire-grid structure with exciting with hammering method, measure its response simultaneously; (3) signal that obtains is imported computing machine after A/D converter is sampled, calculate the transport function of point of excitation and response point, obtain the frequency of aperture plate; (4) with the method for acoustic wave excitation wire-grid structure is carried out the integral body excitation, measure the response of each point, and the match of in computing machine, carrying out transfer curve in real time obtains the Mode Shape of aperture plate with laser vibration measurer.
Further, in step (1), on the shell of aperture plate, arrange 68 measuring points altogether, form the network of aperture plate.
Further, aperture plate is fixed on the anchor clamps of boring, consistent with physical constraint.
Preferably, said anchor clamps adopt the aluminum alloy materials that good rigidly, weight are low, have higher rigidity mass ratio and high damping characteristic, and anchor clamps process with whole block material, the center of gravity of anchor clamps and test product with test the table top center and overlap.
Compared with prior art, the present invention adopts hammering to confirm natural frequency, and the motivational techniques of the vibration shape are confirmed in acoustically-driven, has solved the problem that microstructure is not got up because of the too high exciting of frequency; Adopt aperture plate to be fixed on the anchor clamps of boring the structure support method consistent with physical constraint.Solve microstructure---the installation of travelling-wave tube aperture plate and the problem of location; Adopt laser beam to replace traditional sensor, method, gather vibration response signal on the aperture plate, solved the difficult problem that size because of microstructure is too little, can't the Surface Mount sensor can't obtain to accomplish acquisition of signal.
Description of drawings
Below in conjunction with accompanying drawing the present invention is done further detailed description.
Fig. 1 is the pilot system synoptic diagram.
Fig. 2 is travelling-wave tube aperture plate test specimen figure.
Fig. 3 is an aperture plate modal test installation drawing.
Fig. 4 is a wire-grid structure modal test system diagram.
Fig. 5 is an aperture plate model vibration measuring point arrangenent diagram.
Fig. 6 is the oscillating curve and the spectrogram of aperture plate.
Fig. 7 is the spectrogram of aperture plate under the single-frequency sound wave excitation.
Fig. 8 is the modal test bending vibation mode picture of aperture plate.
Fig. 9 is aperture plate simulation calculation figure as a result.
Embodiment
The present invention adopts the frequency domain method of identification to carry out the test modal analysis to the shell structure of aperture plate.Employing pointwise excitation, the method for single-point pick-up has been arranged 68 measuring points on the aperture plate test specimen; Give wire-grid structure with exciting with hammering method; Measure its response simultaneously, then signal is imported computing machine after A/D converter is sampled, these data are through Fourier (FFT) conversion fast; Then calculate the transport function of point of excitation and response point, obtain the frequency of aperture plate.With the method for acoustic wave excitation wire-grid structure is carried out the integral body excitation then, measure the response of each point, and the match of in computing machine, carrying out transfer curve in real time obtains the Mode Shape of aperture plate with laser vibration measurer.The test modal method is a kind of test method of the direct measuring system natural frequency and the vibration shape; It is through the input signal and output signal of while measuring system; Transfer curve according to test records carries out curve fitting, thereby calculates natural frequency, modal stiffness, modal mass etc.In practical structures or model vibration test; The natural frequency of vibration that draws structure is the purpose of many tests; The natural frequency of vibration of measuring structure with hammering method is a kind of both economical, desirable vibration measuring method; This method can realize that multi-point exciting (firmly hammer multiple spot is knocked) and single-point respond, and shows the hammering frequency response curve on computers in real time, calculates transport function, auto-power spectrum, cross-power spectrum, coherence function and the fourier spectra of each hammering vibration measuring point through superposed average repeatedly.In travelling-wave tube spoke-like aperture plate microstructure modal test verification technique; To this special construction of aperture plate---arch engraved structure, light weight and soften; Can't mount sensor, its vibration experiment build key issues such as mainly solving motivational techniques, signals collecting and structure support.
See also Fig. 1 and Fig. 4, the test macro of vibration test is made up of three parts: (1) excitation system.Excitation system mainly comprises vibrator, accomplishes the excitation to test specimen by it.Typical exciting bank has exciter system, ram hammer, step excitation device.Energisation mode has single-point excitation, multiple spot excitation and the excitation of single-point subregion.Power hammer and two kinds of energisation modes of acoustic wave excitation of adopting in the test.(2) measure portion.Measure portion mainly is data acquisition, comprises sensor, charge amplifier and relevant coupling part.Its function is to be transformed into electric signal to measured (power and response acceleration) through sensor, and after charge amplifier or decay, entering signal analysis software disposal system is handled then.Because the special construction of aperture plate replaces acceleration transducer with laser beam, gather vibration response signal on the aperture plate, measure the deformation quantity of aperture plate reference point.Adopt the PSV-300 laser scanning system that aperture plate is carried out structure modal test in the test.At first aperture plate shooting back is reached computing machine the layouting before the line scanning test of going forward side by side to figure by the inner minisize pick-up head of laser head; After starting collector; Laser will carry out the data acquisition of scan test and measuring point by scanning sequency automatically, and in computing machine, carries out the frequency response function analyzing and processing in real time.It is very approaching to test first three the rank natural frequency and the calculated value that obtain structure, and maximum measuring relative errors is 3.5%.(3) signal processing system.Analysis part mainly comprises peripherals such as analyser and microcomputer (software package), printer.The effect of analyser is to measure and analyze by the signal that sensor or laser instrument produced, and until obtaining transfer function data, it is to be the Digital Signal Analysis system of core with the fast Fourier transform (FFT) technology.
See also Fig. 3, the anchor clamps that test is used are a kind of custom-designed test fixtures of aperture plate microstructure modal test that are, its supporting way is consistent with the actual welding situation of aperture plate in travelling-wave tube rifle body.It adopts the aluminum alloy materials that good rigidly, weight are low, have higher rigidity mass ratio and high damping characteristic; Anchor clamps process with whole block material, eliminate the self-sustained oscillation of anchor clamps; All surface of contact reach required flatness and contact to guarantee favorable mechanical, and guarantee that anchor clamps overlap with test table top center with the center of gravity of test product.
See also Fig. 5; In order to reflect the dynamic perfromance of aperture plate comprehensively, consider the characteristics of its structure simultaneously, arranged 68 measuring points altogether at node place, the hole of aperture plate shell; Form in the network test of aperture plate at first and by the inner minisize pick-up head of laser head aperture plate shooting back to be reached the go forward side by side test of line scanning test of computing machine to figure and layout; After starting collector, laser will carry out scan test and data acquisition by scanning sequency automatically, and in computing machine, carries out the frequency response function analyzing and processing in real time.
See also Fig. 2 and Fig. 3; In order to obtain the vibration parameters that travelling-wave tube vibrates the weak part of sparking, grid-control TWT is controlled the aperture plate sample carried out modal test, through input and output signal process parameter recognition acquisition modal parameter to testing the structure of gathering; Obtain mode natural frequency, damping ratio and the mode shape of shaking; Make the characteristic of structure each main mode in rank in a certain interested frequency range clear, can observe out the distortion of aperture plate clearly, can make correct modification to structural design accurately like this through the shape animation that shakes; Reduce the irrationality of structure, improve the rigidity of aperture plate.
Test result:
1, aperture plate vibration natural frequency.See also Fig. 6, aperture plate is fixed on the anchor clamps, and firmly hammer knocks aperture plate, measure the vibration of aperture plate simultaneously with laser vibration measurer, do spectrum analysis through the aperture plate oscillating curve that measures, obtain the natural frequency of aperture plate, its spectrum peak data are seen table 1.
Table 1 spectrum peak tabulation (engineering unit: mm/s)
| Sequence number | Frequency | Amplitude spectrum Peak | Damping ratio |
| 01 | 14235.9 | 11.4748 | 0.063％ |
| 02 | 18331.1 | 5.71416 | 0.142％ |
| 03 | 22538.6 | 1.61977 | 0.120％ |
2, the vibration shape is obtained.See also Fig. 7 and Fig. 8, with single-frequency sound wave excitation aperture plate,, measure the vibration information of each point and the treated vibration shape that obtains first three rank of aperture plate with laser vibration measurer.The model frequency that can know wire-grid structure self from Fig. 8 is very high, in travelling-wave tube vibration environment certification test, can not cause cloudy grid spacing too small because of large deformation takes place in aperture plate resonance.Aperture plate in homogeneous tube with other structure generation translations of travelling-wave tube.
See also Fig. 9, the analog result of aperture plate and test findings are very approaching.Do difficult the doing of modal test of the such engraved structure model of aperture plate; The metal spokes shape aperture plate modal test verification method of this patent introduction has solved this difficult problem; Actual modal test has obtained desirable data result, and the analog computation result is verified preferably.
Claims (4)
1. a grid-control TWT metal grid mesh modal test method is characterized in that it comprises the steps:
(1) method of employing pointwise excitation, single-point pick-up is arranged measuring point on the aperture plate test specimen;
(2) give wire-grid structure with exciting with hammering method, measure its response simultaneously;
(3) signal that obtains is imported computing machine after A/D converter is sampled, calculate the transport function of point of excitation and response point, obtain the frequency of aperture plate;
(4) with the method for acoustic wave excitation wire-grid structure is carried out the integral body excitation, measure the response of each point, and the match of in computing machine, carrying out transfer curve in real time obtains the Mode Shape of aperture plate with laser vibration measurer.
2. grid-control TWT metal grid mesh modal test method according to claim 1 is characterized in that, in step (1), on the shell of aperture plate, arranges 68 measuring points altogether, forms the network of aperture plate.
3. grid-control TWT metal grid mesh modal test method according to claim 1 is characterized in that, aperture plate is fixed on the anchor clamps of boring, and is consistent with physical constraint.
4. grid-control TWT metal grid mesh modal test method according to claim 3; It is characterized in that; Said anchor clamps adopt the aluminum alloy materials that good rigidly, weight are low, have higher rigidity mass ratio and high damping characteristic; Anchor clamps process with whole block material, and anchor clamps overlap with test table top center with the center of gravity of test product.
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| CN104239645A (en) * | 2014-09-23 | 2014-12-24 | 工业和信息化部电子第五研究所 | Design method and system for anti-vibration reliability of micro assembly component |
| CN104776963A (en) * | 2015-04-14 | 2015-07-15 | 北京强度环境研究所 | Acoustic excitation non-contact modal testing system and method |
| CN108920752A (en) * | 2018-05-25 | 2018-11-30 | 电子科技大学 | A kind of traveling wave tube structure size synchronized update and Iterative Design method |
| CN111474241A (en) * | 2020-06-10 | 2020-07-31 | 国网山西省电力公司电力科学研究院 | Method for evaluating latent fault factors existing in GIS structural state |
| CN114312906A (en) * | 2021-12-29 | 2022-04-12 | 中铁第四勘察设计院集团有限公司 | Floating slab track bed, self-vibration frequency detection method thereof and health monitoring method of vibration-damping track |
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| CN104239645A (en) * | 2014-09-23 | 2014-12-24 | 工业和信息化部电子第五研究所 | Design method and system for anti-vibration reliability of micro assembly component |
| CN104776963A (en) * | 2015-04-14 | 2015-07-15 | 北京强度环境研究所 | Acoustic excitation non-contact modal testing system and method |
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| CN111474241A (en) * | 2020-06-10 | 2020-07-31 | 国网山西省电力公司电力科学研究院 | Method for evaluating latent fault factors existing in GIS structural state |
| CN114312906A (en) * | 2021-12-29 | 2022-04-12 | 中铁第四勘察设计院集团有限公司 | Floating slab track bed, self-vibration frequency detection method thereof and health monitoring method of vibration-damping track |
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Address after: No. 78, Zhucun Avenue West, Zhucun street, Zengcheng District, Guangzhou, Guangdong 511300 Patentee after: CHINA ELECTRONIC PRODUCT RELIABILITY AND ENVIRONMENTAL TESTING Research Institute (THE FIFTH ELECTRONIC Research Institute OF MIIT)(CEPREI LABORATORY)) Address before: 510610 No. 110 Zhuang Road, Tianhe District, Guangdong, Guangzhou, Dongguan Patentee before: Fifth Electronics Research Institute of Ministry of Industry and Information Technology |