CN104776963A - Acoustic excitation non-contact modal testing system and method - Google Patents
Acoustic excitation non-contact modal testing system and method Download PDFInfo
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- CN104776963A CN104776963A CN201510173722.1A CN201510173722A CN104776963A CN 104776963 A CN104776963 A CN 104776963A CN 201510173722 A CN201510173722 A CN 201510173722A CN 104776963 A CN104776963 A CN 104776963A
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Abstract
The invention belongs to the field of mechanical measurement and provides an acoustic excitation non-contact modal testing system and method. The problem that the conventional modal testing result for a thin-slab structure is inaccurate is solved in a non-contact modal testing mode. According to the technical scheme, the method comprises the following steps: giving a sound by using a loudspeaker, generating vibration through a non-contact excitation thin-slab testing piece, measuring an acoustic signal by using an acoustic sensor, and measuring the vibration response of the thin-slab testing piece by using a scanning-type laser vibration measurement system in a laser non-contact way; by taking the acoustic signal measured by the acoustic sensor as an input signal and taking the vibration response measured by the scanning-type laser vibration measurement system as an output signal, performing analysis through conventional modal analysis software in the scanning-type laser vibration measurement system to obtain modal parameters of the thin-slab testing piece. The system and the method have the benefits that the influence on additional quality and additional rigidity is avoided in a modal test performed by using the system and the method, and the accurate modal parameters can be obtained; meanwhile, the structural damage to the testing piece is avoided, and the testing effect is good.
Description
Technical field
The invention belongs to mechanical meaurement field, be specifically related to the contactless modal test system and method for a kind of acoustically-driven.
Background technology
For this kind of thin-slab construction of circuit board when dynamic analysis, need the modal parameter obtaining structure, the acquisition of modal parameter has two kinds of methods, and the first is theory calculate, is generally FEM (finite element) calculation; Another kind of for be obtained by modal test.For labyrinth, theory calculate often deviation is comparatively large, and need to be revised by modal test, thus modal test is the basis of thin-slab construction dynamic analysis.
Carry out modal test usually to need to use vibrator or power hammer, apply encourage and measure exciting force to structural member to be analyzed, structural member is pasted the response of vibration transducer measuring vibrations, obtained the modal parameter of structure by pumping signal and response signal.When pasting sensor on structural member, additional mass is formed to structural member; And when using vibrator, exciting block is arranged on structural member, structural member is caused to the impact of additional mass and additional stiffness.When there is additional mass and additional stiffness, must there is deviation in test findings, particularly for this kind of thin-slab construction of circuit board, causes the frequency of test, damping and the vibration shape and the modal parameter of structure own to have larger difference.When making firmly hammer excitation, power hammer is activated on thin-slab construction and may causes damage to structure.Thus for thin-slab construction modal test, need the impact as far as possible reducing additional mass and additional stiffness, and avoid knocking and cause damage, optimal state is for taking contactless Modal Experimental Method.And take contactless Modal Experimental Method to need to design how incentive structure, structure is made to produce motion, how to go to measure exciting force and response, only have and realize these two designs and could obtain modal parameter accurately, also do not report that people solves this two problem preferably, realizes Entirely contactless modal test before this.For contactless excitation, someone takes electric magnetization, and this is suitable to metal construction, but nonmetal structure, need structurally to paste sheet metal, this must produce the impact of additional mass and additional stiffness.Therefore, need to propose the contactless modal test system and method for a kind of acoustically-driven, to solve the problem of additional mass and additional stiffness in dynamic analysis modal test.
Summary of the invention
The object of the invention is to there is additional mass and additional stiffness in the modal test for thin-slab construction dynamic analysis, affect test findings accuracy and easily cause the technical matters that structural member damages, provide a kind of contactless modal test system and method for acoustically-driven being particularly useful for thin-slab construction, use loudspeaker to sound and contactless excitation is carried out to thin-slab construction, use sonic transducer to measure acoustical signal, use laser without contact to measure structural vibration response.
The technical scheme realizing the object of the invention is as follows:
The contactless modal test system of a kind of acoustically-driven, comprises a set of loudspeaker, signal source, a set of signal cable, a set of sonic transducer harmony power supply, a set of scanning type laser vibration measuring system and an a set of test cable; Testpieces to be tested is plumbness, and place loudspeaker in testpieces side, loudspeaker is just to testpieces plate face, and signal source is connected with loudspeaker by signal cable, for sending pumping signal, makes testpieces produce vibration; Place scanning type laser vibration measuring system at testpieces opposite side, the laser head of scanning type laser vibration measuring system is just to testpieces plate face; Scanning type laser vibration measuring system measures the vibration signal of each point on testpieces for sending laser point by point scanning, and can record acoustical signal, obtains the modal parameter of testpieces; Sonic transducer hangs between testpieces and loudspeaker, presses close to testpieces but does not contact; Sonic transducer lane testing cable connects acoustic-electric source and scanning type laser vibration measuring system successively.
The distance of described loudspeaker and testpieces is not more than 0.5 meter.
The distance of described scanning type laser vibration measuring system and testpieces is not less than 3 meters or make laser beam flying angle θ be less than 10 degree.
A test method for the contactless modal test system of above-mentioned acoustically-driven, in turn includes the following steps:
The first step: make all devices of pilot system be in "on" position;
Second step: use scanning type laser vibration measuring system, determine the analyzing spot on testpieces plate face;
3rd step: the signal parameter of adjustment signal source, sends out random signal to loudspeaker, the gain of adjustment loudspeaker to increase volume level, scanning type laser vibration measuring system can be detected obvious vibration signal, signal to noise ratio (S/N ratio) reaches more than 20dB;
4th step: check the sound passage that sonic transducer harmony power supply is formed, the gain of adjustment sonic transducer, scanning type laser vibration measuring system can be detected obvious acoustical signal, signal to noise ratio (S/N ratio) reaches more than 20dB;
5th step: arrange scanning document on scanning type laser vibration measuring system, carries out sweep test, obtains the vibration signal of acoustical signal and analyzing spot;
6th step: model analysis
Use that install in scanning type laser vibration measuring system or external modal idenlification software, the acoustical signal obtained using sonic transducer measurement is as input signal, the vibration signal obtained using the measurement of scanning type laser vibration measuring system is as output signal, do frequency response function analysis, and modal parameter is obtained to frequency response function process.
Beneficial effect of the present invention is: adopt the contactless modal test system and method for acoustically-driven of the present invention, solve contactless excitation and non-contact measurement two large problems, avoid the impact of additional mass in conventional mode and additional stiffness, damage is not caused to structure, is applicable to the modal test of thin-slab construction as this kind of in circuit board.Adopt technical scheme of the present invention, there is not the impact of additional mass and additional stiffness, avoid structural failure in modal test, test effect is good, can obtain modal parameter accurately.
Accompanying drawing explanation
Fig. 1 is acoustically-driven of the present invention contactless modal test system composition diagram;
Fig. 2 is frequency response function amplitude frequency diagram;
Fig. 3 is first step mode bending vibation mode picture (frequency is 229Hz).
In figure:
1-loudspeaker, 2-signal source, 3-signal cable, 4-sonic transducer, 5-acoustic-electric source, 6-scanning type laser vibration measuring system, 7-test cable, 8-testpieces.
Embodiment
Below in conjunction with accompanying drawing, technical scheme of the present invention is further described.
Present embodiments provide the contactless modal test system of a kind of acoustically-driven, its composition as shown in Figure 1, comprising: a set of loudspeaker 1, signal source 2, a set of signal cable 3, a set of sonic transducer 4 harmony power supply 5, a set of scanning type laser vibration measuring system 6 and a set of test cable 7; Signal source 2 sends pumping signal to loudspeaker 1 by signal cable 3, is generally random signal.Loudspeaker 1 just sends acoustically-driven to thin plate testpieces 8 plate face, makes thin plate testpieces 8 produce vibration.The acoustical signal that sonic transducer 4 sends for measuring loudspeaker 1, outputs to scanning type laser vibration measuring system 6 by test cable 7 harmony power supply 5.Scanning type laser vibration measuring system 6 measures the vibration signal of each point on thin plate testpieces 8 for sending laser point by point scanning, and can acoustical signal be recorded, install in use scanning type laser vibration measuring system 6 or external model analysis software performs an analysis to acoustical signal and vibration signal, obtains the modal parameter of thin plate testpieces 8.
Above-mentioned acoustically-driven contactless modal test system building method, in turn includes the following steps:
The first step: thin plate testpieces 8 is installed
Thin plate testpieces 8 is vertically mounted in sound chamber in state (free suspension state or clamped state) plate face as requested.
Second step: loudspeaker 1 is placed
In thin plate testpieces 8 side, loudspeaker 1 is just placed thin plate testpieces 8 plate face, and distance thin plate testpieces 8 is in 0.5 meter.
3rd step: scanning type laser vibration measuring system 6 is placed
Place scanning type laser vibration measuring system 6 at the opposite side of thin plate testpieces 8, the laser head of scanning type laser vibration measuring system 6 is just to thin plate testpieces 8 plate face, and distance thin plate testpieces 8, beyond 3 meters, makes laser beam flying angle θ be less than 10 degree.
4th step: sonic transducer 4 is installed and is connected
Sonic transducer 4 uses thin wire to hang on before thin plate testpieces 8, and directional loudspeaker 1, sonic transducer 4 links acoustic-electric source 5 and scanning type laser vibration measuring system 6 by test cable 7.
5th step: signal source 2 connects
Signal source 2 is connected with loudspeaker 1 by signal cable 3, for loudspeaker 1 pumping signal.
Below in conjunction with a specific embodiment, the present invention's " contactless modal test of acoustically-driven " is introduced.
The contactless modal test of acoustically-driven is carried out for the circuit board of certain installment state.
The contactless Modal Experimental Method of described acoustically-driven, in turn includes the following steps:
The first step: circuit board is installed
Circuit board is pressed actual working state and is inserted in draw-in groove, and circuit board is vertical, and draw-in groove is fixed in the track in the middle part of sound chamber.
Second step: loudspeaker 1 is placed
Place loudspeaker 1 in the side of circuit board, loudspeaker 1 is just to circuit board face, and distance circuit board is 0.3 meter.
3rd step: scanning type laser vibration measuring system 6 is placed
Place scanning type laser vibration measuring system 6 at the opposite side of circuit board, the laser head of scanning type laser vibration measuring system 6 is just to sheet panel top face, and distance circuit board 4 meters, laser beam flying angle θ is about 5 degree.
4th step: sonic transducer 4 is installed and is connected
Use before and after two thin wires and bundle sonic transducer 4, hanging on before circuit board, and directional loudspeaker 1, sonic transducer 4 links acoustic-electric source 5 and scanning type laser vibration measuring system 6 by test cable 7.
5th step: signal source connects
Signal source 2 is connected with loudspeaker 1 by signal cable 3, for loudspeaker 1 random excitation signal.
6th step: make all devices such as the loudspeaker 1 of pilot system, signal source 2, sonic transducer 4, acoustic-electric source 5 and scanning type laser vibration measuring system 6 be in "on" position;
7th step: use scanning type laser vibration measuring system 6 pairs of circuit board surface determination analyzing spots;
8th step: adjustment signal source 2 gives loudspeaker 1 random signal, the gain of adjustment loudspeaker 1 allows volume level increase, scanning type laser vibration measuring system 6 can be detected obvious vibration signal, vibration signal signal to noise ratio (S/N ratio) reaches 30dB;
9th step: inspection sound passage, adjustment channel gain, scanning type laser vibration measuring system 6 can be detected obvious acoustical signal, acoustical signal signal to noise ratio (S/N ratio) reaches 30dB.
Tenth step: scanning type laser vibration measuring system 6 arranges scanning document, carries out sweep test, obtains the vibration signal of analyzing spot on acoustical signal and circuit board.
11 step: model analysis
Use that install in scanning type laser vibration measuring system 6 or external modal idenlification software, the acoustical signal that obtains is measured as input signal using sonic transducer 4, the vibration signal that obtains is measured as output signal using scanning type laser vibration measuring system 6, do frequency response function analysis, the frequency response function obtaining circuit board is shown in Fig. 2; Adopt the methods such as the orthogonal polynomial in above-mentioned modal idenlification software to carry out parameter identification to frequency response function, obtain the modal parameter of thin plate testpieces 8, obtain the first step mode vibration shape (frequency is 229Hz) and see Fig. 3.
In modal test for this kind of thin-slab construction of circuit board, for reducing the impact of additional mass and additional stiffness, and avoid structural failure, realize contactless modal test, need to solve how incentive structure, make structure produce motion, and how to go to measure exciting force and this two large problems of response.Conventional vibrator or the excitation of power hammer will inevitably cause the impact of additional mass and additional stiffness maybe may cause damage to structure on structure, thus can not use vibrator or the excitation of power hammer; And adopt electromagnetic non-contact to encourage, to nonmetal structure, need structurally to paste sheet metal, this can produce the impact of additional mass and additional stiffness, thus needs to design new motivational techniques.Also need non-contact measurement to the measurement of exciting force and response, exciting force measuring and design is relevant with energisation mode, and the non-contact measurement of response also needs to introduce new measuring technique.Adopt the contactless modal test system and method for acoustically-driven of the present invention, solve contactless excitation and non-contact measurement two large problems, avoid the impact of additional mass in conventional mode and additional stiffness, damage is not caused to structure, is applicable to the modal test of thin-slab construction as this kind of in circuit board.
For the modal test of thin-slab construction, the contactless Modal Experimental Method of acoustically-driven that the present invention proposes: use loudspeaker contactless excitation thin-slab construction of sounding to make it produce vibration, sonic transducer is used to measure acoustical signal, laser without contact is used to measure structural vibration response, use conventional model analysis software, be input signal with acoustical signal, take vibratory response as output signal, analyze the modal parameter obtaining structure.Owing to there is not the impact of additional mass and additional stiffness in test, it also avoid structural failure, test effect is good, can obtain modal parameter accurately.
The testpieces of the present embodiment is for thin plate testpieces, but the contactless modal test system of acoustically-driven of the present invention is particularly useful for these type of sheet-type testpieces such as circuit board, but its scope of application is not limited thereto, go for the modal test of the testpieces dynamic analysis of other shapes equally.
Obviously, those skilled in the art can carry out various change and modification to the present invention and not depart from the spirit and scope of the present invention.If these amendments and modification belong within the scope of the claims in the present invention and equivalent technologies thereof, then the present invention is also intended to comprise these change and modification.
Claims (6)
1. the contactless modal test system of acoustically-driven, is characterized in that: comprise a set of loudspeaker (1), signal source (2), a set of signal cable (3), a set of sonic transducer (4) harmony power supply (5), a set of scanning type laser vibration measuring system (6) and an a set of test cable (7); Thin plate testpieces (8) to be tested is plumbness, loudspeaker (1) is placed in thin plate testpieces (8) side, loudspeaker (1) is just to thin plate testpieces (8) plate face, signal source (2) is connected with loudspeaker (1), for sending pumping signal by signal cable (3); Place scanning type laser vibration measuring system (6) at thin plate testpieces (8) opposite side, the laser head of scanning type laser vibration measuring system (6) is just to thin plate testpieces (8) plate face; Sonic transducer (4) hangs between thin plate testpieces (8) and loudspeaker (1), presses close to thin plate testpieces (8) but does not contact; Sonic transducer (4) lane testing cable (7) connects acoustic-electric source (5) and scanning type laser vibration measuring system (6) successively.
2. the contactless modal test system of a kind of acoustically-driven as claimed in claim 1, is characterized in that: described loudspeaker (1) is not more than 0.5 meter with the distance of thin plate testpieces (8).
3. the contactless modal test system of a kind of acoustically-driven as claimed in claim 2, is characterized in that: described loudspeaker (1) is 0.3 meter with the distance of thin plate testpieces (8).
4. the contactless modal test system of a kind of acoustically-driven as claimed in claim 1, is characterized in that: the distance of described scanning type laser vibration measuring system (6) and thin plate testpieces (8) is not less than 3 meters or make laser beam flying angle θ be less than 10 degree.
5. the contactless modal test system of a kind of acoustically-driven as claimed in claim 1, is characterized in that: described scanning type laser vibration measuring system (6) is 4 meters with the distance of thin plate testpieces (8) or makes laser beam flying angle θ be 5 degree.
6. a test method for the contactless modal test system of acoustically-driven as claimed in claim 1, in turn includes the following steps:
The first step: make all devices of pilot system be in "on" position;
Second step: use scanning type laser vibration measuring system (6), determine the analyzing spot on testpieces (8) plate face;
3rd step: the signal parameter of adjustment signal source (2), random signal is sent out to loudspeaker (1), the gain of adjustment loudspeaker (1) is to increase volume level, scanning type laser vibration measuring system (6) can be detected obvious vibration signal, signal to noise ratio (S/N ratio) reaches more than 20dB;
4th step: check the sound passage that sonic transducer (4) harmony power supply (5) is formed, adjustment sonic transducer (4) gain, scanning type laser vibration measuring system (6) can be detected obvious acoustical signal, signal to noise ratio (S/N ratio) reaches more than 20dB;
5th step: scanning document is set on scanning type laser vibration measuring system (6), carries out sweep test, obtain the vibration signal of acoustical signal and analyzing spot;
6th step: model analysis
Use that install in scanning type laser vibration measuring system (6) or external modal idenlification software, the acoustical signal that obtains is measured as input signal using sonic transducer (4), the vibration signal that obtains is measured as output signal using scanning type laser vibration measuring system (6), do frequency response function analysis, and modal parameter is obtained to frequency response function process.
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| CN105701278A (en) * | 2016-01-05 | 2016-06-22 | 东华大学 | Modal parameter acquisition method |
| CN106370293A (en) * | 2016-11-04 | 2017-02-01 | 山西大学 | Measurement system and decomposition method for integral sound vibration and firmware vibration of violin |
| CN107860539A (en) * | 2017-10-13 | 2018-03-30 | 郑州轻工业学院 | A kind of Modal Experimental Method for eliminating additional mass and influenceing |
| CN107991080A (en) * | 2017-12-05 | 2018-05-04 | 中国人民解放军总参谋部第六十研究所 | A kind of high frequency Modal Analysis on Blade method based on non-contact vibration measuring and simulation calculation |
| CN108168868A (en) * | 2017-12-29 | 2018-06-15 | 绍兴文理学院 | A kind of method for detecting the Steel section member natural frequency of vibration |
| CN108489696A (en) * | 2018-03-26 | 2018-09-04 | 东南大学 | A kind of method of spring additional stiffness in elimination frequency response function |
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| CN105701278A (en) * | 2016-01-05 | 2016-06-22 | 东华大学 | Modal parameter acquisition method |
| CN106370293A (en) * | 2016-11-04 | 2017-02-01 | 山西大学 | Measurement system and decomposition method for integral sound vibration and firmware vibration of violin |
| CN107860539A (en) * | 2017-10-13 | 2018-03-30 | 郑州轻工业学院 | A kind of Modal Experimental Method for eliminating additional mass and influenceing |
| CN107991080A (en) * | 2017-12-05 | 2018-05-04 | 中国人民解放军总参谋部第六十研究所 | A kind of high frequency Modal Analysis on Blade method based on non-contact vibration measuring and simulation calculation |
| CN108168868A (en) * | 2017-12-29 | 2018-06-15 | 绍兴文理学院 | A kind of method for detecting the Steel section member natural frequency of vibration |
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| CN108731891A (en) * | 2018-05-30 | 2018-11-02 | 东北大学 | The free boundary of plane sound wave excitation is got off the plane siding vibrating device and application method |
| CN110108504A (en) * | 2019-05-13 | 2019-08-09 | 桂林电子科技大学 | The non-contact excitation of cargo vehicle body mode and non-cpntact measurement acquisition methods |
| CN111323111A (en) * | 2020-03-11 | 2020-06-23 | 北京空间飞行器总体设计部 | Modal test system suitable for film antenna under vacuum environment |
| CN113483977A (en) * | 2021-06-28 | 2021-10-08 | 北京强度环境研究所 | Acoustic characteristic testing device for light and thin structure |
| CN115266419A (en) * | 2022-08-17 | 2022-11-01 | 哈尔滨工业大学 | Device and method for researching ultra-low cycle impact fatigue test based on modal test |
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