CN103091402A - Acoustic measurement method and device for dynamic stiffness of woodworking band saw blade - Google Patents

Abstract

The invention provides acoustic measurement method and device for the dynamic stiffness of a woodworking band saw blade, and the method and the device are simple, accurate and reliable in measuring data. The method comprises the following steps of: knocking the woodworking band saw blade by using a force hammer with a force sensor to ensure that the woodworking band saw blade is horizontally vibrated; receiving and transforming acoustic wave caused by the vibration of the woodworking band saw blade into an electrical signal G by using a sound level meter, carrying out data collection and spectral analysis after processing the electrical signal G and the signal of reflecting the knocking force, detected by the force sensor, of the force hammer so as to obtain a frequency domain graph of dynamic stiffness amplitude A=T/G; obtaining a frequency f of a certain order and the dynamic stiffness amplitude A corresponding to the frequency f of the order through the frequency domain graph; and calculating the dynamic stiffness effective value at the frequency f of the order.

Description

Acoustic measurement method and the measurement mechanism of band saw bar dynamic stiffness

Technical field

The present invention relates to measuring method and the measurement mechanism of band saw bar dynamic stiffness, specifically, is acoustic measurement method and the measurement mechanism of band saw bar dynamic stiffness.

Background technology

Wood working band sawing machine as the first operation of timber process, is equipment most widely used in wood working industry.Therefore, the quality of the mechanical properties such as research band-sawing machine rigidity, comparatively crucial for improving working (machining) efficiency and taking full advantage of material.The stressed extremely complexity of band saw bar, resonance can occur and rock (buffeting) in saw when separating operation, and this will affect saw solution quality, therefore particularly important to the vibration Characteristics of bands for band.

Dynamic stiffness is to describe the key index of physical construction damping property, reflects the ability of its resistance to deformation under specific dynamically excitation.By the definition of dynamic stiffness as can be known, the unit of dynamic stiffness should be N/m, and its computing formula simplifying through the triangle complex exponential form after calculating is: E=A/ (2 π f) ²In formula, E represents dynamic stiffness (N/m); A represents dynamic stiffness amplitude (N/m/s ²); F represents frequency (Hz).

In order to measure dynamic stiffness, generally need to fix a sensor on test specimen, react the response signal of test specimen by the response signal (as acceleration) that this sensor records, then this signal is processed the dynamic stiffness that calculates test specimen.But because sensor is attached on test specimen, the response signal of test specimen is because the impact of sensor additional mass makes its measured value not too accurate.

Summary of the invention

The purpose of this invention is to provide that a kind of method is simple, test data is accurate and the acoustic measurement method of reliable band saw bar dynamic stiffness.

The acoustic measurement method of band saw bar dynamic stiffness of the present invention is that the power hammer that the power sensor is housed knocks the band saw bar, makes band saw bar transverse vibration; Receive the sound wave of band saw bar generation of vibration and change electric signal G into sound meter, carry out data collection and spectrum analysis after the signal of the antistress hammer percussion power T size that again electric signal G and power sensor is detected is processed, obtain the frequency domain figure of dynamic stiffness amplitude A=T/G; Draw certain order frequency f and the dynamic stiffness amplitude A corresponding with this order frequency f from this frequency domain figure; With

Calculate the dynamic stiffness effective value under this order frequency f.

The beneficial effect of this acoustic measurement method: the power hammer encourages measuring object-band saw bar by the sinusoidal interference power of a series of different frequencies.Just resonate when the frequency of exciting force equals system frequency, the peak occurs responding; When the frequency of exciting force was not equal to system frequency, its amplitude was just necessarily less than resonance peak.The frequency spectrum of response obtains frequency response function divided by the power pulse.Frequency response function is the response under unit force, and its inverse is exactly the power that needs under unit response, i.e. dynamic stiffness.Dynamic stiffness is a curve relevant to natural frequency.As expect that frequency response function responds/power exactly; If the dynamic stiffness of expecting is exactly power/response.If the structure of different materials, different size and shape is knocked, the frequency that knocks is different.During measurement, knock the band saw bar, make it produce Free Transverse and sound, receive sound pressure signal and it is become electric signal by this sensor of sound meter.Because sound meter is a non-contact sensor that does not contact with the band saw bar, the relevant parameters (as the natural frequency value) of the reaction carpenter bands for band that it records, with respect to prior art (sensor is fixed on the band saw bar tests), because the band saw bar does not have the impact of sensor additional mass, so measured value is more accurate.

Above-mentioned acoustic measurement method, the probe of sound meter and the distance of bands for band are 1cm.Test is more accurate like this.

Above-mentioned acoustic measurement method, the SsCras signals and systems analysis software that adopts the Nanjing positive soft project of peace Ltd to electric signal process, data acquisition and spectrum analysis.Adopt the SsCras signals and systems analysis software of the Nanjing positive soft project of peace Ltd to carry out the dynamic stiffness test, the frequency spectrum wave crest, the trough that obtain are clear and legible, clear dynamic stiffness of having reacted exactly test specimen.

Above-mentioned acoustic measurement method, described certain rank natural frequency f refers to single order, second order, three rank, quadravalence or five rank natural frequencys.

Above-mentioned acoustic measurement method, sound meter measurement range 35-90dB, frequency range 31.5HZ-8000HZ, accuracy is ± 1.5dB that resolution is 0.1dB.Test result is more accurate like this.

The present invention also provide a kind of simple in structure, test data is accurate and the acoustic measurement device of reliable band saw bar dynamic stiffness.

The acoustic measurement device of this band saw bar dynamic stiffness comprises the power hammer of the power that the is equipped with sensor that knocks the band saw bar, be arranged on band saw bar one side reception band saw bar generation of vibration sound wave and change the sound meter of electric signal into; The output of power sensor and sound meter all connects the signal condition instrument, and the output of signal condition instrument connects signals collecting and analyser.

Above-mentioned device for testing dynamic stiffness, signal condition instrument comprise the amplifier that the electric signal for sound meter output carries out the wave filter of filtering, filtered signal is amplified.

Above-mentioned device for testing dynamic stiffness, signals collecting and analyser comprise signal sampler and signal processing analysis instrument; Signal sampler has computer interface, dsp chip, A/D converter; The signal processing analysis instrument comprises the CPU processor; Amplifier, computer interface, dsp chip, A/D converter, CPU processor are connected successively.

Above-mentioned device for testing dynamic stiffness, sound meter measurement range 35-90dB, frequency range 31.5HZ-8000HZ, accuracy is ± 1.5dB that resolution is 0.1dB.

Description of drawings

Fig. 1 is band saw bar system dynamic stiffness performance test block diagram

Fig. 2 is the dynamic stiffness spectrogram of band saw bar system;

Fig. 3 is dynamic stiffness amplitude and the phase diagram of band saw bar system.

Embodiment

Embodiment: the acoustic wave excitation method is measured the bands for band dynamic stiffness of MJ397 type wood working band sawing machine.

1 testing equipment and instrument

1.1 testing equipment

This testing equipment is the MJ397 type wood working band sawing machine that Shanxi fellow worker group produces, and important technological parameters sees Table 1.Its band saw wheel tensile force is 3543.79N.

The important technological parameters table of table 1 MJ397 type wood working band sawing machine

The band saw bar is straight back of the body profile of tooth, and material is 65Mn.Its effective width (not containing tooth depth) b=76.5mm, thickness s=1.05mm, total length L=5400mm, tooth pitch t=37mm, tooth depth h=13.7mm; 3 basic angles of sawtooth are: throat of tooth angle=25 °, tooth angle=45 °, Clearance angle=20 °.

1.2 the positive CRAS vibration of Nanjing peace and dynamic signal acquisition analytic system

(the Nanjing positive soft project of peace Ltd) CRAS vibration is just being pacified in Nanjing and the dynamic signal acquisition analytic system is comprised of signal condition instrument 1, signal sampler 2, SsCras signals and systems analysis software 3 and computing machine 4 etc.Signal condition instrument 1 comprises anti alias filter and signal amplifier, and signal sampler 2 has computer interface, digital signal device processing DSP chip, A/D converter etc.The signal processing analysis instrument comprises the CPU processor in computing machine 4 etc.

Anti alias filter carries out filtering with the output signal of sound meter, then the signal entering signal Acquisition Instrument 2 after signal amplifier amplifies.The simulating signal that collects machine interface as calculated enters digital signal device processing DSP chip and carries out digital signal processing, then convert digital signal to through A/D converter, the signal input part by the CPU processor in the signal processing analysis instrument enters the CPU processor and carries out Treatment Analysis by CPU processor and system controlling software thereof.

1.3 TES135 type sound meter

Sound meter is by probe, prime amplifier, attenuator, amplifier, frequency weighting network and the effective value indicating gauge is first-class forms, its measurement range L ₀=35-90dB, frequency range 31.5HZ-8000HZ, accuracy is ± 1.5dB, and resolution is 0.1dB, adopts inner 94dB position correction, and this test is only made sound meter microphone and is used.

1.4 1 of the rubber hammer of power sensor is housed.

2 test methods and procedures

2.1 method of testing and principle

Dynamic stiffness is to describe the key index of damping property, and expression causes the needed dynamic force of unit amplitude.Under static load, the ability of resistance to deformation is called quiet rigidity; Under dynamic loading, the ability of resistance to deformation is called dynamic stiffness, weighs with the natural frequency of structure.If it is very slow that dynamic deformation from motion changes, when namely the frequency that changes of dynamic deformation from motion is much smaller than the natural frequency of structure, can think that dynamic stiffness and quiet rigidity are basic identical.Otherwise the frequency of dynamic deformation from motion is during much larger than the natural frequency of structure, and structure is not easy distortion, i.e. distortion is less, and this moment, the relative excitation of dynamic stiffness of structure was larger.But when the frequency of dynamic deformation from motion is close with the natural frequency of structure, resonance effect might occur, this moment, dynamic stiffness was minimum, and distortion is maximum.

By the definition of dynamic stiffness as can be known, the unit of dynamic stiffness should be N/m, and its computing formula simplifying through the triangle complex exponential form after calculating is: E=A/ (2 π f) ²In formula, E represents dynamic stiffness (N/m); A represents dynamic stiffness amplitude (N/m/s ²); F represents frequency (Hz).

If the structure of different materials, different size and shape is knocked, the frequency that knocks is different.Evidence is carried out the resulting frequency values of spectrum analysis to knock consistent with the natural frequency that mechanical pick-up device obtains.Use sound meter identical with the use acceleration transducer as the experimental principle of sensor, still, because sound meter is a non-contact sensor, the natural frequency value that it obtains makes its measured value more accurate because there is no the impact of sensor additional mass.During test, referring to Fig. 1, knock the band saw bar 6 that is contained on saw wheel 5 with the rubber hammer 8 that the power sensor is housed, make it produce Free Transverse and sound, receive sound pressure signal and it is become electric signal G by this sensor of sound meter 7.Signal and the electric signal G of the antistress hammer percussion power T size of power sensor detection are amplified through signal condition instrument 1, after filtering, carry out data acquisition and spectrum analysis, obtain the frequency domain figure of dynamic stiffness amplitude A=T/G; Draw certain order frequency f and the dynamic stiffness amplitude A corresponding with this order frequency f from this frequency domain figure.

2.2 test process

In test, band-sawing machine is in not open state.Its key step is as follows:

(1) the sound meter sensor needs calibration before use.At first press the white button of acoustic calibrator, acoustic calibrator can send the 1000Hz frequency, the normal data of 94dB; Then sound meter is opened to be allocated to and regulated shelves, detecting head is inserted in the hole of acoustic calibrator; At last, with the adjusting knob of bottle opener rotation sound meter, the registration of sound meter microphone is adjusted to 94dB, the sound meter calibration finishes.

(2) before the test, sound meter is popped one's head in parallel apart from bands for band B=1cm place's placement.

(3) connect each instrument and equipment, this rubber hammer produces pumping signal (CH2), and CH2 unit is (N).Sound meter should avoid being placed on the Nodes such as 1/2 or 1/4 place of bands for band width when mounted, and what make sound meter probe and bands for band is 1cm apart from B, sound meter acceptance response signal (CH1), and CH1 unit is made as (m/s ²).During test, rubber hammer knocks the band saw bar that is contained on saw wheel in the suitable distance of distance sound meter with suitable dynamics.Call signal and systematic analysis software arrange in the acquisition parameter of vibration signal, adopt 1/H ₁Pattern, triggering mode triggers for negative, and voltage range is ± 5000mV that the correction factor of sound meter is 320, enlargement factor 10, analysis frequency 500Hz, data acquisition number of times 4, data block length 2048.

(4) repeatedly mixed for preventing frequency, the upper frequency limit of low-pass filter is selected in this test, and frequency filtering is made as 500Hz; Whether before actual measurement, enter the oscillography mode, knock continuously test specimen, connect with the inspection apparatus connecting line, whether waveform is reasonable etc., will reset it when unreasonable;

(5) after oscillography is errorless, enter data acquisition modes.By using rubber hammer; Knock bands for band, evoke the bands for band system vibration, with the triggering mode image data, and read respectively natural frequency value and the dynamic stiffness amplitude on front 8 rank according to its dynamic stiffness spectrogram, dynamic stiffness amplitude figure, and record.

3 results and analysis

Adopt acoustic wave excitation method measurement MJ397 type wood working band sawing machine bands for band structural system dynamic stiffness amplitude and phase place as described in Figure 3, the dynamic stiffness frequency spectrum as shown in Figure 2.As shown in Figure 2, the horizontal ordinate of the CH1 sound meter passage in the dynamic stiffness frequency spectrum represents analysis frequency (Hz), and ordinate represents respectively the amplitude (m/s of band saw bar vibration ²).The horizontal ordinate of CH2 rubber hammer meter passage represents analysis frequency (Hz), and ordinate represents respectively the amplitude (N) of percussion power.As shown in Figure 3, in the dynamic stiffness phase diagram, horizontal ordinate represents analysis frequency (Hz), ordinate phase place.In dynamic stiffness amplitude figure, horizontal ordinate represents analysis frequency (Hz), and ordinate represents the amplitude (N/m/s of dynamic stiffness ²).

Read front 8 rank natural frequencys and corresponding dynamic stiffness amplitude by Fig. 3: the fundamental frequency f of its system ₁=26.25Hz, f ₂=41.25Hz, f ₃=51.25Hz, f ₄=125.00Hz, f ₅=143.75Hz, f ₆=167.50Hz, f ₇=223.75Hz, f ₈=306.25Hz; Its dynamic stiffness amplitude A ₁=74.00N/ms ^-2, A ₂=83.40N/ms ^-2, A ₃=79.08N/ms ^-2, A ₄=72.68N/ms ^-2, A ₅=85.63N/ms ^-2, A ₆=77.31N/ms ^-2, A ₇=84.99N/ms ^-2, A ₈=97.19N/ms ^-2

The dynamic stiffness effective value E of this bands for band system _{Rms (n)}Be calculated as follows:

f ₁Under=26.25Hz, $E_{\mathrm{rms}\left(1\right)}=\frac{A_1}{{\left(2\mathrm{\π}{f}_1\right)}^2}=\frac{74.00}{{(2\×3.14\×26.25)}^2}=0.002720N/m;$

f ₂Under=41.25Hz, $E_{\mathrm{rms}\left(2\right)}=\frac{A_2}{{\left(2\mathrm{\π}{f}_2\right)}^2}=\frac{83.40}{{(2\×3.14\×41.25)}^2}=0.001241N/m;$

f ₃Under=51.25Hz, $E_{\mathrm{rms}\left(3\right)}=\frac{A_3}{{\left(2\mathrm{\π}{f}_3\right)}^2}=\frac{79.08}{{(2\×3.14\×51.25)}^2}=0.000770N/m;$

f ₄Under=125.00Hz, $E_{\mathrm{rms}\left(4\right)}=\frac{A_4}{{\left(2\mathrm{\π}{f}_4\right)}^2}=\frac{72.68}{{(2\×3.14\×125.00)}^2}=0.000118N/m;$

f ₅Under=143.75Hz, $E_{\mathrm{rms}\left(5\right)}=\frac{A_5}{{\left(2\mathrm{\π}{f}_5\right)}^2}=\frac{85.63}{{(2\×3.14\×143.75)}^2}=0.000105N/m;$

f ₆Under=167.50Hz, $E_{\mathrm{rms}\left(6\right)}=\frac{A_6}{{\left(2\mathrm{\π}{f}_6\right)}^2}=\frac{77.31}{{(2\×3.14\×167.50)}^2}=0.000070N/m;$

F ₇Under=223.75Hz, $E_{\mathrm{rms}\left(7\right)}=\frac{A_7}{{\left(2\mathrm{\π}{f}_7\right)}^2}=\frac{84.99}{{(2\×3.14\×223.75)}^2}=0.000038N/m;$

F ₈Under=306.25Hz, $E_{\mathrm{rms}\left(8\right)}=\frac{A_8}{{\left(2\mathrm{\π}{f}_8\right)}^2}=\frac{97.19}{{(2\×3.14\×306.25)}^2}=0.000026N/m$

The first eight rank natural frequency, the dynamic stiffness amplitude of the bands for band system that adopts that the acoustic wave excitation method records, and calculate the dynamic stiffness value show, dynamic stiffness performance under its fundamental frequency is maximum, and namely the rigidity of the bands for band system in 26.25Hz half-power region is best, and this moment, the bands for band deflection was little.

Claims (9)

1. the acoustic measurement method of band saw bar dynamic stiffness, is characterized in that: knock the band saw bar with the power hammer that the power sensor is housed, make band saw bar transverse vibration; Receive the sound wave of band saw bar generation of vibration and change electric signal G into sound meter, carry out data collection and spectrum analysis after the signal of the antistress hammer percussion power T size that again electric signal G and power sensor is detected is processed, obtain the frequency domain figure of dynamic stiffness amplitude A=T/G; Draw certain order frequency f and the dynamic stiffness amplitude A corresponding with this order frequency f from this frequency domain figure; With

Calculate the dynamic stiffness effective value under this order frequency f.

2. acoustic measurement method as claimed in claim 1, it is characterized in that: the probe of sound meter and the distance of bands for band are 1cm.

3. acoustic measurement method as claimed in claim 1 is characterized in that: the SsCras signals and systems analysis software that adopts the Nanjing positive soft project of peace Ltd to electric signal process, data acquisition and spectrum analysis.

4. as claim 1,2 or 3 described acoustic measurement methods, it is characterized in that: sound meter measurement range 35-90dB, frequency range 31.5HZ-8000HZ, accuracy is ± 1.5dB that resolution is 0.1dB.

5. as claim 1,2 or 3 described acoustic measurement methods, it is characterized in that: described certain rank natural frequency f refers to single order, second order, three rank, quadravalence or five rank natural frequencys.

6. the acoustic measurement device of band saw bar dynamic stiffness, it is characterized in that: it comprises: knock the power hammer of the power that the is equipped with sensor of band saw bar, be arranged on band saw bar one side reception band saw bar generation of vibration sound wave and change the sound meter of electric signal into; The output of power sensor and sound meter all connects the signal condition instrument, and the output of signal condition instrument connects signals collecting and analyser.

7. device for testing dynamic stiffness as claimed in claim 6 is characterized in that: the signal condition instrument comprises the amplifier that the signal to the electric signal of sound meter output and the output of power sensor carries out the wave filter of filtering, filtered signal is amplified.

8. device for testing dynamic stiffness as claimed in claim 7, it is characterized in that: signals collecting and analyser comprise signal sampler and signal processing analysis instrument; Signal sampler has computer interface, dsp chip, A/D converter; The signal processing analysis instrument comprises the CPU processor; Amplifier, computer interface, dsp chip, A/D converter, CPU processor are connected successively.

9. device for testing dynamic stiffness as claimed in claim 6 is characterized in that: sound meter measurement range 35-90dB, and frequency range 31.5HZ-8000HZ, accuracy is ± 1.5dB that resolution is 0.1dB.

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