JP5176464B2 - Method for evaluating vibration damping performance of objects - Google Patents

Description

  The present invention relates to a method for evaluating vibration damping performance of an object.

Conventionally, various methods for evaluating the vibration damping performance of an object have been proposed.
For example, an acceleration pickup is attached to an object, the object is freely vibrated by hitting the object with an impulse hammer, and a frequency response function is calculated from the force waveform measured by the impulse hammer and the acceleration waveform measured by the acceleration pickup. There has been proposed a method of measuring and determining a loss coefficient (attenuation performance) from the half-value width of the resonance curve.
In addition, the object is vibrated by exciting the object with the vibrator, and the frequency response function is measured from the force waveform measured by the force transducer attached to the vibrator and the acceleration waveform measured by the acceleration pickup. A method for obtaining the loss factor from the half-value width of the resonance curve has been proposed.
However, the above-described two methods have a disadvantage that the number of data sufficient to accurately calculate the half-width of the resonance curve cannot be obtained when the resonance curve has an extremely steep waveform with the resonance frequency as a peak.

Further, the position of the vibration mode corresponding to the primary resonance frequency, the secondary resonance frequency, the tertiary resonance frequency,... A method has been proposed to calculate the loss factor for each resonance frequency by exciting the object at each frequency and obtaining the attenuation factor for each resonance frequency based on the envelope connecting the peak levels of the measured vibration waveform. (See Patent Document 1).
JP-A 63-250548

However, in the above-described prior art, it is necessary to specify the fine adjustment of the position of the nodes of the first and second vibration modes and the resonance frequency of the object, and to specify the resonance frequency by actual measurement, so that the apparatus for exciting the object is complicated. In addition to being expensive, the work for actual measurement is complicated.
The present invention has been made in view of such circumstances, and an object of the present invention is to vibrate the object which is advantageous in accurately evaluating the vibration damping performance of the object while reducing the cost and improving the work efficiency. It is to provide a damping performance evaluation method.

In order to achieve the above object, the present invention provides an evaluation method for evaluating vibration attenuation performance of an object using a computer based on a vibration waveform of the object that vibrates freely. Means, processing means for processing data input by the input means, and output means for outputting data supplied from the processing means, wherein the processing means inputs the input means via the input means Fourier transform data for generating amplitude characteristic data indicating the vibration amplitude level with respect to the vibration frequency and phase characteristic data indicating the vibration phase with respect to the vibration frequency by performing fast Fourier transform on the vibration data indicating the vibration waveform. Including a generation step and a primary resonance frequency and a secondary or higher resonance frequency of the object based on the amplitude characteristic data. A resonance frequency specifying step for specifying a plurality of resonance frequencies, a bandpass filter setting step for setting a bandpass filter having the resonance frequency as a center frequency corresponding to each of the plurality of resonance frequencies, and the amplitude characteristic data Each of the plurality of bandpass filters to generate resonance frequency-specific amplitude characteristic data corresponding to each of the plurality of resonance frequencies from each bandpass filter; Resonance frequency-specific vibration waveform generation corresponding to each of the plurality of resonance frequencies by performing inverse fast Fourier transform based on each of the resonance frequency-specific amplitude characteristic data and the phase characteristic data Each of the step and the plurality of vibration waveforms by resonance frequency Correspondingly, a loss coefficient output step generated the loss factor of the loss factor η of attenuation rate D generated based on the peak level of the vibration of the resonant frequency vibration waveform η output via the output means including In order to generate the attenuation factor D in the loss factor output step, the square of the peak level of the vibration of the resonance frequency vibration waveform is converted to a common logarithm and then multiplied by 10 to obtain a straight line approximation to obtain the slope of the straight line. It is made in.

  According to the present invention, frequency amplitude characteristic data for each resonance frequency can be obtained from vibration data indicating the vibration waveform of an object that vibrates freely, and a loss factor η can be calculated for each resonance frequency from each frequency frequency characteristic data for each resonance frequency. Therefore, it is of course advantageous to reduce the cost and increase the efficiency of work, and to accurately evaluate the vibration damping performance of the object.

Next, an object vibration damping performance evaluation method according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is an explanatory diagram showing the configuration of an evaluation system for executing the method of the present invention.
As shown in FIG. 1, the evaluation system includes a clamp 4, an acceleration sensor 6, an amplifier 8, an FFT analyzer 10, and a computer 12.
In the present embodiment, the object 2 to be evaluated for vibration damping performance has an elongated cylindrical shape, and is specifically a golf club shaft.
The clamp 4 fixes the one end of the longitudinal direction of the object 2 so that attachment or detachment is possible.
The acceleration sensor 6 is attached to a location near the other end in the longitudinal direction of the object 2 (in this embodiment, the location of the outer peripheral surface of the object 2), detects the acceleration generated by the vibration of the object 2, and outputs a detection signal. Output.
The amplifier 8 amplifies the detection signal and generates vibration data indicating the vibration waveform of the object 2.
The FFT analyzer 10 is connected to a computer 12 and A / D converts the vibration data supplied from the amplifier 8 and stores it in the memory of the FFT analyzer 10, and reads and outputs the vibration data stored in the memory. In this embodiment, this data logger function is used.
The FFT analyzer 10 performs a fast Fourier transform on the A / D converted vibration data, thereby generating amplitude characteristic data indicating the vibration amplitude level with respect to the vibration frequency, and displaying it on the display of the FFT analyzer 10. Of course we have.

FIG. 2 is a block diagram showing the configuration of the computer 12 used for executing the method of the present invention.
The computer 12 includes a CPU 14, a ROM 16, a RAM 18, a hard disk device 20, a disk device 22, a keyboard 24, a mouse 26, a display 28, a printer 30, an input / output interface 32, and the like connected via an interface circuit (not shown) and a bus line. have.
The ROM 16 stores a control program and the like, and the RAM 18 provides a working area.
The hard disk device 20 stores an evaluation program for realizing the object vibration damping performance evaluation method according to the present invention.
The disk device 22 records and / or reproduces data on a recording medium such as a CD or a DVD.
The keyboard 24 and the mouse 26 receive an operation input by the operator.
The display 28 displays and outputs data, and the printer 30 prints and outputs data. The display 28 and the printer 30 output data.
The input / output interface 32 exchanges data with the FFT analyzer 10 which is an external device.
In the present embodiment, the CPU 14 and the input / output interface 32 constitute a claim input means, and the CPU 14 constitutes a claim processing means. The CPU 14, display 28, printer 30, input / output interface 32, etc. Constitutes the output means of the claims.

Next, a method for evaluating the vibration damping performance of an object will be described with reference to the flowchart of FIG.
As shown in FIG. 1, it is assumed that one end of the object 2 in the longitudinal direction is fixed by a clamp 4 and an acceleration sensor 6 is attached to an outer peripheral surface near the other end of the object 2.
First, a portion near the other end of the object 2 is vibrated to cause the object 2 to freely vibrate (step S10).
Various methods of exciting the object 2 are conceivable. For example, you may vibrate by striking the location near the other end of the object with a hammer. Alternatively, when the object 2 is likely to be elastically deformed like a golf club shaft, it is difficult to vibrate with a hammer, so that the operator puts his finger on the other end in the longitudinal direction of the object 2 and plays it. The method of exciting with is good.
That is, when the object 2 is vibrated, the object 2 is elastically deformed by applying a force in a direction perpendicular to the longitudinal direction to the other end of the object 2 while the one end of the object 2 is fixed. Then, the object 2 is vibrated by instantaneously removing the force, so that it vibrates freely.
As a result, the detection signal detected by the acceleration sensor 6 is supplied to the amplifier 8, vibration data indicating the vibration waveform of the object 2 is generated by the amplifier 8, supplied to the FFT analyzer 10, and vibration data is measured (step) S12).

Next, vibration data is input from the FFT analyzer 10 to the computer 12 (step S14).
FIG. 4 is a waveform diagram showing vibration data measured from the object 2 that freely vibrates in step S12. 4 and 7 showing the vibration data, the horizontal axis represents time T (seconds) and the vertical axis represents acceleration A (V).
As shown in FIG. 4, the vibration data measured by the acceleration sensor 6 shows a vibration waveform in which the amplitude of vibration gradually decreases with time.

Next, the processing means of the computer 12 generates Fourier transform data by performing fast Fourier transform on the vibration data indicating the input vibration waveform (step S16: amplitude characteristic data generation step).
The Fourier transform data includes amplitude characteristic data indicating the vibration amplitude level with respect to the vibration frequency, and phase characteristic data indicating the vibration phase with respect to the vibration frequency.
Since the fast Fourier transform process itself is a conventionally known method, a detailed description is omitted. However, the fast Fourier transform obtains a Fourier coefficient from vibration data indicating a vibration waveform, and calculates the Fourier coefficient to calculate the amplitude for each frequency. And the phase.
Here, what represents the relationship between the frequency and the amplitude is amplitude characteristic data indicating the amplitude level of vibration with respect to the frequency of vibration.
FIG. 5 is a diagram showing the amplitude characteristic data generated in step S16 (amplitude characteristic data generation step). In FIG. 5, the horizontal axis represents the vibration frequency f (Hz), and the vertical axis represents the amplitude (power spectrum) (dB) of the vibration amplitude.
Next, the processing means specifies a plurality of resonance frequencies including a primary resonance frequency and a secondary or higher resonance frequency of the object based on the amplitude characteristic data (step S18: resonance frequency specifying step).
That is, as shown in FIG. 5, by specifying the frequency values corresponding to the plurality of peak values included in the amplitude characteristic data, the primary resonance frequency f1, the secondary resonance frequency f2, and the tertiary resonance frequency wavenumber f3. , ... is specified.
In the present embodiment, the amplitude of the fourth or higher order resonance frequency is so small that it can be ignored as compared with the amplitudes of the first to third resonance frequencies f1, f2, and f3.
Therefore, in the following, the primary to tertiary resonance frequencies f1, f2, and f3 that have a large influence on the vibration waveform are evaluated, and the fourth and higher order resonance frequencies that can almost ignore the influence on the vibration waveform are evaluated. However, it is arbitrary how many resonance frequencies are evaluated.

Next, the processing means sets a bandpass filter having the resonance frequency as a center frequency corresponding to each of the primary to tertiary resonance frequencies f1, f2, and f3 specified in step S18 (step S20: band). Path filter setting step).
FIG. 6 is an explanatory diagram of a bandpass filter.
In FIG. 6, the horizontal axis represents frequency and the vertical axis represents filter value. The filter value corresponds to a gain. For example, if the filter value is 0, the input signal is blocked by 100%, if the filter value is 0.5, the input signal passes 50%, and if the filter value is 1. 100% of the input signal is passed.
As shown in FIG. 6, the characteristics of the bandpass filter are defined by the center frequency f _C , the lower limit cutoff frequency f _L, and the upper limit cutoff frequency f _H.
Therefore, a bandpass filter with a center frequency fc = f1, a bandpass filter with a center frequency fc = f2, and a bandpass with a center frequency fc = f3 corresponding to the resonance frequencies f1, f2, and f3 specified in step S18. Set the filter. In FIG. 6, the description is omitted because the center frequency f _C , the lower limit cutoff frequency f _L, and the upper limit cutoff frequency f _{H of the} bandpass filter having the third resonance frequency f 3 exceed the frequency display range. ing.

The lower limit cutoff frequency f _L and the upper limit cutoff frequency f _H are set as follows.
In the present embodiment, the characteristics of the bandpass filter are defined by the following equations (1) and (2).
f _L = f _C · 2 ^(−1/6) (1)
f _H = f _C · 2 ^(1/6) (2)
In other words, the lower limit cutoff frequency _{f L} and upper cut-off frequency _{f H} is in 1/3 octave relationship.
That is, the lower cutoff frequency f _L and upper cut-off frequency f _H in the following equation (3) and (4) the relationship.
f _H = (2) ^1/3 · f _L (3)
f _C = (f _L · f _H ) ^1/2 (4)
This is the same as the concept of the 1/3 octave standard defined in JISC1513. However, in the above-mentioned standard, while the center frequency f _c are predetermined, in this embodiment, that the center frequency f _c is determined by the step S18 is different from the above-mentioned standard.
The band-pass filter only needs to be able to accurately separate the vibration waveform of the target resonance frequency component from the amplitude characteristic data shown in FIG. 5, and the lower-limit cutoff frequency f _L and the upper-limit cutoff of the band-pass filter. how to set the frequency f _H is arbitrary.

Next, the processing means inputs the amplitude characteristic data shown in FIG. 5 to each of the three bandpass filters set in step S20, thereby causing the three resonance frequencies (first, second, Resonance frequency-specific amplitude characteristic data corresponding to each of the tertiary resonance frequencies f1, f2, and f3) is generated (step S22: Resonance frequency-specific amplitude characteristic data generation step).
Next, the processing means performs inverse fast Fourier transform on the basis of each of the three resonance frequency-specific amplitude characteristic data generated in step S22 and the phase characteristic data obtained in step S16, thereby providing three resonance frequencies ( A vibration waveform for each resonance frequency corresponding to each of the first, second, and third resonance frequencies f1, f2, and f3) is generated (step S24: vibration waveform generation step for each resonance frequency).
FIG. 7A shows a vibration waveform for each resonance frequency corresponding to the primary resonance frequency f1, FIG. 7B shows a vibration waveform for each resonance frequency corresponding to the secondary resonance frequency f2, and FIG. It is a figure which shows the vibration waveform according to the resonant frequency corresponding to the resonant frequency f3.
That is, by step S24, vibration waveforms separated for each resonance frequency shown in FIGS. 7A, 7B, and 7C are obtained.

Next, the processing means recalculates the values of the primary, secondary, and tertiary resonance frequencies f1, f2, and f3 based on the three resonance frequency-specific vibration waveforms generated in step S24 (step S26: resonance frequency). Calculation step).
More specifically, when the wave number of the vibration waveform for each resonance frequency is N and the generation time of this wave number N is T, the value of the resonance frequency is newly calculated as N / T.
Thereby, although the numerical value of each resonance frequency can be obtained correctly, if it is not necessary to obtain the numerical value of the resonance frequency so accurately, step S26 may be omitted.

Next, the processing means obtains an attenuation rate D based on the vibration peak level of the vibration waveform by resonance frequency corresponding to each of the three vibration waveforms by resonance frequency, and generates a loss coefficient η from the attenuation rate D. Then, the loss coefficient η is output through the output means (step S28: loss coefficient output step).
More specifically, the square of the peak level of the vibration of the resonance frequency vibration waveform is converted into a common logarithm and then multiplied by ten, whereby the peak level is linearly approximated, and the vibration attenuation rate D is obtained by the slope of the straight line. That is, when the peak level and Pk, the straight line is represented by 10logPk ^2.
Here, the attenuation rate D and the loss coefficient η are in a relationship represented by the equation (5).
η = D / (27.3 · f _X ) (5)
(F _X is each resonance frequency)
Here, the resonance frequency f _X as step S18 may be used each resonance frequency identified in (resonance frequency specifying step), using the value of the exact resonant frequency obtained by the step S26 as the resonant frequency f _X This is advantageous in obtaining the loss coefficient η more accurately.
FIG. 8A is a diagram showing the time change of the square of the peak level of the vibration corresponding to the primary resonance frequency f1 after being converted to a common logarithm and multiplied by 10 and FIG. 8B corresponds to the secondary resonance frequency f2. FIG. 10C shows a value obtained by converting the time change of the square of the vibration peak level to a common logarithm and then multiplying it by 10 times. FIG. 10C shows the time change of the square of the vibration peak level corresponding to the third resonance frequency f3. It is the figure shown by the value multiplied 10 times after converting into. In FIG. 8, the horizontal axis represents time (seconds), and the vertical axis represents acceleration (dB).
In FIG. 8A, FIG. 8B, and FIG. 8C, the slope of the portion approximated by a straight line indicates the vibration attenuation rate D.
In FIG. 8C, for the region where the time exceeds 1 second, since the error included in the obtained peak level data is large, the coordinates of the data are not shown.
In addition, it is arbitrary in what form the loss coefficient η is output and expressed by the output means.
Further, vibration data of the object 2 measured in step S10 and input to the computer 12 (FIG. 4), amplitude characteristic data (FIG. 5) obtained in step S16 (amplitude characteristic data generation step), step S20 (bandpass filter) The characteristics of the bandpass filter set in the setting step) (FIG. 6), the vibration waveforms by resonance frequency (FIGS. 7A, 7B, and 7C) obtained by step S24 (vibration waveform generation step by resonance frequency). )), Data obtained by converting the time change of the square of the peak level of the vibration corresponding to each of the resonance frequencies obtained in step S28 (loss factor output step) to a common logarithm and multiplying it by 10 (FIG. 8 ( When A), (B), and (C)) are intermediate data, a part or all of the intermediate data is output by the output means. For determining whether is arbitrary, the intermediate data outputted in any form of, are arbitrary or expressed.

According to the present embodiment, the frequency amplitude characteristic data for each resonance frequency is obtained from the vibration data indicating the vibration waveform of the freely vibrating object, and the loss coefficient η is calculated for each resonance frequency from the frequency amplitude characteristic data for each resonance frequency. Therefore, there is no need for a special vibration device or complicated work to specify the resonance frequency, and it is of course possible to reduce costs and improve work efficiency, and accurately evaluate the vibration damping performance of objects. This is advantageous.
In particular, when the object 2 is a composite member configured by laminating a plurality of layers of fibers having different orientation directions, or by knitting fibers having different orientation directions, a laminated structure of fibers. It is required to accurately evaluate how the braided structure of the fiber and the fiber affects the damping performance of the object 2. According to the present embodiment, since the loss factor for each resonance frequency of the object 2 can be obtained, it is possible to evaluate the influence of the fiber laminated structure and the fiber braided structure on the damping performance of the composite member. This is advantageous in accurately evaluating the composite member.
Further, when the object is a golf club shaft as in the present embodiment, by obtaining a loss coefficient η at each resonance frequency, when a golf ball is hit with a golf club, the user's hand is passed through the shaft. Therefore, it is advantageous in evaluating the performance of the shaft of the golf club.

In the present embodiment, the case where the object is a shaft of a golf club has been described. However, the method of the present invention can be applied to vibrations of objects having various shapes such as a strip shape, a plate shape, or a solid rod shape. It can be widely applied to evaluate the attenuation performance.
In addition, the method of the present invention can be applied to an object generally referred to as a rigid. In particular, an object having a relatively small loss factor η, for example, an object having a loss factor η of 0.02 or less accurately evaluates vibration damping performance. This is advantageous.

It is explanatory drawing which shows the structure of the evaluation system for performing this invention method. It is a block diagram which shows the structure of the computer 12 used in order to perform the method of this invention. It is a flowchart which shows the vibration damping performance evaluation method of the object of this Embodiment. It is a wave form diagram which shows the vibration data measured from the object 2 which vibrates freely. It is a figure which shows the amplitude characteristic data produced | generated by the amplitude characteristic data production | generation step. It is explanatory drawing of a band pass filter. (A) is a figure which shows the vibration waveform classified by resonance frequency corresponding to the primary resonance frequency f1, (B) is a figure which shows the vibration waveform classified by resonance frequency corresponding to the secondary resonance frequency f2, (C) is a tertiary resonance frequency. It is a figure which shows the vibration waveform according to the resonant frequency corresponding to f3. (A) is a diagram showing the time change of the square of the peak level of the vibration corresponding to the primary resonance frequency f1 as a value multiplied by 10 after being converted to a common logarithm, and (B) is the vibration corresponding to the secondary resonance frequency f2. Fig. 10C shows the time change of the square of the peak level of the first time after conversion to the common logarithm, and Fig. 10C shows the time change of the square of the peak level of the vibration corresponding to the third resonance frequency f3 to the common logarithm. It is the figure shown by the value multiplied 10 times after doing.

Explanation of symbols

  2 ... Object, 12 ... Computer, D ... Decay rate, η ... Loss factor.

Claims (6)

An evaluation method for evaluating the vibration damping performance of the object using a computer based on the vibration waveform of the freely vibrating object,
The computer includes input means for inputting data, processing means for processing data input by the input means, and output means for outputting data supplied from the processing means,
The processing means is
Amplitude characteristic data indicating a vibration amplitude level with respect to a vibration frequency and a phase characteristic indicating a vibration phase with respect to the vibration frequency by performing fast Fourier transform on vibration data indicating the vibration waveform input via the input means. A Fourier transform data generation step for generating data respectively;
A resonance frequency specifying step of specifying a plurality of resonance frequencies including a primary resonance frequency of the object and a resonance frequency of the second or higher order based on the amplitude characteristic data;
A bandpass filter setting step for setting a bandpass filter having the resonance frequency as a center frequency corresponding to each of the plurality of resonance frequencies;
Resonance frequency-specific amplitude characteristic data generation step of generating amplitude characteristic data by resonance frequency corresponding to each of the plurality of resonance frequencies from each band-pass filter by inputting the amplitude characteristic data to each of the plurality of band-pass filters. When,
Resonance for each resonance frequency that generates a vibration waveform for each resonance frequency corresponding to each of the plurality of resonance frequencies by performing an inverse fast Fourier transform based on each of the plurality of amplitude characteristic data for each resonance frequency and the phase characteristic data. A waveform generation step;
Corresponding to each of the plurality of vibration waveforms by resonance frequency, a loss factor η is generated from the attenuation factor D generated based on the peak level of vibration of the resonance frequency vibration waveform, and the loss factor η is output to the output means. look including a loss factor output step of outputting through,
The generation of the attenuation factor D in the loss factor output step is performed by converting the square of the peak level of the vibration of the resonance frequency vibration waveform into a common logarithm and multiplying it by 10 to obtain a linear approximation and obtaining the slope of the straight line. The
A method for evaluating vibration damping performance of an object. In the bandpass filter setting step, the processing means sets a lower limit cutoff frequency and an upper limit cutoff frequency of the bandpass filter,
When the center frequency is fC, the lower cutoff frequency is fL, and the upper cutoff frequency is fH,
fL = fC · 2 ^(−1/6)
fH = fC · 2 ^(1/6) ,
The method for evaluating vibration damping performance of an object according to claim 1. In the bandpass filter setting step, the processing means sets a lower limit cutoff frequency and an upper limit cutoff frequency of the bandpass filter,
When the center frequency is fC, the lower cutoff frequency is fL, and the upper cutoff frequency is fH,
fH = (2) ^1/3 · fL
fC = (fL · fH) ^1/2 .
The method for evaluating vibration damping performance of an object according to claim 1. When the resonance frequency specified in the resonance frequency specifying step is fX,
The loss factor η by the loss factor output step is calculated by η = D / (27.3 · fX).
The method for evaluating vibration damping performance of an object according to claim 1. For each of the plurality of vibration waveforms by resonance frequency generated by the resonance frequency by vibration waveform generation step, when the wave number of the vibration waveform by resonance frequency is N and the generation time of the wave number N is T, A resonance frequency calculating step of calculating each of the plurality of resonance frequencies as N / T,
The loss factor η by the loss factor output step is calculated by η = D / (27.3 · fX),
The resonance frequency obtained by the resonance frequency calculation step is used as the fx.
The method for evaluating vibration damping performance of an object according to claim 1. The object has an elongated cylindrical shape or a strip shape,
In the free vibration of the object, the object is elastically deformed by applying a force in a direction perpendicular to the longitudinal direction to the other end of the object in the longitudinal direction with one end in the longitudinal direction of the object being fixed. And then the force is instantaneously removed,
The method for evaluating vibration damping performance of an object according to claim 1.

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