JPH06102106A - Vibration stress distribution measuring device - Google Patents

Abstract

(57) [Abstract] [Purpose] An object of the present invention is to provide a vibration stress distribution measuring device capable of obtaining vibration stress distribution data with high accuracy for a test piece vibrating in a wide frequency range. [Structure] Strain gauges are attached to the entire surface of the specimen. Further, the test piece is vibrated by the vibrating section at frequencies from the low frequency region to the high frequency region. Further, the strain output value of the strain gauge is input to the data storage unit of the CPU via the dynamic strain gauge and a channel selector capable of channel switching control of the dynamic strain gauge. Further, a displacement meter for reading the response signal of the test piece is arranged on the side of the test piece. In addition, this device applies a sine wave of a predetermined frequency to the sample, and detects the amount of change of the sine wave from the distortion output value and the response signal, and the distortion output value by the single sine wave correlation A frequency response analysis device is provided that obtains averaged amplitude and phase by removing harmonic components, subharmonic components, and random noise by waveform analysis of the response signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration stress distribution measuring device capable of highly accurately analyzing vibration stress distribution data for moving and stationary blades of a jet engine.

[0002]

2. Description of the Related Art In the jet engine shown in FIG.
For the moving and stationary blades arranged at the arrows A, B, C and D,
It is extremely important to measure the vibration stress distribution data with high accuracy and analyze the vibration characteristics in order to easily verify the FEM (finite element method) model and to establish the durability of the jet engine. .

[0003]

By the way, as a conventional method of measuring the vibration stress data of the moving and stationary blades, a plurality of strain gauges are attached to predetermined positions of the moving and stationary blade model, and the moving and stationary blade model at a predetermined frequency. Is known, and a method of analyzing the vibration stress data by obtaining the strain output value from each strain gauge at the resonance point is known. However, the resonance frequency component of the strain output value obtained from the strain gauge contains power supply noise, spike noise, and higher harmonic components, which cannot be removed by the conventional technology. Accurate vibration stress measurement could not be performed. Further, in the conventional measuring method, since only the amplitude component is measured, it is difficult to obtain the strain distribution of positive and negative signs, and the vibration stress distribution data cannot be analyzed. The present invention has been made in view of the above problems, and provides a vibration stress distribution measuring device capable of obtaining vibration stress distribution data with high accuracy for a sample vibrating in a wide frequency range. It is in.

[0004]

The vibration stress distribution measuring apparatus of the present invention applies a large number of strain gauges attached to the entire surface of the specimen and a specimen in a wide range of frequencies from a low frequency region to a high frequency region. A vibrating section to vibrate, a dynamic strain gauge that has a plurality of channels and that obtains a strain output value from a predetermined strain gauge by switching the channels, and is arranged on the side of the specimen to read the response signal of the specimen. C which stores vibration stress data from the displacement gauge, strain output value and response signal and stores it in the data storage unit
It is arranged between the PU and the data transfer between the dynamic strain gauge and the CPU,
A channel selector that switches the channels of the dynamic strainmeter and a sine wave with a predetermined resonance frequency are applied to the sample, and the change amount of the sine wave is detected from the strain output value and the response signal, and a single sine wave correlation A device comprising a frequency response analyzer that obtains averaged amplitude and phase by removing harmonic components, subharmonic components, and random noise by waveform analysis of the distortion output value and response signal by the method. is there.

[0005]

According to the vibration stress distribution measuring apparatus of the present invention, a predetermined frequency is transmitted from the frequency response analyzing apparatus to the vibrating section. Then, the resonance point of the sample being excited is detected by the fine adjustment of the phase.

Here, a sine wave having a predetermined resonance frequency is applied to the sample, and the change amount of the applied sine wave (resonance frequency component) is determined by a predetermined strain gauge selected by the channel selector. From the displacement meter and the response signal from the displacement meter, and the strain output value and the response signal are input again to the frequency response analyzer.

Since the frequency response analysis apparatus employs the single sine wave correlation method as a calculation method for analyzing the waveforms of the distortion output value and the response signal, the waveform of N times integration by the single sine wave correlation method. By the analysis, harmonic components, subharmonic components, and further random noise are removed from the distortion output value and the waveform of the response signal, and the averaged amplitude and phase are calculated. Here, since the phase information is obtained, the distortion output value is a numerical value with a plus / minus sign. Then, the obtained strain output value and response signal are accumulated as vibration stress data in the data section of the CPU.

The above-described operation is performed in other strain gauges by switching the channel selector, and the strain output value obtained from each strain gauge and the response signal from the displacement gauge are input to the frequency response analyzer at any time. As a result, the vibration stress distribution with positive and negative signs is obtained in the data storage unit of the CPU.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the vibration stress distribution measuring apparatus of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows an outline of the measuring apparatus of this embodiment. In the figure, reference numeral 1 is a fixing jig which is installed on the pedestal 3 in a state where the moving blade (sample) 2 whose vibration stress distribution is measured is oriented in the horizontal direction and the blade base end is fixed. In this embodiment, the one end fixing method is adopted as the method for fixing the moving blade 2, but there is also a both end fixing method for fixing the blade tip and the blade root portion of the moving blade 2. The moving blade 2 fixed to the fixing jig 1 is vibrated by the vibrating section 4. The vibrating section 4 causes the rotor blade 2 to have a low frequency range (5 KH).
It is composed of an electrodynamic exciter 4a which gives a vibration of Z or less) and a piezoelectric exciter 4b which gives a vibration of a high frequency range (5 to 15 KHZ or less).

Further, on the blade surfaces of the rotor blade 2 (both sides of the back 2a and the belly 2b), a large number of blades (back 2a
About 150 strain gauges (not shown) are attached to the blade surface on the side. A strain output value is obtained from each strain gauge and sent to the dynamic strain gauge 6.

The dynamic strain gauge 6 has a plurality of channels (about 30 channels) 6a, 6b, 6c, and a strain output value can be obtained from a predetermined strain gauge by switching the channels. A channel selector 7 for automatically switching channels is connected to the dynamic strain meter 6, and when a channel instruction signal is transmitted from the CPU 8 to the channel sector 7, the strain obtained by a predetermined strain gauge is obtained. The output value is input to the frequency response analysis device 5 described later.

A displacement gauge 9 for obtaining a response signal from the rotor blade 2 in a vibrating state is arranged beside the rotor blade 2, and the response signal is inputted to the frequency response analyzer 5. It has become. As a specific device of the displacement gauge 9, an optical electronic displacement gauge is used when a vibration in a low frequency range (5 KHZ or less) is applied to the moving blade 2 by the electrodynamic exciter 4a. , The tip amplitude and phase are obtained as response signals.
In addition, a high frequency range (5
If the vibration of (~ 15KHZ or less) is given,
A laser Doppler vibrometer is used to obtain velocity and phase as response signals. The CPU 8 is provided with a control section 8a, a data storage section 8b, a data output section 8c and the like.

Here, as described above, the strain response value is input to the frequency response analyzer 5 from a predetermined strain gauge,
A response signal is input from the displacement meter 9, but a predetermined frequency (resonance frequency) is given to the rotor blade 2 from the frequency response analyzer 5.
Is applied, and the amount of change in the sine wave is input to the frequency response analysis device 5 via the strain gauge and the displacement gauge 9.

Then, the frequency response analyzing apparatus 5 of the present embodiment.
Adopts the single sine wave correlation method as a calculation method for analyzing the waveforms of the distortion output value and the response signal. Furthermore, random noise is removed, and averaged amplitude and phase are calculated. That is, the basic theory of operation of the single sine wave correlation method will be described with reference to FIG. 2. y (t): output from the system under measurement x (t): SINω ₁ t ω ₁ : 2π × measurement frequency Then,

[Equation 1] However, N is the number of integrations, T = 2π / ω ₁ Here, the integration value is doubled because SI
When Nω ₁ t is multiplied and averaged over the integration time after integration,
for a _1/2 is calculated, 2 so we can determine in advance a ₁
It is doubled. When τ = NT-t and variable transformation are performed, dτ = -dt is taken into consideration, and

[Equation 2] Considering

[Equation 3] Becomes Now

[Equation 4] If you think that

[Equation 5] And becomes the form of convolution integral. That is, h (τ) represents an impulse response, and its characteristic in the frequency domain is given by the following Fourier transform.

[Equation 6] When this integration is performed, H ₁ (ω) is given by the following equation.

[Equation 7] Obtaining the gain characteristics of this filter,

[Equation 8] Becomes Similarly, the filter characteristic | H ₂ (ω) | when multiplied by COSω ₁ t and integrated is given by the following equation.

[Equation 9] These gain characteristics | H ₁ (ω) | and | H ₂ (ω) |
The fact that 1 (0 dB) at / ω ₁ = 1 (fundamental wave) can be proved as follows.

[Equation 10] Similarly, | H ₂ (ω) | = ± 1 Therefore, it can be understood that a filter characteristic (gain) is obtained by always taking an absolute value after integration. here,

[Equation 11] Therefore, the high frequency component theoretically becomes 0 regardless of N (the number of integrations) (to be precise, the Fourier coefficient of the harmonic component is 0).
Becomes ). In the case of subharmonics,

[Equation 12] However, N = Rn (R is an integer)

As described above, it can be understood that the harmonic component, the subharmonic component, and the random noise are removed from the frequency component by the waveform analysis of N times integration by the single sine wave correlation method.

Then, the frequency response analyzing apparatus 5 of the present embodiment.
3, the distortion output value y ₁ (t) and the response signal y ₂ (t) in which harmonics, subharmonics, and random noise are mixed are expressed by Expressions 11 and 12. H ₁ (ω), H ₂
The value that has passed through the filter (ω) is the component of y ₁ (t) and y ₂ (t) synchronized with the applied predetermined frequency (resonance frequency) x (t) = SIN ω ₁ t.

[Equation 13] Becomes Therefore, the averaged amplitude r = r ₂ / r
₁ and the phase θ = θ ₂ −θ ₁ are calculated (see FIGS. 4 and 5).

As described above, in the frequency response analysis apparatus 5 of this embodiment, the strain output value obtained from the strain gauge or the displacement gauge 9 is obtained by the waveform analysis of N times integration by the single sine wave correlation method. Waveform analysis is performed by removing harmonics, subharmonics, and random noise components from the resonance frequency component of the displacement output value, and the averaged amplitude and phase are measured.

The procedure for measuring the vibration stress using the apparatus of this embodiment is carried out as shown in FIG. That is,
After changing the frequency transmitted from the frequency response analyzer 5 from a low frequency to a high frequency to detect a resonance point, the rotor blade 2 is resonated at a predetermined frequency (step SP1). Then, at a predetermined resonance frequency, a channel instruction signal is transmitted from the control unit 8a of the CPU 8 to the channel sector 7, whereby a strain output value is output from the predetermined strain gauge to the frequency response analysis device 5 via the dynamic strain gauge 6. Is entered. Further, a response signal is input from the displacement meter 9 to the frequency response analysis device 5. Then, by the waveform analysis of N times integration by the single sine wave correlation method of the frequency response analysis device 5, the harmonic component, the subharmonic component, from the waveform of the distortion output value and the response signal,
Furthermore, random noise is removed, and averaged amplitude and phase are calculated (step SP2). Then, the strain output value and the response signal obtained from the predetermined strain gauge and the displacement gauge 9 are accumulated as vibration stress data in the data storage unit 8b of the CPU 8 (step SP3). Further, in order to obtain a highly accurate vibration stress distribution, vibration stress measurement is performed separately in a low frequency region using the electrodynamic vibrator 4a and a high frequency region using the piezoelectric vibrator 4b ( The flow in the direction of arrow Q shown in FIG. 6 is repeated). Then, by the above measurement procedure, vibration stress distribution data as shown in FIG. 7 is obtained. This vibration stress distribution data is obtained by vibrating the rotor blade 2 in the secondary bending mode and setting the vibration frequency to 2011HZ for measurement.
The relative strain (S / Smax; S is the amplitude value, Smax is the maximum value of the amplitude represented by the absolute value) is shown, and the horizontal axis shows the position from the blade root side with respect to the total length of the blade as a percentage. As a result, the trailing edge (Tr of the CVX) of the moving blade 2 (Tr
ailing Edge: T / E), leading edge (Leadi)
ng Edge: L / E), the stress distribution from the blade tip to the blade root, and the stress distribution from the blade tip to the blade root at the ventral side (CCV) T / E and L / E.

Therefore, according to the vibration stress distribution measuring apparatus of this embodiment, the frequency response analyzing apparatus 5 analyzes the strain output value inputted from the strain gauge and the waveform of the response signal inputted from the displacement meter 9. Since the single sine wave correlation method is adopted as the calculation method, the waveform of N times integration by this single sine wave correlation method is used to calculate the harmonic component, the subharmonic component, from the waveform of the distortion output value and the response signal, Furthermore, random noise can be removed, and averaged amplitude and phase can be calculated.

Since the phase information is obtained, the strain output value becomes a numerical value with a plus / minus sign, and can be accumulated as vibration stress data in the data storage section 8b of the CPU 8.

Further, the strain output values obtained from the strain gauges attached to the blade surface of the rotor blade 2 are used as the channel selector 7
Since it is possible to input data to the frequency response analysis device 5 at any time by switching operation, the vibration stress data distribution can be automatically obtained.

Further, the vibrating section 4 is an electric type vibration exciter 4a.
Since it is composed of the piezo-type vibrator 4b, it becomes possible to perform vibration stress measurement in a wide range of frequencies from a low frequency region to a high frequency region, and highly accurate vibration stress distribution data can be obtained. In this embodiment, the measuring device and the measuring procedure for the moving blade 2 are shown, but the same can be applied to the stationary blade.

[0024]

Since the vibration stress distribution measuring apparatus of the present invention is configured as described above, the strain output value obtained from the strain gauge and the harmonic component from the waveform of the response signal obtained from the displacement gauge can be divided into Harmonic components and random noise are removed, and the averaged amplitude and phase can be calculated, and the distortion output value also obtains phase information. The vibration stress data distribution can be obtained.

In addition, since the strain output value information from a large number of strain gauges attached to the test piece can be input from the dynamic strain gauge at any time by the channel switching control by the channel selector, The vibration stress data distribution can be obtained.

Further, it becomes possible to measure the vibration stress in a wide range of frequencies from the low frequency region to the high frequency region, and it is possible to obtain the vibration stress distribution data of the specimen with high accuracy.

[Brief description of drawings]

FIG. 1 is a schematic view showing a vibration stress distribution measuring device of the present invention.

FIG. 2 is a diagram showing the basics of a calculation method for waveform analysis of the frequency response analysis apparatus provided in the present invention.

FIG. 3 is a diagram showing a calculation method for waveform analysis of a distortion output value and a response signal by a frequency response analysis device.

FIG. 4 is a diagram showing waveforms of a distortion output value and a response signal.

FIG. 5 is a diagram showing waveforms of averaged distortion output values and response signals.

FIG. 6 is a diagram showing a measurement procedure using the vibration stress distribution measuring device of the present invention.

FIG. 7 is a diagram showing vibration stress distribution measurement data using the vibration stress distribution measuring device of the present invention.

FIG. 8 is a diagram showing moving and stationary blades of various parts of the jet engine.

[Explanation of symbols]

 1 Fixing jig 2 Moving blade (Static blade: Specimen) 3 Stand 4 Exciter 4a Electric exciter 4b Piezo exciter 5 Frequency response analyzer 6 Dynamic strain gauge 7 Channel selector 8 CPU 8a Control 8b Data storage unit 8c Output unit 9 Displacement meter

Claims (1)

[Claims] 1. A large number of strain gauges attached to the entire surface of the specimen, a vibrating section for exciting the specimen at a wide range of frequencies from a low frequency region to a high frequency region, and a plurality of channels. , A dynamic strain gauge that obtains a strain output value from a predetermined strain gauge by switching channels, a displacement gauge that is arranged on the side of the specimen and reads the response signal of the specimen, and a vibration from the strain output value and the response signal. A CPU that obtains stress data and stores it in a data storage unit, a channel selector that is provided between the dynamic strain gauge and the CPU to exchange data, and that controls the channel switching of the dynamic strain gauge, and a predetermined resonance frequency for the sample. Apply the sine wave of
And the amount of change of the sine wave is detected from the distortion output value and the response signal, and the harmonic component, the subharmonic component, and the random component are further randomized by the waveform analysis of the distortion output value and the response signal by the single sine wave correlation method. A vibration stress distribution measuring device comprising: a frequency response analyzing device for removing noise to obtain an averaged amplitude and phase.