KR101650172B1 - Apparatus and method for measuring the velocity of longitudinal wave and transverse wave - Google Patents

Apparatus and method for measuring the velocity of longitudinal wave and transverse wave Download PDF

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KR101650172B1
KR101650172B1 KR1020150066817A KR20150066817A KR101650172B1 KR 101650172 B1 KR101650172 B1 KR 101650172B1 KR 1020150066817 A KR1020150066817 A KR 1020150066817A KR 20150066817 A KR20150066817 A KR 20150066817A KR 101650172 B1 KR101650172 B1 KR 101650172B1
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longitudinal
transverse
signal
wave signal
wave
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KR1020150066817A
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Korean (ko)
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장경영
송동기
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한양대학교 산학협력단
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
    • G01H7/00—Measuring reverberation time ; room acoustic measurements

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  • Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)

Abstract

An apparatus for measuring longitudinal and transverse waves is disclosed. The apparatus for measuring longitudinal and transverse waves according to an embodiment of the present invention includes a longitudinal wave transducer and a transverse wave transducer for receiving a longitudinal wave signal and a transverse wave signal reflected from an object to be inspected; A signal synthesizer for synthesizing the longitudinal signal and the transverse signal so as to generate a longitudinal / transverse overlap signal; A signal extracting unit for separating and extracting the longitudinal wave signal and the transverse wave signal from the longitudinal / transverse overlap signal; And a velocity calculator for calculating velocities of the longitudinal wave signal and the transverse wave signal using the periods of the extracted longitudinal and transverse wave signals and the thickness of the subject.

Description

[0001] APPARATUS AND METHOD FOR MEASURING THE VELOCITY OF LONGITUDINAL WAVE AND TRANSVERSE WAVE [0002]

One embodiment of the present invention relates to velocity measurement of longitudinal and transverse waves, and more particularly to an apparatus and method for longitudinal and transverse velocity measurements based on signal processing.

The technique of measuring the elastic properties of a subject through the measurement of the speed of a sound wave with a pulser / receiver is largely divided into a method using a plurality of pulsers / receivers and a method using a single pulser / receiver.

First, a scheme using a plurality of pulsers / receivers includes a longitudinal wave and a longitudinal wave pulser / receiver and a longitudinal wave transducer for receiving, a pulser / receiver having a shear wave and for receiving, The transverse wave transducer is constructed independently. At this time, the longitudinal wave is excited in the longitudinal wave pulser and received by the longitudinal wave transducer, the received longitudinal wave is signaled through the longitudinal wave receiver, the transverse wave is excited in the transverse wave pulser and received by the transverse wave transducer, To measure the velocity of longitudinal waves and transverse waves. That is, in the method of using plural pulsers / receivers, it is necessary to separately receive and receive signals and to perform signal processing separately.

Next, a single pulser / receiver is used for each of the longitudinal wave transducer and the transverse wave transducer. However, only one pulser / receiver is provided for connecting the pulser / receiver to the longitudinal probe when receiving or receiving the longitudinal wave, When doing so, it switches the pulser / receiver to a transverse probe and performs signal processing of longitudinal and transverse waves.

At this time, there is a problem in that the efficiency and efficiency of a system using a plurality of pulsers / receivers is low, and a method using a single pulser / receiver can simplify the system, but has a problem in that an error occurs in the switching process.

A related prior art is Korean Patent Laid-Open Publication No. 10-2013-0085953 entitled " Method of Measuring Modulus of Elasticity, Disclosure Date: 2014. 10. 24 ".

An object of an embodiment of the present invention is to provide an apparatus and a method for measuring longitudinal and transverse wave velocities that can measure velocities of longitudinal waves and transverse waves that have passed through a subject using an overlapping signal in which longitudinal waves and transverse waves are combined.

According to an aspect of the present invention, there is provided an apparatus for measuring longitudinal and transverse waves, including: longitudinal wave transducers and transverse wave transducers receiving longitudinal wave signals and transverse wave signals reflected from an object; A signal synthesizer for synthesizing the longitudinal signal and the transverse signal so as to generate a longitudinal / transverse overlap signal; A signal extracting unit for separating and extracting the longitudinal wave signal and the transverse wave signal from the longitudinal / transverse overlap signal; And a velocity calculator for calculating velocities of the longitudinal wave signal and the transverse wave signal using the periods of the extracted longitudinal and transverse wave signals and the thickness of the subject.

Preferably, the resonance frequencies of the longitudinal wave transducer and the transverse wave transducer are set differently, the longitudinal wave signal has a resonance frequency equal to the resonance frequency of the longitudinal wave transducer, and the transverse wave signal is equal to the resonance frequency of the transverse wave transducer The resonance frequency of the longitudinal wave signal and the resonance frequency of the transverse wave signal may have different values.

Preferably, the signal combining unit performs signal processing such that the longitudinal wave signal and the transverse wave signal have different resonance frequencies, and then generates the longitudinal / transverse wave superposition signal by combining the longitudinal wave signal and the transverse wave signal .

Preferably, the signal extractor selects an arbitrary frequency between a maximum frequency and a minimum frequency of the longitudinal / transverse overlap signal as a cutoff frequency, performs low-pass and high-pass filtering on the cutoff frequency, The longitudinal wave signal and the transverse wave signal can be separately extracted from the superimposed signal.

Preferably, the signal extractor performs a short time Fourier transform (STFT) on the longitudinal / transversal superposition signal to detect the resonance frequency and the period of each of the two reflection signals included in the longitudinal / transverse overlap signal, And sets a cut-off frequency for separating the longitudinal-wave signal and the transverse-wave signal based on the detected resonance frequency based on the cut-off frequency, Pass filtering may be performed to separate and extract the longitudinal and transverse signals from the longitudinal / transverse overlap signals.

Preferably, the apparatus for measuring longitudinal and transverse waves according to an embodiment of the present invention further includes an elastic property calculating unit that calculates elastic properties based on the velocity of the longitudinal wave signal and the transverse wave signal, Can be performed by the following equations (2) to (6).

&Quot; (2) "

Figure 112015046008356-pat00001

&Quot; (3) "

Figure 112015046008356-pat00002

&Quot; (4) "

Figure 112015046008356-pat00003

&Quot; (5) "

Figure 112015046008356-pat00004

&Quot; (6) "

Figure 112015046008356-pat00005

here,

Figure 112015046008356-pat00006
and
Figure 112015046008356-pat00007
S denotes the thickness of the object to be inspected,
Figure 112015046008356-pat00008
and
Figure 112015046008356-pat00009
The time required for the propagation of the longitudinal wave signal and the transverse wave signal in the object under test,
Figure 112015046008356-pat00010
E is the longitudinal elastic modulus, G is the lateral elastic modulus,
Figure 112015046008356-pat00011
Represents the density of the subject.

Preferably, the elastic properties may include at least one of Poisson's ratio, longitudinal elastic modulus and transverse elastic modulus.

According to another aspect of the present invention, there is provided a method of measuring longitudinal and transverse waves, comprising: receiving longitudinal and transverse signals reflected from an object; Generating a longitudinal / transverse overlap signal by synthesizing the longitudinal signal and the transverse signal so as to be separated; Separating and extracting the longitudinal wave signal and the transverse wave signal from the longitudinal / transverse wave superposition signal; And calculating the velocity of the longitudinal wave signal and the transverse wave signal using the period of each of the extracted longitudinal and transverse wave signals and the thickness of the subject.

Preferably, the longitudinal wave signal and the transverse wave signal are received through a longitudinal wave transducer and a transverse wave transducer whose resonance frequencies are set different from each other, and the longitudinal wave signal has a resonance frequency equal to the resonance frequency of the longitudinal wave transducer, The resonance frequency of the longitudinal wave signal and the resonance frequency of the transverse wave signal may have different values.

Preferably, the step of generating the longitudinal / transverse wave superimposing signal comprises: performing signal processing so that the longitudinal wave signal and the transverse wave signal have different resonance frequencies; and then synthesizing the longitudinal wave signal and the transverse wave signal, A superimposed signal can be generated.

Preferably, the step of separating and extracting the longitudinal and transverse signals comprises the steps of: selecting an arbitrary frequency between a maximum frequency and a minimum frequency of the longitudinal / transverse overlap signal as a cutoff frequency; And performing low-pass and high-pass filtering on the cut-off frequency to separately extract the longitudinal and transverse signals from the longitudinal / transverse overlap signal.

Preferably, the step of separating and extracting the longitudinal and transverse signals comprises performing a short time Fourier transform (STFT) on the longitudinal / transverse overlap signals to calculate a resonant frequency of each of the two reflected signals included in the longitudinal / Detecting a frequency and a period; Dividing the longitudinal signal and the transverse signal based on the detected period; Setting a cutoff frequency for separating the longitudinal and transverse signals based on the detected resonant frequency; And performing low-pass and high-pass filtering on the cut-off frequency to separately extract the longitudinal and transverse signals from the longitudinal / transverse overlap signal.

Preferably, the method for measuring longitudinal and transverse wave velocities according to an embodiment of the present invention further includes calculating elastic properties based on velocities of the longitudinal wave signal and the transverse wave signal, Can be performed by Equations (2) to (6).

 &Quot; (2) "

Figure 112015046008356-pat00012

&Quot; (3) "

Figure 112015046008356-pat00013

&Quot; (4) "

Figure 112015046008356-pat00014

&Quot; (5) "

Figure 112015046008356-pat00015

&Quot; (6) "

Figure 112015046008356-pat00016

here,

Figure 112015046008356-pat00017
and
Figure 112015046008356-pat00018
S denotes the thickness of the object to be inspected,
Figure 112015046008356-pat00019
and
Figure 112015046008356-pat00020
The time required for the propagation of the longitudinal wave signal and the transverse wave signal in the object under test,
Figure 112015046008356-pat00021
E is the longitudinal elastic modulus, G is the lateral elastic modulus,
Figure 112015046008356-pat00022
Represents the density of the subject.

Preferably, the elastic properties may include at least one of Poisson's ratio, longitudinal elastic modulus and transverse elastic modulus.

According to one embodiment of the present invention, by measuring the speed of a longitudinal wave signal and a transverse wave signal by using a single signal mixed with a longitudinal wave and a transverse wave, the structure can be simplified, errors can be reduced, accuracy is improved, stability and efficiency are improved There is an effect that can be made.

FIG. 1 is a block diagram illustrating a longitudinal and transverse velocity measuring apparatus according to an embodiment of the present invention. Referring to FIG.
2 is a diagram for explaining a signal extracting unit according to an embodiment of the present invention.
FIG. 3 is a diagram illustrating a result of performing low-pass and high-pass filtering on a longitudinal / transverse overlap signal according to an embodiment of the present invention.
4 is a diagram illustrating a result of performing a short time Fourier transform on a longitudinal / transverse overlap signal according to an embodiment of the present invention.
FIG. 5 is a flowchart illustrating a method of measuring longitudinal and transverse wave velocities according to an embodiment of the present invention. Referring to FIG.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It is to be understood, however, that the invention is not to be limited to the specific embodiments, but includes all changes, equivalents, and alternatives falling within the spirit and scope of the invention. Like reference numerals are used for like elements in describing each drawing.

The terms first, second, A, B, etc. may be used to describe various elements, but the elements should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component. And / or < / RTI > includes any combination of a plurality of related listed items or any of a plurality of related listed items.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly indicates otherwise. In the present application, the terms "comprises" or "having" and the like are used to specify that there is a feature, a number, a step, an operation, an element, a component or a combination thereof described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram illustrating a longitudinal and transverse velocity measuring apparatus according to an embodiment of the present invention. Referring to FIG.

1, the longitudinal and transverse velocity measuring apparatus 100 includes a longitudinal wave transducer 112, a transverse wave transducer 114, a signal synthesizing unit 120, a signal extracting unit 130 And a speed calculating unit 140. [

Each of the longitudinal wave transducer 112 and the transverse wave transducer 114 receives the longitudinal wave signal and the transverse wave signal which are incident on one surface of the object to be inspected and pass therethrough and reflected from the other surface.

At this time, each of the longitudinal wave transducer 112 and the transverse wave transducer 114 is a unit for transmitting or receiving a longitudinal wave signal and a transverse wave signal, and converts the longitudinal wave signal and the transverse wave signal into an electric signal, Can be converted. Thus, each of the longitudinal wave transducer 112 and the transverse wave transducer 114 receives the longitudinal wave signal and the transverse wave signal, and converts the received longitudinal wave signal and the transverse wave signal into an electric signal corresponding to the longitudinal wave signal and the transverse wave signal.

The longitudinal and transverse signals received by the longitudinal and longitudinal transducers 112 and 114 have resonance frequency characteristics when the longitudinal and transverse transducers 112 and 114 are set to a specific resonance frequency in advance. The resonance frequency of the longitudinal wave probe 112 and the resonance frequency of the transverse wave probe 114 may be set differently according to an embodiment of the present invention. Accordingly, the longitudinal wave signal has the same resonance frequency as the resonance frequency of the longitudinal wave probe, and the transverse wave signal has the resonance frequency equal to the resonance frequency of the transverse wave probe. As a result, the resonance frequency of the longitudinal wave signal and the resonance frequency of the transverse wave signal are different .

However, in another embodiment, the resonance frequencies of the longitudinal wave transducer 112 and the transverse wave transducer 114 may be set to be the same.

The apparatus 100 for measuring longitudinal and transverse waves according to an embodiment of the present invention uses a longitudinal wave signal converted into an electric signal by the longitudinal wave transducer 112 and a transverse wave signal converted into an electric signal by the transverse wave transducer 114 In order to simplify the explanation, the longitudinal and transverse signals before being converted into electric signals are divided into longitudinal and transverse signals, which are converted into electric signals, but longitudinal signals and longitudinal signals are not distinguished from each other. Called transverse wave signal.

The signal combiner 120 combines the longitudinal and transverse signals to generate a longitudinal / transverse overlap signal.

More specifically, the signal combining unit 120 is a unit corresponding to a conventional receiver, and has a function of receiving a longitudinal wave signal from the longitudinal wave transducer 112 and receiving a transverse wave signal from the transverse wave transducer 114 in the same manner as a conventional receiver However, unlike a conventional receiver, a longitudinal wave / transverse wave superposition signal is generated by synthesizing the longitudinal wave signal and the transverse wave signal so as to be distinguished from each other. The longitudinal and transverse signals received by the signal synthesizer 120 from the longitudinal transducer 112 and the transverse transducer 114 are longitudinal and transverse signals converted into electrical signals.

If the resonance frequencies of the longitudinal wave transducer 112 and the transverse wave transducer 114 are different from each other, the signal synthesizing unit 120 merely synthesizes the longitudinal wave signal and the transverse wave signal received from the longitudinal wave transducer 112 and the transverse wave transducer 114, respectively To generate a longitudinal / transverse overlap signal. At this time, since the resonance frequency of the longitudinal wave signal is different from that of the transverse wave signal, the longitudinal wave signal and the transverse wave signal can be distinguished from each other in the longitudinal / transverse wave superposition signal.

However, when the resonance frequencies of the longitudinal wave transducer 112 and the transverse wave transducer 114 are the same, the signal synthesizing unit 120 outputs the longitudinal wave signals received from the longitudinal wave transducer 112 and the transverse wave signals received from the transverse wave transducer 114, The longitudinal and transverse wave superposition signals can be generated by making the longitudinal and transverse wave signals have different frequency characteristics by performing signal processing on the longitudinal and transverse wave signals.

The reason why the longitudinal / transverse overlap signal is generated by using the longitudinal and transverse signals set to have different frequency characteristics in the present invention is that if the longitudinal and transverse signals are used to measure the velocities of the longitudinal and transverse signals, It is possible to measure the speeds of longitudinal and transverse signals without switching connection of the signal synthesizer 120 with the longitudinal transducer 112 or the transverse probe 114 while providing only one signal synthesizer 120 corresponding to the receiver Because.

That is, in a conventional single pulser / receiver scheme, the receiver is alternately switched and connected to one of a longitudinal probe and a transverse probe because if the receiver is simultaneously connected to a longitudinal probe and a transverse probe, the longitudinal and transverse signals In the present invention, the signal combining unit 120 corresponding to the conventional receiver is connected to the longitudinal wave transducer 112 and the transverse wave transducer 114 at the same time, However, since the longitudinal / transverse overlap signal is generated so that the longitudinal wave signal and the transverse wave signal are distinguished from each other, there is no need to selectively connect the signal synthesizer 120 to the longitudinal probe 112 or the transverse probe 114 for connection.

As a result, according to the present invention, since only one signal synthesizer 120 corresponding to a conventional receiver is provided, there is an advantage that the apparatus is simpler than a conventional system using a plurality of pulsers / receivers, There is no need to perform a switching operation in comparison with a method of using a receiver, so that the possibility of errors is lowered and the stability of the apparatus is improved.

The signal extracting unit 130 separates and extracts the longitudinal wave signal and the transverse wave signal from the longitudinal / transverse overlap signal.

At this time, the signal extracting unit 130 selects an arbitrary frequency between the maximum frequency and the minimum frequency of the longitudinal / transverse superposition signal as the cutoff frequency, performs low-pass and high-pass filtering on the cutoff frequency, The longitudinal wave signal and the transverse wave signal can be separated and extracted. A detailed description thereof will be given later with reference to FIG. 2 and FIG.

However, in order to separately extract the longitudinal and transverse signals from the longitudinal / transverse overlap signals by performing low-pass and high-pass filtering, the resonance frequencies of the longitudinal and transverse signals included in the longitudinal / transverse overlap signal should be known.

If the resonance frequencies of the longitudinal and transverse signals included in the longitudinal / transverse overlap signal are not known, the longitudinal and transverse signal can be separated and extracted from the longitudinal / transverse overlap signal by applying frequency conversion to the longitudinal / have. A detailed description thereof will be given later with reference to Fig.

The velocity calculator 140 calculates the velocities of the longitudinal wave signal and the transverse wave signal using the period of each of the longitudinal and transverse signals separated and extracted through the signal extractor 130 and the thickness of the subject.

More specifically, the value obtained by doubling the thickness of the test subject is the reciprocating wave distance of each of the longitudinal wave signal and the transverse wave signal. The period of each of the longitudinal wave signal and the transverse wave signal is set to be longer than the time required for the longitudinal wave signal and the transverse wave signal to propagate The velocity of the longitudinal wave signal can be calculated by dividing the value obtained by doubling the thickness of the object to be measured (longitudinal wave signal propagation distance) by the reciprocating propagation time of the longitudinal wave signal, and the value obtained by doubling the thickness of the subject body The propagation distance of the transverse waves) is divided by the round trip wave propagation time of the transverse wave signal, the velocity of the transverse wave signal can be calculated.

However, the present invention is not limited to this, and various algorithms that can more accurately calculate the speeds of the longitudinal wave signal and the transverse wave signal using the longitudinal wave signal and the transverse wave signal can be applied.

2 is a diagram for explaining a signal extracting unit according to an embodiment of the present invention.

Referring to FIG. 2, the signal extracting unit 130 may include a low pass filter 132 and a high pass filter 134 according to an embodiment of the present invention.

2 (a) shows a longitudinal-wave resonance frequency characteristic

Figure 112015046008356-pat00023
, Below
Figure 112015046008356-pat00024
) Is a transverse wave resonance frequency characteristic of a transverse wave signal (
Figure 112015046008356-pat00025
, Below
Figure 112015046008356-pat00026
Quot;), the longitudinal / transverse overlap signal is separated.

Cutoff frequency (

Figure 112015046008356-pat00027
, Below
Figure 112015046008356-pat00028
Quot;) may be a reference frequency that distinguishes between a low frequency band and a high frequency band to be filtered. The cut-off frequency can be calculated by the following equation (1).

[Equation 1]

Figure 112015046008356-pat00029

In Fig. 2 (a), the cutoff frequency

Figure 112015046008356-pat00030
A signal corresponding to a larger frequency, that is, a longitudinal wave signal can be extracted by the high-pass filter 134,
Figure 112015046008356-pat00031
A signal corresponding to a smaller frequency, that is, a transverse wave signal, can be extracted by the low-pass filter 132. [

Fig. 2 (b) is a cross-

Figure 112015046008356-pat00032
The longitudinal wave resonance frequency
Figure 112015046008356-pat00033
And separating the longitudinal / transversal superposition signal in a case where the longitudinal / transverse overlap signal is larger than the longitudinal / transverse overlap signal.

In the case of FIG. 2 (b), as in the case of FIG. 2 (a), the cutoff frequency can be calculated by Equation (1)

Figure 112015046008356-pat00034
The transverse wave signal having a larger frequency characteristic can be extracted by the high pass filter 134,
Figure 112015046008356-pat00035
A longitudinal wave signal having a smaller frequency characteristic can be extracted by the low-pass filter 132. [

Here, Equation (1)

Figure 112015046008356-pat00036
and
Figure 112015046008356-pat00037
Lt; RTI ID = 0.0 >
Figure 112015046008356-pat00038
But the cutoff frequency
Figure 112015046008356-pat00039
Is not an average
Figure 112015046008356-pat00040
and
Figure 112015046008356-pat00041
Lt; RTI ID = 0.0 > a < / RTI >

FIG. 3 is a diagram illustrating a result of performing low-pass and high-pass filtering on a longitudinal / transverse overlap signal according to an embodiment of the present invention.

In FIG. 3, a signal extraction result of a longitudinal / transverse superposition signal having a frequency higher than that of the transverse signal is plotted as a horizontal axis, and a graph showing the magnitude of the signal with respect to time with respect to the vertical axis.

3 (b) shows the longitudinal wave signal, FIG. 3 (a) shows the transverse wave signal, and FIG. 3 (b) shows the transverse wave signal. .

3 (a) shows a result of passing the longitudinal / transverse overlap signal through the low-pass filter 132. Since the low-pass filter 122 passes the transverse signal lower than the cut-off frequency, The period of the transverse wave signal can be roughly grasped. That is, in FIG. 3 (a), the peak value of the transverse wave signal appears at predetermined time intervals, and the time interval between the two peak values can be the period of the transverse wave signal.

In addition, the period of the longitudinal wave signal can be roughly grasped through FIG. 3 (b), and the period of the longitudinal wave signal can be roughly calculated using the time interval at which the peak value of the longitudinal wave signal occurs in FIG. 3 (b) .

4 is a diagram illustrating a result of performing a short time Fourier transform on a longitudinal / transverse overlap signal according to an embodiment of the present invention.

When a short time Fourier transform is performed on the longitudinal / transverse overlap signal, the period and the resonant frequency of each of the two reflection signals included in the longitudinal / transverse overlap signal can be numerically derived. In principle, the short time Fourier transform is used to perform spectral analysis on a signal, but in the present invention, it is used to detect the period and the resonance frequency of each of two reflection signals included in the longitudinal / transverse overlap signal.

4 (a) shows the longitudinal / transverse overlap signal using the magnitude of the signal over time. As a result of performing the short time Fourier transform on the longitudinal / transversal superposition signal, as shown in FIG. 4 (b) And the frequency magnitude along the time axis can be represented as the spectrum shown by the vertical axis. Referring to FIG. 4 (b), the spectrum of each of the two reflection signals included in the longitudinal / transverse overlap signal is shown, and the period of each of the two reflected signals can be known through the interval between the spectra. Also, the red dotted line passing through the spectrum for each of the two reflected signals represents the resonance frequency for each of the two reflected signals, which is obtained by performing a short-time Fourier transform on the longitudinal / transverse overlap signal and calculating the numerically obtained resonance frequency value As a red dotted line over the spectrum. Referring to FIG. 4 (b), the longitudinal / transverse wave superimposing signal is composed of an upper reflection signal having a resonance frequency of approximately 6.2 MHz and a period of approximately 12 μs, a resonance frequency of approximately 2.1 MHz, And a reflection signal.

At this time, since the longitudinal wave signal is faster than the transverse wave signal, it can be seen that the reflection signal at the upper end is a longitudinal wave signal and the reflection signal at the lower end is a transverse wave signal.

Next, the cutoff frequency may be set to 4.15 MHz ((6.2 MHz +2.1 MHz) / 2) based on the resonance frequency of the upper-stage longitudinal wave signal and the lower-stage transverse wave signal, The transverse signal can be separated and extracted, and the longitudinal signal can be separated and extracted through the high-pass filtering.

In summary, the signal extracting unit 130 performs a short time Fourier transform (STFT) on the longitudinal / transverse overlap signal to detect the resonance frequency and the period of each of the two reflected signals included in the longitudinal / transverse overlap signal, A cut-off frequency for separating the longitudinal and transverse signals based on the detected resonance frequency is set, and low-pass and high-pass filtering are performed based on the cut-off frequency, / Separate the longitudinal and transverse signals from the overlapping signals.

According to another embodiment of the present invention, the signal extracting unit 130 performs a short time Fourier transform (STFT) on the vertical / horizontal overlap signal to detect only the period of each of the two reflection signals included in the vertical / horizontal overlap signal , The velocity calculating unit 140 may calculate the velocity of the longitudinal wave signal and the transverse wave signal using the period of each of the detected two reflected signals and the thickness of the subject. According to another embodiment of the present invention, the elastic properties of the subject can be calculated using the velocities of the longitudinal and transverse signals. More specifically, the elastic properties of the object can be calculated using the equations (2) to (6).

At this time, the elastic properties may include at least one of Poisson's ratio, longitudinal elastic modulus and transverse elastic modulus.

 &Quot; (2) "

Figure 112015046008356-pat00042

&Quot; (3) "

Figure 112015046008356-pat00043

&Quot; (4) "

Figure 112015046008356-pat00044

&Quot; (5) "

Figure 112015046008356-pat00045

&Quot; (6) "

Figure 112015046008356-pat00046

here,

Figure 112015046008356-pat00047
and
Figure 112015046008356-pat00048
S denotes the thickness of the object to be inspected,
Figure 112015046008356-pat00049
and
Figure 112015046008356-pat00050
The time required for the propagation of the longitudinal wave signal and the transverse wave signal in the object under test,
Figure 112015046008356-pat00051
E is the longitudinal elastic modulus, G is the lateral elastic modulus,
Figure 112015046008356-pat00052
Represents the density of the object to be inspected. Preferably, the longitudinal and transverse velocity measuring apparatus 100 according to an embodiment of the present invention further includes an elastic property calculating unit (not shown) that calculates elastic properties based on velocities of longitudinal and transverse signals .

FIG. 5 is a flowchart illustrating a method of measuring longitudinal and transverse wave velocities according to an embodiment of the present invention. Referring to FIG.

In step 510, longitudinal and transverse velocity measuring apparatus 100 receives a longitudinal wave signal and a transverse wave signal reflected from the subject.

In another embodiment, since the longitudinal and transverse signals are received at longitudinal transducer 112 and transverse transducer 114, the resonant frequencies of the longitudinal and transverse signals may be different. For example, when the longitudinal wave signal and the transverse wave signal are initially excited so as to have different resonance frequencies, the resonance frequencies of the received longitudinal wave signal and the transverse wave signal may also be different.

In step 520, the longitudinal and transverse velocity measuring apparatus 100 synthesizes the longitudinal and transverse wave signals so as to divide the longitudinal and transverse wave signals, thereby generating longitudinal / transverse wave superposition signals.

If the resonance frequency differs from the time when the longitudinal and transverse signals are received for the first time, it is possible to generate the longitudinal / transverse superposition signals by simply synthesizing the received longitudinal and transverse signals without performing separate signal processing will be.

In step 530, longitudinal and transverse velocity measuring apparatus 100 separates and extracts longitudinal and transverse signals from longitudinal / transverse overlap signals.

In step 540, the longitudinal and transverse wave velocity measuring apparatus 100 calculates the velocity of the longitudinal wave signal and the transverse wave signal using the period of each extracted longitudinal wave signal and transverse wave signal, and the thickness of the inspected object.

In another embodiment, the longitudinal and transverse wave velocity measuring apparatus 100 can calculate the elastic properties of the subject by using the velocity of the longitudinal wave signal and the transverse wave signal.

The present invention has been described with reference to the preferred embodiments. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present invention is defined by the appended claims rather than by the foregoing description, and all differences within the scope of equivalents thereof should be construed as being included in the present invention.

Claims (14)

A longitudinal wave transducer and a transverse wave transducer for receiving a longitudinal wave signal and a transverse wave signal reflected from an object;
A signal synthesizer for synthesizing the longitudinal signal and the transverse signal so as to generate a longitudinal / transverse overlap signal;
A signal extracting unit for separating and extracting the longitudinal wave signal and the transverse wave signal from the longitudinal / transverse overlap signal; And
And a velocity calculating section for calculating velocities of the longitudinal wave signal and the transverse wave signal using the period of each of the extracted longitudinal and transverse wave signals and the thickness of the subject. The method according to claim 1,
The resonance frequencies of the longitudinal wave transducer and the transverse wave transducer are set differently,
Wherein the longitudinal wave signal has a resonance frequency equal to the resonance frequency of the longitudinal wave probe, the transverse wave signal has a resonance frequency equal to the resonance frequency of the transverse wave probe, and the resonance frequency of the longitudinal wave signal and the resonance frequency of the transverse wave signal have different values Of the longitudinal and transverse waves. The method according to claim 1,
The signal synthesizer
Wherein the longitudinal and transverse wave signals are generated by performing signal processing such that the longitudinal wave signal and the transverse wave signal have different resonance frequencies, and then synthesizing the longitudinal wave signal and the transverse wave signal to generate the longitudinal / transverse wave superposition signal. The method according to claim 1,
The signal extracting unit
Wherein the frequency of the longitudinal / transverse wave superposition signal is selected as a cutoff frequency and a low-frequency and high-pass filtering are performed on the basis of the cutoff frequency, An apparatus for measuring the speed of longitudinal and transverse waves for separating and extracting transverse signals. The method according to claim 1,
The signal extracting unit
Performing a short time Fourier transform (STFT) on the longitudinal / transversal superposition signal to detect a resonance frequency and a period of each of the two reflection signals included in the longitudinal / transverse overlap signal, and, based on the detected period, And the transverse wave signal, sets a cutoff frequency for separating the longitudinal and transverse signals based on the detected resonance frequency, performs low-pass and high-pass filtering on the cutoff frequency, And a longitudinal and transverse wave velocity measuring device for separating and extracting the longitudinal wave signal and the transverse wave signal from the transverse wave superposition signal. The method according to claim 1,
Further comprising an elastic property calculation unit for calculating an elastic property based on the velocity of the longitudinal wave signal and the transverse wave signal,
Wherein the calculation of the elastic properties is performed by the following equations (2) to (6).
&Quot; (2) "
Figure 112015046008356-pat00053

&Quot; (3) "
Figure 112015046008356-pat00054

&Quot; (4) "
Figure 112015046008356-pat00055

&Quot; (5) "
Figure 112015046008356-pat00056

&Quot; (6) "
Figure 112015046008356-pat00057

here,
Figure 112015046008356-pat00058
and
Figure 112015046008356-pat00059
S denotes the thickness of the object to be inspected,
Figure 112015046008356-pat00060
and
Figure 112015046008356-pat00061
The time required for the propagation of the longitudinal wave signal and the transverse wave signal in the object under test,
Figure 112015046008356-pat00062
E is the longitudinal elastic modulus, G is the lateral elastic modulus,
Figure 112015046008356-pat00063
Represents the density of the subject. The method according to claim 6,
The elastic properties
Poisson's ratio, longitudinal elastic modulus and lateral modulus of elasticity. Receiving a longitudinal wave signal and a transverse wave signal reflected from the subject;
Generating a longitudinal / transverse overlap signal by synthesizing the longitudinal signal and the transverse signal so as to be separated;
Separating and extracting the longitudinal wave signal and the transverse wave signal from the longitudinal / transverse wave superposition signal; And
And calculating the velocity of the longitudinal wave signal and the transverse wave signal using the period of each of the extracted longitudinal and transverse wave signals and the thickness of the subject. 9. The method of claim 8,
The longitudinal and transverse signals are received through a longitudinal wave transducer and a transverse wave transducer whose resonance frequencies are set different from each other,
Wherein the longitudinal wave signal has a resonance frequency equal to the resonance frequency of the longitudinal wave probe, the transverse wave signal has a resonance frequency equal to the resonance frequency of the transverse wave probe, and the resonance frequency of the longitudinal wave signal and the resonance frequency of the transverse wave signal have different values And measuring the velocity of the longitudinal and transverse waves. 9. The method of claim 8,
The step of generating the longitudinal / transverse overlap signal
Wherein the longitudinal and transverse wave signals are generated by performing signal processing such that the longitudinal wave signal and the transverse wave signal have different resonance frequencies, and then synthesizing the longitudinal wave signal and the transverse wave signal to generate the longitudinal / transverse wave superposition signal. 9. The method of claim 8,
The step of separating and extracting the longitudinal wave signal and the transverse wave signal
Selecting an arbitrary frequency between a maximum frequency and a minimum frequency of the longitudinal / transverse overlap signal as a cutoff frequency; And
And performing low-pass and high-pass filtering on the cutoff frequency to separate and extract the longitudinal and transverse signals from the longitudinal / transverse overlap signals. 9. The method of claim 8,
The step of separating and extracting the longitudinal wave signal and the transverse wave signal
Performing a short time Fourier transform (STFT) on the longitudinal / transversal superposition signal to detect a resonance frequency and a period of each of the two reflection signals included in the longitudinal / transverse overlap signal;
Dividing the longitudinal signal and the transverse signal based on the detected period;
Setting a cutoff frequency for separating the longitudinal and transverse signals based on the detected resonant frequency; And
And performing low-pass and high-pass filtering on the cutoff frequency to separate and extract the longitudinal and transverse signals from the longitudinal / transverse overlap signals. 9. The method of claim 8,
Further comprising the step of calculating an elastic property based on the velocity of the longitudinal wave signal and the transverse wave signal,
Wherein the calculation of the elastic properties is performed by the following equations (2) to (6).
&Quot; (2) "
Figure 112015046008356-pat00064

&Quot; (3) "
Figure 112015046008356-pat00065

&Quot; (4) "
Figure 112015046008356-pat00066

&Quot; (5) "
Figure 112015046008356-pat00067

&Quot; (6) "
Figure 112015046008356-pat00068

here,
Figure 112015046008356-pat00069
and
Figure 112015046008356-pat00070
S denotes the thickness of the object to be inspected,
Figure 112015046008356-pat00071
and
Figure 112015046008356-pat00072
The time required for the propagation of the longitudinal wave signal and the transverse wave signal in the object under test,
Figure 112015046008356-pat00073
E is the longitudinal elastic modulus, G is the lateral elastic modulus,
Figure 112015046008356-pat00074
Represents the density of the subject. 14. The method of claim 13,
The elastic properties
Poisson's ratio, longitudinal elastic modulus, and transverse elastic modulus.
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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2792286B2 (en) * 1991-11-12 1998-09-03 日本鋼管株式会社 Method for measuring elastic constant of specimen
JP2009276095A (en) * 2008-05-12 2009-11-26 Jfe Civil Engineering & Construction Corp Non-destructive flaw detecting method and non-destructive flaw detector
KR100955783B1 (en) * 2008-05-07 2010-05-06 한국과학기술원 Nondestructive testing method of concrete structures using stress wave techniques
KR20120113161A (en) * 2011-04-04 2012-10-12 주식회사 포스코 Measuring method and measruting apparatus of poisson's ratio

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2792286B2 (en) * 1991-11-12 1998-09-03 日本鋼管株式会社 Method for measuring elastic constant of specimen
KR100955783B1 (en) * 2008-05-07 2010-05-06 한국과학기술원 Nondestructive testing method of concrete structures using stress wave techniques
JP2009276095A (en) * 2008-05-12 2009-11-26 Jfe Civil Engineering & Construction Corp Non-destructive flaw detecting method and non-destructive flaw detector
KR20120113161A (en) * 2011-04-04 2012-10-12 주식회사 포스코 Measuring method and measruting apparatus of poisson's ratio

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