JP4938050B2 - Ultrasonic diagnostic evaluation system - Google Patents

Description

  The present invention estimates the strength of concrete by measuring the ultrasonic velocity (sound velocity) propagating in the vicinity of the concrete or in the vicinity of the surface using ultrasonic waves propagating in the air. The present invention relates to an ultrasonic diagnostic evaluation apparatus that nondestructively detects and images a defect or unhealthy part.

  Concrete is widely used in social infrastructure structures such as buildings, roads, and tunnels. However, with the lapse of years of use, surface cracks, rusting of rebars due to intrusion of rainwater, deterioration of concrete adhesion, neutralization of concrete, alkali aggregate reaction, etc. occur.

  As non-destructive evaluation methods for concrete, laser light, visual crack detection, hammering inspection, etc. are mainly used. These methods can distinguish between a healthy part and an abnormal part, but cannot detect an accurate position of an internal defect or an unhealthy part of an interface between a reinforcing bar and a concrete. Also, the sound velocity associated with concrete strength cannot be measured.

  An ultrasonic sensor is pressed against the concrete surface via a grease-like acoustic binder to transmit and receive ultrasonic waves, and the sound velocity of a plate-like concrete specimen is measured to predict the strength. There is a problem that the variation of the measured value is large depending on the contact state between the concrete.

  Also, as shown in Patent Document 1, there is a method of measuring the speed of sound by a non-contact transmission method and imaging an internal defect by placing a resin composite material or wood between two air ultrasonic sensors. To do.

  Moreover, as shown to patent documents 2-4, the technique which transmits an ultrasonic wave from the one side of a thin plate like a resin-type composite material via air, and receives the mode conversion board wave with the air ultrasonic sensor of the same side also exists. Exists.

Patent Publication 2002-195987 (FIG. 1) Patent Publication 2006-138818 (FIG. 1) Japanese Patent Publication No. 2007-10737 (FIG. 1) Japanese Patent Publication No. 2008-16497 (FIG. 1)

  However, in the case of inhomogeneous and thick materials that contain multiple components such as cement, sand, gravel and air, such as concrete, the ultrasonic waves are significantly scattered at each component interface during propagation. The application of the law has been considered difficult. In addition, it is extremely difficult to use a transmission method in which ultrasonic sensors are arranged on both sides of an inspection target in a constructed concrete structure, and a measuring device that can inspect from one side of the inspection target is needed. .

  In view of the above circumstances, the present invention transmits and receives ultrasonic waves via air from one side of a concrete structure to be inspected using an air ultrasonic method, and propagates in longitudinal, transverse, or surface waves in concrete. An object of the present invention is to provide an ultrasonic diagnostic apparatus capable of measuring the velocity in a non-contact manner, estimating the strength of the concrete, and detecting and imaging a reinforcing bar or a defect existing inside the concrete.

In order to achieve the above object, in the invention according to claim 1, a transmission signal generator that generates an electrical signal for ultrasonic excitation in response to a trigger signal from a personal computer is generated from the transmission signal generator. A transmission signal amplifying unit that electrically amplifies the applied electrical signal and applies it to the ultrasonic transmission unit, converts the electric signal amplified by the transmission signal amplification unit into ultrasonic vibrations, and ultrasonically transmits to the object to be measured via air An ultrasonic transmission sensor that receives vibration, an ultrasonic reception sensor that receives ultrasonic waves propagated in the object to be measured or on the surface via air, and only a specific frequency band component of the received waveform received by the ultrasonic reception sensor. A preamplifier with a bandpass filter that transmits and amplifies, a reception amplification unit that further amplifies a reception waveform that is transmitted and amplified by the preamplifier with the bandpass filter, and the reception A / D converter for digitally converting the received waveform amplified by the width portion, a waveform storage unit for digitally recording the received waveform converted by the A / D converter, and a digital waveform for the received waveform recorded in the waveform storage unit Using the waveform processing unit that performs processing, the preset propagation distance in the air, the ultrasonic propagation distance inside or near the concrete, and the received wave arrival time of the recorded received waveform, the longitudinal wave, the transverse wave, or the surface wave velocity is calculated. Sound velocity calculation unit to calculate, distance adjustment mechanism between test specimens for variably adjusting the distance between the ultrasonic transmission sensor and the ultrasonic reception sensor with respect to the non-measurement object, and the non-measurement object between the ultrasonic transmission sensor and the ultrasonic reception sensor An azimuth adjusting mechanism that variably adjusts the incident angle with respect to the sensor and a sensor-to-sensor distance adjusting mechanism that variably adjusts the distance between the ultrasonic transmission sensor and the ultrasonic receiving sensor are mounted. An electric signal generated by the transmission signal generation unit based on a command from the personal computer, amplified by the transmission signal amplification unit, and air from the ultrasonic transmission sensor. The ultrasonic vibration is incident on the concrete object to be measured, and the vertical distance longitudinal wave, the transverse wave, or the surface wave is adjusted by adjusting the inter-test body distance adjusting mechanism, the azimuth adjusting mechanism, and the inter-sensor distance adjusting mechanism. The ultrasonic vibration that is excited and propagated in the concrete object to be measured and in the vicinity of the surface is received by the ultrasonic reception sensor, and the received waveform is amplified by the preamplifier with the bandpass filter and the reception amplification unit, Digitally converted by the A / D converter, the digital waveform is recorded in the digital waveform recorder, and the propagation distance in air set in advance by the sound velocity calculator Using the ultrasonic propagation distance inside or near the surface of the concrete and the received wave arrival time of the recorded digital waveform, the longitudinal wave, the transverse wave, or the surface wave velocity at an arbitrary position of the concrete object to be measured is obtained. While calculating the Young's modulus and Poisson's ratio of the concrete from the longitudinal velocity or the transverse velocity among the obtained velocities, the strength of the concrete measurement object is evaluated, while the reception time of the reflected wave signal from the reinforcing bars or defects inside the concrete is calculated. The position of the reinforcing bar or the defect is identified by converting it into the propagation distance in the concrete, and the portion exceeding the predetermined threshold of the amplitude of the reflected wave signal is converted into black and white shading or color tone on the personal computer screen. It is characterized by imaging.
Note that the Young's modulus E and Poisson's ratio ν of concrete can be obtained by a personal computer using the following formula.
E = ρVt ² (3γ ² -4) / (γ ² -1)
ν = (1-2γ ² ) / [2 (1-γ ² )]
Where ρ is density, γ = V _L / V _T , V _L is the longitudinal wave velocity, and V _T is the transverse wave velocity.

  According to a second aspect of the present invention, in the ultrasonic diagnostic apparatus according to the first aspect, the electrical signal generated from the transmission signal generator is generated by a short pulse, a variable frequency burst wave, a chirp wave, or an arbitrary function generator. By selecting one of the selected signals, good measurement conditions can be set. That is, use short pulse waves for concrete with low attenuation such as mortar, burst waves with appropriate wave number for concrete containing coarse aggregate such as gravel and crushed stone, and chirp waves for thick concrete with large attenuation. Therefore, it is possible to receive a waveform with a good SN ratio.

  In the invention according to claim 3, in the ultrasonic diagnostic apparatus according to claim 1 or 2, the cross-correlation function between the received waveform and the transmitted waveform is calculated or propagated through the concrete by an incident burst wave. Receive waveform pulse by applying the time inversion method to the waveform obtained by performing Fourier transform on the signal obtained by Fourier transforming the received signal and applying the inverse transform to the Fourier transform of the incident burst wave. The SN ratio can be improved by compressing.

  In the invention according to claim 4, in the ultrasonic diagnostic apparatus according to any one of claims 1 to 3, complete non-contact measurement can be performed by using an air ultrasonic sensor as the ultrasonic transmission sensor. , The SN ratio can be improved.

  According to the present invention, ultrasonic waves are transmitted and received by several to several tens of millimeters away from the object to be measured using an air ultrasonic sensor, and longitudinal waves, transverse waves, or surface velocities propagating in the concrete member are measured in a non-contact manner. The strength of concrete can be estimated.

  In addition, the position of the moving table that moves the ultrasonic transmission sensor and the ultrasonic reception sensor along the surface of the concrete member is detected by an encoder, and the reception amplitude that exceeds a predetermined threshold at that position is converted into light or shade. By displaying, it is possible to non-destructively detect and image a reinforcing bar or a defect in the concrete.

  Because this is a non-contact measurement method that does not require the grease-like contact medium that is essential for conventional contact ultrasonic measurement, there is no fluctuation in measurement results depending on the state of the contact medium between the ultrasonic sensor and the object to be measured. . Moreover, since it is a non-contact measurement which does not require a grease-like contact medium, the surface of the object to be measured is not soiled.

  When an air ultrasonic sensor with a frequency of 350 kHz or less is used, ultrasonic waves can be transmitted and received as they are even if there is unevenness on the surface of the object to be measured in the order of 0.1 mm. There is no need for smoothing.

  Since it is a non-contact measurement, the incident angle from the air to the concrete can be set arbitrarily, and longitudinal waves, transverse waves, or surface waves can be excited in the concrete by setting to an appropriate angle.

It is a whole block explanatory view of the ultrasonic diagnostic apparatus of concrete using the air ultrasonic sensor concerning an embodiment. It is a conceptual diagram of a longitudinal wave, a transverse wave, and a surface wave measurement. It is an example of V transmission method longitudinal wave reception waveform. It is an example of a V transmission method transverse wave reception waveform. It is an example of a surface wave reception waveform. It is an example of the received waveform from a reinforcing bar. It is an example of the peeling area | region image by a propagation time difference map. It is an example of the reception amplitude change by a frequency sweep. It is an example of the received waveform of the smooth surface and surface groove part by a surface wave. It is an example of the received waveform of the defect part by a longitudinal wave V permeation | transmission method, and a non-defect part.

  An embodiment for measuring the velocity of longitudinal waves, transverse waves or surface waves in concrete using the present invention, or detecting rebars or internal defects in a non-contact manner will be described below with reference to the drawings.

  FIG. 1 is a diagram for explaining an ultrasonic diagnostic apparatus for concrete using an air ultrasonic sensor according to the present invention. The ultrasonic diagnostic apparatus 1 includes a transmission signal generation unit 2 that transmits an electric signal to the ultrasonic transmission sensor 4, a transmission signal amplification unit 3 that amplifies the electric signal, and the ultrasonic transmission sensor 4 and the ultrasonic reception sensor 5. An azimuth adjusting mechanism 21 that adjusts the azimuth with respect to the non-measurement object, a distance adjustment mechanism 22 that adjusts the distance between the ultrasonic sensors 4 and 5, and the object 30 to be measured, the ultrasonic transmission sensor 4, and the ultrasonic reception sensor 5. A movable table 20 equipped with an inter-sensor distance adjusting mechanism 23 and an encoder 7 for adjusting the distance between them, a preamplifier 6 with a band-pass filter for amplifying a reception waveform received by the ultrasonic wave reception sensor 5, and an amplification of the reception waveform Received signal amplification section 8, A / D conversion section 9 for high-speed A / D conversion of the amplified analog signal waveform, waveform storage section 10 for digital recording of the signal waveform, waveform processing section 11, sound speed calculation section 2, an image display unit 13 and the encoder signal reception storage unit 14 is constructed. Of the above components constituting the ultrasonic diagnostic apparatus 1, the transmission signal generation unit 2, the A / D conversion unit 9, the waveform recording unit 10, the waveform processing unit 11, the sound speed calculation unit 12, the image display unit 13, The encoder signal reception storage unit 14 is built in the personal computer 15.

When measuring the longitudinal wave and the transverse wave sound velocity of concrete, as shown in FIG. 2, the ultrasonic transmission sensor 4 and the ultrasonic reception sensor 5 are arranged on one side of the object to be measured 30, and the measurement method by the V transmission method is used. The incident angle θ corresponding to the ultrasonic propagation path determined by the thickness h of the object to be measured 30, the ultrasonic incident angle and the reception position is set based on Snell's law, and the reflected waveform from the back surface of the object to be measured 30 is recorded. From the propagation time, the longitudinal wave and the transverse wave sound velocity Vc of the concrete are calculated by the equation (1).
Vc = (2h / cos θ _R ) / (Tt−Ta) (1)
Where h is the thickness of the concrete
θ _R : Refraction angle
Tt: Reception time
Ta: Air propagation time = Air propagation distance / Air sound speed.

The incident angle θ corresponding to the refraction angle θ _R is calculated by Equation (2) using the sound speed of concrete assumed by Snell's law.
sin θ / Va = sin θ _R / Vc
Where Va: sound velocity in the air
Vc: Longitudinal wave or transverse wave sound velocity of concrete If an accurate sound velocity is required, the measurement is repeated while changing the incident angle until the assumed sound velocity matches the calculated sound velocity within the allowable error range.

  FIG. 3 shows an example of a longitudinal wave reflection waveform on the back surface of a concrete block obtained by the V transmission method using a planar air ultrasonic sensor having a center frequency of 320 kHz. The thickness h of the concrete was 100 mm, and the longitudinal wave refraction angle was 30 degrees. The distance between the ultrasonic transmission sensor 4 and the ultrasonic reception sensor 5 is about 115 mm on the concrete surface, and the propagation distance in the concrete is about 230 mm. Since the air propagation distance is set to 24 mm, the air propagation time is 69 μs. The longitudinal wave velocity is calculated to be about 3900 m / s from the rise time 128 μs indicated by the arrow in FIG.

  An example of the transverse wave reflection waveform on the back surface of the concrete block obtained by the V transmission method is shown in FIG. The transverse wave refraction angle was 30 degrees. The distance between the ultrasonic transmission sensor 4 and the ultrasonic reception sensor 5 is 115 mm on the concrete surface, and the propagation distance in the concrete is about 230 mm. Since the air propagation distance is set to 24 mm, the air propagation time is 69 μs. The transverse wave velocity is calculated as 1840 m / s from the rise time 194 μs indicated by the arrow in FIG.

  FIG. 5 shows a surface wave reception waveform when the surface wave propagation distance of the concrete block is increased every 50 mm from 50 mm to 70 m. From the rising portion reception time difference 10 μs (206 μs−196 μs) indicated by the arrow with respect to the propagation distance difference 20 mm, the surface wave velocity is calculated to be about 2000 m / s.

  In the longitudinal wave V transmission method, the received waveform in the cross section including the reinforcing bar and the cross section not including the reinforcing bar are obtained by adjusting the distance between the ultrasonic transmission sensor 4 and the ultrasonic receiving sensor 5 so that the reinforcing bar position becomes the reflection position. The received waveforms at are shown in FIGS. 6 (A) and 6 (B). As shown by the arrows, it can be seen that the reflected waves from the reinforcing bars are significantly large.

  FIG. 7 shows an example of an image representing the position of the reinforcing bar 31 in the concrete block using the encoder 7 that measures the in-plane relative position of the movable table 20 to the test body 30 shown in FIG. The part where the amplitude of the part of the arrow of FIG. 6 (A) exceeds the threshold value shown by the broken line when the reinforcing bar 31 of FIG. 6 (B) is not displayed is displayed in gray. Note that the threshold value is generally the maximum value of the noise level of the portion of the concrete to be measured that does not include the reinforcing bar.

In the above description, the method of measuring the longitudinal wave and the transverse wave velocity by the V transmission method has been described. However, the longitudinal wave and the transverse wave velocity may be measured by the resonance method described below. That is, as shown in FIG. 1, the ultrasonic transmission sensor 4 and the ultrasonic reception sensor 5 are arranged at intervals of 40 mm across the sound insulating material 24, and 20 variable frequency burst waves are almost perpendicular to the concrete having a thickness of 100 mm. FIG. 8 shows the received waveform when the frequency is incident and the frequency is swept. The amplitude is maximum at 340 kHz. The resonance condition for the propagation distance L when the upper and lower surfaces are free surfaces is given by equation (3).
L = λ (2N + 1) / 2 .. Formula (3)
Here, λ is a wavelength and is expressed by Vc / f. f is the resonance frequency and N is an integer.
When the propagation distance is 102 mm and N = 8, the longitudinal wave velocity of the concrete is about 4000 m / s, and the difference in the longitudinal wave velocity by the propagation time measurement in FIG. 2 is about 2.5%. Thus, the longitudinal wave velocity of the concrete can also be obtained using the resonance method.

Thus, seeking longitudinal wave velocity V _L and transverse wave velocity V _T as described above, these velocity ^{E = ρVt 2 (3γ 2 -4} ) / (γ 2 -1)
ν = (1-2γ ² ) / [2 (1-γ ² )]
ρ is density, γ = V _L / V _T ,
By applying the above formula and obtaining the Young's modulus E and Poisson's ratio ν of the concrete by the personal computer 15, the strength of the concrete measured object can be evaluated.

  Further, the position of the reinforcing bar 31 or the defect 32 is identified by converting the reception time of the reflected wave signal from the reinforcing bar 31 or the defect 32 inside the concrete into the propagation distance in the concrete using the obtained longitudinal wave velocity and the transverse wave velocity. The portion whose position is identified and where the amplitude of the reflected wave signal exceeds a predetermined threshold value can be converted into an image by converting it into black and white shading or color tone on the image display unit 13 of the personal computer 15. it can.

  Also, FIG. 9 shows surface wave reception waveforms with and without a surface groove. FIG. 9 (A), (A) shows a waveform with a propagation distance of 90 mm across a grooved surface portion and a groove for a test body having a groove of 2 mm width and 100 mm depth at the longitudinal center of a 400 × 200 × 200 mm concrete block. Shown in B). As shown in FIG. 9A, a clear surface wave is received at the surface portion without the groove, but in the measurement across the groove, the surface wave is not received as shown in FIG. 9B. A weak surface wave signal may be received depending on the depth and width of the surface groove or crack. Then, as shown in FIG. 6, a threshold value exceeding a predetermined noise level is set, and the surface wave reception amplitude exceeding the threshold value is imaged on the image display unit 13 of the personal computer 15 to visualize the surface defect portion. be able to.

  FIG. 10A and FIG. 10B show longitudinal wave reception waveforms of a defective portion and a healthy portion existing in the center portion of a 200 × 100 × 100 mm concrete block using V transmitted longitudinal waves. When the defect 32 as shown in FIG. 1 exists, a scattered wave signal is detected at the position of the arrow as shown in FIG. On the other hand, in the healthy part without the defect 32, the back reflection waveform is received with a delay of 20 μs. Therefore, an internal defect can be visualized by identifying the position having this time difference and imaging it on the image display unit 13 of the personal computer 15.

  In the above-described embodiment, it has been described that a completely non-contact measurement can be performed by using an air ultrasonic sensor as an ultrasonic transmission sensor. However, for a material with significant attenuation, an acoustic coupling is used as an ultrasonic transmission sensor. The S / N ratio can be improved by using a contact-type vibration source that does not use an agent, for example, a flying object having a specific frequency band or an impact hammer.

DESCRIPTION OF SYMBOLS 1 Ultrasonic diagnostic apparatus 2 Transmission signal generation part 3 Transmission signal amplification part 4 Ultrasonic transmission sensor 5 Ultrasonic reception sensor 6 Preamplifier with a band pass filter 7 Encoder 8 Reception amplification part 9 A / D conversion part 10 Waveform storage part 11 Waveform processing Unit 12 Sound velocity calculation unit 13 Image display unit 14 Encoder signal reception storage unit 15 Personal computer 20 Moving table 21 Ultrasonic sensor orientation adjustment mechanism 22 Ultrasonic sensor / distance adjustment mechanism 23 Ultrasonic sensor distance adjustment mechanism 24 Sound insulation material 30 DUT 31 Reinforcing bar 32 Defect

Claims (4)

A transmission signal generator for generating an electrical signal for ultrasonic excitation in response to a trigger signal from a personal computer, a transmission signal for electrically amplifying the electrical signal generated from the transmission signal generator and applying it to the ultrasonic transmitter An amplifying unit, an ultrasonic transmission sensor that converts the electrical signal amplified by the transmission signal amplifying unit into ultrasonic vibrations, and injects ultrasonic vibrations into the concrete measurement object via air, propagated in or on the surface of the measurement object Ultrasonic wave receiving sensor that receives ultrasonic waves through the air, preamplifier with bandpass filter that transmits and amplifies only a specific frequency band component of the received waveform received by the ultrasonic wave receiving sensor, transmitted through the preamplifier with bandpass filter A reception amplification unit for further amplifying the amplified reception waveform, an A / D conversion unit for digitally converting the reception waveform amplified by the reception amplification unit, the A Waveform storage unit that digitally records the received waveform converted by the / D conversion unit, waveform processing unit that performs digital waveform processing on the received waveform recorded in the waveform storage unit, preset propagation distance in air, and inside or near the surface of concrete A sound velocity calculation unit that calculates a longitudinal wave, a transverse wave, or a surface wave velocity using the ultrasonic wave propagation distance and the reception wave arrival time of the recorded reception waveform, and the non-existence of the ultrasonic transmission sensor and the ultrasonic reception sensor A distance adjustment mechanism between test specimens that variably adjusts a distance to a measurement object, an azimuth adjustment mechanism that variably adjusts an incident angle of the ultrasonic transmission sensor and the ultrasonic reception sensor with respect to a non-measurement object, the ultrasonic transmission sensor, and the ultrasonic wave It is equipped with an inter-sensor distance adjustment mechanism that variably adjusts the distance between the receiving sensors, and a movable table that can move along the surface of the object to be measured.
The electrical signal generated by the transmission signal generation unit based on a command from the personal computer is amplified by the transmission signal amplification unit, and ultrasonic vibration is applied to the concrete object to be measured from the ultrasonic transmission sensor via air. Incidently adjust the inter-specimen distance adjusting mechanism, the azimuth adjusting mechanism, and the inter-sensor distance adjusting mechanism to excite a vertical incident longitudinal wave, a transverse wave, or a surface wave, and the inside and the surface of the concrete object to be measured The ultrasonic vibration propagated in the vicinity is received by the ultrasonic receiving sensor, and the received waveform is amplified by the preamplifier with the bandpass filter and the reception amplification unit, and then digitally converted by the A / D conversion unit. Waveforms are recorded in the digital waveform recording unit, and the propagation distance in air and the inside or near the surface preset by the sound velocity calculation unit Using the ultrasonic propagation distance and the received wave arrival time of the recorded digital waveform, the longitudinal wave, the transverse wave, or the surface wave velocity at an arbitrary position of the concrete object to be measured is obtained. Calculate the Young's modulus and Poisson's ratio of concrete from the velocity or shear wave velocity to evaluate the strength of the concrete object to be measured, while converting the reception time of the reflected wave signal from the reinforcing bars or defects inside the concrete into the propagation distance in the concrete The position of the reinforcing bar or the defect is identified by converting the portion of the reflected wave signal whose amplitude exceeds a predetermined threshold into a black and white shade or color tone on a personal computer screen and imaged. Ultrasound diagnostic device.   2. The ultrasonic diagnostic apparatus according to claim 1, wherein the electrical signal generated from the transmission signal generator is a short pulse, a variable frequency burst wave, a chirp wave, or a signal generated by an arbitrary function generator.   Signal obtained by calculating the cross-correlation function between the received waveform and the transmitted waveform, or by Fourier transforming the received signal propagated in the concrete by the incident burst wave, and applying the inverse transform to the Fourier transform of the incident burst wave The signal-to-noise ratio is improved by compressing the received waveform pulse by applying a time reversal method in which the waveform obtained by performing inverse Fourier transform on the waveform is applied to the incident waveform. Ultrasonic diagnostic equipment.   The ultrasonic diagnostic apparatus according to claim 1, wherein the ultrasonic transmission sensor is an air ultrasonic sensor.

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