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Ultrasonic detection apparatus and ultrasonic detection method employing the same

Imported: 24 Feb '17 | Published: 06 Jan '04

Masayuki Hirose

USPTO - Utility Patents

Abstract

While a transmitting transducer (

2

a) for transmitting an ultrasonic wave and a receiving transducer (

2

b) for receiving an ultrasonic wave are moved within a predetermined circular region (

7) on a surface of a material being measured, ultrasonic waves are transmitted and received 10,000 times. Then, arithmetic averaging is performed every time an ultrasonic wave is received, on the ultrasonic wave and ultrasonic waves that have been received until then. For example, the aforementioned predetermined frequency is given by ((n±(½))×(10

6×v/L))(Hz), where L is a variation in distance between the transmitting transducer and the receiving transducer, v is a transmission velocity of an ultrasonic wave transmitting in a material being detected, and n is a natural number. Consequently, it is possible to detect, with high accuracy, the thickness of a concrete material having a narrow width and a thick thickness, the thickness of the covering of a reinforcing bar and the diameter thereof, the depth of a crack and the like.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating an ultrasonic detection apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic view illustrating an embodiment that employs a one-transducer method.

FIG. 3 is a schematic view illustrating the positional relationship between a transmitting transducer and a receiving transducer in the method according to a first embodiment method of the present invention.

FIGS.

4(

a) through (

c) are graphs illustrating time series waveforms resulted from a measurement according to the method of the first embodiment.

FIG. 5 is a graph illustrating a time series waveform provided by the measurement of the width of a concrete material

51

a.

FIG. 6 is a schematic view illustrating the positional relationship between a transmitting transducer and a receiving transducer specified by a method according to a second embodiment method of the present invention.

FIG. 7 is a graph illustrating a time series waveform resulted from a measurement according to the method of the second embodiment.

FIG. 8 is a view illustrating a material to be detected which is employed in an example of measurement of the depth of a crack, (a) being a perspective view, (b) being a plan view, (c) being a cross-sectional view taken along line A—A of (b), and (d) being a cross-sectional view taken along line B—B of (b).

FIGS.

9(

a) through (

c) are graphs illustrating time series waveforms resulted from the measurement of the depth of a crack.

FIGS.

10(

a) and (

b) are schematic views illustrating a method for moving one transducer.

FIG. 11 is a cross-sectional view illustrating a material to be detected which is employed in an embodiment of measuring the depth of a deformed reinforcing bar.

FIG. 12 is a graph illustrating a spectrum obtained when a measurement is made with transducers

33

a and

33

b remaining fixed at both sides across a fixed point C.

FIGS.

13(

a) and (

b) are graphs illustrating time series waveforms resulted from the measurement of the depth of a deformed reinforcing bar.

FIG. 14 is a graph illustrating spectra obtained by filtering of C

2

n·Y

1,1.

FIGS.

15(

a) and (

b) are graphs illustrating time series waveforms corresponding to the spectra shown in FIG.

14.

FIG. 16 is a view illustrating a path of ultrasonic waves in a deformed reinforcing bar, (a) being a side view and (b) being a cross-sectional view taken along line C—C of (a).

FIG. 17 is a schematic view illustrating ultrasonic waves transmitting in a circumferential direction of a circular reinforcing bar.

FIGS.

18(

a) and (

b) are graphs illustrating time series waveforms obtained from a concrete material having no cracks formed thereon.

FIGS.

19(

a) and (

b) are schematic view illustrating the transmission path of ultrasonic waves in a concrete material having no crack formed therein.

FIG. 20 is also a schematic view illustrating the transmission path of ultrasonic waves in a concrete material having no crack formed therein.

FIG. 21 is a schematic view illustrating a jig for a third embodiment of the present invention.

FIG. 22 is a view of an arithmetic mean y

Dk(t), an arithmetic mean y

Dk+1(t), and their arithmetic mean when a given frequency component is shifted by one cycle between the arithmetic mean y

Dk(t) and the arithmetic mean y

Dk+1(t), (a) being a schematic view illustrating the arithmetic mean y

Dk(t), (b) being a schematic view illustrating the arithmetic mean y

Dk+1(t), and (c) being a schematic view illustrating their arithmetic mean

fy

ave(t).

FIG. 23 is a view of an arithmetic mean y

Dk(t), an arithmetic mean y

Dk+1(t), and their arithmetic mean when a given frequency component is shifted by one-half cycle between the arithmetic mean y

Dk(t) and the arithmetic mean y

Dk+1(t), (a) being a schematic view illustrating the arithmetic mean y

Dk(t), (b) being a schematic view illustrating the arithmetic mean y

Dk+1(t), and (c) being a schematic view illustrating their arithmetic mean

f/2y

ave(t).

FIG. 24 is a schematic view illustrating the transmission of waves produced when a measurement is made between A′ and B′ shown in FIG.

72(

b) by employing a two-transducer method.

FIG. 25 is a view illustrating a wave obtained through arithmetic averaging with two types of jigs being employed, (a) being a graph illustrating a Fourier spectrum and (b) being a graph illustrating a time series waveform.

FIG. 26 is a view illustrating a wave obtained with only jig D

2 being employed, (a) being a graph illustrating a Fourier spectrum and (b) being a graph illustrating a time series waveform.

FIG. 27 is a view illustrating a wave obtained with the center frequency being at 130 kHz, (a) being a graph illustrating a Fourier spectrum and (b) being a graph illustrating a time series waveform.

FIG. 28 is a graph illustrating the relationship between a frequency fi and a normalized amplitude.

FIG. 29 is a cross-sectional view illustrating a concrete material in which a reinforcing bar as a subject to be detected is embedded.

FIG. 30 is a schematic view illustrating the transmission of a wave produced upon detection of a deformed reinforcing bar

82 shown in FIG.

73.

FIG. 31 is a view illustrating waves with a frequency component being 2f

B and two types of jigs being employed, (a) being a schematic view illustrating arithmetic mean y

D1(t) obtained with one transducer being placed at a short distance from the other, (b) being a schematic view illustrating arithmetic mean y

D2(t) obtained with one transducer being placed at a long distance from the other, and (c) being a schematic view illustrating their arithmetic mean y

ave(t).

FIG. 32 is a graph illustrating the Fourier spectrum of a frequency component having a center frequency of 590 kHz used for gaining.

FIG. 33 is a schematic view illustrating a time series waveform at each position of measurement.

FIG. 34 is a schematic view illustrating distances between the transducers of each jig.

FIG. 35 is a graph illustrating time series waveforms obtained when four jigs are used.

FIG.

36(

a) is a schematic view illustrating a generated wave corresponding to peak

92, (b) being a schematic view illustrating a generated wave corresponding to peak

93, (c) being a schematic view illustrating generated waves corresponding to peaks

94 and

96, and (d) being a schematic view illustrating a generated wave corresponding to peak

64.

FIG. 37 is a graph illustrating a time series wave of a broadband frequency component gained from input ultrasonic waves with the center frequency being at 1100 kHz.

FIGS.

38(

a) through (

d) are schematic views illustrating waves obtained when each jig is used and

38(

e) is a schematic view illustrating their arithmetic mean.

FIG. 39 is a view illustrating the procedure of arithmetic averaging according to equation 20.

FIG. 40 is a graph illustrating changes in spectrum.

FIG. 41 is a graph illustrating spectra

Ba

5 and a

5.

FIG. 42 is a graph illustrating an arithmetic mean wave obtained when both transmitting and receiving transducers have an oscillator 40 mm in diameter whose resonant frequency of 500 kHz.

FIG. 43 is a graph illustrating a component wave gained by applying equations 52 and 53 to the arithmetic mean wave of FIG. 42 with the frequency shown in the following equation 55 being employed as the center frequency.

FIGS.

44(

a) through (

d) are schematic views illustrating various methods for scanning a transducer without using a measurement tool.

FIG. 45 is a cross-sectional view illustrating the typical shape of a longitudinal-wave transducer.

FIG. 46 is a schematic view illustrating the manner of transmission of longitudinal ultrasonic waves input to a concrete material from a surface thereof directly downwards.

FIG. 47 is a graph illustrating the results of measurement by the method, shown in FIG.

44(

b), for scanning the model of concrete of FIG.

72.

FIG. 48 is a graph illustrating the comparison between the spectra of interference waves interfering detection and waves of targets to be detected such as plate thickness.

FIG. 49 is a graph illustrating the result of raising a wave or a component wave having a center frequency of 200 kHz of FIG. 42 to the third power.

FIG. 50 is a graph illustrating the result of gaining a component wave with the center frequency being at f

D=65 kHz.

FIG. 51 is a schematic cross-sectional view illustrating a model of concrete used for measurement.

FIG. 52 is a graph illustrating component waves gained at each measurement point with the center frequency being at 190 kHz.

FIG. 53 is a graph illustrating an example obtained in the course of shifting, by filtering, the center frequency employed for gaining a wave obtained by raising each component wave of FIG. 52 to the tenth power.

FIG. 54 is a graph illustrating a 200 kHz component wave provided by measurement

3.

FIG. 55 is a view illustrating an amplified component wave obtained at a center frequency of 680 kHz reached after gradual sweeping of center frequencies towards higher frequencies.

FIG. 56 is a graph illustrating a component wave having a center frequency of 1 MHz.

FIG. 57 is a schematic view illustrating the transmission of various waves in a concrete material that has been subjected to aging.

FIG. 58 is a schematic view illustrating the path of critical refracted waves.

FIG. 59 is a schematic view illustrating a method for detecting a reinforcing bar in a concrete material on the surface of which cracks are formed.

FIG. 60 is a view illustrating a concrete material that has been left for five years dried after poured, (a) being a plan view thereof, (b) being a cross-sectional view taken along line D—D of (a), and (c) being a cross-sectional view taken along E—E of (a).

FIG. 61 is a view illustrating waves received at measurement position P

28, (a) being a graph illustrating a case where no electrical noise nor disturbance has been eliminated and (b) being a graph illustrating a case where they have been eliminated.

FIG. 62 is a graph illustrating a Fourier spectrum with the center frequency being at 120 kHz.

FIG. 63 is a schematic view illustrating a time series wave obtained at each measurement position when electrical noise or the like has been eliminated.

FIG. 64 is a schematic view also illustrating a time series wave obtained at each measurement position when electrical noise and the like have been eliminated, with the scale of FIG. 63 being changed.

FIG. 65 is a schematic view illustrating the transmission path of refracted waves at measurement positions P

23 and P

25.

FIG. 66 is a schematic view illustrating the order of generation at various paths.

FIG.

67(

a) is a schematic view illustrating an arithmetic mean wave y

A(t) and (b) is a schematic view illustrating an arithmetic mean wave y

B(t).

FIG.

68(

a) is a graph showing a pulsed voltage, (b) being a graph showing the spectrum of the pulsed voltage, and (c) being a graph showing a time series waveform of the pulsed voltage.

FIG.

69(

a) is a graph showing a stepped voltage, (b) being a graph showing the spectrum of the stepped voltage, and (c) being a graph showing a time series waveform of the stepped voltage.

FIG. 70 is a schematic view illustrating a concrete plate as a material to be detected.

FIG. 71 is a graph illustrating a reflected wave obtained under a prior-art measuring method.

FIG. 72 is a view illustrating a concrete pillar as a material to be detected, (a) being a schematic view thereof before being cut apart and (b) being a schematic view thereof after having been cut apart.

FIG. 73 is a schematic view illustrating the transmission of a wave produced when a transducer

52 is placed at center A for measurement of thickness.

FIG.

74(

a) through (

c) are graphs illustrating time series waveforms resulted from a prior-art detection method.

Claims

1. A ultrasonic detection apparatus wherein, in a measurement where, in a reinforced concrete structure having a plurality of reinforcing bars embedded in the concrete structure parallel to each other in a plane, letting a predetermined value of L be a distance between a transmitting transducer and a receiving transducer when the concrete structure has cracks on a surface thereof and letting another predetermined value of L be the distance when the concrete structure has no cracks, the transducers are arranged on the surface of the concrete structure to allow a line segment connecting between two transducers to be parallel to a longitudinal direction of the reinforcing bars, a received wave having the earliest time of generation is selected as a pertinent received wave from a plurality of received waves obtained by varying a position of said two transducers in the longitudinal direction of the reinforcing bars, and with a plurality of pertinent received waves obtained through the same measurement as the aforementioned one by varying a distance of said line segment by a given amount of x, a reinforcing bar is recognized to be present immediately under a measurement point of a received wave indicative of a maximum value of a curve connecting between times of generation of these waves.

2. The ultrasonic detection apparatus according to claim 1, wherein a depth d of an embedded reinforcing bar is given by d = ( t - L V p s ) ( 2 V p c cos θ - 2 V p s tan θ )

and it holds that θ = sin - 1 V p c V p s ,

where t is a time of generation of an ultrasonic wave received on a surface of the concrete structure immediately above the reinforcing bar,

cV

P is a sound velocity in the concrete structure,

and

SV

P is a sound velocity in the reinforcing bar.

3. An ultrasonic detection apparatus, wherein with pertinent received waves obtained from a measurement where, in a reinforced concrete structure having a plurality of reinforcing bars embedded in the concrete structure parallel to each other in a plane, when a sound velocity

cV

P in the concrete structure is unknown, letting a predetermined value of L be a distance between a transmitting transducer and a receiving transducer when the concrete structure has cracks on a surface thereof and letting another predetermined value of L be the distance when the concrete structure has no cracks, the transducers are arranged on the surface of the concrete structure to allow a line segment connecting between said two transducers to be parallel to a longitudinal direction of the reinforcing bars, an unknown quantity or the sound velocity

cV

P in the concrete structure and a depth d of an embedded reinforcing bar are simultaneously determined from the following simultaneous equations, t 11 = 2 d V p c × 1 cos θ + 1 V p s ( ( L - 2 d tan θ ) ) , t 12 = 2 d 2 + b 2 V p c × 1 cos θ + 1 V p s ( L - 2 d 2 + b 2 tan θ ) ) , and θ = sin - 1 V p c V p s where t 11

is a time of generation of an ultrasonic wave received on the surface of the concrete structure immediately above the reinforcing bar, t

12 is a time of generation of an ultrasonic wave received at a position spaced by a predetermined distance b on a plane apart from the measurement point, and

sV

P is a sound velocity in the reinforcing bar.

4. The ultrasonic detection apparatus according to claim 3, wherein said pertinent received wave has the earliest time of generation among a plurality of received waves obtained by varying a position of said two transducers in the longitudinal direction of the reinforcing bars when the concrete structure has cracks on a surface thereof, and a received wave obtained from one measurement is employed as the pertinent received wave when no cracks are present on the surface.

5. The ultrasonic detection apparatus according to any one of claims 1 to 4 wherein said predetermined frequency is given by ( ( 1 2 + n ) × ( 10 6 × V ~ 1 2 · Δ L ) ) ( Hz )

where L is a predetermined value to be determined by a difference between the maximum and minimum values of a distance between said transmitting transducer and said receiving transducer, a diameter of a receiving transducer oscillator, a width of a receiving transducer oscillator on a line segment connecting between said two transducers, a property of a material being detected, a method for scanning transducers, and a difference between one-transducer and two-transducer measurements, {tilde over (V)} is an average sound velocity of a surface wave and direct wave produced in said material being detected, and n is a real number equal to 0 or greater.

6. The ultrasonic detection apparatus according to claim 5, wherein the aforementioned predetermined frequency is given by (f

D+n)(Hz) where a value of f

D to be determined from a resonant frequency of an outer sheath of a receiving transducer satisfies that f D > 1 2 · 10 6 × V ~ 1 2 · Δ L

and n is a real number equal to 0 or greater.

7. The ultrasonic detection apparatus according to claim 5, wherein in detecting a plate thickness or the like having a long distance for an ultrasonic wave to transmit, a received wave is multiplied a plurality of times by a time series filter G ( t ) = sin ( π 2 t 0 · t )

given by a predetermined value t

0, determined by a depth of a subject being detected and a sound velocity, to allow said predetermined frequency to be f D > 1 2 · 10 6 × V ~ 1 2 · Δ L

accordance with a f

D determined by a resonant frequency of an outer sheath of a receiving transducer.

8. The ultrasonic detection apparatus according to claim 5, wherein a received wave is multiplied a plurality of times by a time series filter G ( t ) = sin ( π t 0 · t ) ,

determined from a time of generation t

0 of a detected wave obtained from a component wave having f

D as a center frequency when a value of f

D determined by a resonant frequency of an outer sheath of a receiving transducer satisfies that f D > 1 2 · 10 6 × V ~ 1 2 · Δ L

or from a time of generation t

0 of a detected wave obtained from a component wave having f D > 1 2 · 10 6 × V ~ 1 2 · Δ L

as a center frequency when a value of f

D satisfies that f D > 1 2 · 10 6 × V ~ 1 2 · Δ L

to allow said predetermined frequency to be given by (f

D+n)(HZ) and ( ( 1 2 + n ) × ( 10 6 × V ~ 1 2 · Δ L ) ) ( Hz ) ,

respectively, where n is a real number equal to 0 or greater.

9. A method for detecting an ultrasonic wave wherein, in a measurement where, in a reinforced concrete structure having a plurality of reinforcing bars embedded in the concrete structure parallel to each other in a plane, letting a predetermined value of L be a distance between a transmitting transducer and a receiving transducer when the concrete structure has cracks on a surface thereof and letting another predetermined value of L be the distance when the concrete structure has no cracks, the transducers are arranged on the surface of the concrete structure to allow a line segment connecting between two transducers to be parallel to a longitudinal direction of the reinforcing bars, a received wave having the earliest time of generation is selected as a pertinent received wave from a plurality of received waves obtained by varying a position of said two transducers in the longitudinal direction of the reinforcing bars, and with a plurality of pertinent received waves obtained through the same measurement as the aforementioned one by varying a distance of said line segment by a given amount of x, a reinforcing bar is recognized to be present immediately under a measurement point of a received wave indicative of a maximum value of a curve connecting between times of generation of these waves.

10. The method for detecting an ultrasonic wave according to claim 9, wherein a depth d of an embedded reinforcing bar is d = ( t - L V p s ) ( 2 V p c cos θ - 2 V p s tan θ )

and it holds that θ = sin - 1 V p c V p s ,

where t is a time of generation of an ultrasonic wave received on a surface of the concrete structure immediately above the reinforcing bar,

cV

P is a sound velocity in the concrete structure, and

SV

P is a sound velocity in the reinforcing bar.

11. The method for detecting an ultrasonic wave according to any one of claims 9 to 10, wherein said predetermined frequency is given by ( ( 1 2 + n ) × ( 10 6 × V ~ 1 2 · Δ L ) ) ( Hz )

where L is a predetermined value to be determined by a difference between the maximum and minimum values of a distance between said transmitting transducer and said receiving transducer, a diameter of a receiving transducer oscillator, a width of a receiving transducer oscillator on a line segment connecting between said two transducers, a property of a material being detected, a method for scanning transducers, and a difference between one-transducer and two-transducer measurements, {tilde over (V)} is an average sound velocity of a surface wave and direct wave produced in said material being detected, and n is a real number equal to 0 or greater.

12. The method for detecting an ultrasonic wave according to claim 11, wherein the aforementioned predetermined frequency is given by (f

D+n)(Hz) where a value of f

D to be determined from a resonant frequency of an outer sheath of a receiving transducer satisfies that f D > 1 2 · 10 6 × V ~ 1 2 · Δ L

and n is a real number equal to 0 or greater.

13. The method for detecting an ultrasonic wave according to claim 11, wherein in detecting a plate thickness or the like having a long distance for an ultrasonic wave to transmit, a received wave is multiplied a plurality of times by a time series filter G ( t ) = sin ( π 2 t 0 · t ) ,

given by a predetermined value t

0, determined by a depth of a subject being detected and a sound velocity, to allow said predetermined frequency to be 1 2 · 10 6 × V ~ 1 2 · Δ L

in accordance with a f

D determined by a resonant frequency of an outer sheath of a receiving transducer.

14. The method for detecting an ultrasonic wave according to claim 11, wherein a received wave is multiplied a plurality of times by a time series filter G ( t ) = sin ( π t 0 · t ) ,

determined from a time of generation t

0 of a detected wave obtained from a component wave having f

D as a center frequency when a value of f

D determined by a resonant frequency of an outer sheath of a receiving transducer satisfies that f D > 1 2 · 10 6 × V ~ 1 2 · Δ L

or from a time of generation t

0 of a detected wave obtained from a component wave having 1 2 · 10 6 × V ~ 1 2 · Δ L

as a center frequency when a value of f

D satisfies that f D > 1 2 · 10 6 × V ~ 1 2 · Δ L ,

to allow said predetermined frequency to be given by (f

D+n)(Hz) and ( ( 1 2 + n ) × ( 10 6 × V ~ 1 2 · Δ L ) ) ( Hz ) ,

respectively, where n is a real number equal to 0 or greater.

15. A method for detecting an ultrasonic wave wherein with pertinent received waves obtained from a measurement where, in a reinforced concrete structure having a plurality of reinforcing bars embedded in the concrete structure parallel to each other in a plane, when a sound velocity

cV

P in the concrete structure is unknown, letting a predetermined value of L be a distance between a transmitting transducer and a receiving transducer when the concrete structure has cracks on a surface thereof and letting another predetermined value of L be the distance when the concrete structure has no cracks, the transducers are arranged on the surface of the concrete structure to allow a line segment connecting between said two transducers to be parallel to a longitudinal direction of the reinforcing bars, an unknown quantity or the sound velocity

cV

P in the concrete structure and a depth d of an embedded reinforcing bar are simultaneously determined from the following simultaneous equations, t 11 = 2 d V p c × 1 cos θ + 1 V p s ( ( L - 2 d tan θ ) ) , t 12 = 2 d 2 + b 2 V p c × 1 cos θ + 1 V p s ( L - 2 d 2 + b 2 tan θ ) ) , and θ = sin - 1 V p c V p s where t 11

is a time of generation of an ultrasonic wave received on the surface of the concrete structure immediately above the reinforcing bar, t

12 is a time of generation of an ultrasonic wave received at a position spaced by a predetermined distance b on a plane apart from the measurement point, and

sV

P is a sound velocity in the reinforcing bar.

16. The method for detecting an ultrasonic wave according to claim 15, wherein said pertinent received wave has the earliest time of generation among a plurality of received waves obtained by varying a position of said two transducers in the longitudinal direction of the reinforcing bars when the concrete structure has cracks on a surface thereof, and a received wave obtained from one measurement is employed as the pertinent received wave when no cracks are present on the surface.