CN102788845A

CN102788845A - Barker coding excitation ultrasonic detection method of concrete structure defect

Info

Publication number: CN102788845A
Application number: CN2012103230769A
Authority: CN
Inventors: 李长征; 王锐; 张清明; 周杨; 李姝昱; 杨磊; 冷元宝; 乔惠忠; 赵志忠; 谢义兵
Original assignee: Yellow River Institute of Hydraulic Research
Current assignee: Yellow River Institute of Hydraulic Research
Priority date: 2012-09-04
Filing date: 2012-09-04
Publication date: 2012-11-21

Abstract

The invention discloses a barker coding excitation ultrasonic detection method of a concrete structure defect. The method comprises 1 using a buck coding excitation energy converter at an emission end, enabling carrier waves to be cosine signals and enabling the energy converter to transmit width time signals; and 2 using a matched filtering method at a receiving end, conducting pulse compression on received reflected signals, and finally obtaining narrow pulse signals with high resolution ratio and big major and minor lobes. Barker codes are adopted at the emission end to modulate coding excitation and send modulated big-time-width signals, corresponding matched filtering processing is carried out on the received signals, and large-amplitude narrow-pulse signals can be obtained. The big-time-width signals are big in energy so that a certain range of reflected signals can be obtained when depth defects are detected, the major and minor lobes after the matched filtering processing are big, echo signals are high in range, defect positions can be accurately judged according to defect reflection time, and detection capability of the defects is improved accordingly.

Description

The Barker code excitation supersonic detection method of xoncrete structure defective

Technical field:

The present invention relates to a kind of xoncrete structure defect inspection method, relate in particular to a kind of Barker code excitation supersonic detection method that encourages the xoncrete structure defective of ultrasonic signal based on Barker code.

Background technology:

The means of at present ultrasound detection being carried out in the size and the position of concrete inner structure defective can be divided into two types substantially: the one, and pulse echo method at concrete surface excitation ultrasound signal, receives echoed signal in the same side and carries out the identification of defective; Another kind of is the sound wave through transmission technique, transmits in concrete one side, receive at opposite side, when receiving the sound of signal and changes in amplitude judge whether inner structure exists defective.Ultrasonic detection equipment is simpler, operate also very convenient, so be widely used in the xoncrete structure defects detection.

At the scene in the testing process, ground unrest disturbs greatlyyer sometimes, makes echo and noise signal aliasing, and perhaps echo is submerged in the noise signal fully, and the pulse excitation that places an order of this situation is difficult to judge flaw echoes, makes troubles to defects detection.On the other hand, for the detection of thicker concrete component, because sonic propagation length is bigger apart from the amplitude decay, be difficult for determining echoed signal in the reception signal, this also is one of problem of puzzlement engineering detecting personnel.

Summary of the invention:

, the echoed signal time low to xoncrete structure defects detection signal to noise ratio (S/N ratio) is difficult for interpretation; And it is long apart from concrete component detection problem; The purpose of this invention is to provide a kind of wide pulse signal through the emission macro-energy; In the receiving end matched filtering, obtain the echoed signal that main lobe is narrower, amplitude is higher, thus the Barker code excitation supersonic detection method of the xoncrete structure defective of the detectability of raising defective.

Technical scheme of the present invention realizes in the following manner:

A kind of Barker code excitation supersonic detection method of xoncrete structure defective: this method comprises:

1. adopt the code-excited transducer of Barker code at transmitting terminal, wherein carrier wave is the cosine impulse signal, makes the signal of transducer length launch time broad; 2. take the method for matched filtering at receiving end, the reflected signal that receives is carried out pulse compression, finally obtain the narrow pulse signal that resolution is higher, principal subsidiary lobe is bigger;

The practical implementation step:

Adopting the longest Barker code is N=13, {+1 ,+1 ,+1 ,+1 ,+1 ,-1 ,-1 ,+1 ,+1 ,-1 ,+1 ,-1 ,+1 },

1. confirm coding parameter according to defective approximate depth ; Barker code length

; Carrier frequency (transducer dominant frequency)

, unit chip carrier cycle number is n; The concrete velocity of wave is

,

Figure 2012103230769100002DEST_PATH_IMAGE010

; The duration of transmitted wave is less than the reflection interval that echo is propagated;

2. the Barker code coded signal is calculated in programming:

Figure 2012103230769100002DEST_PATH_IMAGE012

; Barker code is 1 o'clock

Figure 2012103230769100002DEST_PATH_IMAGE014

, and Barker code is-1 o'clock

Figure 2012103230769100002DEST_PATH_IMAGE016

.

3. coded signal

Figure 2012103230769100002DEST_PATH_IMAGE018

lead-in signal generator is used for excitation; Transmitting transducer directly docks with receiving transducer; Recorder signal ;

is as the matched filtering function; Signal length is

Figure 2012103230769100002DEST_PATH_IMAGE022

, and SF remains unchanged in all testing processes;

4. to seized concrete component; Adopt reflectometry or transmission beam method to detect;

is consistent with the transducer dominant frequency for transmission carrier frequency; Coded signal

is through signal generator stimulated emission transducer; The recorder signal is , and signal length is

Figure 2012103230769100002DEST_PATH_IMAGE026

;

5. the echoed signal that receives

is calculated with

, obtained signal

Figure 2012103230769100002DEST_PATH_IMAGE028

;

Figure 2012103230769100002DEST_PATH_IMAGE032

; As if

Figure 2012103230769100002DEST_PATH_IMAGE034

, get

Figure 2012103230769100002DEST_PATH_IMAGE036

in the computation process. individual point of

representative

waveform,

is increased to

Figure 2012103230769100002DEST_PATH_IMAGE040

from 1.

N is a n point of waveform;

6 According to

the peak time

, and amplitude determined position of the defect within the concrete.

Can also adopt short Barker code is N=2, N=3, N=4, N=5, N=7 or N=11.

Good effect of the present invention is:

Barker code is a kind of of pseudorandom two-phase sign indicating number, and the Barker code pumping signal has desirable ambiguity function, has good distance resolution.Adopt the excitation of Barker code modulating-coding at transmitting terminal, send bandwidth signals when ovennodulation big,, can obtain large amplitude, narrow pulse signal receiving signal through the corresponding matched Filtering Processing.Bandwidth signals is bigger because of energy when big; So when detecting dark defective, still can obtain the reflected signal of certain amplitude, bigger through the principal subsidiary lobe of matched filter processing, the echoed signal that amplitude is higher; Can accurately judge defective locations according to the defect reflection time, thereby improve the detectability of defective.

Description of drawings:

Fig. 1 is the principle schematic that concrete component of the present invention detects;

Peak value contrasted synoptic diagram after Fig. 2 received signal peak and the matched filtering of Barker code pumping signal for monopulse of the present invention encourages;

Fig. 3 is a concrete structure member crevices illustraton of model of the present invention;

Fig. 4 is that Barker code of the present invention detects result.

Embodiment:

Below in conjunction with accompanying drawing the present invention is done further explain:

Embodiment 1,

(1) detection in hole

(20cm * 20cm * 20cm), as shown in Figure 1, it is the horizontal cylindrical hole of 2cm that there is a diameter in test block central authorities to select a rock test block; Take both sides that the single-shot list of wearing is received detection mode; Measuring point is 10 and evenly distributes that wherein the 6th measuring point is just in time relative with the hole, and the transducer dominant frequency is 500kHz.At first detect with the monopulse energisation mode.Use carrier frequency to detect as 13 Barker code excitations of 500kHz then, main lobe peak value after the matched filtering and rect.p. detect the contrast of main lobe peak value and see Fig. 2.

Detect step:

1. Barker code length

Figure 2012103230769100002DEST_PATH_IMAGE046

; Carrier frequency (transducer dominant frequency)

Figure 2012103230769100002DEST_PATH_IMAGE048

500kHz, unit chip carrier cycle number is n=1; The concrete velocity of wave is

Figure 2012103230769100002DEST_PATH_IMAGE050

,

.This formula shows: the duration of transmitted wave is less than the reflection interval that echo is propagated;

2. Barker code coding letter

is calculated in programming

; Barker code is 1 o'clock

, and Barker code is-1 o'clock

.

3. with coded signal

The lead-in signal generator is used for excitation, and transmitting transducer directly docks with receiving transducer, the recorder signal

, As the matched filtering function, signal length does

=3000, SF is 1 * 10 in all testing processes ^-8S remains unchanged;

is through signal generator stimulated emission transducer; The recorder signal is

, and signal length is

=40000.

5. the echoed signal that receives

is calculated with

, obtained signal .

; As if , get

in the computation process.

6 According to

The peak time

, and amplitude determined position of the defect within the concrete.

Can find out that by Fig. 2 the peak value of signal is minimum after the 6th the measuring point matched filtering of Barker code excitation, can judge the position in hole thus.And the 6th measuring point peak value of monopulse mode of excitation is not minimum.Analyze the former because defective build-up effect to the long pulse pumping signal, the excitation signal pulse is long more, and the energy loss that runs into behind the hole is big more, show the height of peak value after the matched filtering, and the hole is less to the energy affect of single pulse signal.

Embodiment 2,

Crack Detection:

(Fig. 3 is seen at the dark 12cm of sillar place in the crack for 24cm * 24cm * 24cm), the wide about 1.5mm in crack to select sillar that horizontal fracture is arranged in the middle of one.The detection mode of taking the single-shot list to receive, transmitting probe and receiving transducer are at the sillar top; Use carrier frequency to detect as 13 Barker code excitations of 500kHz, Fig. 4 is the testing result of Barker code excitation, and visible main lobe peak value is narrower, and peak amplitude is higher, also can obviously find out secondary and three echoed signals.Can find out that by Fig. 4 there is reflected signal at 55 μ s places, the position that can judge the crack by the concrete velocity of wave is about 12cm.

Claims

1. the Barker code of an xoncrete structure defective encourages supersonic detection method: this method comprises:

1. adopt the code-excited transducer of Barker code at transmitting terminal, wherein carrier wave is a cosine signal, makes transducer launch signal when wide; 2. take the method for matched filtering at receiving end, the reflected signal that receives is carried out pulse compression, finally obtain the narrow pulse signal that resolution is higher, principal subsidiary lobe is bigger;

The practical implementation step:

(1). confirms coding parameter according to the defective approximate depth; Barker code length ; Carrier frequency is transducer dominant frequency

, and unit chip carrier cycle number is n; The concrete velocity of wave is

,

Figure 2012103230769100001DEST_PATH_IMAGE010

(2). the Barker code coded signal is calculated in programming:

Figure 2012103230769100001DEST_PATH_IMAGE012

; Barker code is 1 o'clock

Figure 2012103230769100001DEST_PATH_IMAGE014

, and Barker code is-1 o'clock

Figure 2012103230769100001DEST_PATH_IMAGE016

;

(3). with coded signal

Figure 2012103230769100001DEST_PATH_IMAGE018

Figure 2012103230769100001DEST_PATH_IMAGE020

,

As the matched filtering function, signal length does

Figure 2012103230769100001DEST_PATH_IMAGE022

, SF remains unchanged in all testing processes;

(4). to seized concrete component; Adopt reflectometry or transmission beam method to detect;

is consistent with the transducer dominant frequency for transmission carrier frequency; Coded signal is through signal generator stimulated emission transducer; The recorder signal is

Figure 2012103230769100001DEST_PATH_IMAGE024

, and signal length is

Figure 2012103230769100001DEST_PATH_IMAGE026

;

(5). the echoed signal that receives

is calculated with

, obtained signal

Figure 2012103230769100001DEST_PATH_IMAGE028

;

Figure 2012103230769100001DEST_PATH_IMAGE030

Figure 2012103230769100001DEST_PATH_IMAGE032

; In the computation process if

Figure 2012103230769100001DEST_PATH_IMAGE034

; Get

Figure 2012103230769100001DEST_PATH_IMAGE036

;

individual point of

representative

waveform,

is increased to

Figure 2012103230769100001DEST_PATH_IMAGE040

from 1;

N is a n point of

Figure 2012103230769100001DEST_PATH_IMAGE042

waveform;

(6) According to

the peak time and amplitude determine the location of defects inside the concrete.

2. the Barker code excitation supersonic detection method of xoncrete structure defective according to claim 1: it is characterized in that: Barker code is N=2, N=3, N=4, N=5, N=7 or N=11.