CN106770669A - Defect two-dimensional appearance imaging detection method based on multi-mode acoustic beam synthetic aperture focusing - Google Patents

Abstract

A kind of defect two-dimensional appearance imaging detection method based on multi-mode acoustic beam synthetic aperture focusing, it belongs to technical field of nondestructive testing.This method uses the phased array ultrasonic detection system of phased array ultrasonic detection instrument, phased array supersonic probe and inclined wedge, electronic scanning function using phased array ultrasonic detection instrument implements signal acquisition to tested test block, and the A for obtaining each aperture of phased array supersonic probe sweeps signal.Encourage acoustic beam in the difference at voussoir Yu test block interface, test block bottom and blemish surface emergence pattern translation type according to each aperture, suitable multi-mode acoustic beam is selected from 8 kinds of acoustic beam propagation patterns.Based on SAFT image-forming principles and Fermat's theorem, the propagation delay of each aperture multi-mode acoustic beam is calculated, and carry out amplitude overlap-add procedure, the SAFT images after being rebuild, so that complete characterization defect two-dimensional appearance feature.This method can realize the correct identification of volume type and area-type defect, and then to defect length, depth and orientation accurate quantification, with engineering application value higher.

Description

Defect two-dimensional appearance imaging detection method based on multi-mode acoustic beam synthetic aperture focusing

Technical field

The present invention relates to a kind of defect two-dimensional appearance imaging detection method based on multi-mode acoustic beam synthetic aperture focusing, its Belong to technical field of nondestructive testing.

Background technology

The qualitative, quantitative of defect, positioning and fixed orientation are the research work that Non-Destructive Testing is paid close attention to all the time.Ultrasonic detecting technology So that its detection sensitivity is high, testing result intuitive display the advantages of and be widely used in defects detection.However, conventional Ultrasound is profit The echo amplitude swept with A in signal carries out defects detection with phase property, it is difficult to determine defect property；Conventional phased array ultrasound skill Art can realize the image checking of defect, but present be only defect pattern Partial Feature, defect property may be caused to judge by accident, There is deviation in quantitative and positioning result, cause the defect extent of injury to be underestimated.

To solve the above problems, domestic and foreign scholars improve image quality using ultrasonic signal and image processing techniques, make every effort to More intuitively, defect characteristic information is comprehensively presented.Such as synthetic aperture focusing technology (Synthetic Aperture Focusing Technique, SAFT) it is to be launched successively using phased array supersonic probe aperture and receive the full array signal of acquisition, with detection The advantages of scope is big, resolving power is high, detection signal-to-noise ratio is high, but still it is unable to complete characterization defect two-dimensional appearance；Using reverse-time migration Imaging can obtain defect pattern and approximate geometry dimension information, but treatment operand is big, and computational efficiency is relatively low, is unfavorable for big chi The defect imaging detection of very little component.

The content of the invention

The present invention provides a kind of defect two-dimensional appearance imaging detection method based on multi-mode acoustic beam synthetic aperture focusing, its Purpose is directed to defect two-dimensional appearance complete characterization difficulty, and Flaw discrimination identification and quantitative result have error, utilize Phased array electronic scanning function simultaneously coordinates A of the inclined wedge collection comprising the multi-modes information such as blemish surface back wave to sweep letter Number, signal is swept to A according to Fermat's theorem and SAFT image-forming principles carries out time delay and amplitude overlap-add procedure, and then acquisition can The SAFT images of complete characterization defect two-dimensional appearance.

The technical solution adopted by the present invention is：Defect two-dimensional appearance imaging inspection based on multi-mode acoustic beam synthetic aperture focusing Survey method, using the detecting system being made up of phased array ultrasonic detection instrument, phased array supersonic probe and inclined wedge, using phased Battle array electronic scanning module implements A and sweeps signal acquisition to tested test block.According to each aperture excitation acoustic beam in voussoir and test block interface, examination Block bottom and the difference of blemish surface emergence pattern translation type, select suitable multi-mode acoustic beam.Based on SAFT image-forming principles And Fermat's theorem, multi-mode acoustic beam is calculated in the refraction point position of voussoir Yu test block interface, signal is swept to A carries out time delay Calculate and amplitude overlap-add procedure, the SAFT images after being rebuild, so that complete characterization defect two-dimensional appearance feature, methods described Using the following steps：

A () phased array ultrasonic detection parameter is selected

Material, shape and size information according to tested test block choose suitable phased array ultrasonic detection parameter, main bag Include phased array supersonic frequency probe, probe aperture and aperture spacing etc.；

B () A sweeps signal acquisition

Based on selected phased array ultrasonic detection parameter, the A for gathering each aperture using phased array electronic scanning function sweeps letter Number, and preserved with txt forms；

C () establishment of coordinate system and image reconstruction area grid are divided

With voussoir tip location as the origin of coordinates, voussoir and tested test block interface are x-axis, and depth direction is y-axis, before voussoir It is positive x-axis along direction, test block depth direction sets up coordinate system for y-axis forward direction, by tested region division into m × n rectangle net Lattice, its grid node is each image reconstruction point；

D () refraction point position solves

The excitation acoustic beam in each aperture of phased array supersonic probe will be in voussoir and test block interface, test block bottom and blemish surface hair Raw reflection/refraction, by taking i-th aperture as an example, its acoustic beam propagation path includes five parts：Sound path S_1iIt is phased array supersonic probe hole Footpath (corresponds to the velocity of sound for c to the distance of voussoir and test block interface first refractive point₁)；Sound path S_2iIt is interface first refractive point and test block (the correspondence velocity of sound is c to the distance of bottom reflection point₂)；Sound path S_3iIt is bottom reflection point and distance (the corresponding velocity of sound of image reconstruction point c₃)；Sound path S_4iFor the distance of image reconstruction point and test block and the refraction point of voussoir second, (the corresponding velocity of sound is c₄)；Sound path S_5iIt is second Distance (correspondence velocity of sound c of the refraction point to receiving aperture₅)；For the propagation sound path S being detected in test block_2i、S_3iAnd S_4i, it is corresponding Acoustic beam pattern can be shear wave or compressional wave, thus have 8 kinds of acoustic beam propagation patterns, be referred to as multi-mode acoustic beam, it is actually detected in Suitable multi-mode acoustic beam is selected according to detection spatial dimension；

Therefore, it is respectively when total sound path and sound：

S(x_0i)=S_1i+S_2i+S_3i+S_4i+S_5i (1)

Wherein x_0iIt is first refractive point abscissa；

Fermat's theorem is met during most short sound, then refraction point x_0iMeet：

E () SAFT image reconstructions are obtained with defect two-dimensional appearance

Each aperture A of reading and saving sweeps signal, according to refraction point coordinates calculate every group excite aperture and image reconstruction point it Between relative time-delay Δ t_i；Based on SAFT image-forming principles, pointwise is swept signal to A and applies to postpone and carry out at amplitude superposition Manage, the composite signal for obtaining each image reconstruction point is：

In formula, I (m, n) is the superposition amplitude of imaging region internal net point (m, n), f_iIt is i-th A of probe aperture acquisition Signal is swept, N is aperture number；

Amplitude normalized and SAFT image reconstructions are carried out to composite signal, you can defect two dimension shape is obtained from image Looks feature；

F () Flaw discrimination is recognized and quantitative determination

Direct basis defect two-dimensional appearance feature in the picture, it is area-type or volume flaw that can qualitatively judge；It is right In volume flaw, the peak coordinate point in defect imaging region is read, its ordinate is defect center depth, using -6dB methods Flaw size can be provided；For area-type defect, the upper and lower coordinate points that defect imaging plots peak declines 6dB are read, two sit Euclidean distance between punctuate is defect length, and ordinate is defect two-end-point depth；According to image reconstruction point row k width Value highest point coordinates (x_k,y_k), the angle of orientation θ of area-type defect can be obtained by formula (5)：

In formula, M is image reconstruction point line number.

The beneficial effects of the invention are as follows：This defect two-dimensional appearance imaging inspection based on multi-mode acoustic beam synthetic aperture focusing Survey method obtains blemish surface reflection echo information using the propagation characteristic of multi-mode acoustic beam, realizes that defect two-dimensional appearance is complete Characterize, be the qualitative recognition of volume type and area-type defect, the accurate quantification of defect length, depth and orientation provides effectively solution Certainly method.Meanwhile, the algorithm that the method is related to can be embedded into defectoscope, realize automatic real time imagery, with engineering higher Using and promotional value.

Brief description of the drawings

The present invention will be further described with example below in conjunction with the accompanying drawings.

Fig. 1 is the ultrasonic testing system schematic diagram that the present invention is used.

Fig. 2 is test block and defect schematic diagram.

Fig. 3 is the coordinate system and acoustic beam propagation path schematic diagram set up when multi-mode acoustic beam is gathered.

Fig. 4 is the conventional SAFT reconstruction images of the Φ 1mm cross-drilled holes of spacing 5mm in test block.

Fig. 5 is the conventional SAFT reconstruction images of length 5mm crackles in test block.

Fig. 6 is the multi-mode acoustic beam SAFT reconstruction images of length 5mm crackles in test block.

Specific embodiment

Defect two-dimensional appearance imaging detection method based on multi-mode acoustic beam synthetic aperture focusing, the ultrasound detection system of use System is as shown in figure 1, including phased array ultrasonic detection instrument, phased array supersonic probe, inclined lucite voussoir.Specific inspection Survey and process step is as follows：

A () tested test block is the carbon steel coupons of thickness 40mm, test block size is 200mm × 200mm × 40mm, is added in test block The length 5mm crackles and depth of work central depths 30mm are respectively the Φ 1mm cross-drilled holes of 27.5mm, 32.5mm, as shown in Figure 2.

B () utilizes M2M phased array ultrasonic detection systems, coordinate voussoir to examine test block using phased array supersonic probe Survey, wherein phased array supersonic probe element number of array is that 32, centre frequency is 5MHz, and aperture, aperture are encouraged as 1 using 2 array elements Size is 10mm × 1.2mm.26 ° of voussoir inclination angle, probe first excite aperture height 8.04mm, sample frequency 100MHz, electricity Sub- scanning stepping 0.6mm.

C () is as shown in figure 3, set up rectangular coordinate system, and detection zone is divided into m × n rectangular mesh.Wherein voussoir Longitudinal wave velocity is 2330m/s, test block transverse wave velocity 3230m/s, longitudinal wave velocity 5700m/s.

D () is the conventional SAFT composite diagram of the Φ 1mm cross-drilled holes with length 5mm crackles of spacing 5mm as shown in Figure 4 and Figure 5 Picture, it can be seen that this two classes defect imaging result is sufficiently close to, it is difficult to correctly distinguish defect type.

E () carries out scanning to test block using phased array electronic scanning function, obtain and include T-T-L (shear waves-horizontal stroke by 31 Ripple-compressional wave, the S in corresponding (1)_2i、S_3iAnd S_4i) acoustic beam propagation pattern A sweep signal composition data set, and with data text This form is derived.

F () is based on Fermat's theorem and SAFT image-forming principles, birefringence point coordinates is solved, and according to formula (4) pointwise to A Sweep signal application time to postpone and carry out amplitude superposition, the SAFT images rebuild.Fig. 6 is the multi-mode of length 5mm crackles Acoustic beam SAFT images, as seen from the figure, defect imaging quality is good, and detection resolving power is higher, and overall pattern obtains complete characterization, can It is area-type defect with the clearly defect.Statistical computation can be obtained, and the quantitative-length result of defect is 6.2mm, central depths positioning It is 29.6mm, shows that party's standard measure and position error are relatively small；To often row pixel is most strong near defect in SAFT images Amplitude position carries out linear fit, and obtaining defect by formula (5) is oriented to 2.3 °, shows that the vertical orientated defect for being most difficult to detection takes surely To accurate.

Claims (1)

1. the defect two-dimensional appearance imaging detection method of multi-mode acoustic beam synthetic aperture focusing is based on, it is characterized in that, using by phase The detecting system that control battle array ultrasound measuring instrument, phased array supersonic probe and inclined wedge are constituted, using phased array electronic scanning module A is implemented to tested test block and sweeps signal acquisition；According to each aperture excitation acoustic beam in voussoir and test block interface, test block bottom and defect table The difference of face emergence pattern translation type, selects suitable multi-mode acoustic beam；Based on SAFT image-forming principles and Fermat's theorem, calculate In the refraction point position of voussoir Yu test block interface, signal is swept to A carries out time delay calculating and amplitude superposition to multi-mode acoustic beam Treatment, the SAFT images after being rebuild, so that complete characterization defect two-dimensional appearance feature, methods described uses the following steps：

A () phased array ultrasonic detection parameter is selected

Material, shape and size information according to tested test block choose suitable phased array ultrasonic detection parameter, mainly including phase Control battle array ultrasonic probe frequency, probe aperture and aperture spacing；

B () A sweeps signal acquisition

Based on selected phased array ultrasonic detection parameter, the A for gathering each aperture using phased array electronic scanning function sweeps signal, and Preserved with txt forms；

C () establishment of coordinate system and image reconstruction area grid are divided

With voussoir tip location as the origin of coordinates, voussoir and tested test block interface are x-axis, and depth direction is y-axis, voussoir forward position side To being x-axis forward direction, test block depth direction sets up coordinate system for y-axis forward direction, by tested region division into m × n rectangular mesh, its Grid node is each image reconstruction point；

D () refraction point position solves

The excitation acoustic beam in each aperture of phased array supersonic probe will occur anti-in voussoir and test block interface, test block bottom and blemish surface Penetrate/reflect, by taking i-th aperture as an example, its acoustic beam propagation path includes five parts：Sound path S_1iFor phased array supersonic probe aperture is arrived The distance of voussoir and test block interface first refractive point, the correspondence velocity of sound is c₁；Sound path S_2iIt is interface first refractive point and test block bottom surface The distance of pip, the correspondence velocity of sound is c₂；Sound path S_3iIt is bottom reflection point and the distance of image reconstruction point, correspondence velocity of sound c₃；Sound Journey S_4iIt is image reconstruction point and the distance of test block and the refraction point of voussoir second, the correspondence velocity of sound is c₄；Sound path S_5iIt is the second refraction point To the distance of receiving aperture, correspondence velocity of sound c₅；For the propagation sound path S being detected in test block_2i、S_3iAnd S_4i, corresponding acoustic beam pattern It is shear wave or compressional wave, thus has 8 kinds of acoustic beam propagation patterns, is referred to as multi-mode acoustic beam, it is actually detected middle according to detection space Scope selects suitable multi-mode acoustic beam；

Therefore, it is respectively when total sound path and sound：

S(x_0i)=S_1i+S_2i+S_3i+S_4i+S_5i (1)

$T\left(x_{0i}\right)=\frac{S_{1i}}{c_1}+\frac{S_{2i}}{c_2}+\frac{S_{3i}}{c_3}+\frac{S_{4i}}{c_4}+\frac{S_{5i}}{c_5}---\left(2\right)$

Wherein x_0iIt is first refractive point abscissa；

Fermat's theorem is met during most short sound, then refraction point x_0iMeet：

$\frac{dT\left(x_{0i}\right)}{{\mathrm{dx}}_{0i}}=0---\left(3\right)$

E () SAFT image reconstructions are obtained with defect two-dimensional appearance

Each aperture A of reading and saving sweeps signal, and calculating every group according to refraction point coordinates excites between aperture and image reconstruction point Relative time-delay Δ t_i；Based on SAFT image-forming principles, pointwise is swept signal to A and applies to postpone and carry out amplitude overlap-add procedure, is obtained Composite signal to each image reconstruction point is：

$I(m,n)=\underset{i=1}{\overset{N}{\Σ}}{f}_i(t_i-{\mathrm{\Δt}}_i)---\left(4\right)$

In formula, I (m, n) is the superposition amplitude of imaging region internal net point (m, n), f_iFor the A of i-th probe aperture acquisition sweeps letter Number, N is aperture number；

Amplitude normalized and SAFT image reconstructions are carried out to composite signal, i.e., defect two-dimensional appearance is obtained from image special Levy；

F () Flaw discrimination is recognized and quantitative determination

Direct basis defect two-dimensional appearance feature in the picture, qualitative judgement is area-type or volume flaw；For volume Type defect, reads the peak coordinate point in defect imaging region, and its ordinate is defect center depth, is to be given using -6dB methods Flaw size；For area-type defect, the upper and lower coordinate points that defect imaging plots peak declines 6dB are read, between two coordinate points Euclidean distance be defect length, ordinate is defect two-end-point depth；According to image reconstruction point row k amplitude peak Coordinate (x_k,y_k), the angle of orientation θ of area-type defect is obtained by formula (5)：

$tan\mathrm{\θ}=\frac{M\underset{k=1}{\overset{M}{\Σ}}{x}_k\·y_k-\underset{k=1}{\overset{M}{\Σ}}{x}_k\·\underset{k=1}{\overset{M}{\Σ}}{y}_k}{M\underset{k=1}{\overset{M}{\Σ}}{x_k}^2-{\left(\underset{k=1}{\overset{M}{\Σ}}{x}_k\right)}^2}---\left(5\right)$

In formula, M is image reconstruction point line number.