CN104698089A - Ultrasonic relative time propagation technology suitable for inclined crack quantifying and imaging - Google Patents

Abstract

The invention provides an ultrasonic relative time propagation technology suitable for inclined crack quantifying and imaging, and belongs to the technical field of ultrasonic nondestructive testing. According to the propagation technology, the length, the width, the inclined angle and the position of cracks are set in a two-dimensional section model, a probe with N array elementsis arranged in the model by means of signal parameters of a phased array linear array probe, N2 TXT files representing A scanning signals are formed according to phased array all-capture signal collection, the TXT files are read through software, a TFM image of the cracks is obtained, an upper tip end coordinate point (xR, zR) and a lower tip end coordinate point (xD, zD) on the cracks are found in the image through MATLAB software, and the length delta and the inclined angle gamma of the cracks are calculated. The propagation technology solves the problems that a traditional relative time propagation technology is poor in inclined crack quantifying precision and cannot be used for measuring the inclined angle of the cracks. Besides, by means of the propagation technology, the cracks can be visually imaged and accurately positioned. A solution is provided for further improving quantifying precision of the cracks in workpieces, and good application and popularization prospects are achieved.

Description

A kind ofly be applicable to Incline Crack quantitatively and the ultrasonic relative time communications of imaging

Technical field

The present invention relates to and be a kind ofly applicable to Incline Crack quantitatively and the ultrasonic relative time communications of imaging, solve the problem that traditional relative time communications is difficult to carry out Incline Crack imaging directly perceived and accurate quantification, location, relate to ultrasonic non-destructive inspection techniques field.

Background technology

Crackle is one of the most common in material and structure, harmfulness is maximum defect type.The length of correct judgement crackle, the defect characteristic such as orientation and position, be of great significance the safety evaluatio tool of workpiece.As a kind of supersonic damage-free detection method, tradition relative propagation time technology (relative arrival time technique, RATT) accurate with it, excellent vertical crack quantitation capabilities, is widely applied in defect NDT and NDE field.

But in the traditional RATT crack length mathematic(al) representation as shown in formula (1), hypothesis crackle orientation is perpendicular to examined workpiece bottom surface usually, have ignored the impact of crackle orientation on quantitative result.But in practical work piece crackle orientation not necessarily perpendicular to workpiece bottom, for Incline Crack, in B scan image, the relative position of upper prong and lower prong diffraction echo can change with the change of crackle orientation, and then cause the change of mistiming between two echoes, cause occurring the error of calculation in formula (1), affect the quantitative accuracy of crackle.Although the people such as R.Hoseini have modified the mathematic(al) representation of crack length according to the relative position between upper and lower most advanced and sophisticated diffraction echo, improve the quantitative accuracy of Incline Crack to a certain extent, but, limit by B scanning imagery, the RATT of this improvement still cannot carry out imaging directly perceived to Incline Crack, and quantitative error is relatively high, also cannot the crackle that orientation is parallel to sound wave incident direction (γ=-θ) be carried out quantitatively.

Summary of the invention

The object of the present invention is to provide and be a kind ofly applicable to Incline Crack quantitatively and the ultrasonic relative time communications of imaging, solve the problem that traditional relative time communications is difficult to carry out Incline Crack imaging directly perceived and accurate quantification, location.There is good prospect for promotion and application.

The technical solution used in the present invention is: be a kind ofly applicable to Incline Crack quantitatively and the ultrasonic relative time communications of imaging, comprises the steps:

(1) in the ultrasonic Numerical Simulating Platform of Fdtd Method, set up the two-dimensional section model of examined workpiece, and the length of crackle, width, inclination angle and position are set in a model;

(2) according to the array number of actual phased array linear array probe, array element size, center distance and time domain impulsive signals parameter, arranging an array number is in a model the probe of N;

(3) according to the full signal acquisition collection of phased array, successively array element is excited according to 1 ~ N order, after exciting at every turn, the acoustic reflection signal of crackle is received by whole N number of array element, finally, forms N number of A sweep signal, and be stored in N number of TXT file, like this, after N number of array element successively excites, N is formed altogether ²the individual TXT file representing A sweep signal;

(4) MATLAB software is utilized to read N ²individual TXT file, by the N in file ²individual A sweep signal is kept in FMC matrix H, and utilization carries out image reconstruction based on the program of total focus algorithm to H, obtains the TFM image of crackle;

(5), after obtaining TFM image, MATLAB software is utilized to find out the coordinate points (x of amplitude maximum in the upper and lower most advanced and sophisticated echo of crackle in the picture respectively _r, z _r) and (x _d, z _d);

(6) (x is determined _r, z _r) and (x _d, z _d) after, according to distance between two points formula and 2 two included angle of straight line formula between line segment and normal determined calculate length δ and the tilt angle gamma of crackle, finally realize the quantitative of crackle, meanwhile, utilize the upper and lower coordinate points position of crackle in total focus image to realize the accurate location to crackle.

Effect of the present invention and benefit are: this be applicable to Incline Crack quantitatively and the ultrasonic relative time communications of imaging the length of crackle, width, inclination angle and position are set in two-dimensional section model, according to the signal parameter of actual phased array linear array probe, arranging an array number is in a model the probe of N, according to the full signal acquisition collection of phased array, successively excite array element according to 1 ~ N order, form N altogether ²the individual TXT file representing A sweep signal, utilizes MATLAB software to read N ²individual TXT file, obtains the TFM image of crackle, and the coordinate points (x of amplitude maximum in crackle upper prong echo found out in the picture by recycling MATLAB software _r, z _r) and lower prong echo in the coordinate points (x of amplitude maximum _d, z _d), according to the two included angle of straight line formula between line segment and normal that distance between two points formula and are determined, calculate length δ and the tilt angle gamma of crackle at 2.This communications, solves the problem that traditional relative time communications Incline Crack quantitative accuracy is poor, cannot measure crackle inclination angle.In addition, the technology that the present invention mentions can also carry out imaging directly perceived to crackle, and accurately can locate crackle.There is provided solution for improving the quantitative accuracy of crackle in workpiece further, there is good prospect for promotion and application.

Accompanying drawing explanation

Fig. 1 is quantitative principle (a) scanning process of crackle of traditional relative time communications; (b) mistiming τ _preading.

Fig. 2 is the principle of phased array total focus image imaging.

Fig. 3 is the principle utilizing total focus image counting crack length δ and tilt angle gamma.

Fig. 4 is the schematic diagram of Finite Difference-Time Domain sub-model and crackle.

Fig. 5 is Gauss pulse matching waveform and dominant frequency (a) time domain waveform curve; (b) spectrum curve.

Fig. 6 is total focus image (a) 0 ° of different orientation crackle, (b) 15 °, (c) 30 °, (d) 45 °, (e) 60 °, (f) 75 °.

Fig. 7 is length δ and tilt angle gamma result of calculation (a) 0 ° of different orientation crackle, (b) 15 °, (c) 30 °, (d) 45 °, (e) 60 °, (f) 75 °.

Embodiment

The ultimate principle of tradition RATT as shown in Figure 1.From Fig. 1 (a), be positioned at phased array probe on the left of crackle by suitable delay and focusing rule, make sound wave inject workpiece with incidence angle θ.The shortest sound path that sound wave arrives crackle upper prong and lower prong is represented by line segment AB and line segment CD.Correspondingly, in the B scan image as shown in Fig. 1 (b), the position relationship of crackle upper prong and lower prong diffraction echo is determined by sound path AB and CD.The time of arrival τ corresponding according to maximum amplitude point in upper prong and lower prong diffraction echo _dand τ _r, calculate ultrasound wave arrives the sound path c τ of crackle upper prong and lower prong _r/ 2 and c τ _d/ 2, then utilize the geometric relationship in Fig. 1 (a), calculate to obtain the length δ of crackle by formula (1).

$\mathrm{\δ}=(\mathrm{CD}-\mathrm{AB})\cos \mathrm{\θ}=\frac{c({\mathrm{\τ}}_R-{\mathrm{\τ}}_D)\cos \mathrm{\θ}}{2}=\frac{{\mathrm{c\Δ\τ}}_P\cos \mathrm{\θ}}{2}---\left(1\right)$

Wherein c is the velocity of sound in medium, △ τ _pfor τ _rand τ _ddifference, the mistiming namely between upper and lower most advanced and sophisticated echo.

As a kind of novel phased array supersonic imaging technique, (Full Matrix Capture is caught based on complete matrix, FMC) total focus (Total Focusing Method, the TFM) imaging algorithm of signals collecting obtains increasing concern in recent years.FMC is a kind of ultrasonic signal acquisition technology based on individual reception-transmit phased array probe, and its principle is for 4 array element linear arrays, and 1,2,3, No. 4 array element successively excites ultrasound wave perpendicular to workpiece bottom as transmitting probe according to step 1,2,3,4.In each step, the ultrasonic time-domain signal that single array element is launched, after detecting target, reflected signal is received by all array element, forms 4 A sweep signals, and like this, 4 steps amount to formation 4 ²individual A sweep signal.Be the linear array probe of N for array number, FMC process gathers N altogether ²individual A sweep signal, and be kept in matrix H, be denoted as FMC matrix.Compare the A sweep signal for the synthesis of B scan image, forgiven multiple individual reception-transmitting array element never A sweep signal of arriving of orientation sample in FMC matrix, crack information more comprehensively can be obtained.

Tested discrete region as shown in Figure 2, is first turned to m × n square node point, and each net point is equivalent to a focusing unit by the process of total focus imaging and principle.According to formula (2), calculate and be emitted through net point (x, z) by array element i and the signal propagation time received for array element j.Utilize formula (3) to carry out delay process to this signal, obtain the amplitude of net point (x, z).Utilize circulation on net point (x, z) at all N ²amplitude in individual send-receive combination is sued for peace, and tries to achieve amplitude I (x, z), and utilizes different colors to represent the power of amplitude I (x, z).

$t=\frac{\sqrt{{(x_{\mathrm{tx}}-x)}^2+z^2}+\sqrt{{(x_{\mathrm{rx}}-x)}^2+z^2}}{c_l}---\left(2\right)$

In formula, c _lfor the longitudinal wave velocity of medium, x _txfor launching the position of array element, x _rxfor receiving the position of array element, x is the horizontal ordinate of image, and z is the ordinate of image.

$I(x,z)=\left|\mathrm{\ΣH}\left(\frac{\sqrt{{(x_{\mathrm{tx}}-x)}^2+z^2}+\sqrt{{(x_{\mathrm{rx}}-x)}^2+z^2}}{c_l}\right)\right|---\left(3\right)$

In formula, H (t) is Hilbert conversion, and its effect is that time-domain signal is converted into envelope signal.

After total focus imaging, form high-definition picture as shown in Figure 3.Different from B scan image, TFM image can reduce crackle actual position within the workpiece, and crackle is presented in image intuitively.Further, according to crackle upper prong diffraction echo coordinates (x in image _r, z _r) and lower prong diffraction echo coordinates (x _d, z _d), can calculate the length δ of crackle and the tilt angle gamma of crackle, realize the quantitative of crackle, computing method are as shown in formula (4) and (5).Meanwhile, according to (the x in TFM image _r, z _r) and (x _d, z _d) position, the accurate location to crackle can also be realized.

$\mathrm{\δ}=\sqrt{{(x_R-x_D)}^2+{(z_R-z_D)}^2}---\left(4\right)$

$\mathrm{\γ}=\arctan \left(\frac{x_R-x_D}{z_R-z_D}\right)---\left(5\right)$

A kind ofly be applicable to Incline Crack quantitatively and the ultrasonic relative time communications of imaging, for Incline Crack imaging and accurate crackle quantitatively, location, bury mode-Ⅲ crack for length 5mm in two dimensional model in Finite Difference-Time Domain fractional value platform, comprise step as follows:

(1) entirely catch the process of matrix H for simulation has crackle in the phased array system collection workpiece of independent transmission-reception array element function, in the ultrasonic numerical value platform of Fdtd Method, set up the two-dimensional section model of examined workpiece.As shown in Figure 4, model is of a size of 60 × 25mm ², the material of model is set to carbon steel, and its density is 7900kg/m ³, longitudinal wave velocity is 5900m/s, and transverse wave velocity is 3200m/s.Model lower end is set to solid-vacuum boundary, and all the other positions are set to absorbing boundary.Arrange that width is 0.4mm, length is 5.0mm rectangular channel, with equivalently represented crackle in a model.The central depths of groove is 15mm, and inclination angle is 0 °, 15 °, 30 °, 45 °, 60 °, 75 °, amounts to 6 angles;

(2) with reference to actual, above model, arrange 64 array element phased array linear array probes, array element is of a size of 0.55mm, and array element center distance is 0.6mm.Select Gauss pulse matching waveform as sound source, A sweep waveform is as shown in Fig. 5 (a), and the spectrum signature after FFT is as shown in Fig. 5 (b), known, and its dominant frequency is 5.19MHz.The counting period of model is that 0.078 μ s/ walks, and amounts to calculation 1542 step, adds up to 12 μ s computing time.

(3) according to the definition that the full signal acquisition of phased array gathers, successively array element is excited according to 1 ~ No. 64 order.After exciting, the acoustic reflection signal of crackle is received by whole 64 array elements at every turn.After each array element in phased array array is excited, sound wave, after crackle, is received by 64 array elements whole in array, forms 64 A sweep signals, and be stored in 64 TXT files.Like this, after 64 array elements successively excite, amount to formation 64 ²the individual TXT file representing A sweep signal;

(4) MATLAB software is utilized to read 64 ²individual TXT file, and by 64 in file ²individual A sweep signal is kept in FMC matrix H, and utilization carries out defect image reconstruction based on the MATLAB program of formula (2), (3) to H, obtains total focus image as shown in Figure 6;

(5), after total focus imaging, MATLAB software is utilized to find out the coordinate points (x of the upper and lower most advanced and sophisticated diffraction echo amplitude maximum of crackle in the picture _r, z _r) and (x _d, z _d).And according to (x _r, z _r) and (x _d, z _d) distance between two points formula (4) calculates the length δ of crackle, meanwhile, utilizes (x _r, z _r) and (x _d, z _d) angle of the line segment determined and normal tries to achieve crackle tilt angle gamma;

$\mathrm{\δ}=\sqrt{{(x_R-x_D)}^2+{(z_R-z_D)}^2}---\left(4\right)$

$\mathrm{\γ}=\arctan \left(\frac{x_R-x_D}{z_R-z_D}\right)---\left(5\right)$

(6) through measuring, the upper prong of different orientation Incline Crack and lower prong diffraction echo coordinates coordinate are as shown in Figure 7.According to above-mentioned coordinate, calculate 0 °, 15 °, 30 °, 45 °, 60 °, 75 ° Incline Crack length δ and tilt angle gamma as shown in table 1.Result shows, the error range that crack length δ calculated value is corresponding is 0.01 ~ 0.11mm, and the error range that crackle tilt angle gamma calculated value is corresponding is 0.00 ° ~ 6.11 °, all can meet engineer applied standard.The upper and lower most advanced and sophisticated coordinate points setting value of the crackle recorded in total focus image and ultrasonic measurements as shown in table 2, show to utilize the present invention can realize the accurate location of crackle.

The setting value of table 1 crack length δ and tilt angle gamma and ultrasonic measurements contrast

The setting value of the upper and lower most advanced and sophisticated coordinate of table 2 crackle and ultrasonic measurements contrast

Claims (1)

1. be applicable to Incline Crack quantitatively and a ultrasonic relative time communications for imaging, it is characterized in that: comprise the steps:

(1) in the ultrasonic Numerical Simulating Platform of Fdtd Method, set up the two-dimensional section model of examined workpiece, and the length of crackle, width, inclination angle and position are set in a model;

(2) according to the array number of actual phased array linear array probe, array element size, center distance and time domain impulsive signals parameter, arranging an array number is in a model the probe of N;

(3) according to the full signal acquisition collection of phased array, successively array element is excited according to 1 ~ N order, after exciting at every turn, the acoustic reflection signal of crackle is received by whole N number of array element, finally, forms N number of A sweep signal, and be stored in N number of TXT file, like this, after N number of array element successively excites, N is formed altogether ²the individual TXT file representing A sweep signal;

(4) MATLAB software is utilized to read N ²individual TXT file, by the N in file ²individual A sweep signal is kept in FMC matrix H, and utilization carries out image reconstruction based on the program of total focus algorithm to H, obtains the TFM image of crackle;

(5), after obtaining TFM image, MATLAB software is utilized to find out the coordinate points (x of amplitude maximum in the upper and lower most advanced and sophisticated echo of crackle in the picture respectively _r, z _r) and (x _d, z _d);

(6) (x is determined _r, z _r) and (x _d, z _d) after, according to distance between two points formula $\mathrm{\δ}=\sqrt{{(x_R-x_D)}^2+{(z_R-z_D)}^2}$ And 2 two included angle of straight line formula between line segment and normal determined calculate length δ and the tilt angle gamma of crackle, finally realize the quantitative of crackle, meanwhile, utilize the upper and lower coordinate points position of crackle in total focus image to realize the accurate location to crackle.