CN1521501A - Method of Controlling Acoustic Beam Focus Scanning and Receiving in Phased Array Ultrasonic Testing System - Google Patents

Abstract

The invention provides a total-digital phase control supersonic detection system control sound beam focusing scanning and reception method comprising the steps of, (1) calculating the coordinate value of the each central dot for each vibration unit, (2) determining the vibration set, (3) determining the sound distance time, (4) calculating all the corresponding transmission and reception delay time and time window to all the vibration elements, (5) transmitting and receiving based on all the corresponding transmission and reception delay time. The detecting system using the array type probe has higher operating efficiency and improved detection quality.

Description

Method of Controlling Acoustic Beam Focus Scanning and Receiving in Phased Array Ultrasonic Testing System

technical field

The present invention relates to a method for controlling sound beam synthesis focusing, scanning and echo reception by a fully digital phased array ultrasonic testing system, and in particular to a fully digital phased array ultrasonic testing system for detecting weld seams of natural gas pipelines ( A method for controlling beamforming focusing, scanning, and echo reception as applied in USPA-2000).

Background technique

Ultrasonic instruments currently used for non-destructive testing of materials are mostly composed of a single transducer probe, analog circuit devices for controlling transmission and reception, and a display. During the detection, the manual hand-held probe moves and searches on the workpiece, and the detection result is judged by observing and displaying the echo. This type of instrument has the advantages of convenience, flexibility, economy and practicality. However, inspection technicians are required to have rich experience, and the work efficiency is low, especially in places with heavy workload and high requirements, such as the detection of weld seams in natural gas pipelines. In addition, it is difficult to save the inspection data for a long time for further in-depth analysis and archiving.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for controlling sound beam synthesis focusing, scanning and echo reception by an all-digital phased array ultrasonic detection system.

A method for controlling sound beam focus scanning and receiving by an all-digital phased array ultrasonic testing system, comprising the following steps:

a: Calculate the coordinate value of the center point of each vibration element;

b: Determine the vibration element group;

c: determine the sound path time;

d: Find the corresponding transmission and reception delay time for all the vibration elements in the vibration element group;

e: Each vibration element transmits and receives respectively according to the above-mentioned corresponding transmission and reception delay times;

From the comprehensive consideration of various factors of detection, various special detection systems can be developed by combining the array probe composed of the same small size multi-transducer vibration elements with multiple high-speed digital circuit devices to combine transmission and reception. This array type probe can give full play to the characteristics of small-sized transducer with large divergence angle of sound beam and high receiving conversion coefficient. Without changing the relative position of the probe, the synthetic sound beam can be deflected to a specified angle and focused to a specified detection area by selecting the excitation sequence of the vibration elements and the delay time of the excitation pulse. The scanning function can be realized when a series of focus points and their order are specified.

The detection system using this array probe has the following outstanding advantages:

1. The required focused sound beam and echo reception are controlled by multi-channel high-speed electronic devices. It is not necessary to change the relative position of the probe and the detection area to complete the focused scanning detection of the sound beam in the detection area at high speed. work efficiency.

2. The scanning scheme of the focused acoustic beam and the position of the defect reflection source can be determined digitally, which improves the quality of inspection.

3. Combined with multi-channel high-speed digital circuit transmitting and receiving control devices and upper industrial control machine, it can realize the image display of echo data such as A, B and C ultrasound; establish an echo database for long-term archiving. It provides the possibility to develop an ultrasonic testing system with an intelligent function of testing result evaluation.

Description of drawings

Figure 1 Schematic diagram of the array probe and the position of the detected workpiece.

Figure 2 is a schematic diagram of determining the vibration element group.

Figure 3 is a schematic diagram of calculating the sound path.

Figure 4 is the timing diagram of each vibration element's transmission and reception.

Fig. 5 Schematic diagram of ultrasonic focusing column.

Figure 6 is a schematic diagram of the secondary sound path.

Fig. 7 is a schematic diagram of the three sound paths.

Fig. 8 is a working flow diagram of a specific embodiment of the present invention.

Detailed ways

There are many ways to arrange the vibration elements in the array probe. The present invention is aimed at the line vibration element array in which the vibration elements are lined up along a straight line, as shown in FIG. The vibrators are arranged in a straight line on the probe 2 for shear wave detection. During detection, the plexiglass wedge 1 is placed in contact with the workpiece to be detected.

In the selected coordinate system, the position of the coordinates of the center point of each vibration element on the probe has been determined, and the focus of the desired focus area has been determined. In other words, the sound path of the wave emitted by each vibration element has been determined. Assuming the longest sound path time is T, we can make the waves with longer sound paths in the vibration element group emit first, that is, the corresponding vibration elements are excited first, and the corresponding vibration elements with shorter sound path are excited later, so that the sound path of these waves The sum of time and delay time is equal to T, then the interference effect of each wave can achieve the purpose of focusing the sound beam in a specified area. How to arrange the excitation time of each vibration element raises the problem of calculating the delay time. The basic problem can be summarized as: the geometric coordinates of the focal point are known: (fx, fy) and the refraction angle β of the center line of the sound wave at the interface, the sound speeds C1 and C2 of the longitudinal wave in the wedge and the shear wave in the steel, and the vibrations involved in the emission and reception. The number of elements (even number 2M), now to be determined:

There are at most 2M vibration elements on the probe, which are evenly distributed on both sides of the center line and participate in transmission and reception;

各振元的发射延迟时间，使之组合发射的声束以给定的中心线为中心线，且聚焦在给定的焦点。

The emission delay time of each vibration element makes the sound beam emitted by combination take the given center line as the center line and focus on the given focal point.

各振元的接收延迟时间，供控制接收的数字器件将各振元的接收数据经相位移位到标准时间基后叠加，得到完整回波数据。

The receiving delay time of each vibration element is used to control the receiving digital device to shift the received data of each vibration element to the standard time base and superimpose it to obtain complete echo data.

Consider first the sound path problem, that is, the longitudinal wave emitted by the vibration element group travels in the wedge and is refracted by the interface, and the refracted transverse wave is directly focused on a specified partition of the weld section. The method to solve the above problem is given below:

1. Determine the vibration element group (as shown in Figure 2)

Set the coordinates of the center point of each vibrating element x(1-N), y(1-N), N is the number of vibrating elements on the probe, sorted from left to right.

The steps are as follows:

① Calculate the position of the sound beam centerline on the probe.

Point P coordinates: xp=xf+(D0-yf)tanβ

yp=D0

② Calculate the incident angle α: mu=c1/c2, sinα=mu*sinβ

③i loops from N to 2, and calculates the sinα corresponding to the line connecting the center point of the local oscillator and the next oscillator and point P

sinα0＝(x(i)-xp)/sqrt((x(i)-xp) ² +(y(i)-yp) ² )

sinα1=(x(i-1)-xp)/sqrt((x(i-1)-xp) ² +(y(i-1)-yp) ² )

If (sinα0≥sinα)^(sinα1<sinα), take i and send it to i0, and turn out of the loop, otherwise go to the next step of the loop.

If it is still not found after the cycle is completed, it will display the prompt "Could not find the center vibrating element", and switch out of the program.

If (i0≥M)^(N-i0)≥M, the number of vibration elements in the vibration element group is 2M, from i0-M to i0+M-1;

If i0≥(N-i0), the number of vibration elements in the vibration element group is 2 (N-i0), from 2i0-N+1 to N;

Otherwise, the number of vibrators in the vibrator group is 2i0, from 1 to 2i0.

In this way, the number of vibration elements elnum of the vibration element group and the number of vibration elements elem(1-elnum) can be determined.

2. Calculate the sound path (as shown in Figure 3)

The key to calculating the launch delay time of the vibration element is to find the coordinates of the point Pi, which can be reduced to the following problem: find a point on the straight line y=D0, so that:

sinαi＝mu*sinβi

Let the Pi coordinates be (x, D0), bring the above formula into f(x)=0, the form is:

(xi-x)/sqrt((xi-x) ² +(yi-D0) ² )-mu*(x-xf)/sqrt((x-xf) ² +(D0-yf) ² )＝0

Let xx be the abscissa of the intersection point of the line passing through I(xi, yi) and F(xf, yf) and y=D0:

xx＝xi-(yi-D0)(xi-xf)/(yi-yf)

It can be proved that f(x) is monotonic on [xx, xi], and f(xx)>0, f(xi)<0, f(x)=0 exists on [xx, xi] and there is only one root . Using the Pegasus iterative method to solve f(x)=0, the order of its convergence is 7.275, and no derivative is needed. The algorithm is given below.

Find the zero point of f(x) on [a, b], f(x) satisfies f(a)f(b)<0.

Iterative formula: Xi+1＝Xi-Fi*(Xi-Xi-1)/(Fi-Fi-1)

Start with a, b, namely x0=a, F0=f(a), x1=b, F1=f(b);

If FiFi+1<0, use (Xi, Fi) instead of (Xi-1, Fi-1), (Xi+1, Fi+1) instead of (Xi, Fi)

If FiFi+1>0, use (Xi+1, Fi+1) instead of (Xi, Fi), (Xi-1, vFi-1) instead of (Xi-1, Fi-1)

... where v=Fi/(Fi+Fi+1)

Then iteratively seek Xi+2, and iterate until |Xi-Xi-1|<eps1 or |F|<eps2. eps1 and eps2 are predetermined sufficiently small positive numbers. Calculating f(x) and solving f(x)=0 in the program can design a function process for calling.

Program summary:

Vibrator 1-elnum cycle within the pair of vibrator groups

Take the number of the vibration element, the coordinates of the center of the vibration element xi, yi

Calculate xx

Call the function to solve f(x)=0 to find xpi, and get Pi coordinates (xpi, D0)

Calculate I→Pi, Pi→F two-stage sound path

Calculate the travel time iPi/c1+Pif/c2 (in nanoseconds) and complete the cycle.

3. Calculate the delay time (as shown in Figure 4)

The excitation time of the vibration element with the longest sound path is taken as the time 0 reference, so the timing of each vibration element's transmission and reception is shown in Figure 4:

各振元行程时间与发射延迟时间之和均相等且等于T。设行程时间最长的(即延时时间为0的)振元序号为i0，行程时间为T，则对振元组内各振元有：

The sum of the travel time of each vibration element and the launch delay time is equal to T. Let the serial number of the vibration element with the longest travel time (that is, the delay time is 0) be i0, and the travel time be T, then for each vibration element in the vibration element group:

ts(i)+time(i)=T i=1, 2, ..., n

ts(i) is the delay time of the vibration element

time(i) is the travel time of Zhenyuan

n is the number of vibration elements of the vibration element group participating in the transmission and reception.

The launch delay time of each vibration element is:

ts(i)=T-time(i) i=1, 2, ..., n

最早激发的振元最迟收到回波。

The earliest-fired vibrators are the latest to be echoed.

最迟激发的振元最早收到回波。

The vibrator that fires the latest receives the echo the earliest.

Based on the above time reference, the reception delay time of each vibration element is:

tr(i)=ts(i)+time(i)+time(i)=T+T-ts(i)=2*T-ts(i) i=1, 2, ..., n

关于声束聚焦，实际的超声束不是聚焦于一点，而是聚焦于一柱体内(如图5所示)。设聚焦柱为ab，检测中总是安排聚焦柱覆盖检测区的一个分区。以主声轴为基准，ab距离是柱长，f是几何焦点。超声束进入a后均可能遇到反射源，超声束到达b之前均可能遇到反射源，于是对接收延迟时间作如下修正：

Regarding the beam focusing, the actual ultrasonic beam is not focused on one point, but in a cylinder (as shown in Figure 5). Let the focusing column be ab, and the focusing column is always arranged to cover a partition of the detection area in the detection. Based on the main sound axis, the distance ab is the column length, and f is the geometric focus. After the ultrasonic beam enters a, it may encounter a reflection source, and before the ultrasonic beam reaches b, it may encounter a reflection source, so the receiving delay time is corrected as follows:

tr(i)'=2*T-ts(i)-(travel time from a to b) i=1, 2,...., n

时间窗的含义是超声束进入a后到达b之间

The meaning of the time window is the time between when the ultrasonic beam enters a and arrives at b

t3=2*(travel time from a to b)

In the detection, it is hoped that the focal area of an acoustic beam covers a subregion of the detection area, in other words, the possible reflected echoes in the range from a to b are the objects of our attention. Define twice the travel time from wave a to wave b as the receiving time window. The reception delay time should be from the zero-delay vibration element excitation time to the reflection echo at point a to the vibration element time. Of course, the reception delay time of each vibration element in the vibration element group should be subtracted twice of the travel time from a to f.

For the quadratic sound path problem and the third sound path problem, that is, after refraction and refocusing to a certain partition after the first and second reflections, the equivalent focus coordinates can be obtained first through the law of reflection, and then transformed into a first-order sound path problem deal with. As shown in Figure 6, the situation of the secondary sound path: when the actual focus coordinates are Xf, yf, the equivalent focus coordinates are Xf, -yf. As shown in Fig. 7, the case of three sound paths: when the actual focus coordinates are Xf, yf, the equivalent focus coordinates are Xf, yf-2D0.

In the actual detection process, the object to be detected is often divided into many detection surfaces, and each detection surface is covered by many sound beams. Introduce the concept of detection scheme: a so-called detection scheme is a set of data, and they complete all the control functions of the expected transmission of an ultrasonic beam and echo reception according to the prior agreement. The specific workflow is shown in Figure 8:

First execute step 100: initialize, set known data, mainly include: probe position, steel pipe data, physical parameters, scheme data; wherein scheme data refers to: design a program module specially generating scheme in application software -- scheme generator, It can not only generate conventional detection schemes in batches, but also generate individual detection schemes. The generated schemes can be numbered according to the agreement and stored in the form of files or databases to form a scheme library for the detection and control module to call. The main data of a scheme are: Scheme number; focus point coordinates, field width and field depth of focus area; emission physical parameters: excitation pulse width, amplitude, etc.; participating in emission and vibration element group, refraction angle of sound beam center line; each vibration element in the vibration element group Delay time; receiving delay time and sampling time window value.

Then execute step 101: calculate the coordinate value {(Xi, yi), I=1, . . . , N} of the center point of each vibration element;

Execute step 102: carry out the scheme cycle; Execute step 1021: For a given scheme (sound beam), get the focal point coordinates (fx, fy) and the refraction angle β data of the center line of the sound wave; calculate the incident angle α according to the law of refraction, and then calculate The position of the center line on the probe (Xo, Yo);

Execute step 1022: determine the vibration element group

若(Xo，Yo)二侧振元数均≥M，则二侧各取M个共2M个振元组成振元组。

If the number of vibrators on both sides of (Xo, Yo) is greater than or equal to M, then M vibrators in total are taken from both sides to form a vibrator group.

否则(Xo，Yo)必有一侧振元数＜M，设其个数为m，则取(Xo，Yo)二侧各m个，共2m个振元组成单元组。

Otherwise (Xo, Yo) must have the number of vibration elements on one side < M, let the number be m, then take m on both sides of (Xo, Yo), a total of 2m vibration elements to form a unit group.

Execute step 1023: estimate the constraints, the constraints are:

采用以有机玻璃为楔块的横波探伤钢材时，在β角给定的情况下其对应的α角应满足27.6°＜α＜57.7°的限制条件，使得钢中只有折射横波，无折射纵波。

When using shear wave flaw detection steel with plexiglass as a wedge, the corresponding angle α should satisfy the restriction condition of 27.6°<α<57.7° when the β angle is given, so that there are only refracted shear waves in the steel and no refracted longitudinal waves.

在波源的近场区，由于波的干涉而出现一系列的声压极大极小值，易形成误判或漏判，因此应避免在近场区探伤定量，即声束中心声程应大于近场长度。对相控阵探头而言，需估算振元组的近场长度，形成另一个限制条件。

In the near-field area of the wave source, a series of maximum and minimum sound pressure values appear due to wave interference, which is easy to cause misjudgment or missed judgment. Therefore, quantitative testing in the near-field area should be avoided. near-field length. For phased array probes, it is necessary to estimate the near-field length of the vibrator group, forming another constraint.

在楔块夹角φ较小，振元组振元较靠近楔角处时，由于声波在钢管壁中多次反射衰减而在回波中形成一片树状波。必须调整声程使时间窗落在树状波之后。树状波区对应的声程可通过理论计算或实验确定。

When the wedge angle φ is small and the vibration element of the vibration element group is closer to the wedge angle, a tree-like wave is formed in the echo due to the multiple reflection and attenuation of the sound wave in the steel pipe wall. The sound path must be adjusted so that the time window falls behind the tree wave. The sound path corresponding to the tree-shaped wave region can be determined by theoretical calculation or experiment.

For the above constraint conditions, the intermediate results should be verified in time during the calculation process. When the constraint conditions are not satisfied, parameters such as the position of the vibration element group should be adjusted to obtain better results for use.

Execute step 1024: successively calculate the vibration elements in the vibration element group:

The center coordinates of the vibration element (Xi, Yi)

It is difficult to directly calculate the coordinates of the incident point Ai corresponding to the vibration element, and you can use

Sinαi/sinβI=c1/c2 conditions, list the equations, and then use the numerical method of finding f(X)=0 roots to solve the problem.

在二种质介中的声程和行程时间

Sound path and travel time in two media

Execute step 1025: judge whether the constraints described in step 1023 are satisfied, if not, go to step 1022: adjust the vibration element group.

Execute step 1026: Find the corresponding transmission and reception delay times and reception time windows for all the vibration elements in the vibration element group, and record them in the file.

Execute step 1027: judge whether the scheme has been cycled, and for the next scheme, go to step 102 to perform scheme circulation until all sound beams have been cycled, then execute step 1028: exit.

Through the above steps, the vibration element groups that each sound beam participates in emission and the delay time of each vibration element can be determined.

Claims (10)

1. A method for controlling sound beam focused scanning and receiving by an all-digital phased array ultrasonic detection system, comprising the steps of: a: Calculate the coordinate value of the center point of each vibration element; b: Determine the vibration element group; c: determine the sound path time; d: Find the corresponding transmission and reception delay time and time window for all the vibration elements in the vibration element group; e: Each vibration element transmits and receives respectively according to the above-mentioned corresponding transmission and reception delay times; 2. The method for controlling the focused scanning and receiving of the sound beam by the all-digital phased-array ultrasonic testing system according to claim 1, characterized in that all the data used to control the emission and reception of an ultrasonic beam constitute the testing scheme. 3. The method for controlling the focused scanning and receiving of sound beams by the all-digital phased array ultrasonic detection system according to claim 2, characterized in that, a scheme library is formed from the detection schemes, and the detection schemes in the scheme warehouse are used to detect The program performs loop testing. 4. The method for controlling the focused scanning and receiving of sound beams by an all-digital phased array ultrasonic detection system according to claim 3, wherein the data of the detection scheme includes: scheme number; focus point coordinates, focus area The field width and field depth; the physical parameters of the emission: the excited pulse width, amplitude, etc.; participating in the emission and the vibration element group, the refraction angle of the center line of the sound beam; the delay time of each vibration element in the vibration element group; the reception delay time and sampling time window value. 5. The method for controlling the focused scanning and receiving of the sound beam by the all-digital phased array ultrasonic testing system according to claim 1, characterized in that the sum of the sound path time and the delay time of the waves emitted by each vibration element are equal and equal to the longest sound path time T. 6. The method for controlling the focused scanning and receiving of sound beams by an all-digital phased array ultrasonic testing system according to claim 1, wherein the number of said vibration elements is at most 2M, and said determined vibration element group includes the following step: ① Calculate the position of the sound beam centerline on the probe. ② Calculate the incident angle α. ③i circulates from N to 2, and calculates the sinα corresponding to the line connecting the center point of the local oscillator and the next oscillator and point P. ④ If (sinα0≥sinα)^(sinα1<sinα), take i and send it to i0, and turn out of the cycle, otherwise turn to the next step of the cycle, the number of the vibration element of i0 is described; ⑤If (i0≥M)^(N-i0)≥M, the number of vibration elements in the vibration element group is 2M, from i0-M to i0+M-1; if i0≥(N-i0), then the number of vibration elements in the vibration element group The number of elements is 2(N-i0), from 2i0-N+1 to N; otherwise, the number of elements of the group of elements is 2i0, from 1 to 2i0. 7. The method for controlling the focused scanning and receiving of the sound beam by the all-digital phased-array ultrasonic testing system according to claim 1, characterized in that, the delay time of each vibration element emission is: ts(i)=T-time(i) i=1, 2, ..., n The receiving delay time of each vibration element is: tr(i)=ts(i)+time(i)+time(i)=T+T-ts(i)=2*T-ts(i) i=1,2,...,n The ts(i) is the delay time of the vibration element, time(i) is the travel time of the vibration element, and n is the number of vibration elements of the vibration element group participating in the transmission and reception. 8. The method for controlling the focused scanning and receiving of sound beams by an all-digital phased array ultrasonic testing system according to claim 1, characterized in that the ultrasonic beams emitted by each vibration element are not focused on one point, but focused on In a cylinder, set the focusing cylinder as ab, take the main acoustic axis as the reference, the distance from ab is the length of the column, f is the geometric focal point, and the receiving delay time is: tr(i)'=2*T-ts(i)-(travel time from a to b) i=1, 2,...., n 9. The method for controlling acoustic beam focus scanning and receiving by an all-digital phased array ultrasonic testing system according to claim 1, characterized in that, between step c and step d, further includes step f: estimating constraint conditions, if If the constraints are not satisfied, the vibration element group is adjusted. 10. The method for controlling the focused scanning and receiving of sound beams by the all-digital phased array ultrasonic testing system according to claim 1, characterized in that the constraints are: ①In the case of a given β angle and a plexiglass wedge, the corresponding α angle should meet the constraint condition of 27.6°<α<57.7°, and the β angle is the refraction angle of the center line of the sound wave at the interface. ②The sound path at the center of the sound beam should be greater than the near-field length. For phased array probes, the near-field length of the vibrator group needs to be estimated. ③The sound path must be adjusted so that the time window falls behind the tree wave.

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