RU2629894C1 - Ultrasound antenna grid - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: ultrasonic antenna array containing ultrasonic transducers installed in the housing with a dry point contact on the working surface of the grate, an individual clamping mechanism with the possibility of reciprocating movement perpendicular to the working surface of the grate and the control circuit. The transducers are arranged in plan along a zigzag line with contact points at its vertices, the vectors of the vibrational displacements of all ultrasonic transducers are oriented transversely or along the longitudinal axis of the antenna array, permanent magnets placed on the working surface of the array are additionally installed, the control circuit is made in the form of an amplifier and a pulse generator for Each converter, a common control unit, a signal processing device, and a communication unit. The output of each pulse generator is connected to the input of the corresponding converter and the input of the corresponding amplifier whose output is connected to the corresponding information input of the signal processing device, the input of the pulse generator is connected to the corresponding output of the control unit, the synchronizing output of which is connected to the input of the signal processing device connected, as well as And a control unit, with a communication unit whose output is an output of the antenna array associated with the processing and display device and formation.

EFFECT: providing the possibility of creating a device with the ability to control products with both small transverse dimensions and products with a double extension.

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Description

The invention relates to the field of ultrasonic non-destructive testing and can be used for defectoscopy of extended products by an echo method with waveguide propagation of ultrasound in them. Such products include, in particular, pipes, rods, rods, rails, corners, sheet and T-bars, etc.

A known equidistant antenna array (AR) containing piezoelectric transducers arranged in a row in a housing is presented in an article by A.K. Gurvich, A.A. Samokrutov, V.G. Shevaldykin “Application of the ultrasonic flaw detector AKP 1224 for monitoring rails using the waveguide method”, XVII Russian Scientific and Technical Conference “Non-Destructive Testing and Diagnostics”, Ekaterinburg, 2005 (copy attached).

This linear AR is poorly adapted to control products with non-planar surfaces, such as pipes or rods, especially of small diameters, because it rests on the surface along the line of ultrasonic transducers, which causes instability of its position. In addition, it contains only a hard-coded electronic switch and a common receiving path with an analog output, which does not allow it to be used to control products with a double length, for example, sheets or pipes of large diameters, when joint spatio-temporal processing of signals from all transducers by an antenna is required lattices in the general device for processing and displaying information according to the synthesized aperture algorithm.

The closest analogue of the invention is an ultrasonic antenna array in the form of a two-dimensional matrix, containing ultrasonic transducers installed in the housing, a switch connected to them, a pulse generator, a measuring unit connected to it and a control unit connected to the control inputs of the switch and the measuring unit connected to the information input with the output of the switch, and the output of the pulse generator is connected to the input of the excitation of the switch, with each of the ultrasonic transducers ying tread providing a point or line contact with the product and with a controlled clamping mechanism with the possibility of reciprocating movement of the ultrasound transducer perpendicularly to the working surface of the array - RU 2080592 C1, 1997 g.

Known equidistant AR has all the disadvantages of the previous analogue.

In accordance with these shortcomings, the technical problem solved by the invention consists in creating a device with the ability to control products with both small transverse dimensions: pipes, rods of small diameter or T-profile, and products with a double length, while the proposed AR should be used with an external device processing and displaying information in the form of a computer or a specialized electronic unit with a screen.

This problem is solved in an ultrasonic antenna array containing ultrasonic transducers installed in the housing with dry point contact on the working surface of the grating, an individual clamping mechanism with the possibility of reciprocating movement perpendicular to the working surface of the grating and a control circuit, the transducers are arranged in plan along a zigzag line with contact points at its vertices, the vectors of vibrational displacements of all ultrasonic transducers are oriented across or along along the single axis of the antenna array, permanent magnets are additionally placed on the working surface of the array, the control circuit is made in the form of a pulse generator and amplifier for each converter and a common control unit, signal processing device and communication unit, while the output of each pulse generator is connected to the input of the corresponding converter and the input of the corresponding amplifier, the output of which is connected to the corresponding information input of the signal processing device, the input of the pulse generator ene to the corresponding output of the control unit, synchronizing the output of which is connected to the input of a signal processing device connected, as well as a control unit, a communication unit, the output of which is the output of the antenna array associated with a processing device and display information.

In particular cases of the device execution, the distances between the contact points of adjacent transducers can be selected from the condition:

where d is the distance between the contact points;

r _a - the spatial correlation interval of the noise of the material of the product in the direction along the lattice;

r _c is the spatial correlation interval of the noise of the product material in the direction transverse to the lattice.

In FIG. 1 and 2 show the construction of the AP in a partially disassembled form to illustrate the installation of the vectors of vibrational displacements of all ultrasonic transducers across the longitudinal axis of the AP (Fig. 1) or along the longitudinal axis of the AP (Fig. 2), in FIG. 3 shows the arrangement of the contact tips of the transducers (point contacts of the transducers) in plan along the zigzag line on the working surface of the AP, in FIG. 4 presents a complete block diagram of the control AR.

In FIG. 1 and 2, the semi-dismantled design of the AR allows you to see its layout, in which the transducers 1 with contact tips 2 (point contacts of the transducers) are installed in the housing 3, where there is also an individual clamping mechanism 4, made, in particular, in the form of a spring with a reciprocating displacement perpendicular to the working surface of 5 AR. The control circuit of each transducer 1 in the form of an amplifier and a pulse generator is located on the corresponding electronic board 6. Inside the transducer 1 contains a piezoelectric element, specifically oriented relative to the board 6. All transducers 1 AR with a dry point contact (CTK) are the same. The bottom of the transducer housing 1 is designed in such a way that the oscillating surface of the piezoelectric element through the material of the bottom and contact tip 2 is mechanically connected to the surface OK in a region much shorter than the wavelength of the ultrasonic waves in the material OK. All free surfaces of the piezoelectric element are covered with damping material.

Permanent magnets 7 are placed on the working surface 5 of the AR, the location of which and the number can be arbitrary depending on the location on the working surface 5 and the material of the magnet 7, which can provide the necessary retention force of the AR on the pipe of the corresponding diameter.

The common control unit 8, the signal processing device 9, and the communication unit 10 shown in FIG. 4 in a block diagram, structurally placed on the boards 11 in the housing 3 of the AP, shown in a semi-disassembled design in FIG. 1 and 2 in the form of upper and lower parts.

The different installation directions of the electronic boards 6 in the converters 1 shown in FIG. 1 and 2 are shown to illustrate the orientation of the vibrational displacement vectors of all ultrasonic transducers across the longitudinal axis AP (FIG. 1) or along the longitudinal axis AP (FIG. 2).

The arrangement of the transducers 1 with the contact tips 2 (point contacts of the transducers) in plan along the zigzag line on the working surface 5 of the AP, shown in FIG. 3 in accordance with the invention, in contrast to the usual equidistant arrangement along a straight line, has two advantages: operational and energy, determined by the signal-to-noise ratio.

The operational advantage is that the AP, installed manually on a pipe of small diameter (about 25-40 mm), does not slide off the pipe, because it does not rely on one line of contact tips (point contacts), but on two lines oriented along the generatrix of the pipe .

The energy advantage of an AR with a zigzag arrangement of converters over a linear one is due to a higher ratio of the resulting (after space-time processing) useful signal to the noise of the pipe metal, which is explained as follows.

Experimental studies have shown that the noise of the metal of the pipe walls is correlated with the sounding signal and, most importantly, its realizations, adopted in a pair of spaced points on the pipe wall, are correlated with each other. The spatial correlation interval of this noise varies depending on the orientation of the receiving points with a constant distance between the points. With the location of the receiving points along the pipe, the interval is approximately 2 times less than with the location of the receiving points across the axis of the pipe. The actual values of the noise correlation intervals for pipes with diameters from 30 to 1420 mm are approximately 10-20 mm for receiving points along the pipe and 20-35 mm for points across the pipe. Moreover, a larger correlation interval corresponds to a larger pipe diameter.

The total aperture of the AR is selected in accordance with the required directional function of the lattice. The step of arranging the converters (d is the distance between the contact points) in the AR is chosen from compromise conditions, based on the interval of spatial noise correlation. On the one hand, for a given aperture, the distance between the contact points (step of the transducers) is desirable to choose as small as possible in order to use many transducers in the array, since their combined effect (after spatio-temporal processing of the signals) will give the highest level of useful signal from defects. However, with a small distance between the contact points shorter than the spatial correlation interval, the noise in the implementations of the received signals from neighboring grating converters will be partially correlated. And the signal-to-noise ratio (as a result of space-time processing) will not be greater than with a larger distance from a smaller number of converters in the AR. Therefore, the distance d between the contact points of the transducers in the lattice should be chosen commensurate with the spatial spatial correlation interval of the noise of the control object (OK).

The best values of the distances d between the contact points (contact tips 2) of the transducers 1 are in the range from a value equal to the correlation interval to a value 40% greater than this interval, in accordance with the formula:

where d is the distance between the contact points;

r _a - the spatial correlation interval of the noise of the material of the product in the direction along the lattice;

r _with - the interval of spatial correlation of the noise of the material of the product in the direction across the lattice.

When the converters 1 in the AR are arranged in two rows with a shift of one row relative to the other half the distance of the converters in a row, it allows, without violating the conditions for optimizing the choice of distance between the contact points, to arrange the rows of converters 1 as close to each other as possible. the distance d between the contact points of the converters in this case is equal to the hypotenuse of the triangle, whose legs are the distance between the rows and half the distance between the converters in the row.

The block diagram of FIG. 4 contains a pulse generator 12 and an amplifier 13 for each converter 1, a common control unit 8, a signal processing device 9 and a communication unit 10 for communication with the information processing and display device 14.

The output of each pulse generator 12 is connected to the input of the corresponding converter 1 and the input of the corresponding amplifier 13, the output of which is connected to the corresponding information input of the signal processing device 9. The input of the pulse generator 12 is connected to the corresponding output of the control unit 8, the synchronizing output of which is connected to the input of the signal processing device 9. The output of the device 9 is connected, like the control unit 8, with a communication unit 10, the output of which is the output of the antenna array associated with the information processing and display device 14.

The pulse generator 12 may be a transistor switch or a push-pull switch, providing pulse generation in the form of a short meander.

As amplifiers 13, operational amplifiers in micro performance are typically used. Amplifiers 13 in the AR are low-noise with a gain of about 20 dB.

The control unit 8 is used to generate triggering pulses for pulse generators 12, synchronization pulses for the signal processing device 9 and for the communication unit 10. The control unit 8 itself begins to work on the initialization signal from the information processing and display device 14 received through the communication unit 10. And further, the control unit 8 synchronizes the entire operation of the AP together with the information processing and display device 14.

The control unit 8 is a microprocessor, for example, executed on a programmable logic integrated circuit (FPGA) XC6SLX25-2FGG484I, with the work program AP installed in it.

The signal processing device 9 produces the main signal amplification from each pre-amplifier 13 AP independently of other signals, and converts the signals into digital form. Those. The signal processing device contains independent amplification and analog-to-digital conversion (ADC) channels. Their number is equal to the number of converters in the AR. In addition, the device 9 has a memory in which the received and amplified signals from the converters 1 are recorded.

Device 9 is built on standard operational amplifiers, ADC chips and memory.

The communication unit 10 is designed to transmit clock signals between the AP and the information processing and display device 14 and to transmit signals recorded in the memory of the AP signal processing device 9 to the information processing and display device 14.

The communication unit 10 is a microcontroller serving digital data buses. It can be performed, for example, on the FPGA XC7Z010-1CLG225I, which contains two core microcontrollers and an Ethernet interface.

The device 14 for processing and displaying information performs the functions of spatio-temporal signal processing, displaying the results of the OK control on the display, and general AR control. The device comprises a processor-based computing device, RAM, image memory, a display, and an operator interface device. As a device for processing and displaying information, a personal computer can be used.

The inventive antenna array (AR) can operate in two modes: in the detection of defects in the walls of pipes with diameters of 20-25 to approximately 250-300 mm when emitting ultrasonic (ultrasound) signals along the pipe and in the detection of defects in the walls of pipes of large diameters ( more than 250 mm) when ultrasound signals are emitted in the direction of the pipe circumference.

In both modes, an echo-pulse control method is used for the waveguide propagation of ultrasonic waves in the pipe walls.

In the first mode, the propagation of ultrasonic waves occurs along the pipe. The entire tube is a one-dimensional waveguide, because no selection of the position of the reflectors around the circumference of the pipe. The only spatial parameter of the detected discontinuity in the pipe is the distance from the AR.

In the second mode, the propagation of ultrasonic waves occurs around the circumference of the pipe on both sides of the AR. In this case, the pipe wall is a two-dimensional waveguide. There are two spatial parameters of the discovered discontinuity in this mode - these are the coordinates along the axes along the pipe and around the circumference.

In these modes, the control result — the A-scan in the first mode and the defectogram (in the form of a reflector topogram) in the second mode — is obtained due to the spatio-temporal processing of the array of received signal implementations from the pipe walls. But the processing algorithms in the device 12 for processing and displaying information are different.

Consider the operation of the device 14 for processing and displaying information in the mode of radiation and reception of ultrasonic signals along the pipe.

For the operation of the AR in this mode, all its transducers 1 are installed so that their vibrational displacement vectors are oriented across the longitudinal axis of the AR (Fig. 1).

The operator manually installs the AP on the pipe surface with the long side along the pipe axis at the inspection site. Magnets 7 hold the grate firmly on the pipe.

When the operator presses a button on the information processing and display device 14, the control signal through the communication unit 10 arrives at the control unit 8, from the outputs of which control signals are sent to the inputs of the pulse generators 12 of each converter 1. When the pulse generator 12 receives a start pulse from its output a short video pulse, for example, of a rectangular or triangular shape or a radio pulse containing 2-4 half-periods of oscillations, but, as a rule, no more than 10 half-periods, is fed to converter 1. The type of the generator signal is selected depending on the state of the OK, i.e. on the degree of attenuation of the ultrasonic waves in its material, and also on how far from the AR it is required to detect defects in the OC.

From the output of the transducer 1, the sounding of the pipe by ultrasonic pulses begins according to the following scheme: the first transducer (from the side of one of the ends of the casing 3 of the grating) emits an ultrasound pulse to the pipe wall, immediately after that it and the other transducers 1 simultaneously receive signals from the pipe surface. After the required interval for receiving signals from the pipe and a pause necessary for attenuation of any vibrations of the pipe walls, the second transducer emits an ultrasonic pulse, and he, as well as all subsequent converters 1, receive signals from the pipe surface. And so on, sensing and receiving signals occur. At the end of this cycle of emission and reception of signals, the last transducer emits a probing signal and receives signals from the pipe surface.

All received signals are digitized and recorded in the memory of the antenna array in the signal processing device 9, and then, through the communication unit 10, are transmitted to the information processing and display device 14.

In the device 14 for processing and displaying information (computer), an array of these signals is processed to obtain a time sequence of echo pulses reflected from various inhomogeneities of the pipe walls (corrosion, cracks, welds, welded pipes, fasteners, etc.) located side of one of the ends of the AR. For this, all received signals are summed with individual time shifts relative to the signal received by the first converter after the probe pulse is emitted by it. Temporary shifts are calculated in advance based on the known ultrasonic propagation velocity along the pipe.

Before the summation, the received signals are shifted in time so that the echo signal from a certain reflector in the pipe wall located at a certain distance from the first transducer of the antenna array, in all received signals would be at the same time. Then all other echo signals from other reflectors will also be coincident in time. After summing all the time-shifted signals, the total implementation is detected and the A-scan of the echo pulses from the reflectors in the tube is displayed on the screen. The horizontal axis of this sweep is calibrated in units of distance from the first transducer AR to any reflector in the pipe.

Thus, the operator receives on the screen a sequence of echo pulses by which one can judge the range to a potential defect. The amplitude of the echo pulse can be used to estimate its size.

If it is necessary to carry out control in another place of the pipe, the operator rearranges the AR in this place and again presses the button in the information processing and display device 14, upon the signal from which the whole process described above again occurs.

The details of the process are as follows.

The AR from the control unit 8 performs the alternate sounding of OK with the reception of ultrasonic signals from the OK and sends through the communication unit 10 the received and digitized implementations (a mixture of noise and useful echo signals) to the information processing and display device 14. The total number of implementations N is equal to:

where n is the number of converters in the antenna array.

In the device 14 for processing and displaying information, all implementations are recorded in memory and their further spatio-temporal processing occurs, the result of which is the A-scan of the echo signals on the screen.

The essence of spatio-temporal processing is to create a directivity function of the AR along the pipe. Since the transducers practically do not have directivity, more precisely, their directivity functions have two wide lobes facing the maxima along the pipe in one or the other direction (the directivity function has the form of a figure eight), as a result of processing the implementations of the received signals, a one-sided directivity of the AR along the pipe is created.

For this, the propagation time of the ultrasonic signal along the pipe by a distance p, which can be called the step of the location of the transducers 1 along the pipe, is preliminarily calculated, and the time can be called the step delay. This distance is equal to half the distance between the closest converters 1 in any row. The step delay t _p at a known speed with the propagation of ultrasonic signals along the pipe is equal to:

Then, almost all N signal implementations (except one, from the combined operation of the first AR converter) are overwritten into the memory of the signal processing device 9 with various time shifts that are multiples of the step delay. In particular, the implementation of converters: the first - second (first emitter - second receiver) is shifted by one step delay. Implementation: first - third - by two step delays, etc. Implementation, for example, the third - sixth - by seven step delays. The shift occurs in the direction of decreasing the delay time of each instantaneous implementation value. Since the implementations are presented in digital form, the necessary number of signal samples is “cut out” from the beginning to shift them.

Then all implementations are summed up term by term and the resulting sequence of samples of the total implementation is written into memory.

Further, in the simplest version, the module of each sample of the total implementation is taken and this sequence of modules is displayed on the screen in the form of an A-scan. Instead of calculating the module, the best result is obtained by calculating the envelope of the total implementation.

Consider the operation of the device 14 for processing and displaying information in the mode of emission and reception of ultrasonic signals across the pipe.

For the operation of the AR in this mode, all its converters 1 are installed so that their vibrational displacement vectors are oriented along the longitudinal axis of the AR (Fig. 2).

The work of the AR on the emission and reception of implementations of signals from the walls of the pipe does not differ from that described above for the first mode of operation. The only difference is in the direction of propagation of the probing signals and the received echo signals.

All received signals are digitized and recorded in the memory of the signal processing device 9, and then transmitted to the information processing and display device 14. In the device 14 (computer), an array of these signals is processed in order to obtain a map of the location in the pipe walls of various heterogeneities of the walls that reflect ultrasonic signals. A map (defectogram) is an image of a scan of the pipe walls in a two-dimensional canvas, on which images of inhomogeneities are displayed in brightness form (or color) on both sides of the AR location zone. Using this defectogram, one can determine the coordinates of the location of inhomogeneities, i.e. their position along the pipe and the position on its circumference.

Converters in the AR have a very wide radiation pattern in the form of a figure eight. Therefore, they emit and are able to receive echo signals in the direction of the circumference of the pipe in a wide range of angles relative to the direction transverse to the pipe. This range of angles is approximately ± 70-80 degrees.

Each signal recorded in the memory of the 9 AR device from each pair of transducers that worked as an emitter and a receiver is a long oscillation sequence containing metal noises and reflected pulses from various inhomogeneities of the pipe walls. These pulses have a duration approximately equal to the duration of the probe pulse, i.e. just two to three periods (typically) of fluctuations. The duration of the entire recorded signal is determined by the maximum range of the reflector, which you want to display on the defectogram. This range is determined by the diameter of the controlled pipe, therefore, the duration is many times longer than the duration of the probe pulse, i.e. 100-300 times.

Each pulse from the inhomogeneity of the pipe wall has a certain delay time relative to the moment of sending the probe signal. This time is equal to the quotient of dividing the distance traveled by the ultrasonic wave from the emitter to the inhomogeneity and then to the receiver, by the wave propagation speed. Therefore, the delay time of the signal from any possible heterogeneity for any pair of AR elements is known (calculated in advance from the given coordinates of the expected heterogeneity and the known ultrasound speed).

The signal processing algorithm for reconstruction of a defectogram is as follows.

The defectogram is reconstructed pointwise. For each image point in the corresponding memory cell, the images are summed up with recording the segments of all signals (from all pairs of converters) of a duration equal to the duration of the probe pulse with delay times equal to the calculated times for the corresponding point of the pipe wall. The resulting sum of these segments is detected (the envelope of this total signal segment is found) and the maximum of the envelope in the form of brightness or color is displayed on the screen at a point corresponding to the coordinates of the visualized point of the pipe wall.

If there are no inhomogeneities in the pipe wall at a certain point of the pipe, then only a certain noise level accumulated from a given point of the wall will be displayed on the screen at the corresponding image point. If there is a heterogeneity, then the sum of the echo signals from it will be much more noise, since a lot of echo signals from this heterogeneity coherently accumulate in the memory cell.

The spatial-temporal processing algorithm for the adopted implementations in this case is as follows.

Let the X axis of the coordinate system be directed along the axis of the pipe, and the Y axis in the perpendicular direction. In this flat case, the pipe wall thickness can be neglected, because the thickness is much less than the length of the ultrasonic wave propagating in the walls of the pipe. Any heterogeneity of the metal, regardless of whether it is surface or internal, equally affects the ultrasound signal, reflecting it back to the AR. Since the pipe diameter, as a rule, is much larger than the ultrasonic wave, the pipe wall can be considered as a plane.

Each point of the reconstructed image displays a value proportional to the reflectivity of the corresponding point on the pipe wall. For this, in the memory cell of the device 14 for processing and displaying information, all echo signals arriving at the AR from this point in the pipe are coherently summed. So, for example, the total echo signal S (x, y) from the point A (x, y) of the pipe wall with coordinates x, y in the general form is the sum of:

where U _{s, r} is the echo signal coming from point A (x, y), selected from the received signal implementation from the emitting transducer with number s and the receiving transducer with number r in the time interval (t _{s, r} , t _{s, r} + τ );

t _{s, r} is the propagation time of ultrasonic vibrations along the path from the radiating transducer with number s to the point A (x, y) and back to the receiving transducer with number r;

τ is the duration of the sample (segment) of the implementation, approximately equal to the duration of the probe signal;

D _s , D _r are the directivity functions of the transducers in the direction from the radiating transducer with number s to the point A (x, y) and in the direction from the receiving transducer with number r to this point, respectively;

n is the number of converters in the AR.

The time t _{s, r} is expressed as follows:

where x _s , y _s and x _r , y _r are the coordinates of the emitting transducer with number s and the receiving transducer with number r, respectively;

C is the speed of propagation of ultrasonic waves in the walls of the pipe.

In the presented device in accordance with the description shows the implementation of the ability to control products with small transverse dimensions: pipes, rods of small diameter or T-profile. In this case, the AR is used with an external device for processing and displaying information in the form of a computer or a specialized electronic unit with a screen.

Claims (6)

1. Ultrasonic antenna array containing ultrasonic transducers installed in the housing with dry point contact on the working surface of the grating, an individual clamping mechanism with the possibility of reciprocating movement perpendicular to the working surface of the grating and a control circuit, characterized in that the transducers are arranged in plan along a zigzag line with points of contact at its vertices, the vectors of vibrational displacements of all ultrasonic transducers are oriented across or l the longitudinal axis of the antenna array, additionally installed permanent magnets located on the working surface of the array, the control circuit is made in the form of an amplifier and a pulse generator for each converter, a common control unit, a signal processing device and a communication unit, while the output of each pulse generator is connected to the input of the corresponding converter and the input of the corresponding amplifier, the output of which is connected to the corresponding information input of the signal processing device, the input is a generator and the pulse is connected to the corresponding output of the control unit, the synchronizing output of which is connected to the input of the signal processing device, connected, like the control unit, to the communication unit, the output of which is the output of the antenna array connected to the information processing and display device. 2. The ultrasonic antenna array according to claim 1, characterized in that the distances between the contact points of adjacent transducers are selected from the condition:

where d is the distance between the contact points; r _a - the spatial correlation interval of the noise of the material of the product in the direction along the lattice; r _with - the interval of spatial correlation of the noise of the material of the product in the direction across the lattice.

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