Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
  • G01N29/36—Detecting the response signal, e.g. electronic circuits specially adapted therefor
  • G01N29/38—Detecting the response signal, e.g. electronic circuits specially adapted therefor by time filtering, e.g. using time gates
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
  • G01N29/04—Analysing solids
  • G01N29/043—Analysing solids in the interior, e.g. by shear waves
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
  • G01N29/36—Detecting the response signal, e.g. electronic circuits specially adapted therefor
  • G01N29/40—Detecting the response signal, e.g. electronic circuits specially adapted therefor by amplitude filtering, e.g. by applying a threshold or by gain control
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
  • G01N29/44—Processing the detected response signal, e.g. electronic circuits specially adapted therefor
  • G01N29/46—Processing the detected response signal, e.g. electronic circuits specially adapted therefor by spectral analysis, e.g. Fourier analysis or wavelet analysis
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
  • G01N29/44—Processing the detected response signal, e.g. electronic circuits specially adapted therefor
  • G01N29/48—Processing the detected response signal, e.g. electronic circuits specially adapted therefor by amplitude comparison
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2291/00—Indexing codes associated with group G01N29/00
  • G01N2291/04—Wave modes and trajectories
  • G01N2291/044—Internal reflections (echoes), e.g. on walls or defects

Definitions

• the invention relates to the field of non-destructive testing and can be used in ultrasonic testing systems, mainly installations for automated ultrasonic testing of sheet and long products and pipes.
• the transducer of an ultrasonic flaw detector emits pulses of high-frequency elastic vibrations into the product.
• the radiation of the probe pulses occurs mainly along the normal to the surface of the controlled products hundreds or even thousands of times per second.
• the receiving transducer hundreds or thousands of times per second receives responses from the product or, as they are also called, “realizations”.
• Each implementation contains signals reflected from rolled surfaces and from defects, as well as pulses due to interference, which in most cases is acoustic or electromagnetic in nature (see the book by J. Krautkremer and G. Krautkremer “Ultrasonic material control. Help”, Moscow , ed. "Metallurgy”, 1991).
• each implementation contains information that allows you to judge the thickness of the controlled product at the location of the ultrasonic transducer, the presence or absence of discontinuities, etc. Interference can distort the information received, cause the wrong decision to be made about the physical and consumer properties of the controlled product,
• Various methods are used to reduce the level of interference, for example, a previously known defective place is preliminarily sounded and the spectrum code of the received signal is recorded in the memory unit, and the control results are judged by comparing this code with the echo spectrum code of the monitored area of the product (SU 1341571).
• pulse normalization of the magnetic state of the material being monitored, as well as coherent is used to reduce the level of interference during the control by an electromagnetic-acoustic converter or incoherent accumulation of implementations.
• Useful signals that are “tied” to the probe pulse and therefore have relatively slowly varying amplitudes and phases from realization to realization, are effectively added up and, as a result, quickly “resolved”.
• the interference, arrival time, the amplitude and phase of which are for the most part random is not so efficiently added up in the drive and, as a result, it “accumulates” much more slowly. Therefore, coherent (as, by the way, incoherent) accumulation in most cases can effectively increase the ratio of useful syral / pomexa.
• Methods SU 1341571, SU 932391, GB 1034724, and in particular the method RU 2123401 do not allow to deal with specific ultrasonic monitoring specific interference, which is partially or fully synchronized with probing pulses and, therefore, with useful signals (often whose spectra coincide with spectra of useful signals). Such interference is very dangerous, since it can cause false alarms and accumulate in the drive, thereby reducing the “good signal / sweep” ratio.
• An example of a source of synchronous interference is a computer controlling a computer complex, which is part of any modern multichannel system of automated ultrasonic monitoring. In many cases, synchronous interference is also fluctuations in the product that are not attenuated due to previous probing pulses or spurious vibrations of scale particles or air bubbles that fall into the working area of the ultrasonic transducer.
• the registration of signals from pulsed ultrasonic flaw detectors involves the use of broadband filters, which is due to the need for selection of defects located fairly close to natural reflectors, which, as a rule, form powerful "bottom" signals.
• a broadband filter provides reception of signals without “falling over” their fronts, which favorably affects the resolution.
• the noise immunity of such a filter in some practical cases may be unsatisfactory.
• Another advantage of a broadband receiver is its ability to provide significantly higher accuracy in determining the distance between the "bottom” pulses. This is extremely important, for example, when performing ultrasonic thickness measurement.
• the present invention eliminates this contradiction.
• the present invention is based on the task of creating an ultrasonic monitoring method with increased noise immunity, which allows monitoring with high resolution time and, as a result, with a maximum reduction in the dead zones of control and maintaining the accuracy of thickness measurement while ensuring high reliability of the control results.
• the objective of the invention is to develop a device that implements such a method.
• the received signal is divided into several time zones, its components located in the waiting areas are separated from the main signal signals reflected from defects, signals from different time zones are subjected to independent processing by supplying signals from n the action of the probe pulse and the expectation of bottom signals on broadband amplifiers, the signals from the waiting areas of signals reflected from defects are filtered to ensure the maximum signal to noise ratio at the output of the corresponding device, the maximum signal amplitude in the waiting areas of signals reflected from the defect is determined, the value of this amplitude is compared with the maximum permissible value and the presence / absence of a defect is judged by the results of this comparison.
• the reliability of determining the presence / absence of defects is evaluated by comparing in the waiting areas of signals reflected from defects, the amplitude of the frequency components characteristic of the spectrum of the probe pulses or the spectrum of the received useful signals, with the amplitude of the frequency components not typical of the spectrum of the probe pulses or the spectrum of the received useful signals.
• the main and auxiliary cycles of accumulation (coherent or incoherent) of the received signals are carried out, and the received signal cleared of synchronized interference is obtained by subtracting the total signals obtained as a result of the main and auxiliary accumulation cycles.
• a device that allows the implementation of the above method includes blocks for receiving ultrasonic oscillation signals, processing and recording them, while this device contains four switching devices, band-pass and notch filters, six peak detectors, a signal delay device, two blocks for measuring signal level ratios, two threshold devices, an addition device and a signal subtraction device.
• the received signals through the first two switching devices are fed to the inputs of the first two peak detectors, as well as through the amplifier and the third switching device to the inputs of the bandpass and notch filters.
• the input of the bandpass filter is connected to the input of the signal delay device and to the input of the third peak detector, and the output of the notch filter is connected to the input of the fourth peak detector.
• the outputs of the third and fourth peak detectors are connected to the inputs of the second block for measuring signal level ratios.
• the output of the third peak detector is connected to the input of the first signal level measuring unit, the second input of which is connected to the output of the first peak detector.
• the outputs of both signal ratio meters through threshold devices are connected to the inputs of the addition device, the output of the latter is connected to the control input of the fourth switching device, the signal input of which is connected to the output of the signal delay device.
• the output of the switching device is connected to the inputs of the first and second drives, the outputs of which are connected to the inputs of the subtracting device.
• the output of the subtractor is connected to the input of the sixth peak detector, and the output of the first drive is connected to the input of the fifth peak detector, the amplitude values of the signals processed and cleared of noise are taken from the outputs of the peak detectors.
• FIG. 1 shows a signal in the absence of interference using a receiver with matched filtering
• FIG. 2 is a view of a received signal in the absence of interference using a broadband receiver
• FIG. 3 is a view of a received signal with a rolled thickness four times reduced using a receiver with matched filtering
• FIG. 4 is a view of a received signal at a rental thickness reduced by four times, using a broadband receiver
• FIG. 5 is a view of a received signal in the presence of interference using a broadband receiver
• FIG. 7 - signal spectrum in the presence of interference
• FIG. 8 is a structural diagram of the proposed device
• FIG. 9 is a generalized transfer characteristic of a band-pass filter
• FIG. 10 is an example of an amplitude-frequency response of a real band-pass filter
• FIG. 11 is a view of a signal cleared of interference
• FIG. 12 is a spectrum of a signal filtered and processed by the device shown in FIG. 8.
• FIG. Figures 1 and 2 show a signal typical of sheet and long products using a receiver with matched filtering (Fig. 1) and using a broadband receiver (Fig. 2).
• Position 1 indicates the probe pulse
• positions 2 and 3 indicate the first and second "bottom" pulses, respectively
• position 4 indicates signals from defects.
• the signals at the output of the broadband receiver have a significantly (sometimes several times) shorter "dead zone".
• the probe pulse 1 is much shorter than that of FIG. 1. Because of this, one of the pulses 4, visible in FIG. 2 is practically indistinguishable in FIG. 1 (the first after the probe pulse).
• Broadband reception provides a wider range of rolled thicknesses that can be controlled. For example, when the thickness is reduced by four times, monitoring using a matched receiver is not possible: pulses 2 and 3 in FIG. 3 almost merge. At the same time, for a broadband receiver (Fig. 4), monitoring will be possible, since the gap between pulses 2 and 3 will be sufficient to register pulses reflected from defects in it.
• the signal received by the broadband receiver is divided into several time zones: A, B, C and D (Fig. 2). Signals from different time zones are subjected independent processing by supplying signals from the areas of operation of the probe pulse and waiting for bottom signals to broadband amplifiers, the signals from the waiting areas of signals reflected from defects are filtered to ensure the maximum signal to noise ratio at the output of the corresponding device, the maximum signal amplitude in the waiting areas of signals is determined reflected from the defect, the value of this amplitude is compared with the maximum permissible value, and the presence / absence of EKTA.
• the signal is cleaned in the waiting areas of pulses reflected from defects, from the noise synchronized with the useful signal, which at the rental can be caused, for example, by undamped oscillations or by the presence of spurious waves excited by piezoelectric or electromagnetic acoustic transducers.
• the main and auxiliary cycles of accumulation of the received signals are carried out, and the received signal cleared of synchronized interference is obtained by subtracting the total signals obtained as a result of the main and auxiliary accumulation cycles.
• the process of accumulation of signals is the memorization of several successive implementations of the signals of the corresponding time zones (zones B and D), and then the mutual time-by-time addition of the signals of the same zones of waiting for defects belonging to different cycles of radiation-reception, followed by normalization of the results of the auxiliary accumulation cycle relative to the results of accumulation of the main cycle .
• FIG. 8 shows a block diagram of a device that allows the above actions to be performed on signals.
• This device contains a broadband amplifier 6; switching devices 7, 8, 9 and 10; peak detectors-meters 11, 12, 13, 14, 15 and 16 maximum amplitude values; band-pass filter 17, which optimally selects the spectrum of the useful signal; notch filter 18, suppressing the useful signal; blocks 19 and 20 performing the operation measuring the ratio of the signal amplitude from the output of block 13 to the amplitudes of the signals from the outputs of block 11 and block 14, respectively; threshold devices 23 and 24; device 25 addition (logical circuit "And"); signal delay device 26; drives 27 and 28 with the number of accumulations, respectively, Nl and N2, while Nl is much less than N2; a subtracting device 29 that subtracts the signal transmitted through the drive 28 from the signal transmitted by the drive 27.
• the diagram indicates: point 5 of the input signal input; point 21 measuring the amplitude of the first "bottom” signal; point 22 measuring the amplitude of the second "bottom” signal; point 30 measuring the amplitude of the useful signal at the output of the first drive 27 for zone B (or D); point 31 measuring the amplitude of the useful signal from zone B (or D), cleared of synchronized interference.
• the informative input signal 5 shown in FIG. 5 (36 indicates the impulse from interference) is supplied to the inputs of the switches 7 and 8 and then to the peak detectors 11 and 12, which measure the amplitude values of the first two “bottom” signals 21 and 22.
• these signals can be used to implement a mirror-shadow and multiple mirror shadow methods for detecting discontinuities.
• the amplitude value of the first “bottom” impulse characterizes, under certain conditions, the amount of energy introduced into the control object (OK). With respect to this value, it is convenient to measure the amplitudes of all other received signals.
• the input signal 5 is fed to the input of the broadband amplifier 6, which is designed to compensate for the decrease in the amplitude of the signals received from zones B and D, which is inevitable with a coordinated (or optimal) filtering.
• the mixture of the useful signal and interference passes through the band-pass and notch filters 17, 18, to the inputs of which it passes through the switch 9.
• the signal spectra in the absence of interference and when exposed are presented, respectively, in FIG. 6 and 7, where 33 denotes the spectrum of the useful signal, and 34 denotes the interference spectrum.
• the frequency response (AFC) of the bandpass filter 17 is shown in FIG. 9 and 10.
• the parameter characterizing the attenuation of the frequency components of the signal lying outside the passband of the filter is denoted by A.sub.d
• the parameter characterizing the unevenness of the amplitude-frequency characteristics (AFC) in the passband of the filter is denoted by Ap .
• the useful signal At the output of the bandpass filter 17, the useful signal already dominates (Figs. 11 and 12), and at the output of the notch filter 18, there is interference.
• the useful signal is sent to a delay device 26, and further, through the switch 10, to the drives 27 and
• FIG. 12 The spectrum of the received signal processed by the device of FIG. 8 is shown in FIG. 12, where 33 denotes the spectrum of the wanted signal in zones B and D after processing; 34 - interference spectrum after processing; position 35 is the amplitude-frequency response of the bandpass filter.
• the switch 10 is used to block inaccurate data, preventing their flow to the drives 27 and 28.
• a sign of data inaccuracy and the possible prevalence of interference in the signal delayed in the device 26 is the excess of the interference amplitude of certain levels measured relative to the amplitude values of the first bottom signal 21 and the signal (mainly useful) generated at the output of the peak detector-meter 13.
• devices 10, 17, 18, 19, 20, 24, 25, 26 serve solely to control the reliability of the data.
• the above blocks can be excluded.
• the amplitude values of the fully processed signal 30 and the same signal after clearing the synchronized interference 31 appear at the outputs of the peak detectors 15 and 16, respectively.
• signals from the “bottom” pulse action zones can also be supplied to the amplifier and the third switching device, where they are then processed similar to that which is performed on the signals from the standby zones defects.
• the device in accordance with the present invention allows to implement protection against interference of the measured useful signals by spectrally processing them in the waiting areas of signals from defects, as well as to suppress signals synchronized with the useful interference signal, which can limit the sensitivity of the control or cause false alarms.
• the device eliminates the dead zones of control due to the presence of "bottom” signals, by applying the procedure for removing synchronized interference to “bottom” signals, which can mask signals from defects lying close to the surface.
• This device to increase the noise immunity of ultrasonic testing can be implemented using well-known electronic devices and components, as well as computer hardware.

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• 2006
  • 2006-12-15 DE DE200611003795 patent/DE112006003795T8/de active Active
  • 2006-12-15 WO PCT/RU2006/000675 patent/WO2008018813A1/ru active Application Filing
  • 2006-12-15 JP JP2009541255A patent/JP5497448B2/ja active Active

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