CN104062356A - Method and device for overcoming eddy current electromagnetic detection interference signal judging defects - Google Patents
Method and device for overcoming eddy current electromagnetic detection interference signal judging defects Download PDFInfo
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- CN104062356A CN104062356A CN201310094565.6A CN201310094565A CN104062356A CN 104062356 A CN104062356 A CN 104062356A CN 201310094565 A CN201310094565 A CN 201310094565A CN 104062356 A CN104062356 A CN 104062356A
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Abstract
The invention discloses a method and device for overcoming eddy current electromagnetic detection interference signal judging defects. The method comprises the following steps: step 1, filtering small clutter in sine wave amplitude; step 2, after determining a suspected defect, performing interference-removing filtering before outputting; step 3, transmitting treated information to a display by a defect output module, and giving an alarm. The method and device of the invention are high in sensitivity, high in accuracy, wide in application, and capable of detecting metal materials and nonmetal conductors. Since only defect signals are outputted, defect misjudgement due to drift and jitter is avoided.
Description
Technical field
The present invention relates to a kind of nondestructive testing technique field, relate in particular to for overcoming method and the device thereof of eddy current electromagnetic detection undesired signal judgement defect.
Background technology
Along with the continuous development and progress of society, metal material and nonmetallic materials can need to be measured some physical quantity of material before application, performance and structural state etc., and need to detect these material internals in the process of using, whether can produce the crack defect that some people with the naked eye cannot see, EDDY CURRENT is conventional detection method now, the basis that its application " electromagnetics " basic theories detects as conductor, the magnetic field of a conductor being put into this variation produce eddy current, eddy current produces magnetic field, this magnetic field changes along with the variation of alternating current, be that alternating current increases and expands, alternating current reduces and blanking, therefore when conductive surface or when closely surface occurs that the properties of defect or measuring metallic materials changes, the intensity of eddy current and distribution also change, and then can indirectly know whether the existence of internal defects and metallicity variation has occurred.
Yet, in eddy current detection method, because detected workpiece is subject to the impact of self or outside objective factor, as discontinuous in density of material, temperature variation or shake of causing because of mechanical drive etc., capital exerts an influence to eddy current signal, make the detection software that connects eddy current signal occur signal drift and undesired signal problem, thereby cause detecting software and send false alarm, take manual detection to need operator's rich experiences to judge, and judged result is likely erroneous judgement, therefore existing detection software need to improve.
Summary of the invention
It is a kind of for overcoming method and the device thereof of eddy current electromagnetic detection undesired signal judgement defect that technical matters to be solved by this invention is to provide, this method was exported after can directly the data after equipment sampling being entered to process, and only export flaw indication, the defect erroneous judgement of having avoided drift and shake to cause.
For solving the problems of the technologies described above, technical solution of the present invention is: for overcoming the method for eddy current electromagnetic detection signal judgement defect, comprise the following steps:
Step 1: the little clutter in sinusoidal wave wave amplitude is carried out to filtering;
(a) first, a buffer area is set in internal memory, the data after sampling enter and fill buffer area;
(b) secondly, catch any one maximal value or minimum value as extreme value after, then flutter and catch the next extreme value occurring subsequently;
(c) last, the amplitude between two extreme point wave bands (being vertical range) with preset filtering gate value and contrast judgement, the amplitude that is greater than predefined filtering gate value is those suspected defects signal and carries out follow-up judgement;
(d) when continuous amplitude is little-large-little situation, large amplitude wave band is those suspected defects, when continuous amplitude is little-large-large situation, and second large wave band amplitude be greater than current wave band, and second the large wave band of take continues the amplitude of next wave band of judgement as current wave band;
Step 2: determine after those suspected defects, removed interference filter before output;
(a) first, in detecting software, preset an interference coefficient;
(b) secondly, by the amplitude between two extreme points of those suspected defects wave band divided by the data point number between these two extreme points, according to the quotient value drawing, judge, quotient value is less than the interference coefficient setting and is interference, will not export, quotient value is greater than the interference coefficient setting and is defect, the output of reporting to the police;
Step 3: defect output module sends the information after processing display to and reports to the police.
Further, the buffer area described in step 1 (a) at least can be deposited 1 defect.
Further, the extreme value described in step 1 (b) comprises maximum value and minimal value, and to be greater than the value of current point be minimal value to the value of N continuous point, and the value that a N continuous value of putting is less than current point is maximum value.
Further, warning output described in step 2 (b) is to export symmetrical defective waveform by balanced algorithm, and send signal to defect output module and process, described defect output module is driven by defective data, described balanced algorithm processing procedure: the head that first determines defective waveform section, two points of tail, get again head, mean value or intermediate point between 2, tail, can determine an axis of symmetry, when defective waveform is shown as forward waveform, get a upper trough extreme value and the next crest extreme value of defective waveform section, when defective waveform is shown as inverted waveform, get a crest extreme value and a next trough extreme value, can determine starting position and the end position of defect waves.
For overcoming the device of eddy current electromagnetic detection signal judgement defect, comprise: computing unit is processed in pulse signal device, probe, data acquisition circuit and filtering, the output terminal of described pulse signal device is connected with the input end of probe, in described probe, be provided with rectangle drive coil and magnetic test coil, magnetic test coil is arranged at the center of drive coil bottom, the output terminal of probe is connected with the input end of data acquisition circuit, and described data acquisition circuit output terminal is processed computing unit with filtering and is connected.
Further, described pulse signal device sends excitation square-wave signal, and described square-wave signal voltage is 5～10V, frequency 10Hz～100kHz, dutycycle 0.1～0.9.
Further, in described data acquisition circuit, be provided with hardware data capture card.
Adopt after such scheme, the invention has the beneficial effects as follows that sensitivity of the present invention, accuracy are high, be widely used, can detect metal material, nonmetallic materials and conductor, therefore and owing to only exporting flaw indication, can avoid drift and shake and the defect erroneous judgement that causes.
Accompanying drawing explanation
Fig. 1 is that the present invention is for the structural representation of eddy current electromagnetic detection signal defect device;
Fig. 2 is the output spectrum figure that does not adopt filtering of the present invention and go to disturb;
Fig. 3 is the original waveform figure that does not adopt filtering of the present invention and go to disturb;
Fig. 4 adopts the filtered output spectrum figure of the present invention;
Fig. 5 adopts the filtered original waveform figure of the present invention;
Fig. 6 adopts filtering of the present invention and removes the impedance diagram after interference;
Fig. 7 adopts filtering of the present invention and removes the time-base diagram after interference;
Fig. 8 adopts balanced algorithm schematic diagram of the present invention.
Main element symbol description
1, pulse signal device
2, probe 21, drive coil 22, magnetic test coil
3, computing unit 5, measured workpiece are processed in data acquisition circuit 4, filtering.
Embodiment
Below in conjunction with the drawings and specific embodiments, the invention will be further described.
Disclosed is a kind of for overcoming the method for eddy current electromagnetic detection signal judgement defect, as shown in Figure 1, a kind of device for eddy current electromagnetic detection signal judgement defect, comprise: pulse signal device 1, probe 2, data acquisition circuit 3 and filter processing unit 4, the output terminal of pulse signal device 1 is connected with the input end of probe 2, pulse signal device 1 sends field wave signal, square-wave signal voltage is 5～10V, frequency 10Hz～100kHz, dutycycle 0.1～0.9, just profound ripple dutycycle 1:1; In probe 2, be provided with drive coil 21 and 2 magnetic test coils 22, magnetic test coil 22 is arranged at the center of drive coil 21 bottoms, the output terminal of probe 2 is connected with the input end of data acquisition circuit 3, in data acquisition circuit 3, be provided with hardware data capture card, the sample frequency of hardware data capture card is the optimum detection frequency of measured workpiece, and the output terminal of data acquisition circuit 3 is processed computing unit 4 with filtering and is connected.
As shown in Figure 2 and Figure 3; reason due to measured workpiece 5 self; as: density of material, temperature variation, shake etc.; when carrying out EDDY CURRENT, conventionally there will be the situation of the undesired signals such as signal drift, clutter; when employing equipment detects automatically, because the situation of undesired signal can make equipment, occur that erroneous judgement defect reports to the police, and adopt while manually detecting; need to waveform being judged according to operator's rich experiences, also there is certain False Rate in the method.
As shown in Figures 4 to 7, for adopting filtering of the present invention and removing output spectrum figure and the original waveform figure after interference, concrete steps are:
Step 1: the little clutter in sinusoidal wave wave amplitude is carried out to filtering.
(a) first, computer control is set, in the internal memory of computing machine, arranges and at least can deposit the buffer area of 1 defect, the data-signal after equipment sampling enters and fills buffer area;
(b) secondly, flutter catch any one maximal value or minimum value as extreme value after, then flutter and catch the next extreme value occurring subsequently, extreme value comprises maximum value and minimal value, be that the value that the value of N continuous point is greater than current point is minimal value, the value that a N continuous value of putting is less than current point is maximum value.
(c) last, the amplitude between two extreme point wave bands (being vertical range) with preset filtering gate value and contrast judgement, the amplitude that is greater than predefined filtering gate value is those suspected defects signal and carries out follow-up judgement;
(d) when continuous amplitude is little-large-little situation, large amplitude wave band is those suspected defects, when continuous amplitude is little-large-large situation, and second large wave band amplitude be greater than current wave band, and second the large wave band of take continues the amplitude of next wave band of judgement as current wave band;
Step 2: determine after those suspected defects, removed interference filter before output.
(a) first, in detecting software, preset an interference coefficient, the different detection speeds according to different materials, have different interference coefficients, before automatic test, can manually test and find out rational value.
(b) secondly, by the amplitude between two extreme points of those suspected defects wave band divided by the data point number between these two extreme points, according to the quotient value drawing, judge, quotient value is less than the interference coefficient setting and is interference, will not export, quotient value is greater than the interference coefficient setting and is defect, the output of reporting to the police.
Step 3: defect output module sends the information after processing display to and reports to the police.
Above-mentioned warning output is to export symmetrical defective waveform by balanced algorithm, and send signal to defect output module and process, defect output module is driven by defective data, described balanced algorithm processing procedure: the head that first determines defective waveform section, two points of tail, get again head, mean value or intermediate point between 2, tail, can determine an axis of symmetry, when defective waveform is shown as forward waveform, get a upper trough extreme value and the next crest extreme value of defective waveform section, when defective waveform is shown as inverted waveform, get a crest extreme value and a next trough extreme value, can determine starting position and the end position of defect waves.
When probe 2 detects flaw indication (being just profound ripple), after hardware handles, will produce a series of data point, each data point is by X, two data values of Y form, as: P1 (X1, Y1), P 2 (X 2, and Y 2) ... as shown in Figure 6, these points are drawn in two-dimensional coordinate system, will form the figure of an irregular ∞ font, be called impedance diagram, as shown in Figure 7, by X, the line that Y is separately drawn as an one dimension is separately (as X 1, X 2, X 3 ..., Y 1, Y 2, Y 3 ...), top is X, and the line that below is Y is called base line, and the value of X2+Y2 being opened to radical sign acquisition is called amplitude A, uses amplitude data (as A1, A2, A3 ...) also can draw base line, X in practical application, Y-signal is only used for picture impedance diagram, and can not adopt X, Y calculates amplitude, picture value base line, and when probe 2 does not detect flaw indication or undesired signal, base line (X, Y, A) should be a horizontal line, in the time of defectiveness or interference, generation is similar to the waveform of just profound ripple, the feature of flaw indication can be used X, Y, the data of A are carried out defect judgement, when having drift impact, will become oblique line, drift is accumulated to a certain degree and will reaches alarm threshold value, and produces false alarm.
As shown in Figure 8, for adopting the oscillogram of exporting after balanced algorithm of the present invention, after adopting this algorithm, can the genetic defects waveform segment of axis of symmetry will be passed through, by asymmetric transfer of shapes, be that symmetrical waveform segment is exported centered by axis of symmetry, and confirmable reference position and end position of informing testing staff's defective waveform section, the False Rate having occurred while having lowered greatly EDDY CURRENT.
Above embodiment is preferred embodiment of the present invention, used for illustrative purposes only, but not limitation of the present invention, person skilled in the relevant technique, without departing from the spirit and scope of the present invention, can also make various conversion or variation.Therefore, all technical schemes that are equal to also should belong to category of the present invention.
Claims (7)
1. for overcoming a method for eddy current electromagnetic detection undesired signal judgement defect, it is characterized in that: comprise the following steps:
Step 1: the little clutter in sinusoidal wave wave amplitude is carried out to filtering;
(a) first, a buffer area is set in internal memory, the data after sampling enter and fill buffer area;
(b) secondly, catch any one maximal value or minimum value as extreme value after, then flutter and catch the next extreme value occurring subsequently;
(c) last, the amplitude between two extreme point wave bands (being vertical range) with preset filtering gate value and contrast judgement, the amplitude that is greater than predefined filtering gate value is those suspected defects signal and carries out follow-up judgement;
(d) when continuous amplitude is little-large-little situation, large amplitude wave band is those suspected defects, when continuous amplitude is little-large-large situation, and second large wave band amplitude be greater than current wave band, and second the large wave band of take continues the amplitude of next wave band of judgement as current wave band;
Step 2: determine after those suspected defects, removed interference filter before output;
(a) first, in detecting software, preset an interference coefficient;
(b) secondly, by the amplitude between two extreme points of those suspected defects wave band divided by the data point number between these two extreme points, according to the quotient value drawing, judge, quotient value is less than the interference coefficient setting and is interference, will not export, quotient value is greater than the interference coefficient setting and is defect, the output of reporting to the police;
Step 3: defect output module sends the information after processing display to and reports to the police.
2. according to claim 1 a kind of for overcoming the method for eddy current electromagnetic detection undesired signal judgement defect, it is characterized in that: the buffer area described in step 1 (a) at least can be deposited 1 defect.
3. according to claim 1 a kind of for overcoming the method for eddy current electromagnetic detection undesired signal judgement defect, it is characterized in that: the extreme value described in step 1 (b) comprises maximum value and minimal value, be that the value that the value of N continuous point is greater than current point is minimal value, the value that a N continuous value of putting is less than current point is maximum value.
4. according to claim 1 a kind of for overcoming the method for eddy current electromagnetic detection undesired signal judgement defect, it is characterized in that: the warning output described in step 2 (b) is to export symmetrical defective waveform by balanced algorithm, and send signal to defect output module and process, described defect output module is driven by defective data, described balanced algorithm processing procedure: the head that first determines defective waveform section, two points of tail, get again head, mean value or intermediate point between 2, tail, can determine an axis of symmetry, when defective waveform is shown as forward waveform, get a upper trough extreme value and the next crest extreme value of defective waveform section, when defective waveform is shown as inverted waveform, get a crest extreme value and a next trough extreme value, can determine starting position and the end position of defect waves.
5. one kind for overcoming the device of eddy current electromagnetic detection undesired signal judgement defect, it is characterized in that: comprising: computing unit is processed in pulse signal device, probe, data acquisition circuit and filtering, the output terminal of described pulse signal device is connected with the input end of probe, in described probe, be provided with drive coil and magnetic test coil, magnetic test coil is arranged at the center of drive coil bottom, the output terminal of probe is connected with the input end of data acquisition circuit, and described data acquisition circuit output terminal is processed computing unit with filtering and is connected.
6. according to claim 5 a kind of for overcoming the device of eddy current electromagnetic detection undesired signal judgement defect, it is characterized in that: described pulse signal device sends excitation square-wave signal, described square-wave signal voltage is 5～10V, frequency 10Hz～100kHz, dutycycle 0.1～0.9.
7. according to claim 5 a kind of for overcoming the device of eddy current electromagnetic detection undesired signal judgement defect, it is characterized in that: in described data acquisition circuit, be provided with hardware data capture card.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN104296984A (en) * | 2014-10-20 | 2015-01-21 | 国家电网公司 | Mechanical failure detecting method and device for large-scale generator stator winding end |
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| WO2006007826A1 (en) * | 2004-07-19 | 2006-01-26 | Prüftechnik Dieter Busch AG | Method and device for the non-destructive and contactless detection of flaws in a test piece moved relative to a probe |
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| 刘淑娟等: "基于斜率的自适应中值滤波算法", 《计算机应用》 * |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN104296984A (en) * | 2014-10-20 | 2015-01-21 | 国家电网公司 | Mechanical failure detecting method and device for large-scale generator stator winding end |
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