CN108344798B - Double-frequency excitation circular eddy current probe and method for detecting thick-wall deep crack defects - Google Patents
Double-frequency excitation circular eddy current probe and method for detecting thick-wall deep crack defects Download PDFInfo
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Abstract
The invention belongs to the technical field of nondestructive testing, and relates to a double-frequency excitation circular eddy current probe and a method for detecting thick-wall deep crack defects. The invention discloses a double-frequency excitation circular eddy current probe, which comprises a double-frequency excitation probe assembly, a detection probe assembly and a fixing frame; the excitation probe assemblies are in two groups and are distributed in bilateral symmetry with the detection probe assemblies as the center; the excitation probe assembly consists of an excitation coil and an excitation coil mounting upright post; the detection probe assembly consists of a detection coil and a detection coil mounting upright post; the fixing frame consists of a stand column fixing plate and a scanning component connecting piece which are fixedly connected; the bottom ends of the exciting coil mounting stand columns and the detection coil mounting stand columns are arranged on a stand column fixing plate; the exciting coil is a circular eddy current coil and is excited by sinusoidal double-frequency alternating current. The dual-frequency excitation probe can improve the penetration depth of eddy current and the detection capability of the probe on deep cracks, and the penetration depth can reach about 21 mm.
Description
Technical Field
The invention belongs to the technical field of nondestructive testing, relates to an eddy current probe for industrial detection of defects, and particularly relates to a double-frequency excitation circular eddy current probe and method for detecting thick-wall deep-crack defects.
Background
The eddy current detection is one of conventional nondestructive detection technology, and is an electromagnetic detection method for detecting defects and testing performance of materials and components according to electromagnetic performance changes of the materials based on an electromagnetic induction principle, wherein the basic principle is based on the theory of electromagnetism. The eddy current detection method has the advantages of non-contact, high detection speed and shallow crack quantification, and is an effective method for quantitatively and nondestructively evaluating structural surface and near-surface defects. The eddy current online detection technology is widely applied to manufacturing of large-scale, heavy-duty and special equipment and aerospace key parts in industry, so that the crack detection technology is important to guaranteeing equipment operation safety, assessing equipment service life, reducing equipment maintenance cost and the like.
At present, conventional eddy current detection adopts an eddy current probe with single frequency to detect defects which basically stay near the surface layer, and the identification capability of deeper defects and deep defects in equipment parts is limited because of obvious skin effect. Although the detection effect on deep cracks can be improved to a certain extent by means of measures such as optimizing the structural parameters of the probe, reducing the excitation frequency and the like, other problems exist at the same time: if low-frequency excitation is adopted, although the penetration depth of eddy current can be increased, and the capability of the probe for detecting deep defects can be improved, the problems of low probe resolution, low signal to noise ratio, low detection speed and signal amplitude, and the like caused by the speed effect of the probe and the difficulty in resolution of detection signals can be caused. Even though sensitivity can be improved by adopting a manner of an interferometer (SQUID), a giant magneto resistance sensor (GMR), a magneto-sensitive element such as a hall element, a magnetic circuit shield, and the like, the problem of too low detection speed is not solved well all the time, and thus cannot be applied to a large-area high-speed detection occasion.
Therefore, the research is suitable for the eddy current detection probe for high-speed detection of large-area thick-wall deep-crack defects, and has important significance and prospect in the aspects of ensuring the safe operation of equipment, evaluating the service life of the equipment, reducing the maintenance cost of the equipment and the like.
Disclosure of Invention
In order to overcome the defects of the prior art and solve the problems in the prior art, the invention aims to provide the double-frequency excitation circular vortex probe for detecting the thick-wall deep crack defects and the detection method thereof, and the two excitation coils with different frequencies are used for simultaneously and reversely exciting to generate a composite vortex field in a test piece material, so that the purposes of changing the distribution state of the vortex field in the material and increasing the penetration depth are achieved. Compared with the prior art of single frequency (low-frequency excitation), magnetic sensors and the like, the invention can effectively solve the problems of low probe resolution, low sensitivity, low detection speed, difficult detection signal resolution and the like, can be used for large-scale high-speed detection of deep crack defects of thick-wall components, and provides accurate and reliable judgment basis for detection and evaluation of deep crack defects of thick walls in industrial practice.
The technical scheme adopted by the invention is as follows: a dual-frequency excitation circular eddy current probe for detecting thick-wall deep crack defects is characterized in that: the device comprises an excitation probe assembly, a detection probe assembly and a fixing frame; the excitation probe assemblies are in two groups and are distributed in bilateral symmetry with the detection probe assemblies as the center; each group of excitation probe components consists of 1 excitation coil and 1 corresponding excitation coil mounting upright post, and the excitation coils are sleeved on the excitation coil mounting upright posts; the detection probe assembly consists of a detection coil and a detection coil mounting upright post, and the detection coil is sleeved on the detection coil mounting upright post; the fixing frame consists of a stand column fixing plate and a scanning component connecting piece, and the stand column fixing plate is fixedly connected with the scanning component connecting piece; the bottom ends of the exciting coil mounting stand columns and the detection coil mounting stand columns are arranged on a stand column fixing plate; the upright post fixing plate is fixedly connected with the scanning component connecting piece.
Further, the double-frequency excitation circular eddy current probe is detachably mounted with the scanning component through the scanning component connecting piece.
Further, the exciting coil is a circular eddy current coil and is excited by sinusoidal double-frequency alternating current.
Further, the detection probe assembly is provided with a group which consists of 1 detection coil and 1 corresponding detection coil mounting upright post.
Further, the detection coil is a circular eddy current coil.
Further, the diameters of the exciting coils and the corresponding exciting coil mounting posts are respectively larger than those of the detecting coils and the corresponding detecting coil mounting posts.
Further, the exciting coil is completely sleeved on the exciting coil mounting upright post, and the top end surface of the exciting coil is kept in the same plane with the top end surface of the exciting coil mounting upright post so as to keep the fixed relative position relation of the exciting coil in the detection process.
Further, the detection coil is completely sleeved on the detection coil mounting upright post, and the top end face of the detection coil is kept in the same plane with the top end face of the detection coil mounting upright post so as to keep the fixed relative position relation of the detection coil in the detection process.
Furthermore, the scanning component connecting piece is a connecting plate, and the connecting plate is provided with a mounting hole for integrally mounting the double-frequency excitation circular eddy current probe on the scanning component.
Preferably, the plurality of mounting holes are symmetrically distributed on the scanning component connecting piece.
Further, the exciting coil mounting stand column, the detecting coil mounting stand column and the fixing frame are all made of PVC materials.
Further, the exciting coil and the detecting coil are wound by enamelled wires.
Based on the scheme, the invention adopts another technical scheme that: the method for detecting the thick-wall deep crack defect by using the double-frequency excitation circular eddy current probe is characterized by comprising the following steps of:
s1, continuously introducing steady-state sinusoidal excitation currents with different frequencies and sizes into two groups of excitation coils through a synchronous alternating-current power supply, wherein the sinusoidal excitation currents generate a vortex field in a metal flat test piece;
s2, C scanning is carried out on the surface of the test piece by the detection probe assembly through the scanning control console, the vortex field at the defect is disturbed by the defect, and defect information is fed back to the detection coil through the disturbance magnetic field;
s3, inputting a detection signal in the detection coil into a filter, filtering the detection signal by using the filter to remove high-frequency noise, and outputting the high-frequency noise to an oscilloscope;
s4, inputting the detection signal filtered to remove the high-frequency noise into an amplifier, and amplifying the weak detection signal through the amplifier;
and S5, displaying the defect signal of the test piece on an oscilloscope in real time, finding out the defect, and calculating the actual depth of the defect through a calibration curve of a standard test piece.
Further, a gap distance s= (1.4-2) ×r between the two groups of excitation coils o ，R o Is the outer radius of the excitation coil; the gap distance between the exciting coils plays an important role in the overall size of the probe and the detection performance of the probe, directly influences the detection result of deep cracks, and can effectively improve the crack detection of the probe by keeping a proper distanceThe depth is detected. The invention preferably adopts two larger circular eddy current coils as excitation elements, one smaller circular eddy current coil is used as a detection signal acquisition element, the detection coil is positioned at the midpoint of the central connecting line of the two circular excitation coils, and the analysis test proves that the space between the two circular excitation coils is S= (1.4-2) x R o With this distance range, detection of depth defects can be achieved.
Further, in the two groups of exciting coils, the exciting coil on the higher frequency side is matched with smaller exciting current, the exciting coil on the lower frequency side is matched with larger exciting current, and the current in each exciting coil is kept to be 0.5-0.7 times of the exciting frequency fed into the exciting coil. The configuration of the probe mainly includes the configuration of the excitation current magnitude and the excitation frequency in the excitation coils, the configuration of the gap between the excitation coils, and the like. The distribution of the excitation current levels in the two excitation coils directly influences the level of the eddy current depth. The density of eddy current generated by exciting coil current on the surface of the test piece is limited by two factors, namely exciting frequency and exciting current. The eddy current density generated on the surface of the test piece by different excitation frequencies and different excitation currents is different, and the skin effect on the surface of the test piece can be effectively reduced by adjusting the excitation frequencies and the excitation current proportion at the same time to enable the excitation frequencies and the excitation current proportion to reach proper values. The high current can generate larger eddy current density, the excitation coil at the higher frequency is matched with smaller excitation current, and the excitation coil at the lower frequency is matched with larger excitation current.
The principle of the invention is as follows:
firstly, continuously introducing steady-state sinusoidal excitation currents with different frequencies and sizes into two groups of excitation coils, wherein the sinusoidal excitation currents can generate alternating magnetic fields on the surface and the inside of a test piece, alternating eddy currents can be induced in the test piece and the surface of the test piece by the changed magnetic fields, the eddy currents can be disturbed by defects in the test piece, a secondary magnetic field induced by the eddy currents and detection signals can be picked up by a circular detection line circle, and whether the current position has defects or not is judged by processing the detection signals and comparing the detection signals with detection signals of a defect-free test piece; if the defect exists, the actual depth of the defect can be deduced by continuing to pass through the calibration curve of the standard test piece.
The invention has the beneficial effects that:
1. the invention adopts the circular eddy current coil insensitive to the direction as the excitation and detection element, and solves the problems that the eddy current generated by the rectangular excitation coil is sensitive to the crack direction and the crack defect parallel to the eddy current flow direction is not easy to detect in the actual detection process, thereby effectively avoiding the occurrence of crack omission detection.
2. The double-coil excitation probe adopts a sine double-frequency alternating current excitation mode, attenuation degrees of eddy currents generated by different frequencies in a test piece are different, and by setting proper excitation parameters, opposite eddy currents which can be mutually offset are generated at a certain point on the surface of the tested piece, so that the density of the eddy currents in the surface of the test piece is weakened, the density of the eddy currents in the deep part of the material is relatively increased, the detection signal of deep cracks is relatively increased, the signal-to-noise ratio of the detection signal is increased, the influence of the eddy current skin effect on the surface of the test piece on deep crack defect detection is effectively reduced, the penetration depth of the eddy currents and the detection capability of the probe on the deep cracks are improved, and the penetration depth of the double-frequency excitation probe can reach more than 1.6 times when single-frequency excitation is performed on the basis of the density of the surface eddy currents.
3. The gap distance S between the double excitation coils is closely related to the size of the probe and the detection performance of the probe, the gap distance S directly influences the detection result of deep cracks, and the detection depth of the probe on the cracks can be effectively improved by keeping a proper distance. Experiments show that the gap distance of the double probes is set as S= (1.4-2) x R in the invention o The depth of the detectable crack defect can reach about 21 mm.
4. The double-frequency excitation circular eddy current probe has high detection efficiency, and can avoid the problems of low resolution, reduced sensitivity, low detection speed and the like of the probe.
5. The double-frequency excitation circular eddy current probe solves the following problems in the prior art: the problem that the eddy current skin effect on the surface of the test piece influences the deep crack defect detection; the problem that the internal defect cannot be detected due to the fact that the internal detection signal of the test piece is too small; the eddy penetration depth is small, and the eddy probe has low capability of detecting deep cracks.
Drawings
FIG. 1 is an assembly view of a dual frequency excitation probe;
FIG. 2 is a schematic diagram of a dual frequency excitation probe detection scheme;
FIG. 3 is a graph showing the eddy current density change curve of the dual-frequency excitation probe at the combination of two excitation frequencies of 5kHz and 20 kHz;
FIG. 4 is a graph showing the eddy current density change curve of a single-frequency excitation probe when two excitation frequencies of 5kHz and 20kHz are excited respectively;
FIG. 5 is a graph showing the eddy current density change curve of the dual-frequency excitation probe at the combination of two excitation frequencies of 30kHz and 80 kHz;
FIG. 6 is a graph showing the variation of eddy current density of a single frequency excitation probe when the probe is excited at two excitation frequencies of 30kHz and 80kHz respectively.
Parts, parts and numbers in the figures: 1-is an exciting coil; 2-mounting an upright post for the exciting coil; 3-is a detection coil; 4-mounting an upright post for the detection coil; 5-is a column fixing plate; 6-is a scanning component connector; 7-is a connecting plate; 8-mounting holes; 9-is a current source; 10-is a filter; 11-is an amplifier; 12-is an oscilloscope; 13-is a test piece; 14-is a scan path; 15-is a crack.
Detailed Description
The following describes the technical scheme of the present invention in detail with reference to the accompanying drawings, but the content of the present invention is not limited thereto.
Example 1:
as shown in fig. 1, a dual-frequency excitation circular eddy current probe for detecting thick-wall deep crack defects is characterized in that: the device comprises an excitation probe assembly, a detection probe assembly and a fixing frame; the excitation probe assemblies are in two groups and are distributed in bilateral symmetry with the detection probe assemblies as the center; each group of excitation probe components consists of 1 excitation coil 1 and 1 corresponding excitation coil mounting upright post 2, and the excitation coils 1 are sleeved on the excitation coil mounting upright posts 2; the detection probe assembly consists of a detection coil 3 and a detection coil mounting upright post 4, wherein the detection coil 3 is sleeved on the detection coil mounting upright post 4; the fixing frame consists of a vertical column fixing plate 5 and a scanning component connecting piece 6, and the vertical column fixing plate 5 is fixedly connected with the scanning component connecting piece 6; the bottom ends of the exciting coil mounting stand columns 2 and the bottom ends of the detecting coil mounting stand columns 4 are mounted on the stand column fixing plates 5.
The whole double-frequency excitation circular eddy current probe is detachably mounted with the scanning component through the scanning component connecting piece 6.
The detection probe assembly is provided with a group which consists of 1 detection coil 3 and 1 corresponding detection coil mounting upright post 4.
The exciting coil 1 and the detecting coil 3 are circular eddy current coils.
The diameters of the exciting coil 1 and the corresponding exciting coil mounting upright post 2 are respectively larger than the diameters of the detecting coil 3 and the corresponding detecting coil mounting upright post 4.
The exciting coil 1 is excited by sinusoidal double-frequency alternating current.
The exciting coil 1 is completely sleeved on the exciting coil mounting upright post 2, and the top end surface of the exciting coil is kept in the same plane with the top end surface of the exciting coil mounting upright post 2 so as to keep the fixed relative position relation of the exciting coil 1 in the detection process;
the detection coil 3 is completely sleeved on the detection coil mounting upright post 4, and the top end surface of the detection coil is kept in the same plane with the top end surface of the detection coil mounting upright post 4 so as to keep the fixed relative position relation of the detection coil 3 in the detection process.
The scanning component connecting piece 6 is a connecting plate 7, and a mounting hole 8 is formed in the connecting plate 7 and used for integrally mounting the double-frequency excitation circular eddy current probe on the scanning component.
The number of the mounting holes 8 is 2, and the mounting holes are symmetrically distributed on the left side and the right side of the connecting plate 7.
The exciting coil mounting stand column 2, the detecting coil mounting stand column 4 and the fixing frame are all made of PVC materials.
The exciting coil 1 and the detecting coil 3 are wound by enamelled wires.
Gap distance s= (1.4-2) ×r between the two groups of excitation coils 1 o ，R o For exciting the outer radius of the coil.
Of the two groups of exciting coils 1, the exciting coil 1 on the higher frequency side is matched with smaller exciting current, the exciting coil 1 on the lower frequency side is matched with larger exciting current, and the current in each exciting coil 1 is kept to be 0.5-0.7 times of the exciting frequency fed into the exciting coil.
An assembly drawing of the dual frequency excitation probe assembly obtained from example 1 is shown in fig. 1.
Example 2:
as shown in fig. 2, based on embodiment 1, a method for detecting a thick-wall deep crack defect by using a dual-frequency excitation circular eddy current probe is characterized in that: the method comprises the following steps:
s1, continuously introducing steady-state sinusoidal excitation currents with different frequencies and sizes into two groups of excitation coils 1 through a synchronous alternating-current power supply 9, wherein the sinusoidal excitation currents generate a vortex field in a metal flat test piece 13;
s2, C scanning is carried out on the surface of the test piece 13 by the detection probe assembly through the scanning control console, a vortex field at a defect is disturbed by the defect, and defect information is fed back to the detection coil 3 through the disturbance magnetic field;
s3, inputting a detection signal in the detection coil 3 into a filter 10, and filtering high-frequency noise in the detection signal by using the filter 10;
s4, inputting the detection signal filtered to remove high-frequency noise into an amplifier 11, amplifying the weak detection signal through the amplifier 11, and outputting the weak detection signal to an oscilloscope 12;
and S5, displaying the defect signal of the test piece 13 on the oscilloscope 12 in real time, finding out the defect, and calculating the actual depth of the defect through finite element analysis by utilizing ansys software through a calibration curve of a standard test piece.
Example 3:
in order to verify that the penetration depth of the double-frequency excitation circular eddy current probe for detecting the thick-wall deep crack defect is superior to that of a corresponding single-frequency excitation probe, on the basis of the embodiment 2, the penetration depth comparison experiment of the single-frequency excitation eddy current probe and the double-frequency excitation eddy current probe is carried out by using two excitation frequencies of 5kHz and 20 kHz.
1. When the double-frequency excitation circular eddy current detection probe is adopted for experiments, 5kHz and 1.3A current is input into the excitation coil 1 positioned at the left side of the detection coil 3, and 20kHz and 0.7A current is input into the excitation coil 1 positioned at the right side of the detection coil 3; the configuration parameters, the detection method and the results of the double-frequency excitation eddy current probe are as follows:
1) Configuration parameters
(1) Two sets of excitation coils 1 basic dimensions: outer radius R o 12mm, inner radius R i Height h=6 mm;
(2) the excitation frequencies of the two groups of excitation coils 1 are respectively:f left =5 kHz and f right =20kHz
(3) The excitation current in the two groups of excitation coils 1 is respectively as follows:I left =1.3a and I right =0.7A
(4) Distance between two sets of excitation coils 1:S=16mm
2) The detection method comprises the following steps:
as shown in fig. 2, the detection was performed according to the method in example 2;
3) Detection result:
from the eddy current density change curve of the dual-frequency excitation circular eddy current probe obtained in the embodiment 3 at the combination of the excitation frequencies of 5kHz and 20kHz, as shown in fig. 3, the graph in fig. 3 can calculate that the penetration depth can reach 21.28mm when the excitation frequencies of 5kHz and 20kHz are combined.
2. On the basis of examples 1 and 2, only one set of excitation coils 1 was installed, and experiments were performed using a single frequency excitation eddy current probe. When a single-frequency excitation circular eddy current detection probe is adopted for experiments, 5kHz and 0.7A current and 20kHz and 0.7A current are sequentially input into an excitation coil 1; the basic size of the exciting coil 1, the detection method and the result are as follows:
1) Basic dimensions of the excitation coil 1: outer radius R o 12mm, inner radius R i Height h=6 mm;
2) Detection method and result:
(1) inputting frequency into exciting coil 1f 1 =5kHz, currentI 1 Steady-state sinusoidal excitation current of =0.7a, experiments were performed using the same method as when two sets of excitation coils 1 were installed; the obtained eddy current density change curve of the single-frequency excitation circular eddy current probe excited at the excitation frequency of 5kHz is shown in figure 4; from the graph in FIG. 4, it can be calculated that the penetration depth at the single frequency excitation of 5kHz is 13.7mm;
(2) inputting frequency into exciting coil 1f 2 =20kHz, currentI 2 =A steady-state sinusoidal excitation current of 0.7A was tested in the same way as when two sets of excitation coils 1 were installed; the obtained single-frequency excitation circular eddy current probe has an eddy current density change curve when excited at an excitation frequency of 20kHz, and is shown in figure 4. From the graph in FIG. 4, it can be calculated that the penetration depth at 20kHz single frequency excitation is 10.08mm.
3. Comparing the double-frequency excitation with the single-frequency excitation detection result:
comparison of penetration depth of the double-frequency excitation circular eddy current probe when the excitation frequencies of 5kHz and 20kHz are combined and penetration depth of the single-frequency excitation circular eddy current probe when the excitation frequencies of 5kHz and 20kHz are respectively excited is shown in table 1:
from the above results, it is clear that the penetration depth can reach 21.28mm when the dual-frequency excitation eddy current probe is used for combining the excitation frequencies of 5kHz and 20kHz, and is larger than the penetration depth obtained by respective single-frequency excitation.
Example 4:
in order to further verify that the penetration depth of the double-frequency excitation circular eddy current probe for detecting the thick-wall deep crack defect is superior to that of the corresponding single-frequency excitation probe, on the basis of the embodiment 2, the penetration depth comparison experiment of the single-frequency excitation eddy current probe and the double-frequency excitation eddy current probe is further carried out by using two excitation frequencies of 30kHz and 80 kHz.
1. When the double-frequency excitation circular eddy current detection probe is adopted for experiments, 30kHz and 1.3A current is input into the excitation coil 1 positioned at the left side of the detection coil 3, and 80kHz and 0.7A current is input into the excitation coil 1 positioned at the right side of the detection coil 3; the configuration parameters, the detection method and the results of the double-frequency excitation eddy current probe are as follows:
1) Configuration parameters:
(1) two sets of excitation coils 1 basic dimensions: outer radius R o 12mm, inner radius R i Height h=6 mm;
(2) the excitation frequencies of the two groups of excitation coils 1 are respectively:f left =30khz and f right =80kHz
(3) The excitation current in the two groups of excitation coils 1 is respectively as follows:I left =1.3a and I right =0.7A
(4) Distance between two sets of excitation coils 1:S=16mm
2) The detection method comprises the following steps:
as shown in fig. 2, the detection was performed according to the method in example 2;
3) Detection result:
from the eddy current density change curve of the dual-frequency excitation circular eddy current probe obtained in the embodiment 4 at the combination of the two excitation frequencies of 30kHz and 80kHz, as shown in fig. 5, the graph in fig. 5 can calculate that the penetration depth can reach 13.87mm when the excitation frequencies of 30kHz and 80kHz are combined.
2. On the basis of examples 1 and 2, only one set of excitation coils 1 was installed, and experiments were performed using a single frequency excitation eddy current probe. When a single-frequency excitation circular eddy current detection probe is adopted for experiments, 30kHz and 0.7A current and 80kHz and 0.7A current are sequentially input into an excitation coil 1; the basic size of the exciting coil 1, the detection method and the result are as follows:
1) Basic dimensions of the excitation coil 1: outer radius R o 12mm, inner radius R i Height h=6 mm;
2) Detection method and result:
(1) input into the exciting coil 1f 1 =30kHz、I 1 Steady-state sinusoidal excitation current of =0.7a, experiments were performed using the same method as when two sets of excitation coils 1 were installed; the obtained single-frequency excitation circular eddy current probe has an eddy current density change curve when excited at an excitation frequency of 30kHz, and is shown in figure 6. From the graph in FIG. 6, it can be calculated that the penetration depth at 30kHz single frequency excitation is 8.663mm;
(2) input into the exciting coil 1f 2 =80kHz、I 2 Steady-state sinusoidal excitation current of =0.7a, experiments were performed using the same method as when two sets of excitation coils 1 were installed; the obtained single-frequency excitation circular eddy current probe has an eddy current density change curve when excited at an excitation frequency of 80kHz, and is shown in figure 6. From the graph in FIG. 6, it can be calculated that the penetration depth at 80kHz single frequency excitation is 6.447mm.
3. Comparing the double-frequency excitation with the single-frequency excitation detection result:
comparison of penetration depth of the dual-frequency excitation circular eddy current probe at the combination of the excitation frequencies of 30kHz and 80kHz and penetration depth of the single-frequency excitation circular eddy current probe at the excitation frequencies of 30kHz and 80kHz respectively is shown in Table 2:
from the results, when the dual-frequency excitation eddy current probe is used for combining the excitation frequencies of 30kHz and 80kHz, the penetration depth can reach 13.87mm, and the penetration depth obtained by the corresponding single-frequency excitation probe is more than 1.6 times.
The above description is only of the preferred embodiments of the present invention, and is not intended to limit the scope of the claims. Any solution implemented in the scope of the claims covered by the claims of this application, or any solution that is possible to a person skilled in the art, using the method content disclosed above, falls within the scope of protection of the invention.
Claims (8)
1. A dual-frequency excitation circular eddy current probe for detecting thick-wall deep crack defects is characterized in that: the device comprises an excitation probe assembly, a detection probe assembly and a fixing frame; the excitation probe assemblies are in two groups and are distributed in bilateral symmetry with the detection probe assemblies as the center; each group of excitation probe components consists of 1 excitation coil (1) and 1 corresponding excitation coil mounting upright post (2), and the excitation coils (1) are sleeved on the excitation coil mounting upright posts (2); the detection probe assembly consists of a detection coil (3) and a detection coil mounting upright post (4), and the detection coil (3) is sleeved on the detection coil mounting upright post (4); the fixing frame consists of an upright post fixing plate (5) and a scanning component connecting piece (6), and the upright post fixing plate (5) is fixedly connected with the scanning component connecting piece (6); the bottom ends of the exciting coil mounting stand columns (2) and the bottom ends of the detecting coil mounting stand columns (4) are mounted on a stand column fixing plate (5);
the exciting coil (1) and the detecting coil (3) are circular eddy current coils;
the diameters of the exciting coil (1) and the corresponding exciting coil mounting stand column (2) are respectively larger than those of the detecting coil (3) and the corresponding detecting coil mounting stand column (4);
the exciting coil (1) is excited by adopting sine double-frequency alternating current;
gap distance s= (1.4-2) x R between the two sets of excitation coils (1) o ，R o For exciting the outer radius of the coil.
2. A dual frequency excitation circular eddy current probe for detecting thick wall deep crack defects as claimed in claim 1, wherein: the whole double-frequency excitation circular eddy current probe is detachably mounted with the scanning component through the scanning component connecting piece (6).
3. A dual frequency excitation circular eddy current probe for detecting thick wall deep crack defects as claimed in claim 1, wherein: the exciting coil (1) is completely sleeved on the exciting coil mounting upright post (2), and the top end surface of the exciting coil is kept in the same plane with the top end surface of the exciting coil mounting upright post (2) so as to keep a fixed relative position relation of the exciting coil (1) in the detection process;
the detection coil (3) is completely sleeved on the detection coil mounting upright post (4), and the top end surface of the detection coil is kept in the same plane with the top end surface of the detection coil mounting upright post (4) so as to keep the fixed relative position relation of the detection coil (3) in the detection process.
4. A dual frequency excitation circular eddy current probe for detecting thick wall deep crack defects as claimed in claim 1, wherein: the scanning component connecting piece (6) is a connecting plate (7), and a mounting hole (8) is formed in the connecting plate (7) and used for integrally mounting the double-frequency excitation circular eddy current probe on the scanning component.
5. A dual frequency excitation circular eddy current probe for detecting thick wall deep crack defects as claimed in claim 1, wherein: the exciting coil mounting stand column (2), the detecting coil mounting stand column (4) and the fixing frame are all made of PVC materials;
the exciting coil (1) and the detecting coil (3) are formed by winding enameled wires.
6. A method for detecting thick-wall deep crack defects using the dual-frequency excitation circular eddy current inspection probe according to any one of claims 1-5, characterized in that: the method comprises the following steps:
s1, continuously introducing steady-state sinusoidal excitation currents with different frequencies and sizes into two groups of excitation coils (1) through a synchronous alternating-current power supply (9), wherein the sinusoidal excitation currents generate a vortex field in a metal flat test piece (13);
s2, C scanning is carried out on the surface of the test piece (13) by the detection probe assembly through the scanning control console, a vortex field at a defect is disturbed by the defect, and defect information is fed back to the detection coil (3) through the disturbance magnetic field;
s3, inputting a detection signal in the detection coil (3) into a filter (10), and filtering out high-frequency noise in the detection signal by using the filter (10);
s4, inputting the detection signal filtered to remove high-frequency noise into an amplifier (11), amplifying the weak detection signal through the amplifier (11), and outputting the weak detection signal to an oscilloscope (12);
and S5, displaying the defect signal of the test piece (13) on an oscilloscope (12) in real time, finding out the defect, and calculating the actual depth of the defect through a calibration curve of a standard test piece.
7. The method for detecting thick-wall deep crack defects by using the double-frequency excitation circular eddy current testing probe according to claim 6, wherein the method comprises the following steps: the gap distance s=16 mm between the two groups of excitation coils (1).
8. The method for detecting thick-wall deep crack defects by using the double-frequency excitation circular eddy current testing probe according to claim 6, wherein the method comprises the following steps: of the two groups of exciting coils (1), the exciting coil (1) on the higher frequency side is matched with smaller exciting current, the exciting coil (1) on the lower frequency side is matched with larger exciting current, and the current in each exciting coil (1) is kept to be 0.5-0.7 times of the exciting frequency fed into the exciting coils.
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| CN109406621B (en) * | 2018-12-30 | 2023-05-26 | 北方民族大学 | Double-frequency uniform vortex probe and deep crack mixing detection signal extraction technology |
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| CN111999380B (en) * | 2020-09-25 | 2023-07-14 | 北方民族大学 | Eddy current superposition probe for detecting layering defects and detection method |
| CN112034037B (en) * | 2020-09-25 | 2023-07-25 | 北方民族大学 | Eddy current synchronous detection method and probe for multiple types of defects |
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