CN111257409B - Double-layer double-D-shaped coil and defect direction detection method and device based on coil - Google Patents

Double-layer double-D-shaped coil and defect direction detection method and device based on coil Download PDF

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CN111257409B
CN111257409B CN202010069316.1A CN202010069316A CN111257409B CN 111257409 B CN111257409 B CN 111257409B CN 202010069316 A CN202010069316 A CN 202010069316A CN 111257409 B CN111257409 B CN 111257409B
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CN111257409A (en
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于亚婷
王伟
张磊
程西蒙
王磊
王振伟
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University of Electronic Science and Technology of China
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    • G—PHYSICS
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    • G01N27/90—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables for investigating the presence of flaws using eddy currents
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
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    • G01N27/90—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables for investigating the presence of flaws using eddy currents
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Abstract

The invention discloses a double-layer double-D type coil and a method and a device for detecting the defect direction of a metal component based on the coil, wherein the coil comprises an upper coil and a lower coil which are parallel to each other, and the shapes of the upper coil and the lower coil are double-D type; the outermost layer radius, the number of turns of the coil and the wire spacing of the upper-layer coil and the lower-layer coil are equal, and the distance between planes where the two coils are located is the distance between the upper-layer coil and the lower-layer coil. The detection device comprises an excitation signal generation module, a double-layer double-D type coil probe, a tested piece, a signal amplification and filtering module, a data acquisition and processing module and a defect direction quantitative detection module. The invention provides a double-layer double-D type coil structure, and provides a quantitative detection method and a device for the defect direction in a metal component based on the structure, so that the quantitative nondestructive detection of the defect direction in the metal component can be realized, a foundation is laid for the quantitative nondestructive detection of the depth and the width of the defect, and the precision of the pulse eddy current quantitative detection of the defect of the metal component is improved.

Description

Double-layer double-D-shaped coil and defect direction detection method and device based on coil
Technical Field
The invention belongs to the technical field of nondestructive testing, and particularly relates to a double-layer double-D type coil structure, and a method and a device for quantitative nondestructive testing of the defect direction of a metal component based on the double-layer double-D type coil.
Background
The eddy current detection technology is a nondestructive detection which utilizes the electromagnetic induction principle to nondestructively evaluate certain performances of a conductive material and a workpiece thereof or discover defects by measuring the change of induced eddy current in the detected workpiece.
The induced magnetic field associated with the eddy current is superposed with the original magnetic field, so that the comprehensive magnetic field of the detection system changes along with the change of the electromagnetic property of the metal component, the defect geometric parameters or the lifting distance, and the complex impedance of the detection coil changes. Since the magnitude, phase, flow pattern of the induced eddy current in the conductor and its accompanying magnetic field are affected by the physical characteristics of the conductor, the physical properties and integrity, etc. of the metal member are nondestructively evaluated by monitoring the change in the impedance of the detection coil or the change in the integrated magnetic field.
Conventional eddy current testing is a surface or near-surface non-destructive testing method. Compared with other non-destructive testing methods, eddy current testing has the following advantages: (1) the detection sensitivity to the surface and near-surface defects of the conductive material is high; (2) the application range is wide, and various physical and process factors influencing the induced eddy current characteristic can be monitored; (3) the coupling agent is not needed, and the high-speed, high-efficiency and automatic detection of the pipe, the rod and the wire rod is easy to realize; (4) under certain conditions, the information about the depth of the crack can be reflected; (5) the method can be used for monitoring the inner hole surfaces of high-temperature thin-walled tubes, thin wires, parts and other occasions where the detection methods are not applicable. However, the direction, depth and width of the defect can generate coupling influence on the comprehensive magnetic field, so that the eddy current nondestructive testing technology is difficult to realize the simultaneous detection of the direction, depth and width of the defect. Therefore, a plurality of nondestructive detection methods are combined to realize quantitative nondestructive detection of the defects in the metal component.
Wu Dehe et al, in the text "influence of directivity of surface defect on magnetic leakage magnetic field distribution", analyzed the influence of directivity of long defect and short defect in magnetic leakage nondestructive testing MFL on magnetic field in three directions of x, y and z of magnetic leakage nondestructive testing system and its influence law through the guidelines and experimental comparison. Research shows that the larger the amplitude of the detection signal is when the magnetization direction of the object to be detected is perpendicular to the direction of the defect, and the smaller the amplitude of the detection signal is when the magnetization direction of the object to be detected is parallel to the direction of the defect. In the article of 'influence of defect direction on GMR-based eddy current defect detection', Wang super et al studied the qualitative and quantitative relationship between the GMR-based rectangular coil-excited eddy current detection probe and the defect direction through simulation and experiment. The research shows that: when the defects are perpendicular to the bottom surface of the coil to excite current, the defects have stronger effect of blocking the eddy current, the change of the magnetic induction intensity caused by the defects is more obvious, and the identifiability of the defects is higher. On the basis, scanning experiments are carried out on the defects in different directions, the peak value of a magnetic induction intensity distribution curve obtained when the defects are parallel to the axis of the exciting coil is clear, the defect signal is more prominent, the position of a peak point is more definite, and a foundation is laid for judging the size of the defects by utilizing the peak distance.
The eddy current nondestructive detection can realize quantitative measurement of artificial defects in metal components, and is one of the common methods for detecting surface and subsurface defects in metal components. However, the existing research shows that the defects in different directions have different degrees of obstruction to eddy currents in the metal component, so that the defect directions have important influence on the nondestructive quantitative detection result of the electromagnetic eddy currents, but no research literature proposes a method for measuring the defect directions.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, provides a double-layer double-D type coil structure, and provides a method and a device for quantitative nondestructive detection of the defect direction of a metal component based on the structure, so that the quantitative nondestructive detection of the defect direction in the metal component can be realized, a foundation is laid for the quantitative nondestructive detection of the depth and the width of the defect, and the precision of the pulse eddy current quantitative detection of the defect of the metal component is improved.
The purpose of the invention is realized by the following technical scheme: a double-layer double-D type coil structure comprises an upper-layer coil and a lower-layer coil which are parallel to each other, wherein the upper-layer coil and the lower-layer coil are both double-D type in shape; the outermost layer radius, the coil turns and the wire spacing of the upper coil and the lower coil are equal, and the distance between the planes of the two coils is the distance d between the upper coil and the lower coil;
the central lines of the upper coil and the lower coil are respectively l2、l1Taking the opposite direction of current flowing in each layer of coil as the central line l of the layer of coil2、l 10 deg. reference direction, the central line l of the upper coil2Projected to the lower coil plane to obtain2'; when the deflection angle between the two layers of coils is zero DEG,/1And l2' overlapping; when the upper coil rotates clockwise by an angle theta0When l is turned on1And l2' Angle of included formation is theta0The angle is called as the deflection angle between the upper layer coil and the lower layer coil; center line l of lower coil1The center line of the double-layer double-D type coil is defined;
when the upper and lower layers of coils are electrifiedThe deflection angle theta between the two layers of coils when the flow input ends are connected0The range of (1) is 0-360 degrees; when the current input ends of the upper and lower layers of coils are not connected, the deflection angle theta between the two layers of coils0The range of (A) is 0 to 180 degrees.
The invention also discloses a metal component defect direction quantitative nondestructive testing method based on the double-layer double-D type coil, which comprises the following steps:
s1, manufacturing and processing a double-layer double-D type coil probe, wherein the probe comprises a signal excitation unit and a signal receiving unit, the signal excitation unit is of a double-layer double-D type coil structure, and the signal receiving unit is a detection coil or a magnetic sensor;
s2, generating a pulse excitation signal with fixed frequency: generating a pulsed excitation signal U0Inputting the signals into a signal excitation unit of the double-layer double-D type coil probe;
s3, extracting reference signals: placing a probe for processing a double-layer double-D type coil at a position which is above a region of a tested piece without defects and is lifted to a certain height l, and detecting a reference voltage signal A0；
S4, measuring detection signal: fixing a double-layer double-D type coil probe at the position with the same lift-off height l above the defect area of the measured metal component, and respectively measuring the two layers in different known defect directions thetaiLower voltage signal AiAnd in an unknown defect direction thetadVoltage signal a ofdAnd detecting the voltage signal AiAnd AdThe signal is input to a response signal amplifying and filtering module; n, n represents the number of measurements;
s5, response signal amplification and filtering: for voltage signal AiAnd AdAmplifying and filtering to remove AiAnd AdAmplifying the filtered signal to obtain an ideal voltage signal A'iAnd A'dAnd give A'iAnd A'dPeak value of (B)ziAnd Bzd；
S6, determining the defect direction comprises the following two substeps:
s61, according to (theta)i，Bzi) Plotting the defect direction θiAnd BziObtaining a relation curve graph which presents symmetrical distribution about the defect angle;
according to thetaiAnd BziFitting the relation curve to obtain the defect directions theta and BzFunctional relationship of (c):
θ＝G(Bz) (1)；
s62, solving the defect direction: unknown defect direction thetadVoltage signal a ofdSubstituting the formula (1) to obtain two defect direction values thetad1And thetad2(ii) a Wherein, thetad1At an acute angle, θd2Is an obtuse angle; differential signal Delta A ═ max | A'd-A0If Δ A > ε, the defect direction θd＝θd2(ii) a On the contrary, the defect direction thetad＝θd1(ii) a Wherein epsilon is a preset threshold value.
Further, the defect direction θ is defined as: taking the reverse direction of the current flowing into the lower coil of the double-layer double-D type coil as the initial direction of the rotation angle of the coil relative to the defect; center line l of winding1Projected on the surface of the tested piece to obtain1' when the coil and the tested piece have deflection angle, l1The included angle theta corresponding to the central line of the defect is the relative defect deflection angle between the defect and the double-layer D-shaped coil and is defined as the defect direction.
Further, in the steps S3 and S4, a specific method for obtaining the voltage signal is as follows: after the pulse excitation signal is input into the excitation unit, a coupled electromagnetic field is formed in the space between the metal component to be detected and the double-layer double-D type coil according to the principle of electromagnetic induction, and the signal receiving unit is distributed in the space, detects the magnetic induction intensity of the position where the signal receiving unit is located and converts the magnetic induction intensity into a voltage signal.
The metal component defect direction quantitative nondestructive detection device based on the double-layer double-D type coil comprises an excitation signal generation module, a double-layer double-D type coil probe, a tested piece with a defect, a signal amplification filtering module, a data acquisition and processing module and a defect direction quantitative detection module;
the excitation signal generation module is connected with the double-layer double-D type coil probe and is used for generating a square wave excitation signal with fixed frequency and providing an accurate square wave excitation signal for the excitation coil;
the signal amplification and filtering module is respectively connected with the double-layer double-D type coil probe and the data acquisition and processing module, and is used for performing amplification and filtering processing on the voltage signal received in the probe and transmitting the amplified and filtered signal to the data acquisition and processing module;
the data acquisition and processing module is used for acquiring and processing the amplified and filtered signals and transmitting the processed signals to the defect direction quantitative detection module;
the defect direction quantitative detection module is used for calculating the defect direction.
The invention has the beneficial effects that: compared with the prior detection technology, the double-layer double-D type coil structure provided by the invention has the following two main advantages: 1. the direction information of the defect is the same as the depth and width information of the defect and is an important parameter for representing the state of the defect in a metal component, but most of the existing pulse eddy current coils adopt cylindrical coils, are insensitive to the direction of the defect and cannot accurately detect the direction information of the defect. The coil deflection angle exists between the upper coil and the lower coil, so that the coil structure can realize accurate detection of the defect direction. 2. The traditional eddy current detection coil is formed by manual work or winding by a winding machine, and has the problem of certain interchangeability. The coil structure provided by the invention can be embedded in a PCB (printed circuit board) through copper deposition, etching and other processes, and the consistency of the coil can be ensured, so that the coil structure provided by the invention is more suitable for the occasions of array type eddy current coil nondestructive testing.
The quantitative nondestructive detection method and device for the defect direction of the metal component are provided based on the double-layer double-D type coil structure, quantitative nondestructive detection of the defect direction in the metal component can be achieved, a foundation is laid for achieving quantitative nondestructive detection of the depth and width of the defect, and the precision of pulse eddy current quantitative detection of the defect of the metal component is improved.
Drawings
Fig. 1 is a first schematic diagram of a double-layer double-D type coil structure;
fig. 2 is a second schematic diagram of a double-layer double-D type coil structure;
FIG. 3 is a schematic diagram of defect versus coil deflection angle definition;
FIG. 4 is a graph of the relationship between the defect direction and the Z component of the flux density of the double-layer double-D coil;
FIG. 5 is a structural diagram of a quantitative nondestructive testing device based on a double-layer double-D type coil;
FIG. 6 is a graph showing the relationship between the Z component of the magnetic flux density and the defect direction
FIG. 7 is a comparison graph of two defect direction differential signals at a flat angle to each other.
Detailed Description
The technical scheme of the invention is further explained by combining the attached drawings.
As shown in fig. 1, a double-layer double-D type coil structure includes an upper coil and a lower coil which are parallel to each other, and both the upper coil and the lower coil are double-D type; the outermost layer radius, the coil turns and the wire spacing of the upper coil and the lower coil are equal, and the distance between the planes of the two coils is the distance d between the upper coil and the lower coil;
the deflection angle of the double-layer double-D-type coil structure is defined as shown in FIG. 2, and the central lines of the upper coil and the lower coil are respectively defined as l2、l1Taking the opposite direction of current flowing in each layer of coil as the central line l of the layer of coil2、l 10 deg. reference direction, the central line l of the upper coil2Projected to the lower coil plane to obtain2'; when the deflection angle between the two layers of coils is zero DEG,/1And l2' overlapping; when the upper coil rotates clockwise by an angle theta0When l is turned on1And l2' Angle of included formation is theta0The angle is called as the deflection angle between the upper layer coil and the lower layer coil; center line l of lower coil1The center line of the double-layer double-D type coil is defined;
because the two layers of coils are the same, and the single-layer coil is in a centrosymmetric pattern, two D-shaped structures of the single-layer coil are adjacent in the vertical direction; when two layers of wires are arrangedWhen the current inputs of the coils are connected, it can be known that when θ is0If 180 ° results in the current flow direction of the two-layer coil being exactly opposite, the deflection angle θ between the two-layer coil can be specified0The range of (1) is 0-360 degrees; when the current input ends of the upper and lower layers of coils are not connected, the current input end can be known as theta0If the current direction of the upper and lower layer of coils is exactly the same again when 180 °, the deflection angle θ between the two layers of coils can be specified0The range of (A) is 0 to 180 degrees.
The defect direction is first defined and specified as shown in fig. 3. The defect direction θ is defined as: taking the reverse direction of the current flowing into the lower coil of the double-layer double-D type coil as the initial direction of the rotation angle of the coil relative to the defect; center line l of winding1Projected on the surface of the tested piece to obtain1' when the coil and the tested piece have deflection angle, l1The included angle theta corresponding to the central line of the defect is the relative defect deflection angle between the defect and the double-layer D-shaped coil and is defined as the defect direction.
The invention relates to a metal component defect direction quantitative nondestructive testing method based on a double-layer double-D type coil, which comprises the following steps:
s1, manufacturing and processing a double-layer double-D type coil probe, wherein the probe comprises a signal excitation unit and a signal receiving unit, the signal excitation unit is of a double-layer double-D type coil structure, and the signal receiving unit is a detection coil or a magnetic sensor;
s2, generating a pulse excitation signal with fixed frequency: generating a pulsed excitation signal U0Inputting the signals into a signal excitation unit of the double-layer double-D type coil probe;
s3, extracting reference signals: placing a probe for processing a double-layer double-D type coil at a position which is above a region of a tested piece without defects and is lifted to a certain height l, and detecting a reference voltage signal A0；
S4, measuring detection signal: fixing a double-layer double-D type coil probe at the position with the same lift-off height l above the defect area of the measured metal component, and respectively measuring the two layers in different known defect directions thetaiLower voltage signal AiAnd in the unknown absenceSink direction thetadVoltage signal a ofdAnd detecting the voltage signal AiAnd AdThe signal is input to a response signal amplifying and filtering module; n, n represents the number of measurements;
s5, response signal amplification and filtering: for voltage signal AiAnd AdAmplifying and filtering to remove AiAnd AdAmplifying the filtered signal to obtain an ideal voltage signal A'iAnd A'dAnd give A'iAnd A'dPeak value of (B)ziAnd Bzd；
S6, determining the defect direction comprises the following two substeps:
s61, according to (theta)i，Bzi) Plotting the defect direction θiAnd BziA graph showing a symmetrical distribution with respect to the defect angle is obtained, as shown in fig. 4. As can be seen from fig. 4: when the deflection angle of the defect and the relative defect of the double-layer D-shaped coil is an acute angle, the voltage signal peak value B is increased along with the increase of the angleziGradually decrease; when the deflection angle of the defect relative to the double-layer D-shaped coil is obtuse, the voltage signal peak value B increases along with the increase of the angleziGradually increases and the relationship curve presents a symmetrical distribution about the defect angle. Therefore, under the condition that the defect angle is unknown, a certain voltage signal peak value B is measuredz0Two deflection angles theta can be obtained01And theta02. Since the relationship shown in fig. 4 is not a monotonic defect, meaning that the same field strength corresponds to two defect directions, it has been found that the sum of the two defect directions is 180 °. It was also found that the peak value variation of the defective and non-defective differential signals was large when the direction of the defect was less than 90 ° and greater than 90 °. When the defect direction is smaller than 90 degrees, the peak value of the differential signal is almost zero, but when the defect direction is larger than 90 degrees, the peak value of the differential signal is larger, so that a proper threshold value epsilon can be adopted to judge whether the defect direction is an acute angle or an obtuse angle.
According to thetaiAnd BziFitting the relation curve to obtain the defect directions theta and BzFunctional relationship of (c):
θ＝G(Bz) (1)；
s62, solving the defect direction: unknown defect direction thetadVoltage signal a ofdSubstituting the formula (1) to obtain two defect direction values thetad1And thetad2(ii) a Wherein, thetad1At an acute angle, θd2Is an obtuse angle; differential signal Delta A ═ max | A'd-A0If Δ A > ε, the defect direction θd＝θd2(ii) a On the contrary, the defect direction thetad＝θd1(ii) a Wherein epsilon is a preset threshold value.
Further, in the steps S3 and S4, a specific method for obtaining the voltage signal is as follows: after the pulse excitation signal is input into the excitation unit, a coupled electromagnetic field is formed in the space between the metal component to be detected and the double-layer double-D type coil according to the principle of electromagnetic induction, and the signal receiving unit is distributed in the space, detects the magnetic induction intensity of the position where the signal receiving unit is located and converts the magnetic induction intensity into a voltage signal.
As shown in fig. 5, the device for quantitatively and nondestructively detecting the defect direction of a metal component based on a double-layer double-D type coil of the present invention comprises an excitation signal generation module, a double-layer double-D type coil probe, a tested piece with a defect, a signal amplification and filtering module, a data acquisition and processing module, and a defect direction quantitative detection module;
the excitation signal generation module is connected with the double-layer double-D type coil probe and is used for generating a square wave excitation signal with fixed frequency and providing an accurate square wave excitation signal for the excitation coil;
the signal amplification and filtering module is respectively connected with the double-layer double-D type coil probe and the data acquisition and processing module, and is used for performing amplification and filtering processing on the voltage signal received in the probe and transmitting the amplified and filtered signal to the data acquisition and processing module;
the data acquisition and processing module is used for acquiring and processing the amplified and filtered signals (generally, a data acquisition card is used for acquiring time domain signals in the defect direction to acquire a peak value), and transmitting the processed signals to the defect direction quantitative detection module;
the defect direction quantitative detection module is used for calculating the defect direction.
When the number of turns of the double-layer double-D type coil is 10, the distance between each turn of the coil is 5mil, the distance between the upper coil and the lower coil is 1mm, the lifting distance is 0.5mm, the included angle between the upper coil and the lower coil is 135 degrees, the defect depth is 0.6mm, the defect width is 0.6mm, and the defect direction is changed from 0 degree to 180 degrees, the relationship between the coil induction magnetic field and the defect direction is shown in FIG. 6.
As shown in fig. 6, in this embodiment, when the defect direction is 60 ° < θ <120 °, the defect direction has little influence on the detection result, and when 0 ° < θ <60 ° and 120 ° < θ <180 °, the defect direction has an important influence on the detection result. The direction of the defect can be detected using fig. 6. As can also be seen from fig. 5, the influence curve is symmetrical about θ at 90 °, i.e. when the two defect directions are mutually orthogonal, the corresponding magnetic induction is the same.
To achieve quantitative detection, two differential signals in the defect directions that are orthogonal to each other were investigated and compared as shown in fig. 7. As can be seen from fig. 7, when the defect direction is less than 90 °, the peak of the differential signal is close to zero, but when the defect direction is greater than 90 °, the peak of the differential signal is significant. Thus, by setting a suitable threshold, the unique direction of the defect can be determined.
It will be appreciated by those of ordinary skill in the art that the embodiments described herein are intended to assist the reader in understanding the principles of the invention and are to be construed as being without limitation to such specifically recited embodiments and examples. Those skilled in the art can make various other specific changes and combinations based on the teachings of the present invention without departing from the spirit of the invention, and these changes and combinations are within the scope of the invention.

Claims (4)

1. The metal component defect direction quantitative nondestructive detection method based on the double-layer double-D type coil is characterized by comprising the following steps of:
s1, manufacturing and processing a double-layer double-D type coil probe, wherein the probe comprises a signal excitation unit and a signal receiving unit, the signal excitation unit is of a double-layer double-D type coil structure, and the signal receiving unit is a detection coil or a magnetic sensor; the double-layer double-D type coil structure comprises an upper-layer coil and a lower-layer coil which are parallel to each other, wherein the upper-layer coil and the lower-layer coil are both double-D type; the outermost layer radius, the coil turns and the wire spacing of the upper coil and the lower coil are equal, and the distance between the planes of the two coils is the distance d between the upper coil and the lower coil;
the central lines of the upper coil and the lower coil are respectively l2、l1Taking the opposite direction of current flowing in each layer of coil as the central line l of the layer of coil2、l10 deg. reference direction, the central line l of the upper coil2Projected to the lower coil plane to obtain2'; when the deflection angle between the two layers of coils is zero DEG,/1And l2' overlapping; when the upper coil rotates clockwise by an angle theta0When l is turned on1And l2' Angle of included formation is theta0The angle is called as the deflection angle between the upper layer coil and the lower layer coil; center line l of lower coil1The center line of the double-layer double-D type coil is defined;
when the current input ends of the upper and lower layers of coils are connected, the deflection angle theta between the two layers of coils0The range of (1) is 0-360 degrees; when the current input ends of the upper and lower layers of coils are not connected, the deflection angle theta between the two layers of coils0The range of (1) is 0 to 180 degrees;
s2, generating a pulse excitation signal with fixed frequency: generating a pulsed excitation signal U0Inputting the signals into a signal excitation unit of the double-layer double-D type coil probe;
s3, extracting reference signals: placing the probe for processing double-layer double-D type coil at a position with certain lift-off height l above the region without defects of the tested piece, and detecting a reference voltage signal A0；
S4, measuring detection signal: fixing a double-layer double-D type coil probe at the position with the same lift-off height l above the defect area of the measured metal component, and respectively measuring the two layers in different known defect directions thetaiLower voltage signal AiAnd in an unknown defect direction thetadVoltage signal a ofdAnd detecting the voltage signal AiAnd AdThe signal is input to a response signal amplifying and filtering module; i is 2,3, …, n, n represents the number of measurements;
s5, response signal amplification and filtering: for voltage signal AiAnd AdAmplifying and filtering to remove AiAnd AdAmplifying the filtered signal to obtain an ideal voltage signal A'iAnd A'dAnd give A'iAnd A'dPeak value of (B)ziAnd Bzd；
S6, determining the defect direction comprises the following two substeps:
s61, according to (theta)i，Bzi) Plotting the defect direction θiAnd BziObtaining a relation curve graph which presents symmetrical distribution about the defect angle;
according to thetaiAnd BziFitting the relation curve to obtain the defect directions theta and BzFunctional relationship of (c):
θ＝G(Bz) (1)；
s62, solving the defect direction: unknown defect direction thetadPeak value B of the ideal voltage signalzdSubstituting the formula (1) to obtain two defect direction values thetad1And thetad2(ii) a Wherein, thetad1At an acute angle, θd2Is an obtuse angle; differential signal Delta A ═ max | A'd-A0If Δ A > ε, the defect direction θd＝θd2(ii) a On the contrary, the defect direction thetad＝θd1(ii) a Wherein epsilon is a preset threshold value.
2. The method for quantitatively and nondestructively detecting the defect direction of the metal component based on the double-layer double-D type coil as claimed in claim 1, wherein the defect direction θ is defined as: taking the reverse direction of the current flowing into the lower coil of the double-layer double-D type coil as the initial direction of the rotation angle of the coil relative to the defect; center line l of winding1Projected on the surface of the tested piece to obtain1' when the coil and the tested piece have deflection angle, l1Will be associated with the center of the defectThe lines form a corresponding included angle theta, which is the relative defect deflection angle between the defect and the double-layer D-shaped coil and is defined as the defect direction.
3. The method for quantitatively and nondestructively detecting the defect direction of a metal member based on a double-layer double-D type coil as claimed in claim 1, wherein the steps S3 and S4 are performed by the following steps: after the pulse excitation signal is input into the excitation unit, a coupled electromagnetic field is formed in the space between the metal component to be detected and the double-layer double-D type coil according to the principle of electromagnetic induction, and the signal receiving unit is distributed in the space, detects the magnetic induction intensity of the position where the signal receiving unit is located and converts the magnetic induction intensity into a voltage signal.
4. The metal component defect direction quantitative nondestructive detection device based on the double-layer double-D type coil is implemented by adopting the detection method according to any one of claims 1 to 3, and is characterized by comprising an excitation signal generation module, a double-layer double-D type coil probe, a tested piece with a defect, a signal amplification filtering module, a data acquisition and processing module and a defect direction quantitative detection module;
the excitation signal generation module is connected with the double-layer double-D type coil probe and is used for generating a square wave excitation signal with fixed frequency and providing an accurate square wave excitation signal for the excitation coil;
the signal amplification and filtering module is respectively connected with the double-layer double-D type coil probe and the data acquisition and processing module, and is used for performing amplification and filtering processing on the voltage signal received in the probe and transmitting the amplified and filtered signal to the data acquisition and processing module;
the data acquisition and processing module is used for acquiring and processing the amplified and filtered signals and transmitting the processed signals to the defect direction quantitative detection module;
the defect direction quantitative detection module is used for calculating the defect direction.
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