CN109580721A - A kind of pulse eddy current detection method and detection device of ferromagnetic metallic material conductivity - Google Patents
A kind of pulse eddy current detection method and detection device of ferromagnetic metallic material conductivity Download PDFInfo
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Abstract
本发明公开了一种铁磁金属材料电导率的脉冲涡流检测方法和检测装置，属于电磁无损检测技术领域。在铁磁平板脉冲涡流检测模型感应电压的时域解析解的基础上，利用感应电压测量曲线，建立感应电压时域信号测量值与理论计算值之间的最小二乘问题来反演被检铁磁构件的电导率与磁导率；并通过逐步增加脉冲激励电流的幅值，得到不同幅值脉冲电流激励下电导率反演结果的变化曲线；最后通过曲线拟合的方法，找到电导率反演结果的变化曲线与纵坐标轴的交点，即为被检铁磁构件的电导率。利用本发明所提供的方法和装置可为工业中铁磁金属材料的电导率提供非接触和无损检测，削弱了磁导率非线性变化对电导率检测结果的影响，提高精度和可靠性。
The invention discloses a pulse eddy current detection method and a detection device for the electrical conductivity of ferromagnetic metal materials, and belongs to the technical field of electromagnetic nondestructive detection. On the basis of the time domain analytical solution of the induced voltage in the ferromagnetic flat plate pulsed eddy current testing model, using the measured curve of the induced voltage, the least squares problem between the measured value of the time domain signal of the induced voltage and the theoretical calculated value is established to invert the tested iron. The conductivity and permeability of the magnetic components; and by gradually increasing the amplitude of the pulse excitation current, the change curves of the conductivity inversion results under the excitation of different amplitude pulse currents are obtained; finally, the conductivity inversion results are found by the method of curve fitting. The intersection of the variation curve of the result and the ordinate axis is the conductivity of the ferromagnetic component under test. The method and device provided by the invention can provide non-contact and non-destructive testing of the electrical conductivity of ferromagnetic metal materials in the industry, weaken the influence of nonlinear changes of magnetic permeability on the electrical conductivity testing results, and improve the accuracy and reliability.
Description
Technical field
The invention belongs to electromagnetic nondestructive testing fields, and in particular to a kind of pulse whirlpool of ferromagnetic metallic material conductivity
Flow detection method and detection device.
Background technique
Conductivity is an important parameter for characterizing metal material electric conductivity, material, microstructure, the heat of it and material
Processing status is closely related.By detecting the conductivity of ferromagnetic metallic material, raw material can be sorted and be recognized, be judged
The conditions of heat treatment such as annealing, quenching, assess the hardness and mechanical performance of ferromagnetic component, detect residual stress and gold in ferromagnetic component
Phase constitution variation etc..Therefore, the conductivity of ferromagnetic metallic material is carried out non-destructive testing, there is important application value.
The conductivity of material, Huo Zhetong can be reliably detected out using sinusoidal eddy-current method for non-ferromagnetic metal material
Testing result is demarcated in the reference block for crossing known conductivity, or using analytic expression direct inversion to calculate conductivity exhausted
To value.The method comparative maturity of sinusoidal eddy-current method detection non-ferromagnetic metal material conductivity, advantage are that Non-contact nondestructive can be achieved
Detection, pre-processes without the non-conductive coating layer to component surface.But the magnetic conductivity of ferromagnetic metallic material is strong, and magnetic conductivity meeting
Change with remanent magnetism, exciting current amplitude and frequency, therefore, sinusoidal eddy-current method cannot accurately detect the conductance of ferromagnetic metallic material
Rate.
DC four point probe method is the important method of the weaker material electric conductivities of electric conductivity such as current measurement soil, semiconductor.
With the conductivity of DC four point probe method detection ferromagnetic metallic material, advantage is its conductivity testing result not by permeability
Influence.It is limited in that probe must have good electrical contact with tested component surface, therefore must remove before detection tested
Component surface non-conductive coating layer, paint, oxide layer and corrosion layer etc..In addition, ferromagnetic metallic material is good conductor, high current is needed
Excitation could generate sufficiently large voltage signal, due to the fuel factor of exciting current and the measurement error of weak voltage signals,
Error is larger when four probe method being caused to detect the conductivity of ferromagnetic metallic material, testing result poor repeatability.
Impulse eddy current method be it is a kind of can electromagnetic nondestructive method to ferromagnetic metallic material examinations.With pulse electricity
Stream excitation replaces sinusoidal current to motivate, and inspires pulsed magnetic field outside tested component, makes to induce impulse eddy current in tested component,
Then by detecting the attenuation process of this impulse eddy current electromagnetic field, to detect the geometric dimension and electromagnetic parameter of tested component.
Summary of the invention
The object of the present invention is to provide the pulse eddy current detection methods and detection device of a kind of ferromagnetic metallic material conductivity.
On the basis of the time domain analytic solutions of ferromagnetic plate Pulsed eddy current testing model induced voltage, using induced voltage experiment curv,
The least square problem established between induced voltage time-domain signal measured value and calculated value carrys out inverting and is detected ferromagnetic component
Conductivity and magnetic conductivity；And the amplitude by being stepped up pulse excitation electric current, it obtains electric under different amplitude pulse current excitations
The change curve of conductance inversion result；Finally by the method for curve matching, find the change curve of conductivity inversion result with
The intersection point of axis of ordinates, the conductivity of as tested ferromagnetic component.
Present invention firstly provides a kind of pulse eddy current detection methods of ferromagnetic metallic material conductivity, the specific steps are as follows:
Step 1: the acquisition of the Pulsed eddy current testing signal of tested ferromagnetic component.
Step 2: the inversion method of tested ferromagnetic component electromagnetic parameter.
Step 3: eliminating influence of the magnetic conductivity variation to conductivity testing result using curve matching.
The method advantage that the present invention implements Pulsed eddy current testing to ferromagnetic metallic material conductivity is:
(1) a kind of non-contact, lossless detection method can be provided for the conductivity of ferromagnetic metallic material in industry, filled up
Such technological gap.Can indirectly judgement material hardness, condition of heat treatment, residual stress etc., help to improve material processing work
Skill is horizontal, provides a kind of new nondestructiving detecting means for links such as the productions, maintenance and monitoring of key position ferromagnetic component.
(2) decoupling between conductivity and magnetic conductivity is realized, impulse eddy current method is made to detect ferromagnetic metallic material conductivity
It is possibly realized.Theoretically it can be proved that conductivity can be coupled with magnetic conductivity when eddy current signal can not penetrate tested ferromagnetic component
Together, using eddy current testing signal, it can only be accurately finally inversed by the ratio of the two, can not detect conductivity.In the present invention,
Using impulse eddy current method, eddy current signal can be made effectively to penetrate tested ferromagnetic component, it, can be accurately anti-using time domain induced voltage signal
The product and relative permeability of tested ferromagnetic component conductivity and wall thickness and product two amounts of wall thickness are performed, to realize
The decoupling of conductivity and magnetic conductivity makes it possible that impulse eddy current method detects ferromagnetic metallic material conductivity.
(3) influence of the magnetic conductivity nonlinear change to conductivity testing result is weakened, conductivity testing result is improved
Precision and reliability.For ferromagnetic metallic material, the magnetic conductivity of material is difficult directly to measure, and the size of magnetic conductivity by
The factors such as tested ferromagnetic material microstructure, remanent magnetism, pulse excitation magnetic field strength influence, and will affect conductivity testing result.?
In the present invention, the magnetic conductivity of tested ferromagnetic component is on the one hand set as a unknown parameter, at the signal proposed through the invention
Reason method carrys out the value that inverting determines detection magnetic conductivity every time；On the other hand, by electric under different amplitude pulse current excitations
Conductance inversion result carries out curve fitting, and finds corresponding conductivity inversion result when external magnetic excitation field is zero and ties as detection
Fruit, to weaken the influence caused by testing result of magnetic conductivity nonlinear change, improve conductivity detection precision and can
By property.
Detailed description of the invention
Fig. 1 is the structure chart of ferromagnetic metallic material conductivity impulse eddy current electromagnetic nondestructive device.
Figure 1A is the sectional structure chart of coil probe.
Fig. 2 is the inversion result of conductivity and its matched curve under different amplitude pulse current excitations.
Specific embodiment
Below in conjunction with drawings and examples, the present invention is described in further detail.
The present invention provides the pulse eddy current detection method and detection device of a kind of ferromagnetic metallic material conductivity, the detection
Device is as shown in Figure 1, include coil probe, host, DA analog-digital converter, power amplification circuit, sampling resistor, the first AD modulus
Converter and the 2nd AD analog-digital converter, the coil probe includes coil rack, excitation coil and detection coil, and coil is visited
Head (as shown in Figure 1A, 1 is coil rack, and 2 be excitation coil, and 3 be detection coil) is placed in above tested ferromagnetic component, and coil is visited
Head the distance between lower edge and tested ferromagnetic component upper surface (referred to as coil probe lift off) are denoted as lo, under coil is popped one's head in
The wall thickness of the tested ferromagnetic component in side is denoted as d.The coil rack uses air-cored cylindrical coil skeleton, successively twines on coil rack
Around excitation coil and detection coil, wherein the position of excitation coil and detection coil be can be interchanged.The output end of host connects DA
The input terminal of digital analog converter, the input terminal of the output end connection power amplification circuit of DA digital analog converter, power amplification circuit
Output end connection sampling resistor input terminal, the second output terminal of sampling resistor connects the input of the 2nd AD analog-digital converter
End, the second input terminal of the output end connection host of the 2nd AD analog-digital converter, the first output end of sampling resistor connect excitation
The both ends at the both ends of coil, detection coil connect the first AD analog-digital converter input terminal, the output end of the first AD analog-digital converter
The first input end of host is connected, wherein host will connect to DA digital analog converter output drive digital signal, DA digital analog converter
The excitation digital signal of receipts is converted to excitation analog signal and is transferred to power amplification circuit, and power amplification circuit is by received excitation
Pulse excitation electric current is exported after analog signal amplifying power to sampling resistor, supply swashs after sampling resistor receives pulse excitation electric current
Coil is encouraged, detection coil will connect induced voltage analog signal transmission to the first AD analog-digital converter, the first AD analog-digital converter
The induced voltage analog signal of receipts is converted to induced voltage discrete digital signal and is transferred to host progress as the result is shown.
A kind of pulse eddy current detection method of ferromagnetic metallic material conductivity provided by the invention, includes the following steps:
Step 1: the acquisition (SAP) of the Pulsed eddy current testing signal of tested ferromagnetic component:
The obtaining step of pulse eddy current testing signal in step 1 of the present invention are as follows:
Step SAP-1, by coil probe (as shown in Figure 1A, 1 is coil rack, and 2 be excitation coil, and 3 be detection coil)
It is disposed vertically above tested ferromagnetic component, hold-in winding probe lift off lo(0-20mm) is constant, as shown in Figure 1；
Step SAP-2, excitation coil and detection coil are wound on coil rack, and the both ends of excitation coil connect sampling resistor
The first output end, sampling resistor input termination power amplification circuit output end, detection coil two termination the first AD moulds
The input terminal of number converter, the second output terminal of current sampling resistor connect the input terminal of the 2nd AD analog-digital converter；
Step SAP-3 is exported with host programming and is continued pulsewidth as 10~500ms, and the excitation number that amplitude is 0.1~1V is believed
Number；After DA digital analog converter, become to continue pulsewidth to be 10~500ms, amplitude is the excitation analog signal of 0.1~1V, output
To power amplification circuit；After power amplification circuit amplifying power, exports and continue pulsewidth as 10~500ms, amplitude is 0.1~5A
Pulse excitation electric current, after pulse excitation electric current flows through sampling resistor, supply excitation coil, I0For pulse excitation current amplitude；
Step SAP-4, meanwhile, the induced voltage time-domain signal u (t) at the first AD analog-digital converter acquisition testing coil both ends
(unit V), and will be in the induced voltage signal u (t) that collected storage to host；It is acquired and is sampled with the 2nd AD analog-digital converter
Resistance both ends pulse excitation current signal i (t) (unit A), and store into host.
In the present invention, the induced voltage time-domain signal that tested ferromagnetic component is carried out using Pulsed eddy current testing device and
The acquisition of exciting current signal, referred to as Pulsed eddy current testing signal acquisition step, Signal Acquisition Procedure,
SAP。
Step 2: the inversion method (PIP) of tested ferromagnetic component electromagnetic parameter:
After the induced voltage for collecting detection coil both ends according to SAP step, how to be determined by induced voltage and be detected iron
The conductivity and relative permeability of magnetic component are the key that signal processings in the present invention.Author Chen Xingle is equal to 2014, delivers
Paper " Excitation current waveform for eddy on " NDT&E International " volume 66
Current testing on the thickness of ferromagnetic plates ", gives ferromagnetic plate pulse
EDDY CURRENT model, using the ferromagnetic plate Pulsed eddy current testing model, when being passed through pulse excitation electric current i (t) in excitation coil
When, the induced voltage time-domain expression at detection coil both ends are as follows:
π value is 3.14；
E is the bottom of natural logrithm, value 2.72；
σ is the conductivity of tested ferromagnetic component, unit S/m；
D is the wall thickness of tested ferromagnetic component, unit m；
μ0For space permeability, value is 4 π × 10-7H/m；
μrFor the relative permeability for being detected ferromagnetic component；
B is the cutoff boundary of ferromagnetic plate Pulsed eddy current testing model, unit m；
λiIndicate first-order bessel function J1(bλiThe positive root of i-th of)=0；
J0(x) 0 rank Bessel function of the first kind is indicated；
ξkIt is transcendental equationK-th of positive root；
Coefficient
Time constant
T indicates the time；
I (t) is the pulse excitation current signal of sampling resistor acquisition, unit A；
I ' (t) indicates pulse excitation current signal to the derivative of time t；
" * " indicates convolution algorithm
CdFor the coil factor of excitation coil, CpFor the coil factor of detection coil, calculating formula can refer to Chen Xingle and be equal to
2014, " the Excitation current waveform for being published on " NDT&E International " volume 66
An eddy current testing on the thickness of ferromagnetic plates " text.
The present invention is based on the time domain analytic solutions of above-mentioned ferromagnetic plate Pulsed eddy current testing model induced voltage, establish induced electricity
The least square problem between time-domain signal measured value and calculated value is pressed, to the conductivity and magnetic conductivity progress at test point
Inverting, the specific steps are as follows:
Step PIP-1, by coil probe lift-off lo, tested ferromagnetic component wall thickness d and pulse excitation current signal i (t)
It is substituted into formula (1) as known quantity, while by the relative permeability μ of the conductivityσ of tested ferromagnetic component and tested ferromagnetic componentr
It is set as unknown parameter, that is, needs the parameter vector x=(x of inverting1,x2)T=(σ, μr)T；
Step PIP-2, according to SAP step, with the induction at the detection coil both ends that the first AD analog-digital converter collects
Voltage time-domain signal measurement data is (t1,u1),(t2,u2),…,(tm,um), by the reason of its induced voltage calculated with formula (1)
By calculated value u (x, ti) compare, enable induced voltage time-domain signal measured value uiError sum of squares between calculated value is minimum
Carry out inverted parameters x, that is, establish least square problem:
Remember residual function ri(x)=ui-u(x,ti), i=1,2 ..., m, and remember residual functional vector r (x)=(r1(x),r2
(x),...,rm(x))T, R2For two-dimentional real number space, m is the number of measurement, x1And x2Indicate two elements in vector x.
Step PIP-3, using iterative algorithm, solves the optimal solution x of least square problem (2) in host*, iteration
The calculating step of algorithm are as follows:
(1) initial point is given(wherein σ(1)=106~107S/m,Permit
Perhaps error ε > 0 (generally takes ε=10-3), set k=1；
(2) parameter vector for walking kthIt substitutes into calculating formula (1), calculates each of kth step
Time point tiInduced voltage calculated value u (x(k),ti), then with induced voltage time-domain signal measured value uiIt is poor to make, meter
Calculate the residual functional value of kth step
ri(x(k))=ui-u(x(k),ti), i=1,2 ..., m,
And obtain the residual functional vector r of kth step(k)；Then induced voltage theoretical curve is further calculated by formula (1)
To the first-order partial derivative of the conductivityσ of tested ferromagnetic component
And induced voltage theoretical curve is to the relative permeability μ of tested ferromagnetic componentrFirst-order partial derivative
Obtain the matrix A of m × 2k=(aij)m×2；J=1,2.
(3) solve system of equation
Acquire direction vector b；
(4) the parameter vector x walked from kth(k)It sets out, along the direction vector b of kth step(k)Make linear search, finds out step-length
αk, so that
I.e. using α as the function f (x of independent variable(k)+αb(k)) when being minimized, the value of independent variable α is αk。
And it enables
x(k+1)=x(k)+αkb(k)；
(5) if | | x(k+1)-x(k)| |≤ε then stops calculating, and obtains the optimal solution x of least square problem (2)*=x(k+1)；
Otherwise, k:=k+1, return step (2) are set.
Step PIP-4 is solved the optimal solution of least square problem (2) by above-mentioned iterative algorithmAfterwards,
The inversion result σ * for obtaining the conductivity of tested ferromagnetic component, is detected the inversion result of the relative permeability of ferromagnetic component
By the inversion result of the inversion result of the conductivity of tested ferromagnetic component and the relative permeability of tested ferromagnetic component and pulse electricity
Flow excitation amplitude I0It is mapped, is saved in host.
In the present invention, host detects signal analysis and processing to induced voltage, is finally inversed by the conductivity of tested ferromagnetic component
With the process of the relative permeability of tested ferromagnetic component, the referred to as inversion step of parameter, Parameters Inversion
Procedure, PIP.
Step 3: utilizing curve matching, eliminates influence of the magnetic conductivity variation to conductivity testing result:
For ferromagnetic metallic material, the magnetic conductivity of material is difficult directly to measure, and the size of magnetic conductivity is by tested iron
The factors such as magnetic Fine Texture of Material, remanent magnetism, pulse excitation magnetic field strength influence, and therefore, detect every time, are detected the magnetic of ferromagnetic component
Conductance may all change, to influence conductivity testing result.In the present invention, on the one hand by the magnetic of tested ferromagnetic component
Conductance is set as a unknown parameter, and the signal processing method proposed through the invention carrys out the value that inverting determines magnetic conductivity；It is another
Aspect is carried out curve fitting by the inversion result to the conductivity for being detected ferromagnetic component under different amplitude pulse current excitations,
The inversion result of the conductivity of corresponding tested ferromagnetic component when external magnetic excitation field is zero is found as testing result, to cut
Weak magnetic conductance nonlinear change is influenced caused by testing result.Specific implementation step are as follows:
Step 1: obtaining the wall thickness d of tested ferromagnetic component using vernier caliper or audigage measurement, coil is popped one's head in
It is disposed vertically above tested ferromagnetic component, the lift off l of coil probe is gone out using ruler or vernier caliper measuremento；
Step 2: the lift off l of fixed coil probeoIt is constant, by pulse excitation current amplitude I0With 0.2A stepping, from
0.2A is gradually increased 3.0A, and according to SAP step, acquires the corresponding detection coil two of different pulse excitation current amplitudes respectively
The signal for holding induced voltage time-domain signal and sampling resistor both ends pulse excitation electric current, is stored in host；
Step 3: according to PIP step, being finally inversed by the corresponding tested ferromagnetic component of different amplitude pulse exciting currents respectively
The relative permeability of conductivity and tested ferromagnetic component, and draw out tested ferromagnetic component conductivity inversion result with pulse
Exciting current amplitude I0Change curve, as shown in black circle in Fig. 2；
Step 4: utilization index functionTo in Fig. 2 be detected ferromagnetic component conductivity inversion result σ * into
Row curve matching is as illustrated in solid line in figure 2 conductivity matched curve, to obtain factor sigma in exponential function0It is fitted and ties with ε
FruitWithWhereinThe conductivity testing result of as tested ferromagnetic component.
Embodiment 1
The embodiment for implementing conductivity detection to ferromagnetic component with method in the present invention is given below.
Tested ferromagnetic component is that three pieces of diameters are 100mm, and thickness is the cylindrical steel test block of 6mm, and material is respectively
20# steel, 45# steel and Q235 steel.
Coil probe is sequentially placed into above three pieces of tested steel test block centers, the lift off of hold-in winding probe is
5mm is constant, pulse excitation current amplitude I0Using 0.2A as stepping, it is gradually increased from 0.2A to 3.0A, first according to SAP in the present invention
Step obtains Pulsed eddy current testing signal, then establishes least square problem using detection signal according to PIP step, obtains difference
It is detected the inversion result of ferromagnetic component conductivity and relative permeability under amplitude pulse current excitation, and draws out as shown in Figure 2
Conductivity inversion result change curve.And then utilization index function is fitted conductivity inversion result change curve, obtains
To the conductivity of tested steel test block.It is different according to step in the present invention respectively to 10 groups of data of the conductivity measurement of each test block
The conductivity testing result that material tests test block is as shown in table 1.Calculate the average value and mark of each test block conductivity testing result
Quasi- difference is respectively 5.09 ± 0.02MS/m, 6.98 ± 0.04MS/m and 6.95 ± 0.03MS/m.
The conductivity of three pieces of steel test blocks is detected respectively with four probe method, conductivity is respectively 5.16 ±
0.05MS/m, 7.03 ± 0.11MS/m and 6.86 ± 0.08MS/m.As it can be seen that with pulse eddy conductivity detection side in the present invention
Method, it is almost the same to the testing result and four probe method conductivity testing result of ferromagnetic metallic material conductivity, between the two
Deviation maximum 0.09MS/m.Demonstrate the feasibility and reliability of method detection ferromagnetic metallic material conductivity in the present invention.
The conductivity impulse eddy current method testing result unit of 1 unlike material of table experiment test block: MS/m
| Test block material | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | Mean value | Standard deviation |
| 20# steel | 5.11 | 5.09 | 5.11 | 5.08 | 5.09 | 5.03 | 5.07 | 5.08 | 5.10 | 5.11 | 5.09 | 0.02 |
| 45# steel | 7.00 | 6.95 | 6.98 | 6.96 | 6.97 | 6.94 | 6.98 | 6.97 | 6.98 | 7.08 | 6.98 | 0.04 |
| Q235 steel | 6.92 | 6.96 | 6.95 | 6.93 | 6.89 | 6.97 | 6.96 | 6.96 | 7.00 | 6.97 | 6.95 | 0.03 |
Claims (5)
1. a kind of pulse eddy current detection method of ferromagnetic metallic material conductivity, which is characterized in that specific step is as follows:
Step 1: the acquisition of the Pulsed eddy current testing signal of tested ferromagnetic component；
Step 2: the inversion method of tested ferromagnetic component electromagnetic parameter；
Step 3: eliminating influence of the magnetic conductivity variation to conductivity testing result using curve matching.
2. a kind of pulse eddy current detection method of ferromagnetic metallic material conductivity as described in claim 1, which is characterized in that step
The obtaining step of pulse eddy current testing signal in rapid one are as follows:
Coil probe vertical is placed in above tested ferromagnetic component by step SAP-1, hold-in winding probe lift off loIt is constant,
lo=0-20mm；
Step SAP-2, winds excitation coil and detection coil on coil rack, and the of the both ends connection sampling resistor of excitation coil
Two the first AD moduluses of termination of one output end, the output end of the input termination power amplification circuit of sampling resistor, detection coil turn
The input terminal of parallel operation, the second output terminal of current sampling resistor connect the input terminal of the 2nd AD analog-digital converter；
Step SAP-3 is exported with host programming and is continued pulsewidth as 10~500ms, and amplitude is the excitation digital signal of 0.1~1V；
After DA digital analog converter, become to continue pulsewidth to be 10~500ms, amplitude is the excitation analog signal of 0.1~1V, is exported to function
Rate amplifying circuit；After power amplification circuit amplifying power, exports and continue pulsewidth as 10~500ms, amplitude is the arteries and veins of 0.1~5A
Exciting current is rushed, after pulse excitation electric current flows through sampling resistor, supplies excitation coil, I0For pulse excitation current amplitude；
Step SAP-4, the induced voltage time-domain signal u (t) at the first AD analog-digital converter acquisition testing coil both ends, and will acquisition
In obtained induced voltage signal u (t) storage to host；The pulse excitation of sampling resistor both ends is acquired with the 2nd AD analog-digital converter
Signal i (t), and store into host.
3. a kind of pulse eddy current detection method of ferromagnetic metallic material conductivity as described in claim 1, which is characterized in that step
Specific step is as follows for the inversion method of tested ferromagnetic component electromagnetic parameter in rapid two:
Step PIP-1, by coil probe lift-off lo, tested ferromagnetic component wall thickness d and pulse excitation current signal i (t) as
The amount of knowing, while by the relative permeability μ of the conductivityσ of tested ferromagnetic component and tested ferromagnetic componentrIt is set as unknown parameter, that is, is had
Parameter vector x=(x to inverting1,x2)T=(σ, μr)T；
The induced voltage time-domain signal of step PIP-2, the detection coil both ends collected with the first AD analog-digital converter measure
Data are (t1,u1),(t2,u2),…,(tm,um), by calculated value u (x, the t of itself and induced voltagei) compare, enable induced electricity
Press time-domain signal measured value uiError sum of squares minimum between calculated value carrys out inverted parameters x, that is, establishes least square
Problem:
Remember residual function ri(x)=ui-u(x,ti), i=1,2 ..., m, and remember residual functional vector r (x)=(r1(x),r2
(x),...,rm(x))T, R2For two-dimentional real number space, m is the number of measurement, x1And x2Indicate two elements in vector x；
Step PIP-3, using iterative algorithm, solves the optimal solution x of least square problem in host*, the meter of iterative algorithm
Calculate step are as follows:
(1) initial point is givenAllowable error ε > 0, sets k=1；
(2) parameter vector for walking kthIt substitutes into ferromagnetic plate Pulsed eddy current testing model, calculates
The each time point t of kth stepiInduced voltage calculated value u (x(k),ti), then measured with induced voltage time-domain signal
Value uiIt is poor to make, and calculates the residual functional value of kth step
ri(x(k))=ui-u(x(k),ti), i=1,2 ..., m,
And obtain the residual functional vector r of kth step(k)；Then sense is further calculated by ferromagnetic plate Pulsed eddy current testing model
Answer voltage theoretical curve to the first-order partial derivative of the conductivityσ of tested ferromagnetic component
And induced voltage theoretical curve is to the relative permeability μ of tested ferromagnetic componentrFirst-order partial derivative
Obtain the matrix A of m × 2k=(aij)m×2；J=1,2；
(3) solve system of equation
Acquire direction vector b；
(4) the parameter vector x walked from kth(k)It sets out, along the direction vector b of kth step(k)Make linear search, finds out step-length αk, so that
Using α as the function f (x of independent variable(k)+αb(k)) when being minimized, the value of independent variable α is αk；
And it enables
x(k+1)=x(k)+αkb(k)；
(5) if | | x(k+1)-x(k)| |≤ε then stops calculating, and obtains the optimal solution x of least square problem*=x(k+1)；Otherwise, it sets
K:=k+1, return step (2)；
Step PIP-4 is solved the optimal solution of least square problem by above-mentioned iterative algorithmAfterwards, it is detected
The inversion result σ of the conductivity of ferromagnetic component*, it is detected the inversion result of the relative permeability of ferromagnetic componentIt will be detected ferromagnetic
The inversion result and pulsed current excitation amplitude of the relative permeability of the inversion result of the conductivity of component and tested ferromagnetic component
I0It is mapped, is saved in host.
4. a kind of pulse eddy current detection method of ferromagnetic metallic material conductivity as described in claim 1, which is characterized in that step
Curve matching is utilized in rapid three, eliminates influence specific implementation step of the magnetic conductivity variation to conductivity testing result are as follows:
Step 1: the wall thickness d of tested ferromagnetic component is obtained using vernier caliper or audigage measurement, by coil probe vertical
It is placed in above tested ferromagnetic component, the lift off l of coil probe is gone out using ruler or vernier caliper measuremento；
Step 2: the lift off l of fixed coil probeoIt is constant, by pulse excitation current amplitude I0With 0.2A stepping, from 0.2A by
It is gradually increased to 3.0A, and according to step 1, acquires the corresponding detection coil both ends induction of different pulse excitation current amplitudes respectively
The signal of voltage time-domain signal and sampling resistor both ends pulse excitation electric current, is stored in host；
Step 3: according to step 2, being finally inversed by the conductivity of the corresponding tested ferromagnetic component of different amplitude pulse exciting currents respectively
With the relative permeability of tested ferromagnetic component, and draw out tested ferromagnetic component conductivity inversion result with pulse excitation electricity
Flow amplitude I0Change curve；
Step 4: utilization index functionTo the inversion result σ of the conductivity of tested ferromagnetic component*It is quasi- to carry out curve
It closes, to obtain factor sigma in exponential function0With ε fitting resultWithWhereinThe conductivity inspection of as tested ferromagnetic component
Survey result.
5. a kind of Pulsed eddy current testing device of ferromagnetic metallic material conductivity, which is characterized in that the detection device includes line
Probe, host, DA analog-digital converter, power amplification circuit, sampling resistor, the first AD analog-digital converter and the 2nd AD modulus is enclosed to turn
Parallel operation, the coil probe include coil rack, excitation coil and detection coil, and coil probe is placed on tested ferromagnetic component
Side, coil probe the distance between lower edge and tested ferromagnetic component upper surface are denoted as lo, coil probe lower section is detected ferromagnetic structure
The wall thickness of part is denoted as d, and excitation coil and detection coil are wound on coil rack, the output end connection DA digital analog converter of host
Input terminal, the input terminal of the output end connection power amplification circuit of DA digital analog converter, the output end connection of power amplification circuit
The input terminal of sampling resistor, the second output terminal of sampling resistor connect the input terminal of the 2nd AD analog-digital converter, the 2nd AD modulus
Second input terminal of the output end connection host of converter, the both ends of the first output end connection excitation coil of sampling resistor, inspection
The both ends of test coil connect the first AD analog-digital converter input terminal, and the output end of the first AD analog-digital converter connects the first of host
Input terminal, wherein host believes received excitation number to DA digital analog converter output drive digital signal, DA digital analog converter
It number is converted to excitation analog signal and is transferred to power amplification circuit, power amplification circuit is by received excitation analog signal amplification function
Pulse excitation electric current is exported after rate to sampling resistor, sampling resistor supplies excitation coil, detection line after receiving pulse excitation electric current
Circle is by induced voltage analog signal transmission to the first AD analog-digital converter, and the first AD analog-digital converter is by received induced electricity pressing mold
Quasi- signal is converted to induced voltage discrete digital signal and is transferred to host progress as the result is shown.
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