CN106645391A - Multi-frequency eddy current testing system and method for evaluating carbon fiber plate defect depth - Google Patents

Multi-frequency eddy current testing system and method for evaluating carbon fiber plate defect depth Download PDF

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CN106645391A
CN106645391A CN201610885548.8A CN201610885548A CN106645391A CN 106645391 A CN106645391 A CN 106645391A CN 201610885548 A CN201610885548 A CN 201610885548A CN 106645391 A CN106645391 A CN 106645391A
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signal
frequency
depth
defect
module
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裘进浩
季宏丽
徐笑娟
程军
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Nanjing University of Aeronautics and Astronautics
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Nanjing University of Aeronautics and Astronautics
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/72Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables
    • G01N27/82Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables for investigating the presence of flaws
    • G01N27/90Investigating 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 multi-frequency eddy current testing system and method for evaluating carbon fiber plate defect depth. The system comprises a composite-material to-be-tested part, a multi-frequency sine excitation signal generating module, an eddy current sensing unit, a signal processing and separating module, a signal collecting module and a depth inversion module, wherein the eddy current sensing unit comprises a transmission cable, a probe control mechanism, an eddy current excitation coil and an eddy current detecting coil; the signal processing and separating module comprises a pre-amplifier and a multi-frequency detecting signal separating module. The multi-frequency eddy current testing system and method for evaluating the carbon fiber plate defect depth has the advantage that defect size information is obtained by measuring the peak sensing voltage and peak frequency of different-depth defects, and accordingly the defect depth of composite plates can be evaluated.

Description

A kind of multi frequency detection system and detection for assessing carbon fiber board depth of defect Method
Technical field:
The present invention relates to CFRP NDT for Composite Materials field, more particularly to it is a kind of scarce for assessing carbon fiber board The multi frequency detection system of sunken depth and detection method.
Background technology:
Carbon fibre composite is a kind of new structural material that middle 1960s emerge, with other composite woods The incomparable superior function of material, has obtained widely applying in fields such as civilian industry, military affairs, Aero-Space.It is multiple to ensure Condensation material component disclosure satisfy that each to use requirement, and the internal soundness for monitoring composite structure is widely closed by increasingly Note.
At present, realizing the method for CFRP NDT of composite mainly has:Ultrasonic wave, acoustic resistance, ray and infrared ray side Method is detected, but these methods respectively have deficiency for the detection of carbon fibre composite, and what is had needs couplant, some equipment volumes Greatly, it is expensive, it is only used for workshop detection of offing normal.
EDDY CURRENT is a kind of efficiently contactless Dynamic Non-Destruction Measurement, without the need for couplant, high degree of automation.Due to whirlpool Stream detection is realized based on electromagnetic induction principle, and probe need not be contacted with measured piece, thus structure will not be produced and appointed What affects.Conventional vortex detection technique is worked using single-frequency, and the information content of acquisition is limited, it is impossible to met to depth of defect Assessment.Multi frequency detection technology is according to detected object feature, while apply multiple frequency excitation eddy current probes, according to the skin that becomes Effect obtains parameter to be checked different responses at each frequency, and by orthogonal lock-in-amplifier device, least square method etc. feature is extracted Parameter, and then can be the quality control of composite element according to the depth information of the amplitude inversion defect of multifrequency Eddy signal Foundation is provided.
The content of the invention:
For the problems referred to above, the purpose of the present invention is to propose to a kind of multifrequency Eddy for assessing carbon fiber board depth of defect Detecting system and detection method, according to Kelvin effect, the method is reached by applying, is realized to CFRP composite properties and damage The identification of wound, easy to operate, testing result is visual and understandable, and sensitivity is high, is adapted to online, In-service testing.
The present invention is adopted the following technical scheme that:A kind of multi frequency detection system for assessing carbon fiber board depth of defect System, it is characterised in that:There is module, currents sensing unit, transmission including composite test specimen to be measured, multifrequency sine pumping signal Cable, signal transacting and separation module, signal acquisition module and Depth Inverse module, the currents sensing unit is by control of popping one's head in Machine, vortex excitation coil and test coil of eddy current composition, signal transacting and separation module include preamplifier and multi-frequency testing Signal separation module, the output that the multifrequency sine pumping signal occurs module delivers to respectively vortex excitation coil by transmission cable With multi-frequency testing signal separation module, probe controlling organization is connected with excitation coil and test coil of eddy current is vortexed, EDDY CURRENT The output signal of coil premenstrual being put be connected with the input all the way of multi-frequency testing signal separation module after amplifier amplification output, signal The acquisition module signal that exported by multi-frequency testing signal separation module of collection simultaneously sends into Depth Inverse module.
Further, the preamplifier exports detection coil electric signal is amplified, export after filtering, described many On the one hand frequency detection signal separation module receives the electric signal exported by preamplifier, on the other hand receives and is swashed by multifrequency sine The signal source reference signal of signal generating module output is encouraged, if detection signal and reference signal same frequency, multi-frequency testing signal Separation module output obtains low frequency signal after LPF, conversely, non-output signal.
Further, the multi-frequency testing signal separation module realized by orthogonal lock-in-amplifier module, orthogonal lock-in-amplifier Module includes phase-sensitive detector and low pass filter, and the signal of test coil of eddy current output is amplified to be sent together with reference signal Enter phase-sensitive detector, filtered after high frequency item using low pass filter, obtain the amplitude and phase information of detection signal.
Further, the analog voltage signal Jing A/D exported after separation conversions are sent into depth by the signal acquisition module Processed in inverting module, analyzed, extracted the maximum Δ V and corresponding frequency f of peak point of induced voltage variable quantityg
Further, maximum Δ V and peak point of the Depth Inverse module according to the induced voltage variable quantity for extracting Corresponding frequency fg, by reverse transmittance nerve network, set up maximum Δ V, corresponding frequency f of peak point of voltage varietyg And the relation between correspondence depth of defect D:D=F (Δ V, fg)。
Further, the transmission cable adopts coaxial cable, by inner wire, insulating barrier, aluminum foil shielded, braid shielded box Sheath is constituted, and its length is less than 1m, and parasitic capacitance is less than 100pF/m.
Further, the vortex excitation coil and test coil of eddy current adopt open circles annulus, left-right situs Send-receive formula eddy current probe is constituted, the vortex excitation coil and test coil of eddy current are separated at intervals.
Further, the probe controlling organization compresses probe using flexure spring mechanism, make eddy current probe all the time with it is multiple Condensation material surface of test piece laminating to be measured, the vortex excitation coil converts electrical signals to magnetic signal and is coupled to composite to be treated In test block, test coil of eddy current receives the magnetic signal of change and is converted to electric signal.
The present invention is also adopted the following technical scheme that:A kind of multi frequency detection for assessing carbon fiber board depth of defect is examined Survey method, comprises the steps:
Step one:The eddy current signal characteristic parameter in composite test specimen to be measured is extracted, is obtained by straight line scanning mode First internal flaw, at different frequencies induced voltage change curve, extracts the crest voltage Δ V in amplitude-distance Curve figure With corresponding frequency f of peak pointg
Step 2:Using same procedure, the crest voltage Δ V caused by the second internal flaw is extracted*It is corresponding with peak point Frequency fg *
Step 3:The two groups of signals for extracting are drawn into curve, crest voltage Δ V increases with the increase of depth of defect, The frequency of correspondence peak point also increases therewith;
Step 4:Depth Inverse module is corresponding according to the maximum Δ V and peak point of the induced voltage variable quantity for extracting Frequency fg, carry out by the way of neutral net using being built, specifically include:
Input layer is built, the variable of input layer includes the maximum Δ V of output induced voltage variable quantity, and peak point is corresponding Frequency fg
Hidden layer is built, hidden layer includes the neuron of 3 or more than 3;
Output layer is built, output layer is depth of defect D;Build reverse neural network;
The maximum Δ V and peak point of the induced voltage variable quantity caused by composite test specimen defect to be measured is corresponding Frequency fgSubstitute into input layer;Depth of defect D is substituted into into output layer, neural metwork training is carried out, training result is obtained;
Step 5:According to training result, maximum Δ V, corresponding frequency f of peak point of voltage variety are set upgWith it is right Answer the relation between depth of defect D:D=F (Δ V, fg);
Step 6:Obtain the signal caused by defect in composite test specimen to be measured using multi frequency detection system to become Change, extract characteristic parameter:The maximum Δ V of induced voltage variable quantity and corresponding frequency f of peak pointg, substitute into trained In neural network input layer, the depth information of defect in composite test specimen to be measured is obtained.
Further, there is module as generation multiple-frequency signal excitation eddy current probe in the multifrequency sine pumping signal, its Middle generation double frequency excitation signal, concrete steps include:
Using two-way DDS chip AD9958, four tunnel output signals are produced;
Each AD9958's wherein exports all the way the input for being respectively fed to follow-up multi-frequency testing signal separation module, in addition Two-way output then produces two-frequency signal by add operation Jing mixing;
Two-frequency signal after mixing excitation vortex excitation coil Jing after drive circuit output produces magnetic field.
The present invention has the advantages that:The present invention is used to assess the multi frequency detection side of carbon fiber board depth of defect Method includes:The generation of multifrequency Eddy signal, the eddy current signal obtained in composite structure, multi-frequency testing Signal separator, removal Noise and lift-off bias, carry out feature signal extraction, obtain corresponding crest frequency under different depth, assess composite to be measured Depth of defect in structure.Wherein, multifrequency Eddy signal is produced using the method for synchronization, and single frequency sinusoidal signal is produced by DDS, and The mixing of signal is carried out using adder;Signal transmission adopts coaxial cable, reduces noise jamming and loss;Probe control Mechanism compresses probe using flexure spring mechanism, is allowed to be fitted with composite surface of test piece to be measured, reduces lift-off interference;Signal Process and separation module by detection probe output signal is amplified, filtering, export after frequency separation;Signals collecting and Depth Inverse Module carries out defect inverting for obtaining the output signal that lock mutually amplifies, and extracting characteristic parameter.The multifrequency Eddy method passes through structure Build maximum Δ v, corresponding frequency f of peak point of the induced voltage variable quantity caused by defectgAnd the pass between depth of defect D System, obtains the depth information of defect in composite test specimen to be measured, and the quality control for composite element provides foundation.
Description of the drawings:
Fig. 1 is the present invention for assessing the multi frequency detection system architecture diagram of carbon fiber board depth of defect.
Fig. 2 is composite structure internal flaw position view in the present invention.
Fig. 3 is that multifrequency Eddy is produced and signal transacting schematic diagram in the present invention.
Fig. 4 is the line scanning knot of the first underbead crack defect induced voltage amplitude variations at different frequencies in the present invention Fruit is schemed.
Fig. 5 is that the relation between the induced voltage characteristic parameter of different depth internal flaw in the present invention and scan frequency is bent Line chart.
Fig. 6 is the schematic diagram of reverse neural network in the present invention.
Specific embodiment:
The present invention program is described in detail below in conjunction with accompanying drawing.Following examples are with technical solution of the present invention as front Carry and being implemented, give specific embodiment and operating process, but the scope of protection of the invention is not limited to following enforcements Example.
As shown in figure 1, being the multi frequency detection system knot provided by the present invention for assessing carbon fiber board depth of defect Structure block diagram.It is understandable to enable the above-mentioned purpose of the present invention, feature to become apparent from, below in conjunction with the accompanying drawings with specific implementation method pair The present invention is described in further detail.
The present invention includes composite test specimen to be measured for the multi frequency detection system for assessing carbon fiber board depth of defect 101st, there is module 102, currents sensing unit 103, transmission cable 104, signal transacting and splitting die in multifrequency sine pumping signal Block 108, signal acquisition module 111 and Depth Inverse module 112.Wherein currents sensing unit 103 is by transmission cable 104, probe Controlling organization 105, vortex excitation coil 106 and test coil of eddy current 107 are constituted, and signal transacting and separation module 108 are including front Put amplifier 109 and multi-frequency testing signal separation module 110.
Wherein, the output that multifrequency sine pumping signal occurs module 102 delivers to respectively vortex excitation line by transmission cable 104 Circle 106 and multi-frequency testing signal separation module 110, probe controlling organization 105 and vortex excitation coil 106 and test coil of eddy current 107 are connected, for adjusting eddy current probe position and lift-off;The premenstrual amplifier 109 of putting of the output signal of test coil of eddy current 107 is put It is connected with the input all the way of multi-frequency testing signal separation module 110 after big output;Signal acquisition module 111 is gathered by multi-frequency testing The signal of the output of signal separation module 110 simultaneously sends into Depth Inverse module 112.
Electric signal that the preamplifier 109 exports detection coil 107 is amplified, export after filtering, the multifrequency On the one hand detection signal separation module 110 receives the electric signal exported by preamplifier 109, on the other hand receives by multifrequency just There is the signal source reference signal of the output of module 102 in string pumping signal, if detection signal and reference signal same frequency, multifrequency inspection Survey signal separation module 110 is exported and obtain after LPF low frequency signal (being approximately direct current signal), conversely, without output letter Number.
Multi-frequency testing signal separation module 110 is realized that orthogonal lock-in-amplifier module is mainly wrapped by orthogonal lock-in-amplifier module Containing phase-sensitive detector and low pass filter, the signal of the output of test coil of eddy current 107 is amplified to be sent into together with reference signal Phase-sensitive detector, is filtered after high frequency item using low pass filter, obtains the amplitude and phase information of detection signal.
The analog voltage signal Jing A/D exported after separation conversions are sent into Depth Inverse module 112 by signal acquisition module 111 In processed, analyzed, extract the maximum Δ V and corresponding frequency f of peak point of induced voltage variable quantityg
Maximum Δ V and peak point corresponding frequency of the Depth Inverse module 112 according to the induced voltage variable quantity for extracting fg, by reverse transmittance nerve network, set up maximum Δ V, corresponding frequency f of peak point of voltage varietygWith correspondence defect Relation between depth D:D=F (Δ V, fg);
According to the relation between the voltage variety and depth of defect under different crest frequencies, composite knot to be measured is assessed Depth of defect in structure.
Composite test specimen 101 to be measured carries out crackle before test in Crack Damage form as research object to carbon fiber board Defect makes.The present embodiment is with the underbead crack defect of two different depths (respectively in the first underbead crack defect and second Portion's crack defect) as a example by, as shown in Figure 2.
There is module 102 and be used as to produce multiple-frequency signal excitation eddy current probe in multifrequency sine pumping signal, optional as one kind Embodiment, as a example by the present embodiment is to produce double frequency excitation signal, concrete steps include:
Using two-way DDS chip AD9958, four tunnel output signals are produced;
Each AD9958's wherein exports all the way the input for being respectively fed to follow-up multi-frequency testing signal separation module 110, Two-way output in addition then produces two-frequency signal by add operation Jing mixing;
Two-frequency signal after mixing excitation vortex excitation coil 106 Jing after drive circuit output produces magnetic field, such as Fig. 3 institutes Show.
Transmission cable 104 adopts coaxial cable, is made up of inner wire, insulating barrier, aluminum foil shielded, braid shielded box sheath, Its length is less than 1m, and parasitic capacitance is less than 100pF/m, effectively reduces noise jamming, reduces loss.Signal Jing transmission cables 104 transmission, controlling organization 105 of popping one's head in is responsible for the detection height of two probes of adjustment, is compressed using flexure spring mechanism and is popped one's head in, and leads to Three-dimensional regulation is crossed, makes eddy current probe fit with the composite surface of test specimen 101 to be measured all the time, reduce Lift-off effect to testing result Impact.Vortex excitation coil 106 converts electrical signals to magnetic signal and is coupled in composite test specimen 101 to be measured, is vortexed Detection coil 107 receives the magnetic signal of change and is converted to electric signal.
Vortex excitation coil 106 and test coil of eddy current 107 adopt open circles annulus, and left-right situs are constituted to be sent out Penetrate-receiving type eddy current probe;There is a determining deviation between vortex excitation coil 106 and test coil of eddy current 107, it is to avoid vortex inspection The magnetic field of test coil 107 is disturbed by being vortexed the magnetic field of excitation coil 106, affects accuracy of detection.
The present invention is used to assess the multifrequency eddy current testing method of carbon fiber board depth of defect, comprises the steps:
Step one:The eddy current signal characteristic parameter in composite test specimen 101 to be measured is extracted, is obtained by straight line scanning mode The first internal flaw 1 is taken, as shown in Fig. 2 induced voltage change curve at different frequencies, corresponding scanning result such as Fig. 4 It is shown, extract the crest voltage Δ V and corresponding frequency f of peak point in amplitude-distance Curve figureg
Step 2:Using same procedure, the crest voltage Δ V caused by the second internal flaw 2 is extracted*It is corresponding with peak point Frequency fg *
Step 3:The two groups of signals for extracting are drawn into curve, as shown in figure 5, increasings of the crest voltage Δ V with depth of defect Plus and increase, correspondence peak point frequency also increase therewith.
Step 4:Depth Inverse module 112 is corresponding with peak point according to the maximum Δ V of the induced voltage variable quantity for extracting Frequency fg, carry out by the way of neutral net using being built, specifically include:
Input layer is built, the variable of the input layer includes the maximum Δ V of output induced voltage variable quantity, peak point pair Frequency f answeredg
Hidden layer is built, hidden layer includes the neuron of 3 or more than 3;
Output layer is built, output layer is depth of defect D;The reverse neural network of structure is as shown in Figure 6;
By the maximum Δ V and corresponding frequency f of peak point of the induced voltage variable quantity caused by multiple material board defect to be measuredg Substitute into the input layer;The depth of defect D is substituted into into the output layer, neural metwork training is carried out, training result is obtained;
Step 5:According to training result, maximum Δ V, corresponding frequency f of peak point of voltage variety are set upgWith it is right Answer the relation between depth of defect D:D=(Δ V, fg);
Step 6:The signal caused by defect in composite test specimen 101 to be measured is obtained using multi frequency detection system Change, extracts characteristic parameter:The maximum Δ V of induced voltage variable quantity and corresponding frequency f of peak pointg, substitute into through training Neural network input layer in, obtain the depth information of defect in composite test specimen 101 to be measured.
The above is only the preferred embodiment of the present invention, it is noted that for the ordinary skill people of the art For member, some improvement can also be made under the premise without departing from the principles of the invention, these improvement also should be regarded as the present invention's Protection domain.

Claims (10)

1. a kind of multi frequency detection system for assessing carbon fiber board depth of defect, it is characterised in that:Including composite Test specimen (101) to be measured, multifrequency sine pumping signal occur module (102), currents sensing unit (103), transmission cable (104), Signal transacting and separation module (108), signal acquisition module (111) and Depth Inverse module (112), the currents sensing unit (103) by probe controlling organization (105), vortex excitation coil (106) and test coil of eddy current (107) constitute, signal transacting and Separation module (108) includes preamplifier (109) and multi-frequency testing signal separation module (110), the multifrequency sine excitation The output of signal generating module (102) delivers to respectively vortex excitation coil (106) and multi-frequency testing signal by transmission cable (104) Separation module (110), probe controlling organization (105) is connected with vortex excitation coil (106) and test coil of eddy current (107), whirlpool Stream detection coil (107) output signal it is premenstrual put amplifier (109) amplify output after with multi-frequency testing signal separation module (110) input all the way is connected, and signal acquisition module (111) gathers the letter exported by multi-frequency testing signal separation module (110) Number and send into Depth Inverse module (112).
2. it is used to as claimed in claim 1 assess the multi frequency detection system of carbon fiber board depth of defect, it is characterised in that: Electric signal that the preamplifier (109) exports detection coil (107) is amplified, export after filtering, the multi-frequency testing Signal separation module (110) on the one hand receives the electric signal exported by preamplifier (109), on the other hand receives by multifrequency just There is the signal source reference signal of module (102) output in string pumping signal, if detection signal and reference signal same frequency, multifrequency Detection signal separation module (110) output obtains low frequency signal after LPF, conversely, non-output signal.
3. it is used to as claimed in claim 2 assess the multi frequency detection system of carbon fiber board depth of defect, it is characterised in that: The multi-frequency testing signal separation module (110) is realized that orthogonal lock-in-amplifier module includes phase sensitivity by orthogonal lock-in-amplifier module Wave detector and low pass filter, the signal of test coil of eddy current (107) output is amplified to send into together phase sensitivity with reference signal Wave detector, is filtered after high frequency item using low pass filter, obtains the amplitude and phase information of detection signal.
4. it is used to as claimed in claim 3 assess the multi frequency detection system of carbon fiber board depth of defect, it is characterised in that: The analog voltage signal Jing A/D exported after separation conversions are sent into Depth Inverse module (112) by the signal acquisition module (111) In processed, analyzed, extract the maximum Δ V and corresponding frequency f of peak point of induced voltage variable quantityg
5. it is used to as claimed in claim 4 assess the multi frequency detection system of carbon fiber board depth of defect, it is characterised in that: Maximum Δ V and peak point corresponding frequency f of the Depth Inverse module (112) according to the induced voltage variable quantity for extractingg, By reverse transmittance nerve network, maximum Δ V, corresponding frequency f of peak point of voltage variety are set upgWith correspondence defect depth Relation between degree D:D=F (Δ V, fg)。
6. it is used to as claimed in claim 5 assess the multi frequency detection system of carbon fiber board depth of defect, it is characterised in that: The transmission cable (104) adopts coaxial cable, is made up of inner wire, insulating barrier, aluminum foil shielded, braid shielded box sheath, its Length is less than 1m, and parasitic capacitance is less than 100pF/m.
7. it is used to as claimed in claim 6 assess the multi frequency detection system of carbon fiber board depth of defect, it is characterised in that: Vortex excitation coil (106) and test coil of eddy current (107) adopt open circles annulus, and left-right situs are constituted to be sent out - receiving type eddy current probe is penetrated, the vortex excitation coil (106) and test coil of eddy current (107) are separated at intervals.
8. it is used to as claimed in claim 7 assess the multi frequency detection system of carbon fiber board depth of defect, it is characterised in that: Probe controlling organization (105) is compressed using flexure spring mechanism to be popped one's head in, and makes eddy current probe to be tested with composite all the time Part (101) surface is fitted, and vortex excitation coil (106) converts electrical signals to magnetic signal and to be coupled to composite to be measured In test specimen (101), test coil of eddy current (107) receives the magnetic signal of change and is converted to electric signal.
9. a kind of multi frequency detection detection method for assessing carbon fiber board depth of defect, it is characterised in that:Including as follows Step:
Step one:The eddy current signal characteristic parameter in composite test specimen (101) to be measured is extracted, is obtained by straight line scanning mode First internal flaw (1), at different frequencies induced voltage change curve, extracts the crest voltage in amplitude-distance Curve figure Δ V and corresponding frequency f of peak pointg
Step 2:Using same procedure, the crest voltage Δ V caused by the second internal flaw (2) is extracted*It is corresponding with peak point Frequency fg *
Step 3:The two groups of signals for extracting are drawn into curve, crest voltage Δ V increases with the increase of depth of defect, correspondence The frequency of peak point also increases therewith;
Step 4:Depth Inverse module (112) is corresponding according to the maximum Δ V and peak point of the induced voltage variable quantity for extracting Frequency fg, carry out by the way of neutral net using being built, specifically include:
Input layer is built, the variable of input layer includes the maximum Δ v of output induced voltage variable quantity, the corresponding frequency of peak point fg
Hidden layer is built, hidden layer includes the neuron of 3 or more than 3;
Output layer is built, output layer is depth of defect D;Build reverse neural network;
The maximum Δ V of the induced voltage variable quantity that will be caused by composite test specimen to be measured (101) defect is corresponding with peak point Frequency fgSubstitute into input layer;Depth of defect D is substituted into into output layer, neural metwork training is carried out, training result is obtained;
Step 5:According to training result, maximum Δ V, corresponding frequency f of peak point of voltage variety are set upgWith correspondence defect Relation between depth D:D=F (Δ V, fg);
Step 6:Obtain the signal caused by defect in composite test specimen (101) to be measured using multi frequency detection system to become Change, extract characteristic parameter:The maximum Δ V of induced voltage variable quantity and corresponding frequency f of peak pointg, substitute into trained In neural network input layer, the depth information of defect in composite test specimen to be measured (101) is obtained.
10. it is used to as claimed in claim 9 assess the multi frequency detection detection method of carbon fiber board depth of defect, its feature It is:There is module (102) as multiple-frequency signal excitation eddy current probe is produced in the multifrequency sine pumping signal, wherein producing double Frequency pumping signal, concrete steps include:
Using two-way DDS chip AD9958, four tunnel output signals are produced;
Each AD9958's wherein exports all the way the input for being respectively fed to follow-up multi-frequency testing signal separation module (110), separately Outer two-way output then produces two-frequency signal by add operation Jing mixing;
Excitation vortex excitation coil (106) Jing after drive circuit output of two-frequency signal after mixing produces magnetic field.
CN201610885548.8A 2016-10-10 2016-10-10 Multi-frequency eddy current testing system and method for evaluating carbon fiber plate defect depth Pending CN106645391A (en)

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