CN204255900U - A kind of electromagnetic nondestructive device of steel part defect - Google Patents

Abstract

An electromagnetic nondestructive device for steel part defect, belongs to technical field of nondestructive testing.Be made up of probe, signal generator, power amplifier, prime amplifier, signal acquisition and processing system; Wherein, pop one's head in and to be made up of " E " type magnetic core, drive coil, the first inductive coil, the second inductive coil, the first permanent magnet, the second permanent magnet, shell; Place the first permanent magnet and the second permanent magnet that parallel with core plane respectively on the both sides of " E " type magnetic core, the magnetic direction that the first permanent magnet and the second permanent magnet are formed in steel part inside and magnetic core magnetic bound conjugate and detection side are to perpendicular; First permanent magnet, the second permanent magnet and " E " type magnetic core are placed on the surface of detection steel part jointly, and agree with the surface of detection steel part.Apparatus structure described in the utility model is simple, low-power consumption, the defect existed under can quick and precisely measuring steel surface and cumulative stress region.

Description

A kind of electromagnetic nondestructive device of steel part defect

Technical field

The utility model belongs to technical field of nondestructive testing, is specifically related to a kind of electromagnetic nondestructive device of steel part defect.

Background technology

Steel are as a kind of Important building material, and it is of a great variety, are widely used in industrial and agricultural production scientific research every field, as oil pipeline, bridge, railway and building etc.Can cause certain cumulative stress in the use procedure of steel part, so that damage breaks to form defect.Especially when defect appears under steel piece surface, because the skin effect of ferrimagnet is more obvious, the more difficult detection of conventional electromagnetic method.Therefore, online Non-Destructive Testing and estimation can be carried out to this type of defect accurately and effectively, very necessary for the safe handling of guarantee steel component, Study on nondestructive detection method field is had great significance.

In the last few years, the lossless detection method development based on electromagnetic theory and technology was rapid, and conventional electromagnetics detection method comprises eddy-current method, Barkhausen Noise, Magnetic Flux Leakage Inspecting method, metal magnetic memory method, magnetic force (effect) method etc.The advantages such as its method and corresponding equipment have noncontact, and measuring speed is very fast, radiationless, in production scientific research field extensive application.

Detection method of eddy is the lossless detection method of modal defect of metallic member, but the skin effect of being limited to, and the method is used for the detection of surperficial gross imperfection.Barkhausen Noise refers to that ferrimagnet is when the external magnetic field magnetization strengthened, and motion that is discontinuous and great-jump-forward occurs domain wall, and the noise signal of generation can reflect materials microstructure structure and stress state to a certain extent.But fathoming of the method is shallow, and the surfaceness etc. of component all has a great impact noise signal.Magnetic Flux Leakage Inspecting method refers to that the stray field of magnetic material fault location can produce respective change, is used for the gross imperfection on test material surface when applying excitation field.In recent years the Tian Guiyun seminar of Britain Newcastle university has made outstanding work in Magnetic Flux Leakage Inspecting field, pulse leakage detection method (pulsed magnetic flux leakage field testing is proposed, PMFL), low-frequency square-wave pulse is adopted to encourage, in conjunction with electromagnetic induction pulse reluctance method (pulsed magnetic reluctance PMR), significantly improve the investigation depth of defect, following several millimeters of surface can be reached.Metal magnetic memory method is that Russian Doubov teaches in proposition in 20 end of the centurys, and it is in fact a kind of leakage field effect of broad sense, and external excitation magnetic field is terrestrial magnetic field, manifests steel part inherent vice and stress distribution situation by material surface stray field.But terrestrial magnetic field can change along with the difference of geographic position and environment, so Magnetic Memory phenomenon will show certain randomness, the method poor reliability.Magnetic method is based on electromagnetic induction principle, obtains the magnetic characteristic curve of ferrimagnet under effect of stress, utilize respective magnetic parameter as: coercive force, remanent magnetism, magnetic permeability, saturation magnetization etc. characterize stress and the defect condition of component.But coil can not be wound on material members when practical application, be difficult to realize on-line measurement.

Utility model content

The purpose of this utility model is to provide a kind of electromagnetic nondestructive device of steel part defect, and apparatus structure described in the utility model is simple, low-power consumption, the defect existed under can quick and precisely measuring steel surface and cumulative stress region.

The electromagnetic nondestructive device of a kind of steel part defect described in the utility model, is made up of probe (1), signal generator (2), power amplifier (3), prime amplifier (4), signal acquisition and processing system (5).Wherein, probe (1) is made up of " E " type magnetic core (6), drive coil (7), the first inductive coil (8), the second inductive coil (9), the first compensating inductance (10), the second compensating inductance (11), the first permanent magnet (12), the second permanent magnet (13), shell (14); Wherein, drive coil (7) is wound in the yoke in the middle of " E " type magnetic core (6), in the yoke that first inductive coil (8) and the second inductive coil (9) are wound on " E " type magnetic core (6) both sides respectively and reversal connection of connecting, especially, the canoe of two inductive coils, material, wire diameter and the number of turn are identical; Two input ends that first inductive coil (8) is connected with the first compensating inductance (10), the second inductive coil (9) connects prime amplifier (4) respectively after connecting with the second compensating inductance (11) carry out preliminary differential amplify; The first permanent magnet (12) and the second permanent magnet (13) that parallel with magnetic core (6) plane (the Y-Z plane namely shown in Fig. 1, X-direction is outside along paper) is being placed respectively with " E " type magnetic core (6) both sides; First permanent magnet (12), the second permanent magnet (13) and " E " type magnetic core (6) are placed on the surface of detection steel part (15) jointly, and agree with (pop one's head in and searching surface fit to greatest extent closely) with the surface of detection steel part (15); The S pole of the first permanent magnet (12) and the N pole (or S pole of the N pole of the first permanent magnet (12) and the second permanent magnet (13)) of the second permanent magnet (13) contact with the surface of detection steel part (15), thus the magnetic direction (X-direction) that the first permanent magnet (12) and the second permanent magnet (13) are formed in steel part inside and magnetic core (6) yoke direction (Z-direction) and detection side perpendicular to (Y direction).The magnetization M direction of the first permanent magnet (12) inside is along ﹢ Z-direction (or ﹣ Z-direction), and the magnetization M direction of the second permanent magnet (13) inside is along ﹣ Z-direction (or ﹢ Z-direction).

Signal generator (2) produces the periodic signal (square wave or sawtooth wave) of certain frequency and amplitude, this periodic signal amplifies (amplifying 2 ~ 100 times) through power amplifier (3) again and is loaded on the drive coil (7) of probe (1), because the first inductive coil (8) and the second inductive coil (9) are series connection reversal connections, so the total output voltage of two inductive coils is ε (t)=ε 1 (t)-ε 2 (t), wherein the induced signal of two inductive coils is respectively ε 1 (t) and ε 2 (t).Carry out preliminary differential amplify through prime amplifier (4) and obtain total output signal U (t)=K ε (t) (K is the gain of prime amplifier (4)); U (t)=K ε (t) obtains comprising the frequency-region signal U (ω) of multiple harmonic after carrying out FFT conversion by signal acquisition and processing system (5) again, the amplitude of each harmonic of this frequency-region signal U (ω) and empirical data are compared, thus obtains the information of steel part depth of defect to be measured and size.

The material of " E " type magnetic core (6) can be ferrite (manganese-zinc ferrite), siliconized plate or amorphous and nano crystal soft magnetic material, permanent magnet material can be ferrite, neodymium iron boron or aluminium nickel cobalt, shell (14) is nonferromagnetic hard material, and other spaces in shell (14) are filled by hard rubber.

Wherein, the frequency of the cyclic pulse signal that signal generator 2 provides is 0.1 ~ 10kHz, and amplitude is 50 ~ 10000mV, and the investigation depth of this device is 1mm ~ 20mm.

Wherein, signal acquisition and processing system (5) is made up of multichannel data collecting card and host computer (PC) and data processing software, and in the less demanding situation of accuracy of detection, available multi-channel oscillograph replaces data collecting card.

The typical sizes of probe 1: long c is 10 ~ 200mm, and wide e is 2 ~ 100mm, and high q is 2 ~ 100mm.The electromagnetic nondestructive device principle of work of steel defect of the present utility model is as follows:

Signal generator (2) provides cyclic pulse signal, and signal is square wave or sawtooth wave.Signal is loaded into the drive coil (7) of probe (1) again via power amplifier (3), power amplifier (3) also can be high power operational amplifier or voltage-current converter circuit.Drive coil inside will produce magnetic flux Φ (t) identical with exciting current i (t) variation tendency, and its form is approximate square waves or sawtooth wave also.μ _ethe equivalent permeability of magnetic core and detection steel part composite magnetic circuit, l _ethe length of magnetic path, N _cand S _cthe number of turn and the sectional area of drive coil respectively.

Φ(t)＝μ _eN _ci(t)S _c/l _e(1)

Due to the E type symmetrical structure of magnetic core, when detecting steel part lower surface zero defect, form two duplicate parallel circuitses by E-type magnetic core both sides yoke and steel part.Ignore leakage field, then magnetic flux Φ 1 (t)=Φ 2 (t)=Φ (t)/2 in first, second inductive coil (8), (9).Due to the existence of drive coil inductance value, exciting current i (t) (square wave or sawtooth wave rising edge or negative edge) when sign mutation forms periodic transient state process, and waveform has certain distortion, but also can carry out Fourier transform:

${\mathrm{\Φ}}_1\left(t\right)={\mathrm{\Φ}}_2\left(t\right)=\underset{n=0}{\overset{\∞}{\mathrm{\Σ}}}[a_n\sin \left(\mathrm{n\ωt}\right)+b_n\cos \left(\mathrm{n\ωt}\right)]---\left(2\right)$

Thus resolve into the harmonic wave of a series of different frequency composition, wherein ω is leading role's frequency of periodic signal.A _n, b _nfor the coefficient of nth harmonic, proportional with harmonic amplitude.For cyclical signal, ordered series of numbers { a _n, { b _nsuccessively decrease, be unfavorable for the detection of higher hamonic wave signal.

The same with other method for electromagnetically measuring, during AC signal detection hardware, can produce skin effect, when signal current density in component decays to 1/e, corresponding skin depth δ is:

$\mathrm{\δ}=\sqrt{\frac{2}{\mathrm{\ω\μ\σ}}}---\left(3\right)$

Wherein, μ, σ are component magnetic permeability and conductivity respectively, and component is ferromagnetic steel, and magnetic permeability μ is comparatively large, so skin depth δ is little, thus limit the degree of depth that electromagnetic method detects steel part.

Probe is provided with two parts permanent magnet (12), (13), and it agrees with detection steel piece surface.The inclined field of hard magnetization is produced like this between permanent magnet, and magnetic direction (along X-axis) is vertical with magnetic core pumping signal direction of magnetization (along Y-axis) (in the yoke of magnetic core, magnetic core pumping signal direction of magnetization is along Z-direction, in steel part, magnetic core pumping signal direction of magnetization is along Y-direction, thus forms a ring texture in Y-Z plane).Although magnetic flux is easy to pass through from steel part, wants when arranging permanent magnet (12) (13) space D suitably, crossing and closely can make magnetic core magnetic saturation, induced signal being diminished, sensitivity decrease.The effect of permanent magnet has the following aspects: 1. producing high-intensity magnetic field between permanent magnet can, by search coverage steel piece surface and nearly surface magnetization extremely saturated or near state of saturation, make near surface detecting area magnetic permeability μ decline.2. because permanent magnet magnetization direction (X-axis) encourages direction of magnetization (Y-axis) vertical with probe, quite create induced magnetic anisotropy at the nearly near surface of steel part, along X-direction, then direction of magnetization Y-axis is encouraged to be hard direction, so decline along the magnetic permeability μ of detection direction steel part.Magnetic permeability declines, and skin depth δ will increase, and induced signal can bring the information of more deep layer.3. the unordered magnetic moment in steel part can be magnetized in the inclined field that permanent magnet applies, and shields stray magnetic field to a certain extent, improves signal quality.4. permanent magnet is fixed on probe, probe can be adsorbed on steel piece surface when measuring, and ensures to apply certain normal pressure when measuring, and probe and steel part are fitted, and ensures accuracy and the repeatability of measurement.

Induced potential in the upper inductive coil (8) of corresponding probe, (9) is:

${\mathrm{\ϵ}}_1\left(t\right)={\mathrm{\ϵ}}_2\left(t\right)=-\frac{\∂{\mathrm{\Φ}}_1\left(t\right)}{\∂t}=\underset{n=0}{\overset{\∞}{\mathrm{\Σ}}}\mathrm{n\ω}[b_n\sin \left(\mathrm{n\ωt}\right)-a_n\cos \left(\mathrm{n\ωt}\right)]---\left(4\right)$

The coefficient of the nth harmonic of ε 1 (t) and ε 2 (t), for cyclical signal ordered series of numbers { n ω a _n, { n ω b _nthan the Fourier expansion ordered series of numbers { a of magnetic flux Φ 1 (t), Φ 2 (t) _n, { b _nsuccessively decreasing compensates to some extent, conveniently carries out Data Analysis Services to higher hamonic wave.

Because inductive coil (8), (9) are series connection reversal connections, so output voltage ε (t)=ε 1 (t)-ε 2 (t)=0 that inductive coil is total.But in fact, inductive coil (8), (9) are difficult to accomplish just the same, the inductance value of its correspondence is L1, L2, so need inductive coil serial adjustable sense (10), (11) respectively, the inductance value of its correspondence is Lc1, Lc2, while guarantee coil resistance is equal, regulate controllable impedance (10), (11), make L1+Lc1=L2+Lc2, the signal that during guarantee zero defect, inductive coil (8), (9) produce is consistent.Controllable impedance (10), (11) are inessential elements, can not want when inductive coil (8), (9) parameter are identical.

When popping one's head in when defect (or cumulative stress region), i.e. magnetic core inductive coil 1 place magnetic circuit steel part part existing defects, defect length is vertical with probe excitation orientation (i.e. detection direction Y direction), along X-direction, as shown in Figure 1, magnetic resistance can increase, and the magnetic flux Φ 1 (t) in inductive coil (8) can reduce.And the magnetic flux Φ 2 (t) in inductive coil (9) can increase.Corresponding inductive coil series connection reversal connection output voltage ε (t)=ε 1 (t)-ε 2 (t) ≠ 0

$\mathrm{\ϵ}\left(t\right)={\mathrm{\ϵ}}_1\left(t\right)-{\mathrm{\ϵ}}_2\left(t\right)=\underset{n=0}{\overset{\∞}{\mathrm{\Σ}}}\mathrm{n\ω}[a\cos \left(\mathrm{n\ωt}\right)-b\sin \left(\mathrm{n\ωt}\right)]---\left(5\right)$

Wherein, a, b are the coefficient that inductive coil (8) (9) induced signal difference each harmonic is corresponding.Because skin effect, different frequency harmonic wave in steel part through the degree of depth different, so different frequency harmonic components contained in inductive coil signal epsilon (t) can reflect the information of steel part depth of defect and size.

Last induced signal carries out preliminary differential amplify through prime amplifier (4), obtains the gain that total output signal U (t)=K ε (t), K is prime amplifier (4).Carry out analyzing and processing by signal acquisition and processing system (5) again, extract signal characteristic quantity at time-domain and frequency-domain, obtain the information of depth of defect and size.Signal acquisition and processing system (5) is that in the less demanding situation of accuracy of detection, multichannel data collecting card can replace with multi-channel oscillograph by multichannel data collecting card and host computer and data processing software System's composition.

When detecting defect, signal acquisition and processing system (5) needs to detect steel part material according to reality, and surfaceness and probe set a series of voltage magnitude, thus judges size and the degree of depth of defect.These threshold values are determined according to the empirical relationship of defect and output.

First be provided with valid value threshold value Urt, as total output signal effective value Urms≤Urt, system assert that steel part zero defect or depth of defect exceed device and detect the degree of depth.Because what in practical application, steel part detection zone surfaceness can affect probe agrees with degree, actual sonde configuration can not ensure full symmetric, so the maximal value that system when also can not be 0, Urt should be steel part zero defect that exports when zero defect exports.

For the defect of same even depth, size is larger, and namely width is wider, and the frequency-region signal exporting U all can increase.For the defect of same width, the degree of depth is more shallow, and namely distance surface is nearer, and the frequency-region signal dominant frequency each harmonic amplitude exporting U is larger.

From above formula with illustrate, the requirement for magnetic flux signal and pumping signal: 1. there is abundant harmonic components; 2. to there is sudden change (rising edge or negative edge), make induced voltage signal large.It is square-wave signal (having a rising edge and a negative edge in one-period) and sawtooth wave (having a rising edge or a negative edge in one-period) that periodic signal meets above-mentioned condition

In addition, many employing " U " type magnetic cores in prior art, when detecting than output signal, change amount signal is very little, and sensitivity is little, so need dual probe structure or signal data difference processing part, but system is comparatively complicated.And the utility model adopts E-type magnetic core, inductive coil series connection reversal connection, except exporting differential signal epsilon (t), is eliminated the invariant exported, is improved the sensitivity of detection; Outside interference can also be offset, because the size of probe is little, inductive coil (8), (9) residing locus can be considered a bit, if disturbing magnetic field is had to exist outside, equal induced signal can be produced two inductive coils (8), (9), but the differential output after series connection reversal connection is cancelled out each other, result is 0, does not have an impact to measurement result.

In addition when apparatus design, probe (1) plane requires to agree with searching surface, can make cambered surface by car, but will keep the axial symmetry along middle yoke when detecting oil pipe; Permanent magnet can make cambered surface, also can be divided into some pieces, contact with searching surface.And the size of probe is wanted suitably, the centre of E-type magnetic core and both sides yoke distance should not have big difference (within 1 order of magnitude) with flaw size to be measured

The electromagnetic nondestructive device of steel part defect of the present utility model, can defect under on-line checkingi steel surface, and measures fast and effectively the degree of depth of defect and width and estimate.Meanwhile, this device can also be used for detecting with or without cumulative stress region under surface.The features such as the utility model relates to device and has structure simply, low in energy consumption, economic and practical, have good application prospect at production scientific research field of non destructive testing.

Accompanying drawing illustrates:

Fig. 1: be steel part defect the cannot-harm-detection device structural representation described in the utility model.

Fig. 2: be probe bottom surface structure schematic diagram described in the utility model.

Wherein, the name of each several part is called probe 1, signal generator 2, power amplifier 3, prime amplifier 4, signal acquisition and processing system 5, " E " type magnetic core 6, drive coil 7, first inductive coil 8, second inductive coil 9, first compensating inductance 10, second compensating inductance 11, first permanent magnet 12, second permanent magnet 13, shell 14, detection steel part 15.

Fig. 3: be output waveform and the device output waveform of inductive coil of popping one's head in when pumping signal is square wave;

The output waveform that figure (a) is inductive coil during steel part zero defect; The output waveform that figure (b) is steel part zero defect timer; Wherein, 1. curve is the output signal of the first inductive coil, and 2. curve is the output signal of the second inductive coil, and two curve shapes are identical, change in the opposite direction; 3. curve is the differential wave (signal 2. subtraction signal 1.) exported after first, second inductive coil series connection reversal connection, namely at the signal before prime amplifier (4); 4. curve is the time-domain signal that measurement mechanism exports; 5. curve is that 4. curve obtains frequency-region signal through FFT change); The output waveform that figure (c) is each inductive coil of popping one's head in during defectiveness, the output waveform that figure (d) is defectiveness timer.The width 5mm of corresponding defect, degree of depth 1mm, the pumping signal that signal source provides is square wave, frequency 100Hz, and amplitude is 400mV; Collecting device is hyperchannel oscillograph.

Fig. 4: for the effective value of defect steel part device output waveform time different depth h (defect width is identical, is 5mm) and each harmonic amplitude of frequency domain are with the relation curve of depth of defect; Wherein, Urms is effective value, and U1 is curve dominant frequency signal 5., U2, U3, U4 be respectively curve 5. in secondary, three times, four-time harmonic signal.Corresponding embodiment 3.

Fig. 5: be output waveform and the device output waveform of inductive coil of popping one's head in when pumping signal is sawtooth wave; Figure (a) is the output waveform of inductive coil of popping one's head in during zero defect, the output waveform that figure (b) is zero defect timer, figure (c) is the output waveform of inductive coil of popping one's head in during defectiveness, the output waveform that figure (d) is defectiveness timer.Wherein, 1., be 2. the output waveform of two inductive coils, being 3. the wave that inductive coil series connection reversal connection exports, is 4. the time-domain signal that measurement mechanism exports, and is 5. the frequency-region signal that measurement mechanism exports.C steel part defect width 5mm that (), (d) are corresponding, degree of depth 1mm.

Embodiment

Embodiment 1: the electromagnetic nondestructive device of steel defect

Design a kind of electromagnetic nondestructive device of steel defect, for the not degree of depth of defect and size under on-line checkingi steel surface.Device comprises probe (1), signal generator (2), power amplifier (3), prime amplifier (4), Signal sampling and processing equipment (5).

Probe (1) is made up of " E " type magnetic core (6), drive coil (7), the first inductive coil (8), the second inductive coil (9), the first compensating inductance (10), the second compensating inductance (11), the first permanent magnet (12), the second permanent magnet (13), shell (14).Wherein, drive coil (7) is wound in the middle yoke of magnetic core (6), be wound in the yoke on the both sides of magnetic core (6) after first inductive coil (8) and the second inductive coil (9) series connection reversal connection, the canoe of two inductive coils, material, wire diameter and the number of turn are identical, first inductive coil (8) and the second inductive coil (9) are connected the first compensating inductance (10) and the second compensating inductance (11) respectively, and the both sides of magnetic core (6) place the first permanent magnet (12) and the second permanent magnet (13) respectively.

" E " type magnetic core (6) is manganese-zinc ferrite material, be of a size of 4mm (wide e) × 18mm (long c) × 8mm (high q), middle yoke and both sides yoke spacing are 5mm, and the number of turn of drive coil (7) is 200 circles, wire diameter 0.08mm.The number of turn of first, second inductive coil (8), (9) is 100 circles, wire diameter 0.1mm.First, second compensating inductance (10), (11) are solenoid inductor, the number of turn is 70 circles, wire diameter 0.5mm, and the magnetic core of compensating inductance is three layers of Fe-based amorphous soft magnetic ribbon material, size 2.5mm × 100mm, can in solenoid type inductance mobile adjusting inductance.First, second permanent magnet (12), (13) material are neodymium iron boron, are of a size of 5mm × 45mm × 3mm, and two permanent magnet space D are 18mm.Shell (14) material is plastic plate.

Signal generator (2) is Agilent 33250A signal generator, power amplifier (3) is high power operational amplifier opa549 (gain is 2), prime amplifier (4) is instrument amplifier AD620 (gain is 9), and signal acquisition and processing system (5) is RIGOL DS1102 oscillograph and PC.Detection steel part material is Q235 steel, size 50mm × 100mm × 10mm.

Embodiment 2: the electromagnetic nondestructive method of steel defect

1) choose the probe of suitable dimension according to the surface condition of steel part to be detected, probe described in embodiment is agreed with the detection surface of steel part.

2) at the zero defect place of steel part, observed the waveform of pumping signal and induced signal in time domain by signal acquisition and processing system (5), frequency and the amplitude of pumping signal (square wave or sawtooth wave) are set, require there is more complete transient state process at the waveform of cycle underexcitation signal.Require that exciting current power is less than the rated power (determined by probe magnetic core and drive coil, exceeded this power magnetic core and drive coil is overheated can damage) of probe (1) and drive coil (7) simultaneously.The gain of power amplifier (3) and prime amplifier (4) is appropriately set.Regulate compensating inductance (10), (11) make inductive coil (8), (9) export waveform consistent, series connection reversal connection output signal ε (t) and total output signal U (t) reach minimum value, are desirably 0.

3) along detection side to (Y-axis) mobile probe, at the defectiveness place of steel part, device has certain signal and exports.At surveyed area, because the agree with degree of steel piece surface roughness to be measured on probe has impact, simultaneously due to probe actual geometirc symmetry axis with detect orientation consistency due to the reason of practical operation vision and have deviation; So also need to adjust angle (within 5 °) among a small circle, make the effective value Urms of output signal U occur minimal value, at this moment think that steel piece surface and probe agree with, measurement data is effective.

4) by Signal sampling and processing equipment (5), output signal U (t) is carried out FFT and be converted to frequency-region signal U (ω), this frequency-region signal comprises dominant frequency signal and multiple harmonic signal.

5) output effective value threshold value Urt is set (because steel piece surface adds and has certain roughness man-hour, probe lower surface in testing process can not completely and steel piece surface agree with, even if so when detecting flawless normal steel part part, the output of probe is non-vanishing, namely device always exports and has certain magnitude of voltage, always the maximum value exported when be exactly this Urt detects normal steel part, export effective value and just think that steel part zero defect or defectiveness but device detect not out when being less than this value), as total output signal effective value Urms≤Urt, assert that steel part zero defect or depth of defect exceed device and detect the degree of depth.When surveying total output signal effective value Urms > Urt, carry out the judgement of defect information.

6) utilize device described in the utility model, first measure the defect steel part of a series of known width and the degree of depth, obtain the experience amplitude matrix A k of frequency-region signal U (ω) each harmonic amplitude _{(n × m)}, need to detect n × m group sample, matrix element ak _ijfor measuring the minimal value of U (ω) amplitude that this group defect sample timer exports, wherein 1≤i≤n, 1≤j≤m, wherein k represents the kth subharmonic of frequency-region signal U (ω), and each harmonic signal all has an amplitude matrix corresponding with it; When the data Biao Shi same defect degree of depth with a line in matrix, along with the increase of defect width, device exports the amplitude of frequency-region signal; In matrix when the data Biao Shi same defect width of same row, along with the increase of depth of defect, device exports the amplitude of frequency-region signal.Meanwhile, a defect array Q is set up _ij,

Wherein, matrix function group element (h _i, w _j), line number i represents the degree of depth h of defect, the degree of depth h of same row element _ientirely identical, along with the degree of depth of the defect of the increase correspondence of i is darker; Columns j (requires that the length of defect is larger than the width of probe according to representing defect width w, namely the spacing of permanent magnet 12,13 is exceeded, and the width of defect is less than the spacing (spacing of middle yoke and side yoke) of magnetic core yoke, therefore the utility model device is under defect length exceedes the condition of permanent magnet spacing, can be used in width and the degree of depth of measuring defect), the width w of same column element _jentirely identical, along with the width of the defect of the increase correspondence of j is larger.The measuring accuracy of the size indication device of (or between column data) residual quantity value (stepping) between row data, and the measuring accuracy of device depends on the precision of signal acquisition and processing system (5) and actual detection case, the precision of signal acquisition and processing system is high, noise suppression effect good, the resolution of steel part flaw size is just high, defect matrix Q _ijdata volume larger, and the detection stepping of the degree of depth of correspondence and width is just little.Otherwise, the low precision of signal acquisition and processing system, the resolution rate variance of steel part flaw size, then defect matrix Q _ijdata volume less, and the detection stepping of the degree of depth of correspondence and width is just large.So this device detects the Precision measurement that can be used for defect, and stepping can reach 0.1mm.Also may be used for the presence or absence of defect or the detection of guestimate defect size.

Then, by each element a1 in the amplitude of the dominant frequency signal U1 of frequency-region signal U (ω) that obtains when measuring unknown width and deep defects and amplitude matrix A 1 _ijcompare.Fixed line number i, if a1 _ij≤ U1 < a1 _{i (j+1)}, then a1 is recorded _ijcorresponding row columns group (i1, j1).I, from 1, compares successively according to order from small to large, finds often capable eligible a1 _ijcorresponding ranks number i, j, form array (i _s1, j _s1), but the columns parameter j in each array can not get identical numerical value with the array columns j previously chosen.By these arrays composition array set S1={ (i _s11, j _s11), (i _s12, j _s12) ..., wherein i _s11=1, i _s12=2 ...In S set 1 array first element i between, and between second element j, do not repeat that (because have same depth, the defect of different in width can not have identical output; Equally, have same widths, the defect of different depth also can not have identical output).If in S1, array is unique, then array (i _s1, j _s1) row i _s1, row j _s1the corresponding degree of depth and width are (at defect matrix Q _ijdefect information is searched according to the row of correspondence and row) be exactly the information that device records defect.

7) if array is unique in array set S1, then by each element value a2 in the amplitude matrix A 2 of the second harmonic signal U2 of frequency-region signal U (ω) that obtains when measuring unknown defect _ijcompare.In like manner, i, from 1, compares successively according to order from small to large, finds often row to meet a2 _ij≤ U1 < a2 _{i (j+1)}time a2 _ijcorresponding ranks number array (i _s2, j _s2).By these arrays composition array set S2={ (i _s21, j _s21), (i _s22, j _s22) ..., wherein i _s21=1, i _s22=2 ..., in like manner in S set 2 array first element i between, and not repeat between second element j.Get the common factor S1 ∩ S2 of S1 and S2, see that whether S1 ∩ S2 array is unique.

If unique, by each element value a3 in the amplitude U of the harmonic signal U3 of frequency-region signal U (ω) that obtains when measuring unknown defect and amplitude matrix A 3 _ijcompare.Array set S3={ (i can be obtained equally _s31, j _s31), (i _s32, j _s32) ..., wherein i _s31=1, i _s32=2 ..., then get S1, the common factor S1 ∩ S2 ∩ S3 of S2 and S3, see that whether S1 ∩ S2 ∩ S3 array is unique.

By that analogy, successively by each element value ak in the k rd harmonic signal Uk of U and amplitude matrix A k _ijcompare, array set Sk={ (i can be obtained _sk1, j _sk1), (i _sk2, j _sk2) ..., wherein i _sk1=1, i _sk2=2 ..., until the array in the common factor of S1 to Sk is unique, then the degree of depth that the ranks of this unique array (i, j) are corresponding and width are exactly the degree of depth and the width that device records defect.If system still exports without definite, then return step 3) repeat.The number k of Sk is determined by data acquisition equipment used in experimental signal acquisition and processing system (5) quality, and data acquisition equipment precision is high, and k can be larger.Data acquisition equipment is poor, and k is just little.If the collecting device in embodiment is hyperchannel oscillograph, precision is poor, is applicable to rough detection, and k can only to 3 or 4, namely can only detect three, four-time harmonic, more than quintuple harmonics detects inaccurate.I in array _skn, j _sknfootmark skn expression by dominant frequency signal or kth rd harmonic signal at amplitude matrix A k _{(n × m)}when n-th line detects, the array obtained.

8) if testing result poor sensitivity, can changing device probe size, return step 1) repeat.According to actual conditions, in experimental signal acquisition and processing system (5), data acquisition equipment used is oscillograph, and measurement result precision is poor, for steel part defect with or without or the guestimate of size.

Embodiment 3:

Utilize the steel part of measurement device known defect size described in the utility model, obtain dominant frequency signal, secondary, three times, the amplitude matrix of four-time harmonic is respectively

$A1=\left(\begin{array}{cc}50& 70\\ 39& 45\\ 15& 21\end{array}\right),A2=\left(\begin{array}{cc}31& 49\\ 23& 29\\ 12& 20\end{array}\right),A3=\left(\begin{array}{cc}20& 39\\ 11& 17\\ 9& 12\end{array}\right),A4=\left(\begin{array}{cc}12& 25\\ 8& 13\\ 5& 9\end{array}\right)......$

Defect matrix Q _{(3 × 2)}, $Q=\left(\begin{array}{cc}\left(\mathrm{1,3}\right)& \left(\mathrm{1,5}\right)\\ \left(\mathrm{5,3}\right)& \left(\mathrm{5,5}\right)\\ \left(\mathrm{9,3}\right)& \left(\mathrm{9,5}\right)\end{array}\right).$

Its line number 1,2,3 is corresponding degree of depth 1mm, 5mm, 9mm respectively, stepping 4mm; The corresponding width of columns 1,2 is 3mm, 5mm, stepping 2mm.

Then device described in the utility model is utilized, measure the steel part (its possible flaw size is the degree of depth 4 ~ 6mm and width 4 ~ 6mm) of a certain unknown flaw size, obtain the frequency-region signal dominant frequency amplitude U1=51mV that its output signal U is corresponding, secondary harmonic amplitude U2=30mV, third harmonic amplitude U3=18mV, four-time harmonic amplitude U3=13mV.

Compare each element a1 in U1 and matrix A 1 _ij, in the first row, the element of 50 < U1 < 70,50 correspondences is a1 ₁₁, so passable to array (1,1); 45 < U1 in a second row, the element of 45 correspondences is a1 ₂₂, so array (2,2) can be obtained.Owing to requiring that in the array set of composition, line number and columns all do not repeat, so can not compare in the third line of matrix A 1, thus obtain array set S1={ (1,1), (2,2) again }.

Because the array in array set S1 is not unique, then need to compare further each element a2 in U2 and matrix A 2 _ijrelation, without qualified element in the first row of matrix A 2.29 < U2 in the second row of matrix A 2, so can obtain a2 ₂₂corresponding array (2,2).I.e. array set S2={ (2,2) }.So common factor S1 ∩ S2=(2,2), result is unique; And then, at defect matrix Q _ijin the 2nd row, the 2nd row corresponding array (5, the 5) degree of depth 5mm that represents and width 5mm, be the degree of depth and the width of steel part to be measured.

When Fig. 4 is for detecting different depth h defect steel part, the effective value of device output signal and frequency-region signal, defect width is 5mm.Under the present embodiment condition, it is 51mV, i.e. Urt=51mV that zero defect steel part detects the maximum effective value exported.Exporting effective value when depth of defect is 9mm is 51.8mV, Urms > Urt, so within the detection degree of depth of this pick-up unit under embodiment incentive condition be approximately 9mm.Effective value, dominant frequency and each harmonic amplitude reduce with the increase of the degree of depth.

For the same degree of depth (1mm), different in width (3mm, 5mm) defect steel part detect time, pick-up unit output signal effective value and each harmonic amplitude of frequency domain in table 1.

Table 1: when steel part has a 3mm and 5mm width defect, the effective value of pick-up unit output signal and frequency-region signal amplitude

(mV)	5mm is wide	3mm is wide
			Urms	167	106
U1	79	66
			U2	50	32
U3	40	21
			U4	25	12

Wherein, Urms is effective value, and U1 is dominant frequency signal 5., U2, U3, U4 be respectively 5. in secondary, three times, four-time harmonic signal.

Claims (8)

1. an electromagnetic nondestructive device for steel part defect, is characterized in that: be made up of probe (1), signal generator (2), power amplifier (3), prime amplifier (4), signal acquisition and processing system (5); Wherein, probe (1) is made up of " E " type magnetic core (6), drive coil (7), the first inductive coil (8), the second inductive coil (9), the first permanent magnet (12), the second permanent magnet (13), shell (14); Drive coil (7) is wound in the yoke in the middle of " E " type magnetic core (6), in the yoke that the first inductive coil (8) and the second inductive coil (9) are wound on " E " type magnetic core (6) both sides respectively and reversal connection of connecting; Two input ends that first inductive coil (8) and the second inductive coil (9) connect prime amplifier (4) respectively carry out preliminary differential amplify; Place respectively on the both sides of " E " type magnetic core (6) and first permanent magnet (12) of magnetic core (6) plane parallel and the second permanent magnet (13), the magnetic direction that the first permanent magnet (12) and the second permanent magnet (13) are formed in steel part inside and magnetic core (6) yoke direction and detection side are to perpendicular; First permanent magnet (12), the second permanent magnet (13) and " E " type magnetic core (6) are placed on the surface of detection steel part (15) jointly, and agree with the surface of detection steel part (15); Signal generator (2) produces the periodic signal of certain frequency and amplitude, and this periodic signal is loaded on the drive coil (7) of probe (1) after power amplifier (3) amplifies.

2. the electromagnetic nondestructive device of a kind of steel part defect as claimed in claim 1, is characterized in that: the first inductive coil (8) is all identical with the second inductive coil (9) canoe, material, wire diameter and the number of turn.

3. the electromagnetic nondestructive device of a kind of steel part defect as claimed in claim 1, it is characterized in that: be also provided with the first compensating inductance (10) and the second compensating inductance (11), the first inductive coil (8) and the second inductive coil (9) connect two input ends of prime amplifier (4) more respectively after connecting with the first compensating inductance (10) and the second compensating inductance (11) respectively.

4. the electromagnetic nondestructive device of a kind of steel part defect as claimed in claim 1, is characterized in that: the material of " E " type magnetic core (6) is ferrite, siliconized plate or amorphous and nano crystal soft magnetic material.

5. the electromagnetic nondestructive device of a kind of steel part defect as claimed in claim 1, is characterized in that: the material of permanent magnet is ferrite, neodymium iron boron or aluminium nickel cobalt.

6. the electromagnetic nondestructive device of a kind of steel part defect as claimed in claim 1, is characterized in that: the material of shell (14) is nonferromagnetic hard material, and other spaces in shell (14) are filled by hard rubber.

7., as the electromagnetic nondestructive device of a kind of steel part defect of claim 1 ~ 6 as described in any one, it is characterized in that: signal generator (2) is Agilent 33250A signal generator; Power amplifier (3) for high power operational amplifier opa549, gain be 2; Prime amplifier (4) is instrument amplifier AD620, and gain is 9; Signal acquisition and processing system (5) is RIGOL DS1102 oscillograph and PC.

8. as the electromagnetic nondestructive device of a kind of steel part defect of claim 1 ~ 6 as described in any one, it is characterized in that: signal generator (2) provides cyclic pulse signal, signal is square wave or sawtooth wave, and frequency is 0.1 ~ 10kHz, and amplitude is 50 ~ 10000mV.