CN102661998A - Electromagnetic acoustic emission nondestructive detection method of metal thin board and device thereof - Google Patents

Abstract

The invention provides an electromagnetic acoustic emission nondestructive detection method of a metal thin board and a device of the method, which utilize an acoustic emission technology to test a metal material. The detection method comprises the following steps that: pulsed eddy current generated by an eddy current generator is loaded to the metal thin board to be detected; if the metal thin board to be detected has cracks, acoustic emission signals are simulated; the acoustic emission signals are detected and collected by using four piezoelectric sensors, are input to a preamplifier through signal wires for amplification, and are input to a PC (Personal Computer) machine; the PC machine carries out two-dimensional time-difference positioning according to the collected acoustic emission signals; and a crack defect existing in the metal thin board to be detected is detected through positioning. The used device comprises the eddy current generator, the four piezoelectric transducers, the preamplifier and the PC machine. With the adoption of the electromagnetic acoustic emission nondestructive detection method of the metal thin board provided by the invention, the defects that the conventional electromagnetic detection method cannot obtain material fault active state information through detection, and the difficult problem that the conventional acoustic emission detection technology is difficult to extract a material partial fault weak signal from an entire signal, can be overcome.

Description

A kind of electromagnetic sound emission lossless detection method and device thereof of sheet metal

Technical field

Technical scheme of the present invention relates to utilizes sound wave emissions technical testing metal material, specifically a kind of electromagnetic sound of sheet metal emission lossless detection method and device thereof.

Background technology

Electromagnetic detection is the experimental technique that electricity, magnetic property or the material response characteristic of utilizing material under electromagnetic action, to show (concentrating characteristic or acoustic emission characteristic like vibration characteristics, stress) judged relevant performance of material and defective; Can realize noncontact Non-Destructive Testing to fault in material; Have advantages such as highly sensitive and detection speed be fast, be widely used in manufacturing industry, space flight and aviation, petrochemical complex and other each industrial circles.Based on the electromagnetic detection principle method that fault in material detects is mainly contained conventional eddy current detection method, far-field vortex checking method, magnetic memory detecting method, flux-leakage detection method, low frequency electromagnetic field detection method, microwave detection method and current potential detection method in the prior art; These methods have a common weak point to be; It is detected to be the static characteristics of fault in material, can't obtain the moving state information of fault in material.

On the other hand; The acoustic emission testing technology of fault in material is that industry is known with its high sensitivity and dynamic monitoring characteristic; But there is a difficult problem that is difficult to from overall signal, extract material local defect feeble signal in existing acoustic emission testing technology always; For the commercial Application of reality, this has greatly limited the confidence level and the range of application of acoustic emission testing technology.

How Electromagnetic Testing Technology and acoustic emission are combined,,, become an important research direction to be suitable for actual commercial Application with difficulty and the complexity of handling at the prerequisite decline low signal that keeps the acoustic emission advantage.

Summary of the invention

Technical matters to be solved by this invention is: electromagnetic sound emission lossless detection method and device thereof that a kind of sheet metal is provided; Be a kind of electromagnetic nondestructive method and device thereof of the sheet metal based on eddy current excitation acoustic emission, overcome existing electromechanical detection method and can't detect the deficiency of the moving state information that obtains fault in material and the difficult problem that is difficult to from overall signal, extract material local defect feeble signal that existing acoustic emission testing technology exists.

The present invention solves this technical problem the technical scheme that is adopted: a kind of electromagnetic sound emission lossless detection method of sheet metal; Be a kind of electromagnetic nondestructive method of the sheet metal based on eddy current excitation acoustic emission, the steps include: impulse eddy current is loaded on the sheet metal to be detected, if there is crackle in sheet metal to be detected; Can be inspired acoustic emission signal; Detect and gather this acoustic emission signal, transmit acoustic emission signal, detected acoustic emission signal is amplified; Carry amplifying signal, carry out data acquisition and processing and obtain a result; Concrete operations are; Drive coil in the vortex generator is placed on the zone to be detected of sheet metal to be detected; Again four piezoelectric transducer S1, S2, S3 and S4 are placed on this sheet metal to be detected by four vertex positions of rhombus; Each piezoelectric transducer is connected to prime amplifier through signal wire respectively, and this prime amplifier is connected to PC with concentric cable again; When beginning to detect; Let signal generator output control signal in the vortex generator; This control signal is input to the power amplifier that connects the 190V direct supply in the vortex generator, and this power amplifier generation and the same frequency of control signal and period and voltage are the pulse voltage of 190V, and this pulse voltage is loaded on the loop of being made up of resonant capacitance and drive coil in the vortex generator; On sheet metal to be detected, produce thus with the frequency eddy current; If there is crack-type defect in sheet metal to be detected, can be inspired acoustic emission signal, this acoustic emission signal is by four piezoelectric sensor S ₁, S ₂, S ₃And S ₄Detect collection and input to prime amplifier through signal wire; Amplify by this prime amplifier again and input to PC; This PC carries out two dimension time difference location according to the acoustic emission signal that is collected, thereby detection and localization goes out the crack-type defect that this sheet metal to be detected exists.

The electromagnetic sound emission lossless detection method of above-mentioned a kind of sheet metal, said control signal is that 1 week, voltage are the square-wave signal of 8V; Frequency is the resonance frequency f in the loop of resonant capacitance and drive coil composition ^*(100% ± 10%).

The electromagnetic sound emission lossless detection method of above-mentioned a kind of sheet metal; Said PC carries out two dimension time difference location according to the acoustic emission signal that is collected; Its calculation procedure is: PC is according to the velocity of wave V of the acoustic emission sound wave that sends of sheet metal to be detected of input, again according to four piezoelectric transducer S ₁, S ₂, S ₃And S ₄Coordinate, calculate piezoelectric transducer S ₁Probe and piezoelectric transducer S ₂Probe spacing be a, piezoelectric transducer S ₃Probe and piezoelectric transducer S ₄The spacing of probe be b, again according to four piezoelectric sensor S ₁, S ₂, S ₃And S ₄The acoustic emission signal sequencing that collects is confirmed piezoelectric transducer S ₁With piezoelectric transducer S ₃Between collect the time difference Δ t of acoustic emission signal ₁, and piezoelectric transducer S ₂With piezoelectric transducer S ₄Between collect the time difference Δ t of acoustic emission signal ₂, and then obtain acoustic emission source, i.e. the coordinate of crack tip position according to following time difference location Calculation formula (1) and (2):

$\left\{\begin{array}{cc}x=\frac{\mathrm{\Δ}{t}_{1}V}{2a}[\mathrm{\Δ}{t}_{1}V+2\sqrt{{(x-a/2)}^2+y^2}]& \left(1\right)\\ y=\frac{\mathrm{\Δ}{t}_{2}V}{2b}[\mathrm{\Δ}{t}_{2}V+2\sqrt{{(y-b/2)}^2+x^2}]& \left(2\right).\end{array}\right.$

The electromagnetic sound of above-mentioned a kind of sheet metal emission lossless detection method, the flow process that said PC carries out the program of two dimension time difference location according to the acoustic emission signal that is collected is: velocity of wave V and four piezoelectric transducer S of importing the acoustic emission sound wave that sheet metal to be detected sends respectively ₁, S ₂, S ₃And S ₄Coordinate → PC according to four piezoelectric transducer S ₁, S ₂, S ₃And S ₄Coordinate, calculate piezoelectric transducer S ₁Probe and piezoelectric transducer S ₃Probe between apart from a, calculate piezoelectric transducer S ₂Probe and piezoelectric transducer S ₄Probe between distance b → PC arrive the sequencing of piezoelectric sensor according to the acoustic emission signal that collects, confirm piezoelectric transducer S ₁With piezoelectric transducer S ₃Between gather the time difference Δ t of acoustic emission signal ₁, and piezoelectric transducer S ₂With piezoelectric transducer S ₄Between gather the time difference Δ t of acoustic emission signal ₂→ PC calculates the acoustic emission source coordinate according to time difference ranging formula, realizes the location to sheet metal crack-type defect to be detected.

The used device of electromagnetic sound emission lossless detection method of above-mentioned a kind of sheet metal is based on the sheet metal electromagnetic nondestructive device that eddy current encourages acoustic emission, comprises vortex generator, four piezoelectric transducer S ₁, S ₂, S ₃, S ₄, prime amplifier and PC; Said vortex generator is made up of signal generator, power amplifier and drive coil; Its intermediate power amplifier is connected and composed by following circuit by MOSFET Q1, MOSFET Q2, diode D1, diode D2, a transformer and a resonant capacitance: the collector of MOSFET Q1 connects the negative pole of 190V direct current positive pole and D2; Negative pole and the transformer that the emitter of MOSFET Q1 meets diode D1 holds 1 in the same way, the gate pole of MOSFET Q1 connects the signal output part 1 of signal generator through signal wire; The collector of MOSFET Q2 connects positive pole and the transformer backward end 1 of diode D2; The emitter of MOSFET Q2 connects the positive pole of 190V direct current negative pole and D1, and the gate pole of MOSFET Q2 connects the signal output part 2 of signal generator through signal wire, and transformer backward end 2 connects resonant capacitance one end; Transformer holds 2 to connect drive coil one end in the same way, and another termination drive coil other end of resonant capacitance is formed the loop thus; The drive coil of vortex generator lies in the zone to be detected of sheet metal to be detected, again with four piezoelectric transducer S ₁, S ₂, S ₃And S ₄Four vertex positions by rhombus are placed on this sheet metal to be detected four piezoelectric transducer S respectively ₁, S ₂, S ₃And S ₄Be connected to prime amplifier through signal wire respectively, prime amplifier is connected to PC with concentric cable.

The electromagnetic sound of above-mentioned a kind of sheet metal is launched in the used device of lossless detection method, and the drive coil in the said vortex generator is that 170 circles, the external diameter of 0.3mm enameled wire coiling is that 1.5cm, internal diameter are that 0.5cm and height are the air core coil of 1cm.

The electromagnetic sound of above-mentioned a kind of sheet metal is launched in the used device of lossless detection method; The model of the signal generator in the said vortex generator is GWinstek SFG-1003; The model of MOSFET Q1 and MOSFET Q2 is IRF730; The model of diode D1 and diode D2 is MUR1620, and transformer is for the 110 circle coils that use the coiling of 0.3mm enameled wire with the TX36/23/15 of Philips 1: 1 transformer as magnetic core, and the rated voltage of resonant capacitance is that 1200V and capacity are 1.5uF.

The electromagnetic sound of above-mentioned a kind of sheet metal is launched in the used device of lossless detection method, and said signal wire is the 50 Ω copper conductors in 0.2mm line footpath, and other connecting line and lead are the enameled wire of 0.5mm.

The electromagnetic sound of above-mentioned a kind of sheet metal is launched in the used device of lossless detection method, said four piezoelectric transducer S ₁, S ₂, S ₃And S ₄Be purchased, produced by U.S. PAC company, model is all WSA; Said prime amplifier is purchased, and is produced by U.S. PAC company, and model is 2/4/6.

The invention has the beneficial effects as follows:

Compared with prior art; The outstanding substantive distinguishing features of the electromagnetic sound of a kind of sheet metal of the present invention emission lossless detection method and device thereof is, impulse eddy current is loaded on the sheet metal to be detected, receives the influence of the crack-type defect of the existence on the sheet metal to be detected; Impulse eddy current forms tangible concentration effect at the crack tip place; Current density sharply increases near causing crack tip, and under the effect in magnetic field, the crack tip place produces Lorentz force; And the direction of Lorentz force makes the crackle both sides outwards expand respectively; And then inspire and comprise the multitone that enriches defect information and transmit, utilize piezoelectric transducer to detect this acoustic emission signal again and carry out the accurate information that signal Processing can obtain crack-type defect on the sheet metal, thereby realize accurate detection and location the sheet metal crack-type defect with PC.

Compared with prior art; The electromagnetic sound emission lossless detection method of a kind of sheet metal of the present invention and the marked improvement of device thereof are; 1., sheet metal to be detected do not detect under having the effect of the mechanical load of adding; Detection obtains the moving state information of fault in material, and the structure of sheet metal to be detected is not caused secondary damage; 2. impulse eddy current can excite and comprise the multitone that enriches defect information and transmit, and has improved the detectability of acoustic emission testing technology to defective; 3. the present invention uses drive coil to load electric magnetization, has greatly reduced the requirement to power supply, makes load mode need not contact, and has improved detection speed; 4. the electromagnetic sound of a kind of sheet metal of the present invention emission lossless detection method is simple to operate, and the building block of its device is simple in structure and cheap.

Description of drawings

Below in conjunction with accompanying drawing and embodiment the present invention is further specified.

Fig. 1 is the operating process schematic block diagram of the electromagnetic sound emission lossless detection method of a kind of sheet metal of the present invention.

Fig. 2 is the formation schematic block diagram of the used device of the electromagnetic sound emission lossless detection method of a kind of sheet metal of the present invention.

Fig. 3 is the circuit theory diagrams of the vortex generator of the used device of the electromagnetic sound emission lossless detection method of a kind of sheet metal of the present invention.

Fig. 4 is the PC in the used device of the electromagnetic sound emission lossless detection method of a kind of sheet metal of the present invention carries out two dimension time difference plane positioning step according to the acoustic emission signal that collects a synoptic diagram.

Fig. 5 is the process flow diagram that PC carries out the program of two dimension time difference location in the used device of the electromagnetic sound emission lossless detection method of a kind of sheet metal of the present invention according to the acoustic emission signal that collects.

Embodiment

Embodiment illustrated in fig. 1 showing, the operating process of the electromagnetic sound emission lossless detection method of a kind of sheet metal of the present invention is: impulse eddy current is loaded on the sheet metal to be detected, if there is crackle in sheet metal to be detected; Can be inspired acoustic emission signal; Detect and gather this acoustic emission signal, transmit acoustic emission signal, detected acoustic emission signal is amplified; Carry amplifying signal, carry out data acquisition and processing and obtain a result.

Embodiment illustrated in fig. 2 showing, the used device of electromagnetic sound emission lossless detection method of a kind of sheet metal of the present invention is made up of vortex generator, four piezoelectric transducers, prime amplifier and PCs.

Embodiment illustrated in fig. 3 showing; The vortex generator of the device that the electromagnetic sound emission lossless detection method of a kind of sheet metal of the present invention is used is made up of signal generator, power amplifier device and drive coil; Its intermediate power amplifier is connected and composed by following circuit by MOSFETQ1, MOSFET Q2, diode D1, diode D2, a transformer and a resonant capacitance: the collector of MOSFET Q1 connects the negative pole of 190V direct current positive pole and D2; Negative pole and the transformer that the emitter of MOSFET Q1 meets diode D1 holds 1 in the same way, the gate pole of MOSFET Q1 connects the signal output part 1 of signal generator through signal wire; The collector of MOSFET Q2 connects positive pole and the transformer backward end 1 of diode D2; The emitter of MOSFET Q2 connects the positive pole of 190V direct current negative pole and D1; The gate pole of MOSFET Q2 connects the signal output part 2 of signal generator through signal wire; Transformer backward end 2 connects resonant capacitance one end, and transformer holds 2 to connect drive coil one end in the same way, and another termination drive coil other end of resonant capacitance is formed the loop thus.

PC carries out two dimension time difference location according to the acoustic emission signal that is collected, promptly two-dimentional time difference plane positioning, and its step is as shown in Figure 4: PC is according to four piezoelectric transducer S ₁, S ₂, S ₃And S ₄Coordinate, calculate piezoelectric transducer S ₁Probe and piezoelectric transducer S ₂Probe spacing be a, piezoelectric transducer S ₃Probe and piezoelectric transducer S ₄The spacing of probe be b, again according to four piezoelectric sensor S ₁, S ₂, S ₃And S ₄The acoustic emission signal sequencing that collects is confirmed piezoelectric transducer S ₁With piezoelectric transducer S ₃Between collect the time difference Δ t of acoustic emission signal ₁, and piezoelectric transducer S ₂With piezoelectric transducer S ₄Between collect the time difference Δ t of acoustic emission signal ₂, by piezoelectric transducer S ₁With piezoelectric transducer S ₃Gather the time difference Δ t of acoustic emission signal ₁Obtain hyperbolic curve 1, by piezoelectric transducer S ₂With piezoelectric transducer S ₄Gather the time difference Δ t of acoustic emission signal ₂Obtain hyperbolic curve 2, add the velocity of wave V of PC, draw Coordinate Calculation formula (1) and (2) according to the acoustic emission sound wave that sends of sheet metal to be detected of input, definite thus acoustic emission source be the crack tip position be located in two hyp intersection point Q (x, y) on.

Embodiment illustrated in fig. 5 showing, the flow process that PC carries out the program of two dimension time difference location according to the acoustic emission signal that collects in the used device of the electromagnetic sound of a kind of sheet metal of the present invention emission lossless detection method is: velocity of wave V and four piezoelectric transducer S of importing the acoustic emission sound wave that sheet metal to be detected sends respectively ₁, S ₂, S ₃And S ₄Coordinate.→ PC is according to four piezoelectric transducer S ₁, S ₂, S ₃And S ₄Coordinate, calculate piezoelectric transducer S ₁Probe and piezoelectric transducer S ₃Probe between apart from a, calculate piezoelectric transducer S ₂Probe and piezoelectric transducer S ₄Probe between distance b.→ PC is confirmed piezoelectric transducer S according to the sequencing of the acoustic emission signal arrival piezoelectric sensor that collects ₁With piezoelectric transducer S ₃Between gather the time difference Δ t of acoustic emission signal ₁, and piezoelectric transducer S ₂With piezoelectric transducer S ₄Between gather the time difference Δ t of acoustic emission signal ₂→ PC calculates the acoustic emission source coordinate according to time difference ranging formula, realizes the location to sheet metal crack-type defect to be detected.

The used device of the electromagnetic sound of a kind of sheet metal among following all embodiment emission lossless detection method be with such as above-mentioned Fig. 2 and described parts of Fig. 3 and components and parts formation; The model of the signal generator in the said vortex generator is GWinstek SFG-1003; The model of MOSFET Q1 and MOSFET Q2 is IRF730; The model of diode D1 and diode D2 is MUR1620; Transformer is for the 110 circle coils that use the coiling of 0.3mm enameled wire with the TX36/23/15 of Philips 1: 1 transformer as magnetic core, and the rated voltage of resonant capacitance is that 1200V and capacity are 1.5uF.Drive coil in the said vortex generator is that 170 circles, the external diameter of 0.3mm enameled wire coiling is that 1.5cm, internal diameter are that 0.5cm and height are the air core coil of 1cm.Said signal wire is the 50 Ω copper conductors in 0.2mm line footpath, and other connecting line and lead are the enameled wire of 0.5mm.Said four piezoelectric transducer S ₁, S ₂, S ₃And S ₄Be purchased, produced by U.S. PAC company, model is all WSA.The electromagnetic sound of above-mentioned a kind of sheet metal is launched in the used device of lossless detection method, and said prime amplifier is purchased, and is produced by U.S. PAC company, and model is 2/4/6.Drive coil in the vortex generator is lain on the sheet metal, again with four piezoelectric transducer S ₁, S ₂, S ₃And S ₄Four vertex positions by rhombus are placed on this sheet metal to be detected four piezoelectric transducer S respectively ₁, S ₂, S ₃And S ₄Be connected to prime amplifier through signal wire respectively, this prime amplifier is wired to PC.

Embodiment 1

When beginning to detect; Signal generator output control signal in the vortex generator is that 1 week, frequency are that 5.5kHz and voltage are the square-wave voltage of 8V; This signal is input to the power amplifier that connects the 190V direct supply in the vortex generator; This power amplifier generation and the same frequency of control signal and period and voltage are the pulse voltage of 190V; This pulse square wave voltage is loaded on the loop of being made up of resonant capacitance and drive coil, and to generate for 2 weeks on the aluminum metal thin plate to be detected of 500mm * 115mm * 15mm be the quasi sine eddy current of 5kHz with frequency being of a size of, and has crackle as if this aluminum metal thin plate to be detected; Can be inspired acoustic emission signal, this acoustic emission signal is by four piezoelectric sensor S ₁, S ₂, S ₃And S ₄Detect and input to prime amplifier through signal wire; Amplify acoustic emission signal and input to PC by this prime amplifier; This PC carries out two dimension time difference location according to the acoustic emission signal that is collected; Its calculation procedure is: PC is according to the velocity of wave V of the acoustic emission sound wave that sends of aluminum metal thin plate to be detected of input, again according to four piezoelectric transducer S ₁, S ₂, S ₃And S ₄Coordinate, calculate piezoelectric transducer S ₁Probe and piezoelectric transducer S ₂Probe spacing be a, piezoelectric transducer S ₃Probe and piezoelectric transducer S ₄The spacing of probe be b,, again according to four piezoelectric sensor S ₁, S ₂, S ₃And S ₄The acoustic emission signal sequencing that collects is confirmed piezoelectric transducer S ₁With piezoelectric transducer S ₃Between collect the time difference Δ t of acoustic emission signal ₁, and piezoelectric transducer S ₂With piezoelectric transducer S ₄Between collect the time difference Δ t of acoustic emission signal ₂, and then obtain acoustic emission source, i.e. the coordinate of crack tip position according to following time difference location Calculation formula (1) and (2):

$\left\{\begin{array}{cc}x=\frac{\mathrm{\Δ}{t}_{1}V}{2a}[\mathrm{\Δ}{t}_{1}V+2\sqrt{{(x-a/2)}^2+y^2}]& \left(1\right)\\ y=\frac{\mathrm{\Δ}{t}_{2}V}{2b}[\mathrm{\Δ}{t}_{2}V+2\sqrt{{(y-b/2)}^2+x^2}]& \left(2\right).\end{array}\right.$

Above-mentioned two dimension time difference finder flow process is: velocity of wave V and four piezoelectric transducer S of importing the acoustic emission sound wave that aluminum metal thin plate to be detected sends respectively ₁, S ₂, S ₃And S ₄Coordinate.→ PC is according to four piezoelectric transducer S ₁, S ₂, S ₃And S ₄Coordinate, calculate piezoelectric transducer S ₁Probe and piezoelectric transducer S ₃Probe between apart from a, calculate piezoelectric transducer S ₂Probe and piezoelectric transducer S ₄Probe between distance b.→ PC is confirmed piezoelectric transducer S according to the acoustic emission signal sequencing that collects ₁With piezoelectric transducer S ₃Between gather time difference of acoustic emission signal and piezoelectric transducer S ₂With piezoelectric transducer S ₄Between gather the time difference Δ t of acoustic emission signal ₂→ PC calculates the acoustic emission source coordinate according to time difference ranging formula, realizes the location to this aluminum metal thin plate crack-type defect to be detected.

Final detection and localization goes out the crack defect position that this aluminum metal thin plate to be detected exists, and positioning error is 1mm.

Embodiment 2

The signal generator output control signal of removing in the vortex generator is that 1 week, frequency are that 4.5kHz and voltage are the pulse square wave voltage of 8V; Sheet metal to be detected is for to be of a size of outside the copper sheet metal to be detected of 500mm * 115mm * 15mm, and other are all with embodiment 1.

Final detection and localization goes out the crack defect position that this copper sheet metal to be detected exists, and positioning error is 1mm.

Embodiment 3

The signal generator output control signal of removing in the vortex generator is that 1 week, frequency are that 11.0kHz and Voltage Peak peak value are the pulse square wave voltage of 380V; Sheet metal to be detected is for to be of a size of outside the copper sheet metal to be detected of 500mm * 115mm * 15mm, and other are all with embodiment 1.

Final detection and localization goes out the crack defect position that this copper sheet metal to be detected exists, and positioning error is 1mm.

Claims (6)

1. the electromagnetic sound of a sheet metal is launched lossless detection method; It is characterized in that: be a kind of electromagnetic nondestructive method of the sheet metal based on impulse eddy current excitation acoustic emission, the steps include: impulse eddy current is loaded on the sheet metal to be detected, if there is crackle in sheet metal to be detected; Can be inspired acoustic emission signal; Detect and gather this acoustic emission signal, transmit acoustic emission signal, detected acoustic emission signal is amplified; Carry amplifying signal, carry out data acquisition and processing and obtain a result; Concrete operations are; Drive coil in the vortex generator is placed on the zone to be detected of sheet metal to be detected; Again four piezoelectric transducer S1, S2, S3 and S4 are placed on this sheet metal to be detected by four vertex positions of rhombus; Each piezoelectric transducer is connected to prime amplifier through signal wire respectively, and this prime amplifier is connected to PC with concentric cable again; When beginning to detect; Let signal generator output control signal in the vortex generator; This control signal is input to the power amplifier that connects the 190V direct supply in the vortex generator, and this power amplifier generation and the same frequency of control signal and period and voltage are the pulse voltage of 190V, and this pulse voltage is loaded on the loop of being made up of resonant capacitance and drive coil in the vortex generator; On sheet metal to be detected, produce thus with the frequency eddy current; If there is crack-type defect in sheet metal to be detected, can be inspired acoustic emission signal, this acoustic emission signal is by four piezoelectric sensor S ₁, S ₂, S ₃And S ₄Detect collection and input to prime amplifier through signal wire; Amplify by this prime amplifier again and input to PC; This PC carries out two dimension time difference location according to the acoustic emission signal that is collected, thereby detection and localization goes out the crack-type defect that this sheet metal to be detected exists.

2. according to the electromagnetic sound emission lossless detection method of the said a kind of sheet metal of claim 1, it is characterized in that: said control signal is that 1 week, voltage are the square-wave signal of 8V; Frequency is the resonance frequency f in the loop of resonant capacitance and drive coil composition ^*(100% ± 10%)

3. launch lossless detection method according to the electromagnetic sound of the said a kind of sheet metal of claim 1; It is characterized in that: said PC carries out two dimension time difference location according to the acoustic emission signal that is collected; Its calculation procedure is: PC is according to the velocity of wave V of the acoustic emission sound wave that sends of sheet metal to be detected of input, again according to four piezoelectric transducer S ₁, S ₂, S ₃And S ₄Coordinate, calculate piezoelectric transducer S ₁Probe and piezoelectric transducer S ₂Probe spacing be a, piezoelectric transducer S ₃Probe and piezoelectric transducer S ₄The spacing of probe be b,, again according to four piezoelectric sensor S ₁, S ₂, S ₃And S ₄The acoustic emission signal sequencing that collects is confirmed piezoelectric transducer S ₁With piezoelectric transducer S ₃Between collect the time difference Δ t of acoustic emission signal ₁, and piezoelectric transducer S ₂With piezoelectric transducer S ₄Between collect the time difference Δ t of acoustic emission signal ₂, and then obtain acoustic emission source, i.e. the coordinate of crack tip position according to following time difference location Calculation formula (1) and (2):

$\left\{\begin{array}{cc}x=\frac{\mathrm{\Δ}{t}_{1}V}{2a}[\mathrm{\Δ}{t}_{1}V+2\sqrt{{(x-a/2)}^2+y^2}]& \left(1\right)\\ y=\frac{\mathrm{\Δ}{t}_{2}V}{2b}[\mathrm{\Δ}{t}_{2}V+2\sqrt{{(y-b/2)}^2+x^2}]& \left(2\right).\end{array}\right.$

4. according to the electromagnetic sound of the said a kind of sheet metal of claim 1 emission lossless detection method, it is characterized in that: the flow process that said PC carries out the program of two dimension time difference location according to the acoustic emission signal that is collected is: velocity of wave V and four piezoelectric transducer S of importing the acoustic emission sound wave that sheet metal to be detected sends respectively ₁, S ₂, S ₃And S ₄Coordinate → PC according to four piezoelectric transducer S ₁, S ₂, S ₃And S ₄Coordinate, calculate piezoelectric transducer S ₁Probe and piezoelectric transducer S ₃Probe between apart from a, calculate piezoelectric transducer S ₂Probe and piezoelectric transducer S ₄Probe between distance b → PC arrive the sequencing of piezoelectric sensor according to the acoustic emission signal that collects, confirm piezoelectric transducer S ₁With piezoelectric transducer S ₃Between gather the time difference Δ t of acoustic emission signal ₁, and piezoelectric transducer S ₂With piezoelectric transducer S ₄Between gather the time difference Δ t of acoustic emission signal ₂→ PC calculates the acoustic emission source coordinate according to time difference ranging formula, realizes the location to sheet metal crack-type defect to be detected.

5. the used device of the electromagnetic sound of the said a kind of sheet metal of claim 1 emission lossless detection method is characterized in that: be based on the sheet metal electromagnetic nondestructive device of impulse eddy current excitation acoustic emission, comprise vortex generator, four piezoelectric transducer S ₁, S ₂, S ₃, S ₄, prime amplifier and PC.Said vortex generator is made up of signal generator, power amplifier and drive coil; Its intermediate power amplifier is connected and composed by following circuit by MOSFET Q1, MOSFET Q2, diode D1, diode D2, a transformer and a resonant capacitance: the collector of MOSFET Q1 connects the negative pole of 190V direct current positive pole and D2; Negative pole and the transformer that the emitter of MOSFET Q1 meets diode D1 holds 1 in the same way, the gate pole of MOSFET Q1 connects the signal output part 1 of signal generator through signal wire; The collector of MOSFET Q2 connects positive pole and the transformer backward end 1 of diode D2; The emitter of MOSFET Q2 connects the positive pole of 190V direct current negative pole and D1; The gate pole of MOSFET Q2 connects the signal output part 2 of signal generator through signal wire; Transformer backward end 2 connects resonant capacitance one end, and transformer holds 2 to connect drive coil one end in the same way, and another termination drive coil other end of resonant capacitance is formed the loop thus; The drive coil of vortex generator lies in the zone to be detected of sheet metal to be detected, again with four piezoelectric transducer S ₁, S ₂, S ₃And S ₄Four vertex positions by rhombus are placed on this sheet metal to be detected four piezoelectric transducer S respectively ₁, S ₂, S ₃And S ₄Be connected to prime amplifier through signal wire respectively, prime amplifier is connected to PC with concentric cable.

6. according to the used device of electromagnetic sound emission lossless detection method of the said a kind of sheet metal of claim 5, it is characterized in that: the drive coil in the said vortex generator is that 170 circles, the external diameter of 0.3mm enameled wire coiling is that 1.5cm, internal diameter are that 0.5cm and height are the air core coil of 1cm.

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