CN108956782B - Laser shock online detection method and device based on sound wave frequency characteristics - Google Patents
Laser shock online detection method and device based on sound wave frequency characteristics Download PDFInfo
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- C21D10/005—Modifying the physical properties by methods other than heat treatment or deformation by laser shock processing
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Abstract
The invention relates to the field of laser processing technology and nondestructive testing, in particular to a laser shock online testing method and device based on sound wave frequency characteristics. The device comprises sampling circuit, laser shock sound wave frequency signal storehouse, system program, and wherein the sampling circuit includes: the device comprises a sound wave collector, a low-pass filter, a common collector amplifying circuit and an A/D converter. The system program consists of three subroutines: a time-frequency conversion subprogram, a signal processing subprogram and a control subprogram. The online detection of the laser impact effect is realized by detecting the actually measured sound wave frequency signal in the laser impact process and comparing the actually measured sound wave frequency signal with the sound wave frequency signal in the signal library.
Description
Technical Field
The invention relates to the field of laser processing technology and nondestructive testing, in particular to a laser shock online testing method and device based on sound wave frequency characteristics, which are suitable for a laser shock process for improving the mechanical properties of key parts.
Background
The principle of the laser shock technique is that when a short pulse of high power density is applied to the absorbing layer on the metal surface through flowing water (confinement layer), the absorbing layer rapidly vaporizes, while plasma gas is formed. The plasma gas expands sharply, introducing residual compressive stress on the metal surface. Laser shock is a high and new technology that can improve the fatigue, wear and corrosion resistance of metal materials. In addition, the laser impact can also utilize the force effect of high-amplitude shock waves induced by the interaction of high-energy pulse laser and materials to enable the sheet material to generate plastic deformation.
In the early laboratory stage, the workpiece which has just passed the impact can be removed to check the impact effect. However, in the industrial stage, since laser impact is completed in a closed workshop, field detection after each impact is impossible, and in addition, the detection mode is not applicable in consideration of improvement of production efficiency. To popularize the laser impact technique in industrial applications, the on-line detection of the machining process and the real-time detection of the impact effect must be realized and used as the basis for controlling the machining quality.
The existing laser impact on-line detection method mainly comprises the following steps: (1) laser Shock Peening System With Time-of-flight Monitoring (Patent Number: US20070119824A 1). The detection method utilizes the flight time characteristic of shock waves (namely the propagation speed of the shock waves) in the laser shock process to predict shock results, and realizes real-time online detection of laser shock. (2) The invention discloses a laser shock peening online detection method and device based on shock wave waveform characteristics (an authorization notice number CN 101482542B), and the online detection of a laser shock effect is realized by detecting the amplitude and the pulse width of shock waves transmitted in air.
The failure types in the laser shock processing process cannot be accurately judged by the methods, including the following steps: (1) failure caused by unstable light emission of the laser; (2) failure of the absorber layer due to plasma breakthrough; (3) failure due to workpiece ablation; (4) the running water (the constraining layer) does not cover the workpiece resulting in failure. And the methods can not automatically control the laser impact equipment to stop when failure occurs, thereby realizing automatic operation.
The optimization of laser shock process parameters at the present stage has reached a bottleneck period due to the inability to accurately detect the specific failure reasons in the laser shock process. There is a need for a new on-line detection method to detect the quality of the machining process in real time and to pinpoint the type of failure when it occurs, providing a constructive basis for the improvement of laser shock process parameters.
Disclosure of Invention
In view of the above problems, an object of the present invention is to provide an on-line laser shock detection method based on acoustic frequency characteristics, which has high detection accuracy and improved detection efficiency. The on-line detection of the laser impact effect is realized by detecting the actually measured sound wave frequency signal in the laser impact process and comparing the actually measured sound wave frequency signal with the sound wave frequency signal in the signal library. The invention also provides a device for laser shock online detection based on the sound wave frequency characteristics, which comprises a sound wave collector, a low-pass filter, a common collector amplifying circuit, an A/D converter, a laser shock sound wave frequency signal library and a system program. The method and the device can accurately detect the failure reason in the laser impact process, and provide a constructive basis for the improvement of laser impact process parameters.
The purpose of the invention is realized by the following technical means:
the principle of the invention is as follows: when laser impacts a certain workpiece, the frequency of the sound wave caused by the shock wave is determined, when failure occurs, the frequency of the sound wave caused by the corresponding shock wave can be changed, the failure reason of the laser impact can be judged by detecting the change of the frequency of the sound wave, and therefore the processing quality of the laser impact is detected on line at high precision.
A laser shock on-line detection device based on sound wave frequency characteristics comprises: laser shock sound wave frequency signal library, system program and sampling circuit. The sampling circuit of the device comprises: the device comprises a sound wave collector, a low-pass filter, a common collector amplifying circuit and an A/D converter. The sound wave collector, the low-pass filter, the common collector amplifying circuit and the A/D converter are sequentially connected through a signal line, and finally the A/D converter is connected to a computer. The computer is connected with the control cabinet through a signal wire, and the control cabinet is respectively connected with the manipulator and the laser through the signal wire. The sound wave collector is positioned above a workpiece on the clamping manipulator, and the distance is such that the flowing water restriction layer can obtain the optimal sound wave information on the premise of not sputtering on the bionic ear sound wave collector; the laser shock sound wave frequency signal library and the system program are installed on a computer. The online detection of the laser impact effect is realized by detecting the actually measured sound wave frequency signal in the laser impact process and comparing the actually measured sound wave frequency signal with the sound wave frequency signal in the signal library.
The sound wave collector adopts a bionic ear sound wave collector to collect time domain signals of sound waves.
The low-pass filter adopts a Butterworth filter for filtering white noise, when the cut-off frequency is set to be 1000Hz, the noise can be reduced to one thousandth, if the noise density is the same, the influence on the total noise voltage is larger when the frequency is higher, and therefore the total noise voltage can be obviously reduced by removing high-frequency noise.
The common collector amplifying circuit plays a role in amplifying current and power, and the A/D converter can convert an analog sound wave signal into a digital sound wave signal.
The system program has three subprograms, and each function is as follows: a time-frequency conversion subroutine: the time-frequency conversion function is realized by utilizing a fast algorithm of discrete Fourier transform; b signal processing subroutine: judging the effect of laser shock by analyzing the frequency domain signal, and outputting a judgment result; c control subroutine: because the control cabinet is connected with the laser and the manipulator, the system program can automatically control the manipulator and the laser to stop according to the judgment result by controlling the control cabinet.
The system program compares the amplitude value of each frequency of the actually measured sound wave frequency signal with the amplitude value of each frequency of the standard sound wave frequency signal in the signal library through the signal processing subprogram, if the amplitude value of a certain section of frequency exceeds the threshold K% of the frequency range of the standard sound wave frequency signal, the actually measured sound wave frequency signal is judged to be a failure signal by the signal processing subprogram in the system program, otherwise, the actually measured sound wave frequency signal is a normal signal, and the processing is normally carried out. The system program compares the actual measurement sound wave frequency signals judged to be invalid with the invalid sound wave frequency signals in the signal library, if all frequency bands do not exceed the threshold K% of the amplitude value of the corresponding frequency band in a certain invalid sound wave frequency signal, the program judges the invalid form and outputs the invalid reason, and the system program sends out an instruction to stop the laser and the manipulator. Otherwise, the program output fails for unknown reasons, and the system program issues instructions to shut down the laser and the robot.
The calculation formula of the threshold value K is as follows: k ═ B × S. Where B represents the amplitude of the envelope of the corresponding acoustic frequency signal in the signal library. Since the corresponding sound wave frequency signals in the signal library are different, the amplitudes of the envelope lines are also different, and therefore, each threshold value K% has no correlation. And S represents a safety factor, and the value of S is an empirical value and can be adjusted according to the actual processing environment.
The laser shock acoustic wave frequency signal library comprises: a, a failure acoustic wave frequency signal caused by unstable light emission of a laser; b, a failure acoustic frequency signal caused by the fact that the absorption layer is broken by plasma; c, failure acoustic frequency signals caused by workpiece ablation; d, the flowing water restraint layer does not cover the failure sound wave frequency signal caused by the workpiece; e the laser without failure impacts the standard acoustic frequency signal.
The gain effect of the invention is as follows:
1. the invention has simple detection principle, simple used detection device, stable detection process, high repeatability and easy realization. 2. The frequency domain analysis method is applied to the field of laser shock detection for the first time, and compared with the traditional laser shock online detection method and device, the method can accurately detect the failure reason in the laser shock process, and provides a constructive basis for the improvement of laser shock process parameters. 3. The set safety factor S can be adjusted according to the actual processing environment. Therefore, the invention has wide adaptability.
Drawings
Fig. 1 is a flowchart of an online detection method of laser shock based on acoustic frequency characteristics.
Fig. 2 is a schematic diagram of an online laser shock detection device based on acoustic frequency characteristics.
Wherein, 1 is a bionic ear sound wave collector, 2 is a Butterworth filter, 3 is a common collector amplifying circuit, 4 is an A/D converter, 5 is a sampling circuit, 6 is a computer, 7 is a control cabinet, 8 is a laser, 9 is a mechanical arm, 10 is a workpiece, 11 is an absorption layer, and 12 is flowing water (a constraint layer).
Detailed Description
The invention will be further described with reference to the accompanying drawings, but the scope of the invention is not limited thereto.
As shown in the figure, the invention comprises a laser shock sound wave frequency signal library, a system program, a sampling circuit 5 and the like. The on-line detection of the laser impact effect is realized by detecting the actually measured sound wave frequency signal of the sound wave in the laser impact process and comparing the actually measured sound wave frequency signal with the sound wave frequency signal in the signal library. The sampling circuit 5 of the device comprises: the bionic ear acoustic wave collector comprises a bionic ear acoustic wave collector 1, a Butterworth filter 2, a common collector amplifying circuit 3 and an A/D converter 4. The laser shock acoustic wave frequency signal library and the system program are installed on the computer 6. The system program has three subprograms, and each function is as follows: a time-frequency conversion subroutine: the time-frequency conversion function is realized by utilizing a fast algorithm of discrete Fourier transform; b signal processing subroutine: judging the effect of laser shock by analyzing the frequency domain signal, and outputting a judgment result; c control subroutine: because the control cabinet 7 is connected with the laser 8 and the manipulator 9, the system program can automatically control the laser 8 and the manipulator 9 to stop according to the judgment result by controlling the control cabinet 7.
The laser impact on-line detection device based on the sound wave frequency characteristic comprises the following use steps:
1. preparation work before laser shock is carried out: a workpiece 10 is clamped on a manipulator 9, the workpiece 10 is positioned on a focusing focus of a laser beam through the movement of the manipulator 9, an absorption layer 11 is pasted on the surface of a region to be processed of the workpiece, and flowing water (a restraint layer) 12 is adjusted to cover the surface of the workpiece 10.
2. The bionic ear sound wave collector 1, the Butterworth filter 2, the common collector amplifying circuit 3 and the A/D converter 4 are sequentially connected through signal lines, and finally the A/D converter 4 is connected to the computer 6. The bionic ear sound wave collector 1 is placed 50cm above a workpiece 10, and the purpose is to obtain the best sound wave information on the premise that flowing water (a constraint layer) 12 is not sputtered on the bionic ear sound wave collector 1.
3. The 4 kinds of failure acoustic frequency signals and the standard acoustic frequency signals are input into a signal library.
4. After the system program is started, the laser 8 and the manipulator 9 are started to start laser shock.
5. And the signal processing subprogram in the system program compares the amplitude value of each frequency of the actually measured sound wave frequency signal with the amplitude value of each frequency of the standard sound wave frequency signal, if the amplitude value of a certain section of frequency exceeds the threshold K% of the frequency range of the standard sound wave frequency signal, the actually measured sound wave frequency signal is judged as a failure signal by the signal processing subprogram in the system program, otherwise, the actually measured sound wave frequency signal is a normal signal, and the processing is normal.
6. And a signal processing subprogram in the system program compares the actually measured sound wave frequency signal which is judged to be invalid with the invalid sound wave frequency signal in the signal library, if all frequency bands do not exceed the threshold K% of the amplitude value of the corresponding frequency band in a certain invalid sound wave frequency signal, the program judges the invalid form and outputs the reason of the invalid, and the system program sends an instruction to stop the laser 8 and the manipulator 9. Otherwise, the program output fails for an unknown reason and the system program instructs the laser 8 and the robot 9 to stop.
Claims (5)
1. An on-line laser shock detection device based on acoustic frequency characteristics, the device comprising: a laser shock sound wave frequency signal library, a system program and a sampling circuit; the sampling circuit includes: the device comprises a sound wave collector, a low-pass filter, a common collector amplifying circuit and an A/D converter; the sound wave collector, the low-pass filter, the common collector amplifying circuit and the A/D converter are sequentially connected through a signal line, and finally the A/D converter is connected to a computer; the computer is connected with the control cabinet through a signal wire, and the control cabinet is respectively connected with the manipulator and the laser through the signal wire; the sound wave collector is positioned above a workpiece on the clamping manipulator, and the distance is such that the flowing water restriction layer can obtain the optimal sound wave information on the premise of not sputtering on the bionic ear sound wave collector; the laser shock sound wave frequency signal library and the system program are installed on the computer; the online detection of the laser impact effect is realized by detecting the actually measured sound wave frequency signal in the laser impact process and comparing the actually measured sound wave frequency signal with the sound wave frequency signal in the signal library; the system program has three subprograms, and each function is as follows: a time-frequency conversion subroutine: the time-frequency conversion function is realized by utilizing a fast algorithm of discrete Fourier transform; b signal processing subroutine: judging the effect of laser shock by analyzing the frequency domain signal, and outputting a judgment result; c control subroutine: because the control cabinet is connected with the laser and the manipulator, the system program can automatically control the manipulator and the laser to stop according to the judgment result by controlling the control cabinet; the system program compares the amplitude value of each frequency of the actually measured sound wave frequency signal with the amplitude value of each frequency of the standard sound wave frequency signal in the signal library through the signal processing subprogram, if the amplitude value of a certain section of frequency exceeds the threshold value K% of the section of frequency of the standard sound wave frequency signal, the actually measured sound wave frequency signal is judged as a failure signal by the signal processing subprogram in the system program, otherwise, the actually measured sound wave frequency signal is a normal signal, and the processing is normally carried out; the system program compares the actual measurement sound wave frequency signals judged to be invalid with the invalid sound wave frequency signals in the signal library, if all frequency bands do not exceed a threshold K% of amplitude values of corresponding frequency bands in certain invalid sound wave frequency signals, the program judges the invalid form and outputs the invalid reason, and the system program sends out an instruction to stop the laser and the manipulator; otherwise, the program output is invalid due to unknown reasons, and the system program sends out instructions to stop the laser and the manipulator; the calculation formula of the threshold value K is as follows: k ═ B × S; wherein, B represents the amplitude of the envelope curve of the corresponding sound wave frequency signal in the signal library; because corresponding sound wave frequency signals in the signal library are different, the amplitudes of envelope lines of the sound wave frequency signals are also different, and therefore all the threshold values K% have no correlation; s represents a safety factor.
2. The laser shock online detection device based on the sound wave frequency characteristic of claim 1, wherein the sound wave collector adopts a bionic ear sound wave collector to collect a time domain signal of the sound wave.
3. The apparatus according to claim 1, wherein the low pass filter is a butterworth filter for filtering white noise, and when the cut-off frequency is set to 1000Hz, the noise can be reduced to one thousandth, and if the noise density is the same, the higher the frequency, the larger the influence on the total noise voltage, so that the removal of high frequency noise can significantly reduce the total noise voltage.
4. The device for detecting laser shock on line based on frequency characteristics of acoustic wave according to claim 1, wherein the common collector amplifying circuit is used for amplifying current and power, and the a/D converter is used for converting analog acoustic wave signals into digital acoustic wave signals.
5. The on-line laser shock detection device based on the acoustic frequency characteristic as claimed in claim 1, wherein the laser shock acoustic frequency signal library comprises: a, a failure acoustic wave frequency signal caused by unstable light emission of a laser; b, a failure acoustic frequency signal caused by the fact that the absorption layer is broken by plasma; c, failure acoustic frequency signals caused by workpiece ablation; d, the flowing water restraint layer does not cover the failure sound wave frequency signal caused by the workpiece; e the laser without failure impacts the standard acoustic frequency signal.
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| CN110438333A (en) * | 2019-09-19 | 2019-11-12 | 中国人民解放军空军工程大学 | A kind of kHz low-energy laser scanning impact reinforcing method and its device |
| CN110653223B (en) * | 2019-09-26 | 2021-10-29 | 厦门理工学院 | Laser cleaning monitoring device and monitoring method thereof and laser cleaning machine |
| CN114778695B (en) * | 2022-05-17 | 2024-05-03 | 国家能源集团新疆能源有限责任公司 | Nondestructive monitoring analysis method for rock burst mine anchor rod anchoring quality |
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| CN101482542B (en) * | 2009-02-11 | 2012-05-23 | 江苏大学 | Laser impact intensified on-line detection method and apparatus based on waveform characteristics of shock wave |
| CN103712677A (en) * | 2012-10-09 | 2014-04-09 | 天津中杰科技发展有限公司 | Inherent frequency detection method of laser shock peening treatment quality |
| CN103207178A (en) * | 2013-02-04 | 2013-07-17 | 中国航空工业集团公司北京航空制造工程研究所 | Online testing method and apparatus for laser shock peening effect |
| CN105316473B (en) * | 2015-12-04 | 2018-08-28 | 杨昭 | A kind of laser-impact processing on-line checking correcting system based on Workpiece vibration frequency |
| CN106324101A (en) * | 2016-10-20 | 2017-01-11 | 沈阳慧远自动化设备有限公司 | Laser shock strengthening on-line quality monitoring system and method based on sound pressure characteristic |
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