CN113358577A - Electromagnetic wave method for determining starting point of laser ultrasonic signal - Google Patents
Electromagnetic wave method for determining starting point of laser ultrasonic signal Download PDFInfo
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- CN113358577A CN113358577A CN202110646212.7A CN202110646212A CN113358577A CN 113358577 A CN113358577 A CN 113358577A CN 202110646212 A CN202110646212 A CN 202110646212A CN 113358577 A CN113358577 A CN 113358577A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/1702—Systems in which incident light is modified in accordance with the properties of the material investigated with opto-acoustic detection, e.g. for gases or analysing solids
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/01—Arrangements or apparatus for facilitating the optical investigation
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/1702—Systems in which incident light is modified in accordance with the properties of the material investigated with opto-acoustic detection, e.g. for gases or analysing solids
- G01N2021/1706—Systems in which incident light is modified in accordance with the properties of the material investigated with opto-acoustic detection, e.g. for gases or analysing solids in solids
Abstract
The invention discloses an electromagnetic wave method for determining a starting point of a laser ultrasonic signal. When the pulse laser irradiates the surface of the object to be measured, the local high temperature of the pulse laser ablates the surface of the object to form plasma and radiates electromagnetic waves, and the pulse laser is excited inside the object to be measured to generate ultrasonic waves. And receiving the electromagnetic wave by adopting an antenna, and taking the electromagnetic wave as a reference signal or a zero point of the laser ultrasonic signal. The method has strong operability, overcomes the signal zero drift caused by the problems of laser temperature rise and the like when the conventional laser ultrasonic equipment collects ultrasonic signals, eliminates the system error of a detection system, and realizes stable and reliable collection of the laser ultrasonic signals.
Description
Technical Field
The invention belongs to the field of laser ultrasonic nondestructive testing, and particularly relates to a method for generating electromagnetic waves and ultrasonic waves by utilizing pulse laser excitation and taking the electromagnetic waves as a starting point of a pulse laser excitation ultrasonic signal.
Background
With the production and application of various heavy mechanical equipment and precision high-cost parts, the need for nondestructive testing of the equipment or parts becomes urgent. The traditional ultrasonic detection technology is limited by various factors, such as piezoelectric probe type ultrasonic detection and water immersion ultrasonic detection, which must use a coupling agent, and can not achieve non-contact, although electromagnetic ultrasonic detection and air coupling ultrasonic detection are non-contact, a detector still needs to be close to a detected object, and the signal quality needs to be improved. Compared with the traditional ultrasonic detection, the laser ultrasonic detection technology realizes the complete non-contact, nondestructive or micro-damage detection, and realizes the rapid scanning by controlling the movement of the light path, thereby greatly improving the detection efficiency.
For a laser ultrasonic nondestructive testing system, the detection of an ultrasonic signal is an important part, and at present, there are various ways to detect an ultrasonic signal, including a piezoelectric sensor, an air-coupled ultrasonic probe, an optical method, and the like, and after a single ultrasonic signal is received, the start time of the ultrasonic wave cannot be determined, and a reference signal is necessary to determine an accurate time start point.
When a pulse laser acts on the surface of a sample to be measured, the material to be measured is irradiated by the laser to generate plasma and radiate electromagnetic waves to the outside, and the electromagnetic waves and the ultrasonic waves are generated simultaneously. Since the electromagnetic wave velocity is equal to the speed of light, its propagation time is ignored, and therefore the electromagnetic wave can be used as the starting point of the ultrasonic signal.
Disclosure of Invention
The invention aims to provide a laser ultrasonic signal acquisition device which utilizes pulse laser to excite plasma and generate electromagnetic waves, receives the electromagnetic waves through an antenna and is used as a starting point for laser ultrasonic signal acquisition. The method has high detection sensitivity and strong operability, overcomes zero drift caused by the problems of laser temperature rise and the like when the laser ultrasonic signal is acquired at present, and realizes high-precision acquisition of the laser ultrasonic signal.
In order to achieve the above object, the present invention discloses an electromagnetic wave method for determining the starting point of a laser ultrasonic signal, which is characterized in that the method comprises the following steps:
(1) when the pulse laser irradiates the surface of the material to be detected, plasma is formed on the surface of the material to be ablated due to the local high temperature of the pulse laser so as to radiate electromagnetic waves, and the pulse laser is excited in the object to be detected to generate ultrasonic waves;
(2) receiving electromagnetic waves by using an antenna, and taking the electromagnetic waves as a starting point for collecting laser ultrasonic signals;
(3) receiving electromagnetic wave and ultrasonic wave signals through a data acquisition card, and inputting two channel signals into a computer;
(4) the received electromagnetic wave is used as the starting point of the laser ultrasonic signal, and the propagation time or the propagation speed of the ultrasonic wave excited by the laser is accurately obtained.
The invention also discloses a system which is specially used for the laser ultrasonic nondestructive testing and utilizes the electromagnetic wave as a reference signal. Including pulse laser (1), focusing mirror (2), antenna (3), signal amplifier (4), data acquisition card (5), ultrasonic detector (6), computer (7) and measured object (8), its characterized in that:
the pulse laser (1) is used for generating pulse laser, the excitation is controlled by the computer (7), and single-beam pulse laser light is focused and then acts on the surface of a measured object (8).
The focusing mirror (2) is used for focusing the pulse laser, and the focus of the pulse laser acts on the surface of a measured object (8).
The antenna (3) is used for receiving electromagnetic waves generated by surface radiation of an object to be measured (8).
The ultrasonic detector (6) is used for receiving ultrasonic waves transmitted on the surface or in the measured object (8).
One end of the signal amplifier (4) is connected with the antenna (3) and the ultrasonic detector (6) to respectively realize the amplification of two-channel signals, and the other end of the signal amplifier is connected with the data acquisition card (5) to output signals.
One end of the data acquisition card (5) is connected with the signal amplifier (4), and the other end is connected with the computer (7) to realize signal acquisition and input signals into the computer (7).
The computer (7) is used for realizing the emission control of the pulse laser and signal storage and signal processing.
The invention relates to a method for generating electromagnetic waves and ultrasonic waves by utilizing pulse laser excitation and taking the electromagnetic waves as the starting points of pulse laser excitation ultrasonic signals, which is also characterized in that the method is not limited by ultrasonic detection methods, and the ultrasonic signals obtained by various ultrasonic detection methods can take the electromagnetic waves as reference signals.
The invention has the beneficial effects that:
compared with a laser ultrasonic detection system without a reference signal, the technology greatly improves the accuracy and stability of the detection system.
Compared with the current signal which is used for sending an excitation command to the pulse laser by a computer and is used as a reference signal, the technology can effectively inhibit zero drift caused by temperature change of the laser and the like, and reduce system errors.
Compared with the technology that the light sensor is used for detecting the refraction light of the pulse laser as the reference signal, the technology does not need a light splitting device, has no influence on the excited pulse laser, is simple to operate and is non-contact.
Drawings
In order that the present disclosure may be more readily and clearly understood, reference is now made to the following detailed description of the present disclosure taken in conjunction with the accompanying drawings, in which:
FIG. 1 is a schematic diagram of the system of the present invention;
figure 2 shows electromagnetic and ultrasonic signals received on 304 stainless steel.
Wherein: the device comprises a short pulse laser (1), a focusing mirror (2), an antenna (3), a signal amplifier (4), a data acquisition card (5), an ultrasonic detector (6), a computer (7) and a measured object (8).
Detailed Description
The invention utilizes pulse laser excitation to generate electromagnetic waves and ultrasonic waves, takes the electromagnetic waves as the starting point of the pulse laser excitation ultrasonic wave signal, and comprises the following steps:
the pulse laser is emitted by a short pulse laser (1) controlled by a computer (7), is focused by a focusing mirror (2) and then acts on the object to be measured (8), so that ultrasonic waves are generated and propagate in the object to be measured (8) and on the surface of the object to be measured, and electromagnetic waves generated by ionization of the object to be measured (8) are propagated to the outside.
The electromagnetic wave generated by ionization of the measured object (8) and transmitted to the outside is detected by the antenna (3), the signal is amplified by the signal amplifier (4), and then is collected by the data acquisition card (5) to be used as a channel signal and be recorded into the computer.
The antenna (3) does not need to be in contact with a measured object (8), and non-contact detection is realized.
The ultrasonic wave propagated inside the object to be measured (8) is detected by an ultrasonic detector (6), the signal is amplified by a signal amplifier (4), and then is acquired by a data acquisition card (5) to be used as another channel signal and be recorded into a computer.
The ultrasonic detector (6) comprises various ultrasonic detectors such as a contact type piezoelectric ultrasonic sensor, an air coupling ultrasonic sensor, an optical interferometer and the like without limitation.
After the two-channel signals are stored in a computer, the electromagnetic wave signals are used as starting points, the waveform position of the ultrasonic signals is correspondingly adjusted, and the signals are re-extracted on the basis of the original ultrasonic signals so as to inhibit system errors.
Fig. 2 shows electromagnetic wave signals and ultrasonic wave signals received by the laser ultrasonic method at 304 stainless steel. As shown in the figure, since the signal speed of the electromagnetic wave is the speed of light, the propagation time is considered to be zero, and therefore the electromagnetic wave is considered to be the starting point of the ultrasonic wave. By using the electromagnetic wave as a reference signal, the propagation time or propagation speed of the ultrasonic wave is accurately obtained.
Claims (6)
1. An electromagnetic wave method for determining the starting point of a laser ultrasonic signal, which is characterized in that electromagnetic waves and ultrasonic waves are generated by using pulse laser excitation, and the electromagnetic waves are used as the starting points of the pulse laser excitation ultrasonic signals, comprising the following steps:
(1) when the pulsed laser irradiates the surface of the object to be measured, the surface of the object is ablated to form plasma due to the local high temperature of the pulsed laser so as to radiate electromagnetic waves, and the pulsed laser is excited in the object to be measured to generate ultrasonic waves;
(2) receiving electromagnetic waves by adopting an antenna, and taking the electromagnetic waves as reference signals or zero points for laser ultrasonic signal acquisition;
(3) receiving electromagnetic wave and ultrasonic wave signals through a data acquisition card, and inputting two channel signals into a computer;
(4) the received electromagnetic wave signal is used as the starting point of the laser ultrasonic signal, and the propagation time or the propagation speed of the ultrasonic wave excited by the laser is accurately obtained.
2. The method for generating electromagnetic waves and ultrasonic waves by using pulsed laser excitation and using the electromagnetic waves as the starting points of the pulsed laser excitation ultrasonic signals according to claim 1, characterized in that in the step (1), the pulsed laser generates plasma on the surface of the object to be measured, and the generation and annihilation process of the plasma forms the electromagnetic waves.
3. The method for generating electromagnetic waves and ultrasonic waves by pulsed laser excitation according to claim 1 or 2, wherein the electromagnetic waves are used as the starting point of the pulsed laser excitation ultrasonic signals, and the pulsed laser is excited in the object to be measured to generate ultrasonic waves and propagate inside the material while generating the electromagnetic waves in step (1).
4. The method for generating electromagnetic waves and ultrasonic waves by pulsed laser excitation according to claim 1 or 2, wherein the electromagnetic waves are used as the starting point of the pulsed laser excitation ultrasonic signals, and the electromagnetic waves generated by the pulsed laser in step (2) are detected by an antenna without contacting with the material to be detected, and the signals are A/D converted and input into a computer.
5. The method for generating electromagnetic waves and ultrasonic waves by pulsed laser excitation according to claim 1 or 2, wherein the electromagnetic waves are used as the starting points of the pulsed laser excitation ultrasonic signals, wherein in the steps (2) and (3), the ultrasonic waves excited by the pulsed laser are detected by a plurality of methods including a laser interferometer, a piezoelectric ultrasonic probe, and an air-coupled ultrasonic probe.
6. The method for generating electromagnetic waves and ultrasonic waves by pulsed laser excitation according to claim 1 or 2, wherein the electromagnetic waves are used as the starting points of the signals of the ultrasonic waves excited by the pulsed laser, and the propagation speed of the electromagnetic waves is equal to the speed of light, and the propagation time is extremely short, so that the starting points of the signals of the ultrasonic waves are obtained in step (4).
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Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS58154458A (en) * | 1982-03-10 | 1983-09-13 | Toshiba Corp | Position detecting and correcting device |
| JP2001311615A (en) * | 2000-04-28 | 2001-11-09 | Nkk Corp | Method and apparatus for non-contact ultrasonic thickness measuring |
| CN1818713A (en) * | 2006-03-16 | 2006-08-16 | 秦忠 | Ultrasonic positioning method of active long-range radio-frequency electronic label |
| CN107860716A (en) * | 2017-10-30 | 2018-03-30 | 东北大学 | A kind of lossless detection method and equipment of the elastic constant based on laser-ultrasound |
| CN108802688A (en) * | 2018-07-18 | 2018-11-13 | 上海天豚信息科技有限公司 | Localization method, the space positioning system of object to be measured object in space |
| CN109990829A (en) * | 2018-12-25 | 2019-07-09 | 华中科技大学 | The method and device that a kind of element, defect and residual stress detect simultaneously |
-
2021
- 2021-06-10 CN CN202110646212.7A patent/CN113358577A/en active Pending
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS58154458A (en) * | 1982-03-10 | 1983-09-13 | Toshiba Corp | Position detecting and correcting device |
| JP2001311615A (en) * | 2000-04-28 | 2001-11-09 | Nkk Corp | Method and apparatus for non-contact ultrasonic thickness measuring |
| CN1818713A (en) * | 2006-03-16 | 2006-08-16 | 秦忠 | Ultrasonic positioning method of active long-range radio-frequency electronic label |
| CN107860716A (en) * | 2017-10-30 | 2018-03-30 | 东北大学 | A kind of lossless detection method and equipment of the elastic constant based on laser-ultrasound |
| CN108802688A (en) * | 2018-07-18 | 2018-11-13 | 上海天豚信息科技有限公司 | Localization method, the space positioning system of object to be measured object in space |
| CN109990829A (en) * | 2018-12-25 | 2019-07-09 | 华中科技大学 | The method and device that a kind of element, defect and residual stress detect simultaneously |
Non-Patent Citations (2)
| Title |
|---|
| KYUNG MIN HONG 等: "Preliminary Study of the Measurement of Foreign Material in Galvanic Corrosion Using Laser Ultrasonic", 《JOURNAL OF THE OPTICAL SOCIETY OF KOREA》, vol. 17, no. 4, 31 August 2013 (2013-08-31), pages 323 - 327 * |
| 林中亚等: "激光诱导超声表面波的实验研究", 《科技创新导报》, no. 26, 11 September 2015 (2015-09-11), pages 28 - 29 * |
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Application publication date: 20210907 |