CN113740215A - Method for detecting particles in laser welding plume through cooperation of multiple laser beams - Google Patents
Method for detecting particles in laser welding plume through cooperation of multiple laser beams Download PDFInfo
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- CN113740215A CN113740215A CN202110883185.5A CN202110883185A CN113740215A CN 113740215 A CN113740215 A CN 113740215A CN 202110883185 A CN202110883185 A CN 202110883185A CN 113740215 A CN113740215 A CN 113740215A
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- 239000002245 particle Substances 0.000 title claims abstract description 50
- 238000003466 welding Methods 0.000 title claims abstract description 27
- 238000000034 method Methods 0.000 title claims abstract description 24
- 238000001514 detection method Methods 0.000 claims abstract description 42
- 238000012545 processing Methods 0.000 claims abstract description 9
- 230000000694 effects Effects 0.000 claims abstract description 5
- 239000004065 semiconductor Substances 0.000 claims description 5
- 239000000835 fiber Substances 0.000 claims description 4
- 238000005259 measurement Methods 0.000 abstract description 7
- 230000008859 change Effects 0.000 abstract description 6
- 238000011065 in-situ storage Methods 0.000 abstract description 2
- 230000008569 process Effects 0.000 description 6
- 238000010586 diagram Methods 0.000 description 3
- 238000010521 absorption reaction Methods 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 229910001209 Low-carbon steel Inorganic materials 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000012625 in-situ measurement Methods 0.000 description 1
- 230000001678 irradiating effect Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- 230000000877 morphologic effect Effects 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 239000013307 optical fiber Substances 0.000 description 1
- 238000005498 polishing Methods 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
- G01N15/02—Investigating particle size or size distribution
- G01N15/0205—Investigating particle size or size distribution by optical means
- G01N15/0211—Investigating a scatter or diffraction pattern
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
- G01N15/10—Investigating individual particles
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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
- G01N21/84—Systems specially adapted for particular applications
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Abstract
A method for detecting particles in laser welding plume by cooperation of multiple laser beams belongs to the technical field of laser welding. The measuring system consists of a plurality of detection lasers with different wavelengths, a focusing system, a data acquisition card and a signal processing system. The detection lasers with different wavelengths are respectively focused on the same position in the plume through respective focusing systems, meanwhile, the detection lasers are scattered by particles in the plume, part of scattered light reenters the respective detection lasers to cause a self-mixing effect and change output voltage signals of the detection lasers, and information such as the diameter and the density of the particles can be obtained through processing the output voltage signals. The invention can cooperatively detect the particles at the same position in the plume through the detection lasers with different wavelengths, can ensure that the measurement range of the particle diameter at the measurement position is wider (10 nm-50 mu m), and can more accurately measure the diameter of the particles in the plume and the corresponding density condition thereof in situ in a large range.
Description
Technical Field
The invention relates to a method for cooperatively detecting particles in plume by multiple laser beams, and belongs to the field of laser material processing.
Background
The rapid development of 1 μm-scale lasers (fiber lasers, Nd: YAG lasers, disk lasers and semiconductor lasers) is an important advance in the field of laser science. The laser can be transmitted through the optical fiber, and has the advantages of high absorption rate, high power, high processing flexibility, low running cost and the like when being used for processing metal materials. The plume is an inherent physical phenomenon during laser welding with the wavelength of 1 mu m, and has obvious negative influence on the welding process. The essence of laser welding influenced by the plume is that a large number of particles exist in the plume, and the particles in the plume attenuate laser energy and change the propagation direction of a light beam in modes of absorption, scattering and the like. Therefore, the study on the characteristics of the particles in the plume has guiding significance for diagnosing the welding process and improving the welding process quality.
Currently, studies on the plume include morphological observation of the plume, measurement of the temperature of the plume, and influence of the plume on the welding process, and the like, and the physical characteristics of the plume are known to some extent. However, the current research does not understand the mechanism of plume formation, and there is no direct evidence about the distribution of particles in the plume, the size of the particles, the source of the particles, and the like. In the current stage, the research on the particles in the plume mainly comprises collecting the particles in the plume after the welding process is finished and then measuring the particles. On one hand, collected plume particles are cooled and agglomerated, and the measurement result is not the actual size of the particles in the plume in a light beam, but only the approximate range of the diameter of the plume particles can be obtained; on the other hand, the method cannot obtain the characteristics of the space distribution rule, the motion speed and the like of the particles in the plume.
To solve the above problems, the subject group proposed "a method for in situ measurement of particles in plume", CN 202010245365.6. The size distribution of the particles in the plume can be measured in real time. According to the self-mixing interference effect principle, the resolution measured by the method is half wavelength of the detection laser. However, the diameter of the particles in the plume is between 10nm and 50 μm, and the particles with the diameter smaller than the half wavelength of the detection laser cannot be detected; and the particles with the diameter far larger than the detection laser wavelength have the problems of excessive interference fringes and poor counting.
The invention provides a method for cooperatively detecting the plume by multiple laser beams, which can effectively solve the problems. The detection laser beam emits Mie scattering effect when irradiating on the particles, part of scattered light enters the detection laser to cause the change of output power and frequency, and information such as the diameter, the speed, the distribution condition and the like of the particles is obtained through the collection and processing of received signals. The invention adopts the detection lasers with different wavelengths to simultaneously measure the determined positions in the plume, and the included angle between each two lasers is adjustable within the range of 10-180 degrees, so that more comprehensive and more accurate information can be obtained.
Disclosure of Invention
The invention provides a method for detecting particles in laser welding plumes by cooperation of multiple laser beams. A certain determined position in the plume is synchronously measured through a plurality of detection lasers with different wavelengths, and physical information of particles with the determined positions from nanometer magnitude to micrometer magnitude in the welding process and the plume, such as size, speed, distribution condition and the like, is comprehensively obtained in real time. Compared with the traditional method for collecting the plume particles and measuring by a single probe light feedback type, the method can carry out more detailed and comprehensive accurate measurement.
In order to realize the purpose, a detection system is composed of a detection laser group, an attenuation sheet, a data acquisition card and a computer. During welding, a welding laser beam with the magnitude of 1 mu m is irradiated on a workpiece to generate plume. The detection laser light with a plurality of different wavelengths irradiates particles with determined positions (detection positions) in the plume to generate a Mie scattering effect, and part of scattered light enters a laser cavity to cause the output power and the frequency to change. The photodiode arranged in the semiconductor laser cavity converts the optical signal into an electric signal, the electric signal is collected and stored by a data acquisition card, and finally, Matlab software is used for carrying out signal processing on a computer to obtain a power and frequency change diagram.
In order to achieve the purpose, the technical scheme of the invention is as follows: the focused focal points of the multiple detection laser beams act on the same position in the plume. The number of the detection lasers is more than or equal to 2, and the angle between the detection lasers is adjustable within the range of 10-180 degrees. The output power of the detection laser is 0.01 mW-50W, and the output wavelength is 100 nm-20 μm (the number and wavelength of the detection lasers can be selected according to actual needs, but the same wavelength of the welding laser cannot be used). The diameter of a focusing spot of the detection laser beam is 0.1 mu m-10 mm; the wavelength difference between different detection lasers is between 100nm and 2 mu m. A laser with the wavelength of 1 mu m is used during welding, and can be a fiber laser, an Nd-YAG laser, a disc laser or a semiconductor laser, and the output power is 0.5 kW-100 kW.
The invention has the following advantages: the invention measures the particles in the brilliance through the combination of a plurality of detection semiconductor lasers, on one hand, compared with the traditional method that the brilliance particles are collected after welding is finished, the invention can measure the particles in the welding laser beam in situ and can remove the particles or splash particles outside the beam. Meanwhile, human errors generated by a collecting and measuring method can be avoided, and a real-time result is obtained. On the other hand, compared with a single-beam measurement method, the method can avoid data distortion (small particles cannot be measured and large particles are difficult to count) caused by overlarge difference between the detection light wavelength and the particle diameter, and the obtained particle data is more comprehensive and accurate. In addition, the invention has the advantages of compact and easy collimation system, shared propagation path of the detection light and the feedback light, small volume, easy adjustment, no need of external interference, no influence of the power fluctuation of the detection laser, low cost and the like.
Drawings
FIG. 1: experimental method schematic diagram for multi-beam paraxial measurement of particles in plume
The meaning of the individual reference symbols in the figures: 1.2.3. the method comprises the following steps of detecting a laser group, 4 welding laser beams, 5 welding plates, 6 data acquisition card NI62510, 7 and a computer.
FIG. 2: measuring result graph of detection laser with wavelength of 1.31 mu m
FIG. 3: diagram of measurement results of detection laser with wavelength of 0.639 μm
Detailed Description
In this example, a YLS-6000 fiber laser is used for welding, the welded plate is low carbon steel with the thickness of 10mm and is subjected to grinding and polishing treatment, and the processing parameters are as follows: the welding speed is 2m/min, the laser power is 1kW, the spot diameter is 1.06mm, and the spot acts on the surface of the plate. The detection laser has the wavelengths of 639nm and 1310nm respectively, and is focused by a lens with the focal length of 100mm, and the laser power is 500 mW; signals are collected and stored by a data acquisition card of National Instruments model 6251, and are processed by Matlab software to obtain a voltage spectrogram as shown in fig. 2 and 3. The size, the quantity distribution and the speed change condition of the particles in the plume can be obtained by reading the number of the interference fringes in the image and measuring the relationship between the diameter of the particles and the interference fringes and the wavelength of the detection laser.
The above description is only a preferred embodiment of the present invention, and those skilled in the art will understand that the scope of the present invention is not limited thereto. Any easily conceivable variations or alterations without departing from the principle of the invention are intended to be covered by the scope of protection of the present invention.
Claims (3)
1. A method for detecting particles in laser welding plumes in cooperation with multiple laser beams is characterized in that: the detection lasers are used as a transmitting end and a receiving end, the detection lasers with different wavelengths are focused and simultaneously act on the same measuring position in the plume, particles in the plume reflect detection light and then enter the respective lasers to generate a self-mixing effect, an output voltage signal of each detection laser is measured, the voltage signals are collected and stored through a data acquisition card and then are subjected to signal processing on a computer, and the diameter and the density of the particles are calculated.
2. The method for detecting particles in a laser welding plume cooperatively by multiple laser beams as claimed in claim 1, wherein: the number of the detection lasers is more than or equal to 2, and the wavelength range of the detection lasers is between 0.1 and 20 mu m; the power range of the detection laser is between 0.01mW and 5W; the diameter of a focusing spot of the detection laser beam is 0.1 mu m-10 mm; the wavelength difference between different detection lasers is between 100nm and 2 mu m, and the included angle between the detection lasers is between 10 and 180 degrees.
3. The method for detecting particles in a laser welding plume cooperatively by multiple laser beams as claimed in claim 1, wherein: the welding uses a high-power laser with the magnitude of 1 micron, which is fiber laser, Nd, YAG laser, disc laser or semiconductor laser, and the output power is 0.5kW to 100 kW.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202110883185.5A CN113740215A (en) | 2021-08-02 | 2021-08-02 | Method for detecting particles in laser welding plume through cooperation of multiple laser beams |
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| CN202110883185.5A CN113740215A (en) | 2021-08-02 | 2021-08-02 | Method for detecting particles in laser welding plume through cooperation of multiple laser beams |
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Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1877339A (en) * | 2005-06-10 | 2006-12-13 | 中国科学院空间科学与应用研究中心 | Laser-scattering measuring system for particle speed |
| CN102564909A (en) * | 2011-11-29 | 2012-07-11 | 中国科学院安徽光学精密机械研究所 | Laser self-mixing multi-physical parameter measurement method and device for atmospheric particulate |
| CN104487818A (en) * | 2012-06-19 | 2015-04-01 | 美利坚合众国政府,由海军部长所代表 | Remote multisensor optical particle monitor for flowing fluid systems |
| CN108027312A (en) * | 2015-07-30 | 2018-05-11 | 皇家飞利浦有限公司 | Laser sensor for particle size detection |
| CN111398103A (en) * | 2020-03-31 | 2020-07-10 | 北京工业大学 | Method for measuring particles in light beam in laser welding based on sandwich model constrained plume |
| CN111398107A (en) * | 2020-03-31 | 2020-07-10 | 北京工业大学 | Method for in-situ measurement of particles in laser welding plume |
-
2021
- 2021-08-02 CN CN202110883185.5A patent/CN113740215A/en active Pending
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1877339A (en) * | 2005-06-10 | 2006-12-13 | 中国科学院空间科学与应用研究中心 | Laser-scattering measuring system for particle speed |
| CN102564909A (en) * | 2011-11-29 | 2012-07-11 | 中国科学院安徽光学精密机械研究所 | Laser self-mixing multi-physical parameter measurement method and device for atmospheric particulate |
| CN104487818A (en) * | 2012-06-19 | 2015-04-01 | 美利坚合众国政府,由海军部长所代表 | Remote multisensor optical particle monitor for flowing fluid systems |
| CN108027312A (en) * | 2015-07-30 | 2018-05-11 | 皇家飞利浦有限公司 | Laser sensor for particle size detection |
| CN111398103A (en) * | 2020-03-31 | 2020-07-10 | 北京工业大学 | Method for measuring particles in light beam in laser welding based on sandwich model constrained plume |
| CN111398107A (en) * | 2020-03-31 | 2020-07-10 | 北京工业大学 | Method for in-situ measurement of particles in laser welding plume |
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