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RSS2023 Vol. 47, No. 2
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2023, 47(2): 147-153.
doi: 10.7510/jgjs.issn.1001-3806.2023.02.001
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Abstract:
In order to improve the performance of aluminum/steel connection, an unequal thickness aluminum/steel pair welding head whose tensile strength is 40% of that of the aluminum alloy base metal was obtained using the laser technology by adjusting the process parameters. The joint weld structure, interface compounds, and mechanical properties were analyzed. The results show that the welding speed is 1.8 m/min, the laser is biased to the steel side by 0.3 mm, the defocusing amount is 0 mm, the laser power is 3.0 kW, and the tensile strength of the joint reaches 38 MPa, respectively. With the other welding parameters unchanged, when the defocus amount is -2 mm, the tensile strength of the joint is further increased to 57.7 MPa, the shape of the weld section changes from wine cup shape to corset waist, the fusion line is more neat, and the cracks and porosity defects near it are significantly reduced. Phase diffraction and energy dispersive spectrometer in the interface area of the weld showed that the compounds grown vertically along the fusion line were FeAl, FeAl3, Fe2Al5 and Fe2CrAl and Fe3Al with different degrees of brittleness. The overall tensile fracture mode of the joint is brittle fracture, the connection strength at some positions on the fracture surface is good, showing a concave shape, and Fe3Al is found through inspection Fe3Al. The results of this study are improving the performance of aluminum/steel joints in the bodywork, weight reduction and energy saving and emission reduction are of great practical significance.
In order to improve the performance of aluminum/steel connection, an unequal thickness aluminum/steel pair welding head whose tensile strength is 40% of that of the aluminum alloy base metal was obtained using the laser technology by adjusting the process parameters. The joint weld structure, interface compounds, and mechanical properties were analyzed. The results show that the welding speed is 1.8 m/min, the laser is biased to the steel side by 0.3 mm, the defocusing amount is 0 mm, the laser power is 3.0 kW, and the tensile strength of the joint reaches 38 MPa, respectively. With the other welding parameters unchanged, when the defocus amount is -2 mm, the tensile strength of the joint is further increased to 57.7 MPa, the shape of the weld section changes from wine cup shape to corset waist, the fusion line is more neat, and the cracks and porosity defects near it are significantly reduced. Phase diffraction and energy dispersive spectrometer in the interface area of the weld showed that the compounds grown vertically along the fusion line were FeAl, FeAl3, Fe2Al5 and Fe2CrAl and Fe3Al with different degrees of brittleness. The overall tensile fracture mode of the joint is brittle fracture, the connection strength at some positions on the fracture surface is good, showing a concave shape, and Fe3Al is found through inspection Fe3Al. The results of this study are improving the performance of aluminum/steel joints in the bodywork, weight reduction and energy saving and emission reduction are of great practical significance.
2023, 47(2): 154-170.
doi: 10.7510/jgjs.issn.1001-3806.2023.02.002
Abstract:
1.7 μm waveband covers many molecular absorption lines and is located in the transparent window of living tissue.This band laser source has important applications in material processing, mid infrared laser generation, gas detection, medical surgery, and biological imaging. The research progress and the related applications of 1.7 μm waveband laser were summarized at home and abroad in this paper, and the work of Changchun University of Science and Technology in this field was introduced. Although the research and application of 1.7 μm waveband fiber laser still face a series of problems, it is reasonable to believe that with the continuous improvement of the related technologies, 1.7 μm waveband high-performance fiber laser will develop rapidly.
1.7 μm waveband covers many molecular absorption lines and is located in the transparent window of living tissue.This band laser source has important applications in material processing, mid infrared laser generation, gas detection, medical surgery, and biological imaging. The research progress and the related applications of 1.7 μm waveband laser were summarized at home and abroad in this paper, and the work of Changchun University of Science and Technology in this field was introduced. Although the research and application of 1.7 μm waveband fiber laser still face a series of problems, it is reasonable to believe that with the continuous improvement of the related technologies, 1.7 μm waveband high-performance fiber laser will develop rapidly.
2023, 47(2): 171-177.
doi: 10.7510/jgjs.issn.1001-3806.2023.02.003
Abstract:
In order to solve the problem of discoloration, melting and falling off of artificial speckles when the conventional digital image correlation method is applied to thermal strain measurement under high temperature conditions, the laser speckle was used as the characteristic texture method of the digital image correlation method. The correlation of speckle images before and after temperature change to measure metal thermal strain was calculated, experiments of heating specimens in a non-vacuum environment were carried out, the artificial speckle and laser tests on aluminum and tungsten specimens in a tubular heating furnace respectively vacuum heating experimental comparison of speckle were conducted.The corresponding speckle images were obtained and the mean strain curve data were calculated. The results show that in the non-vacuum environment, the laser speckle image jitters greatly due to the disturbance of heat flow, and the measured thermal strain curve has large interference noise. The thermal strain of aluminum with the temperature increases from room temperature to 450 ℃ and the thermal strain of tungsten with the temperature increases from room temperature to 800 ℃ is respectively consistent with the artificial speckle results. This study shows that the laser speckle digital image correlation method can effectively measure the dynamic thermal strain of the metal wall under the conditions of high vacuum and high heat flow similar to the fusion reactor divertor, which provides a new idea for the damage diagnosis of the first wall material of the fusion reactor divertor.
In order to solve the problem of discoloration, melting and falling off of artificial speckles when the conventional digital image correlation method is applied to thermal strain measurement under high temperature conditions, the laser speckle was used as the characteristic texture method of the digital image correlation method. The correlation of speckle images before and after temperature change to measure metal thermal strain was calculated, experiments of heating specimens in a non-vacuum environment were carried out, the artificial speckle and laser tests on aluminum and tungsten specimens in a tubular heating furnace respectively vacuum heating experimental comparison of speckle were conducted.The corresponding speckle images were obtained and the mean strain curve data were calculated. The results show that in the non-vacuum environment, the laser speckle image jitters greatly due to the disturbance of heat flow, and the measured thermal strain curve has large interference noise. The thermal strain of aluminum with the temperature increases from room temperature to 450 ℃ and the thermal strain of tungsten with the temperature increases from room temperature to 800 ℃ is respectively consistent with the artificial speckle results. This study shows that the laser speckle digital image correlation method can effectively measure the dynamic thermal strain of the metal wall under the conditions of high vacuum and high heat flow similar to the fusion reactor divertor, which provides a new idea for the damage diagnosis of the first wall material of the fusion reactor divertor.
2023, 47(2): 178-184.
doi: 10.7510/jgjs.issn.1001-3806.2023.02.004
Abstract:
In order to solve the problem of the influence of different optical coherence tomography (OCT) image preprocessing methods on scattering coefficient calculation in dermis, and to improve the accuracy of noninvasive blood glucose detection, an optimization method of early OCT image data processing was proposed. The 3-D images were first processed by skin surface alignment, 3-D reconstruction and 1-D average, and then the background noise and data normalization effect on the accuracy of blood glucose prediction were analyzed by clinical experiments. The results show that the prediction error decreases by 18.31% compared with that before pretreatment. This study has important reference value for improving the accuracy of optical noninvasive blood glucose detection using OCT.
In order to solve the problem of the influence of different optical coherence tomography (OCT) image preprocessing methods on scattering coefficient calculation in dermis, and to improve the accuracy of noninvasive blood glucose detection, an optimization method of early OCT image data processing was proposed. The 3-D images were first processed by skin surface alignment, 3-D reconstruction and 1-D average, and then the background noise and data normalization effect on the accuracy of blood glucose prediction were analyzed by clinical experiments. The results show that the prediction error decreases by 18.31% compared with that before pretreatment. This study has important reference value for improving the accuracy of optical noninvasive blood glucose detection using OCT.
2023, 47(2): 185-192.
doi: 10.7510/jgjs.issn.1001-3806.2023.02.005
Abstract:
In order to optimize the laser welding process of bulk metallic glass(BMG) and crystalline metals, a pulsed infrared laser with a maximum average power of 300 W was used to weld Zr-based bulk metallic glass Zr57Nb5Cu15.4Ni12.6Al10 and 440, 304, and 17-4PH stainless steel. The micro-structure, composition, and mechanical properties of experimental welded joints were characterized by material analysis and mechanical testing. Moreover, appropriate laser offset welding process parameters, micro-structure properties, and mechanical properties of welded joints were obtained. The results show that the laser focus shift 0.2 mm~0.3 mm to the side of stainless steel can make the welding evenly and improve the bending strength effectively. The bending strength of bulk metallic glass and 17-4PH joint can reach 339 MPa by appropriate welding process. The laser welded joints of Zr-based bulk metallic glass and stainless steel are mainly divided into melting mixing zone and heat affected zone. Dendritic and granular crystalline structures were found in the melting and mixing zone. The bending strength can be increased by 14%~48% after low temperature annealing treatment. The results of this study have guiding significance for the expansion of Zr- based bulk metallic glass in various fields.
In order to optimize the laser welding process of bulk metallic glass(BMG) and crystalline metals, a pulsed infrared laser with a maximum average power of 300 W was used to weld Zr-based bulk metallic glass Zr57Nb5Cu15.4Ni12.6Al10 and 440, 304, and 17-4PH stainless steel. The micro-structure, composition, and mechanical properties of experimental welded joints were characterized by material analysis and mechanical testing. Moreover, appropriate laser offset welding process parameters, micro-structure properties, and mechanical properties of welded joints were obtained. The results show that the laser focus shift 0.2 mm~0.3 mm to the side of stainless steel can make the welding evenly and improve the bending strength effectively. The bending strength of bulk metallic glass and 17-4PH joint can reach 339 MPa by appropriate welding process. The laser welded joints of Zr-based bulk metallic glass and stainless steel are mainly divided into melting mixing zone and heat affected zone. Dendritic and granular crystalline structures were found in the melting and mixing zone. The bending strength can be increased by 14%~48% after low temperature annealing treatment. The results of this study have guiding significance for the expansion of Zr- based bulk metallic glass in various fields.
Optical breakdown and plasma morphology distribution of double droplets induced by femtosecond laser
2023, 47(2): 193-199.
doi: 10.7510/jgjs.issn.1001-3806.2023.02.006
Abstract:
In order to investigate the optical breakdown and plasma distribution during the interaction between ultrashort laser pulses and double droplets, based on the nonlinear Maxwell's equations and the ionization rate equation, a transient coupled model of femtosecond laser and double droplets was constructed by finite element analysis. The free electron density and laser field distribution of micron-sized double droplets irradiated by femtosecond laser were calculated, and the effects of double-droplet structures on droplet optical breakdown and plasmonic changes were obtained. The results show that the breakdown threshold of the second droplet is approximately 35% of that of a single droplet under the same conditions. The plasma morphology and the location of the breakdown point vary with the distance between the double droplets, and a nanoplasma jet is generated in focused region. In addition, the absorption of laser energy by the second droplet decreases with increasing distance between the double droplets. The energy absorption of the double droplets is about 3% of that of the single droplet when incident with both laser intensity satisfying their breakdown threshold. The absorption of laser energy by the second droplet increases with the increase of laser intensity, and the energy absorption ratio eventually tends to 0.01, which is only 1.5% of that of a single droplet. The investigation provides a certain reference for laser-induced water breakdown and the transmission of laser in the atmosphere.
In order to investigate the optical breakdown and plasma distribution during the interaction between ultrashort laser pulses and double droplets, based on the nonlinear Maxwell's equations and the ionization rate equation, a transient coupled model of femtosecond laser and double droplets was constructed by finite element analysis. The free electron density and laser field distribution of micron-sized double droplets irradiated by femtosecond laser were calculated, and the effects of double-droplet structures on droplet optical breakdown and plasmonic changes were obtained. The results show that the breakdown threshold of the second droplet is approximately 35% of that of a single droplet under the same conditions. The plasma morphology and the location of the breakdown point vary with the distance between the double droplets, and a nanoplasma jet is generated in focused region. In addition, the absorption of laser energy by the second droplet decreases with increasing distance between the double droplets. The energy absorption of the double droplets is about 3% of that of the single droplet when incident with both laser intensity satisfying their breakdown threshold. The absorption of laser energy by the second droplet increases with the increase of laser intensity, and the energy absorption ratio eventually tends to 0.01, which is only 1.5% of that of a single droplet. The investigation provides a certain reference for laser-induced water breakdown and the transmission of laser in the atmosphere.
2023, 47(2): 200-204.
doi: 10.7510/jgjs.issn.1001-3806.2023.02.007
Abstract:
In order to solve the problem of poor target location accuracy in wide-field infrared alarm system, a polynomial fitting method based on active markers was used to extract target location in wide-field infrared alarm system. A high-temperature ceramic heating plate was used to simulate an infrared target, and a high-precision 2-D turntable was used to obtain the corresponding data point set of the camera's attitude angle and the target center coordinates, and a binary high-order polynomial was used to fit the target orientation information. The high-precision azimuth extraction of the target in the large-field infrared warning system was realized. The experimental results show that the angle error of the fitting method is within ±0.1°, and the target positioning accuracy is high. This result is helpful for target azimuth extraction in large-field infrared imaging.
In order to solve the problem of poor target location accuracy in wide-field infrared alarm system, a polynomial fitting method based on active markers was used to extract target location in wide-field infrared alarm system. A high-temperature ceramic heating plate was used to simulate an infrared target, and a high-precision 2-D turntable was used to obtain the corresponding data point set of the camera's attitude angle and the target center coordinates, and a binary high-order polynomial was used to fit the target orientation information. The high-precision azimuth extraction of the target in the large-field infrared warning system was realized. The experimental results show that the angle error of the fitting method is within ±0.1°, and the target positioning accuracy is high. This result is helpful for target azimuth extraction in large-field infrared imaging.
2023, 47(2): 205-213.
doi: 10.7510/jgjs.issn.1001-3806.2023.02.008
Abstract:
Due to the properties of real-time, medium-free, and non-invasive, the optical Doppler effect based non-invasive blood flow measurement is valuable and has a promising future in clinical and other fields. At present, there are three optical non-invasive blood flow measurement technologies: laser Doppler blood flow measurement technology, optical coherence tomography Doppler imaging technology, and photo-acoustic Doppler blood flow measurement technology. The principles of the above three technologies were briefly analyzed, the respective development status was described, and the future and development of these new technologies were exhibited.
Due to the properties of real-time, medium-free, and non-invasive, the optical Doppler effect based non-invasive blood flow measurement is valuable and has a promising future in clinical and other fields. At present, there are three optical non-invasive blood flow measurement technologies: laser Doppler blood flow measurement technology, optical coherence tomography Doppler imaging technology, and photo-acoustic Doppler blood flow measurement technology. The principles of the above three technologies were briefly analyzed, the respective development status was described, and the future and development of these new technologies were exhibited.
2023, 47(2): 214-219.
doi: 10.7510/jgjs.issn.1001-3806.2023.02.009
Abstract:
In order to realize the high speed and high precision control of the imaging beam for the deep space detection system, the theoretical analysis and experimental verification of the fast steering mirror (FSM) driven by the voice coil actuators (VCA) were carried out with a ⌀50 mm×4 mm silicon mirror as the load. At first, the drive mechanism, configuration, and mathematical model of the FSM were presented. Then the finite element method was used to study the influence of the coil, permanent magnet and air gap size of the VCA on the driving torque. Finally, a prototype of abovementioned FSM was designed, produced, and tested, respectively. The result indicates that, the angular stroke of the FSM is greater than ±1°, and the 3 dB bandwidth is greater than 500 Hz. The procedure disclosed here is helpful for FSM to be applied in the fields of deep space detection, laser communication, photoelectric countermeasure, etc.
In order to realize the high speed and high precision control of the imaging beam for the deep space detection system, the theoretical analysis and experimental verification of the fast steering mirror (FSM) driven by the voice coil actuators (VCA) were carried out with a ⌀50 mm×4 mm silicon mirror as the load. At first, the drive mechanism, configuration, and mathematical model of the FSM were presented. Then the finite element method was used to study the influence of the coil, permanent magnet and air gap size of the VCA on the driving torque. Finally, a prototype of abovementioned FSM was designed, produced, and tested, respectively. The result indicates that, the angular stroke of the FSM is greater than ±1°, and the 3 dB bandwidth is greater than 500 Hz. The procedure disclosed here is helpful for FSM to be applied in the fields of deep space detection, laser communication, photoelectric countermeasure, etc.
2023, 47(2): 220-224.
doi: 10.7510/jgjs.issn.1001-3806.2023.02.010
Abstract:
For the sake of studying the initial position's influence of electrons on the trajectory and spatial angular radiation of high-energy electrons in circularly polarized laser pulses, the spatial motion equation of high-energy electrons was deduced theoretically on the basis of nonlinear Thomson scattering model, energy equation, Lagrange equation, and in combination with the assistance of MATLAB numerical simulation, the spatial motion trajectory diagram and spatial angular radiation simulation diagram of high-energy electrons made. The results show that, under the action of the transverse vortex force, the front trajectory of the electron in the whole space is in a tightly separated spiral shape, and the rear trajectory is composed of sparse circles with distant spatial spacing. With the right shift of the initial position of the electron, the value of the polar angle θ and azimuth ϕ has a decreasing trend when the spatial angular radiation reaches the maximum. Specifically, it becomes stable when z0=5λ0 and (θ, ϕ)=(23.5°, 175.5°). Therefore the change of the initial position of the electron in the laser pulse has a great influence on the trajectory and spatial angular radiation of the electron, which creates the groundwork for the subsequent research of the initial position's influence of the electron on the radiation characteristics of high-energy electrons.
For the sake of studying the initial position's influence of electrons on the trajectory and spatial angular radiation of high-energy electrons in circularly polarized laser pulses, the spatial motion equation of high-energy electrons was deduced theoretically on the basis of nonlinear Thomson scattering model, energy equation, Lagrange equation, and in combination with the assistance of MATLAB numerical simulation, the spatial motion trajectory diagram and spatial angular radiation simulation diagram of high-energy electrons made. The results show that, under the action of the transverse vortex force, the front trajectory of the electron in the whole space is in a tightly separated spiral shape, and the rear trajectory is composed of sparse circles with distant spatial spacing. With the right shift of the initial position of the electron, the value of the polar angle θ and azimuth ϕ has a decreasing trend when the spatial angular radiation reaches the maximum. Specifically, it becomes stable when z0=5λ0 and (θ, ϕ)=(23.5°, 175.5°). Therefore the change of the initial position of the electron in the laser pulse has a great influence on the trajectory and spatial angular radiation of the electron, which creates the groundwork for the subsequent research of the initial position's influence of the electron on the radiation characteristics of high-energy electrons.
2023, 47(2): 225-232.
doi: 10.7510/jgjs.issn.1001-3806.2023.02.011
Abstract:
In order to improve the performance of electrical equipment, it is urgent to develop new high performance contact materials for electric power system. A novel preparation method of graphene/copper composite contacts was presented in this paper. The Ni-Cu alloy transition layer was prepared on the surface of copper (mass fraction was 0.999) by plasma-assisted processing. On such a transition layer, the graphene surface film was prepared by a high-powered continuous-wave laser in situ, covering the surface of copper as an independent coating to resist the damage of contact material. The plasma-assisted processing and laser processing processes of graphene composite contact materials were explored. The results show that the graphene/copper-based contact materials have excellent electrical characteristics, the resistance is similar to red copper, hardness is 1.8 times that of red copper, friction coefficient is only 0.06. This work can provide a new solution and a new material system for electrical materials.
In order to improve the performance of electrical equipment, it is urgent to develop new high performance contact materials for electric power system. A novel preparation method of graphene/copper composite contacts was presented in this paper. The Ni-Cu alloy transition layer was prepared on the surface of copper (mass fraction was 0.999) by plasma-assisted processing. On such a transition layer, the graphene surface film was prepared by a high-powered continuous-wave laser in situ, covering the surface of copper as an independent coating to resist the damage of contact material. The plasma-assisted processing and laser processing processes of graphene composite contact materials were explored. The results show that the graphene/copper-based contact materials have excellent electrical characteristics, the resistance is similar to red copper, hardness is 1.8 times that of red copper, friction coefficient is only 0.06. This work can provide a new solution and a new material system for electrical materials.
2023, 47(2): 233-240.
doi: 10.7510/jgjs.issn.1001-3806.2023.02.012
Abstract:
In order to solve the problems that it is difficult to separate the cable support from the cable in the point cloud of underground cable tunnel and the cable points need to be extracted manually, an automatic extraction and segmentation algorithm of underground cable point cloud based on regional cylindrical surface fitting and robust adaptive Kalman filter was proposed. Firstly, the radius of the cable area was determined based on the shape of the cylindrical axis; Then, the axis of the initial regional cable was taken as the direction of the regional cable, and the extension of the central axis of the cable was estimated combined with the robust adaptive Kalman filter algorithm to obtain the central axis of a single complete cable. Finally, the single segmentation of the cable point cloud was realized. The results show that the mean square error of unit weight in the initial area of cable is less than 0.015 m, which can effectively distinguish cable points from other types of points; The cable central axis extension has disadvantages in the underground cable point cloud, and the noise still maintains a robust estimation, which has good robustness. This method effectively improves the accuracy and reliability of underground cable extraction.
In order to solve the problems that it is difficult to separate the cable support from the cable in the point cloud of underground cable tunnel and the cable points need to be extracted manually, an automatic extraction and segmentation algorithm of underground cable point cloud based on regional cylindrical surface fitting and robust adaptive Kalman filter was proposed. Firstly, the radius of the cable area was determined based on the shape of the cylindrical axis; Then, the axis of the initial regional cable was taken as the direction of the regional cable, and the extension of the central axis of the cable was estimated combined with the robust adaptive Kalman filter algorithm to obtain the central axis of a single complete cable. Finally, the single segmentation of the cable point cloud was realized. The results show that the mean square error of unit weight in the initial area of cable is less than 0.015 m, which can effectively distinguish cable points from other types of points; The cable central axis extension has disadvantages in the underground cable point cloud, and the noise still maintains a robust estimation, which has good robustness. This method effectively improves the accuracy and reliability of underground cable extraction.
2023, 47(2): 247-252.
doi: 10.7510/jgjs.issn.1001-3806.2023.02.014
Abstract:
In order to improve the dynamic pointing accuracy of electro-directional infrared targets during mount flight, under the condition that the the update frequency of position information is difficult to increase due to the hardware limit, a solution for the Kalman filter algorithm was proposed to predict the position information of the target and to increase the update rate. The model of dynamic pointing error based on factors such as flight speed, attitude, and sampling frequency of position information is established. Theoretical analysis and experimental verification were carried out. The results show that when the position sampling rate of the infrared target system is increased from 5 Hz to 10 Hz during the uniform linear flight, the pointing angle error is reduced by 54.66%. This study provides a useful attempt to reduce the dynamic pointing error of directional radiative infrared targets based on existing conditions.
In order to improve the dynamic pointing accuracy of electro-directional infrared targets during mount flight, under the condition that the the update frequency of position information is difficult to increase due to the hardware limit, a solution for the Kalman filter algorithm was proposed to predict the position information of the target and to increase the update rate. The model of dynamic pointing error based on factors such as flight speed, attitude, and sampling frequency of position information is established. Theoretical analysis and experimental verification were carried out. The results show that when the position sampling rate of the infrared target system is increased from 5 Hz to 10 Hz during the uniform linear flight, the pointing angle error is reduced by 54.66%. This study provides a useful attempt to reduce the dynamic pointing error of directional radiative infrared targets based on existing conditions.
2023, 47(2): 253-259.
doi: 10.7510/jgjs.issn.1001-3806.2023.02.015
Abstract:
In order to explore the influence of different cooling methods on laser machining, three different cooling methods of water, gas, and gas-water composite were used to assist laser processing of carbon fiber reinforced plastics. At the same time, the effect of different processing conditions on machining quality was studied by a single factor experiment, and the mechanism of different cooling methods was analyzed. The results show that the heated affected zone (HAZ) and groove depth decrease with the decrease of power and frequency and decrease with the increase of velocity. Under the same process parameters, the HAZ produced by gas-water-assisted laser processing is the smallest, followed by gas-assisted laser processing and the largest by water-assisted laser processing. When the laser power is 2250 W, the frequency is 1200 Hz, and the speed is 120 mm/s, the HAZ of water, gas, and water-gas composite cooling modes are 378 μm, 283 μm, 196 μm, respectively, and the groove depth is 401 μm, 789 μm, 647 μm, respectively. It can be seen from the comprehensive comparison that gas-water-assisted laser machining can achieve a better balance between heat and cold and obtain the best processing quality. This study provides a reference for better realization of low-damage machining of carbon fiber reinforced plastics.
In order to explore the influence of different cooling methods on laser machining, three different cooling methods of water, gas, and gas-water composite were used to assist laser processing of carbon fiber reinforced plastics. At the same time, the effect of different processing conditions on machining quality was studied by a single factor experiment, and the mechanism of different cooling methods was analyzed. The results show that the heated affected zone (HAZ) and groove depth decrease with the decrease of power and frequency and decrease with the increase of velocity. Under the same process parameters, the HAZ produced by gas-water-assisted laser processing is the smallest, followed by gas-assisted laser processing and the largest by water-assisted laser processing. When the laser power is 2250 W, the frequency is 1200 Hz, and the speed is 120 mm/s, the HAZ of water, gas, and water-gas composite cooling modes are 378 μm, 283 μm, 196 μm, respectively, and the groove depth is 401 μm, 789 μm, 647 μm, respectively. It can be seen from the comprehensive comparison that gas-water-assisted laser machining can achieve a better balance between heat and cold and obtain the best processing quality. This study provides a reference for better realization of low-damage machining of carbon fiber reinforced plastics.
2023, 47(2): 260-266.
doi: 10.7510/jgjs.issn.1001-3806.2023.02.016
Abstract:
In order to explore the visual characteristics for different ages, the method of stereo color gamut was used to establish the visual perception model for different ages in the display system. Taking the stereo color gamut based on the CIEL*A*B* color space as the standard, stereo gamut data was obtained for different age observers. The results show that from the photometric point of view, the increase of age will lead to a small decrease in the peak response of the photopic spectral luminous efficiency function, and the peak position moves to the long wavelength on the wavelength axis; from the chromaticity point of view, the color gamut volume is reduced by about 1/3 from 1.73×106 in 20-years-old to 1.16×106 in 60-years-old, and this reduction is concentrated in the middle and high brightness planes. Further analysis of the relationship between wavelength and stereo color gamut, the green light source is found to have the greatest effect on the stereo color gamut for all age observers, and the optimal wavelength selection is recommended 520 nm for all observers. The research can provide design guidance between the color gamut, wavelength and brightness of display systems for different age observers.
In order to explore the visual characteristics for different ages, the method of stereo color gamut was used to establish the visual perception model for different ages in the display system. Taking the stereo color gamut based on the CIEL*A*B* color space as the standard, stereo gamut data was obtained for different age observers. The results show that from the photometric point of view, the increase of age will lead to a small decrease in the peak response of the photopic spectral luminous efficiency function, and the peak position moves to the long wavelength on the wavelength axis; from the chromaticity point of view, the color gamut volume is reduced by about 1/3 from 1.73×106 in 20-years-old to 1.16×106 in 60-years-old, and this reduction is concentrated in the middle and high brightness planes. Further analysis of the relationship between wavelength and stereo color gamut, the green light source is found to have the greatest effect on the stereo color gamut for all age observers, and the optimal wavelength selection is recommended 520 nm for all observers. The research can provide design guidance between the color gamut, wavelength and brightness of display systems for different age observers.
2023, 47(2): 267-272.
doi: 10.7510/jgjs.issn.1001-3806.2023.02.017
Abstract:
In order to efficiently and accurately filter out the influence of suspended particles such as cloud smoke on laser imaging fuze, a target recognition method based on the combination of improved Harris+ smallest univalue segment assimilating nucleus (SUSAN) corner detection algorithm and rectangularity was proposed. Based on the original Harris and SUSAN algorithms, the 8-neighborhood template standard deviation was used to perform the initial screening of target pixels to obtain candidate corner points, and after Gaussian filtering, the improved corner point response function value was used for secondary screening, and then the final corner point was obtained by non-maximum suppression, and finally the target and interference were quadratically distinguished by the rectangularity. Through theoretical analysis and experimental verification, 95% of the targets can be effectively identified. The results show that the proposed method can efficiently and accurately distinguish between target and interference, while meeting the real-time requirements, and provides a theoretical reference for the anti-interference of laser imaging fuze.
In order to efficiently and accurately filter out the influence of suspended particles such as cloud smoke on laser imaging fuze, a target recognition method based on the combination of improved Harris+ smallest univalue segment assimilating nucleus (SUSAN) corner detection algorithm and rectangularity was proposed. Based on the original Harris and SUSAN algorithms, the 8-neighborhood template standard deviation was used to perform the initial screening of target pixels to obtain candidate corner points, and after Gaussian filtering, the improved corner point response function value was used for secondary screening, and then the final corner point was obtained by non-maximum suppression, and finally the target and interference were quadratically distinguished by the rectangularity. Through theoretical analysis and experimental verification, 95% of the targets can be effectively identified. The results show that the proposed method can efficiently and accurately distinguish between target and interference, while meeting the real-time requirements, and provides a theoretical reference for the anti-interference of laser imaging fuze.
2023, 47(2): 273-279.
doi: 10.7510/jgjs.issn.1001-3806.2023.02.018
Abstract:
In order to improve the location of laser spot center accuracy in semiconductor laser processing, according to the gray distribution characteristics of spot image generated after picosecond ultra-short pulse laser irradiating monocrystalline silicon, an algorithm of laser spot center location based on gray histogram was proposed. Through simulation analysis of laser spot and monocrystalline silicon etching experiment, the positioning accuracy of the proposed algorithm was compared with that of the traditional algorithm under different irradiation time and laser power. Results show that under different irradiation times, the algorithm precision is 0.761 μm, 51.3% higher than that of gray centroid method and 93.9% higher than that of the maximum column gray value method. Under different laser power, the algorithm precision is 0.793 μm, 73.4% higher than that of gray centroid method and 86.8% higher than that of the maximum column gray value method. It can provide guidance for the design of the control system for spot center positioning of picosecond ultra-short pulse laser.
In order to improve the location of laser spot center accuracy in semiconductor laser processing, according to the gray distribution characteristics of spot image generated after picosecond ultra-short pulse laser irradiating monocrystalline silicon, an algorithm of laser spot center location based on gray histogram was proposed. Through simulation analysis of laser spot and monocrystalline silicon etching experiment, the positioning accuracy of the proposed algorithm was compared with that of the traditional algorithm under different irradiation time and laser power. Results show that under different irradiation times, the algorithm precision is 0.761 μm, 51.3% higher than that of gray centroid method and 93.9% higher than that of the maximum column gray value method. Under different laser power, the algorithm precision is 0.793 μm, 73.4% higher than that of gray centroid method and 86.8% higher than that of the maximum column gray value method. It can provide guidance for the design of the control system for spot center positioning of picosecond ultra-short pulse laser.
2023, 47(2): 280-285.
doi: 10.7510/jgjs.issn.1001-3806.2023.02.019
Abstract:
In order to further reduce the cost and to improve the imaging speed and accuracy, a full field time-domain optical coherence tomography (OCT) system based on light-emitting diode (LED) illumination was proposed. The LED was used as the light source and the closed-loop four-step phase-shifting method with feedback was used to collect signals. Its imaging principle was described, and the system structure was studied, theoretical analysis and experimental verification were carried out. The results show that the coherence length of the system is 23 μm, the axial resolution is 11.8 μm, the lateral resolution is 19.8 μm, and the acquisition time of single image is 2.15 ms, respectively. Compared with the previous OCT scanning methods, the implementation cost is reduced by this method, and the scanning rate and accuracy is respectively faster and higher, which meaning great application value. This research provides a reference for the development of ultra-high speed, high precision and low-cost OCT system.
In order to further reduce the cost and to improve the imaging speed and accuracy, a full field time-domain optical coherence tomography (OCT) system based on light-emitting diode (LED) illumination was proposed. The LED was used as the light source and the closed-loop four-step phase-shifting method with feedback was used to collect signals. Its imaging principle was described, and the system structure was studied, theoretical analysis and experimental verification were carried out. The results show that the coherence length of the system is 23 μm, the axial resolution is 11.8 μm, the lateral resolution is 19.8 μm, and the acquisition time of single image is 2.15 ms, respectively. Compared with the previous OCT scanning methods, the implementation cost is reduced by this method, and the scanning rate and accuracy is respectively faster and higher, which meaning great application value. This research provides a reference for the development of ultra-high speed, high precision and low-cost OCT system.
2023, 47(2): 286-292.
doi: 10.7510/jgjs.issn.1001-3806.2023.02.020
Abstract:
In order to detect the age of aged Baijiu quickly and accurately, 3-D fluorescence spectra of aged Baijiu and base wine were analyzed by parallel factor algorithm and spectral similarity algorithm. The determination functions of volume fraction of high age base wine and age determination functions of aged Baijiu were established respectively. The results show that the determination error of volume fraction of high age base wine did not exceed 0.02, the average spiked recovery was 100.28%, and the error of age determination was less than 1 year; the method based on 3-D fluorescence spectra for rapid determination of age of aged Baijiu solved the difficulty of age identification due to the complexity of 3-D fluorescence spectra of 3 base wine formulations of aged Baijiu. This study provides a reference for the problem of age detection of aged Baijiu formulated with multiple base wines and the determination of the volume fraction of base wine among aged Baijiu.
In order to detect the age of aged Baijiu quickly and accurately, 3-D fluorescence spectra of aged Baijiu and base wine were analyzed by parallel factor algorithm and spectral similarity algorithm. The determination functions of volume fraction of high age base wine and age determination functions of aged Baijiu were established respectively. The results show that the determination error of volume fraction of high age base wine did not exceed 0.02, the average spiked recovery was 100.28%, and the error of age determination was less than 1 year; the method based on 3-D fluorescence spectra for rapid determination of age of aged Baijiu solved the difficulty of age identification due to the complexity of 3-D fluorescence spectra of 3 base wine formulations of aged Baijiu. This study provides a reference for the problem of age detection of aged Baijiu formulated with multiple base wines and the determination of the volume fraction of base wine among aged Baijiu.
