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RSS2023 Vol. 47, No. 3
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2023, 47(3): 293-300.
doi: 10.7510/jgjs.issn.1001-3806.2023.03.001
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Abstract:
In order to solve the problem of insufficient tracking accuracy of high precision electro optical tracking system (ETS) and to improve its ability to deal with uncertainty, a fuzzy sliding mode control method was designed first. The fuzzy logic control was used to adaptively adjust the switching term parameters of the sliding mode control (SMC) on line. Secondly, an interval type 2 fuzzy sliding mode control (IT2FSMC) method was designed to improve the ability of the system to deal with the uncertainty, and then to improve the tracking accuracy, so as to reduce the chattering of SMC. In addition, particle swarm optimization algorithm was used to ensure that the selected SMC parameters are relatively optimal. The proposed control methods were analyzed theoretically and compared experimentally. The results show that IT2FSMC can reduce SMC steady state error by 54.43% while reducing the chattering of SMC. Simulation and experimental analysis verify the effectiveness of the proposed control method in ETS.
In order to solve the problem of insufficient tracking accuracy of high precision electro optical tracking system (ETS) and to improve its ability to deal with uncertainty, a fuzzy sliding mode control method was designed first. The fuzzy logic control was used to adaptively adjust the switching term parameters of the sliding mode control (SMC) on line. Secondly, an interval type 2 fuzzy sliding mode control (IT2FSMC) method was designed to improve the ability of the system to deal with the uncertainty, and then to improve the tracking accuracy, so as to reduce the chattering of SMC. In addition, particle swarm optimization algorithm was used to ensure that the selected SMC parameters are relatively optimal. The proposed control methods were analyzed theoretically and compared experimentally. The results show that IT2FSMC can reduce SMC steady state error by 54.43% while reducing the chattering of SMC. Simulation and experimental analysis verify the effectiveness of the proposed control method in ETS.
2023, 47(3): 301-304.
doi: 10.7510/jgjs.issn.1001-3806.2023.03.002
Abstract:
In order to obtain mode-locked pulses with different center wavelengths, a compact tunable mode-locked laser was built by using Sagnac loop filter with polarization maintaining fiber and semiconductor saturable absorber mirror. And the experimental verification was carried out. The results show that, the laser has a good wavelength tuning function when it operates in a single wavelength mode locked state, and its output wavelength is continuously adjustable in the range of 1031 nm to 1040 nm. The laser can also output a stable dual wavelength asynchronous pulse sequence, with the interval between the two wavelengths about 10 nm, and the bandwidth of each wavelength can be adjusted by the polarization controller. This research can provide a design scheme for building a compact tunable laser.
In order to obtain mode-locked pulses with different center wavelengths, a compact tunable mode-locked laser was built by using Sagnac loop filter with polarization maintaining fiber and semiconductor saturable absorber mirror. And the experimental verification was carried out. The results show that, the laser has a good wavelength tuning function when it operates in a single wavelength mode locked state, and its output wavelength is continuously adjustable in the range of 1031 nm to 1040 nm. The laser can also output a stable dual wavelength asynchronous pulse sequence, with the interval between the two wavelengths about 10 nm, and the bandwidth of each wavelength can be adjusted by the polarization controller. This research can provide a design scheme for building a compact tunable laser.
2023, 47(3): 305-309.
doi: 10.7510/jgjs.issn.1001-3806.2023.03.003
Abstract:
To investigate the intrinsic mechanism of femtosecond laser filament formation to achieve length characterization, fluorescence spectra and acoustic signal information of the plasma filament at different incident laser pulse energies and polarization states were obtained by fluorescence and acoustic methods. The results show that, the intensity of N2 fluorescence signal produced by circularly polarized light is about twice of that of linearly polarized light with the same laser pulse energy, while the intensity of N2+ fluorescence signal produced by linearly polarized light is about 1.3 times of that of circularly polarized light; Plasma fluorescence measurement is an effective way to obtain the length of plasma filament, which is more accurate than acoustic measurement. This study provides a feasible solution to characterize the filament length by revealing the physical essence of coherent laser emission with filament length.
To investigate the intrinsic mechanism of femtosecond laser filament formation to achieve length characterization, fluorescence spectra and acoustic signal information of the plasma filament at different incident laser pulse energies and polarization states were obtained by fluorescence and acoustic methods. The results show that, the intensity of N2 fluorescence signal produced by circularly polarized light is about twice of that of linearly polarized light with the same laser pulse energy, while the intensity of N2+ fluorescence signal produced by linearly polarized light is about 1.3 times of that of circularly polarized light; Plasma fluorescence measurement is an effective way to obtain the length of plasma filament, which is more accurate than acoustic measurement. This study provides a feasible solution to characterize the filament length by revealing the physical essence of coherent laser emission with filament length.
2023, 47(3): 310-316.
doi: 10.7510/jgjs.issn.1001-3806.2023.03.004
Abstract:
Light detection and ranging (LiDAR) is widely used in spacecraft navigation, security monitoring, 3-D mapping, autonomous vehicle, military equipment, robots, and other fields. It has important military and civil value. Avalanche photodiode (APD) array detection technology plays a vital role in the development of LiDAR. In this paper the background of LiDAR and APD array was first introduced, then the development history and latest progress of APD array and LiDAR system was summarized. Finally, the development prospect and research trend of APD array detection technology was summarized.
Light detection and ranging (LiDAR) is widely used in spacecraft navigation, security monitoring, 3-D mapping, autonomous vehicle, military equipment, robots, and other fields. It has important military and civil value. Avalanche photodiode (APD) array detection technology plays a vital role in the development of LiDAR. In this paper the background of LiDAR and APD array was first introduced, then the development history and latest progress of APD array and LiDAR system was summarized. Finally, the development prospect and research trend of APD array detection technology was summarized.
2023, 47(3): 317-321.
doi: 10.7510/jgjs.issn.1001-3806.2023.03.005
Abstract:
To find the connection between the number of near-full absorbing mode and the Fabry-Pérot (F-P) multilayer F-P cavity when single-layer graphene is located in the multilayer F-P cavity and to improve the system's controlling ability to the diversity of absorbing modes, rigorous coupled-wave analysis was adopted. The response characteristics of two-layer and three-layer F-P resonator under critical coupling conditions were analyzed. The results show that perfect absorbing modes of more than 99% and 96% can be respectively formed in two-layer and three-layer F-P cavity systems. Among them, the absorption characteristics of three-layer F-P nested cavity system can be adjusted by doping graphene, and the number and relative positions of absorption modes of three-layer nested cavity can be controlled by changing the structure of three-layer F-P cavity. The system introduces a richer absorbing line type.
To find the connection between the number of near-full absorbing mode and the Fabry-Pérot (F-P) multilayer F-P cavity when single-layer graphene is located in the multilayer F-P cavity and to improve the system's controlling ability to the diversity of absorbing modes, rigorous coupled-wave analysis was adopted. The response characteristics of two-layer and three-layer F-P resonator under critical coupling conditions were analyzed. The results show that perfect absorbing modes of more than 99% and 96% can be respectively formed in two-layer and three-layer F-P cavity systems. Among them, the absorption characteristics of three-layer F-P nested cavity system can be adjusted by doping graphene, and the number and relative positions of absorption modes of three-layer nested cavity can be controlled by changing the structure of three-layer F-P cavity. The system introduces a richer absorbing line type.
2023, 47(3): 322-328.
doi: 10.7510/jgjs.issn.1001-3806.2023.03.006
Abstract:
In order to solve the problems of artifacts and unreal details when process low-resolution blurred images using image enhancement methods, a low-resolution blurred image enhancement algorithm based on deep dense residual generative adversarial network (DDR GAN) was used to achieve effective enhancement of low-quality images. Firstly, an end-to-end generative adversarial network framework was constructed; further, a deep dense residual latent feature encoding architecture was designed to improve the deep semantic feature representation of the input image and enhance the image generation efficiency; finally, the loss function was reconstructed and the perceptual loss was added to guide the model to learn to generate realistic images. The comparative experimental results show that compared with the current state-of-the-art enhanced super-resolution GAN(ESR GAN) and DeBlur GAN-V2 algorithms, the images generated by DDR GAN are visually better, with higher definition and richer image detail. In terms of objective evaluation indicators, compared with ESR GAN and DeBlur GAN-V2, the peak signal-to-noise ratio was improved by 1.7072 dB and 1.1683 dB through DDR GAN, respectively, and the structural similarity by 0.0783 and 0.0713, respectively. This algorithm is helpful for the restoration and enhancement of low-resolution blurred images.
In order to solve the problems of artifacts and unreal details when process low-resolution blurred images using image enhancement methods, a low-resolution blurred image enhancement algorithm based on deep dense residual generative adversarial network (DDR GAN) was used to achieve effective enhancement of low-quality images. Firstly, an end-to-end generative adversarial network framework was constructed; further, a deep dense residual latent feature encoding architecture was designed to improve the deep semantic feature representation of the input image and enhance the image generation efficiency; finally, the loss function was reconstructed and the perceptual loss was added to guide the model to learn to generate realistic images. The comparative experimental results show that compared with the current state-of-the-art enhanced super-resolution GAN(ESR GAN) and DeBlur GAN-V2 algorithms, the images generated by DDR GAN are visually better, with higher definition and richer image detail. In terms of objective evaluation indicators, compared with ESR GAN and DeBlur GAN-V2, the peak signal-to-noise ratio was improved by 1.7072 dB and 1.1683 dB through DDR GAN, respectively, and the structural similarity by 0.0783 and 0.0713, respectively. This algorithm is helpful for the restoration and enhancement of low-resolution blurred images.
2023, 47(3): 329-334.
doi: 10.7510/jgjs.issn.1001-3806.2023.03.007
Abstract:
In order to study of the effect of fiber optic surface plasmon resonance (SPR) sensor parameters on refractive index measurement sensitivity, refractive index measurement experiments were carried out by using the dual-frequency laser heterodyne interferometric phase measurement optical path combined with the optical fiber SPR sensor. The effect of different core diameters on sensor sensitivity of fiber optic SPR sensors was theoretically analyzed. Within the refractive index range adapted by fiber optic SPR sensors, optical fibers with a core diameter of 300 μm and fibers with a core diameter of 400 μm were used to measure the phase difference of glycerol, sucrose and sodium chloride solutions under different mass fractions, and to calculate the corresponding refractive index. The relationship between the mass fraction and refractive index of each solution within the refractive index range adapted by the sensor was analyzed, and the theoretical results were experimentally verified. The results show that the smaller the diameter of the core, the higher the sensitivity of the sensor, and the sensitivity can reach 10-5 orders of magnitude; The higher the density, the higher the stability in the measurement, and the maximum phase difference standard deviation is 0.145°; The larger the molecular weight, the higher the accuracy, and the difference between the measured calculation of sucrose and the calibration value of the Abbe refractometer is up to 0.52×10-4. This research provides a good foundation for the further research and application of optical fiber SPR sensing technology.
In order to study of the effect of fiber optic surface plasmon resonance (SPR) sensor parameters on refractive index measurement sensitivity, refractive index measurement experiments were carried out by using the dual-frequency laser heterodyne interferometric phase measurement optical path combined with the optical fiber SPR sensor. The effect of different core diameters on sensor sensitivity of fiber optic SPR sensors was theoretically analyzed. Within the refractive index range adapted by fiber optic SPR sensors, optical fibers with a core diameter of 300 μm and fibers with a core diameter of 400 μm were used to measure the phase difference of glycerol, sucrose and sodium chloride solutions under different mass fractions, and to calculate the corresponding refractive index. The relationship between the mass fraction and refractive index of each solution within the refractive index range adapted by the sensor was analyzed, and the theoretical results were experimentally verified. The results show that the smaller the diameter of the core, the higher the sensitivity of the sensor, and the sensitivity can reach 10-5 orders of magnitude; The higher the density, the higher the stability in the measurement, and the maximum phase difference standard deviation is 0.145°; The larger the molecular weight, the higher the accuracy, and the difference between the measured calculation of sucrose and the calibration value of the Abbe refractometer is up to 0.52×10-4. This research provides a good foundation for the further research and application of optical fiber SPR sensing technology.
2023, 47(3): 335-339.
doi: 10.7510/jgjs.issn.1001-3806.2023.03.008
Abstract:
In order to trapping multiparticle chain of different materials and different sizes, a double-tapered optical fiber tweezer (DOFT) was prepared by the interfacial layer etching method. A single-fiber optical tweezers system was built to trapping multiparticle chain of yeast, silica, polystyrene, and other materials. The experimental results show that for the particles of the same material, the number of particles trapped by the DOFT decreases with the increase of their size; as for the particles of the same size, the number of particles trapped by the DOFT decreases with the increase of their refractive index. By measuring the trapping force of the multiparticle chain, it is found that the farther from the probe, the smaller the trapping force. Therefore, the particles at the end of a probe will escape first under the external force. In addition, the results of theoretical calculations show that DOFT with second taper angle greater than 60° cannot trap two or more spherical particles, which is consistent with experimental observations. This study can be applied to precision machining and micro-nano fabrication.
In order to trapping multiparticle chain of different materials and different sizes, a double-tapered optical fiber tweezer (DOFT) was prepared by the interfacial layer etching method. A single-fiber optical tweezers system was built to trapping multiparticle chain of yeast, silica, polystyrene, and other materials. The experimental results show that for the particles of the same material, the number of particles trapped by the DOFT decreases with the increase of their size; as for the particles of the same size, the number of particles trapped by the DOFT decreases with the increase of their refractive index. By measuring the trapping force of the multiparticle chain, it is found that the farther from the probe, the smaller the trapping force. Therefore, the particles at the end of a probe will escape first under the external force. In addition, the results of theoretical calculations show that DOFT with second taper angle greater than 60° cannot trap two or more spherical particles, which is consistent with experimental observations. This study can be applied to precision machining and micro-nano fabrication.
2023, 47(3): 340-344.
doi: 10.7510/jgjs.issn.1001-3806.2023.03.009
Abstract:
In order to optimize the measurement of the responsibility and angle parameters of the large-aperture laser detector, and to reduce the discrepancy generated from the central-peak weak-edge profile of gaussian beam, a large-aperture flat-top laser beam generator was designed based on aspheric lens shaping and high-magnification collimating systems. A comprehensive shaping technology based on intensity distribution, aspheric coefficients, and optical path difference was presented. The results show that the aspheric coefficient of a Kepler aspheric lenis less than 20 μm, effective width is 5 mm, and the energy uniformity of the flat-top output beam is greater than 92.8%. And a 40× high quality collimating system was designed to match the aspheric lens to realize a flat-top beam of 150 mm aperture in 2 m distance. The measurement results show that the energy uniformity of the 150 mm flat-top beam is greater than 94.2%. This research is helpful to the engineering design of laser measurement and calibration system.
In order to optimize the measurement of the responsibility and angle parameters of the large-aperture laser detector, and to reduce the discrepancy generated from the central-peak weak-edge profile of gaussian beam, a large-aperture flat-top laser beam generator was designed based on aspheric lens shaping and high-magnification collimating systems. A comprehensive shaping technology based on intensity distribution, aspheric coefficients, and optical path difference was presented. The results show that the aspheric coefficient of a Kepler aspheric lenis less than 20 μm, effective width is 5 mm, and the energy uniformity of the flat-top output beam is greater than 92.8%. And a 40× high quality collimating system was designed to match the aspheric lens to realize a flat-top beam of 150 mm aperture in 2 m distance. The measurement results show that the energy uniformity of the 150 mm flat-top beam is greater than 94.2%. This research is helpful to the engineering design of laser measurement and calibration system.
2023, 47(3): 345-352.
doi: 10.7510/jgjs.issn.1001-3806.2023.03.010
Abstract:
Femtosecond laser ablation processing has small thermal zone, high laser resolution, and can weaken the physical plasma shielding effect when compared with traditional picosecond or nanosecond laser ablation. So, it is widely used in many areas. The mechanism of femtosecond laser ablation of transparent dielectric materials was expounded based on avalanche ionization and multiphoton ionization effects. In addition, the current status of femtosecond laser ablation of different microstructures was introduced. Particularly, the research methods and progress of ablation points, ablation lines and ablation surfaces of femtosecond laser micro-nano processing were reviewed at home and abroad in recent years. Also, the practical application of micro-functional structural components was summarized. Moreover, the current shortcomings of femtosecond lasers in the field of processing transparent dielectrics are analyzed, and the development of this technology is prospected.
Femtosecond laser ablation processing has small thermal zone, high laser resolution, and can weaken the physical plasma shielding effect when compared with traditional picosecond or nanosecond laser ablation. So, it is widely used in many areas. The mechanism of femtosecond laser ablation of transparent dielectric materials was expounded based on avalanche ionization and multiphoton ionization effects. In addition, the current status of femtosecond laser ablation of different microstructures was introduced. Particularly, the research methods and progress of ablation points, ablation lines and ablation surfaces of femtosecond laser micro-nano processing were reviewed at home and abroad in recent years. Also, the practical application of micro-functional structural components was summarized. Moreover, the current shortcomings of femtosecond lasers in the field of processing transparent dielectrics are analyzed, and the development of this technology is prospected.
2023, 47(3): 353-359.
doi: 10.7510/jgjs.issn.1001-3806.2023.03.011
Abstract:
In order to deeply understand the development status of laser remanufacture of titanium alloys, the research progress of laser remanufacturing of titanium alloy was reviewed from the aspects of remanufacturing materials, processes, and methods. The remanufacturing characteristics and applications of metal alloy powder, ceramic powder, rare earth and its oxide powder coatings were described. The effects of main process parameters on the morphology and properties of coatings were discussed. The applications of numerical simulation, auxiliary process and composite process in laser remanufacturing of titanium alloy parts were discussed. Finally, the development trend of laser remanufacturing of titanium alloy parts was prospected.
In order to deeply understand the development status of laser remanufacture of titanium alloys, the research progress of laser remanufacturing of titanium alloy was reviewed from the aspects of remanufacturing materials, processes, and methods. The remanufacturing characteristics and applications of metal alloy powder, ceramic powder, rare earth and its oxide powder coatings were described. The effects of main process parameters on the morphology and properties of coatings were discussed. The applications of numerical simulation, auxiliary process and composite process in laser remanufacturing of titanium alloy parts were discussed. Finally, the development trend of laser remanufacturing of titanium alloy parts was prospected.
2023, 47(3): 360-365.
doi: 10.7510/jgjs.issn.1001-3806.2023.03.012
Abstract:
In order to improve specific application imaging quality of infrared seeker, a model for imaging condition and application scene was constructed by using statistical image of infrared image seeker. On the one hand, L1/L2 norm was used to constrain the restored image according to the characteristics of multi-scale imaging, which kept details in the iterative restoration. On the other hand, a sparse Laplacian distribution was used to constrain fuzzy kernel, and to maintain image's content. Image kernel size can be adjusted adaptively by calculating the image details. The result shows that the prior constrain algorithm of this paper can effectively improve the image quality. In addition, the evaluation index is improved by this prior design, the contrast enhancement coefficient index is increased by 20%~50%, the peak signal to noise ratio is increased by 0.8~3.4, and the cumulative probability of blur detection is increased by 0.3~0.5.This study is helpful for complex scene and moving vector imaging.
In order to improve specific application imaging quality of infrared seeker, a model for imaging condition and application scene was constructed by using statistical image of infrared image seeker. On the one hand, L1/L2 norm was used to constrain the restored image according to the characteristics of multi-scale imaging, which kept details in the iterative restoration. On the other hand, a sparse Laplacian distribution was used to constrain fuzzy kernel, and to maintain image's content. Image kernel size can be adjusted adaptively by calculating the image details. The result shows that the prior constrain algorithm of this paper can effectively improve the image quality. In addition, the evaluation index is improved by this prior design, the contrast enhancement coefficient index is increased by 20%~50%, the peak signal to noise ratio is increased by 0.8~3.4, and the cumulative probability of blur detection is increased by 0.3~0.5.This study is helpful for complex scene and moving vector imaging.
2023, 47(3): 366-371.
doi: 10.7510/jgjs.issn.1001-3806.2033.03.013
Abstract:
In order to analyze space-domain passive fiber cavity ring-down acetylene gas volume fraction detection system more accurately, a theoretical model of gas volume fraction sensing system considering system noise was established in this paper. The performance of space-domain passive fiber cavity ring-down acetylene gas volume fraction detection system was simulated and discussed by using this model. Simulation results show that, by using the space-domain passive fiber cavity ring-down sensing technology, the acetylene volume fraction can be monitored by measuring the ring-down distance and the sensitivity of 56.226 km-1 is achieved, the corresponding stability and detection limit can reach 0.47% and 260.577×10-6, which can be further improved by reducing the inherent cavity loss of the fiber cavity. This research has theoretical significance for the optimization design of volume fraction sensing system.
In order to analyze space-domain passive fiber cavity ring-down acetylene gas volume fraction detection system more accurately, a theoretical model of gas volume fraction sensing system considering system noise was established in this paper. The performance of space-domain passive fiber cavity ring-down acetylene gas volume fraction detection system was simulated and discussed by using this model. Simulation results show that, by using the space-domain passive fiber cavity ring-down sensing technology, the acetylene volume fraction can be monitored by measuring the ring-down distance and the sensitivity of 56.226 km-1 is achieved, the corresponding stability and detection limit can reach 0.47% and 260.577×10-6, which can be further improved by reducing the inherent cavity loss of the fiber cavity. This research has theoretical significance for the optimization design of volume fraction sensing system.
2023, 47(3): 372-379.
doi: 10.7510/jgjs.issn.1001-3806.2023.03.014
Abstract:
In order to investigate the influence of the nonlinear process of four-wave mixing on the spectral broadening characteristics of high-power ytterbium-doped fiber laser, ytterbium-doped fiber with core and inner cladding diameters of 20 μm and 400 μm, resperctively, was used as the gain medium. Based on the nonlinear process of four wave mixing, an ytterbium-doped fiber laser spectral analysis model was established. The effects of pump power, pump wavelength, center wavelength, and injection mode number on the spectral broadening characteristics of an ytterbium-doped fiber laser were analyzed. The output power spectrum of 1080 nm laser and the curve of output laser linewidth with the above parameters were obtained. The simulation results show that in the nonlinear process of four-wave mixing, the increase of pump power leads to the broadening of the output spectral linewidth of the ytterbium-doped fiber laser; the output spectral linewidth broadening rate of different pump wavelengths is different; the broadening degree of the output laser spectrum of the long band central wavelength is similar; the spectral linewidth of ytterbium-doped fiber laser gradually broadens with the increase of the number of injection modes. The simulation results provide theoretical support for the study of ytterbium-doped fiber laser spectral broadening characteristics, and have certain reference significance for the engineering application of high-power fiber laser.
In order to investigate the influence of the nonlinear process of four-wave mixing on the spectral broadening characteristics of high-power ytterbium-doped fiber laser, ytterbium-doped fiber with core and inner cladding diameters of 20 μm and 400 μm, resperctively, was used as the gain medium. Based on the nonlinear process of four wave mixing, an ytterbium-doped fiber laser spectral analysis model was established. The effects of pump power, pump wavelength, center wavelength, and injection mode number on the spectral broadening characteristics of an ytterbium-doped fiber laser were analyzed. The output power spectrum of 1080 nm laser and the curve of output laser linewidth with the above parameters were obtained. The simulation results show that in the nonlinear process of four-wave mixing, the increase of pump power leads to the broadening of the output spectral linewidth of the ytterbium-doped fiber laser; the output spectral linewidth broadening rate of different pump wavelengths is different; the broadening degree of the output laser spectrum of the long band central wavelength is similar; the spectral linewidth of ytterbium-doped fiber laser gradually broadens with the increase of the number of injection modes. The simulation results provide theoretical support for the study of ytterbium-doped fiber laser spectral broadening characteristics, and have certain reference significance for the engineering application of high-power fiber laser.
2023, 47(3): 380-385.
doi: 10.7510/jgjs.issn.1001-3806.2023.03.015
Abstract:
In order to study the influence of hybrid heat sources on welding characteristics of T4003 ferrite stainless steel, the effect of parameters on the morphology and microstructure of laser-arc hybrid weld joints was investigated, and the range of the parameters were optimized. In addition, the impact toughness and enhancing mechanism of weld metal and heat affected zone at -40 ℃ were analyzed emphatically. The results show that the comprehensive mechanical properties of the joint under the optimization parameter are excellent: The tensile fracture occurred in the base material and the tensile strength is 530 MPa, and no crack is found in the 180° transverse bending tests. The average impact absorbed energy of weld metal(50 J) is slightly higher than that of conventional arc welding, and the average impact absorbed energy of heat affected zone is about three times of arc welding(32 J). The reason is that the low heat input of laser-arc hybrid welding refines the coarse grain in heat affected zone. Besides, the impact fracture morphology shows that the final fracture zone of weld metal mainly consists of dimples with no ductile-brittle transition, while the heat affected zone exhibited obvious ductile-brittle transition with quasi-cleavage morphology in the central expansion zone. This study can promote the application of laser-arc hybrid welding in ferritic stainless steel.
In order to study the influence of hybrid heat sources on welding characteristics of T4003 ferrite stainless steel, the effect of parameters on the morphology and microstructure of laser-arc hybrid weld joints was investigated, and the range of the parameters were optimized. In addition, the impact toughness and enhancing mechanism of weld metal and heat affected zone at -40 ℃ were analyzed emphatically. The results show that the comprehensive mechanical properties of the joint under the optimization parameter are excellent: The tensile fracture occurred in the base material and the tensile strength is 530 MPa, and no crack is found in the 180° transverse bending tests. The average impact absorbed energy of weld metal(50 J) is slightly higher than that of conventional arc welding, and the average impact absorbed energy of heat affected zone is about three times of arc welding(32 J). The reason is that the low heat input of laser-arc hybrid welding refines the coarse grain in heat affected zone. Besides, the impact fracture morphology shows that the final fracture zone of weld metal mainly consists of dimples with no ductile-brittle transition, while the heat affected zone exhibited obvious ductile-brittle transition with quasi-cleavage morphology in the central expansion zone. This study can promote the application of laser-arc hybrid welding in ferritic stainless steel.
2023, 47(3): 386-392.
doi: 10.7510/jgjs.issn.1001-3806.2023.03.016
Abstract:
As a typical style of joint operations, close air support has played an important role in supporting ground operations in many recent local wars, and the research on its application has always been updated and improved. In this paper, the application of laser equipment in short-range combat was summarized, and a reference for the domestic development and application of similar equipment was proposed.
As a typical style of joint operations, close air support has played an important role in supporting ground operations in many recent local wars, and the research on its application has always been updated and improved. In this paper, the application of laser equipment in short-range combat was summarized, and a reference for the domestic development and application of similar equipment was proposed.
2023, 47(3): 393-399.
doi: 10.7510/jgjs.issn.1001-3806.2023.03.017
Abstract:
In order to improve the hardness and wear resistance of oil drilling pipe material 42CrMo, Fe06+TiC/Mo composite coatings with different mass fractions (0, 0.10, 0.15, 0.20) were prepared by laser cladding technique. The microhardness, wear resistance, phase composition, wear behavior, and experimental verification were carried out by microhardness instrument, scanning electron microscope, and friction and wear testing machine. It was found that the cladding layer was mainly composed of α-Fe, Cr-Fe and (Fe, Ni) solid solution phases. The results show that the average microhardness of Fe06+TiC composite coating about 1180 HV0.2, and that of Fe06+Mo composite coating is about 893 HV0.2. The average mass loss of Fe06+TiC composite coating is about 2.97 mg, the average mass loss of Fe06 cladding layer is 7.8 mg, and the average mass loss of Fe06+Mo composite coating is about 2.67 mg, respectively. The wear mechanism of Fe06+TiC/Mo composite coating is mainly adhesion wear and abrasive wear. The hardness of Fe06+0.20TiC cladding is the highest, and the wear resistance of Fe06+0.20Mo cladding is the best. This study provides practical reference for improving the hardness and wear resistance of 42CrMo materials.
In order to improve the hardness and wear resistance of oil drilling pipe material 42CrMo, Fe06+TiC/Mo composite coatings with different mass fractions (0, 0.10, 0.15, 0.20) were prepared by laser cladding technique. The microhardness, wear resistance, phase composition, wear behavior, and experimental verification were carried out by microhardness instrument, scanning electron microscope, and friction and wear testing machine. It was found that the cladding layer was mainly composed of α-Fe, Cr-Fe and (Fe, Ni) solid solution phases. The results show that the average microhardness of Fe06+TiC composite coating about 1180 HV0.2, and that of Fe06+Mo composite coating is about 893 HV0.2. The average mass loss of Fe06+TiC composite coating is about 2.97 mg, the average mass loss of Fe06 cladding layer is 7.8 mg, and the average mass loss of Fe06+Mo composite coating is about 2.67 mg, respectively. The wear mechanism of Fe06+TiC/Mo composite coating is mainly adhesion wear and abrasive wear. The hardness of Fe06+0.20TiC cladding is the highest, and the wear resistance of Fe06+0.20Mo cladding is the best. This study provides practical reference for improving the hardness and wear resistance of 42CrMo materials.
2023, 47(3): 400-406.
doi: 10.7510/jgjs.issn.1001-3806.2023.03.018
Abstract:
In order to solve the problems of low efficiency, high false detection rate, low versatility, poor real-time performance of the current fruit identification and detection methods, a fruit recognition detection method based on improved you only look once (YOLO) YOLOv4 algorithm was proposed in this study. Firstly, an efficient channel attention was added to the backbone network to enhance the network's ability to extract semantic information from images. Secondly, the convolutional layers at the cross stage partial block junction in the backbone network were replaced by involutions, which reduced the model size and enhanced the network prediction performance. Finally, residual modules were added to the feature fusion network path aggregation network to speed up network convergence and prevent network gradient explosion. The datasets selected 10 kinds of fruits common in life: dragon fruits, oranges, grapes, green mangoes and so on with a total of 6670 pictures. The experiments show that the mean average precision (MAP) of the proposed method is 99.10%, the precision is 95.62%, and the number of frames transmitted is 41.67/s, respectively. MAP is improved by 15.3% compared with YOLOv4. This study meets the requirements of high detection accuracy and detection speed and has important reference value for improving the accuracy of fruit identification.
In order to solve the problems of low efficiency, high false detection rate, low versatility, poor real-time performance of the current fruit identification and detection methods, a fruit recognition detection method based on improved you only look once (YOLO) YOLOv4 algorithm was proposed in this study. Firstly, an efficient channel attention was added to the backbone network to enhance the network's ability to extract semantic information from images. Secondly, the convolutional layers at the cross stage partial block junction in the backbone network were replaced by involutions, which reduced the model size and enhanced the network prediction performance. Finally, residual modules were added to the feature fusion network path aggregation network to speed up network convergence and prevent network gradient explosion. The datasets selected 10 kinds of fruits common in life: dragon fruits, oranges, grapes, green mangoes and so on with a total of 6670 pictures. The experiments show that the mean average precision (MAP) of the proposed method is 99.10%, the precision is 95.62%, and the number of frames transmitted is 41.67/s, respectively. MAP is improved by 15.3% compared with YOLOv4. This study meets the requirements of high detection accuracy and detection speed and has important reference value for improving the accuracy of fruit identification.
2023, 47(3): 407-412.
doi: 10.7510/jgjs.issn.1001-3806.2023.03.019
Abstract:
In order to improve the efficiency of parameter fitting of binary reflectance distribution function (BRDF)model and understand the spectral direction characteristics of ground object more specifically, a method of parameter fitting of BRDF model based on generalized inverse matrix was proposed. Firstly, the directional characteristics of spectral reflection of ground objects were analyzed, and then the spectral reflectance of targets in different directions was measured by imaging spectrometer. The experimental conditions and a priori measurement data were substituted into BRDF model, the generalized inverse matrix equation was established, and the model parameters of measurement targets were fitted. Using the BRDF model parameters of fitting the push any particular direction under the condition of spectral reflectance and compared with experimental data. Spectral angle mapping method was used to measure its similarity and the results showed that the grass and camouflage raincoat fitting spectrum curve and the measured spectral curve similarity is very high, up to the 0.1307 and 0.0896, confirmed the validity of the parameter fitting method, the ability to verify the generalization of the BRDF model fitting. This method is simple in principle, fast and effective, and provides reference for other types of BRDF model parameter fitting and subsequent research on spectral characteristics of ground objects.
In order to improve the efficiency of parameter fitting of binary reflectance distribution function (BRDF)model and understand the spectral direction characteristics of ground object more specifically, a method of parameter fitting of BRDF model based on generalized inverse matrix was proposed. Firstly, the directional characteristics of spectral reflection of ground objects were analyzed, and then the spectral reflectance of targets in different directions was measured by imaging spectrometer. The experimental conditions and a priori measurement data were substituted into BRDF model, the generalized inverse matrix equation was established, and the model parameters of measurement targets were fitted. Using the BRDF model parameters of fitting the push any particular direction under the condition of spectral reflectance and compared with experimental data. Spectral angle mapping method was used to measure its similarity and the results showed that the grass and camouflage raincoat fitting spectrum curve and the measured spectral curve similarity is very high, up to the 0.1307 and 0.0896, confirmed the validity of the parameter fitting method, the ability to verify the generalization of the BRDF model fitting. This method is simple in principle, fast and effective, and provides reference for other types of BRDF model parameter fitting and subsequent research on spectral characteristics of ground objects.
2023, 47(3): 413-418.
doi: 10.7510/jgjs.issn.1001-3806.2023.03.020
Abstract:
In order to improve the output laser polarization stability of high-energy polarization fiber lasers, the signal light source and (6+1)×1 reverse polarization-maintaining optical fiber coupler were combined by introducing the basic principle of reverse extinction ratio of reverse polarization-maintaining optical fiber coupler. The influence of signal polarization-maintaining optical fiber diameter and physical change of the stress area of the reverse polarization-maintaining optical fiber on the reverse extinction ratio of a reverse polarization-maintaining optical fiber coupler was studied. The results show that the smaller the diameter of the signal polarization-maintaining fiber, the more stable the polarization state of the output polarized laser, and the reverse extinction ratio is greater than 49 dB. At the same time, the coupling efficiency of the pumping fiber arm of the reverse polarization-maintaining fiber coupler is improved to more than 98%. The more serious the change of the physical structure of the stress region of the forward polarization laser output fiber, the less stable the polarization state of the output polarization laser. The research provides reference for the preparation of high extinction ratio high-energy polarization fiber lasers.
In order to improve the output laser polarization stability of high-energy polarization fiber lasers, the signal light source and (6+1)×1 reverse polarization-maintaining optical fiber coupler were combined by introducing the basic principle of reverse extinction ratio of reverse polarization-maintaining optical fiber coupler. The influence of signal polarization-maintaining optical fiber diameter and physical change of the stress area of the reverse polarization-maintaining optical fiber on the reverse extinction ratio of a reverse polarization-maintaining optical fiber coupler was studied. The results show that the smaller the diameter of the signal polarization-maintaining fiber, the more stable the polarization state of the output polarized laser, and the reverse extinction ratio is greater than 49 dB. At the same time, the coupling efficiency of the pumping fiber arm of the reverse polarization-maintaining fiber coupler is improved to more than 98%. The more serious the change of the physical structure of the stress region of the forward polarization laser output fiber, the less stable the polarization state of the output polarization laser. The research provides reference for the preparation of high extinction ratio high-energy polarization fiber lasers.
2023, 47(3): 419-424.
doi: 10.7510/jgjs.issn.1001-3806.2023.03.021
Abstract:
According to the phenomena of interface cracking and falling off of protective coatings caused by different thermophysical parameters between protective coatings and aluminum alloy in the process of laser engraving, a two-dimensional finite element model of multi layer materials was established based on the thermal stress coupling analysis method. The pulsed laser was loaded on the surface of protective coatings in the form of Gaussian distributed heat flux. The stress distribution nephogram of aluminum alloy matrix and the evolution law of kerf morphology of protective coatings under the action of thermal stress with different laser processing parameters were obtained by calculation. The effects of laser power, scanning speed, and repetition frequency on temperature field, stress field, engraving morphology, and stress displacement were compared and analyzed, respectively. The results show that when the parameters are selected as power 60 W, scanning speed 10 m/min and repetition frequency 100 kHz, the influence on temperature field, stress field, etching morphology, and stress displacement is minimal. The research of this paper has great reference significance for the practical application of laser engraving in chemical milling, and provides a direction for the process optimization of laser engraving.
According to the phenomena of interface cracking and falling off of protective coatings caused by different thermophysical parameters between protective coatings and aluminum alloy in the process of laser engraving, a two-dimensional finite element model of multi layer materials was established based on the thermal stress coupling analysis method. The pulsed laser was loaded on the surface of protective coatings in the form of Gaussian distributed heat flux. The stress distribution nephogram of aluminum alloy matrix and the evolution law of kerf morphology of protective coatings under the action of thermal stress with different laser processing parameters were obtained by calculation. The effects of laser power, scanning speed, and repetition frequency on temperature field, stress field, engraving morphology, and stress displacement were compared and analyzed, respectively. The results show that when the parameters are selected as power 60 W, scanning speed 10 m/min and repetition frequency 100 kHz, the influence on temperature field, stress field, etching morphology, and stress displacement is minimal. The research of this paper has great reference significance for the practical application of laser engraving in chemical milling, and provides a direction for the process optimization of laser engraving.
2023, 47(3): 425-431.
doi: 10.7510/jgjs.issn.1001-3806.2023.03.022
Abstract:
2-D scanning system with double mirrors of a traditional wind light detection and ranging(LiDAR) was large in volume and complex in structure, which was not conducive to the small-scale integration of the system. A new 2-D optical scanning system based on rotating double circular wedge prism was studied. The working principle of the system was analyzed, and the simple forward and inverse functional relationship between the rotation angle of the double circular wedge prism and the azimuth and zenith angle of the outgoing beam was derived. The refractive index and wedge angle of the wedge prism were optimized and designed. The results show that when the working wavelength is 532 nm and the refractive index of wedge prism material is 2.03, the optimal wedge angle is 19.5°. The maximum zenith angle of the outgoing beam depends not only on the refractive index and wedge angle of the wedge prism, but also on the beam compression effect. The system is compact and easy to integrate, and large-scale, fast and high-precision scanning of the outgoing beam can be realized. The wind LiDAR can also work in beam scanning modes such as plane position display and distance height display.
2-D scanning system with double mirrors of a traditional wind light detection and ranging(LiDAR) was large in volume and complex in structure, which was not conducive to the small-scale integration of the system. A new 2-D optical scanning system based on rotating double circular wedge prism was studied. The working principle of the system was analyzed, and the simple forward and inverse functional relationship between the rotation angle of the double circular wedge prism and the azimuth and zenith angle of the outgoing beam was derived. The refractive index and wedge angle of the wedge prism were optimized and designed. The results show that when the working wavelength is 532 nm and the refractive index of wedge prism material is 2.03, the optimal wedge angle is 19.5°. The maximum zenith angle of the outgoing beam depends not only on the refractive index and wedge angle of the wedge prism, but also on the beam compression effect. The system is compact and easy to integrate, and large-scale, fast and high-precision scanning of the outgoing beam can be realized. The wind LiDAR can also work in beam scanning modes such as plane position display and distance height display.
2023, 47(3): 432-438.
doi: 10.7510/jgjs.issn.1001-3806.2023.03.023
Abstract:
In order to research the characteristics of momentum downward gale and discussion on forecast method of momentum downward gale, the momentum downward gale process at Yinchuan Airport on 2022-03-06 was analyzed by using the reanalysis data of National Centers for Environmental Prediction (NCEP), conventional meteorological observation data, and wind light detection and ranging (LiDAR) data. The results show that Yinchuan Airport is located in the convergence area on the left side of the westerly jet inlet, which provides a favorable circulation background for the occurrence of momentum downward gale; Under clear sky conditions, the temporal and spatial evolution characteristics of momentum downwind can be accurately detected by the wind LiDAR product; the strong downdraft in the Doppler beam swinging(DBS) mode product marks the beginning of momentum downward transmission, the attenuation degree and change direction of the detection range of the plan position indicator(PPI) mode reflect the sand dust weather intensity and influence path, the occurrence and destruction of radial wind stratification at 500 m height in the range height indicator(RHI) model are the prediction indicators of momentum downward transmission changes; Using the wind LiDAR, the time of occurrence of downwind strong wind can be calculated and predicted 30 min in advance. This research is of great significance to improve the meteorological service support capability.
In order to research the characteristics of momentum downward gale and discussion on forecast method of momentum downward gale, the momentum downward gale process at Yinchuan Airport on 2022-03-06 was analyzed by using the reanalysis data of National Centers for Environmental Prediction (NCEP), conventional meteorological observation data, and wind light detection and ranging (LiDAR) data. The results show that Yinchuan Airport is located in the convergence area on the left side of the westerly jet inlet, which provides a favorable circulation background for the occurrence of momentum downward gale; Under clear sky conditions, the temporal and spatial evolution characteristics of momentum downwind can be accurately detected by the wind LiDAR product; the strong downdraft in the Doppler beam swinging(DBS) mode product marks the beginning of momentum downward transmission, the attenuation degree and change direction of the detection range of the plan position indicator(PPI) mode reflect the sand dust weather intensity and influence path, the occurrence and destruction of radial wind stratification at 500 m height in the range height indicator(RHI) model are the prediction indicators of momentum downward transmission changes; Using the wind LiDAR, the time of occurrence of downwind strong wind can be calculated and predicted 30 min in advance. This research is of great significance to improve the meteorological service support capability.
