Map
WeChat
Email alert
RSS2016 Vol. 40, No. 1
Display Method:
2016, 40(1): 1-4.
doi: 10.7510/jgjs.issn.1001-3806.2016.01.001
[Abstract]
[PDF 1361KB]
Abstract:
In order to obtain symmetrical high birefringence photonic crystal fiber filled with Au. The fundamental mode of the fiber core, dispersion and loss characteristics of plasma polaritons of metal surface were analyzed by means of finite element method. The resonance positions and the resonance strength between fundamental mode and plasma polaritons could be well adjusted by changing the distances between the cladding air holes, the diameters of air holes around the core and the diameter of metal wire. By optimizing the parameters of fiber structure, a polarization filter at the communication band was designed. After numerical aperture of air hole was determined, fundamental mode loss in x-position could reach 473dB/cm and fundamental mode loss of y-position was almost not affected by surface plasma polariton (SPP) mode at the wavelength of 1.55m. The results show that compared with ordinary single-polarization and single-mode photonic crystal fibers, the polarized light in one direction can be filtered out selectively by adjusting the wire diameter and achieve filtering effect in the communication band. It is meaningful for the development of polarization filters in the communication band.
In order to obtain symmetrical high birefringence photonic crystal fiber filled with Au. The fundamental mode of the fiber core, dispersion and loss characteristics of plasma polaritons of metal surface were analyzed by means of finite element method. The resonance positions and the resonance strength between fundamental mode and plasma polaritons could be well adjusted by changing the distances between the cladding air holes, the diameters of air holes around the core and the diameter of metal wire. By optimizing the parameters of fiber structure, a polarization filter at the communication band was designed. After numerical aperture of air hole was determined, fundamental mode loss in x-position could reach 473dB/cm and fundamental mode loss of y-position was almost not affected by surface plasma polariton (SPP) mode at the wavelength of 1.55m. The results show that compared with ordinary single-polarization and single-mode photonic crystal fibers, the polarized light in one direction can be filtered out selectively by adjusting the wire diameter and achieve filtering effect in the communication band. It is meaningful for the development of polarization filters in the communication band.
2016, 40(1): 5-10.
doi: 10.7510/jgjs.issn.1001-3806.2016.01.002
Abstract:
To obtain maximum surface residual compressive stress by optimizing technological parameters of laser shock, the formula of residual compressive stress on the surface of AZ31 magnesium after laser shock process (LSP) was deduced from the theory of laser shock process and plastic deformation. Residual stress fields of AZ31 magnesium by LSP was simulated with ABAQUS software. Finite element analysis shows that laser shock wave pressure of optimal residual compressive stress field ranges from 1.2GPa to 1.7GPa. With the increase of load, residual stress on the surface of AZ31 magnesium increases. The maximum residual compressive stress is about 125MPa with loading range from 1.4GPa to 1.6GPa. There is a slight residual stresses hole phenomenon impact when load is 1.8GPa and a significant residual stresses hole phenomenon when load is more than 1.9GPa. When the load is 1.474GPa, the maximum residual stress is -128.5MPa. Experimental results are consistent with finite element analysis.
To obtain maximum surface residual compressive stress by optimizing technological parameters of laser shock, the formula of residual compressive stress on the surface of AZ31 magnesium after laser shock process (LSP) was deduced from the theory of laser shock process and plastic deformation. Residual stress fields of AZ31 magnesium by LSP was simulated with ABAQUS software. Finite element analysis shows that laser shock wave pressure of optimal residual compressive stress field ranges from 1.2GPa to 1.7GPa. With the increase of load, residual stress on the surface of AZ31 magnesium increases. The maximum residual compressive stress is about 125MPa with loading range from 1.4GPa to 1.6GPa. There is a slight residual stresses hole phenomenon impact when load is 1.8GPa and a significant residual stresses hole phenomenon when load is more than 1.9GPa. When the load is 1.474GPa, the maximum residual stress is -128.5MPa. Experimental results are consistent with finite element analysis.
2016, 40(1): 11-14.
doi: 10.7510/jgjs.issn.1001-3806.2016.01.003
Abstract:
In order to achieve all-optical diode function, a 1-D photonic crystal nonlinear microcavity was designed with metal films in different thickness coated on both sides of the photonic crystal. Transmission properties of the microcavity were studied with the nonlinear transfer matrix method. The results show that structure coupling both the nonsymmetric optical Tamm states and nonlinear microcavity shows bistable states with all-optical diode feature, and that the position of hysteresis loop is related with incident direction. The diode performance is dependent on the thickness of nonlinear microcavity and the ratio of thickness of the metal films on both sides. The design provides a reference for the optimization design of all-optical diodes.
In order to achieve all-optical diode function, a 1-D photonic crystal nonlinear microcavity was designed with metal films in different thickness coated on both sides of the photonic crystal. Transmission properties of the microcavity were studied with the nonlinear transfer matrix method. The results show that structure coupling both the nonsymmetric optical Tamm states and nonlinear microcavity shows bistable states with all-optical diode feature, and that the position of hysteresis loop is related with incident direction. The diode performance is dependent on the thickness of nonlinear microcavity and the ratio of thickness of the metal films on both sides. The design provides a reference for the optimization design of all-optical diodes.
2016, 40(1): 15-19.
doi: 10.7510/jgjs.issn.1001-3806.2016.01.004
Abstract:
In order to solve the problems such as the control of welding penetration, the loss of alloy element and weld surface quality in the process of partial penetration welding of 5A06 aluminum alloy with high power fiber laser, the effects of welding speed, defocusing amount, and lap plate gap on the quality of weld surface were studied by changing one of the welding parameters at fixed laser power and positive welding protective gas. The distribution rule of magnesium element was analyzed theoretically and verified experimentally. The test results show that weld hardness is consistent with the distribution of magnesium element. Due to the common effect of grain refinement and magnesium element diffusion of parent metal, the hardness near fusion line is greater than the other parts. The strength of laser partial penetration welding joint with optimized parameters is greater than the strength of arc riveting joint. When the clearance is 0.2mm, the strength of laser welding joint is highest and can reach 68.1% of the tensile strength of the parent material. The results are helpful to guide the partial penetration laser welding of aluminum alloy.
In order to solve the problems such as the control of welding penetration, the loss of alloy element and weld surface quality in the process of partial penetration welding of 5A06 aluminum alloy with high power fiber laser, the effects of welding speed, defocusing amount, and lap plate gap on the quality of weld surface were studied by changing one of the welding parameters at fixed laser power and positive welding protective gas. The distribution rule of magnesium element was analyzed theoretically and verified experimentally. The test results show that weld hardness is consistent with the distribution of magnesium element. Due to the common effect of grain refinement and magnesium element diffusion of parent metal, the hardness near fusion line is greater than the other parts. The strength of laser partial penetration welding joint with optimized parameters is greater than the strength of arc riveting joint. When the clearance is 0.2mm, the strength of laser welding joint is highest and can reach 68.1% of the tensile strength of the parent material. The results are helpful to guide the partial penetration laser welding of aluminum alloy.
2016, 40(1): 20-24.
doi: 10.7510/jgjs.issn.1001-3806.2016.01.005
Abstract:
To measure microsurface profile of an object, a spatial two-step phase-shifting interferometer was proposed based on an improved Michelson architecture. Based on a Tyman-Grean polarization interferometer, the improved Michelson architecture was used as beam-splitting unit, two linear polarizing plates with polarization direction of 0 and 45 were taken as phase-shifting elements. The interferometer can simultaneously capture two interferograms with phase shift of 90 with a single CCD camera. Phases were extracted and surface topography information was obtained by discrete Hilbert transform. A two-step phase-shifting interferometer was set up and glass plate surface was measured to verify the feasibility of this system. In the laboratory environment, the root mean square error of measurement results was less than 0.02. The system can be used in measurement of microsurface profile and has good stability.
To measure microsurface profile of an object, a spatial two-step phase-shifting interferometer was proposed based on an improved Michelson architecture. Based on a Tyman-Grean polarization interferometer, the improved Michelson architecture was used as beam-splitting unit, two linear polarizing plates with polarization direction of 0 and 45 were taken as phase-shifting elements. The interferometer can simultaneously capture two interferograms with phase shift of 90 with a single CCD camera. Phases were extracted and surface topography information was obtained by discrete Hilbert transform. A two-step phase-shifting interferometer was set up and glass plate surface was measured to verify the feasibility of this system. In the laboratory environment, the root mean square error of measurement results was less than 0.02. The system can be used in measurement of microsurface profile and has good stability.
2016, 40(1): 25-28.
doi: 10.7510/jgjs.issn.1001-3806.2016.01.006
Abstract:
In order to study the growth mechanism from graphite to nano-diamond by laser processing, micron graphite suspension was irradiated by nanosecond pulse laser and then was purified by acid high-temperature oxidation. X-ray diffraction, Raman spectroscopy and high-resolution transmission electron microscopy were used in theoretical analysis and experimental verification. The formation mechanism of nano-diamond was analyzed from thermodynamics and kinetics aspects respectively. Ultra-fine nano-diamond with particle size of 4nm~12nm and uniformly dispersion was synthesized. The results show that under the irradiation of nanosecond pulse laser, the transition from graphite to diamond is solid-vapor-liquid-solid phase transformation process. Compared with millisecond pulse laser, nanosecond laser with high intensity and short pulse width can supply larger super-cooling degree for diamond core growth and improve nucleation rate and growth velocity of nano-diamond. However, growth temperature range of nano-diamond is extremely small. Inevitable graphitization on the surface of diamond particles limits the further growth of nano-diamond.
In order to study the growth mechanism from graphite to nano-diamond by laser processing, micron graphite suspension was irradiated by nanosecond pulse laser and then was purified by acid high-temperature oxidation. X-ray diffraction, Raman spectroscopy and high-resolution transmission electron microscopy were used in theoretical analysis and experimental verification. The formation mechanism of nano-diamond was analyzed from thermodynamics and kinetics aspects respectively. Ultra-fine nano-diamond with particle size of 4nm~12nm and uniformly dispersion was synthesized. The results show that under the irradiation of nanosecond pulse laser, the transition from graphite to diamond is solid-vapor-liquid-solid phase transformation process. Compared with millisecond pulse laser, nanosecond laser with high intensity and short pulse width can supply larger super-cooling degree for diamond core growth and improve nucleation rate and growth velocity of nano-diamond. However, growth temperature range of nano-diamond is extremely small. Inevitable graphitization on the surface of diamond particles limits the further growth of nano-diamond.
2016, 40(1): 29-32.
doi: 10.7510/jgjs.issn.1001-3806.2016.01.007
Abstract:
In order to study effect of heat accumulation on microstructure and mechanical property of Ti-6Al-4V, two cylindrical samples and two tensile samples in 5mm and 10mm diameters of were made by means of laser direct forming. Heat accumulation was intense while forming 5mm sample. Martensite ' was found inside grains at the bottom and top positions, while acicular was found inside grains in the middle position. Heat accumulation was weak while forming 10mm sample. Martensite ' was found from the bottom to the top position. The samples of intense heat accumulation had a slightly weak tensile strength and three times of tensile plasticity. Experiment results show that intense heat accumulation while forming Ti-6Al-4V would make cooling rate decreased and microstructure would transform from martensite ' to acicular so that the tensile strength decreases and the tensile plasticity increases.
In order to study effect of heat accumulation on microstructure and mechanical property of Ti-6Al-4V, two cylindrical samples and two tensile samples in 5mm and 10mm diameters of were made by means of laser direct forming. Heat accumulation was intense while forming 5mm sample. Martensite ' was found inside grains at the bottom and top positions, while acicular was found inside grains in the middle position. Heat accumulation was weak while forming 10mm sample. Martensite ' was found from the bottom to the top position. The samples of intense heat accumulation had a slightly weak tensile strength and three times of tensile plasticity. Experiment results show that intense heat accumulation while forming Ti-6Al-4V would make cooling rate decreased and microstructure would transform from martensite ' to acicular so that the tensile strength decreases and the tensile plasticity increases.
2016, 40(1): 33-37.
doi: 10.7510/jgjs.issn.1001-3806.2016.01.008
Abstract:
In order to study laser welding post-weld-shift (PWS) of coaxial laser diodes based on finite element thermal theory and structural coupling theory, 3 beams laser welding model of coaxial laser diode was developed. Parameters affecting PWS were analyzed and meanwhile, correction experiment of laser hammer was studied. Coupling optical power value was obtained before and after laser welding and after correction. The simulation results demonstrate that power distribution and position distribution of three weld spots have influence on PWS of laser welding of coaxial laser diodes. Coupling light power is on the rise after laser hammering correction, and the maximum coupling power can be up to 94%. Finite element method can be used to prove the reasonable predict of PWS direction. The results have a certain guiding significance on production of coaxial laser in laser welding.
In order to study laser welding post-weld-shift (PWS) of coaxial laser diodes based on finite element thermal theory and structural coupling theory, 3 beams laser welding model of coaxial laser diode was developed. Parameters affecting PWS were analyzed and meanwhile, correction experiment of laser hammer was studied. Coupling optical power value was obtained before and after laser welding and after correction. The simulation results demonstrate that power distribution and position distribution of three weld spots have influence on PWS of laser welding of coaxial laser diodes. Coupling light power is on the rise after laser hammering correction, and the maximum coupling power can be up to 94%. Finite element method can be used to prove the reasonable predict of PWS direction. The results have a certain guiding significance on production of coaxial laser in laser welding.
2016, 40(1): 38-41.
doi: 10.7510/jgjs.issn.1001-3806.2016.01.009
Abstract:
In order to obtain broadband antireflective single layer coating for high power laser amplifiers, stabilized SiO2 sol system with more widely particle size distribution was prepared from silica sol doped and regulated by organic polymer polyvinylpyrrolidone(PVP). Single-layer broadband antireflective coating was developed by sol-gel dipping method. The properties of sol were measured by nanoparticle analyzer and viscometer, the transmittance was measured by spectrophotometer and the coating structure was measured by X-ray spectrometer. The results indicate that the introduction of PVP into silica sol leads to wider distribution of silica sol particles, which makes the coatings have the graded characteristics of refractive index. Thus the coating is broadband and antireflective. The inside transmittance of coatings is higher than 99% in the 550nm~950nm. The single-layer broadband antireflection coating has the stable film performance and can be put to use without post-processing. The single-layer anti-refractive coating meets the requirement of high power laser amplifiers.
In order to obtain broadband antireflective single layer coating for high power laser amplifiers, stabilized SiO2 sol system with more widely particle size distribution was prepared from silica sol doped and regulated by organic polymer polyvinylpyrrolidone(PVP). Single-layer broadband antireflective coating was developed by sol-gel dipping method. The properties of sol were measured by nanoparticle analyzer and viscometer, the transmittance was measured by spectrophotometer and the coating structure was measured by X-ray spectrometer. The results indicate that the introduction of PVP into silica sol leads to wider distribution of silica sol particles, which makes the coatings have the graded characteristics of refractive index. Thus the coating is broadband and antireflective. The inside transmittance of coatings is higher than 99% in the 550nm~950nm. The single-layer broadband antireflection coating has the stable film performance and can be put to use without post-processing. The single-layer anti-refractive coating meets the requirement of high power laser amplifiers.
2016, 40(1): 42-46.
doi: 10.7510/jgjs.issn.1001-3806.2016.01.010
Abstract:
In order to reduce the disturbance of noise on human sphygmus signal and improve the precision of data acquisition, a new improved filtering method was proposed. Based on the characteristics of sphygmus signal and noise, by using empirical mode decomposition method, the appropriate wavelet basis was selected, the wavelet threshold function was improved and a modal coefficients was built suitable for the filtering of a sphygmus signal. And then, sphygmus signals were filtered by the structural modal coefficient. After theoretical analysis and experimental verification, ideal experimental data was obtained. The results show that the improved threshold algorithm not only overcomes the limitations of soft threshold and hard threshold, but also overcomes the edge effect problems effectively which is generated by Fourier transform. At the same time, combining with the empirical mode decomposition method, the filtering errors of low frequency noise are weakened and the adaptability of wavelet transform is enhanced. Compared with the traditional filtering methods, the new method can suppress noise effectively and help to improve the signal-to-noise ratio.
In order to reduce the disturbance of noise on human sphygmus signal and improve the precision of data acquisition, a new improved filtering method was proposed. Based on the characteristics of sphygmus signal and noise, by using empirical mode decomposition method, the appropriate wavelet basis was selected, the wavelet threshold function was improved and a modal coefficients was built suitable for the filtering of a sphygmus signal. And then, sphygmus signals were filtered by the structural modal coefficient. After theoretical analysis and experimental verification, ideal experimental data was obtained. The results show that the improved threshold algorithm not only overcomes the limitations of soft threshold and hard threshold, but also overcomes the edge effect problems effectively which is generated by Fourier transform. At the same time, combining with the empirical mode decomposition method, the filtering errors of low frequency noise are weakened and the adaptability of wavelet transform is enhanced. Compared with the traditional filtering methods, the new method can suppress noise effectively and help to improve the signal-to-noise ratio.
2016, 40(1): 47-52.
doi: 10.7510/jgjs.issn.1001-3806.2016.01.011
Abstract:
In order to reduce the impact of vibration on measurement accuracy and stability of a mobile wind lidar, a vibration-damping floating raft was designed by referring to the successful application of floating rafts in the field of ships. The damping performance of mobile system was analyzed in the circulation of harmonic excitation by using multi-body dynamics modeling method. The damping effects of dampers' parameters were obtained. According to the dampers' parameters and the selected model, the peak value of passing rate after calculation avoided effectively excitation frequency during vehicles' transportation. The values of passing rate were less than 1 in effective frequency range. Meanwhile, the vibration range under the action of shock after calculation wasn't beyond the effective range of damping. Experimental results were consistent with theoretical requirements. By comparing the wind speed measured with a lidar and balloons under the vibration, the effect of damping design on measurement precision is proved. By comparing the locking frequency effect of lidar in the stable situation and in the vibration situation, the reliability of damping design is further certified. The results show that the application of floating raft damping is reasonable and successful in mobile wind lidars.
In order to reduce the impact of vibration on measurement accuracy and stability of a mobile wind lidar, a vibration-damping floating raft was designed by referring to the successful application of floating rafts in the field of ships. The damping performance of mobile system was analyzed in the circulation of harmonic excitation by using multi-body dynamics modeling method. The damping effects of dampers' parameters were obtained. According to the dampers' parameters and the selected model, the peak value of passing rate after calculation avoided effectively excitation frequency during vehicles' transportation. The values of passing rate were less than 1 in effective frequency range. Meanwhile, the vibration range under the action of shock after calculation wasn't beyond the effective range of damping. Experimental results were consistent with theoretical requirements. By comparing the wind speed measured with a lidar and balloons under the vibration, the effect of damping design on measurement precision is proved. By comparing the locking frequency effect of lidar in the stable situation and in the vibration situation, the reliability of damping design is further certified. The results show that the application of floating raft damping is reasonable and successful in mobile wind lidars.
2016, 40(1): 53-59.
doi: 10.7510/jgjs.issn.1001-3806.2016.01.012
Abstract:
In order to simulate the light propagation in 1-D refractive-index-typed photonic crystal (PC) defect waveguide effectively, Hermite-Gaussian function expansion method was adopted. At first, the detailed theoretical derivations of the calculation method were presented. And then, dispersion relation, mode field patterns, energy control factor and equivalent refractive index of 1-D PC waveguides with different polarizations and different structural parameters were calculated. The results show that there are significant differences in the high-ordered modes between 1-D PC defect waveguides and step planar waveguides. The transmission of high-order modes can be controlled effectively by adjusting the structural parameters of 1-D PC.
In order to simulate the light propagation in 1-D refractive-index-typed photonic crystal (PC) defect waveguide effectively, Hermite-Gaussian function expansion method was adopted. At first, the detailed theoretical derivations of the calculation method were presented. And then, dispersion relation, mode field patterns, energy control factor and equivalent refractive index of 1-D PC waveguides with different polarizations and different structural parameters were calculated. The results show that there are significant differences in the high-ordered modes between 1-D PC defect waveguides and step planar waveguides. The transmission of high-order modes can be controlled effectively by adjusting the structural parameters of 1-D PC.
2016, 40(1): 60-63.
doi: 10.7510/jgjs.issn.1001-3806.2016.01.013
Abstract:
In order to control laser wavelengths output of laser by suspending period-adjustable gratings, a structure combining microdriver of micro-electro-mechanical system(MEMS) technology with grating of distributed feedback (DFB) laser was proposed. According to rigorous coupled-wave theory (RCWA) and medium slab waveguide theory, using infinite element software COMSOL, a two-dimensional steady physical model of wavelength-adjustable DFB laser based on GaN was constructed for C-band in optical communication. 2-D electric field mode picture and lasing wavelength linewidth picture at 1550nm were analyzed and the corresponding relationship between grating period and lasing wavelength was gotten. The results show that, with certain structural parameters such as grating lattice thickness, height and gain layer thickness, lasing wavelength and grating period present similar linear relationships being consistent with theoretical analysis. The study will give good theoretical guidance for carrying out the design and preparation of the device.
In order to control laser wavelengths output of laser by suspending period-adjustable gratings, a structure combining microdriver of micro-electro-mechanical system(MEMS) technology with grating of distributed feedback (DFB) laser was proposed. According to rigorous coupled-wave theory (RCWA) and medium slab waveguide theory, using infinite element software COMSOL, a two-dimensional steady physical model of wavelength-adjustable DFB laser based on GaN was constructed for C-band in optical communication. 2-D electric field mode picture and lasing wavelength linewidth picture at 1550nm were analyzed and the corresponding relationship between grating period and lasing wavelength was gotten. The results show that, with certain structural parameters such as grating lattice thickness, height and gain layer thickness, lasing wavelength and grating period present similar linear relationships being consistent with theoretical analysis. The study will give good theoretical guidance for carrying out the design and preparation of the device.
2016, 40(1): 64-67.
doi: 10.7510/jgjs.issn.1001-3806.2016.01.014
Abstract:
In order to transport acoustic signal passively in some emergent cases, a fiber acoustic sensor was designed based on the principle of an optical fiber Michelson interferometer, processing techniques of elastic discs and optical fiber adhesion, 33 coupler phase demodulation. The expressions of three phase differences of output signals were presented, and the average phase differences were calculated based on the least square method. Simulation data and test data were acquired. Experimental results demonstrate that a fiber acoustic sensor can restore acoustic signal accurately and effectively within designed bandwidth. A fiber acoustic sensor can be used in emergent environments such as severe electro-magnetic situation. The test results verify the feasibility of a fiber acoustic sensor.
In order to transport acoustic signal passively in some emergent cases, a fiber acoustic sensor was designed based on the principle of an optical fiber Michelson interferometer, processing techniques of elastic discs and optical fiber adhesion, 33 coupler phase demodulation. The expressions of three phase differences of output signals were presented, and the average phase differences were calculated based on the least square method. Simulation data and test data were acquired. Experimental results demonstrate that a fiber acoustic sensor can restore acoustic signal accurately and effectively within designed bandwidth. A fiber acoustic sensor can be used in emergent environments such as severe electro-magnetic situation. The test results verify the feasibility of a fiber acoustic sensor.
2016, 40(1): 68-72.
doi: 10.7510/jgjs.issn.1001-3806.2016.01.015
Abstract:
In order to solve the problem of measurement error and blind zone because of light obstruction and obtain a satisfactory 3-D shape of in-pipe surface, a novel 3-D shape inspection system for in-pipe surfaces was proposed. The system was set up with a circular structured light to illuminate vertically and dual complementary metal oxide semiconductor cameras to record images simultaneously. Image process algorithm and calibration method for the inspection system were founded. The results of verification experiment show that standard deviation of the system is 0.50mm. The system has good ability to solve the problem of blind zone, reduce the measurement error, and obtain whole 3-D shapes of in-pipe surfaces.
In order to solve the problem of measurement error and blind zone because of light obstruction and obtain a satisfactory 3-D shape of in-pipe surface, a novel 3-D shape inspection system for in-pipe surfaces was proposed. The system was set up with a circular structured light to illuminate vertically and dual complementary metal oxide semiconductor cameras to record images simultaneously. Image process algorithm and calibration method for the inspection system were founded. The results of verification experiment show that standard deviation of the system is 0.50mm. The system has good ability to solve the problem of blind zone, reduce the measurement error, and obtain whole 3-D shapes of in-pipe surfaces.
2016, 40(1): 73-77.
doi: 10.7510/jgjs.issn.1001-3806.2016.01.016
Abstract:
To meet requirements of laser strengthened machines for mould industry, a multi-axis laser machine was constructed. On the basis of ordinary three-axis computer numerical control machine tools, spindle part of the ordinary machine was improved by adding two rotary axes, a laser and a CCD observation system. Positioning accuracy and repeatable positioning accuracy of the machine motion axis was measured and compensated by a laser interferometer. Motion features of the machine and characteristics of laser processing were analyzed. Post-processing of the multi-axis laser strength machine was analyzed theoretically and verified experimentally by using UG NX post-processing editing tool. The results show that positioning accuracy of the machine is less than 0.05mm after compensation, repetition positioning accuracy is 0.02mm. Laser strengthening treatment achieves successfully by using UG NX post-processing editor on machine tool. Experimental results show the feasibility and versatility of a multi-axis laser machine and post-processing. It is helpful for the upgrade from ordinary machine tool to laser processing equipment.
To meet requirements of laser strengthened machines for mould industry, a multi-axis laser machine was constructed. On the basis of ordinary three-axis computer numerical control machine tools, spindle part of the ordinary machine was improved by adding two rotary axes, a laser and a CCD observation system. Positioning accuracy and repeatable positioning accuracy of the machine motion axis was measured and compensated by a laser interferometer. Motion features of the machine and characteristics of laser processing were analyzed. Post-processing of the multi-axis laser strength machine was analyzed theoretically and verified experimentally by using UG NX post-processing editing tool. The results show that positioning accuracy of the machine is less than 0.05mm after compensation, repetition positioning accuracy is 0.02mm. Laser strengthening treatment achieves successfully by using UG NX post-processing editor on machine tool. Experimental results show the feasibility and versatility of a multi-axis laser machine and post-processing. It is helpful for the upgrade from ordinary machine tool to laser processing equipment.
2016, 40(1): 78-81.
doi: 10.7510/jgjs.issn.1001-3806.2016.01.017
Abstract:
In order to explore change of transmission spectrum of magneto-optical photonic crystal in external magnetic field, theoretical analysis and simulation calculation were carried out based on 44 transfer matrix method. Simulation results illustrated that when external magnetic field exists, the defect-mode of mirror photonic crystal would split into two modes under the effect of external magnetic field and the number of photonic crystal layers. And two modes are corresponding to the left-hand and the right-hand circular polarization waves respectively. The frequency difference between the left-hand and the right-hand circular polarization waves increases with the increase of external magnetic field. Only when photonic crystal layers are more than seven layers, defect-mode could have high Q value, which means defect-mode splitting can be clearly observed. The tunable feature of magneto-optical photonic crystal can be applied to design new filters.
In order to explore change of transmission spectrum of magneto-optical photonic crystal in external magnetic field, theoretical analysis and simulation calculation were carried out based on 44 transfer matrix method. Simulation results illustrated that when external magnetic field exists, the defect-mode of mirror photonic crystal would split into two modes under the effect of external magnetic field and the number of photonic crystal layers. And two modes are corresponding to the left-hand and the right-hand circular polarization waves respectively. The frequency difference between the left-hand and the right-hand circular polarization waves increases with the increase of external magnetic field. Only when photonic crystal layers are more than seven layers, defect-mode could have high Q value, which means defect-mode splitting can be clearly observed. The tunable feature of magneto-optical photonic crystal can be applied to design new filters.
2016, 40(1): 82-85.
doi: 10.7510/jgjs.issn.1001-3806.2016.01.018
Abstract:
Small-hole components have typical details of stress concentration so that they are easy to produce fatigue cracks under fatigue load and the usage performance and service life of critical structures are easily affected. In order to study effect of two-side laser shock processing (LSP) order on strengthening of small-hole specimens, fatigue tensile tests of TC4-DT hole components by two-side LSP simultaneously and two-side LSP successively were carried out. ABAQUS finite element software was adopted to conduct simulation study on residual stress distribution of TC4-DT hole components after different two-side LSP. The results show that the specimen fatigue gain after two-side simultaneous LSP is above 2 times than that after two-side successive LSP. Residual stress distribution of a hole component after two-side simultaneous LSP is more homogeneous. And the fatigue source deviates from the midpoint of the thickness significantly. The difference of residual stress of two LSP surfaces is large after two-side successive LSP. The simulation results have good agreement with the experiment results.
Small-hole components have typical details of stress concentration so that they are easy to produce fatigue cracks under fatigue load and the usage performance and service life of critical structures are easily affected. In order to study effect of two-side laser shock processing (LSP) order on strengthening of small-hole specimens, fatigue tensile tests of TC4-DT hole components by two-side LSP simultaneously and two-side LSP successively were carried out. ABAQUS finite element software was adopted to conduct simulation study on residual stress distribution of TC4-DT hole components after different two-side LSP. The results show that the specimen fatigue gain after two-side simultaneous LSP is above 2 times than that after two-side successive LSP. Residual stress distribution of a hole component after two-side simultaneous LSP is more homogeneous. And the fatigue source deviates from the midpoint of the thickness significantly. The difference of residual stress of two LSP surfaces is large after two-side successive LSP. The simulation results have good agreement with the experiment results.
2016, 40(1): 86-89.
doi: 10.7510/jgjs.issn.1001-3806.2016.01.019
Abstract:
In order to identify the invasion of vibration signal, a recognition algorithm based on Mel frequency cepstral coefficients (MFCC) was introduced according to the feature of vibration signal, taking processing method of voice signal as a reference and comparing with original spectrum analysis algorithm based on fast Fourier transform (FFT) after the investigation of distributed optical fiber vibration sensor and vibration signal recognition technology.。In the new algorithm, the vibration signal was analyzed in frequency domain. MFCC under different conditions was extracted and was taken as a new characteristic parameter. After comparing the experimental results, false alarm rates of both the algorithms are 27.5% and 7.5% respectively. The results show that false alarm rate of the algorithm based on MFCC can be reduced by 20% or more compared with the algorithm based on FFT. Obviously, under the premise of not omitting, MFCC algorithm with lower false alarm rate is more suitable for security systems.
In order to identify the invasion of vibration signal, a recognition algorithm based on Mel frequency cepstral coefficients (MFCC) was introduced according to the feature of vibration signal, taking processing method of voice signal as a reference and comparing with original spectrum analysis algorithm based on fast Fourier transform (FFT) after the investigation of distributed optical fiber vibration sensor and vibration signal recognition technology.。In the new algorithm, the vibration signal was analyzed in frequency domain. MFCC under different conditions was extracted and was taken as a new characteristic parameter. After comparing the experimental results, false alarm rates of both the algorithms are 27.5% and 7.5% respectively. The results show that false alarm rate of the algorithm based on MFCC can be reduced by 20% or more compared with the algorithm based on FFT. Obviously, under the premise of not omitting, MFCC algorithm with lower false alarm rate is more suitable for security systems.
2016, 40(1): 90-93.
doi: 10.7510/jgjs.issn.1001-3806.2016.01.020
Abstract:
In order to investigate the effect of one-side and two-side laser shock processing (LSP) on 7050-T7451 aluminum alloy small-hole specimens, the residual compressive stress distribution was analyzed with finite element analysis software ABAQUS and the residual stress curves and fracture morphology were compared. The results show that the residual compressive stress introduced by two-side LSP is 120MPa, larger than that induced by one-side LSP and the front and reserve side stress distribution of two-side LSP is more reasonable. The distance from fatigue source group to treatment side after one-side LSP is 2.54mm and deviates from the dimension centre. Fatigue source group locates in the middle of the thickness after two-side LSP. Fatigue lives increase 53.3% and 156.2% after one-side and two-side LSP respectively. The research shows the guidance to parameter selection of one-side and two-side LSP.
In order to investigate the effect of one-side and two-side laser shock processing (LSP) on 7050-T7451 aluminum alloy small-hole specimens, the residual compressive stress distribution was analyzed with finite element analysis software ABAQUS and the residual stress curves and fracture morphology were compared. The results show that the residual compressive stress introduced by two-side LSP is 120MPa, larger than that induced by one-side LSP and the front and reserve side stress distribution of two-side LSP is more reasonable. The distance from fatigue source group to treatment side after one-side LSP is 2.54mm and deviates from the dimension centre. Fatigue source group locates in the middle of the thickness after two-side LSP. Fatigue lives increase 53.3% and 156.2% after one-side and two-side LSP respectively. The research shows the guidance to parameter selection of one-side and two-side LSP.
2016, 40(1): 94-98.
doi: 10.7510/jgjs.issn.1001-3806.2016.01.021
Abstract:
In a coherent optical orthogonal frequency-division multiplexing transmission system with forward-pumped Raman amplification, the interplay between Raman pump relative intensity noise and cross-phase modulation leads to relative phase noise inducing non-negligible performance degradation. In order to solve this problem, by numerical analysis, theoretical analysis and experimental verification, effect of relative phase noise on the performance of a coherent optical communication system under different modulation formats was analyzed. The performance of a single-carrier orthogonal frequency division multiplexed system under the same conditions was compared with that of a multi-carrier system. The extent of system damage caused by relative phase noise was gotten. The results show that the relatively larger walk-off between pump and signal helps to suppress the impairment induced by the relative phase noise. A higher-order modulated signal is less tolerant to relative phase noise than a lower-order signal. With the same spectral efficiency, the quadrature-amplitude modulation format shows better tolerance to relative phase noise than phase-shift keying.
In a coherent optical orthogonal frequency-division multiplexing transmission system with forward-pumped Raman amplification, the interplay between Raman pump relative intensity noise and cross-phase modulation leads to relative phase noise inducing non-negligible performance degradation. In order to solve this problem, by numerical analysis, theoretical analysis and experimental verification, effect of relative phase noise on the performance of a coherent optical communication system under different modulation formats was analyzed. The performance of a single-carrier orthogonal frequency division multiplexed system under the same conditions was compared with that of a multi-carrier system. The extent of system damage caused by relative phase noise was gotten. The results show that the relatively larger walk-off between pump and signal helps to suppress the impairment induced by the relative phase noise. A higher-order modulated signal is less tolerant to relative phase noise than a lower-order signal. With the same spectral efficiency, the quadrature-amplitude modulation format shows better tolerance to relative phase noise than phase-shift keying.
2016, 40(1): 99-102.
doi: 10.7510/jgjs.issn.1001-3806.2016.01.022
Abstract:
For the purpose of calibration of a forward-scattering spectrometer probe (FSSP), a pinhole-disc calibration apparatus was designed based on diffraction technology. After calculation and simulation of Mie scattering and Fraunhofer diffraction power, the conversion relationships between the pinhole diameter and aerosol particle size were gotten. Parameters of calibration apparatus were gained after calculation based on the conversion relationship. After theoretical analysis and experimental verification, measurement uncertainty of standard particles was delivered to cloud particle spectrometer probe. And then, after the experiment of rotating pinhole disc, measurement uncertainty was passed to the calibration apparatus. Experimental results of calibration apparatus verified theoretical analysis. The results show that calibration apparatus has feasible calibration scheme with high efficiency, large calibration range, good measurement discrete uniformity and good repeatability. The study is helpful for calibration technology of spectrometer probes.
For the purpose of calibration of a forward-scattering spectrometer probe (FSSP), a pinhole-disc calibration apparatus was designed based on diffraction technology. After calculation and simulation of Mie scattering and Fraunhofer diffraction power, the conversion relationships between the pinhole diameter and aerosol particle size were gotten. Parameters of calibration apparatus were gained after calculation based on the conversion relationship. After theoretical analysis and experimental verification, measurement uncertainty of standard particles was delivered to cloud particle spectrometer probe. And then, after the experiment of rotating pinhole disc, measurement uncertainty was passed to the calibration apparatus. Experimental results of calibration apparatus verified theoretical analysis. The results show that calibration apparatus has feasible calibration scheme with high efficiency, large calibration range, good measurement discrete uniformity and good repeatability. The study is helpful for calibration technology of spectrometer probes.
2016, 40(1): 103-108.
doi: 10.7510/jgjs.issn.1001-3806.2016.01.023
Abstract:
The application of closed-loop control system in laser remanufacture is important to improve dimension precision, automation of forming course and intellectualization and has broad space to develop. Typical closed-loop control systems adopting molten geometry, 3-D size, molten pool temperature, laser power and multi-signal combination as monitoring methods, were analyzed from the principle and structures of closed-loop control systems. Meanwhile, the main control methods, such as laser position adjustment, powder feeding rate regulation or laser power control were introduced. Further, key links of construction were summarized in view of top-level design, sensor accuracy, algorithm complexity, reliability and system real-time. Based on the analysis of progress and related limitations of closed-loop control systems aboard and in China, construction difficulty of closed-loop control system was analyzed and concluded. The development directions, such as algorithm intellectualization, sensors integration, controlling parameters comprehensiveness, monitoring controlling network, were also put forward.
The application of closed-loop control system in laser remanufacture is important to improve dimension precision, automation of forming course and intellectualization and has broad space to develop. Typical closed-loop control systems adopting molten geometry, 3-D size, molten pool temperature, laser power and multi-signal combination as monitoring methods, were analyzed from the principle and structures of closed-loop control systems. Meanwhile, the main control methods, such as laser position adjustment, powder feeding rate regulation or laser power control were introduced. Further, key links of construction were summarized in view of top-level design, sensor accuracy, algorithm complexity, reliability and system real-time. Based on the analysis of progress and related limitations of closed-loop control systems aboard and in China, construction difficulty of closed-loop control system was analyzed and concluded. The development directions, such as algorithm intellectualization, sensors integration, controlling parameters comprehensiveness, monitoring controlling network, were also put forward.
2016, 40(1): 109-112.
doi: 10.7510/jgjs.issn.1001-3806.2016.01.024
Abstract:
In order to improve the practicability of multi-wavelength optical pulse equipment, a stable dual-wavelength semiconductor fiber ring laser was proposed and demonstrated by using dual-wavelength principle. Effects of ring cavity dispersion, filter pulse-width and modulation depth on output pulse were discussed. Experimental results are that repetition rate of dual-wavelength pulses is 5.0GHz and typical pulse-width is 20ps. Dual-wavelength pulses have good side-mode suppression ratios of 29.1dB (at 1554.75nm) and 29.7dB (at 1557.21nm) with typical output powers of -6.7dBm and -6.1dBm respectively. Output spectra are very stable with peak power fluctuation less than 0.5dB. This study is of great significance for the study of terahertz source and multi-wavelength optical pulse equipment.
In order to improve the practicability of multi-wavelength optical pulse equipment, a stable dual-wavelength semiconductor fiber ring laser was proposed and demonstrated by using dual-wavelength principle. Effects of ring cavity dispersion, filter pulse-width and modulation depth on output pulse were discussed. Experimental results are that repetition rate of dual-wavelength pulses is 5.0GHz and typical pulse-width is 20ps. Dual-wavelength pulses have good side-mode suppression ratios of 29.1dB (at 1554.75nm) and 29.7dB (at 1557.21nm) with typical output powers of -6.7dBm and -6.1dBm respectively. Output spectra are very stable with peak power fluctuation less than 0.5dB. This study is of great significance for the study of terahertz source and multi-wavelength optical pulse equipment.
2016, 40(1): 113-117.
doi: 10.7510/jgjs.issn.1001-3806.2016.01.025
Abstract:
In order to reduce the relaxation oscillation noise of a diode pumped solid-state laser and improve its stability of output power, the intensity noise was suppressed by means of optoelectronic negative feedback. Theoretical characteristics of laser intensity noise were analyzed. According to the results of theoretical analysis, a proportion-integration-differention(PID) feedback control circuit was designed. By carrying out feedback circuit to suppress the laser intensity noise, ideal experimental data were obtained. When pumped power is 700mW, peak frequency of relaxation oscillation is 300kHz, intensity noise at relaxation oscillation peak and low frequency decreases to 45dB and 15dB respectively. When pumped power is 550mW, relaxation oscillation peak frequency is 250kHz, intensity noise at relaxation oscillation peak and low frequency decreases to 40dB and 10dB respectively. The results shows that the feedback control circuit can effectively reduce intensity noise of a diode pumped solid state laser and improve the stability of laser output power.
In order to reduce the relaxation oscillation noise of a diode pumped solid-state laser and improve its stability of output power, the intensity noise was suppressed by means of optoelectronic negative feedback. Theoretical characteristics of laser intensity noise were analyzed. According to the results of theoretical analysis, a proportion-integration-differention(PID) feedback control circuit was designed. By carrying out feedback circuit to suppress the laser intensity noise, ideal experimental data were obtained. When pumped power is 700mW, peak frequency of relaxation oscillation is 300kHz, intensity noise at relaxation oscillation peak and low frequency decreases to 45dB and 15dB respectively. When pumped power is 550mW, relaxation oscillation peak frequency is 250kHz, intensity noise at relaxation oscillation peak and low frequency decreases to 40dB and 10dB respectively. The results shows that the feedback control circuit can effectively reduce intensity noise of a diode pumped solid state laser and improve the stability of laser output power.
2016, 40(1): 118-121.
doi: 10.7510/jgjs.issn.1001-3806.2016.01.026
Abstract:
In order to achieve good filter performance of guided-mode resonance filters (GMRF) in visible light region, according to rigorous coupled wave theory and equivalent medium theory, a subwavelength GMRF filter was designed based on semiconductor material of ZnO. Simulation and analysis showed that reflection efficiency reached 100% at 475nm, 530nm and 650nm, with sideband reflectance below 4% and bandwidth less than 0.3nm. The results show that GMRF has excellent performance in red, green and blue wavelength region of visible light. GMRFs can be used as three-primary-color filters and are useful for color synthesis and modulation.
In order to achieve good filter performance of guided-mode resonance filters (GMRF) in visible light region, according to rigorous coupled wave theory and equivalent medium theory, a subwavelength GMRF filter was designed based on semiconductor material of ZnO. Simulation and analysis showed that reflection efficiency reached 100% at 475nm, 530nm and 650nm, with sideband reflectance below 4% and bandwidth less than 0.3nm. The results show that GMRF has excellent performance in red, green and blue wavelength region of visible light. GMRFs can be used as three-primary-color filters and are useful for color synthesis and modulation.
2016, 40(1): 122-125.
doi: 10.7510/jgjs.issn.1001-3806.2016.01.027
Abstract:
In order to solve the speckle problem in laser imaging systems, characteristics of laser speckle in imaging systems were studied with the fiber vibrated by a speaker driven by ULN2003 chip. In this experiment, using 532nm wavelength laser as light source of system and using linear CCD image sensor acquisition system to acquire laser speckle images, laser speckle contrast of plastic fiber was analyzed at different vibration frequencies. The results show that when fiber vibration amplitude is stable and vibration frequency increases from 0Hz to 20Hz, image speckle contrast decreases. When vibration frequency is more than 16Hz, image speckle contrast tends to be stable and can get good effect of speckle elimination. The study can be used for laser display, laser imaging and other fields.
In order to solve the speckle problem in laser imaging systems, characteristics of laser speckle in imaging systems were studied with the fiber vibrated by a speaker driven by ULN2003 chip. In this experiment, using 532nm wavelength laser as light source of system and using linear CCD image sensor acquisition system to acquire laser speckle images, laser speckle contrast of plastic fiber was analyzed at different vibration frequencies. The results show that when fiber vibration amplitude is stable and vibration frequency increases from 0Hz to 20Hz, image speckle contrast decreases. When vibration frequency is more than 16Hz, image speckle contrast tends to be stable and can get good effect of speckle elimination. The study can be used for laser display, laser imaging and other fields.
2016, 40(1): 126-130.
doi: 10.7510/jgjs.issn.1001-3806.2016.01.028
Abstract:
Because of the restriction of imaging principle, ultrasound images led toare always with low contrast and weak boundaries, segmentation effect of level set based on edge was not ideal. In order to improve segmentation precision and efficiency of ultrasound images, new a novel level set segmentation algorithm was proposed combining gradient information with regional information was proposed. Firstly, distance regularized level set evolution (DRLSE) model based on boundary was improved, regional information was put into boundary indicator function. And then, the improved boundary indicator function was used instead of DRLSE model's. Finally, a level set evolution model combining gradient information with regional information was obtained. The experimental results show that the model can accurately segment ultrasound images of thyroid tumor and the segmentation efficiency and precision are higher than DRLSE model.
Because of the restriction of imaging principle, ultrasound images led toare always with low contrast and weak boundaries, segmentation effect of level set based on edge was not ideal. In order to improve segmentation precision and efficiency of ultrasound images, new a novel level set segmentation algorithm was proposed combining gradient information with regional information was proposed. Firstly, distance regularized level set evolution (DRLSE) model based on boundary was improved, regional information was put into boundary indicator function. And then, the improved boundary indicator function was used instead of DRLSE model's. Finally, a level set evolution model combining gradient information with regional information was obtained. The experimental results show that the model can accurately segment ultrasound images of thyroid tumor and the segmentation efficiency and precision are higher than DRLSE model.
2016, 40(1): 131-135.
doi: 10.7510/jgjs.issn.1001-3806.2016.01.029
Abstract:
In order to measure the phase modulation of liquid crystal optical phased arrays(LCOPA) automatically with high resolution and high precision, Fourier quarter-wave-plate (FQW) method was adopted. On the basis of the conventional /4 wave-plate method, combined with the discrete Fourier transform algorithm to process data, higher accuracy was attained in spite of the influence of vibration and noise in surroundings. In the experiments, automatic test was accomplished with a computer controlling the stepping motor combing accessory devices such as CCD and FQW. The results showed that the repetitive test precision was less than 0.3 taking a standard /4 wave-plate as a test sample. The near-field phase distribution for a LCOPA developed by ourselves was obtained and its phase cycle and phase valley between the electrodes was observed.
In order to measure the phase modulation of liquid crystal optical phased arrays(LCOPA) automatically with high resolution and high precision, Fourier quarter-wave-plate (FQW) method was adopted. On the basis of the conventional /4 wave-plate method, combined with the discrete Fourier transform algorithm to process data, higher accuracy was attained in spite of the influence of vibration and noise in surroundings. In the experiments, automatic test was accomplished with a computer controlling the stepping motor combing accessory devices such as CCD and FQW. The results showed that the repetitive test precision was less than 0.3 taking a standard /4 wave-plate as a test sample. The near-field phase distribution for a LCOPA developed by ourselves was obtained and its phase cycle and phase valley between the electrodes was observed.
2016, 40(1): 136-140.
doi: 10.7510/jgjs.issn.1001-3806.2016.01.030
Abstract:
To deposit Fe film with smooth surface, accurate dimension, deposition area of optional nature, a YAG solid-state laser was used, Fe(CO)5 was used as liquid precursor and a certain thickness quartz plate was adopted to reduce byproducts. At the condition of laser power density of 1.0106W/cm2, laser frequency of 2.5kHz, laser scanning speed of 300mm/s and scan repetition of 200 times, a Fe layer in a certain thickness was deposited with better surface flatness. Experimental results show that laser power density influences surface quality of deposition layer stronger. Laser power intensity is one of the most important parameters determining whether the layer is deposited or not and the thickness of the layer. The results show that by laser-induced and using Fe(CO)5 as precursor, Fe film deposition can be achieved on copper surfaces.
To deposit Fe film with smooth surface, accurate dimension, deposition area of optional nature, a YAG solid-state laser was used, Fe(CO)5 was used as liquid precursor and a certain thickness quartz plate was adopted to reduce byproducts. At the condition of laser power density of 1.0106W/cm2, laser frequency of 2.5kHz, laser scanning speed of 300mm/s and scan repetition of 200 times, a Fe layer in a certain thickness was deposited with better surface flatness. Experimental results show that laser power density influences surface quality of deposition layer stronger. Laser power intensity is one of the most important parameters determining whether the layer is deposited or not and the thickness of the layer. The results show that by laser-induced and using Fe(CO)5 as precursor, Fe film deposition can be achieved on copper surfaces.
2016, 40(1): 141-147.
doi: 10.7510/jgjs.issn.1001-3806.2016.01.031
Abstract:
Single-frequency all-solid-state lasers are widely used in the fields of high resolution spectroscopy, coherent communication, radars, and gravitation-wave detection and so on. Single-frequency all-solid-state laser is one of the important research fields of all-solid-state lasers. To adopt appropriate single-frequency laser technology better and meet different requirements in applications, several techniques to realize single-frequency all-solid-state lasers were summarized, such as microcavity, coupled cavity, birefringent filters, F-P etalons in cavity, unidirectional ring cavity, twisted mode cavity. Their principles and developments at home and abroad were introduced. The characteristics and application situations were also compared and summarized.
Single-frequency all-solid-state lasers are widely used in the fields of high resolution spectroscopy, coherent communication, radars, and gravitation-wave detection and so on. Single-frequency all-solid-state laser is one of the important research fields of all-solid-state lasers. To adopt appropriate single-frequency laser technology better and meet different requirements in applications, several techniques to realize single-frequency all-solid-state lasers were summarized, such as microcavity, coupled cavity, birefringent filters, F-P etalons in cavity, unidirectional ring cavity, twisted mode cavity. Their principles and developments at home and abroad were introduced. The characteristics and application situations were also compared and summarized.
