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RSS2003 Vol. 27, No. 2
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2003, 27(2): 81-84,93.
[Abstract]
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Abstract:
Fe-based composite layers reinforced by in situ ZrC particles were formed by laser overlapping and single cladding using preplaced FeCSiB alloy powders on a medium carbon steel matrix. The morphologies,microstructures,interface structure and the distribution of the ZrC particles in the clad layers were observed with optical microscopy,field emission electric scanning microscopy (FEEM). The microstructure of ZrC-reinforced Fe-based composite layers is the typical γ austenite dendrite and cellular distributed on the eutectic substrate. The energy dispersive spectroscopy (EDS) analysis shows the reinforcements are in situ synthesis carbides which main compositions consist of transition elements Zr,Mo and carbon. The compound carbide particles distributed within dendrite and interdendritic regions with 1.96%,2.2%～3.84% volume fractions for single and overlapping layers respectively. The martensite transformation went with the rapid cooling processes also. The Fe-based composite layers are dense and free of cracks with a good metallurgical bonding between the layer and substrate. The microhardness values across layer cross section vary between 800HV0.2～1100HV0.2.
Fe-based composite layers reinforced by in situ ZrC particles were formed by laser overlapping and single cladding using preplaced FeCSiB alloy powders on a medium carbon steel matrix. The morphologies,microstructures,interface structure and the distribution of the ZrC particles in the clad layers were observed with optical microscopy,field emission electric scanning microscopy (FEEM). The microstructure of ZrC-reinforced Fe-based composite layers is the typical γ austenite dendrite and cellular distributed on the eutectic substrate. The energy dispersive spectroscopy (EDS) analysis shows the reinforcements are in situ synthesis carbides which main compositions consist of transition elements Zr,Mo and carbon. The compound carbide particles distributed within dendrite and interdendritic regions with 1.96%,2.2%～3.84% volume fractions for single and overlapping layers respectively. The martensite transformation went with the rapid cooling processes also. The Fe-based composite layers are dense and free of cracks with a good metallurgical bonding between the layer and substrate. The microhardness values across layer cross section vary between 800HV0.2～1100HV0.2.
2003, 27(2): 85-87.
Abstract:
An E-O Q-switched solid state Nd:YAG laser system including an oscillator and an amplifier is introduc ed.Intensive discussion and analysis are focused on an abnormal phenomenon:aleaked laser beam with quite high energy is reflected from one side of the polarizer.The leaked laser is detected,then a profound analysis is given to point toil lustrate the detected waveform.It has al so been discussed in detail how to improve the efficiency of the laser quality on some aspects.Finally,it is concluded how to make use of this phenomenon's wave form to guide the debugging of this kind of lasers.The conclusion has a great importance in industrial manufacture of the lasers.
An E-O Q-switched solid state Nd:YAG laser system including an oscillator and an amplifier is introduc ed.Intensive discussion and analysis are focused on an abnormal phenomenon:aleaked laser beam with quite high energy is reflected from one side of the polarizer.The leaked laser is detected,then a profound analysis is given to point toil lustrate the detected waveform.It has al so been discussed in detail how to improve the efficiency of the laser quality on some aspects.Finally,it is concluded how to make use of this phenomenon's wave form to guide the debugging of this kind of lasers.The conclusion has a great importance in industrial manufacture of the lasers.
2003, 27(2): 88-89.
Abstract:
The wake field is stimulated when a slice electron bunch transfers in the homoge neous plasma,and it transfers forward after the bunch.The wake field can be used to be the wiggler for SASE-FEL.The wiggler mechanism is analyzed and its space period,field intensity and the gain length are calculated.Based on SASE theory,this kind of wiggler is compared with APS wiggler.The result shows that the wake field wiggler is superior to the normal wiggler used currently.
The wake field is stimulated when a slice electron bunch transfers in the homoge neous plasma,and it transfers forward after the bunch.The wake field can be used to be the wiggler for SASE-FEL.The wiggler mechanism is analyzed and its space period,field intensity and the gain length are calculated.Based on SASE theory,this kind of wiggler is compared with APS wiggler.The result shows that the wake field wiggler is superior to the normal wiggler used currently.
2003, 27(2): 90-93.
Abstract:
A two-dimensional transient model for high speed laser remelt was presented by solving the heat conduction and convection equations through finite element method and multigrid method.The time dependent physical process of laser remelt under CW laser and pulse laser with high scanning speed (HSP)(2m/s) and lowscanning speed (LSP)(0.2m/s)were simulated.The result shows that the scanning speed has big impact on the streamline and the distribution of the composition.It also shows that the same area on surface may be heated by multi-pulses of laser under LSP while it only be heated by one pulse under HSP.The result indicates that during laser remelt,the surface of the melt pool changes,the middle hollows and the edge reises.In addition,the shape,the size,the average cooling rate of the pool and the cooling rate at the edge of the pool can be obtained through the results.These cooling rates are useful to analyze the microstructure.
A two-dimensional transient model for high speed laser remelt was presented by solving the heat conduction and convection equations through finite element method and multigrid method.The time dependent physical process of laser remelt under CW laser and pulse laser with high scanning speed (HSP)(2m/s) and lowscanning speed (LSP)(0.2m/s)were simulated.The result shows that the scanning speed has big impact on the streamline and the distribution of the composition.It also shows that the same area on surface may be heated by multi-pulses of laser under LSP while it only be heated by one pulse under HSP.The result indicates that during laser remelt,the surface of the melt pool changes,the middle hollows and the edge reises.In addition,the shape,the size,the average cooling rate of the pool and the cooling rate at the edge of the pool can be obtained through the results.These cooling rates are useful to analyze the microstructure.
2003, 27(2): 94-96,112.
Abstract:
A method is proposed to determinate the reflective,extinction coefficient and thickness of thin film material at the same time by means of transmission spectral and simulated annealing algorithm.The strict calculating formula and program diagram are provided.To check the accuracy and feasibility of the method,numerical simulation is first done,and then the SiNx thin films are tested.Simulated results are highly closed to theoretical values,and reproduced curve in terms of the experimental results conforms to initial experimental curve.This method has a lot of advantages such as no damage,simplicity of measurement,facility of manipulation,good stability,fast convergence and high accuracy.
A method is proposed to determinate the reflective,extinction coefficient and thickness of thin film material at the same time by means of transmission spectral and simulated annealing algorithm.The strict calculating formula and program diagram are provided.To check the accuracy and feasibility of the method,numerical simulation is first done,and then the SiNx thin films are tested.Simulated results are highly closed to theoretical values,and reproduced curve in terms of the experimental results conforms to initial experimental curve.This method has a lot of advantages such as no damage,simplicity of measurement,facility of manipulation,good stability,fast convergence and high accuracy.
2003, 27(2): 97-100.
Abstract:
Laser bending is a recently developed and highly flexible metal forming technique.In this paper,3D numerical study on laser bending under temperature gradient mechanism are carried out with ANSYS software.A finite element model of temperatu refield is built,the dynamic temperature field and temperature disribution under provided conditions are analyzed according to the numerical sumulation trsults,the relationships between the technique parameters and the peak temperature,temperature gradient are investigated.
Laser bending is a recently developed and highly flexible metal forming technique.In this paper,3D numerical study on laser bending under temperature gradient mechanism are carried out with ANSYS software.A finite element model of temperatu refield is built,the dynamic temperature field and temperature disribution under provided conditions are analyzed according to the numerical sumulation trsults,the relationships between the technique parameters and the peak temperature,temperature gradient are investigated.
2003, 27(2): 101-102,105.
Abstract:
The develpoment of frequency-doubled Nd:YAG laser,consisting of anoscillator,three amplifies,a KTP frequency doubler and etc.,is reported.The system can produce energy higher than 1J at 532nm.It operates at a pulse repetition rate of 1Hz,a pulse width of 6ns～9ns.An energy conversion efficience of 48% for second harmonic generation of 532nm radiation from 1064nm radiation has been achieved.
The develpoment of frequency-doubled Nd:YAG laser,consisting of anoscillator,three amplifies,a KTP frequency doubler and etc.,is reported.The system can produce energy higher than 1J at 532nm.It operates at a pulse repetition rate of 1Hz,a pulse width of 6ns～9ns.An energy conversion efficience of 48% for second harmonic generation of 532nm radiation from 1064nm radiation has been achieved.
2003, 27(2): 103-105.
Abstract:
The processing paraments of laser welding of aluminum alloy 2007 with high power Nd:YAG CW laser are studied.Pores and hot cracks are found in the welding seam. The experiments show that laser welding with filler wire Alsi12 cnaminimize hot crack due to the smallest amout of heat input into the ease material.
The processing paraments of laser welding of aluminum alloy 2007 with high power Nd:YAG CW laser are studied.Pores and hot cracks are found in the welding seam. The experiments show that laser welding with filler wire Alsi12 cnaminimize hot crack due to the smallest amout of heat input into the ease material.
2003, 27(2): 106-109.
Abstract:
The principle and affecting factors of laser polishing of diamond films are discussed.The theoretical model of laser polishing of diamond films and surface roughness of laser-polished diamond films are analysed.The composited polishing idea is proposed for fine polishing of diamond films,especially of thick fims.
The principle and affecting factors of laser polishing of diamond films are discussed.The theoretical model of laser polishing of diamond films and surface roughness of laser-polished diamond films are analysed.The composited polishing idea is proposed for fine polishing of diamond films,especially of thick fims.
2003, 27(2): 110-112.
Abstract:
According to black box theory,a system was designed to study 180° back scattering characteristic of the turbid media.The operation and determination principles are formulated in the paper.
According to black box theory,a system was designed to study 180° back scattering characteristic of the turbid media.The operation and determination principles are formulated in the paper.
2003, 27(2): 113-115.
Abstract:
The experiment that 18Cr2Ni4W steels were treated by carburizing and laser transformation hardening was carried out. The microst ructure of the treated steel was studied in detail by SEM,TEM and image analyzer. The results show that the microstructure obviously varies with the change of depth in laser hardened zone;the large amount of residual austenite is produced due to existence of ally elements in the steel during laser transformation hardening,which decrease surface hardness;with the scanning speed going up,the hardness is increased.
The experiment that 18Cr2Ni4W steels were treated by carburizing and laser transformation hardening was carried out. The microst ructure of the treated steel was studied in detail by SEM,TEM and image analyzer. The results show that the microstructure obviously varies with the change of depth in laser hardened zone;the large amount of residual austenite is produced due to existence of ally elements in the steel during laser transformation hardening,which decrease surface hardness;with the scanning speed going up,the hardness is increased.
2003, 27(2): 116-118,121.
Abstract:
A detailed discription about working properties of nanosecond optical parametric oscillators(OPO) is given. The main characteristics of nanosecond OPOs are illuminated. Several novel nonlinear crystals are shown and their properties are also discussed. At last a brief look forward of nan-osecond OPOs is presented.
A detailed discription about working properties of nanosecond optical parametric oscillators(OPO) is given. The main characteristics of nanosecond OPOs are illuminated. Several novel nonlinear crystals are shown and their properties are also discussed. At last a brief look forward of nan-osecond OPOs is presented.
2003, 27(2): 119-121.
Abstract:
Coatings,made of Co-Cr-W-Ni-Sialloy+20% SiCp,deposited by laser cladding on IF steel are introduced. Cross section of such coatings has been examined to reveal their microstructure using optical moic-roscope,scanning electron and XRD. There existed some crystallization morphologies in different regions,such as planar,cellar (at the bonding area),columnar and dendrite (at the center and near the surface). XRD showed that the primary phase γ-Co dendrite and Si2W,CoWSi,Cr3Si,CoSi2 existed in the coatings. The results also showed that the wear resistance of the clad layer improved by adding SiCp.
Coatings,made of Co-Cr-W-Ni-Sialloy+20% SiCp,deposited by laser cladding on IF steel are introduced. Cross section of such coatings has been examined to reveal their microstructure using optical moic-roscope,scanning electron and XRD. There existed some crystallization morphologies in different regions,such as planar,cellar (at the bonding area),columnar and dendrite (at the center and near the surface). XRD showed that the primary phase γ-Co dendrite and Si2W,CoWSi,Cr3Si,CoSi2 existed in the coatings. The results also showed that the wear resistance of the clad layer improved by adding SiCp.
2003, 27(2): 122-123,125.
Abstract:
Based on a simlified model of gain region,the propagation and amplification of capillary discharge X-ray within the cylindrical plasma with parabolic eletron density profile are studied with the geometrica loptics approximation. The change relation of light intensity of X-ray leaked from plasmas side is given.At the same time,we analyse the effect of ray on intensity distribution and beam figure.
Based on a simlified model of gain region,the propagation and amplification of capillary discharge X-ray within the cylindrical plasma with parabolic eletron density profile are studied with the geometrica loptics approximation. The change relation of light intensity of X-ray leaked from plasmas side is given.At the same time,we analyse the effect of ray on intensity distribution and beam figure.
2003, 27(2): 124-125.
Abstract:
In the paper,an accurate optical method to meausure thickness along the quartz optical axis is put forward,with which the measurement accuracy can get up to 0.002mm.
In the paper,an accurate optical method to meausure thickness along the quartz optical axis is put forward,with which the measurement accuracy can get up to 0.002mm.
2003, 27(2): 126-129.
Abstract:
By using the second order moments method and generalized Huygens-Fresnel diffraction integral,the transformation properties of a three-dimensional TEMm,n-mode Hermite-Gaussian beam passing th rough an optical symmetrizing system are studied in detail. It is shown that the symmetrization is complete,because,not only the symmetrizing transformation is achieved in the second order moments sense,but also the output beam becomes a circular one,and then retains its shape unchanged upon propagation.
By using the second order moments method and generalized Huygens-Fresnel diffraction integral,the transformation properties of a three-dimensional TEMm,n-mode Hermite-Gaussian beam passing th rough an optical symmetrizing system are studied in detail. It is shown that the symmetrization is complete,because,not only the symmetrizing transformation is achieved in the second order moments sense,but also the output beam becomes a circular one,and then retains its shape unchanged upon propagation.
2003, 27(2): 130-133.
Abstract:
This paper summarizes the state of the arts of pulsed laser remelting and pulsed laser phase transformation.Finally,the exisent problems and the developing trend of pulsed laser remelting and pulsed laser phase transformation are introduced in this paper.
This paper summarizes the state of the arts of pulsed laser remelting and pulsed laser phase transformation.Finally,the exisent problems and the developing trend of pulsed laser remelting and pulsed laser phase transformation are introduced in this paper.
2003, 27(2): 134-136.
Abstract:
The SBS Q-switched Raman shifting Nd:YAG laser is studied theoretically and experimentally. The output energy at the SBS Q-switched mode and dye Q-switched mode is compared.The way of improving the laser output has been proposed.
The SBS Q-switched Raman shifting Nd:YAG laser is studied theoretically and experimentally. The output energy at the SBS Q-switched mode and dye Q-switched mode is compared.The way of improving the laser output has been proposed.
2003, 27(2): 137-139.
Abstract:
The device of electron beam is adjusted and the voltage and current of diode can be changed in a certain range. The third continuum,which centers at 240nm,is obtained by electron beam pumping argon(0.3MPa). Among voltage and current of diode,one is kept fixed and the other is changed. The experimental results show that the intensity of the third continuum of argon increase with the voltage or current of diode.
The device of electron beam is adjusted and the voltage and current of diode can be changed in a certain range. The third continuum,which centers at 240nm,is obtained by electron beam pumping argon(0.3MPa). Among voltage and current of diode,one is kept fixed and the other is changed. The experimental results show that the intensity of the third continuum of argon increase with the voltage or current of diode.
2003, 27(2): 140-142.
Abstract:
In the paper,the merits of laser diode pumped solid state ring laser are introduced. The gyroscope can be made in solid-state,the quality of the beam can be improved and the dead lock can be reduced. But because of the multi longitudinal mode the precision of the gyroscope is decreased. Methods of longitudinal mode selection are discussed. Meantime these methods are compared,dispersion,F-P etalon,composite cavity etc. The con clusion is that F-P etalon is the most effective method to realize the single-longitudinal mode and others will be validated in the experiments.
In the paper,the merits of laser diode pumped solid state ring laser are introduced. The gyroscope can be made in solid-state,the quality of the beam can be improved and the dead lock can be reduced. But because of the multi longitudinal mode the precision of the gyroscope is decreased. Methods of longitudinal mode selection are discussed. Meantime these methods are compared,dispersion,F-P etalon,composite cavity etc. The con clusion is that F-P etalon is the most effective method to realize the single-longitudinal mode and others will be validated in the experiments.
2003, 27(2): 143-144,149.
Abstract:
The coaction of scanning laser with material processed impacts the quality of parts and processing efficiency. The scanning laser energy and its distribution determine the accuracy and performance of SLS parts. The scanning laser energy and its distribution are analyzed,and influence of the relational parameter on scanning laser energy and its distribution is discussed in this paper. Then it is concluded that the relation of scanning laser energy with scanning space is nonlinear,and its distribution is associated with scanning space,and the energy and its distribution are associated with beam diameter and scanning speed,but is irrespective with number of scanning laser lines.
The coaction of scanning laser with material processed impacts the quality of parts and processing efficiency. The scanning laser energy and its distribution determine the accuracy and performance of SLS parts. The scanning laser energy and its distribution are analyzed,and influence of the relational parameter on scanning laser energy and its distribution is discussed in this paper. Then it is concluded that the relation of scanning laser energy with scanning space is nonlinear,and its distribution is associated with scanning space,and the energy and its distribution are associated with beam diameter and scanning speed,but is irrespective with number of scanning laser lines.
2003, 27(2): 145-146.
Abstract:
Properties of YAG laser Q-switched by SBS without back reflective mirror were investigated,and laser pulse was obtained at repetition rate of 1Hz and 5Hz after optimizing lens focal length,length of cell and position of lens focal point.
Properties of YAG laser Q-switched by SBS without back reflective mirror were investigated,and laser pulse was obtained at repetition rate of 1Hz and 5Hz after optimizing lens focal length,length of cell and position of lens focal point.
2003, 27(2): 147-149.
Abstract:
Based on the theory of matrix synthesis and decomposition,two novel types of optical system for transforming three dimensional astigmatic Hermite-Gaussian beams into symmetrical Laguerre Gaussian beams are proposed and illustrated with numerical examples.
Based on the theory of matrix synthesis and decomposition,two novel types of optical system for transforming three dimensional astigmatic Hermite-Gaussian beams into symmetrical Laguerre Gaussian beams are proposed and illustrated with numerical examples.
2003, 27(2): 150-152.
Abstract:
By means of the Fourier series expansion,an approximate analytical propagation equation of flattened Gaussian beams(FGBs) passing through an apertured paraxial ABCD optical system is derived,and illustr ated with numerical examples,when the transmissivity of the aperture is T(x)=cos(Ωx). The hard-edged aperture can be regarded as a special case of Ω=0. Numerical calculations results obtained by the straightforward integration of the Collins formula and our analytical equation are given,showing a good consistency within a small error range.
By means of the Fourier series expansion,an approximate analytical propagation equation of flattened Gaussian beams(FGBs) passing through an apertured paraxial ABCD optical system is derived,and illustr ated with numerical examples,when the transmissivity of the aperture is T(x)=cos(Ωx). The hard-edged aperture can be regarded as a special case of Ω=0. Numerical calculations results obtained by the straightforward integration of the Collins formula and our analytical equation are given,showing a good consistency within a small error range.
2003, 27(2): 153-154,157.
Abstract:
This paper measured output power density of He-Ne laser and radiance of cavity resonator,and analysed its irradiation damage on the basis of maximum permissible exposure(MPE) of eye and skin. In the end,some protections were proposed.
This paper measured output power density of He-Ne laser and radiance of cavity resonator,and analysed its irradiation damage on the basis of maximum permissible exposure(MPE) of eye and skin. In the end,some protections were proposed.
2003, 27(2): 155-157.
Abstract:
The propagation of Hermite Gaussian beams beyond the paraxial approximation is studied through the series expansion. The validity of the expansion formula is illustrated with numerical examples. It is shown that the formula becomes divergent,if the beam width is comparable with the wavelength. The corresponding physical analysis is also made.
The propagation of Hermite Gaussian beams beyond the paraxial approximation is studied through the series expansion. The validity of the expansion formula is illustrated with numerical examples. It is shown that the formula becomes divergent,if the beam width is comparable with the wavelength. The corresponding physical analysis is also made.
2003, 27(2): 158-159.
Abstract:
The misalignment loss of the grating in the wave guide CO2 laser is studied in this paper. And a experiment method for grating obliquity adjusting is also discussed with its accuracy.
The misalignment loss of the grating in the wave guide CO2 laser is studied in this paper. And a experiment method for grating obliquity adjusting is also discussed with its accuracy.
2003, 27(2): 160-160.
Abstract:
Based on ureteroscope an d Ho:YAG laser,31 uretera caculi cases are treated.Among them,29 cases were cured in a short duration.The result shows that this kind of treatment is effective and time save for ureteral calculi cases.
Based on ureteroscope an d Ho:YAG laser,31 uretera caculi cases are treated.Among them,29 cases were cured in a short duration.The result shows that this kind of treatment is effective and time save for ureteral calculi cases.
