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RSS2000 Vol. 24, No. 2
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2000, 24(2): 65-68.
[Abstract]
[PDF 1114KB]
Abstract:
High power density(GW/cm2)short pulse(ns) laser was used for laser shock processing(LSP)45 carbon steel.The effect of LSP on the microstructure and structural changes of 45 carbon steel was studied.The fatigue fracture shapes of unshocked section and shocked section of the sample were examined with the scanning electron microscope(SEM).The experimental results show that laser shock processing can make the fatigue crack of 45 carbon steel not easy to initiate and propagate.The fatigue life of 45 carbon steel was significantly increased.
High power density(GW/cm2)short pulse(ns) laser was used for laser shock processing(LSP)45 carbon steel.The effect of LSP on the microstructure and structural changes of 45 carbon steel was studied.The fatigue fracture shapes of unshocked section and shocked section of the sample were examined with the scanning electron microscope(SEM).The experimental results show that laser shock processing can make the fatigue crack of 45 carbon steel not easy to initiate and propagate.The fatigue life of 45 carbon steel was significantly increased.
2000, 24(2): 68-73.
Abstract:
This paper presents a review of the mechanism,procedure characteristics and the status of laser cleaning procedure,as well as the prospect of laser cleaning applications.It was pointed out that the laser cleaning technology has many advantages,comparing to the liquid cleaning and the ultrasonic cleaning,such as dry cleaning,no damage of the cleaned surface,low cast etc.So the laser cleaning can be used many fields or some specialized fields.
This paper presents a review of the mechanism,procedure characteristics and the status of laser cleaning procedure,as well as the prospect of laser cleaning applications.It was pointed out that the laser cleaning technology has many advantages,comparing to the liquid cleaning and the ultrasonic cleaning,such as dry cleaning,no damage of the cleaned surface,low cast etc.So the laser cleaning can be used many fields or some specialized fields.
2000, 24(2): 74-78.
Abstract:
With the help of regression analytical technology,two mathematical models are presented.One is about the relationship between laser power and laser cutting parameters,the other is about the relationship between cutting velocity and laser cutting parameters.Their errors have been analyzed. The models give the theory ground to increase the efficiency of production,improve the quality and reduce the energy.Experiments show that the models can meet the requirement of industrial manufacturing process.
With the help of regression analytical technology,two mathematical models are presented.One is about the relationship between laser power and laser cutting parameters,the other is about the relationship between cutting velocity and laser cutting parameters.Their errors have been analyzed. The models give the theory ground to increase the efficiency of production,improve the quality and reduce the energy.Experiments show that the models can meet the requirement of industrial manufacturing process.
2000, 24(2): 78-81.
Abstract:
The optical characteristics of jet injecting aerodynamic window with big exit aperture have studied experimentally. The Strehl ratio,wavefront aberration and coefficients of Zernike polynomial of laser beam,passed through the aerodynamic window,were given up from the data,collected by HARTMANN diagnostic apparatus. From these optical characteristics it can be analyze,that the injection flow pressure and the structure of aerodynamic window influence on the passed beam quality.It was shown that the passed beam will be divergence,as the injection flow pressure becomes large. It is related to that the axial grads of air density distribution,caused by gas flow from circular nozzle,become large. And heterogeneous distribution of air bleed hole makes the wavefront tilt so that the passed laser beam will shift.
The optical characteristics of jet injecting aerodynamic window with big exit aperture have studied experimentally. The Strehl ratio,wavefront aberration and coefficients of Zernike polynomial of laser beam,passed through the aerodynamic window,were given up from the data,collected by HARTMANN diagnostic apparatus. From these optical characteristics it can be analyze,that the injection flow pressure and the structure of aerodynamic window influence on the passed beam quality.It was shown that the passed beam will be divergence,as the injection flow pressure becomes large. It is related to that the axial grads of air density distribution,caused by gas flow from circular nozzle,become large. And heterogeneous distribution of air bleed hole makes the wavefront tilt so that the passed laser beam will shift.
2000, 24(2): 82-84.
Abstract:
With the help of a new multichannel speckle shearing photography,a study is conducted of influence on a copper thin slice strain after SMA is embedded. In this photography the rotating optical link converter is put in the light path to change the imaging positions so that the multichannel recording is realized.In one recording medium three speckle patterns of amamorphic state are recorded,and at the same time,with the help of full field filtering analysis,the amamorphic information of these channels be presented conveniently and compared easily.The paper gives theory analysis and experiment results. Which show that after embedding SMA,the matal material has stronger rigidity.
With the help of a new multichannel speckle shearing photography,a study is conducted of influence on a copper thin slice strain after SMA is embedded. In this photography the rotating optical link converter is put in the light path to change the imaging positions so that the multichannel recording is realized.In one recording medium three speckle patterns of amamorphic state are recorded,and at the same time,with the help of full field filtering analysis,the amamorphic information of these channels be presented conveniently and compared easily.The paper gives theory analysis and experiment results. Which show that after embedding SMA,the matal material has stronger rigidity.
2000, 24(2): 85-89.
Abstract:
For passive Q-switched solid state lasers including excite state absorption (ESA),the coupled rate equations is presented. By means of the adiabatic elimination approximation (AEA) and the Hopf bifurcation conditions,the series of multi-pulses produced by passive Q-switch correspond to the limit cycle on the phase plane of optic intensity and population inversion density. Threshold formula for giant pulses and analytical solution for pulses period or repetitive frequency are obtained. The phenomena about Cr4+:YAG saturable absorber Q-switched laser are explained. The calculated results accord with the experiment.
For passive Q-switched solid state lasers including excite state absorption (ESA),the coupled rate equations is presented. By means of the adiabatic elimination approximation (AEA) and the Hopf bifurcation conditions,the series of multi-pulses produced by passive Q-switch correspond to the limit cycle on the phase plane of optic intensity and population inversion density. Threshold formula for giant pulses and analytical solution for pulses period or repetitive frequency are obtained. The phenomena about Cr4+:YAG saturable absorber Q-switched laser are explained. The calculated results accord with the experiment.
2000, 24(2): 90-95.
Abstract:
In this paper,a mathematical model of keyhole mechanism of laser deep welding has been analyzed.We studied the relationship of the stability of weld pool with metallic vapor pressure and the relationship of metallic vapor with plasma.The effect of laser weld parameters(including laser mode,laser power,focusing condition,welding speed and assistant gas etc.)on weld pool behavior have been investigated in detail.Finally,we also have analyzed the weld pool behavior related weld structure and defects(such as crack and porosity etc.).
In this paper,a mathematical model of keyhole mechanism of laser deep welding has been analyzed.We studied the relationship of the stability of weld pool with metallic vapor pressure and the relationship of metallic vapor with plasma.The effect of laser weld parameters(including laser mode,laser power,focusing condition,welding speed and assistant gas etc.)on weld pool behavior have been investigated in detail.Finally,we also have analyzed the weld pool behavior related weld structure and defects(such as crack and porosity etc.).
2000, 24(2): 95-98.
Abstract:
In this paper,an aerodynamic nozzle was investigated for protecting the beam deliveray system and preventing optics pollution from ejected particle vaporized on metallic surface during high power CO2 laser welding. The suitable nozzle structure was designed on the basis of theoeretical analysis on moving trajectory of the ejected particle. The comparing experiments between aerodynamic nozzle and ordinary nozzle were performed to examine the influence of optics pollution on loss of laser power,porosity percentage of weld section; and efficient penetration depth,and also to inspect the distrubution of ejected particle on optics during laser welding. The studied results show that the aerodynamic nazzle substantially reduced the particle amount on the optics,so the loss of the laser power delivered to the workpiece was reduced,the effective weld lentgh was increased.The examination of the weld structure ensured that there was no interference with the quality of the weld due to the cross flow.
In this paper,an aerodynamic nozzle was investigated for protecting the beam deliveray system and preventing optics pollution from ejected particle vaporized on metallic surface during high power CO2 laser welding. The suitable nozzle structure was designed on the basis of theoeretical analysis on moving trajectory of the ejected particle. The comparing experiments between aerodynamic nozzle and ordinary nozzle were performed to examine the influence of optics pollution on loss of laser power,porosity percentage of weld section; and efficient penetration depth,and also to inspect the distrubution of ejected particle on optics during laser welding. The studied results show that the aerodynamic nazzle substantially reduced the particle amount on the optics,so the loss of the laser power delivered to the workpiece was reduced,the effective weld lentgh was increased.The examination of the weld structure ensured that there was no interference with the quality of the weld due to the cross flow.
2000, 24(2): 99-101.
Abstract:
The metal ultrafine powders have superior catalytic,magnetic and electrical properties.The conventional method to manufacturer the metal powder is evaporation condensation method,and the several heating sources,such as resistance,high frequency induction,plasma,electron beam or laser,are used.But these heating sources are used respectively as a single heating source in these system,so have some disadvantages or limitations.Now,we have fined a complex heating source,the laser high frequency induction heating source to manufacture ultrafine Zn powder,by utilizing evaporation condensation method.In our experimental setup,the output rate is 12g/min,and the average diameter of Zn powder is 33.20nm.
The metal ultrafine powders have superior catalytic,magnetic and electrical properties.The conventional method to manufacturer the metal powder is evaporation condensation method,and the several heating sources,such as resistance,high frequency induction,plasma,electron beam or laser,are used.But these heating sources are used respectively as a single heating source in these system,so have some disadvantages or limitations.Now,we have fined a complex heating source,the laser high frequency induction heating source to manufacture ultrafine Zn powder,by utilizing evaporation condensation method.In our experimental setup,the output rate is 12g/min,and the average diameter of Zn powder is 33.20nm.
2000, 24(2): 102-106.
Abstract:
Micromachined defects can be introduced into a semiconductor laser to improve spectral characteristics of the F-P laser. In this paper,the analytical expression of the output spectrum from the micromachined F-P diode laser (MMLD) has been deduced. Moreover,a brief account has been given to explain the side mode suppression of the MMLDs.
Micromachined defects can be introduced into a semiconductor laser to improve spectral characteristics of the F-P laser. In this paper,the analytical expression of the output spectrum from the micromachined F-P diode laser (MMLD) has been deduced. Moreover,a brief account has been given to explain the side mode suppression of the MMLDs.
2000, 24(2): 107-110.
Abstract:
An automatic laser power measurement apparatus has been developed by using single chip microcomputer technology.The operate principle,constitution structure and data processing program of this device are clarified.This device has the features of easy to operate,low cost and small error. Measurements show that the device is stable and practicable.
An automatic laser power measurement apparatus has been developed by using single chip microcomputer technology.The operate principle,constitution structure and data processing program of this device are clarified.This device has the features of easy to operate,low cost and small error. Measurements show that the device is stable and practicable.
2000, 24(2): 110-113.
Abstract:
The propagation properties of coherent and incoherent flattened Gaussian beams have been studied in detail. It has been pointed out that,to meet some requirements in practical applications,the partially coherent flattened Gaussian beam is a suitable choice,which can be realized by using the superposition of partially coherent finite Laguerre Gaussian modes or Hermite Gaussian modes.
The propagation properties of coherent and incoherent flattened Gaussian beams have been studied in detail. It has been pointed out that,to meet some requirements in practical applications,the partially coherent flattened Gaussian beam is a suitable choice,which can be realized by using the superposition of partially coherent finite Laguerre Gaussian modes or Hermite Gaussian modes.
2000, 24(2): 114-118.
Abstract:
Theoretical and experimental study has been carried out on Cr4+：YAG Q-switched,repetitive,conductive cooling,miniature(Ce,Nd):YAG lasers. The optimum operate condition is presented. Using a xenon flash lamp with 3.6～4.8J as the pump energy,we obtained repetitive(2～5pps) single pulse laser output of 10～15mJ with pulse width of 6～12ns.The operate ambient temperature range is +60℃～-40℃.
Theoretical and experimental study has been carried out on Cr4+：YAG Q-switched,repetitive,conductive cooling,miniature(Ce,Nd):YAG lasers. The optimum operate condition is presented. Using a xenon flash lamp with 3.6～4.8J as the pump energy,we obtained repetitive(2～5pps) single pulse laser output of 10～15mJ with pulse width of 6～12ns.The operate ambient temperature range is +60℃～-40℃.
2000, 24(2): 118-122.
Abstract:
Numerically solving equations governing the variations of the beam size and the curvature of wave front in the logarithmically nonlinear media (LNM),the propagating characteristics of Gaussian beams have been described in detail. With the aid of phase diagram,variations of parameters of Gaussian beams have been analyzed for different initial parameters. Using methods adopted in mechanics,the solitons of symmetrical breath mode and non symmetrical breath mode in propagation of Gaussian beams have been discussed.
Numerically solving equations governing the variations of the beam size and the curvature of wave front in the logarithmically nonlinear media (LNM),the propagating characteristics of Gaussian beams have been described in detail. With the aid of phase diagram,variations of parameters of Gaussian beams have been analyzed for different initial parameters. Using methods adopted in mechanics,the solitons of symmetrical breath mode and non symmetrical breath mode in propagation of Gaussian beams have been discussed.
2000, 24(2): 122-124.
Abstract:
Based on the polarization state in the resonant cavity,with the help of Qinc matrix,we anlyze the process which the cavity flowing empty slowly outputs square pulses.Experimental results conform to the analysis.
Based on the polarization state in the resonant cavity,with the help of Qinc matrix,we anlyze the process which the cavity flowing empty slowly outputs square pulses.Experimental results conform to the analysis.
2000, 24(2): 125-128.
Abstract:
First,this paper deduced the diffraction equation for refractive index phase modulation holographic grating,and pointed out that the diffraction efficiency was mainly influenced by refraction index modulation,and the diffraction efficiency of different levels came from many factors.The volume grating effect affected the diffraction efficiency of transmission hologram. This paper also discussed the factors that influenced the diffraction efficiency of scattering object,and proposed the amount of refraction index modulation was very small,the diffraction efficiency was mainly determined by chemical treatment.
First,this paper deduced the diffraction equation for refractive index phase modulation holographic grating,and pointed out that the diffraction efficiency was mainly influenced by refraction index modulation,and the diffraction efficiency of different levels came from many factors.The volume grating effect affected the diffraction efficiency of transmission hologram. This paper also discussed the factors that influenced the diffraction efficiency of scattering object,and proposed the amount of refraction index modulation was very small,the diffraction efficiency was mainly determined by chemical treatment.
2000, 24(2): 128-130.
Abstract:
A improved method using simple instrument to expand Gaussian distribution light field and get large range homogeneous ideal light field was presented.An optical setup used to expand Gaussian distribution light field was designed to improve the utilization ratio of light energy and satisfactory experimental results ware obtained.
A improved method using simple instrument to expand Gaussian distribution light field and get large range homogeneous ideal light field was presented.An optical setup used to expand Gaussian distribution light field was designed to improve the utilization ratio of light energy and satisfactory experimental results ware obtained.
