Proceedings Volume 2713

Fifth International Conference on Industrial Lasers and Laser Applications '95

Vladislav Ya. Panchenko, Vladimir S. Golubev
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Proceedings Volume 2713

Fifth International Conference on Industrial Lasers and Laser Applications '95

Vladislav Ya. Panchenko, Vladimir S. Golubev
View the digital version of this volume at SPIE Digital Libarary.

Volume Details

Date Published: 1 March 1996
Contents: 3 Sessions, 74 Papers, 0 Presentations
Conference: Fifth International Conference on Industrial Laser and Laser Applications '95 1995
Volume Number: 2713

Table of Contents

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Table of Contents

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  • Industrial Lasers: Physical Research, New Lasers, Engineering
  • Laser Materials Processing: Manufacturing Systems, Physical Models, Technology
  • Laser Applications: Rapid Object Manufacturing, Diagnostics, Measurement Systems
Industrial Lasers: Physical Research, New Lasers, Engineering
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Mathematical model of laser generation on the basis of Markov processes theory
Dmitry V. Zaitsev
The discrete nature of active media atoms, laser light photons and their Poisson distribution law allow us to apply correctly Markov processes theory with discrete states and continuous time to the description of laser generation process. The equations of photons quantity in laser resonator and population inversion are deduced. The results coincide with known equations. Equations of photons quantity dispersion and population inversion dispersion are deduced also. The analysis of these equations permits us to explain the operation of spiking pulsed multimode lasers.
Numerical modeling of a fast-axial-flow CO2 laser with considering viscosity and ambipolar diffusion
Ravil S. Galeev, A. A. Fedosov
A numerical method for analysis of a fast axial flow glow discharge carbon dioxide laser is developed. The method is based on the self-consistent solution to the two-dimensional steady- state Navier-Stokes equations in thin-shear-layer approximation (slender channel equations), the parabolized glow discharge equations, and the vibrational relaxation equations. The discharge equations include the continuity equations for the electrons, the positive and negative ions. The one-mode relaxation model for the vibrational kinetics and the plane-parallel optical resonator model are used. The present model is based on the assumption of the charge neutrality and limited by consideration of the positive column of discharge without taking into account the cathode-fall and anode-fall regions.
Amplification and nonlinear losses in relaxing laser mixture of continuous wave fast-axial-flow CO2 lasers
Michail G. Galushkin, Vladimir S. Golubev, V. V. Dembovetsky, et al.
Based on the solution of the self-consistent problem, the influence of laser mixture relaxing beyond the discharge region upon the continuous 600 W carbon-dioxide laser radiation has been investigated. It has been shown that beyond the discharge region, the resonance nonlinear absorption of radiation can originate in the discharge-free area within the certain range of gas velocity, energy input and resonator Q-factor values. The absorption dependence on radiation intensity is complicated in its nature and involves the influence of saturation effect, as well as the variation of excited molecules relaxation length in the radiation field. The values of output mirror reflection factor and the geometry parameters have been determined whereby the laser efficiency is at its maximum with regard to extra amplification of radiation in the relaxing gas mixture flow.
Influence of turbulent diffusion of excited molecules upon energy parameters of fast-axial-flow CO2 laser
Michail G. Galushkin, Vladimir S. Golubev, V. V. Dembovetsky, et al.
A quantitative study of beam extra amplification is conducted for carbon-dioxide lasers with fast axial turbulized gas flow. In this phenomenon, the dominant role is played by turbulent diffusion of excited molecules into the central saturation part of the beam. It has been shown that the decrease in beam radius causing the reduction of diffraction losses allows us to attain greater amplification owing to turbulent diffusion, and it is supported by experiment.
Theoretical analysis of a fast-axial-flow CO2 laser with the conical discharge tube
Ravil S. Galeev
A mathematical model of the fast axial flow carbon-dioxide laser (FAFL) with the glow discharge in a conical tube has been developed. The investigations of the dependence of the laser output power on the discharge tube geometry have been carried out. It is shown that the output power and the electrical-to-optical efficiency can be increased due to the conical discharge tube converging along the flow.
Principal trends in development of gas lasers with rf excitation
Nikolai A. Yatsenko
A review of the modern state and analysis of development methods of gas lasers with pumping of active medium by radio frequency capacitive discharge (RFCD) are given. Specific attention is paid to powerful technological lasers. The advantages and deficiencies of such pumping methods are considered. In particular, the main physical processes and specific constructional decisions, which permit us to realize the advantages of gas lasers rf excitation with the heaviest completeness, are discussed. The perspectives of their further development are defined.
Slab waveguide rf-excited CO2 laser for material processing
Alexander I. Dutov, N. A. Novoselov, V. N. Sokolov, et al.
Results of investigations of output power and beam divergence for a slab waveguide rf-excited carbon-dioxide laser are presented. Laser output of range 200 W and efficiency about 10% in a beam with near-diffraction-limit divergence has been achieved. In the repetitive-rate mode, the pulsed power was more than twice as much as the average one in the cw mode. After beam shaping telescope, the total beam divergence of 2-3 mrad at the 0.8 power level has been obtained.
Computer simulation of rf-excited diffusion-cooled slab CO2 laser
Alexander I. Dutov, Valentina N. Ivanova, Victor E. Semenov, et al.
A codes package of computer simulation of rf-excited cw slab carbon-dioxide laser with diffusion-cooling and hybrid waveguide-unstable resonator is presented. The package consists of four main parts: (1) structure of rf-discharge, (2) processes of inversion formation, (3) laser radiation propagation throughout the resonator, and (4) plasma chemical reactions in the active medium. The calculations of gain, output power, and near- and far-field patterns have been carried out. Comparison of calculated and experimental data has been fulfilled.
Resonator systems providing self-pumping oscillations in fast-flow gas lasers
O. Y. Nikolaeva, A. I. Odintsov, A. I. Fedosejev, et al.
The characteristics of a number of optical resonator systems providing the self-pulsing oscillation of operation in the fast flow gas lasers with the continuous excitation were examined. The considered systems were nonuniform mirror unstable resonator, unstable resonator with inhomogeneous medium excitation and generator-amplifier system. The calculations show the high efficiency of the systems as well as the possibilities for the monitoring of the self-modulated radiation parameters.
Amplifying optical scheme in high-power continuous-wave industrial CO2 lasers
Michail G. Galushkin, Vladimir S. Golubev, Oleg Alexeyevic Novodvorsky, et al.
Wavefront aberrations and Gaussian beam profile distortions have been experimentally studied in the amplifier using carbon-dioxide:N2:He mixture as the active medium, with transverse flowing and about 5 kW power. As a pumping generator a laser with single-mode stable resonator and beam power close to 1 kW was used. The obtained experimental data were correlated with the estimated values of beam power and wavefront distortions caused by thermal deformations of reflection mirrors and optical nonuniformities in active medium. It has been shown that the amplifying scheme enables us to improve the beam quality with retention of industrial carbon-dioxide-laser high power, provided there exists the agreement between the amplified beam and amplifier parameters.
High-power waveguide industrial CO2 lasers
Victor V. Vasiltsov, Michail G. Galushkin, Vladimir S. Golubev, et al.
The paper considers the experimental, engineering and model-physical aspects of development of high-power waveguide single-beam carbon-dioxide lasers for industrial applications. As an illustration, the parameters of the developed experimental model of this type of laser with 0.5 kW average beam power are presented and relevant critical problems are discussed. The results of inquiry into beam output characteristics are offered depending on different parameters. Main technical and economic data have been obtained.
Investigation of industrial CO2 laser beam characteristics with intracavity modulator
Vadim V. Samarkin, Oleg Alexeyevic Novodvorsky, Rafael Ya. Sagdeev, et al.
An investigation of energy, temporal and spatial characteristics of industrial carbon-dioxide laser beam with 1.5 kW average power has been undertaken under modulation of the resonator output mirror transmittance. The use of a mirror, based on Fabry-Perot interferometer for intracavity modulation permitted us to achieve pulse-periodical generation in the 0.1 - 2 kHz range of pulse repetition rate with pulse duration from 0.2 to 5 ms. The beam modulation depth was adjusted by control voltage amplitude and could reach 100%.
Development of self-contained mobile technological CO2 GDL on the basis of gas-turbine engine
Valerii K. Ikonnikov, V. P. Maliavine, V. A. Plotnikov, et al.
Cw carbon-dioxide lasers with the output power of 15 kW have been used in such modern technological processes as welding, cutting and surface hardening. However there arise the problems which require the increase of power up to 50 kW. As an example, to disassemble some nuclear reactors it is necessary to cut plates made of special types of stainless steel up to 330 mm thick. The work of Gorny et al. gives a simple formula representing the thickness of the cut metal h versus the absorbed laser beam power W, its diameter d, cutting rate v, gas flow rate through the cut area G and thermophysical characteristics of metal. We show substitution of well-known constants for stainless steel into the formula. Plots of this dependence are given for cutting rate of 0.1 and 0.3 cm/s with different gas flow rates. It follows from the plots that, first, in order to increase cut depth, a simultaneous increase of power and gas flow rate G are required and secondly, with regard for the losses, power should equal 30 divided by 100 kW. The experience of the developments of high power cw CO and carbon dioxide lasers shows that the least mass and overall dimensions as well as the best operation characteristics with the power level of 30 kW and more refer to gas-dynamic lasers (GDL) due to the following advantages: (1) direct transformation of the portion of thermal energy into the coherent IR radiation; (2) absence of high-power electric sources; (3) absence of additional ejectors; (4) relative easiness in maintenance; and (5) application of compact aircraft units and devices with completed service life. The purpose of this paper is to consider the possibility of the creation of mobile self-contained technological gas-dynamic carbon- dioxide laser (SCT GDL) on the basis of gas-turbine engine (GTE).
Characteristics of a noncomplete combustion-driven downstream-mixing CO2-GDL
Valerii K. Ikonnikov, Peter A. Yegoyantc, Alexander B. Bersh, et al.
The first experiment with a combustion-driven downstream-mixing carbon-dioxide-GDL using C4N2 and N2O with equivalence ratio about 2 has been developed. The small- signal gain of 2.1 m-1 is measured that is in accordance with specific power of 50 kW/kg. The instantaneous mixing model and parabolized Navier-Stokes equations are used to explain the experimental data.
Eurolaser activities and EU113 achievements in particular
Ian J. Spalding, A. Clucas, Andrei A. Ionin, et al.
Cooperative laser activities in Europe under the 'Eureka umbrella,' and their principle objectives, are summarized. The paper then discusses recent laser applications work within the Eureka EU113 CO EUROLASER Project using: a 1 kW laser at Heriot-Watt University, Edinburgh; a 3 - 4 kW (industrial prototype) Laser Ecosse laser (currently sited at TWI, Abington); and the high power laser facility at SBLT, Ekaterinburg. Finally, the potential for carbon laser processing is reviewed globally, in the light of experiments recently published by other workers.
State of development high-power cw CO laser for industrial applications
V. A. Belavin, G. M. Grigor'yan, Y. P. Koretsky
Brief review of the current progress of electric-discharge CO-lasers is given. Special attention is given to a cw CO-EDL with average and high output power (from several hundred watts up to several kilowatts) -- potential prototype of industrial lasers. A composition of a working gas mixture, characteristic of the electrical discharge, the constructional features of systems, etc., are considered. Problems of practical application of a CO-GDL are discussed.
Numerical modeling of power and spectral characteristics of subsonic discharge CO laser
Alexander P. Lavrov, Galina N. Volchkova, Tatjana A. Bungova
A numerical model of subsonic CO discharge laser is formulated. A system of two- dimensional narrow channel equations or one-dimensional gasdynamic equations is used. The peculiarities of the spatial distribution of gain for laser with longitudinal discharge are analyzed. The computations for various experimental installations are made. The recommendations concerning the modernization of these lasers are given. The lasers with line selecting on are analyzed.
YAG:Nd laser system with parallel connection of active elements and passive Q-switching
Anatoly N. Kravets, S. A. Kravets
The generation regimes and technological possibilities of YAG:Nd laser system with parallel connection of active elements is investigated. Passive Q-switching and synchronization of single-mode pulse-periodical radiation has been realized by the LiF:F2 crystal. The phase conjugating by the reflection dynamic hologram in LiF:F2 crystal is analyzed.
Nd:glass fiber-bundle laser for technological applications
L. I. Avakyants, B. M. Dobychin, Alexander V. Charikov, et al.
A free-running flashlamp-pumped Nd:glass fiber-bundle laser is investigated at high repetition rates. Water cooling of both the flashlamp and a pumped part of the bundle allowed us to obtain the average laser power of 25 W at 50 Hz without pulse energy reduction (on the order of 0.5 J). The unpumped parts of the bundle (up to 0.5 m) are intended for delivering laser energy to areas under processing. The benefits of this design for technological application are discussed.
Powerful pulse solid state laser based on potassium-gadolinium tungstate neodimium-doped crystals
Valerii S. Gulev, Sergey L. Mikerin, Vladimir D. Ugozhayev, et al.
The development and the investigation of generation of a powerful pulse solid-state slab laser based on potassium-gadolinium tungstate crystals with neodimium ions in unconventional resonator design realizing the mechanism of autocompensation for optical field distributions caused by an effect induced in powerful lasers active medium by pumping emission are reported. The operation efficiency of this mechanism on the pulse solid-state lasers with slab elements of rectangular cross-section is shown. A high lasing efficiency and high beam quality of the studied laser output radiation are demonstrated.
Chirped DFB gratings using bent waveguides to tailor specific laser properties
Bent waveguides are superimposed on homogeneous distributed feedback (DFB) grating fields to generate chirped DFB gratings. This efficient and high-resolution method enables the fabrication of arbitrarily axially chirped DFB gratings by appropriately bent waveguides which reveal differences between neighboring effective DFB pitches in the sub-interatomic range. The bending functions are generated by high-resolution lithography on a set of masks which can be frequently reused for a low-cost production process. The design principles are described defining specific unit cells which are reproduced as often as necessary to obtain a full coverage of the wafer. The method is demonstrated for semiconductor lasers including DFB gratings.
Beam shaping of phase-coupled array of waveguide lasers with binary phase plates
Guillaume Lescroart, R. Muller, Gilbert L. Bourdet
In this paper, we present theoretical and experimental results on the effects of binary phase plates on the far field diffraction pattern of in phase and out of phase coupled linear array of square waveguide lasers. Different configurations of Talbot cavity are compared in terms of power contained in the main lobe.
Defect-dominated 1.06-um laser-induced damage of antireflectance coatings designed for use at 1.3 um
The unique aspect of this work is that the defects found in an AR optical coating represent a degenerate ensemble that is uniformly distributed throughout the optical coating at high spatial densities. This ensures that various stages of damage may be observed for each irradiation and that the defect source can be identified.
Compensation of thermal effects in acousto-optic deflector
Vladimir I. Balakshy, Vitaly B. Voloshinov, Vladimir A. Karasev, et al.
Results on investigation of thermal effects which appear during operation of an acousto-optic deflector are presented in the paper. Influence of the effects on characteristics of the scanning device is evaluated. For a case of the tellurium dioxide deflector, it is proved that the most principal thermal effect consists in an undesirable spatial shift of a scanning optical beam. The shift leads to the optical beam positioning error which in a typical deflector may be of dozens of resolvable spots. A method of the thermal shifts compensation based on acoustic frequency tuning is proposed. For various regimes of the deflector operation, laws of the frequency tuning are found thus providing the compensation of the shifts with the required precision.
Numerical modeling of active media chemical composition dynamic change in sealed-off pulsed periodical TEA-CO2 lasers
Boris Aleksejevich Kozlov, D. I. Ponomaryov
Algorithms were researched and evaluated for the active media chemical composition dynamic change in sealed-off pulsed-periodical TEA-carbon-dioxide lasers. These algorithms include behavior of up to 64 charged and neutral compounds. Also reported are the results of simulation of the transition to a quasi-equilibrium state of basic neutral compounds (carbon- dioxide, CO, O, O2, O3, N2, N, NO, NO2, NO3, N2O) in carbon- dioxide-laser mixtures of atmosphere pressure at the volume discharge of energy density W equals 0.1 to 0.5 J*cm-3 excitation with the pulses repetition rate F equals 102 - 104 Hz.
Decomposition and regeneration of gas mixtures in CO2 longitudinal pulse discharge lasers
Boris Aleksejevich Kozlov, Vladimir I. Solovyov
The change of gas mixture chemical composition and output power of the carbon-dioxide longitudinal pulse laser was investigated in glass and ceramic discharge tubes at pulse repetition frequencies up to 10 kHz. O2 efficient absorption with ceramics was established. The influence of gas addition (H2) and solid state catalyst (Pd, CuO*MnO2) on chemical composition stabilization, output power and life-time of sealed-off carbon- dioxide laser was studied.
Time evolution of the electric characteristics of a laser discharge through their waveforms of the voltage and the current
Peter Persephonis, A. Ioannou, J. Parthenios, et al.
The time behavior of the electric characteristics resistances and inductances in the discharges in pulsed gas lasers is revealed through a procedure which exploits only the voltages or the currents waveforms. This can be achieved combining step by step the waveforms with the equations governing the performance of the system. This method is described analytically in the text. Its application showed that the resistances drop rapidly (first 10 nsec) from very high values to low values, while the inductances increase to high values and subsequently decrease, forming an abrupt high peak (first 40 nsec). The steep drop of the resistances is due to the electron avalanche multiplication, while the peak of the inductances is due to the centripetal magnetic forces (Laplace forces), which cause a temporary constriction of the plasma. In the 'main phase' of the discharge the resistances present a damping oscillation with the same frequency as the voltages, while the inductances present light fluctuations around constant values. The time varied resistances and inductances strongly influence the electrical and optical behavior of the laser system.
Matching of laser tube with impulse power supply
A. S. Arefyev, N. M. Vereschagin
Theoretical investigation was conducted for matching the laser tube and the power supply. Matching conditions are obtained. Matching arrangement is realized for nitrogen laser with voltage impulse of 160 kV and current impulse leading front duration of 40 ns. It is shown that efficiency and radiation power increase on increasing of the voltage rise rate at high frequency (above 600 Hz).
Laser Materials Processing: Manufacturing Systems, Physical Models, Technology
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Second generation laser manufacturing systems
Aldo V. La Rocca
Laser processing can show its full capacity in laser multiprocessing systems applications in which the laser is not hindered by the constraints imposed when the laser is inserted in conventional systems without reassessing the overall system design. In these cases the laser process performance up to now was kept at very low levels because conventional systems would not need or accept higher ones. Instead now said performance must be brought to the upper limits inasmuch as the lasers will be the pacesetter for the performance of the new systems freed from all the old design bondage. Hence the importance to get the maximum performance from each process singly and from their combinations. Better understanding and control of the fluidynamic effects becomes mandatory because of their paramount role on process energy efficiency and thus process productivity and more important yet quality, repeatability and transferability. At present one of the dedicated laser multiprocessing systems of greatest interest is the laser cut-weld of which several have made appearance on the market. Next to come are the 'augmented' laser multiprocessing obtained by combining the laser with conventional processes in a manner which takes advantages of unexpected synergies permitted by the laser. In this manner, the system is allowed to outperform, in all aspects from productivity to quality, the already much higher performance of dedicated all laser multi- processing system. One of the most important 'augmented' laser multiprocessing is the cut- bend-weld. It should be clear that these flexible multiprocessing machines tend to grow naturally in multistation cells and their aggregation in isles and complete manufacturing centers; i.e., the first viable realizations of computer integrated manufacturing.
Technological problems of pulse YAG laser integration in manufacturing sequences
E. G. Zaychikov, A. A. Gusev, Serguei V. Kayukov, et al.
The description of the two different technological processes including pulse laser welding developed at the SB FIAN is presented in this paper. The assembling of ball bearings with protective washers is one of them. The following mechanical methods are usually used for fastening: with the elastic stop ring and using sectioned washer. But the two methods require the presence of the special turning in an external ring and the external ring suffers a mechanical pressure, which can cause an unacceptable deformation of it.
Possible models of hydrodynamical nonstationary phenomena in the processes of laser beam deep penetration into materials
Vladimir S. Golubev
Some possible qualitative models of nonstationary hydrodynamical phenomena in the melt surrounding the 'key-hole' in processes of laser beam or hole punching are presented. Different mechanisms of excitation of such nonstationarities are discussed: thermocapillary, evaporative and 'wind' instabilities of the surface of the melt; a 'shelf' instability of melt layers subjected to the action of intense laser irradiation. Estimations of the laser beam intensity value I and processing velocity v, representing the limits of different mechanisms of instabilities, are presented. The ranges of these two parameters are: I equals 104 - 107 W/cm2; v equals 10-1 - 102 cm/s. These estimations give some preliminary ideas concerning the choice of (I,v) range, which enables it to provide the stability and quality of deep penetration laser materials processing.
Interaction of laser-induced quasi-stationary plasma flow with substrates
Vladimir N. Anisimov, Valeria G. Grishina, Oleg N. Derkach, et al.
The effects of interaction of quasi-stationary carbon plasma flow with a substrate have been studied using time-integrated and time-resolved emission spectroscopy and ion time-of-flight technique. Plasma flow with typical electron density of order of 1018 cm-3 and temperature of 5 eV was created with 5 ms pulses of TEA carbon-dioxide laser. Plasma- substrate interaction has been shown to result in significant variation of plasma parameters and plasma composition near the surface of the substrate.
Mathematical modeling of nonequilibrium heating and melting of Si by Nd-YAG laser radiation at 1.06 um
Vladimir I. Mazhukin, V. V. Nosov
The mathematical model of the nonequilibrium heating and the phase transformations in Si is considered induced by the nanosecond pulse laser irradiation at 1.06 micrometer. Taken into account are the complex dynamics of the radiation absorption, the electron-hole plasma development, the heat diffusion and the radiation transfer. The simulation results show the self-regenerative nature of the radiation absorption process as well as significant overheating of plasma and formation of overheated metastable region in solid phase.
Computational and experimental investigation of gas-assisted laser cutting of thick metal
N. K. Makashev, O. G. Buzykin, E. S. Asmolov
On the basis of the quantitative physical model of gas-assisted laser cutting of thick metal in air or oxygen the maximum cutting velocity and thickness are calculated. The effect of beam shape on cutting efficiency is considered. The theoretical results are in qualitative agreement with the experimental data at the carbon-dioxide-laser of 7...15 kW. It is shown that the cutting velocity can be increased substantially by means of beam shape and gas jet optimization.
Experimental investigation of the gas flow in gas-assisted laser cutting by means of geometrically similar models
N. K. Makashev, O. G. Buzykin, E. S. Asmolov
The gas flow in the system of nozzle-cut is investigated for the case of gas-assisted laser cutting of materials. The direct measurement of pressure fields is used with geometrically similar models which simulate the configuration forming during the laser cutting of metal sheet. The effect of geometric parameters of the system on the flow pattern in the kerf and on its features responsible for the cutting quality is analyzed. The choice and proper implementation of the assisting gas blowing to the cut front zone if of great importance for the gas-assisted laser cutting. There exist many various methods and facilities for the gas delivery. Nozzle configurations of many kinds and the peculiarities of free jet streams formed by them was the subject of extensive exploration. The efficiency of the nozzle under investigation was evaluated empirically or by the pressure exerted to the flat plate in the stagnation point of normally impinging jet. Recently the attention of investigators has been redirected to the details of the gas flow in the cut kerf. This activity is connected with the development of the theoretical models of gas-assisted laser cutting which serves to appreciate the role of the gas flow parameters in the phenomena responsible for the cutting efficiency. The efficiency of the gas delivery which is characterized by the cutting speed, the maximum thickness of the cut material, or the quality parameters of cut edges depends mainly on the flow features in the cut kerf. In the present paper these features are discussed closely. The results of the investigation provide the ability to choose purposefully the geometrical parameters of the nozzle facilities for laser cutter.
Determination of critical characteristics of gas jet under finishing laser cutting
Ch. Sipavichyus, P. Vaitiekunas, E. Milutis
In the calculations the method of finite volumes with program packet PHOENICS 1.4 was applied. Elliptical transfer equations with standard model of turbulence were numerically solved. Three cases of flow around flat obstacle were investigated. Comparison of evaluated flow rate, pressure and turbulence energy when flowing around the plate with or without a hole was done. Highest possible values of flow rate on the symmetry axis of the system in the case of continuous hole in the obstacle were estimated. Activity of the jet in the cross-sections of nozzle outlet-obstacle and in the periphery above obstacle surface was proven. Analysis of obtained results shows the activity of introduced investigation and abilities to employ its results in projecting of conic nozzles.
Determination of critical characteristics of gas jet under high-quality laser cutting: experimental investigations
Ch. Sipavichyus, R. Chlezhas, P. Vaitiekunas, et al.
Results of investigations on gas jet structure and selection of the optimal nozzle configuration are presented. Free flow from the nozzle and the flat obstacle overflowing were considered. The optimal distance h from the nozzle to the obstacle was determined. The optimal flow rate and gas pressure in the nozzle outlet and in the area in front of the obstacle were found. The flow rate distribution in different cross-sections is presented. Experimental results were employed in the formation of a mathematical model.
Condensation in the laminar-free jet of vapor flowing into a cool gas
Alexey G. Gnedovets, Andrey V. Gusarov, A. Uglov
Laser beam treatment of the surface leads to vaporization. Cooling of the vapor by the surrounded gas results in condensation and the ultrafine particles creation. To make clear conditions of the particles formation, a two-phase hydrodynamic flow of the erosion torch was simulated. A case of the free laminar vapor jet inside the inert gas atmosphere was investigated. The particles are founded to create inside a thin layer -- the condensation front. The particle dimension is proportional to the second power of the ambient gas pressure.
Investigation of hole punching in glass by harmonically modulated beam of industrial CO2 laser
Vladimir S. Golubev, Oleg Alexeyevic Novodvorsky, Rafael Ya. Sagdeev
An investigation into the process of hole formation in 1 to 5 mm thick silicate glass has been undertaken with radiation of the continuous-wave carbon-dioxide-laser operated in pulse- periodical regime. Punching velocity, time of hole formation and heat-affected zone have been determined in accordance with sample thickness, beam and gas flow parameters.
Application of a high-power CO laser in aluminum welding
A multi-kW CO laser system with nearly diffraction limited beam quality has been developed. The performance data are presented. Experiments in laser welding of the aluminum alloy AlMgSil (6082) has been carried out using the CO laser and a commercial industrial carbon- dioxide laser. The welding performance of both laser systems has been compared with results of Nd-YAG laser welding from literature. It has been shown that the penetration depths with the CO laser are higher compared with the results of carbon-dioxide and Nd-YAG laser at the same power level. This is on the one hand a consequence of the better beam quality of the CO laser compared to the Nd-YAG laser and on the other hand the shorter 5 to 5.6 micrometer wavelength compared to the carbon-dioxide laser resulting in a reduced beam-plasma interaction. Owing to the shorter wavelength of the CO laser the absorption of the radiation by laser induced plasma -- one major problem in deep penetration welding with lasers -- is drastically reduced. The aluminum weld seams obtained with the CO laser are very homogeneous and regular at the surface in contrast to the weld seams obtained with the carbon-dioxide laser. The process parameters in CO laser aluminum welding can be changed in a wide range. This is not possible using the carbon-dioxide laser because of the low threshold intensity for a shielding plasma.
Concepts for advanced aluminum welding adaptation techniques for the chemical oxygen iodine laser (coil)
This paper describes and develops the concept of adapting the chemical oxygen iodine laser (COIL) system for aluminum welding. The suitability of the COIL for welding aluminum or Al-SiX alloys, such as A40 is evaluated using current welding material processing techniques. The problem of high thermal conductivity coupled with the high reflectivity of aluminum, which makes it difficult to laser weld, is addressed by proposing the use of a mathematical model for laser welding. The model should predict the size of a laser weld to the net heat absorbed by the workpiece. Thus, the problem of excessive heat flow to components is addressed. The possibility of utilizing the high output power of the COIL by applying 'binary optics' technology to convert the high power and high quality Gaussian output of the main beam into a set of high quality Gaussian sub-beams which will be transported via fiber optics delivery to the sample surface(s) is also discussed. The COIL is a viable source for future satellite construction which requires hermetic sealing of components and instrumentation.
Tribotechnical efficiency of journal-bearing connection of crankshaft renewed by laser built-up welding
I. A. Vishnevetskaya, V. A. Denisov, A. V. Solovyov
The comparative accelerated tests were realized. The break- and wear-resistance of journal- bearing connection was obtained. Crankshaft journals were renewed by the laser built-up welding with self-fluxing Cr-B-Ni-Si powder of the different composition. Available data were analogous to the characteristics of the new connection. The rising of the coating hardness doesn't lead to the improvement of the performances.
Multifactor approach to analysis of the process of tool laser hardening with taking into account regimes of its operation
S. I. Jaresko, Serguei V. Kayukov, M. S. Nerubai
To increase an efficiency of the hardening laser treatment of the cutting tools it was proposed to conduct the complex investigation of influence of the irradiation regimes and conditions of a cutter operation on the tools wear resistance. The linear and non-linear effects having an influence on the wear of the irradiated cutters of the greatest degree were chosen by method of chance balance and its qualitative and quantitative estimation was carried out. Considerable influence of the nonlinear effects of analyzed factors interactions on the wear resistance of hardened cutters was revealed. The necessity of the tools irradiation regimes determined according to the conditions of their operation was confirmed.
Physics and technique fundamentals of laser chemical hardening of the machine elements and metal cutting tools
G. I. Brover, V. N. Waravka, V. N. Pustowoit, et al.
The results of the experimental investigations of microstructures and properties of various materials subjected to the laser chemical heat treatment are presented. Optimization criteria of the laser radiation modes and conditions and also the chemical compositions of the coatings received by means of electrical-spark alloying, ion-plasma spraying, chemical deposition and dross cladding for the purpose of producing composite material having the prescribed service properties on the working surfaces edges of workpieces have been determined.
Oxidation of titanium films irradiated with weak photon beam in the course of thermal treatment
I. S. Nupriyonok, A. M. Chaplanov, A. N. Shibko
Peculiarities of phase transformations occurring in titanium film under annealing accompanied by irradiation with weak photon beam are discussed. It is shown that oxidation kinetics and phase composition of the film are dependent on the energy of light quanta irradiating the film in the course of stationary annealing.
Laser treatment of vanadium silicon system in alkanes
E. N. Gerasimchik, A. M. Chaplanov, A. N. Shibko
Peculiarities of phase transformations occurring in a vanadium-silicon system under pulsed laser treatment in carbon-containing liquids are discussed. Changes in electrophysical parameters of vanadium-silicon contact are studied as a function of irradiation conditions.
Investigation of possiblity of substitution of 12XH3A steel in the process of manufacturing gears for a Sova motorcycle gearing box
L. M. Abramov, V. P. Karabanov, V. L. Abramov, et al.
The experimental work describes the possibility of substituting the expensive alloying steel 12XH3A for the low-cost material (steel 40X) in manufacturing gears of the motor cycle gearing box. It ban be achieved on the basis of the obtained results and with the help of laser melting treatment of small-alloying steel. We can speak about the dependence of laser melting radiation efficiency on the regimes and procedures. The breakage of the gearing box of the motor cycle 'Sova' may be explained by the low carry ability of its first gearing box gear. This investigation includes the determination of the cause of this problem. One of the most wide spread methods of such decisions is the substitution of the used materials by another. The most important criteria for the new materials are: (1) the increase of mechanical characteristics (solidity, plasticity); (2) the increase of such characteristics as hardness, specific percussive viscosity; (3) the improvement of the technological characteristics; (4) the condencention of the manufacturing expenditures (economical effect). In accordance with these creations some materials (35X, 40X, 20XH, 40XHM steels) were chosen. The best material is 40X steel, because it allows us to treat the gears by laser radiation with the surface melt. Surface melt allows us to produce: (1) martensite structure with high solidity and low percussive viscosity; (2) martensite structure with chrome carbides and high percussive viscosity, but low plasticity; (3) amorphous or monocrystallic structures with the best characteristics. The last structure has the best characteristics because dislocation defects in such material are practically absent. Also, the amorphous surface of the materials is the most interesting. The spirit of the investigation is to define the parameters of production such as radiation power, size of laser spot, and speed of spot.
Model of the chemical combinations forming by the laser alloying of metals
V. S. Postnikov
This work presents the model of chemical combinations of carbide or boride type which are formed in the melt by laser alloying of metals. The idea of spherical reactionary volume of liquid phase was used by construction of this model. The concentration of the initial components in this volume is replenished by means of the movement of the substance across the surface of this volume. The two mechanisms of this movement are considered: diffusion and convection. The basic equations of this model are formulated that allow us to correlate the sizes of the chemical combination particles with the basic physical properties of the initial phases and of the reaction products.
Surface layer structure of Cr-Mo-steel after laser chromium-boron-carbiding
V. S. Postnikov, S. A. Belova
This paper contains the results of structure investigations of laser layers on the Cr-Mo-steels surface by laser chromium-boron-carbiding. The positive influence of heating by the following heat treatment on the microfirmness and microfragility of the alloyed layer was shown. By x- ray analysis the mechanisms were determined of firmness and fragility lowering in laser layer by heating. The analysis of the fine structure of the laser layer confirms the supposition about the high thermal stability of the structure which is formed by laser alloying.
Investigation of surface topography after melting by laser beam
V. S. Avanesov, M. A. Zuev
Experimental and theoretical investigations of surface microrelief of steels with various carbon contents were carried out after melting by continuous carbon-dioxide-laser radiation. The model advanced to describe the microrelief formation has shown the coincidence with experimental data. Some technical measures for decreasing the roughness after laser melting by moving beam were pointed out.
Use of laser treatment to obtain high-physical properties of the upper layers of normalized grade 40 steel
Efim I. Tesker, Vladimir A. Guryev
Laser treatment effects on the surface properties of normalized steel 40 grade have been studied. Kinetic features have been established as well as the microstructure-generating mechanism in an intercritical temperature range. Optimum characteristics of laser treatment process have been found, that are to ensure optimum surface properties of the specimen. The test results confirm the high effectiveness of laser treatment and the possibility of obtaining pre-determined properties in the upper layers of the specimens.
Laser treatment of polymer-coated steel components
Viktor V. Chapurkin, Efim I. Tesker, N. Aseev, et al.
Some results of the studies of laser treatment on microstructure and properties of fluorine- siloxan film coating are represented. Original test procedures were developed to study coating properties and microstructure. The optimum laser treatment conditions have been established for film coatings, which opens up new perspectives for higher technical level and a rise in the service life of friction assemblies.
Laser boron-carbiding of Ti-alloy
V. S. Postnikov, M. N. Tagirov
The peculiarities of structure surface layer forming of Ti-alloy by laser alloying by B, C and Cr are presented in this work. The surface layer by the laser alloying consists of great quantity of small particles of borides, carbides and intermetallides which raise the hardness of the surface to 9500 - 11500 MPa. The antifriction properties investigation shows that the wear of Ti-alloy surface is reduced after the laser alloying. The addition of solid oiling into the alloying composition allows us to reduce the coefficient of friction to the sizes that correspond to the coefficient of friction of the traditional anti-friction materials.
Laser treatment of electrical steels and other magnetic materials
B. K. Sokolov, V. V. Gubernatorov
Different techniques for reducing magnetic losses of grain-oriented silicon steel by laser irradiation have been examined. The explanation for the effects is given. The significant decrease in magnetic losses was found after a local laser treatment of an ultrathin strip of fine- grained anisotropic electrical steel. Magnetic loss in amorphous ribbons was found to be essentially reduced to 30% by local laser treatment in a wide range of magnetizing reversal frequencies. A special laser system for realization of local irradiation techniques is considered.
Metal surface defect formation arising by the laser heating
L. Ya. Min'ko, Yuri A. Chivel
Appearance on the surface of metals of microcraters, microparticles, and continuity breaks with characteristics sizes 1 - 10 micrometer was experimentally observed under the action of laser monopulses of duration 40 ns and 300 ns. The model of initial destruction of materials and generation of condensed particles based on exclusively thermal action of laser radiation and natural inhomogeneity of solids is developed.
Laser Applications: Rapid Object Manufacturing, Diagnostics, Measurement Systems
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Rapid objects manufacturing from liquid photosensitive compounds induced by pulsed and cw laser beams
Alexander V. Evseev, Sergey Valentinov Kamayev, Michael A. Markov, et al.
The results of layer-by-layer objects manufacturing from liquid acrylic oligomers by pulsed- periodic excimer XeCl-laser beam (lambda equals 308 nm) and cw He-Cd laser beam are presented. Productivity and power consumption of the layer-by-layer manufacturing by laser beam photo-initiated oligomer polymerization were evaluated. Samples with an overall volume of 1000 cm3 were fabricated by projection printing method (XeCl-laser) and by direct laser drawing (He-Cd laser), and it was shown that the laser beam energy consumption during the objects manufacturing with layers thickness h of 0.1 - 0.2 mm had not exceeded 1 - 2 J(DOT)cm-3. Schemes of the laser stereolithography plants based upon the excimer laser and the cw UV lasers are considered, and their productivity evaluations are presented.
Determination of kinetic rate constants by pulsed laser polymerization
Alexander V. Evseev, A. N. Nikitin
The analytical expressions have been derived to calculate molecular weight distributions (MWDs) for a polymerization scheme that contains reactions of chain initiation, propagation and termination by recombination or disproportionation under polymerization initiation by arbitrary sequence of radiation pulses. These expressions can be applied to study MWD on initiation of polymerization both by arbitrary-duration pulses and by cw beam. MWDs calculated for methylmethacrylate polymerization by pulses sequence with different energy density are presented. Simple relations are derived for determination of chain termination constant kt from chains number distributions.
Laser systems for laminated objects manufacturing
Vadim P. Veiko, V. A. Chujko, Dmitry L. Goobanov, et al.
Various schemes of laser systems and optical aspects of 3D-synthesis are analyzed. Advantages of laminated objects manufacturing process are presented. Main characteristics of laser synthesizers CARAT-200 and CARAT-400 are presented.
Computer-aided laser-optoelectronic OPTEL 3D measurement systems of complex shaped object geometry
Ravil M. Galiulin, Rishat M. Galiulin, J. M. Bakirov, et al.
Technical characteristics, advantages and applications of automated optoelectronic measuring systems designed at the Regional Interuniversity Optoelectronic Systems Laboratory ('OPTEL') of Ufa State Aviation Technical University are given. The suggested range of systems is the result of the long-term scientific and research experiments, work on design and introduction work. The system can be applied in industrial development and research, in the field of high precision measurement of geometrical parameters in aerospace, robotic, etc., where non-contact and fast measurements of complicated shape objects made of various materials including brittle and plastic articles are required.
Research of physical-chemical processes in optically transparent materials during coloring points formation by volumetric-graphical laser processing
Nicolay N. Davidov, L. T. Sushkova, M. V. Rufitskii, et al.
A distinctive feature of glass is a wide range of correlation between internal absorption and admittance of electro-magnetic streams in a wide wavelength scope starting from gamma rays and up to infrared radiation. This factor provides an opportunity for search of new realizations of processes for machining, control and exploitation of glassware for home appliances, radioelectronics and illumination.
Novel noncontact method of surface acoustic waves registration for nondestructive testing
Alexander A. Karabutov, Alexander P. Kubyshkin, Ye. V. Savateyeva
A novel method of fully noncontact excitation and registration of surface acoustic waves (SAW) in constructional materials has been suggested and theoretically substantiated. It is based upon laser-induced excitation of SAW pulse and registration of thermal response that accompanies dilatation in the acoustic wave. The method is especially convenient for the samples under elevated temperatures.
Thermal wave characterization of coatings on substrate
Alexander A. Karabutov, V. V. Klevitskiy, Alexander P. Kubyshkin
The problem of determining coating thickness and thermophysical characteristics using photothermal IR-radiometry is investigated theoretically and experimentally. The information about coating characteristics is contained in frequency dependence of surface temperature oscillation amplitude and phase. The optimization of thermal wave excitation modes (continuous wave and transient) has been done for different coating parameters. In experiments the characteristics of ceramic coatings on metal substrates were determined as well as their changes under technological processes.
Nondestructive material characterization by laser-excited longitudinal and shear acoustic waves
Alexander A. Karabutov, Natalia B. Podymova
Wideband pulsed acoustic spectroscopy over a frequency range 1 - 100 MHz with laser excitation of ultrasound was carried out for metals, ceramics and glass-fiber-reinforced composites. Sizes of grains in metals and ceramics were evaluated and the scatterers size distribution can be estimated. Quality of treatment of metal samples surfaces was evaluated using frequency spectra of attenuation of ultrasound. Fatigue changes in composites arise after loading transform ultrasound attenuation spectra. Measurement of attenuation of shear acoustic waves in metals was carried out using transformation of longitudinal waves at sample surface. The attenuation of shear waves was reasonably stronger than the attenuation of longitudinal waves in the short wavelength region.
Compact Doppler velocimetry system on the basis of injection laser diode
A. V. Marugin, V. B. Tzaregradsky
The laser Doppler velocimetry measuring system on the basis of injection semiconductor cw laser has been investigated. The system is capable of analyzing the local velocity distribution of moving object in the range 1 mm/s - 5 m/s with the sensitivity threshold up to 0.1 nW and signal-to-noise ratio 30 - 40 dB for solid targets and 5 - 15 dB for dense aerosol flows.
Wavefront sensor with an unharmonic grating
Alexander F. Naumov, Nicholas N. Losevsky, Valentin N. Belopukhov, et al.
A new type of wave front sensor is proposed. The possibility of the measuring sensitivity control is shown. The results of the numerical simulation and experiments of the wave front aberrations measurements are presented.
Diagnostics of lens-like media with small-scale inhomogeneities by method of probing beam intensity moments
The use of Gaussian probing beams for measuring parameters of distributed lenses is well known. But common methods become invalid in widespread cases when investigated media contain additive scattering inhomogeneities. This report is devoted to the usual scheme generalization able to overcome mentioned restrictions. It is shown that utilizing arbitrary paraxial probing beams, characterized by space-angle intensity moments, enables us to solve this task effectively. The equations for evolution of moments in lens-like media with small- scale stochastic inhomogeneity are derived and analyzed, on which basis some recommendations are made for fast and suitable measurement of medium parameters.
Laser beams with helical wavefront dislocations and their applications in the diagnostical and metrological systems
Tatiana I. Arsenyan, Nikolai N. Fedotov, L. S. Kornienko, et al.
Properties and practical applications of the light beams with helical dislocations (HD) of wavefront in metrological systems are considered on the basis of experiments with gas lasers and numerical ones. It is shown, that the super stable lasers-heterodynes with high quality of out coming radiation can be created using lasers with inner-resonator helical fields. Conditions of HD appearance in laser beams propagating through the turbulent atmosphere are determined. A method of definition of atmospheric turbulence degree based on HD number counting is suggested. The possibility of such beams application in metrological optical systems having super Raleigh spatial resolution is considered as a promising direction of their usage.
Technological system for control of bearing ring runway surface
Valentin N. Belopukhov, Vjacheslav N. Podvigin, Vladimir G. Volostnikov, et al.
It is regarded as a system intended for automatization of quality check-up operations of a runway surface of a bearing internal ring for the purpose of search for microdefects, deviation form defects, and as a sorter of bearings. The system contains a laser device for noncontact diagnostic and electronics tools.
Form measurement sensor for rotation reflecting surfaces
Valentin N. Belopukhov, O. A. Zajakin, Vjacheslav N. Podvigin, et al.
It is considered the sensor which can measure a surface profile shape and a waviness as the space function. The optical head registering the local surface titles is applied in the sensor. The sensor is the adaptive action system. The device is classified as a coordinate-measurement tool.
Analysis of accuracy characteristics of laser meters for monitoring of geometrical dimensions
V. I. Shlychkov
The geometrical dimension laser meters patterned in accordance with triangulation scheme were used under development of the rolled product thickness meter and geometrical dimension monitoring device of the railway wheels. When used in such devices, the special feature of application of the laser meter lay in the inclinations of the monitoring object surface, when moving at designated range of angles plus or minus psi0. The quantitative evaluation of the measurement error geometrical component is necessary in evaluating the accuracy characteristics of the meter as a whole. For example, the measurement error of the rolled products thickness meter which has a linear field of vision may not exceed 12 mm (epsilon less than or equal to 20 micrometer). The measurement error of the railway wheels geometrical dimensions meter having the field of vision 2y approximately equal to 60 mm for each measurement channel may not exceed 300 micrometers (epsilon less than or equal to 300 micrometer).
Study of aerosol pollutants spreading by lidar and computer experiments
Serguei M. Pershin, Oleg B. Butusov
The possibility of combined utilization of computer modeling and a compact aerosol backscatter lidar in an ecomonitoring system has been studied. The special statistical trajectory model that accounts for the effects of interactions between air flows and city buildings was created. The model is handy for its parameterization by lidar sounding data. For simulation of interactions between aerosol currents and buildings or other obstacles special forms of averaged wind velocity approximations were used. The model had been tuned by means of both literature and lidar data on aerosol plume dispersion over buildings and other obstacles. The method may be applied to the city ecomonitoring systems or to the regional ecomonitoring of complex terrains. The model is useful for calculations of year averaged aerosol pollution zone configurations. The development was utilized for ecological investigations in the Perovskii district of Moscow and around Karabash copper smelter in South Ural (Russia).
Laser infrared spectroscopy system for water vapor concentration control
V. N. Korolyov, A. V. Marugin
The effective schemes of near-infrared high-sensitivity spectrometer on the basis of injection laser and the thermal light source have been designed and investigated. On the example of water vapor concentration analysis it has shown that the volume concentration of 10-6 for gases and their admixtures in atmosphere may be registered by this laser system. The advantages and specifics of considered methods for various practical applications have been discussed.
Heterodyne diagnostics by Doppler signal of backscattering of near-surface flows induced by intense laser radiation
E. M. Chastookhin, V. D. Dubrov, Vyacheslav M. Gordienko, et al.
A procedure of operational inspection of laser technological processes has been suggested that is based on measuring spectral properties of Doppler signal of backscattering from the interaction region by optical heterodyne technique. The technique enables us to obtain the qualitative and quantitative information on hydrodynamic flows in reactor. The measurements have been performed with about 1 kW/cm2 beam intensity of continuous-wave carbon- dioxide laser at the surface of a number of condensed substances by monostatic scheme of interaction.
Thin-plates test with modified IT-200 Fizeau interferometer
Alexis V. Kudryashov, Vadim V. Samarkin, A. A. Lukashev, et al.
The results of the test of the flatness and wedge of thin quartz plates with the help of a modified interferometer Fizeau are presented. The suggested scheme of the interferometer allows us to get and process two interferograms without any adjustment of the tested element. The accuracy of the suggested methods is not less than lambda/10 (lambda equals 0.6 micron).