scholarly journals Interaction of laser radiation with the material during production powders and fibers

2021 ◽  
pp. 114-123
Author(s):  
Y. D. Chernichenko ◽  
M. N. Vereschagin ◽  
S. N. Tselueva ◽  
M. Yu. Tseluev
Keyword(s):  
Laser Radiation ◽  
Time Moment ◽  
Rate Of Change ◽  
Temperature Fields ◽  
Specific Power ◽  
Physical Parameters ◽  
Heated Plate ◽  
Significant Heterogeneity ◽  
Laser Radiation Pulse ◽  
Plasma State

The effect of laser radiation on a solid body leads to a change in the temperature field of the processed substance. The nature of heating, which is determined by the rate of change in temperature and temperature gradients, is different depending on the properties of the processed material and processing conditions.The main physical parameters of the process of laser processing of solids are the specific power of the absorbed laser stream 104–109 W/cm2 and the interaction time of the metal with the beam – 10–5–10–8 s. When such radiation pulses interact with the surface, an instantaneous explosive melting of a part of the material occurs and the substance surrounding the surface is transferred to the plasma state. The subsequent expansion of the plasma is accompanied by the appearance of a shock wave with a peak pressure of 1–10 GPa, which acts on the material, and the metal is dispersed.The mathematical problem of heating and melting a cylindrical plate with a laser light flux that normally affects its surface is solved. this problem is described by a system of thermal conductivity equations in three sections of the heated plate, which are characterized by the time factor of the laser radiation effect on the substance 1) 0 ≤ t ≤ tm; 2) t > tm; 3) tm < t ≤ th  (here tm, th is the time moment corresponding to the beginning of the formation of the liquid phase and the end of the melting of the plate, respectively).The calculated dependences of changes in the surface temperature of metal alloys X18N10T, X15N60 during the action of a laser radiation pulse with a duration of τ=5 ms are presented. The presence of a phase transition associated with metal melting (an inflection in the curves) leads to a temporary decrease in the rate of temperature growth. The distribution of temperature fields causes a significant heterogeneity in the distribution of temperature over the thickness of materials, which reaches 2000 °C or more depending on the thickness of the metal and the conditions of exposure. The temperature curves of the surface heating repeat the shape of the pulse, and the temperature of the rest of the metal has a nonlinear tendency to increase with the output to the asymptote.It is established that the process of explosive metal sputtering requires heating the volume of the material above the melting point at a thickness of 300–350 microns and an impact energy of 7–8 J. Reducing the level of energy impact to 5–6 J and increasing the thickness of the workpiece more than 500 microns does not provide the distribution of temperature fields required for the implementation of the spraying process.

Thermo-Solutal Convection of a Nanofluid Utilizing Fourier’s-Type Compass Conditions

2020 ◽  
Vol 9 (4) ◽  
pp. 362-374
Author(s):  
J. C. Umavathi ◽  
Ali J. Chamkha
Keyword(s):  
Brownian Motion ◽  
Prandtl Number ◽  
Boundary Conditions ◽  
Volume Fraction ◽  
Temperature Fields ◽  
Physical Parameters ◽  
Surface Boundary ◽  
Perturbation Scheme ◽  
Runge Kutta ◽  
The Impact

Nanotechnology has infiltrated into duct design in parallel with many other fields of mechanical, medical and energy engineering. Motivated by the excellent potential of nanofluids, a subset of materials engineered at the nanoscale, in the present work, a new mathematical model is developed for natural convection in a vertical duct containing nanofluid. Numerical scrutiny for the double-diffusive free and forced convection within a duct encumbered with nanofluid is performed. Buongiorno’s model is deployed to define the nanofluid. Robin boundary conditions are used to define the surface boundary conditions. Thermal and concentration equations envisage the viscous, Brownian motion, thermosphores of the nanofluid, Soret and Dufour effects. Using the Boussi-nesq approximation the solutal buoyancy effect as a result of gradients in concentration are incorporated. The conservation equations which are nonlinear are numerically estimated using fourth order Runge-Kutta methodology and analytically ratifying regular perturbation scheme. The mass, heat, nanoparticle concentration and species concentration fields on eight dimensionless physical parameters such as thermal and mass Grashof numbers, Brownian motion parameter, thermal parameter, Prandtl number, Eckert number, Schmidt parameter, and Soret parameter are calculated. The impact of these parameters are outlined pictorially. The velocity and temperature fields are boosted with the thermal Grashof number. The Soret and the Schemidt parameters reduces the nanoparticle volume fraction but it heightens the momentum, temperature and concentration. At the cold wall thermal and concentration Grashof numbers reduces the Nusselt values but they increase the Nusselt values at the hot wall. The reversal consequence was attained at the hot plate. The perturbation and Runge-Kutta solutions are equal in the nonappearance of Prandtl number. The (E. Zanchini, Int. J. Heat Mass Transfer 41, 3949 (1998)). results are restored for the regular fluid. The heat transfer rate is high for nanofluid when matched with regular fluid.

Measurement of laser radiation pulse length

1978 ◽  
Vol 21 (7) ◽  
pp. 955-956
Author(s):  
I. Ya. Khaskin ◽  
V. G. Medresh ◽  
I. N. Yundenko
Keyword(s):  
Laser Radiation ◽  
Pulse Length ◽  
Radiation Pulse ◽  
Laser Radiation Pulse

THE EFFECTS OF ENDOSCOPE AND HEAT TRANSFER ON THE PERISTALTIC FLOW OF A SECOND GRADE FLUID IN AN INCLINED TUBE

2016 ◽  
Vol 16 (04) ◽  
pp. 1650057 ◽  
Author(s):  
K. RAMESH ◽  
M. DEVAKAR
Keyword(s):  
Heat Transfer ◽  
Vertical Tube ◽  
Peristaltic Flow ◽  
Temperature Fields ◽  
Second Grade ◽  
Physical Parameters ◽  
Second Grade Fluid ◽  
Pumping Rate ◽  
Inclined Tube ◽  
Grade Fluid

In the present paper, we have studied the effects of endoscope and heat transfer on the peristaltic flow of second grade fluid through an inclined tube. The endoscope is a solid circular cylinder which is inserted in a peristaltic tube, and the flow takes place through the gap between endoscope and the peristaltic tube. The endoscope is maintained at a temperature [Formula: see text], while the outer tube has a sinusoidal wave traveling down its wall and is exposed to temperature [Formula: see text]. The flow is investigated in a wave frame of reference moving with the velocity of the wave. The equations governing the flow of second grade fluid are modeled in cylindrical coordinates. Using perturbation method, the solutions are obtained for the stream function, pressure gradient and temperature fields. The pressure difference and frictional force at both the walls are calculated using numerical integration. The graphical results are presented to interpret the effect of various physical parameters of interest. It is found that, velocity increases with an increase in inclination angle and the best pumping rate appear in the vertical tube as compared to the horizontal tube. It is also found that, the heat generation parameter has an increasing effect on the velocity of the fluid.

Characterization of Rotating Gantry Micro-CT Configuration for theIn VivoEvaluation of Murine Trabecular Bone

2013 ◽  
Vol 19 (4) ◽  
pp. 907-913 ◽  
Author(s):  
Luke Arentsen ◽  
Susanta Hui
Keyword(s):  
Trabecular Bone ◽  
Signal To Noise Ratio ◽  
Hounsfield Unit ◽  
Rate Of Change ◽  
Physical Parameters ◽  
Micro Ct ◽  
Detector Geometry ◽  
Ct System ◽  
Filter Thickness

AbstractThe objective of this study is to determine the optimal physical parameters of a rotating gantry micro-CT system to assessin vivochanges to the trabecular bone of mice. Magnification, binning, peak kilovoltage, beam filtration, and tissue thickness are examined on a commercially available micro-CT system. The X-ray source and detector geometry provides 1.3×, 1.8×, or 3.3× magnification. Binning is examined from no binning to 2 to 4. Energy is varied from 40 to 80 kVp in 10 kVp increments and filter thickness is increased from no filtration to 1.5 mmAl in 0.5 mmAl increments. Mice are imaged at different magnifications and binning combinations to evaluate changes to image quality and microstructure estimation. Increasing magnification from 1.3× to 3.3× and lowering binning from 4 to 1 varies the spatial resolution from 2.5 to 11.8 lp/mm. Increasing the beam energy or filtration thickness decreases Hounsfield unit (HU) estimation, with a maximum rate of change being −286 HU/kVp for 80 kVp. Images for murine trabecular bone are blurred at effective pixel sizes above 60 μm. By comparing resolution, signal-to-noise ratio, and radiation dose, we find that a 3.3× magnification, binning of 2.80 kVp beam with a 0.5 mmAl filter comprises the optimal parameters to evaluate murine trabecular bone for this rotating gantry micro-CT.

Radiative Flow of Jeffrey Fluid Through a Convectively Heated Stretching Cylinder

2014 ◽  
Vol 31 (1) ◽  
pp. 69-78 ◽  
Author(s):  
T. Hayat ◽  
S. Asad ◽  
A. Alsaedi ◽  
F. E. Alsaadi
Keyword(s):  
Differential Equations ◽  
Nonlinear Partial Differential Equations ◽  
Convective Boundary Condition ◽  
Deborah Number ◽  
Temperature Fields ◽  
Jeffrey Fluid ◽  
Physical Parameters ◽  
Stretching Cylinder ◽  
Series Solutions ◽  
Convective Boundary

AbstractTwo-dimensional flow of Jeffrey fluid by an inclined stretching cylinder with convective boundary condition is studied. In addition the combined effects of thermal radiation and viscous dissipation are taken into consideration. The developed nonlinear partial differential equations are reduced into the ordinary differential equations by suitable transformations. The governing equations are solved for the series solutions. The convergence of the series solutions for velocity and temperature fields is carefully analyzed. The effects of various physical parameters such as ratio of relaxation to retardation times, Deborah number, radiation parameter, Biot number, curvature parameter, local Grashof number, Prandtl number, Eckert number and angle of inclination are examined through graphical and numerical results of the velocity and temperature distributions.

scholarly journals Hydromagnetic Stagnation-Point Flow towards a Radially Stretching Convectively Heated Disk

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
S. Shateyi ◽  
O. D. Makinde
Keyword(s):  
Stagnation Point ◽  
Numerical Solutions ◽  
Relaxation Method ◽  
Disk Surface ◽  
Stagnation Point Flow ◽  
Temperature Fields ◽  
Physical Parameters ◽  
Local Skin ◽  
Spectral Relaxation Method ◽  
Spectral Relaxation

The steady stagnation-point flow and heat transfer of an electrically conducted incompressible viscous fluid are extended to the case where the disk surface is convectively heated and radially stretching. The fluid is subjected to an external uniform magnetic field perpendicular to the plane of the disk. The governing momentum and energy balance equations give rise to nonlinear boundary value problem. Using a spectral relaxation method with a Chebyshev spectral collocation method, the numerical solutions are obtained over the entire range of the physical parameters. Emphasis has been laid to study the effects of viscous dissipation and Joule heating on the thermal boundary layer. Pertinent results on the effects of various thermophysical parameters on the velocity and temperature fields as well as local skin friction and local Nusselt number are discussed in detail and shown graphically and/or in tabular form.

scholarly journals Features of measurements the IR radiation power of a laser diode used in active optoelectronic systems for studying flows

2021 ◽  
Vol 2127 (1) ◽  
pp. 012047
Author(s):  
V V Bliznyuk ◽  
V A Parshin ◽  
N S Savinov ◽  
A A Selivanov ◽  
A E Tarasov
Keyword(s):  
Laser Radiation ◽  
Heat Flow ◽  
Radiation Power ◽  
Laser Diodes ◽  
Physical Parameters ◽  
Electronic Systems ◽  
Ir Radiation ◽  
Controlled Source ◽  
Ir Laser ◽  
Thermal Physical Parameters

Abstract In active optical-electronic systems for stream research that regulate thermal-physical parameters of diagnosed stream volume, the controlled source of the heat flow can be acquired by radiation of high-power IR laser diodes into the void. In the current work the peculiarities of measurement of this radiation are considered, specified by its strong divergence. It is shown that the measurements can involve laser wattmeters IMO-4M with planar thermoelectric primary measuring transformers of the laser radiation with a flat receiving site provided.

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