Modeling of Titanium Oxide Layer Growth Produced by Fiber Laser Beam

2013 ◽  
Vol 336 ◽  
pp. 11-18 ◽  
Author(s):  
Farida Hamadi ◽  
El Hachemi Amara ◽  
Djamila Bennaceur-Doumaz ◽  
R. Boutaka ◽  
H. Kellou ◽  
...  
Keyword(s):  
Temperature Field ◽  
Laser Beam ◽  
Film Growth ◽  
Three Dimensional ◽  
Layer Growth ◽  
Heat Diffusion ◽  
Metallic Surface ◽  
Heat Diffusion Equation ◽  
Computational Procedures ◽  
Volume Method

In this paper, we study the oxidation process during the heating of a titanium metallic surface by a Nd-YAG fiber pulsed laser beam under air environment. For this, we adopted an approach that considers a three-dimensional heat diffusion model coupled with an oxidation parabolic law (oxidation kinetics). The heat diffusion equation solved numerically, gives the temperature field. The oxide film growth is simulated by implementing a dynamic mesh technique. We developed computational procedures UDFs (User Defined Function) running interactively with the Fluent fluid dynamics software [ that implements the finite volume method. These UDFs are developed to insert the oxidation law, the temperature field, the specific boundary conditions and the mesh deformation into the calculation.

Computer simulation of target link explosion in laser programmable redundancy for silicon memory

1986 ◽  
Vol 1 (2) ◽  
pp. 368-381 ◽  
Author(s):  
L.M. Scarfone ◽  
J.D. Chlipala
Keyword(s):  
Thermal Evolution ◽  
Three Dimensional ◽  
Heat Diffusion ◽  
Dielectric Films ◽  
Threshold Temperature ◽  
Heat Diffusion Equation ◽  
Heating Effects ◽  
Transparent Dielectric ◽  
Difference Form ◽  
Pulse Energies

Pulses of Q-switched Nd-YAG radiation have been used to remove polysilicon target links during the implementation of laser programmable redundancy in the fabrication of silicon memory. The link is encapsulated by transparent dielectric films that give rise to important optical interference effects modifying the laser flux absorbed by the link and the silicon substrate. Estimates of these effects are made on the basis of classical plane-wave procedures. Thermal evolution of the composite structure is described in terms of a finite-difference form of the three-dimensional heat diffusion equation with a heat generation rate having a Gaussian spatial distribution of intensity and temporal shapes characteristic of commercial lasers. Temperature-dependent thermal diffusivity and melting of the polysilicon link are included in the computer modeling. The calculations account for the discontinuous change in the link absorption coefficient at the transition temperature. A threshold temperature and corresponding pressure, sufficiently high to rupture the dielectric above the link and initiate the removal process, are estimated by treating the molten link as a hard-sphere fluid. Numerical results are presented in the form of three-dimensional temperature distributions for 1.06 and 0.53 μm radiation with pulse energies 3.5 and 0.15μJ, respectively. Similarities and differences between heating effects produced by long (190 ns FWHM/740 ns duration) and short (35 ns FWHM/220 ns duration) pulses are pointed out.

scholarly journals Three-Dimensional Temperature Distribution Produced by a Moving Laser Beam

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
R. Uyhan
Keyword(s):  
Temperature Field ◽  
Theoretical Model ◽  
Temperature Distribution ◽  
Laser Beam ◽  
Three Dimensional ◽  
Constant Speed ◽  
Unsteady Temperature ◽  
Unsteady Temperature Field ◽  
Absorbing Layer

An axisymmetric laser beam, moving with constant speed, heats a thin infrared absorbing layer sandwiched between two plastic sheets. We use a simplified theoretical model to study the three-dimensional unsteady temperature field produced by the moving laser beam.

Structural Defects and Their Relationship to Nucleation of Gan Thin Films

1996 ◽  
Vol 423 ◽  
Author(s):  
Weida Gian ◽  
Marek Skowronski ◽  
Greg S. Rohrer
Keyword(s):  
Film Growth ◽  
Three Dimensional ◽  
Scanning Force Microscopy ◽  
Columnar Structure ◽  
Layer Growth ◽  
Buffer Layers ◽  
Structural Defects ◽  
Layer By Layer ◽  
Extended Defects ◽  
Edge Dislocations

AbstractMicrostructure and extended defects in α-GaN films grown by organometallic vapor phase epitaxy on sapphire substrates using low temperature AIN (or GaN) buffer layers have been studied using transmission electron microscopy. The types and distribution of extended defects were correlated with the film growth mode and the layer nucleation mechanism which was characterized by scanning force microscopy. The nature of the extended defects was directly related to the initial three-dimensional growth. It was found that inhomogeneous nucleation leads to a grain-like structure in the buffer; the GaN films then have a columnar structure with a high density of straight edge dislocations at grain boundaries which are less likely to be suppressed by common annihilation mechanisms. Layer-by-layer growth proceeds in many individual islands which is evidenced by the observation of hexagonal growth hillocks. Each growth hillock has an open-core screw dislocation at its center which emits monolayer-height spiral steps.

Simulation on Temperature Field of Gap Oil Film in Constant Flow Hydrostatic Center Frame

2011 ◽  
Vol 121-126 ◽  
pp. 4706-4710
Author(s):  
Yong Hai Li ◽  
Xiu Li Meng ◽  
Xiao Dong Yu ◽  
Bo Wu ◽  
Chun Li Gao ◽  
...  
Keyword(s):  
Temperature Field ◽  
Angular Velocity ◽  
Thermal Deformation ◽  
Three Dimensional ◽  
Constant Flow ◽  
Distribution Law ◽  
Simulation Research ◽  
Oil Film ◽  
Temperature Performance ◽  
Volume Method

In order to solve the thermal deformation of the hydrostatic center frame in the heavy type horizontal lathe, a simulation research concerning temperature field of hydrostatic center frame is described. The Finite Volume Method of CFX has been used to compute three-dimensional temperature field of gap fluid between workpiece and bearing pillow. This research theoretically analyzes the influence of angular velocity on the bearing temperature performance according to lubricating theory and computational fluid dynamics, and it has revealed its temperature distribution law of gap oil film. Results indicate that an improved characteristic will be affected by angular velocity easily, and oil cavity temperature increases by gradually with angular velocity enhancing. Through this method, the safety of a hydrostatic center frame can be forecasted, and the optimal design of such products can be achieved, so it can provide reasonable data for design, lubrication, experience and thermal deformation computation for hydrostatic center frame in the heavy type horizontal lathe.

Transient, Three-Dimensional Numerical Model of a Laser Cutting Process With Phase Change Consideration

2004 ◽  
Author(s):  
Gustavo Gutie´rrez ◽  
Juan Guillermo Araya
Keyword(s):  
Temperature Field ◽  
Laser Beam ◽  
Phase Change ◽  
Numerical Models ◽  
Three Dimensional ◽  
Phase Changes ◽  
Ceramic Surface ◽  
Numerical Predictions ◽  
Physical Shape ◽  
Finite Volume Approach

Phase change problems are encountered in several manufacturing and material processing applications. Such problems are computationally challenging because it is necessary to solve a non-linear heat conduction equation and take into considerations the conditions needed to produce material ablation, varying continuously the heat source position, thermo physical properties and physical shape of the domain. This research presents a numerical simulation of the temperature field and the removed material resulting from the impingement of a moving laser beam on a ceramic surface. A finite volume approach has been developed to predict the temperature field including phase changes generated during the process. The model considers heat losses by convection and radiation due to the high temperatures involved and uses a coordinate system affixed to the workpiece; therefore no quasi-steady conditions are assumed, as in the majority of previous works. Numerical predictions were compared with former three-dimensional numerical models considering a semi-infinite solid and from experimental data found in the literature. This study gives insight into the interactions between the laser beam and a silicon nitride workpiece during the cutting.

Three Dimensional Transient Heat Transfer Model for Steel Billet Heating in Reheat Furnace

2012 ◽  
Author(s):  
Satish Kumar Dubey ◽  
Neelesh Agarwal ◽  
P. Srinivasan
Keyword(s):  
Heat Transfer ◽  
Temperature Field ◽  
Oxide Scale ◽  
Three Dimensional ◽  
Heat Transfer Model ◽  
Heat Diffusion ◽  
Transient Heat Transfer ◽  
Transfer Model ◽  
Scale Thickness ◽  
Reheating Process

In steel rolling mills reheat furnaces are used to heat the billets prior to rolling processes. Reheating is one of the most energy intensive processes in the steel industries. Inadequate temperature measuring techniques and extremely complex analytical solution for temperature filed calculations demands suitable numerical model. In the present work a three dimensional transient heat transfer model is developed for billet heating in reheat furnaces. Conduction heat transfer within the billets is modeled using Finite Difference Method (FDM). Fully implicit spatial discretization approximation was used for three dimensional heat diffusion equation of billet. The three dimensional model takes into account the temperature dependent thermo physical properties, reaction heat effect and growing oxide layer. Algorithm is implemented in MATLAB® to solve three dimensional discretization equations. Model is capable of predicting the temperature field for billet and oxide scale thickness for any residence time. The predicted results are in reasonable concurrence with available data. The main objective of this work is to predict billet temperature field and oxide scale thickness for the various residence times, which may be vital for development of energy efficient optimization strategy for reheating process.

Simulation and Optimize Design for Deflector Plate of the Vehicle Mounted Vertically Thermal Launched Missile

2012 ◽  
Vol 459 ◽  
pp. 579-583
Author(s):  
Shao Zhen Yu ◽  
Yi Jiang ◽  
Yan Li Ma ◽  
Yan Yan Ma ◽  
Bo Wei Liu
Keyword(s):  
Numerical Simulation ◽  
Temperature Field ◽  
Simulation Study ◽  
Three Dimensional ◽  
Gas Jet ◽  
Potential Core ◽  
Structured Grid ◽  
Main Factors ◽  
Deflector Plate ◽  
Volume Method

In this dissertation, academic analysis of the influence to deflector plate in gas jet field of a Vehicle-mounted Vertically Thermal Launched missile as well as simulation study. The finite volume method, a fully structured grid, three-dimensional N-S equation is used for the numerical simulation of the process during the missile launching. The two main factors: temperature and forces on the launcher is the standard we test a launching system. The temperature on the position we test will rise with the decreasing length of the deflector. Especially, when the length is near to the potential core, the temperature changed greatly. Also, the angles of the deflector under the same length have less impacted on the temperature field. However, the force on the deflector would be change greater than the temperature with the change of angles

scholarly journals Multidisciplinary design optimization of film-cooled gas turbine blades

1999 ◽  
Vol 5 (2) ◽  
pp. 97-119 ◽  
Author(s):  
Shashishekara S. Talya ◽  
J. N. Rajadas ◽  
A. Chattopadhyay
Keyword(s):  
Objective Function ◽  
Design Optimization ◽  
Gas Turbine ◽  
Upper Bound ◽  
Film Cooling ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Heat Diffusion ◽  
Heat Transfer Analysis ◽  
Heat Diffusion Equation

Design optimization of a gas turbine blade geometry for effective film cooling toreduce the blade temperature has been done using a multiobjective optimization formulation. Three optimization formulations have been used. In the first, the average blade temperature is chosen as the objective function to be minimized. An upper bound constraint has been imposed on the maximum blade temperature. In the second, the maximum blade temperature is chosen as the objective function to be minimized with an upper bound constraint on the average blade temperature. In the third formulation, the blade average and maximum temperatures are chosen as objective functions. Shape optimization is performed using geometric parameters associated with film cooling and blade external shape. A quasi-three-dimensional Navier–Stokes solver for turbomachinery flows is used to solve for the flow field external to the blade with appropriate modifications to incorporate the effect of film cooling. The heat transfer analysis for temperature distribution within the blade is performed by solving the heat diffusion equation using the finite element method. The multiobjective Kreisselmeier–Steinhauser function approach has been used in conjunction with an approximate analysis technique for optimization. The results obtained using both formulations are compared with reference geometry. All three formulations yield significant reductions in blade temperature with the multiobjective formulation yielding largest reduction in blade temperature.

Research on Temperature Field of Hydrostatic Thrust Bearing with Annular Cavity Multi-Pad

2011 ◽  
Vol 121-126 ◽  
pp. 3477-3481
Author(s):  
Xiao Dong Yu ◽  
Xiu Li Meng ◽  
Bo Wu ◽  
Chun Li Gao ◽  
Zhi Xin Qiu ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Temperature Field ◽  
Thermal Deformation ◽  
Thrust Bearing ◽  
Three Dimensional ◽  
Distribution Law ◽  
Simulation Research ◽  
Temperature Performance ◽  
Simulation Results ◽  
Volume Method

A simulation research concerning temperature field of hydrostatic thrust bearing having annular cavities multi-pad was described in order to solve the thermal deformation of the hydrostatic thrust bearing with annular cavity multi-pad in the heavy CNC equipment. The Finite Volume Method of CFX has been used to compute three-dimensional temperature field of gap fluid between the rotation worktable and base. This study theoretically analyzes the influence of rotating velocity on the bearing temperature performance according to computational fluid dynamics and lubricating theory. It has revealed its temperature distribution law. The simulation results indicate that an improved characteristic will be affected by rotating velocity easily, and oil cavity temperature increases by gradually with rotating velocity enhancing. Through this method, the safety of a hydrostatic thrust bearing having annular cavities multi-pad can be forecasted, and the optimal design of such products can be achieved, so it can provide reasonable data for design, lubrication, experience and thermal deformation computation for hydrostatic thrust bearing in the heavy CNC equipment.

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