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1

Modelling of transport phenomena in gas tungsten arc welding

Farzadi A., Serajzadeh S., Kokabi A. H.

Archives of Materials Science and Engineering

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2007

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Vol. 28, nr 7

417-420

EN

Purpose: Since numerical heat transfer and fluid flow models have provided significant insight into welding process and welded materials that could not been achieved otherwise, there has been an important interest in the quantitative representation of transport phenomena in the weld pool. On the other hand, the temperature and velocity distributions of the molten metal as well as the cooling rate after welding operation affect the weld geometry, the microstructure, and the mechanical properties of weld zone. This work demonstrates that the application of numerical transport phenomena can significantly add to the quantitative knowledge in welding and help the welding community in solving practical problems. Design/methodology/approach: The temperature and velocity fields are simulated using the solution of the equations of conversation of mass, energy and momentum in three-dimension and under steady-state heat transfer and fluid flow conditions. Findings: The weld pool geometry and various solidification parameters were calculated. The calculated weld pool geometries were in good agreement with the ones obtained using the experiments. The solidification parameters of G and G/R are determined. It is found that as the welding speed increases, the value of G/R at the weld pool centerline decreases. Research limitations/implications: Welding process used is this study is gas tungsten arc (GTA) welding and base metal is commercial pure aluminum. This model can be investigated to simulate other materials and welding processes. Also the results of this study such as the temperature field can be used in the simulation of microstructure, mechanical properties, etc of welding zone. Originality/value: In this research the solidification parameters of G, R and G/R can be used for prediction of the solidification morphology and the scale of the solidification structure.

2

Materiały gradientowe jako nowe możliwości współczesnej techniki.

Hodor K., Zięba P., Olszowska-Sobieraj B.

Inżynieria Materiałowa

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1999

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R. XX, nr 6

595-600

PL

W pracy wyjaśniono istotę gradientu cechy materiałowej, dokonano przeglądu i klasyfikacji FGM w zależności od: rodzaju łączonych materiałów, zasięgu gradientu, geometrii gradacji, funkcji jaką pełni gradient i od tego, w jaki sposób gradient umożliwia osiągnięcie pożądanego efektu. Zaprezentowano procesy technologiczne, w wyniku których powstają FGM. Obok procesów konstruktywnych i metod opartych na zjawiskach transportu, zwrócono szczególną uwagę na metodę polegającą na połączeniu ze sobą metalu i związku międzymetalicznego przy wykorzystaniu przemiany eutektycznej. Podano przykłady zastosowań FGM w przemyśle lotniczym i kosmicznym, optyce, elektronice i medycynie. Omówiono krajowe zainteresowanie FGM, ze szczególnym uwzględnieniem możliwości otrzymania FGM bezpośrednio w wyniku procesu odlewniczego.

EN

In this paper current state of art in the area of FGM is presented. The principles of the material property gradient is explained, then FGM are classified into several groups according to the material classes they combine, the relative gradient extension, the geometry of the gradation, the function in a component and the way in which the gradient acts to achieve a desired response. Two basic processes of FGM productions are discussed, that is constructive one and transport one. Simultaneously, a new method of FGM manufacturing, like eutectic bounding is presented. Then, some examples of the applications of FGM in aeronautics and space industry, electronics, optics and medicine are given. National interest with FGM is briefly described including the most recent example of FGM production directly due casting process.

3

Self-consistent description of the plasma and impurity transport in tokamak reactor. Pt. 2, Results of calculations

Zagórski R.

Journal of Technical Physics

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1998

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Vol. 39, no 2

315-348

EN

A model has been developed which is capable of describing in a self-consistent way the plasma dynamics in the central and edge regions of a fusion reactor. The core plasma is treated in the frame of the 0D model in which empirical scaling law for energy confinement time is included. The model accounts for the energy losses due to bremsstrahlung and line radiation as well as alpha particle heating. A 1D analytical model for plasma and impurity transport outside the last closed magnetic surface (LCMS) is applied. The model accounts for strong gradients of plasma parameters along magnetic field lines in the divertor. The sputtering phenomena at the plate and radiating cooling by injected impurities are trated self-consistently in the model. The numerical code BILDIV has been built in order to solve the nonlinear set of equations describing the self-consistent transport of plasma and impurities in the SOL. The model has been confirmed by comparison with other models and experiments. Analytical estimates have been evalued showing the most important features of the self-consistent plasma behavior in the tokamak reactor. These estimations have been confirmed by numerical calculations. The model has been used to investigate operating regimes of the ignition experiment. Analysis has been performed for different first wall materials (C, Ni, Mo, W) for ITER-like tokamak.