Diego Santiago

Numerical modeling of welded joints by the "Friction Stir Welding" process

The present work is aimed to simulate the Friction Stir Welding process as a three-dimensional thermally coupled viscoplastic flow. A Finite Element technique is employed, within the context of a general purpose FEM framework, to provide the temperature distributions and the patterns of plastic flow for the material involved in the welded joints. The computational tool presented here may be of great relevance for technologist seeking to set the process control variables, as they are intended to obtain suitable material properties that yield the adequate on service response of the structural components.

A Computational Model for the Numerical Simulation of FSW Processes

In this paper a computational model for the numerical simulation of Friction Stir Welding (FSW) processes is presented. FSW is a new method of welding in solid state in which a shouldered tool with a profile probe is rotated and slowly plunged into the joint line between two pieces of sheet or plate material which are butted together. Once the probe has been completely inserted, it is moved with a small tilt angle in the welding direction. Here a quasi‐static, thermal transient, mixed multiscale stabilized Eulerian formulation is used. Norton‐Hoff and Sheppard‐Wright rigid thermo‐viscoplastic material models have been considered. A staggered solution algorithm is defined such that for any time step, the mechanical problem is solved at constant temperature and then the thermal problem is solved keeping constant the mechanical variables. A pressure multiscale stabilized mixed linear velocity/linear pressure finite element interpolation formulation is used to solve the mechanical problem and a convection mul...

Evaluation and modelling of integral capacitors produced by interdigitated comb electrodes

Integral capacitors (IC) of one or two-layer printed wiring board (PWB) circuits were produced using comb electrodes fixtures and dielectric composites as the inter-electrode material. ICs were fabricated at laboratory scale, using copper comb electrodes and BaTiO3-epoxy composite materials deposited on a glass-Epoxy FR4 board. They were experimentally tested in order to obtain their electrical response. Furthermore, ICs behaviour was modelled through 2-dimensional models applying finite element method (FEM). Results showed that by this laboratory technique it was possible to obtained integral capacitors with low dielectric losses. Moreover, acceptable agreement was found between numerical and experimental capacitance results for all the different analysed ICs. In conclusion, 2D FEM models are a suitable tool to predict electric response of IC devices.

Modelado numérico del proceso de pultrusión en materiales compuestos

Received: February 14, 2003; Revised: June 26, 2003A mathematical pultrusion model of a thermosetting matrix composite is presented. The en-ergy balance was solved by Finite Elements techniques using a program developed for this pur-pose. This model is applied to describe the temperature and resin conversion profiles along thedie. This study was developed considering different pulling velocity, die temperature, differentcomposite and different sections die. The model outcomes are verified through comparison withthe experimental results reported in the literature.