Numerical Simulation and Optimization of Stefan Dimensionless Number to Control TIG Molten Metal Fluidity

Abstract

Welding researchers have a responsibility of improving the integrity

and strength of welded structures, the fluid flow of the molten metal

has a major effect on energy transport from the weld pool to the

surrounding material, which in turn affects the geometry.

Additionally, the flow motion and its volatilities determine the

material properties and quality of the weld. This study was carried

out with the aim of optimizing and predicting the dimensionless

parameters characterizing molten metal flow patterns of mild steel

weld pool ,with a purpose of developing models to explain the

relationship between this dimensionless numbers and the flow

pattern. A 30-run central composite design matrix was generated

which guided in performing the experiments, the stefan

dimensionless number was computed and recorded for each

specimen. Thereafter the response surface methodology expert

system was employed to analyse the data collected from the

experiment.In this study the second order polynomial model was

adopted having current, voltage, gas flow rate and welding speed as

input factors while the stefan dimensionless numbers is the target

response. The result obtained possessed adequate strength to predict

the targeted response.RSM model produced numerical optimal

solutions having a combination of current 189.85A ,voltage 18.00v

wire diameter 1.61mmand wire feed rate of 25mm/min to produce a

welded joint with with Stefan number of 2.69 x10 6

, at a desirability

value of 71.8%.In this study an approach using the response surface

methodology for optimizing and predicting weld process parameters

in order to enhance the integrity of welded joints has been

successfully introduced and its effectiveness and efficiency well

demonstrated.