Tailoring complex weld geometry through reliable heat-transfer and fluid-flow calculations and a genetic algorithm
- PDF / 687,463 Bytes
- 11 Pages / 612 x 792 pts (letter) Page_size
- 86 Downloads / 238 Views
I. INTRODUCTION
IN recent years, complex numerical models of heat transfer and fluid flow for various fusion-welding processes such as the gas tungsten-arc welding,[1,2,3] gas metal-arc (GMA) welding,[4–7] and laser welding[8,9,10] have been developed to better understand the physical processes in welding and the nature of the welded materials. These models have enabled accurate quantitative calculations of thermal cycles and fusion-zone geometry that have been used to quantitatively understand various attributes of the welded joints like weld metal-phase composition,[11,12] grain structure,[13,14] and inclusion structure.[15] Although these models have provided significant insight about the welding processes and welded materials, their applications have been limited due to several factors. First, although these heat-transfer and fluid-flow models use time-tested equations of conservation of mass, momentum, and energy, their predictions of temperature fields and thermal cycles do not always agree with experimental results because the models require many input variables, all of which cannot be prescribed with certainty. For example, the reported values of arc efficiency vary significantly for apparently similar welding conditions, reflecting the complexity of the GMA welding process.[7,16–20] Values of arc efficiency significantly affect the results of numerical heat-transfer and fluid-flow calculations. Therefore, reliable predictions of temperature and velocity fields cannot be obtained without ascertaining accurate values of this and other uncertain parameters.[18,20–22] Second, the models are designed to calculate the temperature and velocity fields for a given set of welding variables. A. KUMAR, Graduate Student, and T. DEBROY, Professor, are with the Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA 16802. Contact e-mail: [email protected] Manuscript submitted February 14, 2005. METALLURGICAL AND MATERIALS TRANSACTIONS A
However, very often what is needed is to determine the welding variables required to achieve a given weld attribute such as the weld geometry. The current generation of unidirectional heat-transfer and fluid-flow models are designed to calculate temperature and velocity fields from welding conditions and are incapable of determining welding conditions. Finally, the GMA welding system is highly complex and involves nonlinear interaction of several welding variables. As a result, a particular weld attribute such as the geometry can be obtained via multiple paths, i.e., through the use of various sets of welding variables. The current generation of numerical heat-transfer and fluid-flow models cannot determine alternative pathways to achieve a target weld attribute. Here, we show that by combining numerical heat-transfer and fluid-flow models with a suitable optimization algorithm, the reliability of the model predictions can be significantly enhanced. Furthermore, the combined models now have new capabilities for bidirectional simulation, where
Data Loading...
