Research Initiation: Solid-Liquid Interface Morphology During Welding

本研究的目的是了解单晶和多晶薄板自焊全熔透焊过程中出现不同固液界面形态的原因。这项研究将确定热流、表面张力、界面动力学效应和晶界(包括晶体各向异性的影响)在熔池形状和熔合区最终性能的发展中所起的作用。研究方法包括利用有限差分、有限元、谱和/或边界积分技术对固-液焊接熔池界面进行数值计算，这些界面被建模为考虑热流并与界面性质耦合的非线性自由或运动边界。此外，在可能的情况下，将使用解析(线性和非线性)渐近分析对各类熔池形状的急剧转变进行数值计算；该分析将有助于更清楚地了解特殊极限情况，并与数值结果进行比较。结果将与现有的实验结果进行比较，目标是最终提供一组焊接条件和最终材料性能之间的相关性。这将有助于了解可消除或绕过有害的熔池形状特征的焊接方法的类型，这些特征会导致产生缺陷和织构熔合区的位置。该项目有可能提高焊接过程的质量和控制。

The goals of this research are to understand the reasons for the appearance of different solid-liquid interface morphologies during the autogenous full penetration welding of single and polycrystalline thin plates. The research will identify the role that heat flow, surface tension, interfacial kinetic effects and grain boundaries play (which include the effects of crystallographic anisotropy) in the development of the weld pool shape and the resultant properties of the fusion zone. Methods of research include numerical calculation of solid-liquid weld pool interfaces modeled as nonlinear free or moving boundaries, that account for heat flow and are coupled with the interfacial properties, by using finite difference, finite element, spectral and/or boundary integral techniques. Furthermore, numerical calculation of sharp transitions in classes of weld pool shapes using analytical (both linear and nonlinear) asymptotic analysis will be performed whenever applicable; the analysis will be helpful in gaining a clearer knowledge of special limiting cases and for comparison with the numerical results. The results will be compared to existing experimental results, and the goal is to ultimately provide a correlation between a set of welding conditions and final material properties. This would provide an understanding of the types of welding methods that might eliminate or circumvent deleterious weld pools shape features which give rise to sites for defect generation and textured fusion zones. The project has potential to improve the quality and control of the welding process.