Sharif Digital Repository

Efficient control of a gas metal arc welding (GMAW) process enables one to obtain high quality products as a consequence of achieving a high quality weld. Although control of the droplet detachment frequency in the welding process would play a great role in improving the welding quality, measuring this variable is difficult and expensive. In this paper, we attempt to control the frequency of droplet detachments without directly measuring it. To this end, we utilize the hybrid property of the GMAW process to indirectly control the frequency. Specifically, a mixed logical dynamical (MLD) model is obtained by considering the hybrid act of the process during droplet detachment. Then, a nonlinear... 

The dynamics of droplet detachment from a surface is a fundamental topic studied in coating engineering, fluid mechanics, and subsurface engineering applications. This topic has direct relevance to wettability alteration using the modified ionic composition of water in contact with oil droplet, low salinity waterflooding (LSWF). Previous experimental studies of LSWF have shown a very long timescale in wettability alteration which cannot be explained using bulk diffusion coefficient. In the present study, we address both the time scale of detachment, as well as the impact of buoyancy and interfacial forces (referred to as Bond number) on droplet detachment by proposing an advanced... 

In the welding process, droplet detachment regularity is important for a good welding quality. The frequency of detachment is one of influential indices for assessing the quality of GMAW in the globular transfer mode. In this paper, a relationship is estimated for measuring droplet detachment frequency in the globular GMAW. The droplet detachment frequency is estimated with a curve fitting by the least squares error (LSE) method. By using short time frequency transform (STFT) we can extract the frequency contents from the mass of drop that is one of the states in the welding model