Computational Fluid Dynamics (CFD) Simulation of Inclusion Motion under Interfacial Tension in a Flash Welding Process

Non-metallic inclusions particles are detrimental to the mechanical properties of a material. It is very important to understand the motion behavior of inclusion particles in molten metal. The motion behavior of non-metallic inclusion particles during weld pool solidification and their distribution in joint areas is dependent on various factors. In the alternative current (AC) flash welding process, inclusions motions are dependent on welding plate movement, interfacial tensions, etc. Apart from this, the temperature of the molten metal in the welding zone and the size of inclusion particles also play an important role. Secondly, the Marangoni forces are developed due to interfacial tension which affects the movement of inclusion particles at the solid-liquid interface in a solidifying welding pool. The interfacial tension varies with the change in surfactant concentration and other factors. In this work, the effect of upsetting rate and interfacial tension on alumina inclusions has been studied. The interfacial tension controls the pushing and engulfment of non-metallic inclusions at the solid-liquid interface. A two-dimensional multiphase mathematical model has been developed to study the inclusion motion behavior at the solid–liquid interface in a solidifying weld pool. The numerical model has been developed by adding the volume of fluid method (VOF), a dynamic mesh model and discrete phase model for a realistic approach. The predicted results show that the upsetting setting parameters have a substantial effect on the overall non-metallic inclusion motion. The inclusions were seen moving away from the welded joint due to the high up-setting rate. The results also reveal that the inclusions were engulfed by the solidification front under the effect of the strong interfacial tension between the non-metallic inclusions and the molten steel.

Flash Welding of Microcomposite Wires for Pulsed Power Applications

This paper presents the experimental results of Cu-Nb wire joining upon applying flash welding technology. The present research is aimed at investigating the structure, electrical and mechanical properties of butt welding joints of Cu-Nb conductors, usable for coils of pulsed magnetic systems. The butt joint structure was found to be free of welding defects. The structure of the butt welded joint provides an insignificant increase in electrical resistance and sufficient ultimate strength and plasticity of the joint. The tensile strength of the welded sample reaches 630 MPa.

Convolutional Neural Network Analysis of Recurrence Plots for Anomaly Detection

Recurrence plots are widely used to represent and characterize recurrence behaviors of complex systems. Although the recurrence plot captures a great deal of useful information, very little has been done to leverage convolutional neural networks (CNNs) regarding the learning of recurrence dynamics. In this paper, we develop a new CNN approach to investigate recurrence patterns in multisensor signals for real-time anomaly detection. The proposed methodology is evaluated and validated in both simulation studies and a real-world case study for quality control of a flash welding process, which is commonly used to manufacture anchor chains in the shipbuilding industry. First, we develop a new sensing system to collect electrical-current and electrode-position profiles in the flash welding process. Second, recurrence plots are derived with multisensor signals collected from the manufacturing process of each workpiece in the anchor chain. Third, CNNs are developed to learn workpiece-to-workpiece variations in the recurrence plots. Experimental results show that the proposed CNN models of recurrence plots yield superior performance for anomaly detection of welding quality variations, improving the automation level of flash welding processes.

Preparation of vertically aligned carbon nanotube/polyaniline composite membranes and the flash welding effect on their supercapacitor properties

A vertically aligned SWNT/PANi membrane was fabricated by electric-filtration coupling and subsequent flash-welding method, exhibiting higher mechanical and supercapacitance properties.