A study of the effects of welding parameters on electron beam welding in the space environment

Abstract

This study was undertaken in order to be sure that no hazard would exist from impingement of hot molten metal particle detachments upon an astronauts' space suit during any future electron beam welding exercises or experiments. The conditions under which molten metal detachments might occur in a space welding environment were analyzed. The safety issue is important during welding with regards to potential molten metal detachments from the weld pool and cold filler wire during electron beam welding in space. This investigation was undertaken to evaluate if molten metal could detach and come in contact with astronauts and burn through the fabric of the astronauts' Extravehicular Mobility Unit during electron beam welding in space. Molten metal detachments from either the weld/cut substrate or weld wire could present harm to an astronaut if the detachment was to burn through the fabric of the astronauts' space suit. Theoretical models were developed to predict the possibility and size of the molten metal detachment hazards during the electron beam welding exercises at Low Earth Orbit. Some possible ways of obtaining molten metal drop detachments would include an impulse force, or bump, to the weld sample, cut surface, or filler wire. Theoretical models were developed for these detachment concerns from principles of impact and kinetic energies, surface tension, drop geometry, surface energies, and particle dynamics. A weld pool detachment parameter for specifying the conditions for metal weld pool detachment by impact was derived and correlated to the experimental results. The experimental results were for the most part consistent with the theoretical analysis and predictions.