Borovyk Y. Development and Investigation of a Longitudinal Welded Structure of Transformable Volume for Space Apparatus Construction

The dissertation is devoted to the development and fabrication of a metallic transformable-volume structure (TVS) for space applications, consisting of conical sections, with mechanical characteristics that can be predicted at the stage of its creation, taking into account the aggressive operating environment. The determination of the structural scheme, which corresponds to the best combination of dimensional characteristics, high compactness, and stability under the influence of operational loads and space factors, has been carried out. Optimal ratios of geometric parameters of the conical sections of the TVS, including their thickness and parameters of circular folds formed during compact transformation, have been determined, ensuring the highest stability of the selected material shell under external loads. A comparison of finite element models of welded section unfolding with the same initial geometry and thickness but with different numbers of folds and compactness has been conducted. The influence of microplasma welding and its characteristics on the final mechanical properties of the TVS, as well as the developed welding regimes for sections of the TVS made of stainless steel with a thickness of 0.3 mm, has been investigated. The TVS requires precise assembly conditions before welding, and only under these conditions is it possible to approximate the necessary mechanical characteristics of the weld to those of the base metal. The optimal parameter of the natural frequency of the 3-meter-long TVS, determined by modal analysis, has been confirmed to ensure the physical and mechanical characteristics that prevent resonance frequency vibrations during operation, thereby maintaining the useful load. The object of research - is self-supporting structures of a transformable space destination The subject of research - is the technological processes of manufacturing and the study of the operational properties of a long-dimensional welded structure of a transformed volume. The purpose of the work: creation of a long-term design of the transformed volume with provision of the specified geometric parameters, vacuum density after passing through deformation cycles and load-bearing capacity under the influence of space factors. The scientific novelty of the work consists in a set of constructive and technological solutions aimed at creating a long-dimensional welded structure of a transformable volume (TVS) for space purposes, in the developed technologies of welding, forming and verification by experimental evaluations of the results of mathematical modeling of stress-strain states and frequencies of natural oscillations of the TVS, which provide its necessary bearing capacity and mass-dimensional parameters, high strength and vacuum density of welded joints.