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The paper analyzes the problem of friction stir welding (FSW) technology. The mechanism of thermo-mechanical process of the FSW method has been identified and a correlation between the weld zone and its microstructure established. Presented are the basic analytical formulations for the definition of temperature fields. Analysis of influential parameters of welding FSW technology at the zone of the weld material and mechanical properties of the realized joint was performed. Influential welding parameters were defined based on tool geometry, technological parameters of processing and the axial load of tool. Specific problems with the FSW process are related to gaps (holes) left behind by a tool at the end of the process and inflexibility of welding regarding the degree of variation of material thickness. Numerical simulation of process welding FSW proceeding was carried out on the example of Aluminum Alloy (AA 2219) using the ANSYS Mechanical ADPL (Transient Thermal) software package. The defined was the temperature field in the welding process at specified time intervals.

SummaryIn this paper, we investigate global and local stability of columns with an open and a closed thin-walled cross section. The proposed model of global stability is made of two deformable elements connected with an elastic joint. Stiffness of the elastic joint represents local discontinuity of the cross section of the column caused by the loss of stability of individual plates. The model of local stability of the columns is conceptualized on the principle of continuity of individual plates of the cross section. The coefficients of local buckling are defined as geometric parameters of the column with a rectangular hollow section (RHS) and a U-shaped cross section. The dominant parameters that influence the interactive behaviour of local and global buckling are the slenderness of plates and the column as a whole. The basic function of the developed models is to identify the stability mechanism in terms of better estimation of the critical force and higher load capacity.