Tube joining by asymmetric plastic instability

• Development of out-of-plane, inclined, plastic instability waves in tubes subjected to axial compression.
• Extension of tube joining by means of asymmetric plastic instability to inclined tube attachments.
• Design guidelines defined as a function of the major process parameters.
• Examples showing the effectiveness and environmental friendly characteristics of the new process.

This paper explores inclined, out-of-plane, plastic instability waves in thin-walled tubes subjected to axial compression and the factors affecting its development and propagation. Explanations are given for the experimental observations and finite element predictions of plastic flow and compression load in a wide range of process parameters. Basic design guidelines are provided, making use of plastic instability waves to produce tube attachments in situations where the axis of the branch tube is inclined to the axis of the main body tube.The overall content of the paper widens and enhances previous work published by the authors in perpendicular tube attachments by providing a complete characterization of the process feasibility window for inclined tube attachments. The new developments in asymmetric plastic instability are a step forward in tube joining because their offer an effective and environmentally friendly solution for producing complex tube attachments in situations where there are little or no-alternatives of utilizing conventional processes involving welding and brazing.