Abstract:The lightweight thin-walled parts are increasingly used in high-tech engineering fields such as aviation, aerospace and automobile. Wrinkling instability has always been one of the major defects in thin-walled parts forming processes. Therefore, the study on prediction of plastic wrinkling instability becomes particularly important in the process of forming lightweight thin-walled parts. Based on the inconsistent between the instability simulation prediction of thin-walled tube structures and the actual situation which are due to various initial defects (such as uneven thickness, dimensional deviations, etc.), this paper takes the example of the AA6061 diameter-reduced tubes by solid granule medium forming technology and combines the DYNAMIC algorithm which is the most suitable for complex contact conditions in ABAQUS, simulates the tube outer pressure compression forming with no initial imperfections, buckling modes initial imperfections, uneven thickness initial imperfections and the last one which contains buckling modes initial imperfections and uneven thickness initial imperfections. The dynamic finite element method with simultaneous introduced buckling modes and thickness unevenness imperfections can accurately predict the instability waveforms of the tube through the comparison between the simulations and the tests. The reliability of the simulation method is verified through the comparison between the simulative and experimental force-displacement curves.

Key words: tube outer pressure compression forming; numerical simulation of wrinkling instability; buckling mode; thickness imperfection