Investigation into wrinkling behavior of thin-walled 5A02 aluminum alloy tubes under internal and external pressure

Abstract

In order to investigate the wrinkling behavior of thin-walled tubes under complex stress states, a dedicated experimental setup was designed and manufactured. In this experimental setup, the internal pressure, the external pressure and the axial feeding of left and right punches were coupled together through accurate closed-loop servo control. Thin-walled 5A02 aluminum alloy tubes were pushed into the die cavity under different internal pressures or under the combined actions of internal and external pressures with the same amount of axial feeding. Meanwhile, the wrinkle formation, as well as the stress state, was predicted numerically using the FEA Abaqus/Explicit solver. It has been found that the number and shape of wrinkles are strongly dependent on the internal pressure when only internal pressure is applied to the inner surface of the tube. Furthermore, the wrinkle formation is closely related to the inhomogeneous stress distribution induced by local bending and axial displacement. Moreover, the shape of wrinkles can be fitted effectively using the GaussAmp function when the internal pressures of 1.2ps, 1.6ps and 1.8ps (ps represents the initial yield pressure for the tube) are applied. In addition, the effect of external pressure has been discussed under three cases and it is shown that the wrinkling behavior exhibits hardly any dependence on the external pressure for the constant pressure difference. Finally, the formation of middle wrinkle can be prevented by higher external pressure both for the constant internal pressure and the variable internal pressure.