Numerical study of the lateral crushing and re-inflation of stainless steel and aluminum tubes

The purpose of this numerical study is to investigate the possibility of re-inflating laterally crushed tubes back to their original circular-cylindrical shape, without using a die. This can find applications in a non-conventional tube bending process as well as in the repair of damaged offshore pipelines. Two materials were investigated, aluminum Al-6061-T6 and 304 stainless steel, which have very different ductility and work hardening characteristics. Three models, of increasing complexity were created and used to investigate the nature of the plastic deformation during the crushing and re-inflation, the punch load–displacement and pressure–volume responses and the geometric accuracy of the final tubes. The models demonstrated that for both materials, it is challenging to return the tubes to their original circular-cylindrical shape without using a suitable die for the crushing and re-inflation.