the foollowing hollow shaft has a torsion applied to it so that the plastic area reaches the inner radius, what is the magnitude of the maximum residual shearing stress? http://lh3.ggpht.com/_H4Iz7SmBrbk/S9XK9ZwAbQI/AAAAAAAACFU/ueYSDTK5qMM/s800/Capture.JPG i dont see why there should be any residual stress? if the shaft entirely becomes plastic- which as far as i can tell is what happens here- why should i have any residual stress, i know that when i have an elastic core, the elastic core wants to return to its original placement and the plastic area wants to stay with its residual strain, leaving each of them a stress and the placement being somewhere inbetween. but why is this so in this case too??