of the hollow shell which is not circular with respect to the shell axis a u2033 u2032 while an oval shape of the hollow shell which serves also to improve mechanical strength at the joinder is shown at fig1 wherein l 1 gt l 2 other shapes are possible such as triangles squares hexagons etc the head 106 u2033 is connected in transverse orientation to the hollow shell 102 u2033 opposite the point 104 u2033 and overhangs the hollow shell the shape of the head may be similar to the non circular shape of the hollow shell as shown at fig1 or may be circular irrespective of the shape of the hollow shell in operation the asymmetric self piercing rivet 100 u2033 is placed at the ram of a ram and die mechanism as generally depicted at fig3 and sheets of metal or metal composite i e aluminum sheets are stacked at the die and the ram is then stroked the deformation d u2032 resulting from the ram and die mechanism driving the asymmetric self piercing rivet into the sheets may resemble that shown at fig4 except that now the non circular shape of the hollow shell is imparted to the deformation such that an.