| 摘要 |
A tubular member having integral exterior protrusions is manufactured by providing a hollow element, for example by extrusion, having therein an axially extending interior defined by a surrounding wall having a thickness varying circumferentially. Such hollow element is positioned within a die that has therein lateral voids. The hollow element within the die is subjected, at the interior thereof, to an axially sequential deformation, for example by sequential penetration through the interior by a mandrel. This results in a non-elastic flow of the material of a thicker portion of the wall in lateral directions thereof into the voids in the die. This results in the hollow element, being formed into a tubular member having on the exterior thereof solid protrusions. |
