Functional element for a fluid-tight attachment to a sheet metal part, component assembly and method

A functional element (10) having a section (16) that has a flange (12), that projects away from a side (14) of the flange (12), and that is adapted for an aperture-free punching into a sheet metal part (72) and having a shaft part (20) that projects away from a side (18) of the flange (12) opposite the first side (14), that satisfies a function, and that has a longitudinal axis (22), wherein the flange (12) and the section (16) are arranged at least substantially coaxially to the shaft part (20), wherein the section (16) is configured as a hollow cylinder that has notches (26 and 26′) extending in parallel with the longitudinal direction at at least one of its outer jacket surface and its inner jacket surface and the section (16) has a diverging frustoconical shape (34) that runs out at least substantially at the free end (28) and that serves for the widening of the section (26) on the punching into the sheet metal part in the region of its free front 20 end (28) on the inner side preferably in a region (32) directly adjacent to the free end (28) of the section.