Method for the production of hollow elements, hollow element, assembly piece, and follow-on composite tool for carrying out said method

A sheet metal part in accordance with 6, wherein the recessed regions (18) have a rounded concave shape or a shape converging to a point.

A component assembly comprising a sheet metal part and a functional element, with the functional element having a body part (25) with a tubular or cylindrical rivet section (24) formed thereon and the sheet metal part (10) having a raised formation (72) which is at least substantially circular in plan view, with a hole (13) having a hole margin (52) being present at the centre of the raised formation and the sheet metal surface having a recess at the side opposite the raised formation and approaching the hole margin via a convex, concave or obliquely positioned surface, wherein the free end (72) of the rivet section (24) is reshaped to a rivet bead (26) which is present at the side of the sheet metal part remote from the raised formation (50);

• wherein the rivet section (24) is crushed at the side of the sheet metal part associated with the raised formation (50) to form a ring fold (28) which traps the sheet metal part (10) between itself and the rivet bead (26) in the region of the raised formation (50) and wherein the rivet bead (26) does not project beyond the local plane (56) of the sheet metal part around the raised formation at the side of the sheet metal part opposite to the raised formation and is preferably slightly set back relative to this plane (56).

Functional element for the attachment to a sheet metal part (10) by one of a riveting process, a riveting or piercing process and a press-in process, with the sheet metal part being provided in the region of the attachment of the functional element (12) with an imprint (14), the imprint (14) manufactured prior to the attachment of the functional element (12) consists of a sequence of regions (16, 18) which are raised and recessed relative to one another, the functional element being equipped with one of rivet features, piercing and riveting features and pressing features and having no actual features providing security against rotation in the region of attachment of the sheet metal part prior to the attachment.