A system and method of friction welding a workpiece. A curl forming die may be disposed proximate a first part and a second part. The curl forming die may form a curl that is generated when the first part is friction welded to the second part.

A joining method for joining a first member having a hole that is opened on at least one surface, to a second member including a material of which a melting temperature is lower than that of a constituent material of the first member, includes: laminating the second member on the first member so as to cover an opening of the hole; and introducing that material of the second member which is softened or melted into the hole through the opening and curing the material of the second member.

A method and an assembly use two copper sheets, which are connected to each other by a screw connection. The screw connection is performed by a screw that is screwed directly into the copper sheets without screw holes having been provided. Therefore the production tolerances for preset screw holes can be dispensed with.