Shaped metal tubes are desirable for use in automotive body assemblies due to their strength and relatively low weight. In constructing automotive body assemblies that use bent, hydroformed tubes, it is sometimes necessary to join a body member to a structural tube, wherein the body member is composed of a first material and the structural tube is composed of a dissimilar, second material. However, it is often difficult to use traditional spot welding, riveting, or bolting practices to make sheet-to-tube assemblies. It has been difficult, if not impossible, to reliably spot weld dissimilar materials such as ferrous to non-ferrous materials, particularly steel to aluminum. Such materials have significantly different melting points, which tend to render the materials incompatible for traditional resistance welding techniques, wherein the first material is to be welded directly to the second material.
Researchers at the University of Michigan have developed a method of joining dissimilar materials, in particular, for joining aluminum, magnesium, composite, and plastic components to steel components. The parts to be welded are held together under a clamping force while a self-piercing rivet is driven through the assembly by a welding electrode. The rivet pierces and passes through the non-ferrous component and into contact with the ferrous component to form a mechanical interlock. An electrical current is then applied to this mechanical retention to melt a portion of the rivet and the ferrous metal in the joining region. The flow of electrical current is stopped after several welding cycles where the now melted material is allowed to solidify upon cooling, thereby forming a weld. Electrode tooling may be used to clamp the pieces together, drive the rivet into the parts and weld the rivet to the parts, thereby consolidating the duties of specific pieces of equipment.
Applications and Advantages
- Joining dissimilar materials for assembly formation, particularly for non-ferrous to ferrous component.
- Minimal contact needed, making this process appropriate-nl-for joining of automotive body parts,-nl-which are often of complex shape.
- Economic and efficient procedure in vehicle-nl-fabrication, and specifically in automotive body-nl-assembly processes.