Joining techniques for aluminium spaceframes used in automobiles: Part I — solid and liquid phase welding

Abstract

Concerns regarding the environmental impact of motor vehicles are driving automotive manufactures to develop lighter, more fuel-efficient vehicles. Such a task is further compounded by customer demands for greater performance and more luxury and safety features, all of which tend to increase vehicle weight. Aluminium spaceframe body structures substantially reduce weight relative to traditional steel monocoques, whilst maintaining essential strength and stiffness. Such structures also present a considerable challenge for fabrication in volume production. In this two-part paper potential joining techniques are reviewed not only in terms of the physical properties of the joint produced, but also with due consideration to production issues pertinent to the automotive industry. This paper reviews solid and liquid-state welding techniques, including the conventional automotive method of spot-welding, in the context of their applicability to aluminium spaceframe structures. The capital cost of equipment, operator safety and work-place environmental issues are found to figure strongly among the many determinants governing the selection of an appropriate fabrication process. However, the ultimate success of spaceframe body structures will depend on how well the fabrication process can be shown to lend itself to volume production. The findings suggest that whichever technique(s) are eventually adopted, conventional vehicle manufacture will be considerably changed. Such change could however be minimised by retaining the traditional technique of spot-welding which, whilst no one technique emerges here as a definitive solution, remains a strong competitor.