Tubular hydroforming of advanced steel and aluminum alloys : an economic evaluation using technical cost modeling

Abstract

Tubular hydroforming is gaining importance in the automotive industry by enabling parts consolidation, weight reduction and performance enhancement. While current automotive applications use almost exclusively mild steel, other advanced steel and aluminum alloys are being discussed for use in the future. This thesis evaluates the economics of hydroforming three representative materials - mild steel, dual phase 600 steel and aluminum 5754 - using technical cost modeling. Costs are analyzed for the entire hyclroforming value stream, from coiled metal sheets to hydrofonned components, for both geometrically equivalent and functionally equivalent hydroformed components. Design conditions of constant load to failure and constant defection are used to derive functional equivalence. Results show that manufacturing costs are most sensitive to the maximum calibration pressure required for hydroforming. While the costs of processing aluminum components are less than those of functionally equivalent steel components, greater aluminum raw material costs of lead to greater total component costs compared to steel. Substitution of advanced materials is not as cost effective a weight reduction strategy as increasing section diameter and thinning walls of mild steel components, assuming no package constraints.