Characterizing materials for tube hydroforming/Two new tests help fabricators determine up-front what will work

摘要

Applications for tube hydroforming are expanding in the automotive industry because of advantages hydroforming can offer in weight reduction, part strength and stiffness, component consolidation, and dimensional accuracy. Quality control of incoming tube material is increasingly important for hydroformers as the technology expands to a greater number of applications, designs become more complex, and more varieties of material are used in the automotive industry. For tube suppliers, producing tubes with different diameter-to-thickness (D/t) ratios and from more grads and alloys to the required formability is more and more challenging. Materials used in tube hydroforming, unlike those in sheet metal forming, are subjected to a prior forming process, tube-making. Consequently, work hardening resulting from the tube-making process causes a loss of formability. Currently no standard test method exists for evaluating tubes used in hydroforming, but recently two test methods have been developed, the uniaxial ring hoop tension test (RHTT) and the cross-sectional hardness test.