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Technical Brief

Influence of Continuous Direct Current on the Microtube Hydroforming Process

[+] Author and Article Information
Scott W. Wagner

Department of Mechanical Engineering—
Engineering Mechanics,
Michigan Technological University,
Houghton, MI 49931
e-mail: swwagner@mtu.edu

Kenny Ng

Department of Mechanical Engineering—
Engineering Mechanics,
Michigan Technological University,
Houghton, MI 49931

William J. Emblom

Department of Mechanical Engineering,
University of Louisiana at Lafayette,
Lafayette, LA 70504

Jaime A. Camelio

Grado Department of Industrial and Systems Engineering,
Virginia Polytechnic Institute and State University,
Blacksburg, VA 24061

1Corresponding author.

Manuscript received July 17, 2015; final manuscript received July 8, 2016; published online October 6, 2016. Assoc. Editor: Gracious Ngaile.

J. Manuf. Sci. Eng 139(3), 034502 (Oct 06, 2016) (5 pages) Paper No: MANU-15-1356; doi: 10.1115/1.4034790 History: Received July 17, 2015; Revised July 08, 2016

Research of the microtube hydroforming (MTHF) process is being investigated for potential medical and fuel cell applications. This is largely due to the fact that at the macroscale the tube hydroforming (THF) process, like most metal forming processes, has realized many advantages, especially when comparing products made using traditional machining processes. Unfortunately, relatively large forces compared to part size and high pressures are required to form the parts so the potential exists to create failed or defective parts. One method to reduce the forces and pressures during MTHF is to incorporate electrically assisted manufacturing (EAM) and electrically assisted forming (EAF) into the MTHF. The intent of both EAM and EAF is to use electrical current to lower the required deformation energy and increase the metal's formability. To reduce the required deformation energy, the applied electricity produces localized heating in the material in order to lower the material's yield stress. In many cases, the previous work has shown that EAF and EAM have resulted in metals being formed further than conventional forming methods alone without sacrificing the strength or ductility. Tests were performed using “as received” and annealed stainless steel 304 tubing. Results shown in this paper indicate that the ultimate tensile strength and bust pressures decrease with increased current while using EAM during MTHF. It was also shown that at high currents the microtubes experienced higher temperatures but were still well below the recrystallization temperature.

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References

Figures

Grahic Jump Location
Fig. 3

Ultimate tensile strength comparison

Grahic Jump Location
Fig. 4

Maximum temperature versus current density

Grahic Jump Location
Fig. 5

Baseline tube grain structure comparison

Grahic Jump Location
Fig. 6

Failed annealed tube

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