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Research Papers

New Micro Tube Hydroforming System Based on Floating Die Assembly Concept

[+] Author and Article Information
Gracious Ngaile

Mem. ASME
North Carolina State University,
Department of Mechanical and
Aerospace Engineering,
911 Oval Drive, EB3,
Raleigh, NC 27695
e-mail: gngaile@ncsu.edu

James Lowrie

North Carolina State University,
Department of Mechanical and
Aerospace Engineering,
911 Oval Drive, EB3,
Raleigh, NC 27695
e-mail: jblowrie@ncsu.edu

Contributed by the Manufacturing Engineering Division of ASME for publication in the JOURNAL OF MICRO- AND NANO-MANUFACTURING. Manuscript received May 12, 2014; final manuscript received August 14, 2014; published online September 19, 2014. Assoc. Editor: Ulf Engel.

J. Micro Nano-Manuf 2(4), 041004 (Sep 19, 2014) (9 pages) Paper No: JMNM-14-1036; doi: 10.1115/1.4028320 History: Received May 12, 2014; Revised August 14, 2014

The advancement of micro tube hydroforming (THF) technology has been hindered by, among others, the lack of robust microdie systems that could facilitate hydroforming of complex parts that require both expansion and feeding. This paper proposes a new micro-THF die assembly that is based on floating a microdie-assembly in a pressurized chamber. The fluid pressure inside the chamber which surrounds the dies and punches is the same as the pressure required to hydroform the tube. The fluid pressure intensity in the chamber varies in accordance with the predetermined pressure loading path required to successfully hydroform the part. The system was built, and hydroforming experiments were carried out for various micro- and meso-scale shapes, including bulge-shapes, Y-shapes, and T-shapes.

Copyright © 2014 by ASME
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References

Figures

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Fig. 1

Metallic seal variants [11]

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Fig. 2

Elastomeric sealing system variants [11]

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Fig. 3

Punch-tube-die junction in conventional macro-THF

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Fig. 4

Decoupled punch-tube-die junction for expansion-driven micro-THF

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Fig. 5

Decoupled punch-tube-die junction for feed-driven micro-THF

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Fig. 6

Floating micro-THF die assembly and hydraulic fluid circuit schematic

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Fig. 7

(a) Y-shape THF simulations: Strain distribution, (b) Y-shape THF simulations: Loading paths, and (c) Y-shape THF simulations: Punch load

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Fig. 8

(a) T-shape THF simulations: Strain distribution, (b) T-shape THF simulations: Loading paths, and (c) T-shape THF simulations: Punch load

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Fig. 9

(a) Bulge-shape THF simulations: Strain distribution, (b) bulge-shape THF simulations: Loading paths, and (c) bulge-shape THF simulations: Punch load

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Fig. 10

Influence of friction and tube size on punch load

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Fig. 11

Micro-THF floating die assembly setup

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Fig. 12

1 mm and 2 mm die sets, notched punches, and punch cross section

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Fig. 13

(a) A 150 ton hydraulic press and (b) 140 MPa pressure intensifier and control circuitry

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Fig. 14 (a)

1 mm OD, L = 20 mm, feed = 1.0 mm and (b) 1 mm OD, L = 12 mm, feed 0.5 mm

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Fig. 15

(a) Wrinkle formation and buckling, 2 mm OD, P = 100 MPa, feed = 2.0 mm and (b) loading path for parts shown in Fig. 15(a)

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Fig. 16

2 mm OD, L = 12 mm, P = 100 MPa

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