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Research Papers

Experimental Investigation of Tensile Properties of SS316L and Fabrication of Micro/Mesochannel Features by Electrical-Assisted Embossing Process

[+] Author and Article Information
Linfa Peng

Shanghai Key Laboratory of Digital Manufacture for Thin-Walled Structures,
Shanghai Jiao Tong University,
Shanghai 200240, China;
State Key Laboratory of Mechanical
System and Vibration,
Shanghai Jiao Tong University,
Shanghai 200240, China

Jianming Mai, Tianhao Jiang

Shanghai Key Laboratory of Digital Manufacture for Thin-Walled Structures,
Shanghai Jiao Tong University,
Shanghai 200240, China

Xinmin Lai

State Key Laboratory of Mechanical
System and Vibration,
Shanghai Jiao Tong University,
Shanghai 200240, China
e-mail: xmlai@sjtu.edu.cn

Zhongqin Lin

State Key Laboratory of Mechanical
System and Vibration,
Shanghai Jiao Tong University,
Shanghai 200240, China

1Corresponding author.

Contributed by the Manufacturing Engineering of ASME for publication in the JOURNAL OF MICRO- AND NANO-MANUFACTURING. Manuscript received June 16, 2013; final manuscript received February 10, 2014; published online March 24, 2014. Assoc. Editor: Ulf Engel.

J. Micro Nano-Manuf 2(2), 021002 (Mar 24, 2014) (11 pages) Paper No: JMNM-13-1051; doi: 10.1115/1.4026884 History: Received June 16, 2013; Revised February 10, 2014

During the electrical-assisted forming process, a significant decrease in the flow stress of the metal is beneficial to reduce the required force for the deformation with high-density electrical current introduced through the materials. It is an alternative manufacturing process of traditional hot forming to improve the formability without the undesirable effects caused by elevated temperature, such as surface oxidation. In this study, tension tests and electrical-assisted embossing process (EAEP) experiments were performed to study the electroplastic (EP) effect with high-density pulse current applied to the specimen and demonstrate the advantage of EAEP. In the first section of this study, specimens with various grain sizes were well prepared and an experimental setup was established to study the flow stress of SS316L sheet in the electroplastic tensile test. Extra cooling system was developed and the temperature increase caused by resistive heating was controlled. Thermal influence caused by resistive heating was thereby reduced. The impacts of the pulse current parameters on the flow stress were investigated. It was observed that the flow stress of the SS316L specimens was significantly reduced by the electroplastic effect. In the second section, the EAEP was proposed to fabricate microchannel feature on metal workpiece. Experiments were conducted to demonstrate the feasibility and advantage of the novel process. The protrusion feature height and microstructure of the grain deformation were measured to investigate the effect of the process parameters, such as the current density, the die geometric dimension, and the grain size of the specimen. Larger feature height was measured owing to the higher density current, which meant the electroplastic effects were helpful in EAEP.

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References

Figures

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Fig. 1

The grain structure of the stainless steel specimens: (a) as-received, (b) heat treatment at 1050 °C, and (c) heat treatment at 1150 °C

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Fig. 2

The schematic and picture of tensile specimen (mm)

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Fig. 3

Electric-assisted tensile experiments: (a) experimental facilities and (b) tensile specimen

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Fig. 4

True stress–strain curves for various current densities: (a) as-received 15 μm, (b) 30 μm grain size, and (c) 110 μm grain size

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Fig. 8

Schematic diagram of embossing system

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Fig. 9

Dies for embossing experiments

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Fig. 7

Flow stress for varying grain sizes with different current densities: (a) true strain 0.05 and (b) true strain 0.2

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Fig. 5

Flow stress reduction (30 μm grain size)

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Fig. 17

Grain deformation of stainless steel specimen: (a) 15 μm grain size and (b) 110 μm grain size

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Fig. 10

Reaction force–displacement curves (grain size 30 μm)

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Fig. 11

3D image results of the embossed workpiece (1.0 mm channel width): (a) 0 A/mm2 and (b) 50 A/mm2

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Fig. 12

Protrusion heights for 30 μm grain size sample

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Fig. 6

Flow stress–strain for varying current densities (30 μm grain size)

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Fig. 13

3D scan results of the embossed parts (0.5 mm channel width): (a) 0 A/mm2 and (b) 50 A/mm2

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Fig. 14

Effect of channel width on feature height at various loads: (a) 0 A/mm2 and 20 A/mm2 and (b) 10 A/mm2 and 50 A/mm2

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Fig. 15

Grain deformation of stainless steel specimen: (a) 0.5mm channel width and (b) 1.0 mm channel width

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Fig. 16

Effect of the specimen grain size on feature height at various loads: (a) 0 A/mm2 and 20 A/mm2 and (b) 10 A/mm2 and 50 A/mm2

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Fig. 18

Feature increment ratio at various grain sizes (0 A/mm2 and 50 A/mm2)

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