A Uniform Pressure Electromagnetic Actuator for Forming Flat Sheets

[+] Author and Article Information
Manish Kamal

Materials Science and Engineering Department, The Ohio State University, Columbus, OH 43210kamal.11@osu.edu

Glenn S. Daehn

Materials Science and Engineering Department, The Ohio State University, Columbus, OH 43210daehn.1@osu.edu

J. Manuf. Sci. Eng 129(2), 369-379 (Oct 04, 2006) (11 pages) doi:10.1115/1.2515481 History: Received December 12, 2005; Revised October 04, 2006

High velocity electromagnetic forming can lead to better formability along with additional benefits. The spatial distribution of forming pressure in electromagnetic forming can be controlled by the configuration of the actuator. A new type of actuator is discussed which gives a uniform pressure distribution in forming. It also provides a mechanically robust design and has a high efficiency for flat sheet forming. A simplified analysis of the actuator is presented that helps in the design of the system. Examples of uses of the actuator are then presented, specifically with regards to forming shapes and surface embossing. Some practical challenges in the design of the actuator are also addressed. This paper emphasizes the approaches and engineering calculations required to effectively use this actuator.

Copyright © 2007 by American Society of Mechanical Engineers
Topics: Pressure , Actuators
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Figure 1

CALE calculated displacement profiles of Takatsu disk (7) during deformation with a flat spiral actuator (8). The sheet is secured at its circumference.

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Figure 2

Schematic of a uniform pressure coil. The primary coil has many turns going into the depth of the paper.

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Figure 3

Construction of the 1st generation 15 turn uniform pressure actuator

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Figure 4

A 23 turn, second generation uniform pressure actuator, with a fixed outer Al channel

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Figure 5

Three-bar coil, pancake coil, and the uniform pressure actuator (arrows indicate current direction)

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Figure 6

Pressure distribution due to the different coils (3-bar coil, pancake coil, and the uniform pressure actuator, from left to right) at 0.8kJ (four Capacitors, 10% energy) on 0.13mm Cu

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Figure 7

Comparison of the peak depth obtained at 0.8kJ (four capacitors, 10% energy) by a uniform pressure (Actuator 1), pancake and 3-bar coils

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Figure 8

Variation of actuator inductance with frequency, measured with LCR bridge (Actuator 2)

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Figure 9

Schematic of the usage of Rogowski probes

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Figure 10

Primary and induced current plots in Al 5083–H18, using Actuator 2, at 4kJ (four capacitors, 50% energy). Because the actuator has 23 turns, the induced current greatly exceeds the primary

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Figure 11

The variation of peak current with root of energy in Actuators 1 and 2 with varied workpiece materials

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Figure 12

Variation in frequency with capacitance for Actuator 2 and Al 5083–H18, as developed by changing the number of capacitors in the system

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Figure 13

Variation of peak pressure with energy for Actuators 1 and 2 calculated from Eq. 12 using experimentally measured values of Ip and Ii (or estimated if that was the case)

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Figure 14

Predicted variation of peak sheet velocity with energy with Actuators 1 and 2. Key assumptions are that plastic work is not done on acceleration and the sheet is only accelerated over the first half cycle.

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Figure 15

Variation of optimal standoff with energy for Actuators 1 and 2

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Figure 16

Comparison between predicted and experimental values of the primary current for Al 5083–H18 using Actuator 2 at energy of 4kJ (four capacitors and 50% energy)

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Figure 17

(a) 5083 Al deformed at 4kJ; (b) autograde steel deformed at 4kJ (four Cap. and 50% energy)

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Figure 18

Peak induced current of two sheet materials as a function of initial energy stored in the capacitors for Actuator 1

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Figure 19

Variation of peak depth with energy for Al 2219–O using Actuator 1 (all using four capacitors)

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Figure 20

Effect of multiple capacitor discharges in forming: (a) depth contour along length of cavity; and (b) depth contour along the width of the cavity at four capacitors and 50% energy

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Figure 21

Examples of embossing onto sheet from a coin with a holographic image (about 2.5cm across) into 0.13-mm-thick soft copper sheet (left) and 0.25-mm-thick 5052-H32 sheet. Both experiments had rough vacuum on both sides of the sheet and a standoff of 2.32mm. The copper was formed at 2.4kJ; the aluminum was formed at 4.0kJ. SEM images compare the original holographic surface (electroformed nickel) and the pattern embossed in the copper (right). In both cases the entire area formed was about 100×75mm.

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Figure 22

Forming a cellphone case with 0.8mm Al alloy using the UP actuator

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Figure 23

Current density distribution along the width of the sheet at 0.2mm depth from the surface with wires of different sections; (a) sheet at a distance of 5mm from the actuator; and (b) sheet at a distance of 2mm from the actuator

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Figure 24

Current density distribution along the width of the sheet at 0.2mm depth from the surface with different wire spacing using circular sectioned wires. Al sheet was placed 5mm below the actuator



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