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Path Actuators for Magnetic Pulse

Assisted Forming and Punch-lessElectro-Magnetic Shearing

A THESIS

Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in

the Graduate School of The Ohio State University

By

Scott Michael Golowin, B.S.

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Copyright By

Scott Michael Golowin

2008

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ABSTRACT

Path actuators can be fabricated very quickly and inexpensive, allowing

customized products to be brought to market very quickly. Only one sided tooling is

required, since an electro-magnetic force is used to drive the work sheet. This eliminates

high tolerance problems in matched tooling and could be implemented into a

manufacturing process. The path actuators were successfully used in net shape

calibration forming of doubly bent U channels and three shearing operations.

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The high velocity punch-less shearing method developed here minimizes burrs on

shearing and no slivers have been seen on any of the parts sheared.

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DEDICATION

This is to my Mother, Father, and Sister. They always knew what I was capable of doing

and were always a positive encouragement. Without them I would not have made it this

far.

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ACKNOWLEDGMENTS

This is a relatively long list. First and foremost I need to acknowledge my advisor

Professor Glenn Daehn, whom gave me a chance to work in this wonderful field of

Electro-Magnetic Forming (EMF). Without him, I would not have found this exciting

work environment of explosions and high speed forming, which brings excitement to my

work every day. The next people I would like to thank is my fantastic graduate group I

have worked with: Manish Kamal, Mala Seth, Jianhui Shang, Yuan Zhang, Kristen

Banik, Jacob Portier, Jonathan Evarts, Kinga Uniocic, Geoffrey Taber, Anupam Vivek,

and last but not least Kathy Babusci. These people made work enjoyable and functional.

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VITA

August 30, 1983 .......................................BornColumbus, Ohio

2006..........................................................B.S. Material Science and Engineering, The

Ohio State University

2006Present ..........................................Graduate Researching Associate, The Ohio

State University

PUBLICATIONS

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TABLE OF CONTENTS

ABSTRACT ................................................................................................................ ii

DEDICATION ............................................................................................................ iv

ACKNOWLEDGMENTS ........................................................................................... v

VITA ........................................................................................................................... vi

TABLE OF CONTENTS .......................................................................................... vii

LIST OF FIGURES ..................................................................................................... x

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CHAPTER 3 .............................................................................................................. 13

MAGNETIC PULSE ASSISTED FORMING ................................................... 13

3.1. INTRODUCTION ................................................................................ 14

3.2. EXPERIMENTAL METHOD ............................................................. 17

3.3. ANALYTICAL PROCEDURES ......................................................... 21

3.4. EXPERIMENTAL RESULTS ............................................................. 22

3.5. ANALYTICAL RESULTS .................................................................. 25

3.6. DISCUSSION ...................................................................................... 29

CHAPTER 4 .............................................................................................................. 31PUNCH-LESS ELECTRO-MAGNETIC FORMING ....................................... 31

4.1. INTRODUCTION ................................................................................ 31

4.1.1. OTHER SHEARING METHODS ............................................. 32

4.1.2. HIGH VELOCITY SHEARING ............................................... 33

4.2. EXPERIMENTAL PROCEDURES .................................................... 40

4.2.1. TWO BY TWO PROCEDURES ............................................... 40

4.2.2. ONE BY ONE PROCEDURE ................................................... 42

4 2 3 OHIO SHEARING PROCEDURE 43

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LIST OF REFERENCES .......................................................................................... 77

APPENDIX A. ........................................................................................................... 79

TWO BY TWO SHEARING DESIGN ............................................................. 79

APPENDIX B. ........................................................................................................... 82

ONE BY ONE SHEARING DESIGN ............................................................... 82

APPENDIX C. ........................................................................................................... 86

OHIO CROSS-SECTIONAL SHEARING DATA ............................................ 86

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LIST OF FIGURES

Figure 1.1: The charging circuit stores a large voltage in the capacitor bank, which is

then dumped through a coil and creates a magnetic field. Rogowski probes are used to

measure the voltage dumps. ................................................................................................ 1

Figure 1.2: The fundamental principle of EMF is shown above. (Left) shows a typical

path actuator, this particular one exerts a magnetic field in the shape of a square. Two

legs come off the bottom of the coil and one is connected to the positive, the other to

ground. When a current is passed through the actuator, the current circles the coil fromhot to ground. (Right) when a work sheet is placed in close proximity, a secondary

induced current is created circling in the opposite direction of the primary. These two

opposite force repel each other and is used in EMF. .......................................................... 3

Figure 1 3: Typical current time profiles of the primary and secondary induce current

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Figure 3.1: Shows traditional springback located at the corners of U channels and

sidewall curl from the drawing process around an edge. .................................................. 15

Figure 3.2: Schematic of springback for in-plane strain bending (Choi 2006). .............. 16

Figure 3.3: Mechanical bending setup, the punch in the center is 60 mm wide with 6 mmcorner radii. The punch moves up into the platoon bending sheet metal around the

corners of the punch. ......................................................................................................... 18

Figure 3.4: The magnetic pulse assisted forming setup was made similar to the

mechanical bending setup. The punch (60 mm wide) was embedded with a path actuatorwith 6 mm corner radii. A clamping load was applied using toggle clamps and shims

were used to adjust for material thickness. ....................................................................... 19

Figure 3.5: View of the path actuator (OFHC copper) that circles the bottom of the G10punch. The coil is closely coupled with the bottom of the doubly bent U channels, where

the force is directed into the corners. ................................................................................ 20

Figure 3.6: Setup of the magnetic pulse assisted forming with toggle clamps pressing thecoil into the corners of the U channel. .............................................................................. 20

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Figure 3.11: In plane stress (Left) mechanically bent and still in press, (Right)

springback upon removal. ................................................................................................. 27

Figure 3.12: In plane stress (Left) mechanically bent and magnetically pulse, (Right)

springback of magnetically pulsed sample. ...................................................................... 28

Figure 3.13: Bending moment through the thickness of the sheet for mechanical forming

and magnetic pulse assisted forming. The residual stresses have been alleviated........... 29

Figure 3.14: Results comparing Experiment and FEA for final springback angles in the

DP 600 in the 0.035thick sheet. ..................................................................................... 30

Figure 4.1: Configuration of experimental setup for impact shearing of the MDS

specimen (Klepaczko, 1991, 1994). .................................................................................. 35

Figure 4.2: Wide spectrum of shear strain rate for C-Cr-Mo hot-rolled steel; (a)

Maximum shear stress vs. log of shear strain rate (l/s); (b) Maximum shear strain of

localization versus log of shear strain rate (l/s) (Klepaczko and Rezaig, 1995). .............. 36

Figure 4 3: Stress conditions in Shearing Zone 39

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Figure 4.7: Blue dye is used to position the die in the center of the copper coil. (Left)

shows dye being applied to the die. (Right) shows the transfer of dye when positionedover the coil....................................................................................................................... 44

Figure 4.8: Model setup in AUTODYN simulates shearing of 1mm thick Aluminum6061-O, the refined middle section is given an initial launch velocity to simulate themagnetic repulsion of the path actuator. ........................................................................... 46

Figure 4.9: Shows increasing energy from left to right (1.6, 2.0, 2.2, & 2.4 kJ) where

only the right most sample was termed successful, the red dots show where the cross-sections were taken. .......................................................................................................... 48

Figure 4.10: The following pictures are aluminum 6061-O cross-sections of the two inch

square shearing samples: (a) Energy (E) was 1.6 kJ with an Off-Set (OS) zero, (b) E = 2.0kJ with OS = 0.010, (c) E = 2.2 kJ with OS = 0.020, (d) E = 2.4 kJ with OS = 0.030,

(e) E = 2.4 kJ with OS = 0.040, (f) E = 2.6 kJ with OS = 0.060, and (g) E = 2.4 kJ with

OS = 0.083...................................................................................................................... 50

Figure 4.11: Depicts standard PEMS cross-sections: S(roll) describes the rolloverfeature, S(shear) describes the secondary shearing zone typically a straight section where

rollover ceases, and the third or tertiary zone is noted by a burr formation or S (rupture) a

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Figure 4.14: Aluminum 6061-O cross-sections in the PEMS operation are subjected to

different measurement tools than normal mechanical sheared pieces, however the tertiaryzone is a combination of the rupture and burr zones in mechanical shearing. These two

were combined due to the insignificant amount of the zone. More often than not a

rupture zone happened to be created as large as 62m and one burr was found to be

24m................................................................................................................................. 55

Figure 4.15: The following pictures are aluminum 6061-O cross-sections of the one inch

square shearing samples: (a) Energy (E) was 1.6 kJ with an Off-Set (OS) 0.020, (b) E =

1.6 kJ with OS = 0.062, & (c) E = 2.4 kJ with OS = 0.128........................................... 56

Figure 4.16: A plot of current traces for Copper Ohio shearing shown with increasingenergy. ............................................................................................................................... 59

Figure 4.17: Successfully sheared sample that was to be sectioned in four (marked by the

lines) and to be mounted to examine the cross-sections marked by the 1, 2, 3, and 4. .... 60

Figure 4.18: Averaged results for Ohio shear samples showing percent rollover versusenergy. ............................................................................................................................... 61

i d l f hi h l h i h d h

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Figure 4.23: Autodyn FEM simulation with a launching velocity of 200 m/s was

successful. Above is a timeline of the simulation the pictures are at time: (a) 4.3 s; (b)9.4 s; (c) 14.0 s.............................................................................................................. 67

Figure 4.24: Autodyn FEM simulation with a launching velocity of 300 m/s wassuccessful. Above is a timeline of the simulation the picture are at time: (a) 4.1 s; (b)8.1 s................................................................................................................................. 68

Figure 4.25: 1 x 1 shearing coil after failure at the tap holes, in order for the screws to

provide a sufficient tie down force only a thin path remained for the current to runthrough during forming. .................................................................................................... 69

Figure 4.26: The chart depicts energy as a function of offset distance for two by two and

one by one shearing of aluminum 6061-T6. The maximum energy needed for two inchsquare shearing was 2.6 kJ (offset distance of 0.060) and one inch shearing was 2.4 kJ

(offset distance of 0.128)................................................................................................. 70

Figure 4.27: Both samples above were one inch square shears and both were formed at1.6 kJ. The sample on the (left) was formed at an offset of zero, while the sample on the(right) had an offset of 0.062........................................................................................... 71

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Figure A.1: 2 x 2 coil design (base unit inches)........................................................... 79

Figure A.2: 2 x 2 potting unit (base unit inches).......................................................... 80

Figure A.3: 2 x 2 die (base unit inches)....................................................................... 81

Figure B.1: 1 x 1 coil (base unit inches)....................................................................... 82

Figure B.2: 1 x 1 potting unit (base unit inches).......................................................... 83

Figure B.3: 1 x 1 backing unit (base unit inches)......................................................... 84

Figure B.4: 1 x 1 die (base unit inches)........................................................................ 85

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LIST OF TABLES

Table 3.1: DP 600 0.035 inches thick: list of energy, peak current, rise time, along with

measurements of initial, final and change in springback angle. ....................................... 23

Table 3.2: DP 600 0.057 inches thick: list of energy, peak current, rise time, along withmeasurements of initial, final and change in springback angle. ....................................... 24

Table 4.1: List of candidate materials for Ohio shearing................................................. 45

Table 4.2: Lowest energy required for shearing at various standoff distances. ............... 49

Table 4.3: Lowest energy shears at various standoff distances. ...................................... 57

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CHAPTER 1

INTRODUCTION

This thesis on path actuators lays out the basic fundamentals behind Electro-

Magnetic Forming and informs the reader how a path actuator can be used. Coils can be

used in magnetic pulse assisted forming to alleviate residual stresses and eliminate

springback. Lastly, it shows how coils can be used in a Punch-less Electro-Magnetic

Shearing (PEMS) operation. This type of blanking does away with clearance issues

because magnetic force is used as the punch.

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setup of a capacitor bank and a charging circuit connected to a coil. Rogowski probes are

used to capture the voltage dump profiles and can be converted into current-time profiles.

Figure 1.1: The charging circuit stores a large voltage in the capacitor bank, which is then dumped through

a coil and creates a magnetic field. Rogowski probes are used to measure the voltage dumps.

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its charge. The secondary induced current creates a loop in the opposite direction. For

the efficiency to be high, path actuators must come very close to completing a loop

themselves. To reiterate the primary current is measured using Rogowski coils, but the

secondary current in the work sheet is acknowledged as a fraction of the primary current

(seeFigure 1.3). The better the conductivity of the work sheet the higher the fraction, for

example the induced current in a sheet of Aluminum 6061 may be around 80 percent of

the primary current.

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Figure 1.3: Typical current-time profiles of the primary and secondary induce current. Notice the induced

current is a fraction of the primary and as the conductivity of the work sheet gets smaller so will the

fraction.

Current-time profiles, captured by Rogowski coils, can be used to estimate

-800

-600

-400

-200

0

200

400

600

800

1000

0 100 200 300 400

Time (microsec)

Cu

rrent(KA)

induced current

Primary current

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WhereHis the electro-magnetic field intensity, expressed in amperes per width and 0is

the permeability of free space and equals (4x 10

-7

H/m). Under the assumption that the

induced current is a fraction of the primary current equations (2) & (3) further describe

how the magnetic pressure is calculated. HerePmaxis magnetic pressure and HpandHi

represents the current densities expressed in amperes per width, in the primary and

induced circuits, respectively [2]. A constant not shown in these equations, but plays a

pivotal role, is the path actuators width. Remember, the H terms are expressed in

amperes per width, therefore, as the width is decreased the magnetic pressure increases

due to a higher current density. The induced magnetic field is calculated as a fraction of

the primary. The fraction, F, is related to the conductivity of the work sheet. As the

conductivity decreases so does the multiplying fraction.

=0

2 (2)

Hi = Hp F (3)

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either the raw material itself or the construction must be examined to reduce energy. The

path actuator is an Electro-Magnetic Forming (EMF) technique that is easy to make and

inexpensive. These coils can be used for net shape calibration and shearing.

Path actuator can be made quickly and inexpensively, being water-jet cut from

high conductivity materials like copper. Once machined coils need to be well insulated

and materials like dielectrics, glass fiber reinforced phenolics (G10), and Kapton tapes

are typically used. Most EMF coils are normally embedded in G10 for structural

integrity. Again, these can be water-jet cut negatives of the coil, which means coils and

there insulating materials can be turned around in a short time frame. The big economic

drive that makes path actuators inexpensive is one sided tooling. Since an EM force is

used in forming; only one side of the sheet comes in contact with a die. This eliminates

matched tooling required in bending and shearing operations.

Path actuators can be used to strain material at higher rates over quasi-static

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Figure 1.4: DP 600 (0.057 thick), mechanically bent U channel.

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clearance issues vanish, and more elaborate shapes can be made. The last expectation is

to create an arbitrary shape, the outline of Ohio is chosen (seeFigure 1.5).

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1.3. OBJECTIVES

The objectives of this thesis are to create working path actuators for magnetic

pulse assisted forming and PEMS. The path actuators are created from Oxygen Free

High Conductivity (OFHC) copper and are water-jet cut and machined. The main

concepts used are closely coupling the actuators to the work sheet for forming, while

keeping the designing cheap, simplistic, and product that could be linked into regular

machinery.

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CHAPTER 2

PATH ACTUATORS

Path actuators can be utilized as a very useful tool and could be implemented into

manufacturing lines. The path coil is inexpensive and simple metal forming technique. It

can also be used for a wide variety of operations, such as calibration forming, flanging,

hemming, shearing, tube expansion and compression, extended drawing, embossing, and

welding. Path actuators are simple single-turn coils in which the primary current takes on

a nearly closed-loop path and this is closely inductively coupled to the work piece. This

work piece also has a nearly-closed eddy current path. The near closures of both these

paths give relatively high efficiency to the operation In contrast to these path actuators

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energy are required. If high energies are not an option, steels can be formed using a

copper driver. Basically, the driver sheet is used to give the lower conductivity material a

proper acceleration for forming by driving it into a die.

In mechanical operations, tooling can become very expensive, especially as the

complexity increases. Mechanically formed sheet metal use highly precise matched

tooling. Besides the fact that this is costly; tooling can undergo multiple modifications to

punch and die, to fine tune for product design. In stamped parts tuning is important

because on unloading residual stresses can reopen a part. The tuning is done to meet a

final net shape requirement. With electro-magnetic calibration forming, parts may be

pressed to net shape and pulsed, adding small deformations to retain a specific shape by

alleviating the residual stresses. The coils themselves can be more easily tuned than

highly precise matched tooling sets. As mentioned before, by constricting the width of

the actuator, the current density increases and so does the generate magnetic field at that

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repulsion created by the path actuator. The path coil creates a loop and a closely coupled

work sheet creates a secondary induced loop. A magnetic repulsion is created from the

eddy currents that are induced in the work piece from the primary current in the path coil.

The primary and secondary currents run in the opposite directions. These equal and

opposite forces repel each other. This is the most important concept behind EMF and is

used to launch the sheet metal into the die for calibration forming and shearing. The

main degrees of freedom associated with EMF are current density, location of the coil

with respect to the sheet and die, and energy level. Figure 2.1 shows an example of an

arbitrary path coil, which tailors the current density for harder to form contours, such as

corners. As the width of the coil was reduced the current density increases, also

increasing the magnetic pressure exerted to the work piece.

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CHAPTER 3

MAGNETIC PULSE ASSISTED FORMING

The Ohio State University and The Edison Welding Institute joined forces on a

springback calibration project. The goal of this project was to take doubly bent U

channels and calibrate it to near right angles at the corners by adding plastic deformation

to the bent corners. The mechanical press used to bend the channels was not available,

but a goal was to see if the coil could be used in conjunction with the press. To test a

copy of the dimensions were used in creating the magnetic pulse setup. Experiments

were run in conjunction with analytical model. The material used in the trials was DP

600 a dual phase steel of thickness 0 035 and 0 057 inches The degree of freedom

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3.1. INTRODUCTION

The concept of net shape forming is usually difficult for most metallic materials.

When deforming sheet metal the outer surface is placed in tension while the inner surface

is compressed. These unequal residual stresses maintain equilibrium by springing back

open when the sheet is unloaded. This elastic recovery is termed springback and now the

part no longer meets the net shape requirements. Figure 3.1 shows traditional springback

at corners of a drawn U channel and also shows sidewall curl from drawing the sheet

metal around an edge. Companies have difficulty tuning punch and die to over bend the

sheet metal, so that, when unloaded the sheet meets the final requirements. The

companysjob is harder when the stock sheet metal changes because the tuning process

must be done again. Electromagnetic calibration can be used in net shape dies for high

tolerance parts and can be easily tuned by adjusting energy. Following example deals

with traditional springback where an electromagnetic pulse can be used to calibrate

d bl b t U h l i t th fi l t h

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Figure 3.1: Shows traditional springback located at the corners of U channels and sidewall curl from the

drawing process around an edge.

In 2006 Choi did a study on spring-back in the bending process for low carbon

steel sheet. He states the phenomenon of spring-back in the plane strain bending is

schematically described inFigure 3.2.

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Figure 3.2: Schematic of springback for in-plane strain bending (Choi 2006).

If one assumes that sheet metals exhibit elastically isotropic and an elasticideally plastic

(i.e. non-strain hardening) behavior, the amount of relative spring-back of sheet metals

having a thickness, t can be calculated from the following equation (4): where roand rf

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3.2. EXPERIMENTAL METHOD

U channels of DP 600, 0.035 and 0.057 inches thick, were mechanically bent

using the setup inFigure 3.3. The punch had a width of 60 millimeters and corner radii

of 6 millimeters. Shims were used to adjust for the thickness of the material. One goal

for this project was to design a system that could be coupled with the mechanical bending

operation. Therefore the 60 millimeter width dimension was maintained in the magnetic

pulse assisted forming arrangement and adjusted for thickness by shims, seeFigure 3.4.

The punch and coil were attached and loaded into the U channel. A downward force was

applied by toggle clamps to secure the setup. The coil was designed with 6 millimeter

radii and created a path that circled and closely coupled with the bottom and corners of

the doubly bent U channels. Figure 3.5 shows the combination of the path actuator and

punch used in the setup. Figure 3.6 shows a setup fully loaded and ready for testing.

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Figure 3.3: Mechanical bending setup, the punch in the center is 60 mm wide with 6 mm corner radii. The

punch moves up into the platoon bending sheet metal around the corners of the punch.

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Figure 3.4: The magnetic pulse assisted forming setup was made similar to the mechanical bending setup.

The punch (60 mm wide) was embedded with a path actuator with 6 mm corner radii. A clamping load was

applied using toggle clamps and shims were used to adjust for material thickness.

Clamp

Load

60 mm

Shims to

adjust forthickness

R 6 mm

Constraintbolt

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Figure 3.5: View of the path actuator (OFHC copper) that circles the bottom of the G10 punch. The coil isclosely coupled with the bottom of the doubly bent U channels, where the force is directed into the corners.

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Upon removal from the mechanical bending process, the U channels did not

conform to the 90 sidewall angles. DP 600 at 0.035 and 0.057 thickhad preformed

springback angles of 83.5 and 81.5, respectively. The method to create the desired 90

sidewall angles was using a path actuator. The main tuning variable is energy. A 16

kilojoules Magneform capacitor bank is used and adjusts in increments of 5% from

experiment to experiment. The final springback angles are plotted versus energy.

3.3. ANALYTICAL PROCEDURES

The analytical procedures were setup and completed by Peihui Zhang at The

Edison Welding Institute. The finite element analysis of the magnetic pulse assisted

forming for springback correction was performed in two steps. The first step was

modeling the electromagnetic coupling between the coil and sheet. The couple is

important to generate the magnetic pressure without loss in efficiency The second step

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The electromagnetic modeling was performed using commercial software

Magnet. 3D modeling was chosen to fully capture the current flow and force distribution

in the coil and work sheet. The coil, the work sheet, and the surrounding air were

included in the model. The estimated current waveform data was used as the input to the

coil. To estimate the current waveform, the system capacitance and inductance was used

to solve a RLC equation. To simplify the modeling process and save calculation time,

time harmonic solution was obtained. After completion of the analysis, current,

electromagnetic force, and magnetic field distributions were plotted and analyzed.

The mechanical modeling was done for two cases for results comparison. Case I

is forming of a flat sheet into U-channel and let it springback. Case II is forming of a flat

sheet into U-channel, applying magnetic pulse pressure, and removing the tooling. Both

cases were done using ABAQUS. To save computational time 3D symmetric models

were built.

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0.057 inches thick, respectively. Plotted results for DP 600 of 0.035 and 0.057

thickness are shown in Figure 3.7, which had performed angles of 83.5 and 81.5,

respectively. With a 5.6 kJ discharge an angle of 89-90 was achieved for both thickness

of material. Figure 3.8 shows a before and after picture of the EM calibrated U channel.

With a 4 kilo Joule discharge the springback in the corners was almost completely

eliminated to meet final requirements.

ID

Energy

(kJ)

Max I

(kA)

T rise

(s)Initial

left

Initial

right

Final

left

Final

right left right

30% - 8kJ 2.4 128 10.4 83.20 83.03 86.77 86.72 3.57 3.7040% - 8kJ 3.2 160 10.4 83.44 83.39 87.26 87.19 3.83 3.81

50% - 8kJ 4.0 172 8.8 83.75 83.46 87.91 87.67 4.16 4.21

60% - 8kJ 4.8 184 9.6 83.77 83.83 88.10 88.12 4.33 4.29

70% - 8kJ 5.6 200 9.6 84.13 84.01 88.98 88.86 4.85 4.85

DP 600 - 0.035" thick

Table 3.1: DP 600 0.035 inches thick: list of energy, peak current, rise time, along with measurements of

initial, final and change in springback angle.

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ID

Energy

(kJ)

Max I

(kA)

T rise

(s)

Initial

left

Initial

right

Final

left

Final

right left right

20% - 8kJ 1.6 120 9.6 81.45 81.45 87.19 87.00 5.74 5.56

30% - 8kJ 2.4 132 8.8 81.38 81.21 86.90 86.51 5.52 5.30

40% - 8kJ 3.2 136 9.6 81.41 81.35 87.58 87.19 6.16 5.84

50% - 8kJ 4.0 176 9.6 81.33 81.13 88.20 87.85 6.87 6.71

60% - 8kJ 4.8 188 9.6 81.42 81.46 88.82 88.70 7.40 7.24

DP 600 - 0.057" thick

Table 3.2: DP 600 0.057 inches thick: list of energy, peak current, rise time, along with measurements of

initial, final and change in springback angle.

84

86

88

90

92

lSpringba

ckAngle(degree)

DP 600 - 0.035" left DP 600 - 0.035" right

DP 600 - 0.057" left DP 600 - 0.057" right

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Figure 3.8: U channel in the back was before EM calibration and U channel in the front was after a 4 kJ

discharge.

3.5. ANALYTICAL RESULTS

Peihui Zhang completed the analytical modeling and comments on the results.

Figure 3.9 shows the mesh and setup of the coil and sheet in the electromagnetic

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Figure 3.9: Electromagnetic model setup showing the mesh and how the work piece and coil are coupled.

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Figure 3.11 plots the in plane stress contours of the sheet metal after being

mechanically bent and then after unloading from the machine. As shown in the figure,

the maximum stress in the U-channel is 600 MPa, and the stress was relieved after

removing of the tooling. Figure 3.12 shows the in-plane stress contours of the doubly

bent U channel after magnetic pulse forming and then after unloading from the machine.

The stress level in the grey area exceeds 600 MPa. Comparison between figures

indicates that the magnetic pulse pressure deforms more of the material into the plastic

zone, which has less elastic recovery. The stress state in the removed magnetic pulse

sample further confirms it.

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Figure 3.12: In plane stress (Left) mechanically bent and magnetically pulse, (Right) springback of

magnetically pulsed sample.

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springback can almost be completely eliminated with 100 MPa of magnetic pressure in

DP 600 0.035 thick.

Figure 3.14: Results comparing Experiment and FEA for final springback angles in the DP 600 in the

0.035 thick sheet.

0.0

1.0

2.0

3.0

4.0

5.0

6.0

84.00 85.00 86.00 87.00 88.00 89.00 90.00 91.00

Final Angle (degree)

FormingEnergylevels

(KJ)

0

20

40

60

80

100

120

M

agpulsePressure(Mpa)

Experiment-DP600

FEA simulation-DP600

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CHAPTER 4

PUNCH-LESS ELECTRO-MAGNETIC FORMING

Punch-less Electro-Magnetic Shearing (PEMS) was termed at The Ohio State

University. Mechanical shearing is present everywhere in manufacturing. Two big

problems encountered by industries are burrs and slivers. A burr is a sharp edge created

by a clearance issue. A sliver is an artifact of the shearing process, its an extra chip falls

from the sheared piece. This remnant can cause havoc on subsequent parts formed. The

goal for the PEMS operation is to eliminate clearance issues, to avoid forming burrs and

slivers. A secondary goal is to create a complex shearing shape that industry would not

attempt while staying cost efficient

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few. With an understanding of other shearing methods and relative costs and advantages,

high velocity shearing is explored and compared to the mechanical shearing process.

4.1.1. OTHER SHEARING METHODS

This discussion will be of other shearing methods such as, cookie cutter die,

simple shear tool, control panel die, laser cutting, and water-jet cutting, and of a blanking

geometry that is more complex than a simple linear shear. All of these techniques have

advantages, but each has a disadvantage as well. With a highly detailed shearing

operation, such as the outline of the state of Ohio, the matched tooling sets will have

difficulty with clearance issues. One clear trend is that burr height increases as the

clearance increases and as the blade gets duller (larger edge radius). This suggests that in

conventional shearing using the 0 cutting angle, very small clearances should provide an

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Electro Magnetic (EM) shearing offers a number of advantages over traditional

methods. It is much less equipment-intensive than laser cutting or die cutting. It can deal

well with very thin materials, whereas very precise tooling is required to shear thin

metals and can be very expensive. Also, there are opportunities for integrating forming

and shearing operations. Despite these advantages, this method has not been well

developed. However, there has been some promise shown in this area by Glouschenkov

for hollow tubular billet cropping of an aluminum alloy [6].

4.1.2. HIGH VELOCITY SHEARING

It has been shown recently, that during shear deformation imposed by a high-

velocity; plastic waves excited in a deformed material can completely change the

mechanics of plastic field. Since formulation of the rate independent theory of elasto-

plastic waves in solids by Krman, Taylor and Rakhmatulin, in the late forties and early

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chains: source of light, photodiode and input/output fiber optics [11]. This is

demonstrated inFigure 4.2,where a wide range of strain rates were tested on C-Cr-Mo

hot-rolled steel. Above a strain rate of 103 l/s a substantial increase of the maximum

shear stress is observed. On the contrary, the adiabatic localization strain increases

initially, again up to ~ 103(l/s) and next, in excess of ~ 2 x 10

4l/s, decreases rapidly [11].

The systematic drop in the critical strain of shear localization is observed for low alloy

steel around impact velocity 100 m/s. An existence of the CIV in shear was predicted by

a numerical method by Wu and Freund [3, 7, 8, 11, 12].

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It is clear that the CIV in shear is closely related with adiabatic heating and

thermal softening. The CIV in shear is caused by an instantaneous instability and strain

localization superimposed on plastic wave propagation in shear [11]. Preliminary

numerical estimation of the CIV values for 1018 steel have confirmed the usefulness of

the analytic procedure proposed by Klepaczko in 1995. The value of CIV obtained with

a simplified constitutive relation was Vcr= 98.0 m/s and c= 4.9 x 10

4

l/s for 2.0 mm

gage length, the value very close to the one determined by the MDS direct impact

technique, Vcr= 90 m/s. The experimental technique based on the MDS specimen and

direct impact has been applied so far for determination of the CIV for three steel

materials. Besides 1018 steel, the CIV determined for VAR 4340 steel (52 HRC) was

130 m/s and in the case of hot-rolled C-Cr-Mo steel 100m/s [11].

Unlike the modified double shear technique, mechanical shearing uses different

technique and equipment. Clearance is typically the number one problem in mechanical

shearing. If set to close the cutting edges bind and wear. So during a normal mechanical

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tooling. The horizontal forces result in the frictional forces FH and F'H and the

shearing forces in FVand F'V. The stress condition in the shearing zone during crack

formation is tri-axial. According to Tresca, the flow criterion is given by equation (5)

[14].

=

=

(5)

Where max is the max shear stress, while 1, 2, & f, represents the principal tensile

stress, principal compressive stress, and flow stress, respectively. During the process, the

shear yield stress increases because of the strain hardening effect. As shown in Figure

4.3, the principal stress circle enlarges until the shearing strength is reached [3]. This

strain hardening effect helps describe the morphology of the shearing cross-section. The

shearing begin but is arrested by the hardening effect, after a critical stress is reached the

rest of the shear propagates by fracture of the surface. Many simulations have been done

for the blanking process. It is considered that the crack starts in the punch-die flank at or

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Figure 4.3: Stress conditions in Shearing Zone.

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The Ohio State University developed electromagnetic shearing capability for

sheet metal cutting that should be cost effective and could find wide application in both

small precision applications, such as medical & micro devices, and could also have

significant applications in heavy-duty manufacturing, such as automotive and truck

manufacturing. The process can replace laser cutting of metal, which involves large

amount of capital investment and can also be applied to non-metal cutting, such as foam.

Furthermore, electromagnetic forming and cutting could be integrated in a single step to

save manufacturing cost. The work here will help develop a new agile sheet metal

shearing technique, for shapes not realistic by conventional methods.

4.2. EXPERIMENTAL PROCEDURES

The PEMS experiments were sectioned into three shapes. Two of the shapes were

squares of different sizes: a two by two inch and a one by one inch square The system

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electro-magnetic path actuator. Next, a set of experimental parameters were designed for

a parametric study.

The path actuators were created from OFHC copper and for structural integrity of

the coil a potting units was made from G10. The coil and potting unit were both water-jet

cut. Next, a shearing die was wire EDM from mild steel and was positioned in the center

of path actuators width. This creates a magnetic pressure under the shearing edge.

Figure 4.5 shows the layout of how the coil, supporting unit and die come together. Half

inch alignment holes were used for position and bolts were used for a clamping force.

CAD drawings of the coil, potting unit, and die can be found in Appendix A (Figure A.1,

Figure A.2,&Figure A.3,respectively).

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With the design completed, a list of variables was selected for a parametric study.

Energy was used as the main variable for shearing. A Magneform 16 kilojoules bank was

used for shearing; this was adjusted in increments of 2.5% from experiment to

experiment. The second variable studied was standoff distance. The standoff was

measured as the distance from the work sheet to the shearing die; this was created using

steel shims. The last variable was material: aluminum 6061-T6, aluminum 6061-O and

copper 101. All materials were one millimeter thick.

4.2.2. ONE BY ONE PROCEDURE

The one by one inch square shearing procedures were conducted as follows. This

second set of experiments was setup to examine an energy level effect for a smaller

square shape. The coils were designed similar to the two by two experiments, having the

same coil width and corner radii. This kept the current densities similar when using the

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of 5% of the bank. The standoff distance was also varied using steel shims at alignment

pins. The material list was aluminum 6061-T6, aluminum 6061-O and copper 101.

4.2.3. OHIO SHEARING PROCEDURE

The Ohio shearing setup was constructed slightly different than before. Materials

remained the same. The coil was made from OFHC copper, while the potting unit and

backing plates were made from G10. The Ohio die was wire EDM from 4340 stainless

steel. The die was scaled to one inch east to west across the border of Ohio (seeFigure

1.5). The coil was created by a smoothed scale drawing of the outline of Ohio. This

eliminated sharp edges which can potentially cause arcing. The outer perimeter was

made an eighth inch larger and the inner perimeter was made an eighth inch smaller (see

Figure 4.6). Tapped holes were placed in the back and the die was attached to a second

plate, which contained alignment holes. Blue dye was used to position the dies cutting

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Figure 4.6: The highly detailed wire EDM Ohio shearing die is shown, laid over the smooth water-jet cut

copper coil an eighth inch of the dies cutting edge.

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Once the die is aligned and with the square shearing studies completed. The

results were used to create the Ohio shearing parameters. Energy was chosen as the only

variable. Again, the 16 kilojoules Magneform capacitor bank is adjusted each experiment

in increments of 5%. Once the critical shearing energy is achieved two more parts are

formed at higher energy. This was done to compare the cross-sectional changes in

rollover, secondary shearing zone, and the tertiary zone at increasing energies. The Ohio

shearing trial used a larger subset of materials and is shown in Table 4.1.

Material Density(g/cc)

ElectricalConductivity

(1/cm)

YoungsModulus

(GPa)

YieldStrength

(MPa)

Mg AZ31B-O 1.77 1.09E+05 45 150

Mg AZ31B-H24 1.77 1.09E+05 45 220

Al 6061-O 2.70 2.73E+05 69 55

Al 6061-T6 2.70 2.51E+05 69 276

Al 3003-H24 2.73 2.40E+05 69 145

Al 3003-O 2.73 2.87E+05 69 41

Cu 101 8.90 5.85E+05 115 69-365

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platform for analysis was AUTODYN, interactive non-linear dynamic analysis software.

To save run time a half 2-D model with respect to symmetry was setup to model the one

by one inch shearing (seeFigure 4.8). The sheet was created by joining three sections.

The middle section was designed to be directly position above the coil and was give the

same width. Meshing in this middle section was more refined and given the initial launch

conditions created by the magnetic pressure. Then modeling was run at launch velocities

of 150, 200 & 300 m/s at a zero offset distance. This in return gave a critical velocity for

shearing and cross-sectional characteristics.

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The FEM simulations were setup to demonstrate shearing of Aluminum 6061-O.

The material properties were selected from the database to imitate the experiment. A

Shock equation of state was selected to model the impact from the launch velocity. Next,

a Johnson-Cook strength model (5) was chosen to better accurately describe the yield

stress, when the material experienced work hardening and/or strain hardening.

= + + (6)

Where A, B, and Cwere constants, which were set as 0, 500 MPa, and 0 respectively.

With these constants, the yield stress changes as a function of plastic strain, p, and the

work hardening exponent, n, was set as 0.25. Effects from thermal input were ignored.

Lastly, plane stress and plane strain erosion criteria were implemented. If an element in

the worksheet reaches either a critical stress of 400 MPa or a strain of 0.75, the element

was removed.

4 4 EXPERIMENTAL RESULTS

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induced current in aluminum is assumed to be 80% of the primary current. The lowest

magnetic pressure needed for shearing 270 MPa for aluminum 6061 at a zero standoff

distance. Figure 4.10 shows cross-sections of the two inch square shears. The samples

are laid out as follows: each picture contains two cross-sections both from the same

sample, the bottom piece in each picture is from the side, the piece above is from the top

edge of the sample, & the shearing direction was always oriented in the upward direction.

The figure shows what were termed successful shear for each standoff distance (zero,

0.010, 0.020, 0.030, 0.040, 0.060, & 0.083 inches).

Off-set of 0.030 increase energy from left to right (1.6, 2.0, 2.2, 2.4 kJ)

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2 x 2

Squares

Energy

(kJ)

Standoff

(in)

Peak Current

(kA)

Rise Time

(s)

Pmax

(MPa)

Al 6061 1.6 0.000 116 9.6 270

Al 6061 2.0 0.010 128 9.6 329

Al 6061 2.2 0.020 134 9.6 361

Al 6061 2.4 0.030 140 9.6 394

Al 6061 2.4 0.040 138 9.6 383

Al 6061 2.6 0.060 140 9.6 394

Al 6061 2.4 0.083 136 9.6 372

Table 4.2: Lowest energy required for shearing at various standoff distances.

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(a) (b)

(c)

(e) (f)

(d)

(g)

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The PEMS cross-sections take on a different morphology than mechanically

sheared operation. Figure 4.11 classifies the notation that was used to describe the cross-

sections. It was note worthy, that the rupture zone, a classic shearing characteristic, was

not seen in the majority of the PEMS operation. Therefore, the following picture

describes the high velocity shearing with a rollover, secondary, and tertiary zone. The

tertiary zone was considered a rupture or burr feature. None of the two by two PEMS

samples contained any significant burr. This was tested using a cotton bag, if a burr was

present, with sharp and cutting features; fibers of cotton would be pulled from the cotton

ball. This is a simple test used in some industrial practices. Also no slivers were present

after the shearing operation. The cross-sections depicted nearly 100% combination of

edge rollover and secondary shearing zone. The tertiary zone was negligible in most

samples. Figure 4.12, Figure 4.13, & Figure 4.14 show plots of percent rollover, percent

secondary shear, and the tertiary value, respectively.

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Figure 4.11: Depicts standard PEMS cross-sections: S(roll) describes the rollover feature, S(shear)

describes the secondary shearing zone typically a straight section where rollover ceases, and the third or

tertiary zone is noted by a burr formation or S (rupture) a rupture zone similar to mechanical shearing.

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Figure 4.12: Aluminum 6061-O cross-sections in the PEMS operation are subjected to different

measurement tools than normal mechanical sheared pieces, however the rollover zone is present in bothand the PEMS cross-sections show up to 42% rollover and little at 15% depending on offset (OS) distance

and energy.

0%

5%

10%

15%

20%

25%

30%

35%

40%

45%

50%

0.0 0.5 1.0 1.5 2.0 2.5 3.0

%Rollover

Energy (kJ)

OS=0.010" OS=0.020" OS=0.030" OS=0.040" OS=0.060" OS=0.083"

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Figure 4.13: Aluminum 6061-O cross-sections in the PEMS operation are subjected to different

measurement tools than normal mechanical sheared pieces, however the secondary zone or sheared zone

are similar. However the PEMS secondary zone often occurs at an angle to the shearing of 65 to 85compared to the normal perpendicular cuts in mechanical shearing. The PEMS operation shows 58% to

84% of the cross-section to be the secondary shearing zone.

50%

55%

60%

65%

70%

75%

80%

85%

90%

95%

100%

0.0 0.5 1.0 1.5 2.0 2.5 3.0

%Shear

Energy (kJ)

OS=0.010" OS=0.020" OS=0.030" OS=0.040" OS=0.060" OS=0.083"

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Figure 4.14: Aluminum 6061-O cross-sections in the PEMS operation are subjected to different

measurement tools than normal mechanical sheared pieces, however the tertiary zone is a combination of

the rupture and burr zones in mechanical shearing. These two were combined due to the insignificantamount of the zone. More often than not a rupture zone happened to be created as large as 62m and one

burr was found to be 24m.

-80

-60

-40

-20

0

20

40

60

80

0.0 0.5 1.0 1.5 2.0 2.5 3.0

TertiaryZone(m)

Energy (kJ)

OS=0.010" OS=0.020" OS=0.030" OS=0.040" OS=0.060" OS=0.083"

BURRFORMATION

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direction. This was similar to how the cross-sections were taken from the two by two

samples. All of the samples contain no significant burr, and no slivers were ever present

after PEMS operation. The operation depicts nearly 100% combination of edge rollover

and secondary shearing zone. The tertiary zone was negligible in most samples. Table

4.3 shows the lowest energy needed for a successful shear for the various standoff

distances, along with peak current, rise time, and magnetic pressure exerted. For the

annealed aluminum samples between zero and 0.062 inches standoff, a magnetic pressure

under 400 MPa was required for shearing.

(a) (a)(b)

(c)

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1 x 1

Squares

Energy

(kJ)

Standoff

(in)

Peak Current

(kA)

Rise Time

(s)

Pmax

(MPa)

Al 6061-O 1.6 0.000 140 14 394

Al 6061-O 1.6 0.010 136 12 372

Al 6061-O 1.6 0.020 138 12 383

Al 6061-O 1.6 0.062 136 12 372

Al 6061-O 2.4 0.128 164 12 541

Table 4.3: Lowest energy shears at various standoff distances.

4.1.3. OHIO SHEARING RESULTS

The Ohio shearing results are complied inTable 4.4,showing energy level, peak

current, rise time, and listing for a successful shear or not. Figure 4.16 shows the

recorded current traces, captured by a Rogowski coil for increasing energy in the copper

samples. The Rogowski loops the path actuator and records the voltage running through

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Material Thickness(in)

Energy(kJ)

Peak Current(kA)

Rise Time(s)

SuccessfulShear

1 Alum 0.0250 4.0 208 11.2 yes

2 Alum 0.0250 4.8 246 10.9 yes

3 Alum 0.0250 5.6 262 11.2 yes

4 Alum 0.0250 3.2 206 10.7 no

1 Copper 0.0200 4.0 221 10.9 no2 Copper 0.0200 4.8 248 10.6 yes

3 Copper 0.0200 5.6 265 10.6 yes

4 Copper 0.0200 6.4 279 10.9 yes

1 Silver 0.0120 3.2 212 10.8 yes

2 Silver 0.0120 2.4 183 10.8 yes

3 Silver 0.0120 1.6 150 10.6 no

4 Silver 0.0120 4.0 228 10.9 yes1 Al 6061-T6 0.0250 4.0 - - no

2 Al 6061-T6 0.0250 4.8 233 11.5 no

3 Al 6061-T6 0.0250 5.6 253 11.1 yes

4 Al 6061-T6 0.0250 6.4 268 11.9 yes

5 Al 6061-T6 0.0250 7.2 290 11.9 yes

1 Al 3003 0.0230 4.0 219 11.3 no

2 Al 3003 0.0230 3.2 199 10.7 no3 Al 3003 0.0230 4.0 218 11.1 yes

4 Al 3003 0.0230 4.8 239 11.9 yes

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Figure 4.16: A plot of current traces for Copper Ohio shearing shown with increasing energy.

The successfully sheared samples were then sectioned and mounted for cross-

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The secondary shear zone was just under half of the material thickness. Most of the

cross-sections recorded no burr formation; however a few samples had the presence of a

small burr. The largest burr recorded was 60 micrometers in Aluminum 6061-T6 (see

Figure 4.21). The majority of the samples lay between burr lengths of 5 to 25

micrometers, barely noticeable to touch and rarely sharp.

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Figure 4.18: Averaged results for Ohio shear samples showing percent rollover versus energy.

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0

PercentRollover

Energy (kJ)

Alum Copper Silver Al 6061-T6 Al 3003-H24 Mg AZ31-O Mg AZ31-B

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Figure 4.19: Averaged results for Ohio shear samples showing the secondary shear zone percentage versus

energy.

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0

PercentSecondary

ShearZone

Energy (kJ)

Alum Copper Silver Al 6061-T6 Al 3003-H24 Mg AZ31-O Mg AZ31-B

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Figure 4.20: Averaged results for Ohio shear samples showing the tertiary zone versus energy.

-35

-25

-15

-5

5

15

25

35

1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0

TertiaryZon

e(m)

Energy (kJ)

Alum Copper Silver Al 6061-T6 Al 3003-H24 Mg AZ31-O Mg AZ31-B

BURR

FORMATION

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Figure 4.21: Aluminum 6061-T6 sheared at 6.4 kJ contained a burr 60 m in length and was taken at 5X

magnification from zone #1.

4.5. ANALYTICAL RESULTS

The modeling was arranged so that a segment of the work piece, no larger than

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determined to be between 150 to 200 m/s. Klepaczko studies were on various steels. He

showed a CIV less than 100 m/s for 1018 steel. However, Klepaczkos approach was

accomplished with impacts by projectiles. This suggests an added mass was used to help

with the shearing process and would effectively reduce the velocity. The PEMS

operation used no projectiles for shearing and would require a higher critical shearing

velocity if the same materials were in question.

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(a)

(d)

(b)

(f)(e)

(c)

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Figure 4.23: Autodyn FEM simulation with a launching velocity of 200 m/s was successful. Above is a

timeline of the simulation the pictures are at time: (a) 4.3 s; (b) 9.4 s; (c) 14.0 s.

(a) (b)

(c)

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Figure 4.24: Autodyn FEM simulation with a launching velocity of 300 m/s was successful. Above is a

timeline of the simulation the picture are at time: (a) 4.1 s; (b) 8.1 s.

4.6. DISCUSSION

The path actuators used for shearing were slightly modified from setup to setup.

These modifications were done to increase the coils lifetime. The two by two square

shearing coil and potting unit were made from different thicknesses of material The

(a) (b)

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and it eventually broke at the legs (seeFigure 4.25). This coil failure could be avoided

by not running the tap holes as deep or using a thicker copper plate. The Ohio shearing

did not encounter any new types of modifications but used the gathered knowledge. The

coil and potting unit were created from similar sized materials, and a backing plate was

used but without the tap holes. At this point of the experiments it was known that zero

standoff gave the best results, and the clamping force of the die restricted the coil from

distorting in-plane thus adding to its lifetime.

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was at a minimal standoff distance; this was zero during trials (Figure 4.26). However,

the one inch square shearing presented no significant difference for zero standoff to a

0.062 inch offset; except a more noticeable texture was picked up from the dies surface

and slight bump formation from the coil (see Figure 4.27). For the two inch square

shearing as the offset distance was increased so was the energy required for a successful

cut. The SS 304 was not successfully sheared. The energy required to begin shearing a

single corner began to warp and distort the path actuators. Therefore, those trials were

stopped.

1.5

2.0

2.5

3.0

ergy

(kJ

)

Two Inch Square Shearing One Inch Square Shearing

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Figure 4.27: Both samples above were one inch square shears and both were formed at 1.6 kJ. The sample

on the (left) was formed at an offset of zero, while the sample on the (right) had an offset of 0.062.

Mechanically sheared pieces typically have a burr and slivers, which are bad in

the manufacturing world. Burrs must be removed are hidden during assembly. These

features arise from a clearance issue between the shearing blades. A rule of thumb is the

larger the clearance the larger the burr. Figure 4.28 shows two cross-sectional

i h f h i ll h d l i l l d

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Figure 4.28: The micrographs above are cross-section views of mechanically sheared aluminum 6061-T6;

(the left) was done on a mechanical shearing machine with a 0.004 clearance, burr height 101m; (the

right) was done by a mechanical pressing using a urethane pad to drive the sheet into the die, burr height

150m.

Figure 4.29 shows sheared samples of the one by one setup with increasing

energy. Figure 4.30 shows a blown up view of the modeling done in conjunction. From

the modeling as the velocity (energy) increased it was expected there would be some

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Figure 4.29: Aluminum shearing, 1 mm thick increasing energy from bottom to top (1.6, 2.0, 2.4, & 2.8 kJ)

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CHAPTER 5

CONCLUSIONS

The path actuators can be fabricated very quickly and inexpensively. Only one

sided tooling is required, since an electro-magnetic force is used to drive the work sheet.

This eliminates high tolerance problems in matched tooling and could be implemented

into a manufacturing process. The path actuators were successfully used for net shape

calibration forming and shearing. The main degrees of freedom were the energy level,

coil with respect to the work sheet and die, and tailored current density.

The path actuator used for calibration forming required tuning of one variable, the

energy to alleviate residual stresses in the material. For both thicknesses of DP 600

(0.035 and 0.057 inches), the doubly bent U channels were formed to 89-90 sidewall

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create a magnetic pressure on both sides of a shearing edge. From results of the two by

two and one by one square shearing setups, a zero offset distance showed the most

promise, shearing at the lowest energy and providing the least distortion. Figure 5.1

shows an energy level effect versus standoff distance, as the standoff increased so does

the energy for shearing. Also, as the standoff increases more of a bump formation is

observed. This was a direct response to the location of the coil below. When passing

similar current densities through the two by two and one by one inch square shearing

coils, a minimal amount of extra energy was required for the scaled up shearing. This

was because the coil had a lower inductance by a removal of 4 out of 8 caps in the

capacitor bank. Lastly, PEMS can be used for more complex shapes, without high

tolerance issues. In most cases large burr formations were avoided and silvers were

never present.

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Figure 5.1: Aluminum 6061-T6 and copper 101.

Standoff Distance

zero

0.010

0.020

0.062

0.128

0.113

2.5kJ 5kJ 7.5kJ 10kJ 12.5kJ 15kJ

Energy Level

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LIST OF REFERENCES

1. Daehn, G.S.,High-Velocity Metal Forming.Forming Processes for Sheet, Strip,

and Plate: p. 406-418.

2. Kamal, M.,A Uniform Pressure Electromagnetic Actuator for Forming Flat

Sheet, inMaterial Science and Engineering. 2005, The Ohio State University:

Columbus. p. 82-94.

3. Grnbaum, M.,Influence of High Cutting Speeds on the Quality of Blanked Parts.

1996, NSF Engineering Research Center for Net Shape Manufacturing, The OhioState University.

4. Choi, S.-H. and K.-G. Chin,Prediction of Spring-Back Behavior in High StrengthLow Carbon Steel Sheets.J. of Mat. Proc. Tech., 2006. 171: p. 385-392.

5. Li, M.,An Experimental Investigation on Cut Surface and Burr in TrimmingAluminum Autobody Sheet.Int. J. of Mech. Sciences, 2000. 42: p. 889-906.

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10. Klepaczko, J.R.,Plastic Shearing at High and Very High Strain Rates.Les

Editions de Physique Les Ulis, J. Phys.(France) IV(France), 1994. 4: p. 35-40.

11. Klepaczko, J.R.,Remarks on Impact Shearing.J. of the Mech. and Phys. of Sol.,1998. 46(10): p. 2139-2153.

12. Wu, F.H. and L.B. Freund,Deformation Trapping Due to Thermoplastic

Instability in One-Dimensional Wave Propagation.J. Mech. Phys. Sol., 1984.

32(2): p. 119-132.

13. Lange, K.,Blanking and Piercing Handbook of Metal Forming. 1985: McGraw-

Hill Book Company. 1216.

14. Lange, K., Umformtechnik III. Blechbearbeitung.Vol. 3. 1990, Berlin,

Heidelberg, New York: Springer.

15. Faura, F., A. Garcia, and M. Estrems,Finite Element Analysis of OptimumClearance in the Blanking Process.J. of Mat. Proc. Tech., 1998(80-81): p. 121-

125.

16. Hatanaka, N., K. Yamaguchi, and N. Takakura,Finite Element Simulaton of theShearing Mechanism in the Blanking of Sheet Metal.J. of Mat. Proc. Tech.,

2003(139): p. 64-70.

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APPENDIX A.

TWO BY TWO SHEARING DESIGN

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APPENDIX B.

ONE BY ONE SHEARING DESIGN

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Figure B.4: 1 x 1 die (base unit inches).

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APPENDIX C.

OHIO CROSS-SECTIONAL SHEARING DATA

Material

Energy

(kJ)

Rollover Section Secondary Section Tertiery Section

1 2 3 4 ave 1 2 3 4 ave 1 2 3 4 ave

Alum 4.0 0.438 0.521 0.583 0.667 0.552 0.563 0.479 0.417 0.333 0.448 -24 0 -24 -12 -15

Alum 4.8 0.474 0.647 0.681 0.686 0.622 0.526 0.353 0.319 0.314 0.378 -24 -48 -24 0 -24Alum 5.6 0.575 0.658 0.695 0.583 0.628 0.425 0.342 0.305 0.417 0.372 -12 0 -12 -24 -12

Copper 4.8 0.665 0.733 0.651 0.571 0.655 0.335 0.267 0.349 0.429 0.345 -12 0 0 0 -3

Copper 5.6 0.713 0.742 0.652 0.719 0.706 0.287 0.258 0.348 0.281 0.294 -18 0 0 -18 -9

Copper 6.4 0.716 0.737 0.663 0.646 0.690 0.284 0.263 0.337 0.354 0.310 0 0 0 0 0Silver 2.4 0.571 0.381 0.391 0.474 0.454 0.429 0.619 0.609 0.526 0.546 0 0 0 -12 -3Silver 3.2 0.524 0.500 0.429 0.386 0.459 0.476 0.500 0.571 0.614 0.541 -12 0 0 0 -3

Silver 4.0 0.571 0.391 0.565 0.652 0.545 0.429 0.609 0.435 0.348 0.455 -24 0 0 0 -6

Al 6061-T6 5.6 0.472 0.382 0.400 0.222 0.369 0.528 0.618 0.600 0.778 0.631 -24 0 0 -24 -12Al 6061-T6 6.4 0.480 0.308 0.451 0.431 0.418 0.520 0.692 0.549 0.569 0.582 -60 0 0 0 -15

Al 6061-T6 7.2 0.434 0.358 0.389 0.481 0.416 0.566 0.642 0.611 0.519 0.584 -12 0 0 -24 -9

Al 3003 4.0 0.604 0.500 0.596 0.604 0.576 0.396 0.500 0.404 0.396 0.424 -24 0 -36 -24 -21

Al 3003 4.8 0.739 0.702 0.771 0.804 0.754 0.261 0.298 0.229 0.196 0.246 -24 -12 -36 -36 -27

Al 3003 5.6 0.667 0.245 0.837 0.612 0.590 0.333 0.755 0.163 0.388 0.410 -24 36 -24 -36 -12

Mg AZ31-O 3.2 0.671 0.480 0.500 0.518 0.542 0.329 0.520 0.500 0.482 0.458 -48 0 0 0 -12

Mg AZ31-O 4.0 0.784 0.571 0.647 0.581 0.646 0.216 0.429 0.353 0.419 0.354 -48 0 0 -12 -15

Mg AZ31-O 4.8 0.591 0.622 0.554 0.598 0.591 0.409 0.378 0.446 0.402 0.409 -48 0 0 0 -12Mg AZ31-B 3.2 0.596 0.560 0.707 0.732 0.649 0.404 0.440 0.293 0.268 0.351 -12 0 0 -36 -12

Mg AZ31-B 4.0 0.590 0.446 0.512 0.509 0.514 0.410 0.554 0.488 0.491 0.486 0 0 24 0 6Mg AZ31-B 4.8 0.434 0.634 0.585 0.519 0.543 0.566 0.366 0.415 0.481 0.457 0 0 48 0 12

Table C.1: Ohio PEMS samples broken into fractional Rollover, Secondary Shear Zone fraction, and Tertiary Zone (m), by zone number and averaged.

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