Preliminary examination ofPreliminary examination ofhigh-velocity metal-shaping withhigh-velocity metal-shaping with

electrical wire explosionelectrical wire explosion

EAPPC 2006 – Speaker: Mirko WoetzelEAPPC 2006 – Speaker: Mirko Woetzel

Overview• Some remarks about explosive shaping

• Replacement of explosives by “Electro-explosives”

• Direct experimental comparison of “electro-explosives” and explosives

• Discussion of the results

Shaping with Explosives

Workpiece hits the matrix with

>100 m/s

ADVANTAGES

• Very easy to use under special conditions

• Used for prototype production

• Low tool cost

DISADVANTAGES• Use of explosives strongly

regulated by laws• Extensive safety measures• Special skilled staff • In-house production very

critical too expensive for series

production!

Shaping with Explosives

• How the advantages of explosive shaping can be used without its disadvantages?

• Approach: – Replacement of explosives by “inert” materials– Suggestion: high power arc, wire explosion

• Very well known processes• But, with respect to sheet metal shaping:

– No direct comparison of “electro-explosives” available– No direct comparison with explosives available

Shaping with Explosives

Parameters:

Different “electro-explosive” media

aluminum wire, copper wire and electrical arc

Different environments

water, oil or air

Constant electrical energy inputConstant electrical energy input

1000 Joule

Electro-explosive Shaping

Test box

20 mm(1) Aluminium – Master-Frame

(2) Teflon – Isolator of electrodes

(3) Smooth Copper – Seal

(4) Aluminium – Shaping Matrix(1)

(2)

(3)

(4)

Volume: 65 ml water, oil or air wires: 0.7 mm

C = 20 µF

VC0 = 10 kV

WC0 = 1 kJ

Energy-Supply

Energy supply

Mounting plate

Rogowski coil

Capacitor

Conductor

Test realization “electro-explosive”

Open test box

Dismantled test box Evaluation

Capacitor discharge:

Closed test box filled with water, oil or air

Metal-sheet inside

î = 30 kAf=50 kHz

primary explosive 100 mg (lead azide detonator)

explosive 185 mg

285 mg explosive with <1,3 kJ energy

Test realization “explosive”

Evaluation “electro-explosion”Evaluation “electro-explosion”

““Electro-explosive”mediumElectro-explosive”medium

Arc Copper Aluminum

Air

Oil

Water

En

viro

nm

ent

En

viro

nm

ent mmh 0

mmh 5.10

mmh 5.10

mmh 1.0

mmh 5.5

mmh 0.4

mmh 0.1

mmh 8.9

mmh 19

3

Comparison “electro-explosive” vs. explosiveComparison “electro-explosive” vs. explosiveEnvironment:Environment:WaterMaterial:Material:Explosive

mmh 20

Environment:Environment:WaterMaterial:Material:Aluminum

mmh 19

Advantages of

• no reaction with outside effects no reaction with outside effects

• no special skilled staff no special skilled staff

• easy storage and transportation easy storage and transportation

• not usable for the crime scenenot usable for the crime scene

• no toxic gasesno toxic gases

• Conclusion– An electro-explosive metal-shaping process was

investigated: Reactive Al-wire/water explosion yields the best shaping result

– At comparable energies comparable results obtained for both electro-explosive and explosive shaping procedures

– Safety aspects• Electro-explosive system=water+aluminum+voltage=

“very safe”• Explosive system=explosives+water+laws+laws+…=

“not too safe”

• Future work – Minimization of electrical energy requirements

(investment and operation cost!)– Proof of principle for large sheet metals– Automation– Introduction to industry