Transcript Electro-explosive

Preliminary examination of
high-velocity metal-shaping with
electrical wire explosion
EAPPC 2006 – Speaker: Mirko Woetzel
Overview
• Some remarks about explosive shaping
• Replacement of explosives by “Electroexplosives”
• Direct experimental comparison of
“electro-explosives” and explosives
• Discussion of the results
Shaping with Explosives
Workpiece hits the matrix with
>100 m/s
Shaping with Explosives
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
Electro-explosive Shaping
Parameters:
Different “electro-explosive” media
aluminum wire, copper wire and electrical arc
Different environments
water, oil or air
Constant electrical energy input
1000 Joule
Test box
(1) Aluminium – Master-Frame
20 mm
(2) Teflon – Isolator of electrodes
(3) Smooth Copper – Seal
(1)
(4) Aluminium – Shaping Matrix
(2)
(3)
(4)
Volume: 65 ml water, oil or air
 wires: 0.7 mm
Energy-Supply
C = 20 µF
VC0 = 10 kV
WC0 = 1 kJ
Energy supply
Mounting plate
Rogowski coil
Conductor
Capacitor
Test realization “electro-explosive”
Open test box
Metal-sheet inside
Closed test box filled with
water, oil or air
Dismantled test box
 Evaluation
Capacitor discharge:
î = 30 kA
f=50 kHz
Test realization “explosive”
 primary explosive 100 mg
(lead azide detonator)
 explosive 185 mg
285 mg explosive with <1,3 kJ energy
Evaluation “electro-explosion”
“Electro-explosive”medium
3
Arc
Copper
Aluminum
Environment
Air
h  0 mm
h  0.1mm
h  1.0 mm
h  10.5 mm
h  5.5 mm
h  9.8 mm
h  10.5 mm
h  4.0 mm
h  19 mm
Oil
Water
Comparison “electro-explosive” vs. explosive
Environment:
Water
Material:
Aluminum
h  19 mm
Environment:
Water
Material:
Explosive
h  20 mm
Advantages of
• no reaction with outside effects
• no special skilled staff
• easy storage and transportation
• not usable for the crime scene
• no 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