Vaporizing Foil Actuator Welding by Collision of Dissimilar Metals

Vaporizing Foil Actuator Welding by Collision of Dissimilar Metals

the following is a brief introduction to vaporizing foil actuator welding (VFAW) which is a specialty of the Impulse Manufacturing
Laboratory at The Ohio State University VFAW is a type of collision
welding which is a technique for joining metals by means of a
high-speed, oblique collision. Such a collision removes the
surface oxide layers from both metals and brings fresh metals
into intimate contact thereby producing a metallurgical bond.
This technique involves no heat input and no melting, so it is a type of solid-state
welding traditionally the necessary high-speed is achieved by explosives and this is
called explosion wielding. collision welding has
been shown to be capable joining a wide range of
dissimilar metal pairs which cannot be easily welded by
other means a collision welded joint is often
characterized by a wavy interface due to the turbulent
plastic flow which takes place during the welding
process. Vaporizing foil actuator welding unlike explosion welding is on a much
smaller scale and does not involve explosives. instead, it uses a piece of aluminum foil which is
cut into a dogbone shape and connected to the output end of a capacitor bank. when the capacitor
bank is discharged foil is electrically vaporized within
tens of microseconds and expanding gas from this rapid vaporization provides the driving force to propel
then sheet metal into high-speed collision with a
target plate the peak velocity of the flyer plate is
typically on the scale hundreds of meters per second. Thus this
technique is able to achieve explosive like speeds without using
explosives the setup of VFAW involves very
light tooling we start with a block of steel and a vaporizing
foil actuator is laid on top and then the flyer which is the metal
sheet to be propelled is laid on top the vaporizing foil
actuator with electrical insulation between. Plastic stand-off sheets were then put in place. the target plate which is the stationary piece of the colliding tandem is placed on top of a standoff distance away from the flyer.
finally everything is constrained by another heavy
block of steel and bolted down. below is a side view the welding process.the rapid vaporization of
the foil propels the flyer toward the target into
a high-speed collision resulting in the welded joint. The material joint made by VFAW exhibits the wavy interface
which is characteristic of collision welding, and is a similar to that
which is observed in an explosion welded joint but on a much smaller scale. the joint
exhibit the fair strength as revealed by peel testing and material
analysis at the fracture surface shows material transfer across the
interface proving that the joint failed in a
parent materials and not just along the interface. in
summary vaporizing foil actuator welding serves
as an agile way to carry out collision welding at the
laboratory-scale with fairly light tooling features comparable to those found
explosion welding are achieved without using explosives I’m on my way to the impulse metalworking lab. So we are trying to weld stainless steel with aluminum here: 304 stainless steel to 6061 aluminum in the T4 temper condition Here is our VFAW setup, connected to the terminals of the capacitor bank which is here this capacitor bank can charge up to 16 kilojoules we are going to not use of all of that we will use 8kJ. So while the flyer is accelerating we are also going to measure the velocity of that by looking
at the Flyers through this hole which has been drilled into the VFAW setup through a PDV probe alex is doing right now is aligning the
laser when he aligns the laser properly there will be a visible fluctuation on
the trace oscilloscope. and there’s the
fluctuation during the experiments, we also run some diagnostics we measure the current by using a Rogowski coil, voltage voltage by using a 1000:1 voltage divider, and the velocity of the flyer by using a laser based system called the photonic doppler velocimeter (PDV) here is our capacitor bank which has a total energy of 16 kJ. out of that we are only going to use 50% which comes out to be 8kJ in other words, it is 80 100Watt lightbulbs lit up for 1 second FIRE IN THE HOLE!! so it took the whole assembly out of the
boombox. We are about to open it up and examine our products you can see the foil is completely vaporized and what is left behind is this An aluminum and stainless steel weld beautiful professional wiggle test? yep, it’s stuck together folks, its real

4 thoughts on “Vaporizing Foil Actuator Welding by Collision of Dissimilar Metals

  1. Beauty. Keep up the good work guys, I hope you guys realize that this is one of those things that revolutionizes human history, our capacity to achieve and build greater things.

  2. BEAUTIFUL! Some forty years ago I saw Al/Steel and Al/Cu explosion welding of plates and tubes at La Plata University in Argentine.

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