Electric heating – Metal heating – By arc
Patent
1998-04-17
2000-11-21
Ryan, Patrick
Electric heating
Metal heating
By arc
21912169, 21912167, B23K 2600
Patent
active
061506303
ABSTRACT:
The invention consists of a method for machining (cutting, drilling, sculpting) of explosives (e.g., TNT, TATB, PETN, RDX, etc.). By using pulses of a duration in the range of 5 femtoseconds to 50 picoseconds, extremely precise and rapid machining can be achieved with essentially no heat or shock affected zone. In this method, material is removed by a nonthermal mechanism. A combination of multiphoton and collisional ionization creates a critical density plasma in a time scale much shorter than electron kinetic energy is transferred to the lattice. The resulting plasma is far from thermal equilibrium. The material is in essence converted from its initial solid-state directly into a fully ionized plasma on a time scale too short for thermal equilibrium to be established with the lattice. As a result, there is negligible heat conduction beyond the region removed resulting in negligible thermal stress or shock to the material beyond a few microns from the laser machined surface. Hydrodynamic expansion of the plasma eliminates the need for any ancillary techniques to remove material and produces extremely high quality machined surfaces. There is no detonation or deflagration of the explosive in the process and the material which is removed is rendered inert.
REFERENCES:
patent: 4826785 (1989-05-01), McClure et al.
patent: 5656186 (1997-08-01), Mourou et al.
patent: 5683366 (1997-11-01), Eggers et al.
Banks Paul S.
Myers Booth R.
Perry Michael D.
Sefcik Joseph A.
Stuart Brent C.
Elve M. Alexandra
Ryan Patrick
The Regents of the University of California
Thompson Alan H.
Wooldridge John P.
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