Explosive forming techniques - FSB Online · t Explosive formi ng techniques 23 May 2002 6...

C. W entzel, Product m anager explosive form ing for aerospace

tTNO Prins M aurits Laboratory

New concepts for cold form ing of non-ferrous m aterials

Explosive form ing techniques

23 M ay 2002Explosive form ing techniques 2t

Outline

• Explosive m aterialprocessing• form ing

• w elding

• Challengesin form ing high perform ance alloys

• Basic principles

• Novel concepts

• Exam ples


W hat is explosive form ing?

• = High Velocity Form ing

• Explosive� Shockw ave in

w ater � Kinetic energy �

Plastic w ork

• Advantages:• potential for low er recurring cost

• one-sided tooling

• unlim ited pow er (size)

• extended form ability

• unique form ing schem es


Illustration of technology

• Explosive:• detonating chord is the w ork

horse

• shape as appropriate

• charge size as appropriate

• Process in practice• built-up w aterbassin

• w ater tank


Challengesin form ing high perform ance alloys

• Typical alloys• Alum inium 2xxx, 7xxx, 6xxx• Titanium pure, Ti6Al4V, specialalloys• nickel based superalloys• ODSalloys(e.g. PM 1000)

• Difficultiesin form ing:• Heattreatm ents required• Lim itationsin pressing capacity• Hotform ing:costly tooling;thinning; alfa caserem oval(Ti)• Forgings: long lead tim es;expensive

• Challenges:• Cold form ing /forging beyond presentlim itations• Elim inate restrictions on size/load capacity• Develop sheetalternatives for forged com ponents


Explosive m aterialprocessing

• Explosive Form ing• shock w ave in w ater/sand orcontact charge

• free form ing ordie form ing,calibration

• M echanism s

• inertia-effectsin high velocity form ing

• forging effectsin interaction w ith die (ironing)

• Key elem entsofform ing• unlim ited size,large thickness

• steer aw ay from tensiledom ain,invoke shearing deform ation

• extended dynam ic form ability lim its

• Explosive w elding

• Explosive engraving


Illustration of M echanism : shear deform ation

• Inw ard form ing• increased deform ability due to

com bined biaxial tension and

com pression

• sim ple, positive, low cost die

�1

�2

Extended formability

Formability limit curve


M echanism : “calibration”

• Im pact of sheet onto die

• “plastic hinge”

• Forging process

• Consolidation of shape for increased accuracy

DIE

Vim pact~ 80 m /s

sheetShock w ave

gap ~ 0.2m m

Plastic hinge


Sim ulation of calibrationDetonating cord

Pressure wave• Experim ents:

• FM L and m onolithic sam ples

loaded by plastic w ave

• Sim ulations• “Hydrocodes”

• Num erical sim ulations of

calibration process on

m icroscale

• dam ping and through

thickness im pact on die

Plate

Die

Cavitationzone

0E+00 2.00E-01 4.00E-01 6.00E-01 8.00E-01 1.00E+00

First layer yields

Second and third layer stay below yield


Exam ples

• PM 1000 beaded panel• extended lim its

• load capacity

• Ariane V ring fram e• load capacity (T3!)

• inertia effects

• M anifold (Exploform )• load capacity

• cheap die

• distributed load

• M ast segm ent• load capacity (size, thickness)

• Titanium pressure tanks• load capacity

• direction of load, inertia

• Beer vessel• ibid

• Isogrid stiffened case• inhom ogenouspart

• load capacity

• Ariane v cone panels• large size,

• distributed load

• im pact effects


Integrally stiffened (Saturnus‘w affle panel’)


Isogrid product fam ily: proof of concept

• Com plex ducts• Double curved products

• From flat m illed sheet m etal

• Proof of principle:• grid on inside & on outside

• Alum inium 5000-series

• Applied process:• ad-hoc solution

• Result:• Good,

considering

first trials


Ariane V Rocket Fram e

• Current process:• Drop ham m er form ing of 1.4 m segm ents

• Set of four dies

• Die w ear, surface contam ination

• Three interm ediate heat treatm ents

• Explosive form ing• Form ing of 2m m Alum inium

2024 in T3 condition

• Tw o steps in single die.

• Elim ination of heat treatm ent

• Im proved properties

• Qualification ongoing

Scaled development product


Ariane V cone panels: “im pact curving”

++ + + + + + + + + + +V ~ 50 -100 m /s


Beaded panel

• Aeolus(X38-rudder)

beaded panel PM 1000

• Hot structure part

• Im proved form ability

• No pressing lim its

• Single tool


Titanium 6Al4V explosive form ing

• Biaxial extension at room

tem perature• rupture typical

• Solution to be found in:• m aterial flow ; and/or

• interm ediate heat treatm ent

• form ing schem e

(allow s control over deform ation

path)


Inertia form ingRolling / Bending• Scrap rate reduction

• Im proved nesting for circular

fram es

• Explosive pre-form ing of long

strips of m etal

Ring

Exploforming

Sections


Explosive w elding/cladding process


Explosive w elding/cladding

• Room tem perature process

• dissim ilar and sim ilar m etal w elding• e.g. Ti-Steel, SS-Cu, Al-Steel, Ni-steel, also Ti-Ti

• w elding of surfaces (planar/curved, sheet/foil)

• local w elding (“seam w eld”)

• M etal bonding w ithout m elting/re-solidification

• Strong bonds

• High deform ability for further processing

• High heat conductivity

• High electrical conductivity


W elding interface Ta-Cu

0.3 m m


Explosive Seam W eld fatigue perform ance

Source: NASA

Comparative fatigue in Al 6061-T6

0

100

200

300

400

1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06Number of cycles to failure

Max

. Ten

sile

str

ess

[MPa

]

Tensile tests Flexure tests

Explosion seam welds

GTA welds

Parentmaterial


Explosive W elding exam ple

• Titanium 6Al4V joint• proof of principle

• “Explosive Seam W eld”

• Joint strength (notched)• prelim inary result 1200 N/m m

• Potential to be explored and

developed

• Process param eters• Explosive charge (… .)

• Geom etry flyer end

• Preset angle

• Post-w elding:• m achining

• heat treatm ent

PM L Rijsw ijk, 24 M ay 2002

Explosive engraving 23t

Set-up of explosive engraving



Explosive engraving of coins in Al-plate


Details of coin engraving



Set-up of the coinson the plate in the bunker



Detonography: an artistic m ethode to duplicate natural m aterial (m etal fossil)


Concepts to be explored

• Bulkhead /hem isphere• purehem isphere

• elliptical

• gasexplosive form ing alternative

• Hybrid assem bly• explosive w eld ofsolid parts onto sheet

• alternative to integral m achining from plate (e.g. alum inium ribs)

• alternative to forging (com pressorblade)

• alternative to casting

• Stiffened sheetform ing• single curvature

• double curvature

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