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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
23 M ay 2002Explosive form ing techniques 3t
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
23 M ay 2002Explosive form ing techniques 4t
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
23 M ay 2002Explosive form ing techniques 5t
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
23 M ay 2002Explosive form ing techniques 6t
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
23 M ay 2002Explosive form ing techniques 7t
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
23 M ay 2002Explosive form ing techniques 8t
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
23 M ay 2002Explosive form ing techniques 9t
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
23 M ay 2002Explosive form ing techniques 10t
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
23 M ay 2002Explosive form ing techniques 12t
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
23 M ay 2002Explosive form ing techniques 13t
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
23 M ay 2002Explosive form ing techniques 14t
Ariane V cone panels: “im pact curving”
++ + + + + + + + + + +V ~ 50 -100 m /s
23 M ay 2002Explosive form ing techniques 15t
Beaded panel
• Aeolus(X38-rudder)
beaded panel PM 1000
• Hot structure part
• Im proved form ability
• No pressing lim its
• Single tool
23 M ay 2002Explosive form ing techniques 16t
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)
23 M ay 2002Explosive form ing techniques 17t
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
23 M ay 2002Explosive form ing techniques 19t
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
23 M ay 2002Explosive form ing techniques 21t
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
23 M ay 2002Explosive form ing techniques 22t
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 27t
Detonography: an artistic m ethode to duplicate natural m aterial (m etal fossil)
23 M ay 2002Explosive form ing techniques 28t
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