or High Velocity Forming HVF Contents Definition Classification Introduction to Explosive Forming Introduction to Electrohydraulic Forming EHF Introduction to Electromagnetic Forming EMF ID: 263393
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Slide1
High Energy Rate Forming (HERF)orHigh Velocity Forming (HVF)Slide2
ContentsDefinition
Classification
Introduction to Explosive Forming
Introduction to Electrohydraulic Forming (EHF)
Introduction to Electromagnetic Forming (EMF)
Operational Problems in HERFSlide3
Definition of HERFProcesses using electrical, magnetic & chemical energy in addition to conventional energy are known as HERF.
The rate of energy flow is of much higher order, so called as high-energy-rate forming.Slide4
Need of HERF or HVFA press of capacity 500
kN
moving over a
distance of 0.15 m delivers energy of 75 KJ.
But the system is so big and bulky that can only be used for large workpieces.
A system consuming less time, compact & more powerful is the requirement.
So, development of HVF takes place.Slide5
Classification based on type of energy used
Type 1 : uses shock waves by detonating explosives
EXPLOSIVE FORMING
Type
2 : uses electric discharge in form of sparks
Electrohydraulic Forming (EHF)
Type
3 : uses magnetic field
Electromagnetic Forming (EMF)Slide6
Explosive Forming : DefinitionA high speed forming process which changes the shape of metal blank by instantaneous high pressure that results from the detonation of an explosive.Slide7
Explosive forming : Typical valuesMetal tubing : upto diameter 1.4 m & length upto 4.6 m have been formed.
Domes constructed of 6 to 12 piece gore sections fabricated from explosive forming can measure upto 6.1 m in diameter.Slide8
Systems of Explosive FormingConfined Systems (closed system)
Unconfined SystemSlide9
Confined SystemSlide10
Unconfined SystemSlide11
Sequence of Explosive formingSlide12
Explosive forming : Process Parameters Detonators : low & high explosives
Stand off distance*
Medium : shock wave transmissionSlide13
Explosive froming
The use of water as the energy transfer medium ensures a uniform transmission of energy and muffles the sound of the explosive blast.
The process has been successfully used to form steel plates 25 mm thick x 4 m diameter and to bulge steel tubes as thick as 25 mm. Slide14
Effect of stand off distance
Al 2024-0 ----Description : Al-90-94%,
Cu-3.8-5%, Cr-Max 0.1%, Fe-Max 0.5%Slide15
Molten
AlSlide16
Unconfined System : EquipmentsWater TankCrane
Vacuum Pump
Detonator Control BoxSlide17
Explosives
Trinitrotoluene (TNT) : 16.5
GPa
Cyclotrimethylene
trinitramine
(RDX) : 23.4
GPa
Dynamite
PETN (
pentaerythritol
tetranitrate
)Slide18
Electromagnetic Forming Definition
: It is an
impulse or high speed forming
technology using pulsed magnetic field to
apply Lorentz forces
to workpieces preferably made of
highly electrically conductive material
without mechanical contact and without a working medium.
Note:- EMF mainly depends on electrical properties of the material being formedSlide19
(i) Swaging, (ii) Expanding & (iii) EmbossingSlide20
a) Compression, b) Expansion, c) Contour FormingSlide21
EMF theoryIn electromagnetic forming, the initial gap between the work piece and the die surface, called the
fly distance
, must be sufficient to permit the material to deform plastically. Slide22
Advantages over conventional formingHollow profiles can be compressed or expanded and flat or three dimensional performed sheet metal can be shaped and joined as well as cutting operations can be performed.Slide23
Electrohydraulic Forming (EHF)Electro hydraulic forming (EHF), also known as
electro spark forming.
A process in which electrical energy is converted into mechanical energy for the forming of metallic parts.Slide24
EHF theoryA bank of capacitors is first charged to a high voltage and then discharged across a gap between two electrodes, causing explosions inside the hollow work piece, which is filled with some suitable medium, generally water.
These explosions produce shock waves that travel
radially
in all directions at high velocity until they meet some obstruction.
If the discharge energy is sufficiently high, the hollow work piece is deformed. Slide25
EHF Slide26
AdvantagesEHF can form hollow shapes with much ease and at less cost compared to other forming techniques.
EHF is more adaptable to automatic production compared to other high energy rate forming techniques.
EHF can produce small – to intermediate sized parts that don't have excessive energy requirements.Slide27
Materials formed with EHFAluminum alloys, Nickel alloys,
Stainless steels,
Titanium, and
Inconel
718Slide28
ApplicationsDome shapesSlide29
ApplicationsTurbine CasingSlide30
Applications Shallow & Deep Rectangular boxes
Manhole Access covers
Equipment covers
Turbojet engine casing