The Electro Magnetic Pulse Technology (EMPT) has a wide range of applications, which are not restricted to electro-magnetic forming.
Both welding (i.e. atomic bonding) and joining by a mechanical interlock are possible.
You can use our EMPT machines for processing of tubular components made from steels or high strength alloys even with a large wall thickness
to diameter ratio. You can use them also for non-magnetic metals such as aluminium and copper, because an eddy current is temporarily
induced in the work piece.
What are the Underlying Physical Principles of EMPT?
Current carrying conductors are affected by a force, when placed in a magnetic field. This force is called the Lorentz force. Moreover, current
carrying conductors will generate a surrounding magnetic field. Hence, two parallel wires will experience an attractive force, in case of equal
current conduction direction. Otherwise, the conductors are forced apart, if the currents run in opposite directions.
The same phenomenon happens, if a metallic tube is placed in a coil, through which an alternating current runs (AC). The coil induces a counter-
rotating eddy current in the tube according to Lenz’s law. In conjunction with the coil’s magnetic field the induced eddy current causes a repulsive
force in radial direction, as shown in the figure. The induced eddy current and magnetic force are
represented for the duration of one half wave of the altering current.
When the current’s polarity is altered, a counter-rotating eddy current is induced once again within
the tube. Thus, there are no changes in direction of the resulting magnetic forces. Because of the
component’s inertia, the forming operation is phase delayed with respect to the time-current
function. The figure illustrates the numerically calculated cross-sectional shape of an EMPT-
specimen.
Some time elapses while the sinusoidal current increases, until the first displacement of the cross
section towards a smaller diameter takes place. During this period stresses inside the specimen
increase rapidly, until their amplitude is sufficient to overcome the yield strength of the work piece as
well as its inertia. Successively, the diameter reduction rate is rapidly increased, causing an end of
the forming process prior to the zero point of the first half wave of the
electrical current.
An alternating current in the range of 100kA can be supplied by a pulse generator and is essential for the
generation of the high-flux magnetic field. The pulse generator is assembled of a bank of capacitors, switches
and associated charging and control devices. The first step to start a forming operation is to charge the
capacitors, and this lasts less than 10 seconds.
Afterwards, a high-current switch, which separates coil and capacitors, is closed. Now, the current oscillates at
high frequency between capacitor and coil. This set-up is capable to generate altering current in the range of
some 100kA up to more than 1 Mega Ampere. Due to the capacitor charging time, the pulse generator can be
operated through a conventional 380V/32A socket. The electricity for a PS60 system (60kJ) costs only
approximately 0.0025€ per pulse, i.e. a ¼ Cent......
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We reply to all these questions with a clear
“Yes”...
Your have the challenges, we have the
answers.
Metal forming by electro-magnetic fields?
Is this really possible?
Welding and joining without distortion and heat
affected zones?
Can it be done in an industrial environment?
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