Engineers find a new way to punch holes through steel

Electromagnetic pulses (EMPs) are usually associated with warfare. The idea is to use a blast of energy to fry the enemy’s computers and telecommunications gear. One common way proposed to do this is with an atomic bomb. In a less extreme fashion, however, EMPs have peaceful uses. They are already employed industrially to shape soft and light metals, such as aluminium and copper. Now a group of researchers has found a way to use an EMP device to shape and punch holes through industry’s metallic heavyweight - steel. This could transform manufacturing by doing away with the need to use large, heavy presses to make goods ranging from cars to washing machines.

Verena Krдusel and her colleagues performed their trick by beefing up an existing electromagnetic-forming machine. Such machines use a bank of capacitors to discharge a current rapidly through a coil. The coil converts the current into a powerful magnetic field. When the component to be worked is placed next to such a machine, the coil induces in it a corresponding field. Like poles repel, and the repulsion between the two fields is strong enough to make the metal distort.

Dr Krдusel and her colleagues boosted the power of their machine by strengthening its coil and speeding up the rate at which the capacitors dump their charge. The result is an extremely strong field - one that delivers enough pressure when it hits the steel to punch out the material next to it, leaving a hole behind. The impact pressure on the steel is about 3,500 atmospheres. That is the weight of three small cars pressing on an area only a centimetre or so square.

The result is that the machine is able to punch holes 30 mm in diameter through the type of sheet steel used to build car bodies, which is usually around 1mm thick. The group have also used their machine to punch holes in hardened steel, including stainless steel. And, besides punching holes in steel, such a machine could also be used to form shapes out of the metal without the need to use a mould or a die.

The Economist

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