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A Bonding Experience: NASA Strengthens Welds
01.22.09
 
The friction stir welding process is currently being used in the manufacturing of wheel rims.

The friction stir welding process is currently being used by several automotive companies and suppliers, including the manufacturing of wheel rims. Image Credit: MTS Systems Corporation

Conventional wisdom says little things strengthen relationships. NASA knows the same is true for welding.

Admit it. You may not have been "wowed" when you read "welding." But what if welding could make your next car safer, more fuel efficient and more affordable? If that fires your interest, then you might want to read further.

Traditional or fusion welding involves blowtorches, solder and all the tools of the trade. Now imagine a different welding process that joins materials with no blowtorch, no solder, no sparks, no smoke, no ozone and no radiation. Instead, it uses friction to heat materials and then "stir" them together at a molecular level.

It may sound like science fiction -- but actually, it's closer to "science friction."

NASA technology has refined a unique process known as friction stir welding, founded by The Welding Institute in Great Britain. It's been used since the 1990's to help make the space shuttle's external tanks safer and more reliable.

Friction stir welding happens something like this. Two pieces of material are clamped firmly together, then a rapidly spinning pin -- that's 300 revolutions a minute -- is forced between the materials at pressures up to 10,000 pounds per square inch.

Just as your hands warm when you rub them together, the interaction between the pin and the material edges creates friction energy on a much larger scale. The friction heats the material edges to a soft state called plasticity, which starts to happen around 800 degrees (F) for most material. The friction energy is carefully controlled not to exceed the point of turning the material to a liquid -- about 1,200 degrees (F) in most cases.

Retractable Pin Tools for the Friction Stir Welding Process

Retractable pin tools for the friction stir welding process. Image Credit: NASA/MSFC

Once the materials are softened the friction stir tool pushes the edges together, allowing them to bond at a molecular level. When it cools, the welded seam is as strong as the original material -- because it IS the original material. No solder or filler are ever used in the process.

Like relationships, "little things" matter in welding. In the original friction stir process, withdrawing the rotating pin left a small opening known as a keyhole. The tiny keyhole created a potential weakness in the weld, and it also added an extra step to fill the hole during manufacturing.

Engineers at NASA's Marshall Space Flight Center developed an innovative pin tool for use in friction stir welding. The pin retracts automatically when a weld is complete and prevents a keyhole. This improvement makes the weld stronger and eliminates the need for patching. The retracting pin also allows materials of different thicknesses and types to be joined together, increasing the manufacturing possibilities.

The NASA-developed pin tool has helped friction stir welding advance within many other industries besides aerospace. It's used to build panels for cruise chips and the walls and ceilings of railroad cars. It bonds the wings and fuselages to some business jets. It strengthens car decks on ferries, and it even improves radioactive waste containers.

Fiction stir welding also has the advantage of being friendlier to both people and the environment. The lack of smoke, fumes and sparks creates better working conditions, and the lack of emissions reduces wear-and-tear on planet Earth.

Back to those improvements that might show up in your next car. Friction stir welding can create braking and steering systems that are stronger and more precise, increasing safety. It improves the performance and design for those all-important wheel rims. It also permits greater use of lighter materials like aluminum. Less weight increases both fuel efficiency and handling ability, so you can love your zippy new sports car even more.

Now that's a REAL bonding experience.

> Read More in Spinoff 2008