Browsing: Metrology

Welding is said to be more art than science. In part, this is a nod to the vital, skilled work that welders perform. It’s also recognition of the fact that the physics of the process is really, really difficult to understand. I joined a NIST project on laser welding about two years ago. Before this, I had studied materials for solar panels and had done some work in laser processing, but I had little interest in laser welding. What eventually drew me in, and what motivates me now, is just how complex laser welding is and the opportunity to contribute to the understanding of a process that is so intertwined with everyday life, yet so mysterious. Act I: Creating a…

The creation of a new material has long been either an accident or a matter of trial and error. Steel, for instance, was developed over hundreds of years by people who didn’t know why what they were doing worked (or didn’t work). Generations of blacksmiths observed that iron forged in charcoal was stronger than iron that wasn’t, and iron that was forged in a very high-temperature, charcoal-fired furnace and rapidly cooled was even stronger, and so on. While we’re still learning things about steel, we now have all kinds of recipes that we can use to make steels with different properties depending on the application, but those recipes took a lot of time, sweat and toil to develop. Wouldn’t it…

I was always fascinated with science. However, I steered away from pursuing science beyond high school because there was too much math involved (and “MATH,” a four-letter word if ever I saw one, and I never really got along). As a result, much of my teaching experience has centered around things that came more naturally to me. In fact, though this will be my 11th year teaching, it is only my third year teaching science. Throughout my career as an educator, I have had the joy of taking care of a wide variety of “classroom animals,” including a Chinese water dragon, a soft-shell turtle, a kingsnake, chickens, a tarantula, and even a fresh-water eel. This year, as a sixth-grade science…

As I peer into the cardboard box NIST researcher Amanda Forster holds out for me, I can’t help thinking that this mild-mannered materials scientist has an impressive collection of shivs. The handmade prison weapons include a ballpoint pen with a razor embedded in the shaft and a toothbrush — originally designed to be gentle on your gums — that’s been re-engineered to easily puncture flesh. They are vivid evidence of a scary fact of prison life: anything can be turned into a weapon. Corrections officers wear stab-resistant body armor that’s usually made from fibers of extremely strong material such as Kevlar, just like the ballistic body armor worn by police or military personnel. But because ballistic armor is designed to…

Although they are mass produced, every firearm is unique, and when fired, they leave unique markings called toolmarks on the bullet and cartridge casing. Law enforcement agencies have used these “fingerprints” to match firearms with bullets as part of their criminal investigations for more than a century. While forensic evidence of this kind wouldn’t likely be enough to get a conviction on its own, it has played a crucial role in linking suspects to crimes, and the ability of firearms examiners to make those matches has never been a source of controversy … until recently. In 2009, a report by the National Academy of Sciences questioned, among other things, the lack of objective methods for evaluating and identifying toolmarks. To…

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