In this video excerpt from NOVA’s "Making Stuff: Stronger", host and New York Times technology columnist David Pogue participates in a demolition derby to investigate the strength and toughness of steel. David and Mark Eberhart, author of Why Things Break, circle around a dirt track and survey the damage to their steel car frame. In a related activity, students test the toughness of some common materials using a spoon drop strength test and gain a deeper understanding about the physical properties of some everyday materials and how materials scientists determine how safe they are, how best to use them, and how to design better ones.
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DAVID POGUE Materials scientist Mark Eberhart is here to help me understand what makes car bodies strong. And to do that that, we first have to watch them break.
Mark, you're a prominent scientist, author, teacher. Why are we at a dirt track in Oklahoma?
MARK EBERHART (Metallurgist, Author, Why Things Break) I've been fascinated with understanding why things break since I was about six years old. You can go into a lab, and you can do real detailed experiments—they don't capture the full beauty of why things break. This is the place to come to really understand what a person means when they say strength.
DAVID POGUE We're the Starsky and Hutch of science nerds.
Can I have some rock music please?
Frankly, I wouldn't mind watching from the stands, but Mark insists that only by becoming crash test dummies ourselves can we understand how steel makes car bodies strong.
MARK EBERHART Most people don't think of strength as kind of a monolithic thing, but it really is a combination...
DAVID POGUE Hey, what's your hurry pal? Sorry about that.
MARK EBERHART It's really a combination of properties. It's not just one property, the way most people use the word.
DAVID POGUE So, really, when we say "strong as steel," it's a little more complicated than that?
MARK EBERHART Oh, absolutely.
DAVID POGUE Besides tensile strength, resistance to pulling, there's also toughness. It's a measure of how much energy a material can absorb without breaking.
When a car crashes and the body dents, the steel is absorbing the energy of the crash. That's toughness.
During our 100 laps the car took some serious hits. Did the steel demonstrate toughness?
You know it's not all that much different from Manhattan at rush hour. Let's check this puppy out.
MARK EBERHART There's some damage over here.
DAVID POGUE The body got creamed, but, the steel didn't break. It's dented, yet still intact.
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