In crash testing it’s called time zero: the moment an accident begins.
When we think about vehicle safety, we tend to think about what happens after time zero. Crumple zones engage. Seat belts cinch tight. Airbags erupt. And after the violence ends, ideally the passenger cell remains intact, the humans inside unharmed. Those fractions of a second at the onset of an impact are crucial.
But so are the ones that come before it. And the quest for safer cars runs in two directions—not just surviving a crash but trying to stop the clock before it ever gets to time zero.
Last year 32,850 people in the U.S. died in motor-vehicle accidents, according to a preliminary estimate by the National Highway Traffic Safety Administration. For all the gains made in safety—the toll has dropped significantly from the 43,510 fatalities recorded in 2005—getting into your car is still likely the most dangerous thing you’ll do on any given day. But around the world car companies and governments are making advances in vehicle safety at an unprecedented pace.
In the past year I’ve visited the front lines of safety innovation, walking the floor of a crash-test facility in Ohio, talking to engineers across the globe, and trying out new electronic safety systems on the latest vehicles. From progress in active crash avoidance to huge improvements in materials, the achievements we’ve made in vehicle safety are staggering. We may never completely eliminate accidents or deaths, but we’re getting closer.
Considering all of the rapid developments we’ve seen with electronic safety systems in recent years, it’s perhaps counterintuitive that some of the biggest safety improvements in the past decade have come from good old-fashioned steel.
“Over the past 10 to 15 years, steels have been getting stronger,” says Chuck Thomas, chief engineer at Honda R&D Americas, in Raymond, Ohio. “We probably had 500 megapascals of tensile strength in the early 2000s. Now hot-pressed or hot-stamped steel is around 1,500 megapascals.” At that strength you can hang 200,000 pounds on an inch-wide strip without tearing it in two. The high-strength steel is stamped hot and then quickly cooled, allowing for complex shapes and a wide variability in yield strength, which helps determine how a car deforms in an accident.
David Leone, executive chief engineer for Cadillac, says that the use of high-strength steel isn’t about turning passenger cars into invincible tanks but controlling crash energy and minimizing weight. “Heavy does not mean safe,” Leone says. “Heavy means heavy. Go back to the ’50s and ’60s. The cars were heavy. They were stiff. But if you ran into the wall, you bounced off the wall and all the deceleration went through your body. Heavy and stiff is not where you want to be.”
These advances in steel—along with strategic use of other materials such as aluminum, magnesium, and carbon fiber—allow engineers to design structures that can dissipate and redirect crash forces. For example, the new Cadillac CTS uses lightweight aluminum “crush cans” up front to soak up a lot of energy before an impact reaches the passengers. Even the CTS’s seat-belt spools unwind slightly during a crash to help minimize forces on your body.
Read more of the original article at Road & Track.
