Once upon a time, automakers didn’t do crash tests. If you had an accident and something bad happened, you just had to take your lumps. Eventually, the industry realized this was stupid, and that cars should be tested so they aren’t needlessly dangerous for passengers in a collision. That spurred rapid developments in the field, with engineers soon employing crash test dummies and high-speed film to test and improve their vehicles. Now, Mercedes-Benz has taken things to a new level by bringing X-rays into the mix.
Yes, we’re talking about those X-rays—the high-powered electromagnetic beams that are most commonly known for their use in medical imaging. Just as they can pass right through flesh and (to a lesser degree) bone, they can also be used to image inside the structures of a car.
To that end, Mercedes-Benz figured they could be used to look inside a vehicle during a crash. And we’re not just talking about taking a single X-ray image, either. We’re talking high-speed photography at up to 1,000 X-ray exposures in a single second.
Mercedes-Benz has developed the technique in partnership with the Fraunhofer EMI research institute. It involves using a linear accelerator as a source of X-ray radiation. The device is able to generate a continuous stream of X-ray pulses of just a few microseconds in duration, allowing the capture of up to 1,000 images a second.
In practice, during a crash test, around 100 still X-ray images are shot and then later combined into a video for analysis. They can show engineers what goes on inside a structure or inside a dummy’s body during a crash. While this is going on, all the usual instrumentation and cameras typically used in a crash test are operational too. Thus, the X-ray system adds a useful analysis tool that doesn’t compromise any other data typically captured in such a test.
Notably, the car is stationary at the beginning of the test. Accelerating the car into a barrier would make it hard to aim the vehicle in the right spot for the X-ray imager. Instead, the car is set up in position and a barrier is rammed into the vehicle instead. This allows accurate imaging of precise areas of interest at the moment of impact.
When imaging a crash test, the X-rays are aimed through the vehicle from above. Meanwhile, an electronic X-ray detector is placed underneath the vehicle to capture the X-rays as they pass through. Just as light must be captured by a camera to create a photo, the X-rays must be captured after passing through the vehicle to get an image of what’s happening inside. Thin areas of the vehicle absorb less X-ray radiation, while denser areas absorb more. The intensity of the radiation hitting the detector determines the grey level of each part of the image.
As a guide, think of an X-ray of a human arm. The flesh shows up light grey because some X-rays pass through. Bone shows up brighter white as it’s denser, and lets less X-rays pass. Meanwhile, the air around the arm lets all the X-rays through, so shows up black.
It’s much the same when X-raying a vehicle, but the detector is tuned so that the black-to-white range is matched to the metals and plastics used in the vehicle’s construction. It’s similar to how airport security staff alter the contrast of their luggage scanners when inspecting baggage. The X-rays produced are of high enough energy that they can pass through the vehicle’s materials, allowing engineers to see inside complex structures.
Combine a bunch of these images taken in quick succession, and engineers can get additional insight into what happens to vehicle structures during a crash. Traditionally, engineers would only be able to look inside a structure after a crash by X-raying it manually or cutting it open. However, with this method, it’s possible to see what’s going on inside in slow motion.
You might imagine there are radiation concerns around this practice, and you’d be correct. X-rays are high enough in energy that it’s important to limit one’s exposure to them, particularly if working around them regularly. Experts at Fraunhofer EMI implemented a rigorous safety scheme in this regard. Employees working on the project wear special dosimeters to ensure they don’t exceed safe exposure levels. The tests also take place in a building with a thick concrete wall to ensure others in the area are not unduly exposed.
As work continues to make vehicles safer than before, it makes sense that new tools would be useful in support of this work. The X-ray system by Mercedes-Benz is an innovative idea that could serve its engineers well in better understanding how cars behave in collisions.
Image credits: Mercedes-Benz
Those are some incredibly cool images. Also, one of the few words of German I know is ‘bremsstrahlung’, which means ‘x-rays’.
(lit. ‘braking radiation’ because you create x-rays by firing electrons at a lump of metal, and as they slam to a halt all that energy becomes an x-ray. Very appropriate for this context).
PS, thanks for using the full name of the manufacturer in the headline, so I didn’t immediately jump to the conclusion that Mercedes Streeter is now a super-villain firing death rays from her fingertips 😉
Nice! I just listened to Crash Test Dummies- mmm mmm mmm mmm
This is wasteful, Mercedes is going to use up the world’s supply of x-rays on a bunch of empty cars.
Do the dummies have artificial bones? Asking for a friend here.
Nah, the bones are natural. Just the skin is artificial.
Firing rays at a car that knows it’s in danger seems like the way a comic book would give us a superpowered car hero or villain. (Maybe there’d be a technician who somehow merged with the car, too.)
So let’s crank this up to maximum power and see what happens.
This seems like a good use. Don’t they already use a scaled up version of this on border checks?
Also I just wanted to make a joke that in David’s XJ, he had the ability to do CAT scans.