There may or may not be an end to human capabilities, but at the same time, there is also nothing more important in our arsenal than that tendency to improve on a consistent basis. This tendency, in particular, has already fetched the world some huge milestones, with technology emerging as quite a major member of the group. The reason why we hold technology in such a high regard is, by and large, predicated upon its skill-set, which guided us towards a reality that nobody could have ever imagined otherwise. Nevertheless, if we look beyond the surface for one hot second, it will become abundantly clear how the whole runner was also very much inspired from the way we applied those skills across a real world environment. The latter component, in fact, did a lot to give the creation a spectrum-wide presence, and as a result, initiated a full-blown tech revolution. Of course, the next thing this revolution did was to scale up the human experience through some outright unique avenues, but even after achieving a feat so notable, technology will somehow continue to bring forth the right goods. The same has turned more and more evident in recent times, and assuming one upcoming discovery ends up with the desired impact, it will only put that trend on a higher pedestal moving forward.

The researching team at North Carolina State University has formally started the work to develop new structural health monitoring methods, methods that can automatically monitor aircraft and other critical structures to supplement or replace conventional inspection. According to certain reports, the stated monitoring technologies will bank upon the power of computer vision and digital camera to find damage lying beneath an aircraft’s surface which often remains overlooked during visual inspection. Now, before we get any further into the new development, we must understand what’s wrong with the current way of doing things around this particular discipline. You see, most structural components in a modern commercial aircraft are made from carbon fiber reinforced polymers (CFRPs), a type of composite material. Such a material is ensured to be lightweight but strong enough at the same time so to make it more suitable for aircrafts than, let’s say, any traditional metal could ever be. However, the whole setup also comes decked up with some severe limitations. For instance, while objects impacting the surface will create visible dents in traditional metallic structures, impact damage in composites usually does not leave a significant dent. Creating layer separation (delamination) and cracks below the surface instead, the material complicates the inspection, as human-led inspections cannot detect barely visible impact damage (BVID) of such sort. This, like you can guess, spells major safety concerns for all those who might end up travelling within a potentially compromised aircraft. Fortunately enough, the development in focus tries to take on that very problem, markedly leveraging guided waves to do so. In case you didn’t know, guided waves are a special kind of mechanical vibration wave which can travel long distances in thin structures. Hence, once these waves leave an attached vibrating shaker and travel across the structure, they effectively interact with any irregularities, and the way in which the said interaction goes should inform investigator on the vehicle’s health. To give you a more comprehensive example, if there is any cracking or layer separation beneath the surface, these irregularities may deflect the wave, or the waves may even become trapped within the damage boundaries. This is where a digital camera steps in to record the motion of the structure’s surface and look for any reflections or trapped waves caused by damage. The state recording is what helps us to learn about location and approximate size of the subsurface damage. That being said, it’s not as straightforward as it sounds, because for extracting the motion from a video of the structure, distinct surface features must be recorded. Hence, an artificial speckle pattern is either adhered or painted onto the surface, containing many small, distinct dots. During the course of a recording, a video relating to the speckle motion reveals the surface movement.

Talk about the process of converting a speckled surface video into a single image which highlights the damage, it warrants three primary steps. Firstly, a filter is applied to keep motion caused by wave in the video and remove motion coming from other sources, like camera vibrations and noise from the wider environment. Next up, the motion in each frame of the video is correlated with an image representing the time-averaged motion in the entire video. The last move talks to averaging all of the resulting video frames together and producing a single damage image that highlights locations containing the subsurface damage.

The researchers have already conducted some initial tests on their latest brainchild. During the said tests, they used two composite panels that represent the structure of the fuselage or main body of an aircraft. These panels had a 3.7 pound impactor dropped on them from a height of about 5 inches. The move was found to create significant damage beneath the surface of the panels, a discovery which was confirmed by a three-second video of the surface. The video would do the job using clear and easy-to-interpret images.

As for the technology’s future prospects, even though the camera-based technique is relatively quick and does not require any sensors whatsoever to be attached to the surface, the need to apply a speckle pattern currently limits its practicality. Fortunately enough, the researching team has already started the proceedings to overcome the stated challenge. They plan on bringing a projection-based technique which uses a standard office projector to project a speckle pattern onto the surface. Such a maneuver should help us big time in avoiding the need to modify the structure’s surface. By placing the projector at a relative angle to the camera, it will become possible for any surface motion to make the speckles shift within the video. Hypothetically speaking, a projected speckle, if it is ever achieved, will open up a ton of other use cases, considering a similar system could even be mounted on a drone and flown around an aircraft, autonomously mapping subsurface damage over the entire structure. Although pretty far-fetched for now, we may even be able to offer these inspection capabilities through a single smartphone application, while simultaneously enjoying the option to use them to help certify used capsules for reuse.