We know that even a speck of dust or a tiny droplet can damage a tough metal surface if the particle collects enough speed on impact.
But until now there was a problem, how or to clarify Why did this damage happen? That's because the speed has to be extremely high and the scale is incredibly small.
MIT researchers have now developed cameras that are fast enough and sufficiently magnified to capture this moment of impact in detail – and have learned that these speeds are so high that the impact actually partially melts the surface ,
This was "unforeseen," based on earlier research on erosion, the scientists said.
High-speed microscopic particles can actually be quite useful, and the way they erode surfaces is not all bad. Sandblasting is one such application or the application of coatings.
But they can also be dangerous ̵
"We want to understand the mechanisms and precise conditions under which these erosion processes can take place," explained Mostafa Hassani-Gangaraj from MIT.
He and his team developed a series of experiments to find out, with a microparticle impact tester developed at MIT. With a frame rate of up to 100 million FPS, the test bed can record at incredibly high speeds.
They then set up a tin surface and heated up another piece of tin with a laser. This vaporizes the substrate surface, ejecting microscopic tin particles and accelerating them. As a result, tin particles about 10 microns in diameter – about 0.01 millimeters – impacted the tin surface at speeds of up to one kilometer per second (2,237 miles per hour).
They also exposed these impacts with lasers to get a clear view of what had happened.
This enabled them for the first time to see the mechanism causing the damage, rather than relying on the surface investigation of the impact.
And there, in the video, you can clearly see molten material splashing away from the point of impact.
This information is actually incredibly valuable. This can, for example, contribute to the improvement of industrial processes using high-speed microparticles, where, according to the researchers, higher rates lead to better results.
These results show that this is not always the case. If you turn it up too high, you can melt things without doing so.
This also helps us to understand how microparticles can damage turbines, spacecraft, and oil pipelines. And what about the poor robots on Mars who survived those crazy dust storms? With this new knowledge, engineers could develop erosion-resistant materials for both space and terrestrial applications.
Obviously, there is still a bit more research. The team used only tin and in the direct impact angle. There will probably be slightly different effects for different materials – with different degrees of hardness or toughness and different melting points (the tin values are quite low) and different impact angles.
But this first step is to show the test bed, and the experimental set-up can be used to capture and analyze this moment of impact, and is extremely impressive.
"We can extend this to any situation where erosion is important," said MIT engineer David Veysset.
The team's research teams were published in the journal Nature Communications .