Researchers at the Massachusetts Institute of Technology (MIT) say that even if the blade is about 50 times harder than the hair, the shaver will eventually become dull after shaving,media New Atlas reported. A team of MIT engineers led by C. Cem Tasan found the reason why steel shaving blades also become dull when removing hair that is much softer than them. Using an electron microscope, they found that under the right conditions, a single hair could cause a gap in the edge of the blade.
The more frustrating thing about the daily mystery is, why does the shaving blade become dull quickly? Intuitively, stainless steel blades should have a service life of more than a week. Because they are used to cut soft hairs, they should last for several months and, if they are coated with harder material, for longer.
However, razor blades do not last, and other steel blades, such as knives and scalpels, can become dull even when specifically designed for softer materials. According to the Massachusetts Institute of Technology, this is because more things happen than simple metal wear, such as when the blade rubs against harder things, such as grinding stones. Instead, what happens is that if the shaver blade acts with the hair under the wrong conditions, it will appear to crack, due to a mechanism called stress enhancement. This cracking leads to more cracks in a cascade cycle that eventually leads to a very blunt shaver and uncomfortable shaving.
“Our main goal is to understand a question that more or less everyone knows about: why blades become useless when interacting with softer materials,” says Tasan, an associate professor at MIT. “We found the main ingredient for failure, which allowed us to identify a new processing path to make blades that could be used longer.”
“We’re metallurgists and want to know what dominates the deformation of the metal so that we can make better ones. In this case, it’s interesting that if you cut something very soft with something very hard, such as steel, such as human hair, the hard material will fail. “
To learn more about what happens when a blade encounters hair, MIT graduate student Gianluca Roscioli shaves with a disposable shaver and then examines the blade under a scanning electron microscope. When he did so, he found almost no wear or fillet. He did find a gap, but it wasn’t consistent along the edge.
In a more complex test, Roscioli built a micro-mechanical device consisting of a movable stage and two clips to maintain a commercial razor blade and fix the various diameters of test hair donated by lab colleagues. During operation, the unit will be cut at different depths and angles, and it can be mounted into an electron microscope.
Analysis of the enlarged blades reveals that when they cut hair vertically, there are no gaps, but when the angle of the blade meets the hair changes, more gaps occur. Computer simulations from the collected data show that not only angle is important, but the consistency of steel in the blade is also important. If the metal changes along the edge, a weak point creates a gap.
To improve the blade quality, the team has applied for a temporary patent to make the shaver steel more evenly processed.
“Our basic idea is to reduce this heterogeneity while maintaining high hardness,” Roscioli said. “We’ve learned how to make better blades, and now we want to do that.”
The study was published in the journal Science.