How Many Times you can Shave Before a Steel Razors Become Dull

"And we wanted to understand, under what conditions does this chipping take place, and what are the ingredients of failure?"

Close analysis of the SEM pictures showed that chips didn't occur when the hair was fully perpendicular to the blade: it was the act of the hair bending that made chipping more likely, with damage usually in the places where the blade edge was met the sides of the hair strands.

Computer simulations run by the researchers identified three likely points of weakness: when the blades meet the hair strands at an angle, when the blade isn't uniform in its steel composition, and when the hair strands hit the blade at a point of structural weakness in that non-uniformity.

The term stress intensification is used in material science when damage is worsened by the presence of microcracks in the material, and that seems to be what's happening here: the hair is causing these microcracks to grow into chips, dulling the blades.

Using these findings, the researchers think that steel could be better manufactured to be more resistant to these microcracks and the chips that grow from them. If that happens, then our razors could last a lot longer against the soft hair on our bodies.

"We are metallurgists and want to learn what governs the deformation of metals, so that we can make better metals," 

The research has been published in Science.