The way to get dull hair makes yourself dull
Even if the blade is about 50 times harder than hair, the razor will eventually become dull after shaving. It is believed that the edge rounding and brittleness of the hard coating of the blade are the reasons for this phenomenon, and Roscioli conducted a detailed microstructure study Wait. Different mechanisms are shown. The combination of out-of-plane bending, microstructural heterogeneity, and roughness (microscopic debris along smooth edges) can sometimes cause fractures, if the conditions are consistent. This fracture originates from the uneven interface at the edge of the hair, and the resulting debris blunts the blade faster than other processes.
science, This question p. 689
Steels used for sharp edges or tools usually have a martensite microstructure, high carbide content and various coatings to exhibit high hardness and wear resistance. However, when cutting much softer materials (such as human hair, cheese or potatoes), they actually become unusable. Although this is a daily observation, due to the structural complexity of interacting materials and the complex boundary conditions under which they deform together, people have little understanding of the underlying physical microscopic mechanism. In order to eliminate this complexity, we used two types of micromechanical testing devices to conduct interruption testing and in-situ electron microscope cutting experiments. We conducted analysis and numerical studies on these findings, revealing that the spatial variation of the lath martensite structure plays a key role in causing II-III mixed mode cracking before significant wear.