How can mere human hair defeat razors so quickly when the blade is 50 times harder than the hair? MIT researchers are on the case.
Associate professor of metallurgy C. Cem Tasan and colleagues found that shaving does not simply wear down the blade over time: a single strand can cause the edge to chip under specific conditions, which then leaves the blade vulnerable to further chipping. As more chips accumulate, the edge can quickly dull, especially if the microscopic structure of the steel is not uniform. The angle at which the blade approaches the hair and the presence of defects in the steel’s heterogeneous microstructure also play a role.
Key to the findings were a series of experiments by graduate student Gianluca Roscioli, who used a scanning electron microscope to examine razor blades after shaving his face and then built an apparatus to carry out cutting tests on his own and his lab mates’ hair inside the microscope. The team also did computational simulations of a blade slicing through a strand to predict the conditions under which the blade would be likely to chip.
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