Researchers from mit have studied the wear and tear of steel blades in the shaving process. First, physicists have conducted a series of experiments under an electron microscope, and then analyzed the interaction between hair and blade using finite element method. It turned out that the risk of damage to the edge increases if cut hair at a large angle, or if you get edge of the hair on the area of the blades with rough edges that there appear already at the stage of manufacture. A great influence on the durability of the blade is provided and uniformity of steel. Article published in the journal Science.
People have long learned to use the steel for making durable and sharp knives, axes and other tools. However, physics still can’t explain what leads to the destruction of the blades of such solid at first glance of the metal. Moreover, it is unclear how the blunt blade, cutting less solid objects than themselves. This question is about the fragility and disposable shaving machines, because in theory, the steel is 50 times harder than an average human hair.
Gianluca Roscioli (Gianluca Roscioli) from the Massachusetts Institute of technology and his colleagues conducted a comprehensive study of the interaction of the steel blades from disposable shaving machine with human hair to determine which factors play the greatest role in the destruction of the tip. First, physicists have studied the objects of their study in an unspoilt view of the electron microscope. Scientists discovered that the blades, even the new machine to shave many minute irregularities, the size of which does not exceed 5 micrometers (average diameter of a human hair is 100 micrometers). The researchers also studied the homogeneity of the steel, from which were made the blades, and has demonstrated that it has sufficiently strong granulirovannogo. All this was useful to physicists in the next stages of the study.
The researchers then observed the change of the condition of the blades after they shaved 10 and 25 times, and found that the first blade from the source of the irregularities start to go cracks, which then lead to chipping of the tip and ultimately to its blunting. However, physicists still wasn’t clear which processes provoke the formation of cracks, there is a need to observe the process in real time. To do this, the researchers created a setup that allows using the electron microscope to continuously monitor the process of removing several mounted on the stand and adjust the angle of the blade. With its help, scientists have discovered that biggest large cracks and recesses in the blade occurred in areas where steel is in contact with the edge of the hair. It also appeared that with the increase of the angle of the blade to the hair relative to the perpendicular position, and increased damage to edge damage.