The Mystery and Clarity of Leonardo da Vinci's Coefficient of FrictionPages 8-20
Sergey Vasiliy Fedorov
Abstract:
The science of friction has been using the coefficient of friction as the main
quantitative characteristic of the friction process for more than five centuries.
The concept of the coefficient of friction as a characteristic of the resistance to
the movement of rubbing surfaces in a hidden form was formulated by
Leonardo da Vinci: "Each rubbing body exerts a friction resistance equal to one
quarter of its weight, provided that the flat plane is in contact with the polished
surface". Two centuries later, the coefficient of friction appeared explicitly, in
the form of a formula, in the works of G. Amontons. It is clear that the coefficient
of friction is a convenient friction parameter, easily determined in the
experiment. However, what is the physical meaning of resistance to the
movement of rubbing surfaces? Modern engineering believes that the
coefficient of friction has no physical meaning. Thermodynamic analysis of the
friction process is performed. The evolutionary patterns of the behavior of the
friction contact are shown. A structural-energy interpretation of the logic of the
coefficient of friction (resistance) is proposed: accumulation of potential
energy of defects in the crystal structure of the deformable volume by friction
contact. The static potential energy of the formed defects in the crystal
structure of the contact is a measure of the decrease in the kinetic energy of the
relative motion of the rubbing surfaces. Such a formulation of resistance to
movement under friction has a deep physical and clear meaning for a scientist
and engineer. The substantiation of Leonardo da Vinci's formulation of friction
that the friction resistance should be equal to 0.25 is given. The interpretation
of this rule is given for the case of friction in mechanisms (machines). Keywords: Friction,
Resistance,
Energy,
Balance,
Transformation,
Coefficient of friction,
Friction force
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