Abstract
Previous experimental data clearly revealed anisotropic friction on the ventral scale surface of snakes. However, it is known that frictional properties of the ventral surface of the snake skin range in a very broad range and the degree of anisotropy ranges as well to a quite strong extent. This might be due to the variety of species studied, diversity of approaches used for the friction characterization, and/or due to the variety of substrates used as a counterpart in the experiments. In order to understand the interactions between the nanostructure arrays of the ventral surface of the snake skin, this study was undertaken, which is aimed at numerical modeling of frictional properties of the structurally anisotropic surfaces in contact with various size of asperities. The model shows that frictional anisotropy appears on the snake skin only on the substrates with a characteristic range of roughness, which is less or comparable with dimensions of the skin microstructure. In other words, scale of the skin relief should reflect an adaptation to the particular range of surfaces asperities of the substrate.
Highlights
Properties of the ventral surface of the snake skin range in a very broad range and the degree of anisotropy ranges as well to a quite strong extent
May be even predict the interactions between the nanostructure arrays of the ventral surface of the snake skin, this study was undertaken, which is aimed at numerical modeling of frictional properties of the structurally anisotropic surfaces in contact with various size of asperities
In the numerical experiment, we showed the effect of stiffness of the surface structures on frictional anisotropy[22], whereas in the present work we concentrated on the role of relative dimensions between skin structures and substrate roughness in friction generated in different sliding directions
Summary
To simulate anisotropy of friction of the skin covered with anisotropic microstructures, we used an appropriate modification of Tomlinson-Prandtl (TP) model. According to the above observations, the skin is covered by slightly randomized periodic structure of the asymmetric holes with short relatively deep slopes from one side and long smooth slopes from another. One of the simplest ways to mimic such a structure in numerical simulation is to use an array of almost periodically placed Gaussians with slightly randomized (negative) amplitude and positions, having different widths in two opposite directions:. N numerates the positions of the minimums. Total length of the system is defined by the condition
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