Research On Friction Characteristics Of Bionic Flexible Contact Surfaces

Bionics is a method of links the functions,biological structures,and organizational principles found in nature to modern technology and applying it to the field of technological innovation.In nature,many animal pads with climbing ability have natural anti-skid function,and their contact surface can be considered as a generalized flexible friction pair.At present,the flexible friction pair is widely used in transmission device using friction force transfer,in order to increase the friction coefficient of contact pair,and improve the working ability and safety operation.In this paper,from the perspective of bionics,the representative micro-texture was carried out on rubber material to study the friction characteristics of the flexible friction pair,which achieves the purpose of increasing friction and control of the friction coefficient.According to the bionic flexible surface contact theory and adhesion friction theory of hemisphere body-plane model,the friction-increasing mechanism of bionic flexible surface was obtained.For the frictional contact model,the total friction force is equal to the sum of adhesion force and furrow force under the motion trend or relative motion trend.The condition that bionic flexible surface morphology has friction-increase characteristics is that at least one of the friction pairs is a flexible body,and the unprocessed surface must be a flexible body.The compression deformation and tensile friction of the bionic flexible surface were analyzed by finite element analysis software.Firstly,taking the hemispherical bulge bionic flexible surface as an example,the contact information between bionic flexible surfaces,such as deformation,embedding height,stress,contact state and so on were studied using finite element method.After that,the influence of the bulge spacing,positive pressure,hardness,bulge shape and bulge size on the friction characteristics of bionic flexible surface were also studied by means of control variable method.The influence of the bulge spacing,positive pressure,bulge hardness,bulge shape and bulge size on the friction enhancement performance of bionic flexible surface were analyzed using the self-made experimental platform,the results of friction contact experiment showed that the increase of the equivalent friction coefficient of bionic flexible surface could reach 63.113%.The friction-increasing laws obtained by experiments are as follows:Equivalent friction coefficient increases initially and then decreases with the increase of the bulge spacing.When the bulge spacing is small,the increase of the equivalent friction coefficient is smaller,and with the increase of spacing,the deflection of the upper plate under pressure increases correspondingly,the increase of the actual contact area and the furrow force lead to the friction-increase.As the spacing continues to increase,the number of bulges on the unit area will decrease,Therefore,the equivalent friction coefficient is reduced.The equivalent friction coefficient increased initially then decreases with the increase of positive pressure,however,the reduction is slight and tends to be stable.The equivalent friction coefficient increases with the bulge hardness,and the increase is obvious.Bionic flexible surface with cuboid bulge has the best friction-increasing properties compared to the cone bulge and hemispherical bulge,and the cone-shaped bulge takes second place.When the bulge spacing is small,the equivalent friction coefficient decreases with the increase of the bulge size,and when the bulge spacing is large,the equivalent friction coefficient increases with the increase of the bulge size,this is due to the increase of the bulge size which is equivalent to reducing the spacing of the bulge.The inherent law between the equivalent friction coefficient of bionic flexible surface and the influencing factors were revealed through the theoretical analysis,numerical simulation and experimental verification,which provide reliable basis for the design and application of friction transmission and anti-slip surface.