Study On The Wear Resistance Mechanism Of Wings And Leg Joints Of Katydids

In many engineering fields,such as optoelectronics,electronics,energy,machinery,aviation and so on,friction is the basic behavior of surface / interface contact.The problems caused by friction,such as wear,temperature rise,adhesion and energy consumption,have a huge impact on the energy,environment,technology and economy in the world today.According to relevant statistics,the annual loss of wear and tear alone has reached hundreds of billions of dollars.It is of great significance for energy,environment,technology and economy to solve the problem of friction and wear in the industry.At present,due to various reasons,the methods to solve this problem in the industry have not achieved good results.It has become a hot and difficult point in the research of mechanical materials science to find a new anti-wear principle and new technology.In this paper,with the help of advanced instruments and equipment,the biological wear-resistant mechanism of the friction parts of wings and legs joints of katydids(Orthoptera)was studied.The surface morphology and microstructure were measured and analyzed by scanning electron microscope,stereomicroscope and superfield microscope;the chemical composition and element content were studied by infrared spectrum and X-ray energy spectrum;the mechanical properties were tested by nanomechanical instrument;and the tribological properties were tested by micro friction and wear test machine.In addition,the friction process of the legs and wings of katydids was simulated by using the finite element analysis technology.The main conclusions are as follows:(1)Through the study of the macro morphology and micro structure of the wings and hind leg joints of the katydids,it is found that the file is located in the upper part of the ventral surface of the left wing,which is composed of dozens of the tooth arranged in turn,and the tooth is asymmetric serrated structure;the plectrum is located in the upper left edge of the back of the right wing,with black luster and spiral texture structure.The surface of tibial joint is smooth without clear texture.There are two regular texture structures on the surface of the femur joint: one is the periodic thin strip structure,the other is the laminated strip tile structure.(2)Nano indentation experiment shows that in the stable stage of 1200 nm,the hardness and elastic modulus of the file and Tibia are higher than those of the plectrum and the femur.The chemical composition analysis of the material shows that there are differences in the content of elements and molecular components in different parts.These differences result in different mechanical properties(hardness,modulus of elasticity)of the friction surfaces of these parts.Combined with the study of microstructure,it is found that the tibia-femur friction pair and the file-plectrum friction pair are both composed of hard smooth surface and soft texture surface,which has good wear resistance.(3)After two months of thousands of times of friction,the structure of the wings of the katydids is complete and undamaged.The surface layer of the denture is wrapped with the inner layer of each denture,and can resist wear;the middle layer is composed of ultra-thin nano layers layer by layer,which has strong and high toughness.Because of its layered structure,it has high surface hardness and good ductility,which is beneficial to wear resistance.The asymmetric serrated structure is common in the biological friction system.When the wings are pronounced,the plectrum moves from the steep side to the inclined side,resulting in greater friction and bright sound,avoiding the application of greater force for friction,which is conducive to wear resistance;on the other hand,in the return stage without sounding,the plectrum moves from the inclined side to the steep side,with less friction and less wear.The finite element analysis shows that the stress distribution is more uniform when the plectrum moves from the steep side to the inclined side,and the stress value at the same depth of the steep side is smaller than when the plectrum moves from the inclined side to the steep side.This can improve the anti damage ability and wear resistance of the file.(4)The average friction coefficient of tibia-femur friction pair measured by friction experiment is 0.070,which is lower than that of products in engineering field.The friction coefficient changes irregularly with the fluctuation of friction rate,and increases slightly with the increase of loading force.SEM photos showed that after 100 cycles of friction,no obvious signs of wear were found on the surface of tibia and femur without lubricant,which proved that tibia-femur friction pair had excellent wear resistance.The two texture structures of the femur can reduce the actual contact area with the surface of the tibia from the microscopic point of view,so as to reduce the adhesion force with the smooth surface of the tibia to reduce the wear rate during sliding and improve its wear resistance.The multi-layer composite structure of the femur can provide a hard surface at the outermost layer to reduce the surface wear,and the combination of the soft layer in the middle dissipates the stress of the whole structure and absorbs a certain amount of energy.The finite element simulation of tibia-femur friction pair shows that the stress distribution of tibia radiates outwards around several points in static and dynamic friction.Under static pressure,the femur presents a concave shape,and the stress distribution is uniform.When the tibia side is the contact surface,the stress distribution of femur is similar to dumbbell shape.When the femur is under pressure,its unique arc structure can transfer the stress to both sides,avoiding the stress concentration,which is beneficial to the wear resistance of the leg joint.In conclusion,the friction parts of the leg joints and wings have good wearresistant characteristics,which are affected by many factors,including the special texture structure of the friction surface,the multi-layer composite structure of biomaterials,the combination of soft smooth surface and hard texture surface,and the distribution of stress corresponding to the special shape of the matching surface.All of these factors combined to form the excellent wear-resistant properties of wings and leg joints of katydids.