Investigation Of Macro-micro Mechanical Behaviors Of Bovid Horns

As a kind of biological composite material,the bovine horn has superior mechanical properties.The macro-micro physics structure of bovine horn is the result of species competition and natural selection for eons,which is vital for bovine to survive in fiercely competitive world.It is beneficial to study on the macro-micro physics structure of bovine horn for both further understanding the intrinsic mechanism of the excellent mechanical behavior and development of high-performance biomimetic composites.This paper study on the relationship between macro-micro physic structure and mechanical behavior of horns by experimental observation,mechanical test,numerical calculation and finite element simulation on the yak horns,buffalo horns and sheep horns.I accomplish the following work specifically and draw several useful conclusions:(1)Observe and record the overall shape and size of the yak horn,buffalo horn and sheep horn,then establish 1:1 scale model of horn analysis based on the experimental data then calculated and analyzed the mechanical behavior.Based on the analysis of the gradient of yak angle with regular circular cross section,I find that the inclination of the horn has a great influence on the stiffness of the structure,and 40-60(the gradient of the parameters described in the text)is the optimal gradient of the horn.The horn has a more average stress distribution and a smaller maximum stress in the range.Different loading of horns show that the maximum stress of the horn is mainly affected by the y component force,in the ideal gradient range.Observations on the irregular cross-sections of buffalo horns and sheep horns indicate that the two horns have a structural enhancement on the side where the stress is bigger.(2)Test experimentally on the compression and bending mechanical properties of yak horns,buffalo horns and sheep angles along the longitudinal,transverse and 45 o directions.The results show that:(1)the longitudinal elastic modulus of the three horns is greater than the transverse elastic modulus;(2)The longitudinal yield limit of the buffalo horn and the horn angle is greater than its lateral yield limit,but the longitudinal yield limit of the yak horn is slightly less than the transverse yield Limit;(3)the bending modulus of buffalo horn in 45 ois the largest,the horizontal is smaller,and the vertical is smallest.(4)The longitudinal flexural modulus of the yak horn is the largest,and the longitudinal bending modulus of the sheep angle is the smallest.(5)Buffalo horns exhibit brittleness damage,different from other specimens in longitudinal compression tests and transverse bending tests.(3)The observation on microstructure of horn section in different directions by scanning electron microscopy showed that yak horn and buffalo horn were composed of laminated keratin fibrous layer.The thickness of the fiber layer in the yak horn is larger(about 60 μm),and the thickness of the fiber layer in the buffalo horn is smaller(about 10 μm).The observation also shows that the fibrous layer of the yak horn is made up of band-like fibers in a similar weaving manner,and the fibrous layers of the buffalo horn are made of finer fibrous sheets.Sheep is composed of longitudinally extending thin tubes and keratin fiber layers surrounded by.(4)The fiber sheet stacking model was established,and the fiber sheet extraction in the stacked structure was calculated.The results show that the decrease of the thickness and the increase of the transverse dimension of the fiber piece will increase the fracture toughness of the horn.The analysis and calculation on the fiber pullout force in the hole-around structure show that the fiber in the pore structure increases the difficulty of fiber desorption,which also increases the fracture toughness of horns.The calculation of stress and strain of Model with hollow cylindrical and noumenal Model show that the pore structure has better ability to resist bending and torsional deformation under the same volume modulus.(5)The porous horn core is simplified into a honeycomb structure,and its modulus in different directions is analyzed and calculated.The results show that the horn core honeycomb structure plays an important role in energy absorption and structural enhancement of the horn.