Experimental Research On Dynamic Stress-Strain Characteristic And Dynamic Fracture Of Bovine Long Bone

Bone tissue is an important part of life,it protect internal organs and support the completion of the movement.In the life,bone tissue is under the load from their own and external in the process of life growth and movement.When the applied force exceeds the ultimate strength will cause fracture.Therefore,it is important to research the mechanical properties and fracture behavior of bone tissue.This paper selects bovine long bone cortical bone as the research object.Use electronic universal testing machine and split Hopkinson pressure bar test the mechanical properties of long bone cylindrical specimens in three directions,By the obtained stress-strain curve analysis the stress-strain characteristics of different directions and different strain rates.Combined with high speed camera and scanning electron microscope analyzed the structure,the macro and micro fracture,the crack propagation after the limit ring loading of bone tissue.Analyzed the fracture characteristics of long bone in three directions then combined with the structure of bone finally established the fracture model.The main research results are summarized as follows:(1)The mechanical properties of long bone in different directions are anisotropy.The ultimate strength and elastic modulus of axial direction are maximum of three directions.And the limit strain of radical direction is the maximum.There is a higher strength in axial direction and greater toughness in radical direction.(2)The stress-strain characteristics of bone tissue showed a certain strain rate correlation.The ultimate strength and ultimate strain of bone tissue increased with the increase of strain rate.Under the condition of high strain rate,the ultimate strength is 30%-80% higher than quasi-static loading.And elastic modulus is 4-10 times larger than that of quasi-static loading,and the ultimate strain is opposite.(3)The fracture properties of bone tissue under different loading modes are different,the specimens of quasi-static loading were all of the fracture form of 45~55° degree shear fracture,which was similar to that of the homogeneous material.However,under the Hopkinson loading,the broken forms are various,which are affected by the internal characteristics.(4)Fracture of long bone tissue in different directions affected by the surface characteristics of osteon,Haversian canal,adhesive line,elliptic lacuna.The axial direction of long bone is mainly affected by the internal defects and osteon.The radical direction of long bone is mainly affected by osteon and the Harversian canal.The tangential direction is mainly affected by lamella and fiber.(5)Establish the fracture model of long bone in different directions,combined with bone tissue structure characteristics and stress-strain characteristics.Can be used to analyzing mechanical properties and fracture mechanism of bone tissue under load.