| Dense titanium and its alloy artificial bone has high elastic modulus,high strength,and problems such as stress shielding and loosening after implantation,which makes the artificial bone have a short service life.In order to reduce the stress shielding of artificial bone and improve the binding ability of artificial bone implantation,porous titanium was taken as the research object,and its mechanical properties were studied by molecular dynamics simulation and mechanical property experiment,and a constitutive model was established.According to the constitutive relation,the stress of tibia-femur movement was simulated by finite element method.Finally,the surface of porous titanium artificial bone was designed with bionic microstructure to improve its bonding ability,and its service performance was analyzed through hardness,friction and wear,contact Angle,body fluid immersion and other experiments.Specific work and achievements are as follows:(1)The micromechanical properties of porous titanium in artificial bone were analyzed by molecular dynamics simulation.It was found that the porous titanium had the characteristics of strain rate strengthening and temperature softening.High strain rate promoted the transformation of porous titanium HCP phase into BCC,which improved the strength of the material.The increase in temperature leads to more boundary growth and slippage,which reduces the strength of the material.(2)The macroscopic mechanical properties of porous titanium for artificial bone were tested by static and dynamic compression experiments and a constitutive model was established.According to the constitutive relation,the tibial-femoral bending forces of porous titanium artificial bone were analyzed and calculated by using the finite element method.The results show that the compression process of porous titanium can be divided into three stages:elasticity,plasticity and densification.The overall accuracy of J-C model simulation results is not high,which can better describe strain hardening.The stress of tibia-femur in the process of rotation of porous titanium artificial bone is less than 20 MPa,which is far less than the yield strength of porous titanium and meets the mechanical requirements.(3)Based on the analysis of the morphology of natural bone and the adherent foot of salamanders and tree frogs,the bionic design of polygon surface microstructures of different shapes and sizes,including hexagons,circles,quadrilaterals,rhomboids and triangles,with the same area ratio control for different shapes.The optimal processing parameters were determined by laser processing experiments,and the bionic polygon microstructures were fabricated on porous titanium surface and characterized by shape measurement microscope.(4)The service performance of porous titanium surface with different microstructure was analyzed by hardness,friction and wear,contact Angle and simulated body fluid immersion experiments.The results show that the hardness of the microstructure surface can be improved by laser machining.Microstructure surface samples have a certain wear reduction effect,and the wear resistance of hexagonal microstructure is better than that of other shapes.The porous titanium surface is hydrophilic,and the different microstructures constructed by laser processing can reduce the contact Angle and improve the hydrophilicity of the material.The samples with microstructures are conducive to HA deposition.The contact Angle of the hexagonal microstructure surface is lower than that of the other shapes,and the hydrophilicity is better.Among the different microstructures,the hexagonal microstructures have more HA deposition and better biological activity. |
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