Study On Mechanical Properties And Permeability Of Fused Porous Ti6Al4V Bone Scaffold

Synthetic titanium alloy bone scaffold has good mechanical properties and biocompatibility,which can effectively solve the problems of limited autologous bone source and limited antigenicity of allogeneic bone.It is widely used in clinical orthopedic transplantation.However,human natural bone tissue is a complex porous structure,and dense titanium alloy bone scaffold is difficult to meet the requirements of mechanical properties and suitable permeability.Therefore,this paper proposes a design method of porous bone scaffold fused with Triply Periodic Minimal Surface（TPMS）,and uses selective laser melting technology to prepare a fused porous bone scaffold sample,and studies its mechanical properties and permeability.The main research contents are as follows:（1）Design and preparation of porous bone scaffold.Based on the G unit structure and D unit structure in the triply periodic minimal surface,the corresponding relationship between the constant K in the function equation and the porosity P is analyzed.The visualization of the TPMS unit structure is realized by Wolfram Mathematica software,and the Sigmoid function is used to construct the parameter equation of the fused TPMS porous bone scaffold.The parametric modeling of the fused TPMS porous bone scaffold is realized,which provides a new idea for the design of porous bone scaffold.（2）Study on the influence of structural parameters on the mechanical properties of fused TPMS porous bone scaffold.The effects of three structural parameters of TPMS porous bone scaffold on elastic modulus,yield strength and porosity were investigated in detail by response surface method.The results show that the optimal structural parameters are:constant K₁=10.000,constant K₂=2.656,fusion boundary r=5.564 mm.The porous structure of fused TPMS was prepared by using the optimal structural parameters.The yield strength is 400.962 MPa,the elastic modulus is10.532 GPa,and the porosity is 64.027%.Porous bone scaffolds with good mechanical properties can be prepared by fusing TPMS and using selective laser melting technology.（3）The directional study of mechanical properties of TPMS porous bone scaffold.According to the symmetry of the inner G unit structure of the fused TPMS porous bone scaffold,the inner G unit structure was rotated by quaternion to evaluate the mechanical properties of the fused TPMS porous bone scaffold in different directions.The yield strength of the fused TPMS porous bone scaffold is in the range of 367.741～419.354 MPa,and the elastic modulus is in the range of 10.617～11.252 GPa.The results show that the designed fused TPMS porous bone scaffold has stable mechanical properties in different directions,which can meet the human body’s demand for the directional mechanical properties of porous bone scaffolds.（4）Study on permeability of fused TPMS porous bone scaffold.The effect of the rotation of the G unit in the inner layer of the fused TPMS porous bone scaffold on the permeability and fluid flow characteristics was investigated.The results show that the rotation of the G unit has a small impact on permeability.The scaffold rotates 45°in the[100]direction has a minimum permeability of 5.70015×10^-8 m²,while the scaffold rotates 60°in the[111]direction has a maximum permeability of6.33725×10^-8 m²,which meet the permeability requirements of human bone tissue.The inner layer of the fused TPMS porous bone scaffold is conducive to transporting nutrients and promoting the migration of bone tissue cells,and the outer layer is conducive to the attachment of bone tissue cells to the structural surface.