电子束增材制造多孔骨支架的选用与疲劳性能研究

Study on the Selection and Fatigue Performance of Porous Bone Scaffolds Fabricated by Electron Beam Melting

增材制造多孔结构具有优良的力学仿生和促骨长入性能,支持骨科植入假体在体内的长期稳定。本研究采用三周期极小曲面(TPMS)法和电子束熔融技术(EBM)设计并制备了仿骨小梁多孔结构,通过微计算机断层扫描技术(Micro-CT)和力学疲劳实验研究它们的孔隙特性、机械力学和疲劳性能,提出了一套新颖的适用于骨科植入假体的选用方法,以满足孔隙连通、力学稳定和高周疲劳寿命的需求。Micro-CT和扫描电镜(SEM)表征发现,单元尺寸≥1.5 mm的多孔支架具有仿生的孔径(748μm)和良好的孔隙连通性;TPMS-Gyroid支架的力学稳定性和可靠性优于TPMS-Diamond支架,所建立的Gibson-Ashby方程可为钛合金多孔支架的设计提供力学性能预测;支架在应力水平为0.2时的疲劳寿命>106次,满足植入材料的长期安全使用要求,其弹性模量与人体松质骨的弹性模量相似(0.1~1.1 GPa)。疲劳行为的研究还发现,疲劳棘轮和疲劳损伤是引发多孔支架失效的主要原因。在设计金属多孔支架结构时,可通过增大支架单元尺寸来减少裂纹萌生的缺口数量,有助于提高支架的疲劳寿命。

Additive manufactured porous structure offers excellent mechanical biomimicry and osseointegration properties,supporting long-term stability of orthopedic implants in human body.This study employed triply periodic minimal surfaces(TPMS)method and Electron Beam Melting(EBM)technology to design and fabricate porous bone mimicking scaffolds.By investigating the pore characteristics,mechanical performance and fatigue life,a novel selection method suitable for bone implantable devices was proposed to meet the requirements of porosity connectivity,mechanical stability,and high-cycle fatigue life.Micro-CT and SEM characterization revealed the porous scaffolds with unit cell sizes≥1.5 mm had biomimetic pore sizes(748μm)and good pore connectivity.The mechanical stability and reliability of TPMS-Gyroid scaffolds were superior to TPMS-Diamond.The established Gibson-Ashby equation in this work provided mechanical performance prediction for titanium alloy porous scaffolds.The fatigue life of the scaffolds exceeded 106 cycles at a stress level of 0.2,satisfying the long-term safety requirements for implant materials,with an elastic modulus similar to that of human cancellous bone(0.1~1.1 GPa).Furthermore,fatigue behavior studies also indicated that fatigue ratchet and fatigue damage were main causes of porous scaffold failure.In the design of metal porous scaffold’s structure,the number of cracks could be reduced by increasing the size of the scaffold unit cell,which was helpful to improve the fatigue life of the scaffolds.