Recent advances in additive manufacturing (AM) have enabled the fabrication of functionally graded porous biomaterials (FGPBs) for application as orthopedic implants and bone substitutes. Here, we present a step-wise topological design of FGPB based on diamond unit cells to mimic the structure of the femoral diaphysis. The FGPB was manufactured from Ti-6Al-4V powder using the selective laser melting (SLM) technique. The morphological parameters, permeability and mechanical properties of FGPB samples were measured and compared with those of the biomaterials with uniform porous structures based on the same type of the unit cell. The FGPB exhibited a low density (1.9 g/cm3), a moderate Young's modulus (10.44 GPa), a high yield stress (170.6 MPa), a high maximum stress (201 MPa) and favorable ductility, being superior to the biomaterials with uniform porous structures in comprehensive mechanical properties. In addition, digital image correlation (DIC) and finite element (FE) simulation were used to unravel the mechanisms governing the deformation and yielding behavior of these biomaterials particularly at the strut junctions. Both DIC and FE simulations confirmed that the deformation and yielding of the FGPB occurred largely in the load-bearing layers but not at the interfaces between layers. Defect-coupled FE models based on solid elements provided further insights into the mechanical responses of the FGPB to compressive loads at both macro- and micro-scales. With the defect-coupled representative volume element model for the FGPB, the Young's modulus and yield stress of the FGPBs were predicted with less than 2% deviations from the experimental data. The study clearly demonstrated the capabilities of combined experimental and computational methods to resolve the uncertainties of the mechanical behavior of FGPBs, which would open up the possibilities of applying various porosity variation strategies for the design of biomimetic AM porous biomaterials. STATEMENT OF SIGNIFICANCE: Functionally graded bone scaffolds significantly promote the recovery of segmental bone defect. In the present study, we present a step-wise topological design of functionally graded porous biomaterial (FGPB) to mimic the structure of the femoral diaphysis. The Ti-6Al-4V FGPB exhibited a superior combination of low density, moderate Young's modulus, high yield stress and maximum stress as well as favorable ductility. The biomechanical performance of FGPB was studied in both macro and micro perspectives. The defect-coupled model revealed the significant yielding in the load-bearing parts and the Young's modulus and yield stress of the FGPBs were predicted with less than 2% deviations from the experimental data. The superiority of combined experimental and computational methods has been confirmed.

中文翻译：

---

增材制造的功能梯度多孔金属生物材料的拓扑设计，渗透性和机械性能。

增材制造（AM）的最新进展已使功能梯度多孔生物材料（FGPB）的制造成为骨科植入物和骨替代物。在这里，我们介绍了基于钻石晶胞模拟股骨干的结构的FGPB的分步拓扑设计。FGPB是使用选择性激光熔化（SLM）技术由Ti-6Al-4V粉末制成的。测量了FGPB样品的形貌参数，渗透性和力学性能，并与基于相同类型晶胞的具有均匀多孔结构的生物材料进行了比较。FGPB表现出低密度（1.9 g / cm3），适度的杨氏模量（10.44 GPa），高屈服应力（170.6 MPa），高最大应力（201 MPa）和良好的延展性，在综合机械性能方面优于具有均匀多孔结构的生物材料。此外，数字图像相关性（DIC）和有限元（FE）模拟被用来揭示控制这些生物材料的变形和屈服行为的机制，特别是在支杆连接处。DIC和FE模拟都证实FGPB的变形和屈服主要发生在承载层中，而没有发生在层之间的界面上。基于实体元素的缺陷耦合有限元模型为FGPB在宏观和微观尺度上对压缩载荷的机械响应提供了进一步的见解。利用FGPB的缺陷耦合代表性体积元模型，Young' 预测FGPB的s模量和屈服应力与实验数据的偏差小于2％。这项研究清楚地证明了结合实验和计算方法来解决FGPB力学性能不确定性的能力，这将为应用各种孔隙度变化策略设计仿生AM多孔生物材料提供了可能性。意义声明：功能分级的骨支架可显着促进节段性骨缺损的恢复。在本研究中，我们提出了功能梯度多孔生物材料（FGPB）的逐步拓扑设计，以模拟股骨干physi端的结构。Ti-6Al-4V FGPB表现出低密度，适度的杨氏模量，高屈服应力和最大应力以及良好的延展性。从宏观和微观两个角度研究了FGPB的生物力学性能。缺陷耦合模型显示了承重部件的明显屈服，并且预测了FGPB的杨氏模量和屈服应力与实验数据的偏差小于2％。实验和计算方法相结合的优越性已得到证实。