Tianjin Key Laboratory for Advanced Mechatronic System Design and Intelligent Control, National Demonstration Center for Experimental Mechanical and Electrical Engineering Education, Tianjin, University of Technology, Tianjin, 300384, People's Republic of China.
Just Huajian Medical Device (Tianjin) Co., Ltd., Tianjin, 300190, China.
J Orthop Surg Res. 2020 Feb 7;15(1):40. doi: 10.1186/s13018-019-1489-y.
Additively manufactured porous metallic structures have recently received great attention for bone implant applications. The morphological characteristics and mechanical behavior of 3D printed titanium alloy trabecular structure will affect the effects of artificial prosthesis replacement. However, the mechanical behavior of titanium alloy trabecular structure at present clinical usage still is lack of in-depth study from design to manufacture as well as from structure to mechanical function.
A unit cell of titanium alloy was designed to mimick trabecular structure. The controlled microarchitecture refers to a repeating array of unit-cells, composed of titanium alloy, which make up the scaffold structure. Five kinds of unit cell mimicking trabecular structure with different pore sizes and porosity were obtained by modifying the strut sizes of the cell and scaling the cell as a whole. The titanium alloy trabecular structure was fabricated by 3D printing based on Electron Beam Melting (EBM). The paper characterized the difference between the designs and fabrication of trabecular structures, as well as mechanical properties and the progressive collapse behavior and failure mechanism of the scaffold.
The actual porosities of the EBM-produced bone trabeculae are lower than the designed, and the load capacity of a bearing is related to the porosity of the structure. The larger the porosity of the structure, the smaller the stiffness and the worse the load capacity is. The fracture interface of the trabecular structure under compression is at an angle of 45 with respect to the compressive axis direction, which conforms to Tresca yield criterion. The trabeculae-mimicked unit cell is anisotropy. Under quasi-static loading, loading speed has no effect on mechanical performance of bone trabecular specimens. There is no difference of the mechanical performance at various orientations and sites in metallic workspace. The elastic modulus of the scaffold decreases by 96%-93% and strength reduction 96%-91%, compared with titanium alloy dense metals structure. The apparent elastic modulus of the unit-cell-repeated scaffold is 0.39-0.618 GPa, which is close to that of natural bone and stress shielding can be reduced.
We have systematically studied the structural design, fabrication and mechanical behavior of a 3D printed titanium alloy scaffold mimicking trabecula bone. This study will be benefit of the application of prostheses with proper structures and functions.
最近，增材制造的多孔金属结构因其在骨植入物应用中的巨大潜力而受到广泛关注。3D 打印钛合金小梁结构的形态特征和力学性能会影响人工假体置换的效果。然而，目前临床应用中钛合金小梁结构的力学性能，从设计到制造，从结构到力学功能，仍缺乏深入研究。
设计了一个模仿小梁结构的钛合金单元。控制的微观结构是指由钛合金组成的单元的重复排列，构成支架结构。通过改变单元的支柱尺寸并整体缩放单元，获得了 5 种不同孔径和孔隙率的模仿小梁结构的单元。基于电子束熔化（EBM）技术制造钛合金小梁结构。本文对小梁结构的设计和制造、力学性能以及支架的渐进破坏行为和失效机制进行了比较。
EBM 制造的骨小梁的实际孔隙率低于设计值，承载能力与结构的孔隙率有关。结构的孔隙率越大，刚度越小，承载能力越差。小梁结构在压缩下的断裂界面与压缩轴方向成 45 度角，符合特雷斯卡屈服准则。模仿小梁的单元是各向异性的。在准静态加载下，加载速度对骨小梁试件的力学性能没有影响。在金属工作空间的不同方向和位置，力学性能没有差异。支架的弹性模量降低了 96%-93%，强度降低了 96%-91%，与钛合金致密金属结构相比。单元重复支架的表观弹性模量为 0.39-0.618GPa，接近天然骨，可降低应力屏蔽。
我们系统地研究了 3D 打印模仿小梁骨的钛合金支架的结构设计、制造和力学行为。这项研究将有助于应用具有适当结构和功能的假体。
