Zhao S, Li S J, Hou W T, Hao Y L, Yang R, Misra R D K
Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016, China.
Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016, China.
J Mech Behav Biomed Mater. 2016 Jun;59:251-264. doi: 10.1016/j.jmbbm.2016.01.034. Epub 2016 Feb 12.
Additive manufacturing technique is a promising approach for fabricating cellular bone substitutes such as trabecular and cortical bones because of the ability to adjust process parameters to fabricate different shapes and inner structures. Considering the long term safe application in human body, the metallic cellular implants are expected to exhibit superior fatigue property. The objective of the study was to study the influence of cell shape on the compressive fatigue behavior of Ti-6Al-4V mesh arrays fabricated by electron beam melting. The results indicated that the underlying fatigue mechanism for the three kinds of meshes (cubic, G7 and rhombic dodecahedron) is the interaction of cyclic ratcheting and fatigue crack growth on the struts, which is closely related to cumulative effect of buckling and bending deformation of the strut. By increasing the buckling deformation on the struts through cell shape design, the cyclic ratcheting rate of the meshes during cyclic deformation was decreased and accordingly, the compressive fatigue strength was increased. With increasing bending deformation of struts, fatigue crack growth in struts contributed more to the fatigue damage of meshes. Rough surface and pores contained in the struts significantly deteriorated the compressive fatigue strength of the struts. By optimizing the buckling and bending deformation through cell shape design, Ti-6Al-4V alloy cellular solids with high fatigue strength and low modulus can be fabricated by the EBM technique.
增材制造技术是一种很有前景的制造多孔骨替代物（如松质骨和皮质骨）的方法，因为它能够调整工艺参数以制造不同的形状和内部结构。考虑到在人体中的长期安全应用，金属多孔植入物有望展现出优异的疲劳性能。本研究的目的是研究单元形状对通过电子束熔炼制造的Ti-6Al-4V网格阵列压缩疲劳行为的影响。结果表明，三种网格（立方、G7和菱形十二面体）的潜在疲劳机制是支柱上循环棘轮效应与疲劳裂纹扩展的相互作用，这与支柱的屈曲和弯曲变形的累积效应密切相关。通过单元形状设计增加支柱上的屈曲变形，网格在循环变形过程中的循环棘轮速率降低，相应地，压缩疲劳强度提高。随着支柱弯曲变形的增加，支柱中的疲劳裂纹扩展对网格疲劳损伤的贡献更大。支柱中包含的粗糙表面和孔隙显著降低了支柱的压缩疲劳强度。通过单元形状设计优化屈曲和弯曲变形，可以通过电子束熔炼技术制造出具有高疲劳强度和低模量的Ti-6Al-4V合金多孔固体。
