Faculty of Mechanical, Maritime, and Materials Engineering, Delft University of Technology (TU Delft), Mekelweg 2, 2628 CD, Delft, The Netherlands; FT Innovations BV, Braamsluiper 1, 5831 PW Boxmeer, The Netherlands.
Mater Sci Eng C Mater Biol Appl. 2013 Dec 1;33(8):4849-58. doi: 10.1016/j.msec.2013.08.006. Epub 2013 Aug 13.
Porous titanium alloys are considered promising bone-mimicking biomaterials. Additive manufacturing techniques such as selective laser melting allow for manufacturing of porous titanium structures with a precise design of micro-architecture. The mechanical properties of selective laser melted porous titanium alloys with different designs of micro-architecture have been already studied and are shown to be in the range of mechanical properties of bone. However, the fatigue behavior of this biomaterial is not yet well understood. We studied the fatigue behavior of porous structures made of Ti6Al4V ELI powder using selective laser melting. Four different porous structures were manufactured with porosities between 68 and 84% and the fatigue S-N curves of these four porous structures were determined. The three-stage mechanism of fatigue failure of these porous structures is described and studied in detail. It was found that the absolute S-N curves of these four porous structures are very different. In general, given the same absolute stress level, the fatigue life is much shorter for more porous structures. However, the normalized fatigue S-N curves of these four structures were found to be very similar. A power law was fitted to all data points of the normalized S-N curves. It is shown that the measured data points conform to the fitted power law very well, R(2)=0.94. This power law may therefore help in estimating the fatigue life of porous structures for which no fatigue test data is available. It is also observed that the normalized endurance limit of all tested porous structures (<0.2) is lower than that of corresponding solid material (c.a. 0.4).
多孔钛合金被认为是有前途的仿生骨材料。增材制造技术（如选择性激光熔化）可制造具有精确微观结构设计的多孔钛结构。已经研究了具有不同微观结构设计的选择性激光熔化多孔钛合金的力学性能，结果表明其力学性能在骨的力学性能范围内。然而，这种生物材料的疲劳行为还没有被很好地理解。我们研究了使用选择性激光熔化制造的 Ti6Al4V ELI 粉末多孔结构的疲劳行为。制造了四种不同孔隙率在 68%至 84%之间的多孔结构，并确定了这四种多孔结构的疲劳 S-N 曲线。描述并详细研究了这四种多孔结构疲劳失效的三阶段机制。结果发现，这四种多孔结构的绝对 S-N 曲线非常不同。一般来说，在相同的绝对应力水平下，多孔结构的疲劳寿命要短得多。然而，这四种结构的归一化疲劳 S-N 曲线非常相似。对所有归一化 S-N 曲线数据点进行了幂律拟合。结果表明，测量数据点与拟合的幂律非常吻合，R(2)=0.94。因此，该幂律可用于估计尚无疲劳试验数据的多孔结构的疲劳寿命。还观察到，所有测试的多孔结构的归一化疲劳极限（<0.2）均低于相应的实心材料（约 0.4）。
