Department of Mechanical Engineering, University of Arkansas, Fayetteville, AR 72701, USA; Center for Advanced Surface Engineering, University of Arkansas, Fayetteville, AR 72701, USA.
Faculty of Mechanical Engineering, Institute of Machine and Industrial Design, Brno University of Technology, Technická 2896/2, 616 69 Brno, Czech Republic.
J Mech Behav Biomed Mater. 2018 May;81:120-129. doi: 10.1016/j.jmbbm.2018.02.014. Epub 2018 Feb 17.
This study evaluates the impact of dimple shapes on lubricant film formation in artificial hip joints. Micro-dimples with 20-50 µm lateral size and 1 ± 0.2 µm depths were fabricated on CrCoMo hip joint femoral heads using a picosecond laser. Tribological studies were performed using a pendulum hip joint simulator to apply continuous swing flexion-extension motions. The results revealed a significantly enhanced lubricant film thickness (≥ 500 nm) with micro-dimpled prosthesis heads at equilibrium position after the lubricant film has fully developed. The average lubricant film thickness of dimpled prostheses with square- and triangular-shaped dimple arrays over time is about 3.5 that of the non-dimpled prosthesis (204 nm). Remarkably, the prosthesis with square-shaped dimple arrays showed a very fast lubricant film formation reaching their peak values within 0.5 s of pendulum movement, followed by prosthesis with triangular-shaped dimple arrays with a transition period of 42.4 s. The fully developed lubricant film thicknesses (≥ 700 nm) are significantly higher than the surface roughness (≈ 25 nm) demonstrating a hydrodynamic lubrication. Hardly any scratches appeared on the post-experimental prosthesis with square-shaped dimple array and only a few scratches were found on the post-experimental prosthesis with triangular-shaped dimple arrays. Thus, prostheses with square-shaped dimple arrays could be a potential solution for durable artificial hip joints.
本研究评估了微凹坑形状对人工髋关节中润滑膜形成的影响。使用皮秒激光在 CrCoMo 髋关节股骨头表面加工了具有 20-50 µm 横向尺寸和 1 ± 0.2 µm 深度的微凹坑。使用摆式髋关节模拟器进行摩擦学研究，以施加连续的摆动屈伸运动。结果表明，在完全形成润滑膜后，具有微凹坑的假体头部在平衡位置处的润滑膜厚度显著增加（≥500nm）。具有方形和三角形凹坑阵列的微凹坑假体的平均润滑膜厚度随时间的变化约为无凹坑假体的 3.5 倍（204nm）。值得注意的是，具有方形凹坑阵列的假体在摆锤运动 0.5s 内迅速形成润滑膜，达到峰值，然后是具有三角形凹坑阵列的假体，过渡时间为 42.4s。完全形成的润滑膜厚度（≥700nm）明显高于表面粗糙度（≈25nm），表明存在流体动力润滑。具有方形凹坑阵列的实验后假体上几乎没有出现划痕，而具有三角形凹坑阵列的实验后假体上只有少数划痕。因此，具有方形凹坑阵列的假体可能是耐用人工髋关节的潜在解决方案。
