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首页> 外文学位 >Dynamic measurements of lubrication film thickness of UHMWPE contacts for total joint replacements.
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Dynamic measurements of lubrication film thickness of UHMWPE contacts for total joint replacements.

机译：动态测量UHMWPE触头的润滑膜厚度，以更换全部接头。

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摘要

A new contact sensing technology previously developed in the Biotribology Laboratory at Clemson University was further studied, evaluated, and characterized to extend its use to the measurement of lubricating film thickness. First, the laboratory's force-controlled knee joint simulator was used while dynamic contact pressure measurements under both dry and lubricated conditions were made using the sensor technology employed in two different artificial knee implant geometries. Each implant was machined by the manufacturer from custom blocks of ultra high molecular weight polyethylene (UHMWPE) containing a grid of discrete sensing regions. The difference between the dry and lubricated contact areas measured at different phases of the gait cycle for each implant suggested that the dynamic lubrication thickness might also be able to be quantified by the sensing technology. To gain insight on this, simplified contacts of metal on UHMWPE were studied with the sensing technology being employed in the UHMWPE side of the contacts. First, the UHMWPE sensor's outputs were studied under static, lubricated conditions while the surface separation was directly controlled. The insights gained during the static testing were used to develop a more representative contact that was then characterized under hydrodynamic conditions. The experimental contact model was designed to mimic a single sensing point of the knee sensors used earlier in this study. It consisted of a UHMWPE sensor pin with a spherical tip sliding on a flat stainless steel counterpart with an implant-grade finish. Hydrodynamic motions were applied to the contact with the laboratory's custom-designed multi-axis pin on disk wear testing machine with friction measuring capabilities. To relate the sensor pin's output to the mode of lubrication, a Stribeck curve was experimentally developed and was used to determine the lambda (lambda) values specific to the UHMWPE on metal sliding point contact. It was found that the boundary lubrication regime existed for lambda < 1, mixed lubrication was present for 1 < lambda 3.5. Calibration equations relating the sensor's output to the film thickness were obtained using simple linear reciprocating motion, and it was found that in the boundary lubricated regime, the sensor's output was linearly related to the film thickness. It was also determined that for mixed and fluid film lubrication, the sensor's output was linear on a log-log scale to the film thickness; thus, there was a power-law relationship. Finally, the calibration equations were used to measure the lubricating film thickness of the UHMWPE contact in a clinically relevant, cross-path motion complete with sliding speeds relevant to the phases of gait where lubricating films can potentially exist for artificial knee joints. Two different loads were applied to the contact for these measurements. For the lightest load, mixed lubrication and HL were measured, and the film thickness varied from 2mum to over 10mum. With the higher load, the film thickness was seen to fall to 1mum for a small portion of the cycle, showing that the contact experienced the full range of lubrication modes from boundary to full hydrodynamic lubrication.*.;*This dissertation is a compound document (contains both a paper copy and a CD as part of the dissertation). The CD requires the following system requirements: Windows MediaPlayer or RealPlayer.
机译：先前在克莱姆森大学生物摩擦学实验室开发的一种新的接触传感技术已得到进一步研究，评估和表征，从而将其应用范围扩展到了润滑膜厚度的测量中。首先，使用实验室的受力控制的膝关节模拟器，同时使用两种不同的人工膝关节植入物几何结构中使用的传感器技术，在干燥和润滑条件下进行动态接触压力测量。每个植入物均由制造商从超高分子量聚乙烯（UHMWPE）的定制块中加工而成，该块包含离散的感应区域。对于每个植入物，在步态周期的不同阶段所测量的干接触面积与润滑接触面积之间的差异表明，动态润滑厚度也可以通过传感技术进行量化。为了对此有更深入的了解，对UHMWPE上的金属简化触点进行了研究，并在触点的UHMWPE侧采用了传感技术。首先，在静态，润滑条件下研究UHMWPE传感器的输出，同时直接控制表面分离。在静态测试中获得的见解被用于发展更具代表性的接触，然后在流体动力学条件下对其进行表征。实验接触模型旨在模拟本研究中较早使用的膝盖传感器的单个感应点。它由一个UHMWPE传感器销组成，该传感器销具有一个球形尖端，该球形尖端在带有植入物级表面的扁平不锈钢对应物上滑动。流体动力运动被应用到具有摩擦测量功能的磁盘磨损试验机上与实验室定制设计的多轴销的接触上。为了将传感器销的输出与润滑方式相关联，实验开发了一条Stribeck曲线，该曲线用于确定特定于UHMWPE的金属滑点接触的拉姆达（lambda）值。结果发现，对于λ<1，存在边界润滑机制，对于1 <λ3.5，存在混合润滑。使用简单的线性往复运动获得了将传感器的输出与薄膜厚度相关的校准方程，发现在边界润滑状态下，传感器的输出与薄膜厚度呈线性关系。还确定了对于混合和流体膜润滑，传感器的输出与膜厚成对数对数线性；因此，存在着权力-法律关系。最后，使用校准方程式来测量UHMWPE触点在临床上相关的交叉路径运动中的润滑膜厚度，该运动具有与步态阶段相关的滑动速度，在该阶段步态可能存在人工膝关节的润滑膜。对于这些测量，将两个不同的负载施加到触点上。对于最轻的负载，测量了混合润滑和HL，膜厚从2μm到10μm以上不等。在较高的载荷下，在整个循环的一小部分中，膜厚度都下降到了1μm，这表明接触经历了从边界润滑到完全流体动力润滑的所有润滑方式。*。** （作为论文的一部分，包含纸质副本和CD）。该CD需要满足以下系统要求：Windows MediaPlayer或RealPlayer。

著录项

  • 作者

    Clark, Andrew Chapman.;

  • 作者单位

    Clemson University.;

  • 授予单位 Clemson University.;
  • 学科 Engineering Biomedical.
  • 学位 Ph.D.
  • 年度 2007
  • 页码 209 p.
  • 总页数 209
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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