The influence of clearance on friction, lubrication and squeaking in large diameter metal-on-metal hip replacements

Large diameter metal-on-metal bearings (MOM) are becoming increasingly popular, addressing the needs of young and more active patients. Clinical data has shown excellent short-to-mid-term results, though incidences of transient squeaking have been noted between implantation and up to 2 years post-operative. Geometric design features, such as clearance, have been significant in influencing the performance of the bearings. Sets of MOM bearings with different clearances were investigated in this study using a hip friction simulator to examine the influence of clearance on friction, lubrication and squeaking. The friction factor was found to be highest in the largest clearance bearings under all test conditions. The incidence of squeaking was also highest in the large clearance bearings, with all bearings in this group squeaking throughout the study. A very low incidence of squeaking was observed in the other two clearance groups. The measured lubricating film was found to be lowest in the large clearance bearings. This study suggests that increasing the bearing clearance results in reduced lubricant film thickness, increased friction and an increased incidence of squeaking

Simultaneous temperature and refractive index measurements using a 3°slanted multimode fiber Bragg grating

Author name used in this publication: M. S. DemokanAuthor name used in this publication: W. Jin2005-2006 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Temperature-insensitive interferometer using a highly birefringent photonic crystal fiber loop mirror

Author name used in this publication: M. S. Demokan2004-2005 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Fusion splicing photonic crystal fibers and conventional single-mode fibers : microhole collapse effect

Author name used in this publication: M. S. Demokan2007-2008 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Designing SSI clusters with hierarchical checkpointing and single I/O space

Adopting a new hierarchical checkpointing architecture, the authors develop a single I/O address space for building highly available clusters of computers. They propose a systematic approach to achieving a single system image by integrating existing middleware support with the newly developed features.published_or_final_versio

Strain and temperature characteristics of a long-period grating written in a photonic crystal fiber and its application as a temperature-insensitive strain sensor

Author name used in this publication: M. S. Demokan2007-2008 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Quantification of the effect of cross-shear and applied nominal contact pressure on the wear of moderately cross-linked polyethylene

Polyethylene wear is a great concern in total joint replacement. It is now considered a major limiting factor to the long life of such prostheses. Cross-linking has been introduced to reduce the wear of ultra-high-molecular-weight polyethylene (UHMWPE). Computational models have been used extensively for wear prediction and optimization of artificial knee designs. However, in order to be independent and have general applicability and predictability, computational wear models should be based on inputs from independent experimentally determined wear parameters (wear factors or wear coefficients). The objective of this study was to investigate moderately cross-linked UHMWPE, using a multidirectional pin-on-plate wear test machine, under a wide range of applied nominal contact pressure (from 1 to 11 MPa) and under five different kinematic inputs, varying from a purely linear track to a maximum rotation of ±55°. A computational model, based on a direct simulation of the multidirectional pin-on-plate wear tester, was developed to quantify the degree of cross-shear (CS) of the polyethylene pins articulating against the metallic plates. The moderately cross-linked UHMWPE showed wear factors less than half of that reported in the literature for the conventional UHMWPE, under the same loading and kinematic inputs. In addition, under high applied nominal contact stress, the moderately cross-linked UHMWPE wear showed lower dependence on the degree of CS compared to that under low applied nominal contact stress. The calculated wear coefficients were found to be independent of the applied nominal contact stress, in contrast to the wear factors that were shown to be highly pressure dependent. This study provided independent wear data for inputs into computational models for moderately cross-linked polyethylene and supported the application of wear coefficient–based computational wear models

Effect of a nonlinear photonic crystal fiber on the noise characterization of a distributed Raman amplifier

Author name used in this publication: M. S. Demokan2004-2005 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Studies on strain and temperature characteristics of a slanted multimode fiber Bragg grating and its application in multiwavelength fiber Raman ring laser

Author name used in this publication: M. S. Demokan2005-2006 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe