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Results for “Friction”

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PubMed2003

The effect of frictional heating and forced cooling on the serum lubricant and wear of UHMW polyethylene cups against cobalt-chromium and zirconia balls.

Hip simulator tests of femoral balls of cobalt-chromium alloy or zirconia against acetabular cups of UHMW polyethylene were run with and without a coolant circulated inside the femoral balls. Without cooling, the wear of polyethylene against zirconia was about 48% lower than with cobalt-chromium alloy, but the steady-state temperature of the zirconia ball was higher (55 degrees C vs. 41 degrees C), and there was more precipitation of protein from the serum, which sometimes formed an adherent layer on the surface of the zirconia. Circulating coolant at 1-20 degrees C markedly reduced the bearing temperatures and the protein precipitation. With coolant at 4 degrees C, wear of the polyethylene against cobalt-chromium alloy was about 26% lower than against zirconia, but the macroscopic and microscopic appearance of the worn polyethylene surfaces were unlike that typically generated in vivo. With or without coolant, the morphology of the polyethylene wear debris was comparable to that generated in vivo, but the ratio of fibrillar to granular debris was higher at the reduced temperature. These results suggested that circulating coolant at an appropriate temperature could avoid overheating (due to non-stop running of the simulator), preventing excessive protein precipitation while providing wear surfaces and wear debris with morphologies closely comparable to those generated in vivo.

Artifacts↗
PubMedDate not supplied

[Macerated human hip bone preparation as a substitute for fresh frozen preparations for testing the primary stability and frictional torques of cementless hip cups].

AIM: The aim of the study was to validate macerated human acetabuli as replacement for fresh frozen preparations for testing primary stability and the screwing in moments of cementless threaded hip cups. METHOD: Three fresh frozen human pelvis were tested. One half of each pelvis was macerated whereas the other half was preserved as fresh frozen preparation. In the side of every pelvis the moments of screwing-in, the micromotions, the maximum expressing force and the maximum pull-out torque were determined. RESULTS: The screwing in moments, the maximum expressing forces and the maximum pull-out torques did not change. The micromotions were reduced to half. CONCLUSION: Considering the reduction of the micromotions, macerated human acetabuli are valid replacements for fresh frozen preparations for testing the primary stability and the screwing-in behaviour of screwed pans.

Cementation↗
PubMed1998

Locomotion: dealing with friction.

To move on land, in water, or in the air, even at constant speed and at the same level, always requires an expenditure of energy. The resistance to motion that has to be overcome is of many different kinds depending on size, speed, and the characteristics of the medium, and is a fascinating subject in itself. Even more interesting are nature's stratagems and solutions toward minimizing the effort involved in the locomotion of different types of living creatures, and humans' imitations and inventions in an attempt to do at least as well.

Animals↗