IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Tribology Wednesday Sessions
       Session TR+MM-WeA

Paper TR+MM-WeA8
Nanotribology of Total Joint Replacement Prosthesis (TJR)

Wednesday, October 31, 2001, 4:20 pm, Room 132

Session: Nanotribology
Presenter: S.P. Ho, Clemson University
Authors: S.P. Ho, Clemson University
R.W. Carpick, University of Wisconsin - Madison
T. Boland, Clemson University
P.F. Joseph, Clemson University
M. LaBerge, Clemson University
Correspondent: Click to Email
Atomic force microscope (AFM) was used to represent nanotribological asperity-to-asperity nanocontact between a cast CoCr alloy and an unsterilized surgical-grade direct compression molded ultra high molecular weight polyethylene (UHMWPE) of TJR prosthesis. UHMWPE is a semicrystalline material consisting of crystalline domains within an amorphous matrix. The primary dependence of friction upon normal load during an abrasive nanocontact may involve gross plastic deformation leading to plowing of UHMWPE surface. We have studied the nanotribological properties and evolution of plastic deformation of UHMWPE, to determine the precursors to wear particle formation in TJR prosthesis. It was hypothesized that variability in friction due to the individual nano-constituents in the semicrystalline polymer could cause a stress concentration leading to the generation of nanoscale wear debris particle; the originator for osteolysis in a total joint arthroplasty. Results from AFM analyses will be presented in this work to elucidate the average coefficient of friction and wear mechanisms and to reveal friction coefficients of the individual nano-constituents in the UHMWPE. Results showed that loading the nanocontact within the elastic regime resulted in an average coefficient of friction of 0.25+/-0.04. Higher normal load ranges revealed a sudden increase in lateral force indicating ploughing of the nanocontact, eventually leading to generation of nanoscale wear debris. The sudden increase in lateral force indicated that the UHMWPE plastically deforms causing an increase in contact area leading to an increase in lateral forces. We will present data supporting the individual contribution of crystalline and amorphous regions to the coefficient of friction for the purpose of understanding the observed plastic deformation at the modeled nanocontact of total joint replacement prosthesis (TJR).