The Quantification of Physiologically Relevant Cross-Shear Wear Phenomena on Orthopaedic Bearing Materials Using the MAX-Shear Wear Testing System

[+] Author and Article Information
Matthew R. Gevaert, Martine LaBerge, Jennifer M. Gordon

Department of Bioengineering, Clemson University, Clemson, South Carolina 29634 Phone: 864-656-4178, Fax: 864-656-4466

John D. DesJardins

Department of Bioengineering, Clemson University, Clemson, South Carolina 29634 Phone: 864-656-4178, Fax: 864-656-4466jdesjar@ clemson.edu

J. Tribol 127(4), 740-749 (Jun 01, 2005) (10 pages) doi:10.1115/1.2000272 History: Received February 24, 2004; Revised June 01, 2005

Background: The occurrence of multi-directional sliding motion between total knee replacement bearing surfaces is theorized to be a primary wear and failure mechanism of ultra-high molecular weight poly(ethylene) (UHMWPE). To better quantify the tribologic mechanisms of this cross-shear wear, the MAX-Shear wear-testing system was developed to evaluate candidate biomaterials under controlled conditions of cross-shear wear. Method of approach: A computer controlled traveling x-y stage under a 3 degree-of-freedom statically loaded pin is used to implement the complex multi-directional motion pathways observed during TKR wear simulation. A MHz collection of dynamic x-y friction was available on all six environmentally controlled stations. The functionality of this testing platform was proven in a 100,000 cycle, 11.6 MPa, wear test using 15.0 mm diameter polished stainless steel spheres against flat GUR4150 UHMWPE. A five-pointed star wear pattern was used to incorporate the physiologically relevant cross-shear sliding conditions of stop/start, 50mms entraining velocity and five crossing angles of 72°. Using normalized volumetric reconstruction of the resulting surface damage, a direct quantitative relationship between linear and cross-shear surface damage intensity was obtained. Results: Cross-shear surface damage volume loss was found to be 2.94 (±0.88) times that associated with linear sliding under identical tribologic conditions. SEM analysis of linear wear damage showed consistent fibril orientation along the direction of sliding while cross-shear wear damage showed multi-directional fibril orientations and increased surface roughness. Significant increases in discrete crossing-point friction coefficients were recorded throughout testing. Conclusions: This scientific approach to quantifying the tribologic effects of cross-shear provides fundamental wear mechanism data that are critical in evaluating potential biomaterials for use as in vivo bearings. Relevant multi-axis, cross-shear wear testing is necessary to provide quantifiable measures of complex biomaterials wear phenomena.

Copyright © 2005 by American Society of Mechanical Engineers
Your Session has timed out. Please sign back in to continue.



Grahic Jump Location
Figure 1

The MAX-Shear wear testing system

Grahic Jump Location
Figure 2

A close-up view of one wear testing station showing the pin and frictional force load cell array configuration

Grahic Jump Location
Figure 3

Five-pointed star wear testing pathway

Grahic Jump Location
Figure 4

Star-shaped damage track on UHMWPE sample, shown magnified at 4×. All crossing locations within the star experience similar damage, as did all five star points. Infrequent closed-loop trajectory corrections during testing caused star-point to star-point profile corrections, resulting in the effect of a pentagram formed by the points of the star.

Grahic Jump Location
Figure 5

Surface profilometry scan (r) showing typical area of cross shear damage (profilometry magnification at 5×; FOV 0.93×1.25mm)

Grahic Jump Location
Figure 6

Sample friction trace showing stop / starts (# indicates one of five regions) and crossing points (× indicates one of five sets of double peaks created by cross pathway transients) at 0.2 km cycles

Grahic Jump Location
Figure 7

SEM images of UHMWPE specimens: orientation of linear damage track(s) shown by white arrow. Orientation A: Cross Shear at low (40×) magnification. B: Fibrils aligned parallel to damage track (3,000×). C: Fracture within wear track (10,000×). D: Cobblestone wear within cross shear, close to transition zone (5,000×). E: Smearing of larger fibrils within center of cross shear zone (10,000×).

Grahic Jump Location
Figure 8

Summary of wear test methods. Symbols ∘∕• indicate absence / presence of shear.

Grahic Jump Location
Figure 9

Circularly translating pin-on-disk motion, adapted from Saikko (16). The net effect of the translation is a circular wear track on the disk, represented on the far right.




Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In