Wear of conventional UHMWPE has historically been recognized as the primary cause of soft-on-hard hip implant failure and revision [1]. Recent understandings [2-3] of the wear mechanisms of UHMWPE-metal coupling highlighted the fundamental role of multi-directional sliding, known as the Cross-Shear (CS) effect. Experimental observations stressed that when polyethylene is subjected to multi-directional sliding against a metallic counter face, the polymeric chains acquire a principal molecular orientation (PMO) in whose direction the surface results harder and the wear resistance increases. On the opposite, in the direction perpendicular to the PMO, i.e. the CS direction, there is a strain softening phenomenon responsible for the detachment of wear debris from the worn surfaces. The concept is schematically represented in Figure 1. However experimental observations were based on pin-on-plate or on pin-on-disc specimens, from which theoretical wear laws were derived. In this study worn cups of UHMWPE were observed at the Atomic Force Microscopy (AFM) to assess the local orientation of the molecules at some reference points of the component. A theoretical model, derived from the ones presented in [4], was also defined.
Experimental and numerical analysis of UHMWPE acetabular cups after wear test: a preliminary study
DI PUCCIO, FRANCESCA;MATTEI, LORENZA;D'ACUNTO, MARIO;ANIS ISHAK NAKHLA, RANDA;
2013-01-01
Abstract
Wear of conventional UHMWPE has historically been recognized as the primary cause of soft-on-hard hip implant failure and revision [1]. Recent understandings [2-3] of the wear mechanisms of UHMWPE-metal coupling highlighted the fundamental role of multi-directional sliding, known as the Cross-Shear (CS) effect. Experimental observations stressed that when polyethylene is subjected to multi-directional sliding against a metallic counter face, the polymeric chains acquire a principal molecular orientation (PMO) in whose direction the surface results harder and the wear resistance increases. On the opposite, in the direction perpendicular to the PMO, i.e. the CS direction, there is a strain softening phenomenon responsible for the detachment of wear debris from the worn surfaces. The concept is schematically represented in Figure 1. However experimental observations were based on pin-on-plate or on pin-on-disc specimens, from which theoretical wear laws were derived. In this study worn cups of UHMWPE were observed at the Atomic Force Microscopy (AFM) to assess the local orientation of the molecules at some reference points of the component. A theoretical model, derived from the ones presented in [4], was also defined.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
