Hysteretic Heating During Cyclic Loading of Medical Grade Ultra High Molecular Weight Polyethylene (UHMWPE)

Galetz, Mathias C.; Goetz, Christian; Adam, Peter; Glatzel, Uwe

doi:10.1002/adem.200700274

Cited by 18 publications

(7 citation statements)

References 30 publications

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“…The maximum pressure according the hertzian equation is 14.5 MPa along with a contact width of 1.35 mm at peak load. A modulus of 200.000 MPa for CoCrMo and 600 MPa for UHMWPE and a Poisson ratio of 0.46 and 0.3 for the CoCrMo and the polyethylene, respectively, were used for the calculation [31,32].…”

Section: Self-made Tribological Testing Devicementioning

confidence: 99%

“…Unfortunately, a detailed determination of a pole figure was not possible due to the problem of the uneven surface profile after testing. The crystal orientation was compared with samples tested in unidirectional cyclic compression creep at 1 Hz in water at 23°C and 23 MPa for 300.000 cycles, as described in detail elsewhere [32]. One curve was derived in loading direction (from the top) and the other perpendicular to the loading direction (from the side).…”

Section: X-ray Diffraction (Xrd)mentioning

confidence: 99%

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Molecular Deformation Mechanisms in UHMWPE During Tribological Loading in Artificial Joints

Galetz

Glatzel

2010

Tribol Lett

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No clear picture of the deformation and wear mechanisms of Ultra High Molecular Weight Polyethylene (UHMWPE) in artificial knee joints exists up to today. Tribological tests were conducted under relevant loads and the worn samples were extensively studied by XRD, DSC, Raman, and SEM. It was shown that stresses close to the surface in areas where high relative velocity in combination with high normal loads are applied are most effective in changing the microstructure and therefore most detrimental to produce wear particles, while in the depth the same deformed structure as under unidirectional cyclic loading is found. A model was proposed which reflects the deformation at different zones in the depth of a tribologically loaded UHMWPE sample. This model shows amazing analogy to the orientation of collagen fibrils in natural cartilage.

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Section: Self-made Tribological Testing Devicementioning

confidence: 99%

Section: X-ray Diffraction (Xrd)mentioning

confidence: 99%

Molecular Deformation Mechanisms in UHMWPE During Tribological Loading in Artificial Joints

Galetz

Glatzel

2010

Tribol Lett

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“…Indeed, the main microstructural modifications under such wear conditions are considered to be a stretching of non‐crystalline regions, known as shear‐yielding, and the reorientation of crystalline lamellae,10 leading to the generation of a several micrometer thick transition region. This transition zone is characterized by a rearrangement of the originally randomly oriented lamellae into a wear‐induced preferential orientation.…”

Section: Resultsmentioning

confidence: 99%

“…Several lubrication conditions must be considered in vivo ranging from a well‐lubricated situation to a partially9 or even fully dry‐sliding situation in case of absent synovial fluid in the patients' TEP. In any scenario, the generated frictional heat in the prosthetic joint is not immediately dissipated and induces a local temperature rise 10. This facilitates tribological near‐surface microstructural reorganizations at the molecular and supramolecular scale in the semicrystalline UHMWPE with its strongly temperature‐dependent dynamic viscoelastic properties.…”

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confidence: 99%

Near‐Surface Microstructural Reorganization of UHMWPE under Cyclic Load – A Pilot Study

et al. 2011

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We report a depth‐resolved analysis of the microstructure of a bulge‐like failure in a medical grade ultra high molecular weight polyethylene (UHMWPE) implant material induced by a cyclic load. The depth‐dependent arrangement of the crystalline lamellae was analyzed by cross‐sectional transmission electron microscopy (TEM). The failure emerges at the top wear surface as an amorphous bulge with a maximum thickness of approximately 300 µm. A sharp interface below the bulge consists of an approximately 0.1 µm thick boundary layer with stacked lamellae with an outstanding degree of orientation perpendicular to the wear surface. The boundary layer is separated from the intact, unmodified base material with random lamellar orientation by an approximately 5 µm thick transition zone with a lamellar alignment perpendicular to the wear surface, which decreases toward the center of the UHMWPE test specimen. We further observed an overall decrease of lamellar thickness toward the wear surface within the influence zone. This indicates the strength and heterogeneity of the local dynamic stress field during cyclic wear and the ease for lamellar rearrangements presumably facilitated by a locally elevated temperature. We propose the bulge to originate from either wear material dragged along the wear surface or from a retransfer from the articulating counter surface, and discuss implications on the degree and relevance of adhesive wear. This study stresses the importance of the UHMWPE transfer material under such dynamic load conditions. Our approach seems suitable for investigating the mechanical aspect of failure mechanisms at the UHMWPE polymer biointerface under cyclic load.

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“…Therefore, it is important to perform fundamental investigations on the structure-property and property-performance relationships of the polymer in terms of dynamic and time-dependent properties. Currently, many efforts are being continuously made to investigate the mechanical properties of UHMWPE orthopedic biomaterials, such as fatigue [1][2][3][4][5], tribology [6][7][8][9], nano/microindentation [10][11][12], thermomechanical analysis (TMA) [13], and mechanical performance improvement [4,[14][15][16]. However, past studies have paid little attention to the viscoelastic behaviors of UHMWPE although the polymer exhibits creep and stress relaxation and is subjected constantly to dynamic load in its major application as orthopedic implants.…”

Section: Introductionmentioning

confidence: 99%

Viscoelastic Behaviors of Ultrahigh Molecular Weight Polyethylene Under Three-Point Bending and Indentation Loading

Deng

Uhrich

2009

J Biomater Appl

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Dynamic mechanical properties under three-point bending and deformation behavior under indentation loading of an ultrahigh molecular weight polyethylene (UHMWPE) were investigated in this study. Dependence of its viscoelastic properties on temperature, frequency, load level, specimen geometry and heating rates were examined. The results showed that temperature and frequency had significant effects on the response of UHMWPE to the dynamic load. With the increase in temperature, the storage modulus (E') was decreased and the loss angle (tan delta) was increased, indicating an increase in the trend in viscoelastic response of the polymer at high temperature. On the other hand, when frequency was increased, higher E' and lower tan delta were observed, suggesting that the material behaved more elastically. While the two heating rates of 5 degrees C/min and 10 degrees C/min had little effect on E' and tan delta, the load level significantly influenced the dynamic mechanical properties of the polymer. UHMWPE showed quite different responses at 0.5 and 20 Hz than at 1-10 Hz, which is worth further investigation. The results from indentation experiment showed that temperature, specimen geometry and load level had significant effects on the response of UHMWPE to the indentation load. With the increase in temperature, the penetration depth was increased, indicating an increase in the deformation trend in the polymer at high temperature. High load led to high penetration. The time-temperature superposition (TTS) method could be used to predict the long-term penetration behaviors of the polymer. From TTS analysis, the activation energy associated with penetration deformation was obtained. Further analysis showed that it might be possible to increase the resistance of UHMEPE to indentation deformation by increasing the thickness and/or decreasing the diameter of the polymer samples.

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Hysteretic Heating During Cyclic Loading of Medical Grade Ultra High Molecular Weight Polyethylene (UHMWPE)

Cited by 18 publications

References 30 publications

Molecular Deformation Mechanisms in UHMWPE During Tribological Loading in Artificial Joints

Molecular Deformation Mechanisms in UHMWPE During Tribological Loading in Artificial Joints

Near‐Surface Microstructural Reorganization of UHMWPE under Cyclic Load – A Pilot Study

Viscoelastic Behaviors of Ultrahigh Molecular Weight Polyethylene Under Three-Point Bending and Indentation Loading

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