The Experts below are selected from a list of 843 Experts worldwide ranked by ideXlab platform
Allan Avram Edidin - One of the best experts on this subject based on the ideXlab platform.
-
surface morphology and wear mechanisms of four clinically relevant biomaterials after hip simulator testing
Journal of Biomedical Materials Research, 2000Co-Authors: S M Kurtz, Christopher L. Muhlstein, Allan Avram EdidinAbstract:The surfaces of worn components hold clues to the underlying wear mechanisms. Previous evidence suggested that the absolute wear rates of acetabular components in a hip simulator were related to Mechanical behavior; we hypothesized that the surface morphology of the liners might also be sensitive to Mechanical properties. A noncontact, three-dimensional surface topography measurement system based on white light interferometry was used to quantify the surface morphology of ultra-high molecular weight polyethylene, polytetrafluoroethylene, high-density polyethylene, and polyacetal liners, and their corresponding femoral heads, after 3 million cycles in a multi-directional hip simulator. Comparisons were made with the fatigue soaked and control (as machined) components. Statistically significant power law relationships were observed between the arithmetic mean surface roughness (Ra) of the worn acetabular liners and the volumetric wear rate in the hip simulator (p < 0.01, r2 = 0.52). Significant relationships were also observed between Ra and the elastic and large Deformation Mechanical behavior of the liner materials, measured directly from the wear-tested liners using the small punch test (p < 0.01, r2 = 0.54–0.81). The results support the hypothesis that wear mechanisms of acetabular liners during hip simulator testing are related to surface morphology in conjunction with the Mechanical behavior of the polymeric materials. © 2000 John Wiley & Sons, Inc. J Biomed Mater Res, 52, 447–459, 2000.
-
influence of Mechanical behavior on the wear of 4 clinically relevant polymeric biomaterials in a hip simulator
Journal of Arthroplasty, 2000Co-Authors: Allan Avram Edidin, S M KurtzAbstract:Abstract The elastic and large-Deformation Mechanical behavior of 4 materials with known clinical performance was examined and correlated with the wear behavior in a hip simulator. Acetabular liners of a commercially available design were machined from ultra-high molecular weight polyethylene (UHMWPE), high-density polyethylene (HDPE), polytetrafluoroethylene (PTFE), and polyacetal and wear tested in a multidirectional hip joint simulator. Elastic and large-Deformation Mechanical behavior was directly measured from the wear-tested liners using the small punch test. The finite element method was used to compute elastic modulus from the measured small punch test initial stiffness, and the contact stress for the liners was calculated using the theory of elasticity solution. Positive, statistically significant correlations were observed between the hip simulator wear rate and the initial peak load, ultimate load, and work to failure from the small punch test. Negative correlations were observed between the wear rate and the elastic modulus and contact stress. The results of this study support the hypothesis that the large-Deformation Mechanical behavior of a polymer plays a greater role in the wear mechanisms prevalent in total hip replacements than the elastic behavior.
-
The relationship between the clinical performance and large Deformation Mechanical behavior of retrieved UHMWPE tibial inserts.
Biomaterials, 2000Co-Authors: S M Kurtz, Clare M. Rimnac, Lisa A. Pruitt, C. W. Jewett, Victor M. Goldberg, Allan Avram EdidinAbstract:Abstract Many aspects of the proposed relationship between material properties and clinical performance of UHMWPE components remain unclear. In this study, we explored the hypothesis that the clinical performance of tibial inserts is directly related to its large-Deformation Mechanical behavior measured near the articulating surface. Retrieval analysis was performed on three conventional UHMWPE and three Hylamer™-M tibial components of the same design and manufacturer. Samples of material were then obtained from the worn regions of each implant and subjected to Mechanical characterization using the small punch test. Statistically significant relationships were observed between the metrics of the small punch test and the total damage score and the burnishing damage score of the implants. We also examined the near-surface morphology of the retrievals using transmission electron microscopy. TEM analysis revealed lamellar alignment at and below the wear surfaces of the conventional UHMWPE retrievals up to a maximum depth of approximately 8 μm, consistent with large-Deformation crystalline plasticity. The depth of the plasticity-induced damage layer varied not only between the retrievals, but also between the conventional UHMWPE and Hylamer™-M components. Thus, the results of this study support the hypothesis that the clinical performance of UHMWPE tibial inserts is related to the large-Deformation Mechanical behavior measured near the articulating surface.
S M Kurtz - One of the best experts on this subject based on the ideXlab platform.
-
Prediction of multiaxial Mechanical behavior for conventional and highly crosslinked UHMWPE using a hybrid constitutive model
Biomaterials, 2003Co-Authors: J.s. Bergström, Clare M. Rimnac, S M KurtzAbstract:The development of theoretical failure, fatigue, and wear models for ultra-high molecular weight polyethylene (UHMWPE) used in joint replacements has been hindered by the lack of a validated constitutive model that can accurately predict large Deformation Mechanical behavior under clinically relevant, multiaxial loading conditions. Recently, a new Hybrid constitutive model for unirradiated UHMWPE was developed Bergstrom et al., (Biomaterials 23 (2002) 2329) based on a physics-motivated framework which incorporates the governing micro-mechanisms of polymers into an effective and accurate continuum representation. The goal of the present study was to compare the predictive capability of the new Hybrid model with the J2-plasticity model for four conventional and highly crosslinked UHMWPE materials during multiaxial loading. After calibration under uniaxial loading, the predictive capabilities of the J2-plasticity and Hybrid model were tested by comparing the load-displacement curves from experimental multiaxial (small punch) tests with simulated load-displacement curves calculated using a finite element model of the experimental apparatus. The quality of the model predictions was quantified using the coefficient of determination (r2). The results of the study demonstrate that the Hybrid model outperforms the J2-plasticity model both for combined uniaxial tension and compression predictions and for simulating multiaxial large Deformation Mechanical behavior produced by the small punch test. The results further suggest that the parameters of the HM may be generalizable for a wide range of conventional, highly crosslinked, and thermally treated UHMWPE materials, based on the characterization of four material properties related to the elastic modulus, yield stress, rate of strain hardening, and locking stretch of the polymer chains. Most importantly, from a practical perspective, these four key material properties for the Hybrid constitutive model can be measured by relatively simple uniaxial tension or compression tests.
-
surface morphology and wear mechanisms of four clinically relevant biomaterials after hip simulator testing
Journal of Biomedical Materials Research, 2000Co-Authors: S M Kurtz, Christopher L. Muhlstein, Allan Avram EdidinAbstract:The surfaces of worn components hold clues to the underlying wear mechanisms. Previous evidence suggested that the absolute wear rates of acetabular components in a hip simulator were related to Mechanical behavior; we hypothesized that the surface morphology of the liners might also be sensitive to Mechanical properties. A noncontact, three-dimensional surface topography measurement system based on white light interferometry was used to quantify the surface morphology of ultra-high molecular weight polyethylene, polytetrafluoroethylene, high-density polyethylene, and polyacetal liners, and their corresponding femoral heads, after 3 million cycles in a multi-directional hip simulator. Comparisons were made with the fatigue soaked and control (as machined) components. Statistically significant power law relationships were observed between the arithmetic mean surface roughness (Ra) of the worn acetabular liners and the volumetric wear rate in the hip simulator (p < 0.01, r2 = 0.52). Significant relationships were also observed between Ra and the elastic and large Deformation Mechanical behavior of the liner materials, measured directly from the wear-tested liners using the small punch test (p < 0.01, r2 = 0.54–0.81). The results support the hypothesis that wear mechanisms of acetabular liners during hip simulator testing are related to surface morphology in conjunction with the Mechanical behavior of the polymeric materials. © 2000 John Wiley & Sons, Inc. J Biomed Mater Res, 52, 447–459, 2000.
-
influence of Mechanical behavior on the wear of 4 clinically relevant polymeric biomaterials in a hip simulator
Journal of Arthroplasty, 2000Co-Authors: Allan Avram Edidin, S M KurtzAbstract:Abstract The elastic and large-Deformation Mechanical behavior of 4 materials with known clinical performance was examined and correlated with the wear behavior in a hip simulator. Acetabular liners of a commercially available design were machined from ultra-high molecular weight polyethylene (UHMWPE), high-density polyethylene (HDPE), polytetrafluoroethylene (PTFE), and polyacetal and wear tested in a multidirectional hip joint simulator. Elastic and large-Deformation Mechanical behavior was directly measured from the wear-tested liners using the small punch test. The finite element method was used to compute elastic modulus from the measured small punch test initial stiffness, and the contact stress for the liners was calculated using the theory of elasticity solution. Positive, statistically significant correlations were observed between the hip simulator wear rate and the initial peak load, ultimate load, and work to failure from the small punch test. Negative correlations were observed between the wear rate and the elastic modulus and contact stress. The results of this study support the hypothesis that the large-Deformation Mechanical behavior of a polymer plays a greater role in the wear mechanisms prevalent in total hip replacements than the elastic behavior.
-
The relationship between the clinical performance and large Deformation Mechanical behavior of retrieved UHMWPE tibial inserts.
Biomaterials, 2000Co-Authors: S M Kurtz, Clare M. Rimnac, Lisa A. Pruitt, C. W. Jewett, Victor M. Goldberg, Allan Avram EdidinAbstract:Abstract Many aspects of the proposed relationship between material properties and clinical performance of UHMWPE components remain unclear. In this study, we explored the hypothesis that the clinical performance of tibial inserts is directly related to its large-Deformation Mechanical behavior measured near the articulating surface. Retrieval analysis was performed on three conventional UHMWPE and three Hylamer™-M tibial components of the same design and manufacturer. Samples of material were then obtained from the worn regions of each implant and subjected to Mechanical characterization using the small punch test. Statistically significant relationships were observed between the metrics of the small punch test and the total damage score and the burnishing damage score of the implants. We also examined the near-surface morphology of the retrievals using transmission electron microscopy. TEM analysis revealed lamellar alignment at and below the wear surfaces of the conventional UHMWPE retrievals up to a maximum depth of approximately 8 μm, consistent with large-Deformation crystalline plasticity. The depth of the plasticity-induced damage layer varied not only between the retrievals, but also between the conventional UHMWPE and Hylamer™-M components. Thus, the results of this study support the hypothesis that the clinical performance of UHMWPE tibial inserts is related to the large-Deformation Mechanical behavior measured near the articulating surface.
Kurt Ingar Draget - One of the best experts on this subject based on the ideXlab platform.
-
Mechanical properties of mammalian and fish gelatins based on their weight average molecular weight and molecular weight distribution
Food Hydrocolloids, 2009Co-Authors: Jonhard Eysturskarð, Ingvild Johanne Haug, Annsissel Teialeret Ulset, Kurt Ingar DragetAbstract:Acid porcine skin gelatins (type A), lime bone gelatins (type B) and gelatin from different cold water fish species were compared on the basis of low Deformation Mechanical properties, Bloom value, weight average molecular weight, molecular weight distribution and isoelectric point. The dynamic storage modulus and Bloom value for all types of gelatin increased with increasing weight average molecular weight. Type A and type B gelatins with similar weight average molecular weight exhibited different dynamic storage modulus (G') and different Bloom values. This is most probably due to a different molecular weight distribution as well as the presence of different hydrolytic fragments. The present study suggests that it may be possible to improve the Mechanical properties by removing low molecular weight molecules from a gelatin sample. The Bloom values for gelatin from haddock, saithe and cod were determined to be 200, 150 and 100 g from a linear correlation between G' and Bloom.
Jonhard Eysturskarð - One of the best experts on this subject based on the ideXlab platform.
-
Mechanical properties of mammalian and fish gelatins based on their weight average molecular weight and molecular weight distribution
Food Hydrocolloids, 2009Co-Authors: Jonhard Eysturskarð, Ingvild Johanne Haug, Annsissel Teialeret Ulset, Kurt Ingar DragetAbstract:Acid porcine skin gelatins (type A), lime bone gelatins (type B) and gelatin from different cold water fish species were compared on the basis of low Deformation Mechanical properties, Bloom value, weight average molecular weight, molecular weight distribution and isoelectric point. The dynamic storage modulus and Bloom value for all types of gelatin increased with increasing weight average molecular weight. Type A and type B gelatins with similar weight average molecular weight exhibited different dynamic storage modulus (G') and different Bloom values. This is most probably due to a different molecular weight distribution as well as the presence of different hydrolytic fragments. The present study suggests that it may be possible to improve the Mechanical properties by removing low molecular weight molecules from a gelatin sample. The Bloom values for gelatin from haddock, saithe and cod were determined to be 200, 150 and 100 g from a linear correlation between G' and Bloom.
Ian W. Hunter - One of the best experts on this subject based on the ideXlab platform.
-
Large Deformation Mechanical testing of biological membranes using speckle interferometry in transmission. I: Experimental apparatus.
Applied Optics, 1997Co-Authors: Paul G. Charette, Ian W. Hunter, Peter HunterAbstract:This paper describes an apparatus designed to study large Mechanical Deformations in biological membranes. The task of Mechanically characterizing biological membranes is challenging because of the anisotropic and nonlinear nature of their material properties. The apparatus described here is well suited to the task because it uses speckle interferometry to measure in-plane displacements in a distributed fashion and has multiple degrees of freedom in the applied stress mechanism. In this way few a priori assumptions or restrictions are imposed on the applied stress and strain fields. The interferometer operates in transmission mode to increase the light efficiency of the system since the sample biological membranes are translucent and reflect little light. The experimental results confirm that the strain fields in the biological membranes that are generated in the experiments are highly nonuniform and cannot be properly estimated from a small number of point measurements.
-
Large Deformation Mechanical testing of biological membranes using speckle interferometry in transmission. II: Finite element modeling.
Applied Optics, 1997Co-Authors: Paul G. Charette, Peter Hunter, Ian W. HunterAbstract:In holography and speckle interferometry the measurement range is generally limited by the greatest number of fringes that can be resolved in a single image. As a result these techniques have been generally confined to small displacement measurement applications. In the case of out-of-plane measurements one can overcome this limitation by simply adding incremental measurements at individual detector pixels. In the case of in-plane measurements, however, summing incremental measurements is not a straightforward procedure since the interference pattern moves laterally across the detector as the material deforms. We describe a modeling technique based on finite elements which solves this problem. In combination with a full field method such as holography or speckle interferometry, it provides a very sensitive measurement technique with dense spatial sampling and large dynamic range. Experimental results of speckle interferometry operating in transmission to measure in-plane displacements of biological membranes are presented, where total material displacements are of the order of millimeters. The results also demonstrate how the finite strain tensor is calculated analytically from the data at any point on the material.