Comparison of numerical methods for elastohydrodynamic lubrication analysis of metal-on-metal hip implants: Multi-grid verses Newton-Raphson

2007 ◽  
Vol 221 (2) ◽  
pp. 133-140 ◽  
Author(s):  
L. M. Gao ◽  
Q. E. Meng ◽  
F. C. Wang ◽  
P. R. Yang ◽  
Z. M. Jin
Keyword(s):  
Numerical Methods ◽  
Elastohydrodynamic Lubrication ◽  
Hip Implants ◽  
Metal On Metal ◽  
Newton Raphson

Effect of Wear of Bearing Surfaces on Elastohydrodynamic Lubrication of Metal-on-Metal Hip Implants

2005 ◽  
Vol 219 (5) ◽  
pp. 319-328 ◽  
Author(s):  
F Liu ◽  
Z M Jin ◽  
F Hirt ◽  
C Rieker ◽  
P Roberts ◽  
...  
Keyword(s):  
Film Thickness ◽  
Elastohydrodynamic Lubrication ◽  
Lubricant Film ◽  
Linear Wear ◽  
Wear Depth ◽  
Hip Implants ◽  
Bearing Surface ◽  
Lubricant Film Thickness ◽  
Hip Simulator ◽  
Metal On Metal

The effect of geometry change of the bearing surfaces owing to wear on the elastohydrodynamic lubrication (EHL) of metal-on-metal (MOM) hip bearings has been investigated theoretically in the present study. A particular MOM Metasul™ bearing (Zimmer GmbH) was considered, and was tested in a hip simulator using diluted bovine serum. The geometry of the worn bearing surface was measured using a coordinate measuring machine (CMM) and was modelled theoretically on the assumption of spherical geometries determined from the maximum linear wear depth and the angle of the worn region. Both the CMM measurement and the theoretical calculation were directly incorporated into the elastohydrodynamic lubrication analysis. It was found that the geometry of the original machined bearing surfaces, particularly of the femoral head with its out-of-roundness, could lead to a large reduction in the predicted lubricant film thickness and an increase in pressure. However, these non-spherical deviations can be expected to be smoothed out quickly during the initial running-in period. For a given worn bearing surface, the predicted lubricant film thickness and pressure distribution, based on CMM measurement, were found to be in good overall agreement with those obtained with the theoretical model based on the maximum linear wear depth and the angle of the worn region. The gradual increase in linear wear during the running-in period resulted in an improvement in the conformity and consequently an increase in the predicted lubricant film thickness and a decrease in the pressure. For the Metasul™ bearing tested in an AMTI hip simulator, a maximum total linear wear depth of approximately 13 μm was measured after 1 million cycles and remained unchanged up to 5 million cycles. This resulted in a threefold increase in the predicted average lubricant film thickness. Consequently, it was possible for the Metasul™ bearing to achieve a fluid film lubrication regime during this period, and this was consistent with the minimal wear observed between 1 and 5 million cycles. However, under adverse in vivo conditions associated with start-up and stopping and depleted lubrication, wear of the bearing surfaces can still occur. An increase in the wear depth beyond a certain limit was shown to lead to the constriction of the lubricant film around the edge of the contact conjunction and consequently to a decrease in the lubricant film thickness. Continuous cycles of a running-in wear period followed by a steady state wear period may be inevitable in MOM hip implants. This highlights the importance of minimizing the wear in these devices during the initial running-in period, particularly from design and manufacturing points of view.

Isoviscous elastohydrodynamic lubrication of circular point contacts with particular reference to metal-on-metal hip implants

2003 ◽  
Vol 217 (5) ◽  
pp. 397-402 ◽  
Author(s):  
D Jalali- Vahid ◽  
Z. M. Jin ◽  
D Dowson
Keyword(s):  
Numerical Solutions ◽  
Elastohydrodynamic Lubrication ◽  
Hip Implants ◽  
Point Contacts ◽  
Hip Joints ◽  
Circular Point ◽  
Metal On Metal ◽  
Artificial Hip Joints

A full numerical analysis of elastohydrodynamic lubrication (EHL) of circular point contacts was carried out in the present study under isoviscous conditions with particular reference to metal-on-metal artificial hip joints, using a modified Newton-Raphson method. It was found to be possible to incorporate directly the physiological conditions, representative of typical metal-on-metal hip implants under in-vivo walking or in-vitro simulator testing, in the present numerical solutions. The predicted minimum and central film thicknesses were compared favourably with those estimated from various formulae available in the literature. In particular, it was shown that both the minimum and the central film thickness expressions derived by Hamrock and Dowson were reasonably accurate for all the conditions considered in the present study.

Effect of surface texturing on the elastohydrodynamic lubrication analysis of metal-on-metal hip implants

2010 ◽  
Vol 43 (10) ◽  
pp. 1851-1860 ◽  
Author(s):  
Leiming Gao ◽  
Peiran Yang ◽  
Ian Dymond ◽  
John Fisher ◽  
Zhongmin Jin
Keyword(s):  
Surface Texturing ◽  
Elastohydrodynamic Lubrication ◽  
Hip Implants ◽  
Metal On Metal ◽  
Effect Of Surface

scholarly journals Application and comparison of numerical methods in the solution of systems of linear equations in space trusses problems

2018 ◽  
Vol 39 (1) ◽  
pp. 49
Author(s):  
Luiz Antonio Farani de Souza ◽  
Rodrigo Dos Santos Veloso Martins ◽  
Juliana Castanon Xavier ◽  
Johannes Hosp Porto
Keyword(s):  
Numerical Methods ◽  
Linear Equations ◽  
Systems Of Linear Equations ◽  
Newton Raphson ◽  
Space Trusses

Uma das aplicações interessantes da engenharia civil é a treliça espacial, um elemento tridimensional, particularmente utilizado como cobertura para estruturas industriais e comerciais, cobrindo grandes áreas abertas com poucos ou nenhum apoio interno. Este artigo tem como objetivo comparar diferentes métodos numéricos implementados computacionalmente para a solução do sistema de equações lineares gerado da iteração de Newton-Raphson no processo incremental. A solução numérica de tais sistemas lineares écomputacionalmente onerosa, portanto é do nosso interesse determinar quais métodos numéricos melhor se adéquam ao problema. Para comparar o custo computacional dos algoritmos, um estudo da complexidade é realizado. Simulações numéricas com o programa Matlab são feitas de problemas de treliças espaciais com comportamento não linear geométrico. O sistema de equações não lineares é solucionado com o método de Newton-Raphson Padrão associado a técnica de continuação Comprimento de Arco Linear. As estruturassão discretizadas por meio do método dos Elementos Finitos Posicional, cujas variáveis fundamentais são as posições nodais do elemento finito. Para o tempo de processamento, os resultados numéricos indicam um melhor desempenho dos métodos iterativos em comparação com métodos diretos, especialmente para problemas de ordem maior, que são comumente os mais encontrados na área estrutural.

US regulator seeks advice on health risks of metal on metal hip implants

BMJ ◽  
2012 ◽  
Vol 344 (mar30 2) ◽  
pp. e2460-e2460
Author(s):  
D. Cohen
Keyword(s):  
Health Risks ◽  
Hip Implants ◽  
Metal On Metal

Wear and Lubrication of Metal-on-Metal Hip Implants

1999 ◽  
Vol 369 ◽  
pp. 10-24 ◽  
Author(s):  
Frank W. Chan ◽  
J. Dennis Bobyn ◽  
John B. Medley ◽  
Jan J. Krygier ◽  
Michael Tanzer
Keyword(s):  
Hip Implants ◽  
Metal On Metal
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