Wear Simulation of Metal-on-Metal Hip Replacements With Frictional Contact

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
Lorenza Mattei ◽  
Francesca Di Puccio
Keyword(s):  
Finite Element ◽  
Pressure Distribution ◽  
Frictional Contact ◽  
Contact Point ◽  
Wear Volume ◽  
Contact Pressure Distribution ◽  
Total Wear ◽  
Metal On Metal ◽  
Hip Replacements ◽  
Wear Maps

Preclinical wear evaluation is extremely important in hip replacements, wear being one of the main causes of failure. Experimental tests are attractive but highly cost demanding; thus predictive models have been proposed in the literature, mainly based on finite element simulations. In such simulations, the effect of friction is usually disregarded, as it is considered not to affect the contact pressure distribution. However, a frictional contact could also result in a shift of the location of the nominal contact area, which can thus modify the wear maps. The aim of this study is to investigate this effect in wear prediction for metal-on-metal implants. Wear assessment was based on a purpose-developed mathematical model, extension of a previous one proposed by the same authors for metal-on-plastic implants. The innovative aspect of the present study consists in the implementation of a modified location of the nominal contact point due to friction, which takes advantage of the analytical formulation of the wear model. Simulations were carried out aimed at comparing total and resurfacing hip replacements under several gait conditions. The results highlighted that the adoption of a frictional contact yields lower linear wear rates and wider worn areas, while for the adopted friction coefficient (f=0.2), the total wear volume remains almost unchanged. The comparison between total and resurfacing replacements showed higher scaled wear volumes (wear volume divided by wear factor) for the latter, in agreement with the literature. The effect of the boundary conditions (in vivo versus in vitro) was also investigated remarking their influence on implant wear and the need to apply more physiological-like conditions in hip simulators. In conclusion although friction is usually neglected in numerical wear predictions, as it does not affect markedly the contact pressure distribution, its effect in the location of the theoretical contact point was observed to influence wear maps. This achievement could be useful for increasing the correlation between numerical and experimental simulations, usually based on the total wear volume. In order to improve the model reliability, future studies will be devoted to implement the geometry update by combining the present model to finite element analyses. On the other hand, further experimental investigations are required to get out from the wide dispersion of wear factors reported in the literature.

Analysis of Contact Pressure Distribution on 3-Bolt Self-Energized Connector Seals

2009 ◽  
Author(s):  
Rajeev Madazhy ◽  
Sheril Mathews ◽  
Erik Howard
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Pressure Distribution ◽  
Contact Pressure ◽  
Maximum Pressure ◽  
Operating Pressure ◽  
Seal Ring ◽  
Contact Pressure Distribution ◽  
Element Analysis ◽  
Novel Design

A novel design using 3 bolts for a self-energized seal connector is proposed for quick assembly applications. Contact pressure distribution on the surface of the seal ring during initial bolt-up and subsequent operating pressure is analyzed for 3″ and 10″ connectors using Finite Element Analysis. FEA is performed on a 3″ and 10″ ANSI RF flange assembly and contact pressure distribution on the RF gasket is compared with the tapered seal ring assemblies. Hydrostatic tests are carried out for the tapered seal and ANSI bolted connectors to evaluate maximum pressure at which leak occurs for both size assemblies.

A Method for Characterizing Running-In of Sliding Contacts

2016 ◽  
Vol 681 ◽  
pp. 228-233
Author(s):  
R. Ismail ◽  
M. Tauviqirrahman ◽  
J. Jamari ◽  
D.J. Schipper
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Pressure Distribution ◽  
Sliding Contact ◽  
Wear Depth ◽  
Contact Pressure Distribution ◽  
Sliding Contacts ◽  
Element Analysis ◽  
Element Simulation ◽  
Proposed Model

Although in terms of conservation wear is undesirable, however, running-in wear is encouraged rather than avoided. Running-in is rather complex and most of the studies related to the change in micro-geometry have been conducted statistically. The purpose of this study was to characterize the running-in of sliding contacts using finite element analysis based on measured micro-geometries. The developed model combines the finite element simulation, Archard’s wear equation and updated geometry to calculate the contact pressure distribution and wear depth. Results show that the proposed model is able to predict the running-in phase of sliding contact system.

A Finite Element Tire Model

1983 ◽  
Vol 11 (1) ◽  
pp. 50-63 ◽  
Author(s):  
J. T. Tielking
Keyword(s):  
Finite Element ◽  
Pressure Distribution ◽  
Contact Pressure ◽  
Shell Of Revolution ◽  
Comprehensive Model ◽  
Tire Model ◽  
Contact Pressure Distribution ◽  
Design Variables ◽  
Nonlinear Shell ◽  
Basic Characteristics

Abstract A finite element tire model, based on nonlinear shell of revolution elements, has been developed to investigate tire-pavement interaction. The basic characteristics of this relatively comprehensive model are reviewed here, with attention focused on its ability to calculate the effect of tire design variables on tire performance data. A four-ply bias tire is used to show the ability of the model to predict the different effects that nylon and polyester cords have on tire deformation, contact pressure distribution, and traction.

A Useful Solution for Estimating Contact Pressure Between a Plate and Foundation

1999 ◽  
Vol 122 (4) ◽  
pp. 781-789
Author(s):  
L. B. Shulkin ◽  
D. A. Mendelsohn ◽  
G. L. Kinzel ◽  
T. Altan
Keyword(s):  
Finite Element ◽  
Pressure Distribution ◽  
Contact Pressure ◽  
Finite Thickness ◽  
Applied Pressure ◽  
Three Dimensional ◽  
Sensitivity Study ◽  
Winkler Foundation ◽  
Contact Pressure Distribution ◽  
Design Variables

Many manufacturing situations involve a finite thickness plate or layer of material which is pressed against a much thicker foundation of the same or different material. One key example is a blank holder (plate) pressed against a die (foundation) in a sheet metal forming operation. In designing such a plate/foundation system the design objective often involves the contact stress distribution between the plate and foundation and the design variables are typically the thickness and modulus of the plate, the stiffness of the foundation and the applied pressure distribution on the noncontacting side of the plate. In general the problem relating the variables to the contact pressure distribution is three-dimensional and requires a complex finite element or boundary element solution. However, if the applied pressure distribution consists of sufficiently localized patches, which is often the case in applications, then an approximate 3D solution can be constructed by superposition. Specifically, the paper provides a convenient calculation procedure for the contact pressure due to a single circular patch of applied pressure on an infinite, isotropic, elastic layer which rests on a Winkler foundation. The procedure is validated by using known analytical solutions and the finite element method (FEM). Next a sensitivity study is presented for ascertaining the validity of the solution’s use in constructing solutions to practical problems involving multiple patches of loading. This is accomplished through a parametric study of the effects of loading radius, layer thickness, layer elastic properties, foundation stiffness and the form of the applied pressure distribution on the magnitude and extent of the contact pressure distribution. Finally, a procedure for determining an appropriate Winkler stiffness parameter for a foundation is presented. [S1087-1357(00)00603-1]

Finite element analysis of the ovine hip: Development, results and comparison with the human hip

2012 ◽  
Vol 25 (04) ◽  
pp. 301-306 ◽  
Author(s):  
J. Jalali ◽  
F. Schmidutz ◽  
C. Schröder ◽  
M. Woiczinski ◽  
J. Maierl ◽  
...  
Keyword(s):  
Finite Element ◽  
Pressure Distribution ◽  
Contact Pressure ◽  
Pelvic Bone ◽  
Acetabular Cartilage ◽  
Contact Pressure Distribution ◽  
Element Analysis ◽  
Average Value ◽  
Femoral Cartilage ◽  
Acetabular Side

SummaryObjectives: The ovine hip is often used as an experimental research model to simulate the human hip. However, little is known about the contact pressures on the femoral and acetabular cartilage in the ovine hip, and if those are representative for the human hip.Methods: A model of the ovine hip, including the pelvis, femur, acetabular cartilage, femoral cartilage and ligamentum transversum, was built using computed tomography and microcomputed tomography. Using the finite element method, the peak forces were analysed during simulated walking.Results: The evaluation revealed that the contact pressure distribution on the femoral cartilage is horseshoe-shaped and reaches a maximum value of approximately 6 MPa. The maximum contact pressure is located on the dorsal acetabular side and is predominantly aligned in the cranial-to-caudal direction. The surface stresses acting on the pelvic bone reach an average value of approximately 2 MPa.Conclusions: The contact pressure distribution, magnitude, and the mean surface stress in the ovine hip are similar to those described in the current literature for the human hip. This suggests that in terms of load distribution, the ovine hip is well suited for the preclinical testing of medical devices designed for the human hip.

Analysis of elastohydrodynamic lubrication in a novel metal-on-metal hip joint replacement

2002 ◽  
Vol 216 (3) ◽  
pp. 185-193 ◽  
Author(s):  
M Jagatia ◽  
Z M Jin
Keyword(s):  
Finite Element ◽  
Film Thickness ◽  
Pressure Distribution ◽  
Contact Pressure ◽  
Elastohydrodynamic Lubrication ◽  
Metal On Metal ◽  
Minimum Film Thickness ◽  
Acetabular Components ◽  
Cobalt Chrome Alloy ◽  
Cobalt Chrome

Elastohydrodynamic lubrication (EHL) analysis was carried out in this study for a novel metal-on-metal hip prosthesis, which consists of a cobalt-chrome alloy femoral head articulating against a cobalt-chrome alloy acetabular insert connected to a titanium fixation shell through a taper. Finite element models were developed to investigate the effect of the pelvic bone and the load on the predicted contact pressure distribution between the two bearing surfaces under dry conditions. The finite element method was used to develop elasticity models for both the femoral and the acetabular components; it was found that the elastic deformation of the acetabular insert was mainly dependent on the load, rather than the detailed pressure distribution. A modified solution methodology was accordingly developed to couple the elasticity models for both the femoral and the acetabular surfaces with the Reynolds equation and to solve these numerically by the finite difference method. It was found that a load increase from 500 to 2500 N had a negligible effect on the predicted maximum contact pressure and the minimum film thickness, due to the relatively flexible and accommodating structure of the acetabular insert. Furthermore, the predicted minimum film thickness was shown to be significantly greater than the simple estimation based on the assumption of semi-infinite solids (mono-block design) using the Hamrock and Dowson formula. The effects of the viscosity of the lubricant and the radial clearance between the femoral and the acetabular components on the predicted lubricating film thickness were investigated under both in vitro simulator testing and in vivo walking conditions.

Analysis of contact mechanics in McKee-Farrar metal-on-metal hip implants

2003 ◽  
Vol 217 (5) ◽  
pp. 333-340 ◽  
Author(s):  
A Yew ◽  
M Jagatia ◽  
H Ensaff ◽  
Z M Jin
Keyword(s):  
Pressure Distribution ◽  
Contact Pressure ◽  
Contact Region ◽  
Radial Clearance ◽  
Geometrical Parameters ◽  
Contact Pressure Distribution ◽  
Acetabular Cup ◽  
Metal On Metal ◽  
Half Angle ◽  
Maximum Contact

Contact mechanics analysis for a typical McKee-Farrar metal-on-metal hip implant was carried out in this study. The finite element method was used to predict the contact area and the contact pressure distribution at the bearing surfaces. The study investigated the effects of the cement and underlying bone, the geometrical parameters such as the radial clearance between the acetabular cup and the femoral head, and the acetabular cup thickness, as well as other geometrical features on the acetabular cup such as lip and studs. For all the cases considered, the predicted contact pressure distribution was found to be significantly different from that based upon the classical Hertz contact theory, with the maximum value being away from the centre of the contact region. The lip on the cup was found to have a negligible effect on the predicted contact pressure distribution. The presence of the studs on the outside of the cup caused a significant increase in the local contact pressure distribution, and a slight decrease in the contact region. Reasonably good agreement of the predicted contact pressure distribution was found between a three-dimensional anatomical model and a simple two-dimensional axisymmetric model. The interfacial boundary condition between the acetabular cup and the underlying cement, modelled as perfectly fixed or perfectly unbonded, had a negligible effect on the predicted contact parameters. For a given radial clearance of 0.079 mm, the decrease in the thickness of the acetabular cup from 4.5 to 1.5 mm resulted in an increase in the contact half angle from 15° to 26°, and a decrease in the maximum contact pressure from 55 to 20 MPa. For a given acetabular cup thickness of 1.5 mm, a decrease in the radial clearance from 0.158 to 0.0395mm led to an increase in the contact half-angle from 20° to 30°, and a decrease in the maximum contact pressure from 30 to 10 MPa. For zero clearance, although the contact pressure was significantly reduced over most of the contact area, the whole acetabular cup came into contact with the femoral head, leading to stress concentration at the edge of the cup. Design optimization of the geometrical parameters, in terms of the acetabular cup thickness and the radial clearance, is important, not only to minimize the contact stress at the bearing surfaces, but also to avoid equatorial and edge contact.

Sign in / Sign up

Export Citation Format

Share Document