Effect of microseparation on contact mechanics in ceramic-on-ceramic hip joint replacements

2002 ◽  
Vol 216 (6) ◽  
pp. 403-408 ◽  
Author(s):  
M M Mak ◽  
A A Besong ◽  
Z M Jin ◽  
J Fisher
Keyword(s):  
Femoral Head ◽  
Contact Mechanics ◽  
Contact Pressure ◽  
Contact Area ◽  
Three Dimensional ◽  
Contact Stresses ◽  
Radial Clearance ◽  
Acetabular Cup ◽  
Edge Contact ◽  
Ceramic On Ceramic

The contact mechanics in ceramic-on-ceramic hip implants are investigated in this study under the microseparation condition where the edge contact occurs between the superolateral rim of the acetabular cup and the femoral head. A three-dimensional finite element model is developed to examine the effect of the microseparation distance between the femoral head and the acetabular cup on the contact area and contact stresses between the bearing surfaces. It is shown that microseparation leads to edge contact and elevated contact stresses, and these are mainly dependent on the magnitude of separation, the radial clearance between the femoral head and the acetabular cup, and the cup inclination angle. For a small microseparation distance (less than the diametrical clearance), the contact occurs within the acetabular cup, and consequently an excellent agreement of the predicted contact pressure distribution is obtained between the present three-dimensional anatomical model and a simple two-dimensional axisymmetric model adopted in a previous study [5]. However, as microsegregation is increased further, edge contact between the superolateral rim and the femoral head occurs. Consequently, the predicted contact pressure is significantly increased. The corresponding contact area resembles closely the stripe wear pattern observed on both clinically retrieved and simulator-tested ceramic femoral heads [8, 9, 11]. Furthermore, introducing a fillet radius of 2.5 mm at the mouth of the acetabular cup is shown to reduce the contact stress due to edge contact, but only under relatively large microseparation distances.

Analysis of contact mechanics in ceramic-on-ceramic hip joint replacements

2002 ◽  
Vol 216 (4) ◽  
pp. 231-236 ◽  
Author(s):  
M M Mak ◽  
Z M Jin
Keyword(s):  
Femoral Head ◽  
Contact Mechanics ◽  
Contact Pressure ◽  
Contact Area ◽  
Design Parameters ◽  
Radial Clearance ◽  
Hip Implants ◽  
Acetabular Cup ◽  
Ceramic Insert ◽  
Ceramic On Ceramic

The contact mechanics in ceramic-on-ceramic hip implants has been analysed in this study using the finite element method. Only the ideal conditions where the contact occurs within the acetabular cup were considered. It has been shown that the contact pressure distribution and the contact area at the main articulating bearing surfaces depend largely on design parameters such as the radial clearance between the femoral head and the acetabular cup, as well as the thickness of the ceramic insert. For the ceramic-on-ceramic hip implants used in clinics today, with a minimum 5-mm-thick ceramic insert, it has been shown that the radius of the contact area between the femoral head and the acetabular cup is relatively small compared with that of the femoral head and the ceramic insert thickness. Consequently, Hertz contact theory can be used to estimate the contact parameters such as the maximum contact pressure and the contact area.

Comparison of Contact Mechanics between a Total Hip Replacement and a Hip Resurfacing with a Metal-On-Metal Articulation

2005 ◽  
Vol 219 (7) ◽  
pp. 727-732 ◽  
Author(s):  
F Liu ◽  
I. J. Udofia ◽  
Z. M. Jin ◽  
F Hirt ◽  
C Rieker ◽  
...  
Keyword(s):  
Contact Mechanics ◽  
Contact Pressure ◽  
Total Hip Replacement ◽  
Contact Area ◽  
Hip Replacement ◽  
Clinical Success ◽  
Three Dimensional ◽  
Hip Resurfacing ◽  
Total Hip ◽  
Metal On Metal

The finite element method was employed in this study to compare the contact mechanics at the bearing surfaces between a metal-on-metal hip resurfacing prosthesis and a total hip replacement with a similar bearing combination. The hip resurfacing prosthesis was implanted and modelled in a full three-dimensional pelvic and femoral bone. A significant reduction in the predicted contact pressure by over 53 per cent as well as a corresponding increase in the contact area by approximately 220 per cent was found in the hip resurfacing prosthesis, in comparison to the total hip replacement. The reduced contact pressure and increased contact area in the hip resurfacing system were due to the combination of the larger bearing size and increased elasticity from the metallic cup and the underlying bone support. The hip resurfacing prosthesis may therefore offer a significant improvement in the tribology at the metallic bearing surfaces, thus offering a potential advantage in terms of long-term clinical success over current total hip replacements with reported survivorships over 20 years.

Thermomechanical Coupling of a Hyper-viscoelastic Truck Tire and a Pavement Layer and its Impact on Three-dimensional Contact Stresses

2021 ◽  
pp. 036119812110171
Author(s):  
Angeli Jayme ◽  
Imad L. Al-Qadi
Keyword(s):  
Contact Stress ◽  
Contact Area ◽  
Three Dimensional ◽  
Interaction Model ◽  
Rolling Resistance ◽  
Contact Stresses ◽  
Thermomechanical Coupling ◽  
Temperature Profiles ◽  
Near Surface ◽  
Truck Tire

A thermomechanical coupling between a hyper-viscoelastic tire and a representative pavement layer was conducted to assess the effect of various temperature profiles on the mechanical behavior of a rolling truck tire. The two deformable bodies, namely the tire and pavement layer, were subjected to steady-state-uniform and non-uniform temperature profiles to identify the significance of considering temperature as a variable in contact-stress prediction. A myriad of ambient, internal air, and pavement-surface conditions were simulated, along with combinations of applied tire load, tire-inflation pressure, and traveling speed. Analogous to winter, the low temperature profiles induced a smaller tire-pavement contact area that resulted in stress localization. On the other hand, under high temperature conditions during the summer, higher tire deformation resulted in lower contact-stress magnitudes owing to an increase in the tire-pavement contact area. In both conditions, vertical and longitudinal contact stresses are impacted, while transverse contact stresses are relatively less affected. This behavior, however, may change under a non-free-rolling condition, such as braking, accelerating, and cornering. By incorporating temperature into the tire-pavement interaction model, changes in the magnitude and distribution of the three-dimensional contact stresses were manifested. This would have a direct implication on the rolling resistance and near-surface behavior of flexible pavements.

Dynamic contact stress and frictional heat analysis of femoral head-on-acetabular cup interface based on calculation and simulation methods

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Xingxing Fang ◽  
Dahan Li ◽  
Yucheng Xin ◽  
Songquan Wang ◽  
Yongbo Guo ◽  
...  
Keyword(s):  
Finite Element ◽  
Femoral Head ◽  
Contact Stress ◽  
Contact Area ◽  
Gait Cycle ◽  
Dynamic Change ◽  
Dynamic Contact ◽  
Frictional Heat ◽  
Acetabular Cup ◽  
Content Type

Purpose The purpose of this paper is to systematically study the dynamic contact stress, frictional heat and temperature field of femoral head-on-acetabular cup contact pairs in a gait cycle. Design/methodology/approach In this paper, four common femoral head-on-acetabular cup contact pairs are used as the research objects, mathematical calculations and finite element simulations are adopted. The contact model of hip joint head and acetabular cup was established by finite element simulation to analyze the stress and temperature distribution of the contact interface. Findings The results show that the contact stress of the head-on-cup interface is inversely proportional to the contact area; high contact stress directly leads to greater frictional heat. However, hip joints with metal-on-polyethylene or ceramic-on-polyethylene paired interfaces have lower frictional heat and show a significant temperature rise in one gait cycle, which may be related to the material properties of the acetabular cup. Originality/value Previous studies about calculating the interface frictional heat always ignore the dynamic change process in the contact load and the contact area. This study considered the dynamic changes of the contact stress and area of the femoral head-on-acetabular cup interface, and four common contact pairs were systematically analyzed.

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.

Super-single tire loadings and their impacts on pavement design

2008 ◽  
Vol 35 (2) ◽  
pp. 119-128 ◽  
Author(s):  
Daehyeon Kim
Keyword(s):  
Contact Stress ◽  
Contact Area ◽  
Three Dimensional ◽  
Contact Stresses ◽  
Structure Design ◽  
Pavement Design ◽  
Inflation Pressure ◽  
Dimensional Finite Element ◽  
Tire Loadings ◽  
Three Dimensional Finite Element

Pavement design and analysis are generally performed based on the load equivalent factor (LEF) obtained from conventional dual tires and assume that the contact stress is equal to the tire inflation pressure. However, heavier tire loadings, such as super-single tires, produce much higher contact stresses than the inflation pressure. This results in larger deformations of subgrades, requiring advanced modeling of subgrades, such as elastic–plastic analysis. Super-single tires also have a different contact area shape from that of conventional tires. To assess the increased contact stresses by super-single tires, realistic contact stress distribution and contact area ratio for super-single tires should be used in the analysis. Three-dimensional finite element analyses of typical flexible pavements were done to evaluate the effects of the increased contact stresses of tire loadings on the subgrades, including load equivalency factors, overlay effect, and subgrade improvement as the behavior of subgrades becomes more important due to the increased contact stresses. Analysis results indicate that the increased contact stresses should be taken into account in the pavement structure design, as well as design of overlay or subgrade improvement. Based on the numerical results, simple design examples are suggested.

scholarly journals Three-dimensional finite analysis of acetabular contact pressure and contact area during normal walking

2017 ◽  
Vol 40 (6) ◽  
pp. 463-469 ◽  
Author(s):  
Guangye Wang ◽  
Wenjun Huang ◽  
Qi Song ◽  
Jinfeng Liang
Keyword(s):  
Contact Pressure ◽  
Contact Area ◽  
Three Dimensional ◽  
Normal Walking

scholarly journals A closed-form formulation for the conformal articulation of metal-on-polyethylene hip prostheses: Contact mechanics and sliding distance

2018 ◽  
Vol 232 (12) ◽  
pp. 1196-1208 ◽  
Author(s):  
Ehsan Askari ◽  
Michael S Andersen
Keyword(s):  
Finite Element ◽  
Closed Form ◽  
Contact Mechanics ◽  
Contact Pressure ◽  
Contact Point ◽  
Contact Stresses ◽  
Computational Time ◽  
Physiological Loading ◽  
Sliding Distance ◽  
Inertia Forces

Using Hertz contact law results in inaccurate outcomes when applied to the soft conformal hip implants. The finite element method also involves huge computational time and power. In addition, the sliding distance computed using the Euler rotation method does not incorporate tribology of bearing surfaces, contact mechanics and inertia forces. This study, therefore, aimed to develop a nonlinear dynamic model based on the multibody dynamic methodology to predict contact pressure and sliding distance of metal-on-polyethylene hip prosthesis, simultaneously, under normal walking condition. A closed-form formulation of the contact stresses distributed over the articulating surfaces was derived based upon the elastic foundation model, which reduced computational time and cost significantly. Three-dimensional physiological loading and motions, inertia forces due to hip motion and energy loss during contact were incorporated to obtain contact properties and sliding distance. Comparing the outcomes with that available in the literature and a finite element analysis allowed for the validation of our approach. Contours of contact stresses and accumulated sliding distances at different instants of the walking gait cycle were investigated and discussed. It was shown that the contact point at each instant was located within the zone with the corresponding highest accumulated sliding distance. In addition, the maximum contact pressure and area took place at the stance phase with a single support. The stress distribution onto the cup surface also conformed to the contact point trajectory and the physiological loading.

Contact mechanics of metal-on-metal hip implants employing a metallic cup with a UHMWPE backing

2003 ◽  
Vol 217 (3) ◽  
pp. 207-213 ◽  
Author(s):  
F Liu ◽  
Z M Jin ◽  
P Grigoris ◽  
F Hirt ◽  
C Rieker
Keyword(s):  
Pressure Distribution ◽  
Contact Mechanics ◽  
Contact Pressure ◽  
Coefficient Of Friction ◽  
Hip Implants ◽  
Cobalt Chromium ◽  
Acetabular Cup ◽  
Metal On Metal ◽  
Interfacial Boundary ◽  
The Coefficient Of Friction

The contact mechanics in metal-on-metal hip implants employing a cobalt chromium acetabular cup with an ultra-high molecular weight polyethylene (UHMWPE) backing were analysed in the present study using the finite element method. A general modelling methodology was developed to examine the effects of the interfacial boundary conditions between the UHMWPE backing and a titanium shell for cementless fixation, the coefficient of friction and the loading angle on the predicted contact pressure distribution at the articulating surfaces. It was found that the contact mechanics at the bearing surfaces were significantly affected by the UHMWPE backing. Consequently, a relatively constant pressure distribution was predicted within the contact conjunction, and the maximum contact pressure occurred towards the edge of the contact. On the other hand, the interfacial boundary condition between the UHMWPE backing and the titanium shell, the coefficient of friction and the loading angle were found to have a negligible effect on the contact mechanics at the bearing surfaces. Overall, the magnitude of the contact pressure was significantly reduced, compared with a similar cup without the UHMWPE backing. The importance of the UHMWPE backing on the tribological performance of metal-on-metal hip implants is discussed.

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