scholarly journals Hydrostatic Pressurization and Depletion of Trapped Lubricant Pool During Creep Contact of a Rippled Indenter Against a Biphasic Articular Cartilage Layer

2003 ◽  
Vol 125 (5) ◽  
pp. 585-593 ◽  
Author(s):  
Michael A. Soltz ◽  
Ines M. Basalo ◽  
Gerard A. Ateshian
Keyword(s):  
Articular Cartilage ◽  
Friction Coefficient ◽  
Soft Tissues ◽  
Squeeze Film ◽  
Cartilage Layer ◽  
Time Period ◽  
Lubricant Flow ◽  
Fluid Load ◽  
Study Support ◽  
Friction Models

This study presents an analysis of the contact of a rippled rigid impermeable indenter against a cartilage layer, which represents a first simulation of the contact of rough cartilage surfaces with lubricant entrapment. Cartilage was modeled with the biphasic theory for hydrated soft tissues, to account for fluid flow into or out of the lubricant pool. The findings of this study demonstrate that under contact creep, the trapped lubricant pool gets depleted within a time period on the order of seconds or minutes as a result of lubricant flow into the articular cartilage. Prior to depletion, hydrostatic fluid load support across the contact interface may be enhanced by the presence of the trapped lubricant pool, depending on the initial geometry of the lubricant pool. According to friction models based on the biphasic nature of the tissue, this enhancement in fluid load support produces a smaller minimum friction coefficient than would otherwise be predicted without a lubricant pool. The results of this study support the hypothesis that trapped lubricant decreases the initial friction coefficient following load application, independently of squeeze-film lubrication effects.

Hydrostatic Pressurization and Depletion of Trapped Lubricant Pool During Creep and Sliding Contact of a Rippled Indenter Against a Biphasic Articular Cartilage Layer

2000 ◽  
Author(s):  
Michael A. Soltz ◽  
Gerard A. Ateshian
Keyword(s):  
Fluid Flow ◽  
Steady State ◽  
Articular Cartilage ◽  
Soft Tissues ◽  
Sliding Contact ◽  
Contact Interface ◽  
Cartilage Layer ◽  
Time Period ◽  
Lubricant Flow ◽  
Lubrication Models

Abstract This study presents an analysis of the contact of a rippled rigid impermeable indenter against a cartilage layer, which represents a first simulation of the contact of rough cartilage surfaces with lubricant entrapment. Cartilage was modeled with the biphasic theory for hydrated soft tissues, to account for fluid flow into or out of the lubricant pool. The findings of this study demonstrate that under contact creep, the trapped lubricant pool gets depleted within a time period on the order of seconds as a result of lubricant flow into the articular cartilage, while for steady state sliding contact a lubricant pool cannot be sustained. These results suggest that the classical cartilage lubrication models of weeping and boosted lubrication may have to be revised. More recent mixture-based models described in the literature are able to predict the frictional response of articular cartilage without necessarily assuming or requiring entrapment of lubricant pools at the articular contact interface.

Lubricant Effects on Articular Cartilage Sliding Biomechanics Under Physiological Fluid Load Support

2021 ◽  
Vol 69 (2) ◽  
Author(s):  
Margot S. Farnham ◽  
Kyla F. Ortved ◽  
Jeffrey S. Horner ◽  
Norman J. Wagner ◽  
David L. Burris ◽  
...  
Keyword(s):  
Articular Cartilage ◽  
Fluid Load ◽  
Physiological Fluid

A Comparison of Two Microslip Contact Models for Studying the Mechanics of Underplatform Dampers

2018 ◽  
Author(s):  
Chao Xu ◽  
Dongwu Li ◽  
Muzio M. Gola ◽  
Chiara Gastaldi
Keyword(s):  
Friction Coefficient ◽  
Friction Model ◽  
Tangential Displacement ◽  
Tangential Stiffness ◽  
Contact Loads ◽  
Contact Kinematics ◽  
Contact Models ◽  
Friction Models ◽  
Microslip Friction ◽  
Contact Parameters

In turbine blade systems, under-platform dampers are widely used to attenuate excessive resonant vibrations. Subjected to vibration excitation, the components with frictionally constrained interfaces can involve very complex contact kinematics induced by tangential and normal relative motions. To effectively calculate the dynamics of a blade-damper system, contact models which can accurately reproduce the interface normal and tangential motions are required. The large majority of works have been developed using macroslip friction models to model the friction damping at the contact interface. However, for those cases with small tangential displacement where high normal loads are applied, macroslip models are not enough to give accurate results. In this paper two recently published microslip models are compared, between them and against the simple macroslip spring-slider model. The aim is to find to which extent these models can accurately predict damper mechanics. One model is the so called GG array, where an array of macroslip elements is used. Each macroslip element of the GG array is assigned its own contact parameters and for each of them four parameters are needed: normal stiffness, tangential stiffness, normal gap and friction coefficient. The other one is a novel continuous microslip friction model. The model is based on a modification of the original classic IWAN model to couple normal and tangential contact loads. Like the GG array the model needs normal and tangential stiffness, and friction coefficient. Unlike the GG array the model is continuous and, instead of the normal gap required by the GG array, the Modified IWAN model needs a preload value. The two models are here applied to the study of the mechanics of a laboratory under-platform damper test rig. The results from the two models are compared and allow their difference, both for damper mechanics and for the complex-spring coefficients, to be assessed.

Evaluation of Articular Cartilage Injury Using Computed Tomography With Axial Traction in the Ankle Joint

2018 ◽  
Vol 39 (9) ◽  
pp. 1120-1127 ◽  
Author(s):  
Tomoyuki Nakasa ◽  
Yasunari Ikuta ◽  
Mikiya Sawa ◽  
Masahiro Yoshikawa ◽  
Yusuke Tsuyuguchi ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Articular Cartilage ◽  
Sensitivity And Specificity ◽  
Subchondral Bone ◽  
Ct Images ◽  
Cartilage Layer ◽  
Arthroscopic Findings ◽  
Cartilage Injuries ◽  
Axial Traction ◽  
Articular Cartilage Injuries

Background: Although chondral or osteochondral injuries are usually assessed by magnetic resonance imaging, its accuracy can be low, presumably related to the relatively thin cartilage layer and the close apposition of the cartilage of the talus and tibial plafond. We hypothesized that axial traction could provide a contrast between the articular cartilage and joint cavity, and it enabled the simultaneous evaluation of cartilage and subchondral bone. The purpose of this study was to assess the feasibility of using computed tomography (CT) imaging with axial traction for the diagnosis of articular cartilage injuries. Methods: Chondral lesions in 18 ankles were evaluated by CT with axial traction using a tensioning device and ankle strap for enlargement of the joint space of the ankle. CT was done in 3-mm slices and programmed for gray scale, and then CT images were allocated colors to make it easier to evaluate the cartilage layer. The International Cartilage Repair Society (ICRS) grades on CT were compared with those on arthroscopic findings. Results: The respective sensitivity and specificity of CT imaging with traction using ICRS grading were 74.4%, and 96.3%. The level of agreement of the ICRS grading between CT images and arthroscopic findings was moderate (kappa coefficient, 0.547). Adding axial traction to CT increased the delineation of the cartilage surface, including chondral thinning, chondral defect, and cartilage separation. Conclusions: CT with axial traction produced acceptable levels of sensitivity and specificity for the evaluation of articular cartilage injuries, in addition to the assessment of subchondral bone. Level of Evidence: Level III, comparative case series.

Comparison of biphasic material properties of equine articular cartilage estimated from stress relaxation and creep indentation tests

2021 ◽  
Vol 7 (2) ◽  
pp. 363-366
Author(s):  
Thomas Reuter ◽  
Christof Hurschler
Keyword(s):  
Articular Cartilage ◽  
Stress Relaxation ◽  
Material Properties ◽  
Soft Tissues ◽  
Sensitivity Analyses ◽  
Creep Model ◽  
Fe Model ◽  
Relaxation Model ◽  
Marquardt Algorithm ◽  
Indentation Tests

Abstract Mechanical parameters of hard and soft tissues are explicit markers for quantitative tissue characterization. In this study, we present a comparison of biphasic material properties of equine articular cartilage estimated from stress relaxation (ε = 6 %, t = 1000 s) and creep indentation tests (F = 0.1 N, t = 1000 s). A biphasic 3D-FE-based method is used to determine the biomechanical properties of equine articular cartilage. The FE-model computation was optimized by exploiting the axial symmetry and mesh resolution. Parameter identification was executed with the Levenberg- Marquardt-algorithm. Additionally, sensitivity analyses of the calculated biomechanical parameters were performed. Results show that the Young’s modulus E has the largest influence and the Poisson’s ratio of ν ≤ 0.1 is rather insensitive. The R² of the fit results varies between 0.882 and 0.974 (creep model) and between 0.695 and 0.930 (relaxation model). The averaged parameters E and k determined from the creep model yield higher values in comparison to the relaxation model. The differences can be traced back to the experimental settings and to the biphasic material model.

scholarly journals Wire Mesh Dampers for Semi-Floating Ring Bearings in Automotive Turbochargers: Measurements of Structural Stiffness and Damping Parameters

Energies ◽  
2018 ◽  
Vol 11 (4) ◽  
pp. 812 ◽  
Author(s):  
Keun Ryu ◽  
Howon Yi
Keyword(s):  
Friction Coefficient ◽  
Dry Friction ◽  
Loss Factor ◽  
Static Load ◽  
Wire Mesh ◽  
Squeeze Film ◽  
Dissipated Energy ◽  
Operation Conditions ◽  
In Series ◽  
Oil Films

The current work introduces a new semi-floating ring bearing (SFRB) system developed for improving the rotordynamic and vibration performance of automotive turbochargers (TCs) at extreme operation conditions, such as high temperature, severe external force excitation, and large rotor imbalance. The new bearing design replaces outer oil films, i.e., squeeze film dampers (SFDs), in TC SFRBs with wire mesh dampers (WMDs). This SFRB configuration integrating WMDs aims to implement reliable mechanical components, as an inexpensive and simple alternative to SFDs, with consistent and superior damping capability, as well as predictable forced performance. Since WMDs are in series with the inner oil films of SFRBs, experimentally determined force coefficients of WMDs are of great importance in the design process of TC rotor-bearing systems (RBSs). Presently, the measurements of applied static load and ensuing deflection determine the structural stiffnesses of the WMDs. The WMD damping parameters, including dissipated energy, loss factor, and dry friction coefficient, are estimated from the area of the distinctive local hysteresis loop of the load versus WMD displacement data recorded during consecutive loading-unloading cycles as a function of applied preload with a constant amplitude of motion. The changes in WMD loss factor and dry friction coefficient due to increases in preload are more significant for the WMDs with lower density. The present work shows, to date, the most comprehensive measurements of static load characteristics on the WMDs for application into small automotive TCs. More importantly, the extensive test measurements of WMD deflection versus increasing static loads will aid to anchor predictions of future computation model.

scholarly journals Tribological Rehydration and Its Role on Frictional Behavior of PVA/GO Hydrogels for Cartilage Replacement Under Migrating and Stationary Contact Conditions

2020 ◽  
Vol 69 (1) ◽  
Author(s):  
Yan Shi ◽  
Dangsheng Xiong ◽  
Jianliang Li ◽  
Long Li ◽  
Qibin Liu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Articular Cartilage ◽  
Friction Coefficient ◽  
Creep Resistance ◽  
Frictional Coefficient ◽  
Dynamic Mechanical Properties ◽  
Friction Behavior ◽  
Frictional Behavior ◽  
Fluid Pressurization ◽  
Stationary Contact

AbstractGraphene oxide (GO) was incorporated into polyvinyl alcohol (PVA) hydrogel to improve its mechanical and tribological performances for potential articular cartilage replacement application. The compressive mechanical properties, creep resistance, and dynamic mechanical properties of PVA/GO hydrogels with varied GO content were studied. The frictional behavior of PVA/GO hydrogels under stationary and migrating contact configurations during reciprocal and unidirectional sliding movements were investigated. The effects of load, sliding speed, diameter of counterface, and counterface materials on the frictional coefficient of PVA/GO hydrogels were discussed. PVA/0.10wt%GO hydrogel show higher compressive modulus and creep resistance, but moderate friction coefficient. The friction coefficient of PVA/GO hydrogel under stationary and migratory contact configurations greatly depends on interstitial fluid pressurization and tribological rehydration. The friction behavior of PVA/GO hydrogels shows load, speed, and counterface diameter dependence similar to those observed in natural articular cartilage. A low friction coefficient (~ 0.03) was obtained from PVA/0.10wt%GO hydrogel natural cartilage counter pair. Graphical Abstract

Regulation of the friction coefficient of articular cartilage by TGF-β1 and IL-1β

2009 ◽  
Vol 27 (2) ◽  
pp. 249-256 ◽  
Author(s):  
Grayson DuRaine ◽  
Corey P. Neu ◽  
Stephanie M.T. Chan ◽  
Kyriakos Komvopoulos ◽  
Ronald K. June ◽  
...  
Keyword(s):  
Articular Cartilage ◽  
Friction Coefficient ◽  
Tgf Β1

scholarly journals Articular Cartilage Wear Characterization With a Particle Sizing and Counting Analyzer

2012 ◽  
Author(s):  
Sevan R. Oungoulian ◽  
Orian Bortz ◽  
Kristin E. Hehir ◽  
Kaicen Zhu ◽  
Clark T. Hung ◽  
...  
Keyword(s):  
Articular Cartilage ◽  
Friction Coefficient ◽  
Wear Debris ◽  
Polyethylene Wear ◽  
Quantitative Measurements ◽  
Diarthrodial Joints ◽  
Cartilage Wear ◽  
Tangential Forces ◽  
Fluid Pressurization

The primary function of articular cartilage is to serve as the bearing material in diarthrodial joints, transmitting loads while minimizing friction and wear. The friction coefficient of cartilage has been characterized extensively in the literature, using standard measurements of normal and tangential forces acting across a sliding interface [1]. However, quantitative measurements of cartilage wear have proven to be more challenging, with only a few studies having reported such measurements. The primary quantitative approaches proposed to date include biochemical assaying of cartilage and test solutions [2], and characterization of changing articular layer thickness [3] and surface roughness [4]. One study examining polyethylene wear debris in hip arthroplasty reported the use of an automated particle analyzer [5]. The aim of this study was to test the hypothesis that latest-generation particle analyzers are capable of detecting cartilage wear debris generated during in vitro loading experiments that last 24 h or less, by producing measurable content significantly above background noise levels. The longer-term objective of our studies is to test the hypothesis that elevated interstitial fluid pressurization, which is known to reduce the friction coefficient of cartilage [6], also reduces cartilage wear.

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