scholarly journals MULTILEVEL NUMERICAL MODEL OF HIP JOINT ACCOUNTING FOR FRICTION IN THE HIP RESURFACING ENDOPROSTHESIS

2019 ◽  
Vol 17 (1) ◽  
pp. 29 ◽  
Author(s):  
Galina M. Eremina ◽  
Alexey Yu. Smolin
Keyword(s):  
Numerical Model ◽  
Multilevel Modeling ◽  
Operation Time ◽  
Scratch Test ◽  
Hip Resurfacing ◽  
Knee Joints ◽  
Macroscopic Model ◽  
Tribological Characteristics ◽  
Cellular Automaton Method ◽  
Moving Parts

Friction between the moving parts of the endoprosthesis has a significant impact on the endoprosthesis operation time. Primarily, it concerns the endoprosthesis of hip and knee joints. To improve the tribological characteristics of the metal endoprosthesis, hardening nanostructured coatings are used. Usually, titanium and titanium alloys are used as metal, and titanium nitride is used as a coating. Herein, we propose an approach to multilevel modeling of the system “bone-endoprosthesis” which is based on the movable cellular automaton method and accounts for friction between the moving parts of the hip resurfacing endoprosthesis. We validated the models of the friction system materials using the instrumented scratch test simulation. Then, we simulated friction at the mesolevel, explicitly considering roughness of the coating. The results obtained at the mesolevel were used as tribological characteristics of the coating in the macroscopic model of the hip resurfacing endoprosthesis.

Experimental Validation of a Dynamic Numerical Model for Timing Belt Drives Behavior Simulation

2000 ◽  
Author(s):  
Lionel Manin ◽  
Daniel Play ◽  
Patrick Soleilhac
Keyword(s):  
Numerical Model ◽  
Dynamic Behavior ◽  
Operation Time ◽  
Transmission Error ◽  
Numerical Results ◽  
Experimental Results ◽  
Medium Size ◽  
Behavior Simulation ◽  
Dynamic Transmission Error ◽  
Timing Belt

Abstract The behavior of timing belts used in automotive applications have to be defined and predicted at the preliminary design phases. Numerical simulations replace progressively experimental determinations that are time and money consuming. The object of the work was to qualify from experimental results a timing belt drive numerical model. The model simulates the dynamic behavior versus time of any kind of tooth belt power transmissions. The model architecture, originalities and capabilities have been already presented, and the purpose is now to compare in details numerical and experimental results. The experimental qualification has been carried out on a laboratory test bench with a medium size engine valve controlled distribution made of 3 pulleys and a tensioner. Tensions, camshaft torque, pulleys speeds and angular acylisms, dynamic transmission error between camshaft and crankshaft pulleys have been measured. Numerous tests have been made for different running conditions by changing : speed, angular acyclism, camshaft torque, setting tension. Several phenomena and influence of parameters have been identified, as the pulley eccentricity effect on camshaft torque, span tensions, and transmission error. Part of the experimental results are used as entries of the model : camshaft torque, crankshaft instantaneous speed, transmission error due to pulley eccentricities. Further, comparisons with the numerical results were made. Experimental and numerical results of tension, angular acyclism, dynamic transmission error, versus operation time are compared for the different tests performed. The agreement is good and shows that the model developed allows to simulate dynamic behavior of timing belt with high degree of confidence.

scholarly journals Mathematical and numerical model for nonlinear viscoplasticity

2011 ◽  
Vol 369 (1947) ◽  
pp. 2864-2880 ◽  
Author(s):  
N. Favrie ◽  
S. Gavrilyuk
Keyword(s):  
Numerical Model ◽  
Specific Energy ◽  
Macroscopic Model ◽  
Material Behaviour ◽  
Plastic Deformations ◽  
Numerical Examples ◽  
Von Mises ◽  
Physical Phenomena ◽  
Deviatoric Part ◽  
Special Case

A macroscopic model describing elastic–plastic solids is derived in a special case of the internal specific energy taken in separable form: it is the sum of a hydrodynamic part depending only on the density and entropy, and a shear part depending on other invariants of the Finger tensor. In particular, the relaxation terms are constructed compatible with the von Mises yield criteria. In addition, Maxwell-type material behaviour is shown up: the deviatoric part of the stress tensor decays during plastic deformations. Numerical examples show the ability of this model to deal with real physical phenomena.

scholarly journals Influence of Changes in the Shape of the Anode Channel in Polymer Electrolyte Fuel Cell on the Loss of Its Service Life

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7338
Author(s):  
Daniel Sławiński ◽  
Michał Soszko ◽  
Wojciech Tokarz ◽  
Sebastian Bykuć
Keyword(s):  
Fuel Cell ◽  
Numerical Model ◽  
Current Density ◽  
Produced Water ◽  
Mechanical Load ◽  
Operation Time ◽  
Polymer Electrolyte Fuel Cell ◽  
Test Results ◽  
Safe Operation ◽  
Fuel Cell Operation

The fuel cell operation is associated with significant current density and durability problems, among other anode collectors. We used a numerical model based on flows with chemical reactions in a porous medium to solve these problems. We tested four variants of the anode channels. In the shape of the anode channel, we introduced changes to improve the current density. We also examined the influence of the channel shape on the stress field and rheological processes in the casing material. We verified the numerical model on the experimental data. Furthermore, we corrected the amount of the hydrogen stream and the produced water in the whole range of the cell’s operation. The test results show that it is possible to increase the current density in all operating fields of the fuel cell while maintaining a low mechanical load on graphite elements and their safe operation time.

scholarly journals Modelling of the Dendritic Crystallization by the Cellular Automaton Method

2016 ◽  
Vol 16 (1) ◽  
pp. 99-106 ◽  
Author(s):  
A. Zyska ◽  
Z. Konopka ◽  
M. Łągiewka ◽  
M. Nadolski
Keyword(s):  
Numerical Model ◽  
Cellular Automaton ◽  
Binary Alloy ◽  
Solid Phase ◽  
Dendritic Structure ◽  
Concentration Field ◽  
Surface Phenomena ◽  
Actual Structure ◽  
Dendritic Crystal ◽  
Cellular Automaton Method

Abstract A numerical model of binary alloy crystallization, based on the cellular automaton technique, is presented. The model allows to follow the crystallization front movement and to generate the images of evolution of the dendritic structures during the solidification of a binary alloy. The mathematic description of the model takes into account the proceeding thermal, diffusive, and surface phenomena. There are presented the results of numerical simulations concerning the multi-dendritic growth of solid phase along with the accompanying changes in the alloying element concentration field during the solidification of Al + 5% wt. Mg alloy. The model structure of the solidified casting was achieved and compared with the actual structure of a die casting. The dendrite interaction was studied with respect to its influence on the generation and growth of the primary and secondary dendrite arms and on the evolution of solute segregation both in the liquid and in the solid state during the crystallization of the examined alloy. The morphology of a single, free-growing dendritic crystal was also modelled. The performed investigations and analyses allowed to state e.g. that the developed numerical model correctly describes the actual evolution of the dendritic structure under the non-equilibrium conditions and provides for obtaining the qualitatively correct results of simulation of the crystallization process.

Power Values and Power Distance Moderate the Relationship Between Workplace Supervisory Power and Job Satisfaction

2020 ◽  
Vol 19 (3) ◽  
pp. 135-141
Author(s):  
Kenneth D. Locke
Keyword(s):  
Job Satisfaction ◽  
Multilevel Modeling ◽  
Power Distance ◽  
European Social Survey ◽  
Social Survey ◽  
The Relationship ◽  
Workplace Power ◽  
Over Time

Abstract. Person–job (or needs–supplies) discrepancy/fit theories posit that job satisfaction depends on work supplying what employees want and thus expect associations between having supervisory power and job satisfaction to be more positive in individuals who value power and in societies that endorse power values and power distance (e.g., respecting/obeying superiors). Using multilevel modeling on 30,683 European Social Survey respondents from 31 countries revealed that overseeing supervisees was positively associated with job satisfaction, and as hypothesized, this association was stronger among individuals with stronger power values and in nations with greater levels of power values or power distance. The results suggest that workplace power can have a meaningful impact on job satisfaction, especially over time in individuals or societies that esteem power.

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