scholarly journals Contribution to the Modelling of the Tribological Surface Transformations

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
G. Antoni
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Phase Transformations ◽  
Structural Changes ◽  
Solid Phase ◽  
Thermomechanical Model ◽  
Element Analysis ◽  
Loaded Area

When solids are subjected to tribological loads, structural changes can occur both at the surface and in depth, immediately below the loaded area; in the case of some materials, especially metals, these changes are known as solid-solid phase transformations or Tribological Surface Transformations (TSTs). A thermomechanical model is presented in the present study in order to describe these TSTs. The ability of the model to take account TSTs is assessed with a 2D finite element analysis.

A Penetration-Based Finite Element Method for Hyperelastic 3D Biphasic Tissues in Contact: Part 1-Derivation of Contact Boundary Conditions

2005 ◽  
Vol 128 (1) ◽  
pp. 124-130 ◽  
Author(s):  
Kerem Ün ◽  
Robert L. Spilker
Keyword(s):  
Finite Element Method ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Boundary Conditions ◽  
Solid Phase ◽  
Contact Boundary ◽  
Element Analysis ◽  
Efficient Manner ◽  
Biphasic Tissues ◽  
Element Method

In this study, we extend the penetration method, previously introduced to simulate contact of linear hydrated tissues in an efficient manner with the finite element method, to problems of nonlinear biphasic tissues in contact. This paper presents the derivation of contact boundary conditions for a biphasic tissue with hyperelastic solid phase using experimental kinematics data. Validation of the method for calculating these boundary conditions is demonstrated using a canonical biphasic contact problem. The method is then demonstrated on a shoulder joint model with contacting humerus and glenoid tissues. In both the canonical and shoulder examples, the resulting boundary conditions are found to satisfy the kinetic continuity requirements of biphasic contact. These boundary conditions represent input to a three-dimensional nonlinear biphasic finite element analysis; details of that finite element analysis will be presented in a manuscript to follow.

scholarly journals Modeling Solid-Phase Microextraction of Volatile Organic Compounds by Porous Coatings Using Finite Element Analysis

2019 ◽  
Author(s):  
Bulat Kenessov ◽  
Miras Derbissalin ◽  
Jacek A. Koziel ◽  
Dmitry S. Kosyakov
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Volatile Organic Compounds ◽  
Mass Transport ◽  
Organic Compounds ◽  
Solid Phase Microextraction ◽  
Solid Phase ◽  
Element Analysis ◽  
Volatile Organic ◽  
Pdms Coating

Experimental optimization of analytical methods based on solid-phase microextraction (SPME) is a complex and labor-intensive process associated with uncertainties. Using theoretical basics of SPME and finite element analysis software for the optimization proved to be an efficient alternative. In this study, an improved finite element analysis-based model for SPME of volatile organic compounds (VOCs) by porous coatings was developed mainly focussing on the mass transport in coatings. Benzene and the Carboxen/polydimethylsiloxane (Car/PDMS) coating were used as the model VOC and a porous SPME coating, respectively. It has been established that in the coating, volumetric fractions of Carboxen, PDMS, and air are 33, 42 and 25%, respectively. It has been proven that Knudsen diffusion in micropores can slow down a mass transport of analytes in the coating. For Car/PDMS coating, mass transport of benzene is mostly characterized by a molecular diffusion, which can be explained by a large fraction of macro- and mesopores. It has been shown that the developed model can be used to model the extraction of VOCs from air and water samples encountered in a typical SPME development method procedure. It was possible to determine system equilibration times and use them to optimize sample volume and Henry’s law constant. The developed model is relatively simple, fast, and can be recommended for optimization of extraction parameters for other analytes and SPME coatings. The diffusivity of analytes in a coating is an important property needed for improved characterization of existing and new SPME polymers and analytical method optimization.

scholarly journals Optimization of Time-Weighted Average Air Sampling by Solid-Phase Microextraction Fibers Using Finite Element Analysis Software

Molecules ◽  
2018 ◽  
Vol 23 (11) ◽  
pp. 2736 ◽  
Author(s):  
Bulat Kenessov ◽  
Jacek Koziel ◽  
Nassiba Baimatova ◽  
Olga Demyanenko ◽  
Miras Derbissalin
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Solid Phase Microextraction ◽  
Solid Phase ◽  
Weighted Average ◽  
Internal Diameter ◽  
Analysis Software ◽  
Element Analysis ◽  
Time Weighted Average

Determination of time-weighted average (TWA) concentrations of volatile organic compounds (VOCs) in air using solid-phase microextraction (SPME) is advantageous over other sampling techniques, but is often characterized by insufficient accuracies, particularly at longer sampling times. Experimental investigation of this issue and disclosing the origin of the problem is problematic and often not practically feasible due to high uncertainties. This research is aimed at developing the model of the TWA extraction process and optimization of TWA air sampling by SPME using finite element analysis software (COMSOL Multiphysics, Burlington, MA, USA). It was established that sampling by porous SPME coatings with high affinity to analytes is affected by slow diffusion of analytes inside the coating, an increase of their concentrations in the air near the fiber tip due to equilibration, and eventual lower sampling rate. The increase of a fiber retraction depth (Z) resulted in better recoveries. Sampling of studied VOCs using 23 ga Carboxen/polydimethylsiloxane (Car/PDMS) assembly at maximum possible Z (40 mm) was proven to provide more accurate results. Alternative sampling configuration based on 78.5 × 0.75 mm internal diameter SPME liner was proven to provide similar accuracy at improved detection limits. Its modification with the decreased internal diameter from the sampling side should provide even better recoveries. The results obtained can be used to develop a more accurate analytical method for determination of TWA concentrations of VOCs in air using SPME. The developed model can be used to simulate sampling of other environments (process gases, water) by retracted SPME fibers.

Effects of Friction on the Unconfined Compressive Response of Articular Cartilage: A Finite Element Analysis

1990 ◽  
Vol 112 (2) ◽  
pp. 138-146 ◽  
Author(s):  
Robert L. Spilker ◽  
Jun-Kyo Suh ◽  
Van C. Mow
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Articular Cartilage ◽  
Soft Tissues ◽  
Solid Phase ◽  
Mechanical Test ◽  
Fluid Phase ◽  
Element Formulation ◽  
Unconfined Compression ◽  
Element Analysis

A finite element analysis is used to study a previously unresolved issue of the effects of platen-specimen friction on the response of the unconfined compression test; effects of platen permeability are also determined. The finite element formulation is based on the linear KLM biphasic model for articular cartilage and other hydrated soft tissues. A Galerkin weighted residual method is applied to both the solid phase and the fluid phase, and the continuity equation for the intrinsically incompressible binary mixture is introduced via a penalty method. The solid phase displacements and fluid phase velocities are interpolated for each element in terms of unknown nodal values, producing a system of first order differential equations which are solved using a standard numerical finite difference technique. An axisymmetric element of quadrilateral cross-section is developed and applied to the mechanical test problem of a cylindrical specimen of soft tissue in unconfined compression. These studies show that interfacial friction plays a major role in the unconfined compression response of articular cartilage specimens with small thickness to diameter ratios.

Analytical model for a superelastic Timoshenko shape memory alloy beam subjected to a loading–unloading cycle

2018 ◽  
Vol 29 (20) ◽  
pp. 3902-3922 ◽  
Author(s):  
Nguyen Van Viet ◽  
Wael Zaki ◽  
Rehan Umer
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Analytical Model ◽  
Solid Phase ◽  
Three Dimensional ◽  
Element Analysis ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

We propose a new analytical model for a superelastic shape memory alloy prismatic cantilever beam subjected to a concentrated force at the tip. The force is gradually increased and then removed and the corresponding distribution of phase transformation fields in the beam is determined, analytically, in both the transverse and longitudinal directions. Analytical moment–curvature and shear force–shear strain relations are also derived during loading and unloading of the beam. The proposed model is validated against an exact numerical beam model as well as a three-dimensional finite element analysis model for the same beam, with very good agreement in each case. Moreover, an experiment is proposed and carried out to characterize the load–deflection response of a shape memory alloy beam under the same boundary conditions as those considered in deriving the model. The obtained response is in good agreement with the analytical model as well as three-dimensional finite element analysis simulations. The analytical method provides a direct mathematical way for describing the material and structural properties of the beam and the distribution of the different solid phase regions as they change under the influence of an applied load and allows the determination of details such as the boundaries of solid phase regions immediately and accurately using equations. The same would require postprocessing at possibly significant computational cost and personal effort if finite element analysis or similar numerical methods are used.

Correlation Between Structural Changes of Materials During Friction and Finite Element Analysis

2005 ◽  
Author(s):  
D. Barlam ◽  
I. Garbar ◽  
L. Levi
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Structural Changes ◽  
Sliding Friction ◽  
Material Surface ◽  
The Finite Element Method ◽  
Surface Layers ◽  
Element Analysis ◽  
X Ray ◽  
Contact Parameters

The Finite Element Method (FEM) is widely used for modeling strain distribution during friction contact. One of the necessary conditions for such modeling is the correspondence between structural changes in a material surface layers and Finite Element Analysis results. The present study is dedicated to the possibility of using FEM as a tool to predict structural changes of material surface layers during friction depending on material properties and friction conditions. Contact during friction with reciprocating and unidirectional sliding between two surfaces under condition of plane strain had been modeled using commercial Finite Element (FE) code. The correlation between FE results and structural results, obtaining by electron microscopy and X-ray, were studied for the primary and secondary running-in processes. An elastic-plastic model had been used to learn the influence of different contact parameters such as: pressure, hardening, friction coefficient and geometry of asperities on the FE modeling results. Correlation between the FEM predictions and structural results such as dislocation’s density and distribution, were studied in a qualitative manner revealing that plastic strain results can be used to predict structural changes of material under sliding friction.

scholarly journals Optimization of Time-Weighted Average Air Sampling by Solid-Phase Microextraction Fibers Using Finite Element Analysis Software

2018 ◽  
Author(s):  
Bulat Kenessov ◽  
Jacek A. Koziel ◽  
Nassiba Baimatova ◽  
Olga P. Demyanenko ◽  
Miras Derbissalin
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Solid Phase Microextraction ◽  
Solid Phase ◽  
Weighted Average ◽  
Air Sampling ◽  
Internal Diameter ◽  
Analysis Software ◽  
Element Analysis ◽  
Time Weighted Average

Determination of time-weighted average (TWA) concentrations of volatile organic compounds (VOCs) in air using solid-phase microextraction (SPME) is advantageous over other sampling techniques, but is often characterized by insufficient accuracies, particularly at longer sampling times. Experimental investigation of this issue and disclosing the origin of the problem is problematic and often not practically feasible due to high uncertainties. This research is aimed at developing the model of TWA extraction process and optimization of TWA air sampling by SPME using finite element analysis software (COMSOL Multiphysics). It was established that sampling by porous SPME coatings with high affinity to analytes is affected by slow diffusion of analytes inside the coating, an increase of analytes concentrations in the air near the fiber tip due to equilibration, and eventual lower sampling rate. The increase of a fiber retraction depth (Z) resulted in better recoveries. Sampling of studied VOCs using 23-ga Car/PDMS assembly at maximum possible Z (40 mm) was proven to provide more accurate results. Alternative sampling configuration based on 78.5 x 0.75 mm i.d. SPME liner was proven to provide similar accuracy at improved detection limits. Its modification with the decreased internal diameter from the sampling side should provide even better recoveries. The developed model offers new insight into optimization of air and gas sampling using SPME.

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