Documents disponibles écrits par cet auteur

On elastic interaction of nominally flat rough surfaces / A. Sepehri in Transactions of the ASME . Journal of tribology, Vol. 130 N°1 (Janvier 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 130 N°1 (Janvier 2008) . - 5 p. Titre : On elastic interaction of nominally flat rough surfaces Type de document : texte imprimé Auteurs : A. Sepehri, Auteur ; K. Farhang, Auteur Année de publication : 2008 Article en page(s) : 5 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Force  Separation  (Technology)  Surface  roughness  Stress  Optimization  Approximation  Equations  Errors Résumé : A hybrid interactive/optimization technique is used to derive in approximate closed-form equations relating contact load to mean plane separation. Equations governing Hertz contact for the interaction of surface asperities are considered in which asperity shoulder-to-shoulder contact results in normal and tangential components of force. The normal component of asperity force is summed statistically to find total normal force between the two surfaces. The tangential force over a half-plane corresponding to a select direction is found accounting for the directionality of the tangential component of asperity forces. Two sets of approximate equations are found for each of the normal and half-plane tangential force components. The simplest forms of the approximate equations achieve accuracy to within 5% error, while other forms yield approximation error within 0.2%. En ligne : http://tribology.asmedigitalcollection.asme.org/article.aspx?articleid=1467980 [article] On elastic interaction of nominally flat rough surfaces [texte imprimé] / A. Sepehri, Auteur ; K. Farhang, Auteur . - 2008 . - 5 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 130 N°1 (Janvier 2008) . - 5 p. Mots-clés : Force  Separation  (Technology)  Surface  roughness  Stress  Optimization  Approximation  Equations  Errors Résumé : A hybrid interactive/optimization technique is used to derive in approximate closed-form equations relating contact load to mean plane separation. Equations governing Hertz contact for the interaction of surface asperities are considered in which asperity shoulder-to-shoulder contact results in normal and tangential components of force. The normal component of asperity force is summed statistically to find total normal force between the two surfaces. The tangential force over a half-plane corresponding to a select direction is found accounting for the directionality of the tangential component of asperity forces. Two sets of approximate equations are found for each of the normal and half-plane tangential force components. The simplest forms of the approximate equations achieve accuracy to within 5% error, while other forms yield approximation error within 0.2%. En ligne : http://tribology.asmedigitalcollection.asme.org/article.aspx?articleid=1467980

A two-parameter function for nanoscale indentation measurement of near surface properties / K. Farhang in Transactions of the ASME . Journal of tribology, Vol. 130 N°1 (Janvier 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 130 N°1 (Janvier 2008) . - 6 p. Titre : A two-parameter function for nanoscale indentation measurement of near surface properties Type de document : texte imprimé Auteurs : K. Farhang, Auteur ; L. E. Seitzman, Auteur ; B. Feng, Auteur Année de publication : 2008 Article en page(s) : 6 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Nanoscale  phenomena  Surface  properties  Displacement  Equations  Errors  Elasticity  Functions  Shapes  Crystals  Force  measurement Résumé : A two-parameter function for estimation of projected area in instrumented indentation measurement is obtained to account for indenter tip imperfection. Imperfection near indenter tip is modeled using a spherical function and combined with a linear function describing the edge boundary of the indenter. Through an analytical fusion technique, the spherical and linear functions are combined into a single function with two unknown geometric parameters of tip radius of curvature and edge slope. Data from indentation measurement of force and displacement, using a Berkovich tip and single crystal alumina and silica samples, are implemented in the proposed area function yielding estimated values of Young’s modulus. Results were compared with that obtained from Oliver and Pharr technique for deep as well as shallow indentation regimes. The estimates for Young’s modulus were found to agree quite favorably. More importantly, in contrast to the Oliver–Pharr technique, the use of the two-parameter function resulted in a significantly more accurate estimation of Young’s modulus for shallow indentation depth of 0–50nm. The error in estimation of Young’s modulus was found to be within 10% for indentation depths of 25–50nm and within 20% for indentation depths of 0–25nm. En ligne : http://tribology.asmedigitalcollection.asme.org/article.aspx?articleID=1467964 [article] A two-parameter function for nanoscale indentation measurement of near surface properties [texte imprimé] / K. Farhang, Auteur ; L. E. Seitzman, Auteur ; B. Feng, Auteur . - 2008 . - 6 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 130 N°1 (Janvier 2008) . - 6 p. Mots-clés : Nanoscale  phenomena  Surface  properties  Displacement  Equations  Errors  Elasticity  Functions  Shapes  Crystals  Force  measurement Résumé : A two-parameter function for estimation of projected area in instrumented indentation measurement is obtained to account for indenter tip imperfection. Imperfection near indenter tip is modeled using a spherical function and combined with a linear function describing the edge boundary of the indenter. Through an analytical fusion technique, the spherical and linear functions are combined into a single function with two unknown geometric parameters of tip radius of curvature and edge slope. Data from indentation measurement of force and displacement, using a Berkovich tip and single crystal alumina and silica samples, are implemented in the proposed area function yielding estimated values of Young’s modulus. Results were compared with that obtained from Oliver and Pharr technique for deep as well as shallow indentation regimes. The estimates for Young’s modulus were found to agree quite favorably. More importantly, in contrast to the Oliver–Pharr technique, the use of the two-parameter function resulted in a significantly more accurate estimation of Young’s modulus for shallow indentation depth of 0–50nm. The error in estimation of Young’s modulus was found to be within 10% for indentation depths of 25–50nm and within 20% for indentation depths of 0–25nm. En ligne : http://tribology.asmedigitalcollection.asme.org/article.aspx?articleID=1467964