The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform

Olayinka R. Karim - One of the best experts on this subject based on the ideXlab platform.

  • Effect of variety and moisture content on some engineering properties of paddy rice
    Journal of Food Science and Technology, 2011
    Co-Authors: Abdul-rasaq A. Adebowale, Lateef O. Sanni, Hameed O. Owo, Olayinka R. Karim
    Abstract:

    The effect of variety and moisture content on some engineering properties of five improved paddy rice varieties was investigated within moisture content range of 10% and 30% dry basis (d.b.). Increase in moisture content was found to increase the linear dimensions, mass of 100 seeds, surface area, apparent volume, true volume, arithmetic mean diameter, effective geometric diameter, sphericity, angle of repose, porosity and Static Coefficient of friction while bulk density and true density decreased with increase in moisture content. Static Coefficient of friction was found to increase as moisture content increased from 0.34–0.46, 0.35–0.59, 0.36–0.46 and 0.34–0.45, respectively on plywood, galvanized steel, mild steel and glass structural surfaces. The highest Static Coefficient was found on galvanized steel. Angle of repose was found to increase as moisture content increases. The study concludes that variety and changes in moisture content significantly ( P  

  • Effect of variety and moisture content on some engineering properties of paddy rice
    Journal of food science and technology, 2010
    Co-Authors: Abdul-rasaq A. Adebowale, Lateef O. Sanni, Hameed O. Owo, Olayinka R. Karim
    Abstract:

    The effect of variety and moisture content on some engineering properties of five improved paddy rice varieties was investigated within moisture content range of 10% and 30% dry basis (d.b.). Increase in moisture content was found to increase the linear dimensions, mass of 100 seeds, surface area, apparent volume, true volume, arithmetic mean diameter, effective geometric diameter, sphericity, angle of repose, porosity and Static Coefficient of friction while bulk density and true density decreased with increase in moisture content. Static Coefficient of friction was found to increase as moisture content increased from 0.34–0.46, 0.35–0.59, 0.36–0.46 and 0.34–0.45, respectively on plywood, galvanized steel, mild steel and glass structural surfaces. The highest Static Coefficient was found on galvanized steel. Angle of repose was found to increase as moisture content increases. The study concludes that variety and changes in moisture content significantly (P < 0.05) affected most of the engineering properties determined.

Jean-louis Thonnard - One of the best experts on this subject based on the ideXlab platform.

  • Simple and Reliable Method to Estimate the Fingertip Static Coefficient of Friction in Precision Grip
    IEEE Transactions on Haptics, 2016
    Co-Authors: Allan Barrea, David Cordova Bulens, Philippe Lefèvre, Jean-louis Thonnard
    Abstract:

    —The Static Coefficient of friction (m Static) plays an important role in dexterous object manipulation. Minimal normal force (i.e., grip force) needed to avoid dropping an object is determined by the tangential force at the fingertip-object contact and the frictional properties of the skin-object contact. Although frequently assumed to be constant for all levels of normal force (NF, the force normal to the contact), m Static actually varies nonlinearly with NF and increases at low NF levels. No method is currently available to measure the relationship between m Static and NF easily. Therefore, we propose a new method allowing the simple and reliable measurement of the fingertip m Static at different NF levels, as well as an algorithm for determining m Static from measured forces and torques. Our method is based on active, back-and-forth movements of a subject's finger on the surface of a fixed six-axis force and torque sensor. m Static is computed as the ratio of the tangential to the normal force at slip onset. A negative power law captures the relationship between m Static and NF. Our method allows the continuous estimation of m Static as a function of NF during dexterous manipulation, based on the relationship between m Static and NF measured before manipulation.

  • A continuous measure of fingertip friction during precision grip.
    Journal of neuroscience methods, 2009
    Co-Authors: Thibaut André, Philippe Lefèvre, Jean-louis Thonnard
    Abstract:

    When humans manipulate an object, the minimal grip force (GF) required to avoid slipping depends on the frictional properties between the fingers and the object. As a consequence, fingertip skin friction plays a critical role during object manipulation. Here, the effects of the normal force and moisture content on the skin's Static Coefficient of friction (CF) for human fingertips were studied. Ten subjects were asked to pinch an object with a given normal force. Slippage of the object on the fingertips was generated for different ranges of normal force using a linear translation stage. The exerted forces and moisture of the fingertips were then measured, and the Static Coefficient of friction was calculated as the ratio between the tangential force and normal force at slippage. These results demonstrate that the effects of the normal force and moisture content on the CF exhibit a complex interaction. For a given moisture condition, the CF varies as a power function of the normal force; in contrast, for a given normal force, the CF is described by a "bell-shaped" function of moisture. A global expression of the CF as a function of the normal force and moisture content is derived, and a method is proposed for a continuous measure of the CF. This new method shall be of particular interest in investigating dexterous manipulation.

Habib S Benabdallah - One of the best experts on this subject based on the ideXlab platform.

  • Static friction Coefficient of some plastics against steel and aluminum under different contact conditions
    Tribology International, 2007
    Co-Authors: Habib S Benabdallah
    Abstract:

    The Static friction behavior was investigated in the case of POM-based polymers containing additives, designated DE20076, DE100KM and DE12017 as well as Nylon-66 designated ZY103HSL, when in contact with AISI 1045 steel and 6061 aluminum alloy. A designed apparatus that detects the exact moment corresponding to the transition from rest to slip was used to measure the Coefficient of Static friction. The impact of normal load, dwell time before slip, apparent area of contact and lubrication by water and paraffin oil on the Static friction characteristics was studied. A decrease of the Static Coefficient of friction with low normal load followed by a levelling off governed by its effect on the real area of contact and stiffness of the counterface was observed. This also yielded a linear decrease of slip acceleration as well as stick time. A polynomial equation, which increases monotonically, was found to express well the effect of stick time on Static friction, independently of the materials in contact. Adhesive effects were generated by the presence of both lubricants with the result of increase of the Static Coefficient of friction.

Kyriakos Komvopoulos - One of the best experts on this subject based on the ideXlab platform.

  • The Effect of Adhesion on the Static Friction Properties of Sidewall Contact Interfaces of Microelectromechanical Devices
    Journal of Microelectromechanical Systems, 2006
    Co-Authors: Shannon J. Timpe, Kyriakos Komvopoulos
    Abstract:

    Static friction between sidewall contact surfaces of polycrystalline silicon micromachines was investigated under different contact pressures, vacuum conditions, relative humidity levels, and temperatures. The Static Coefficient of friction exhibited a nonlinear dependence on the external contact pressure. A difference between in-contact and pull-out adhesion forces was observed due to the elastic recovery of the deformed asperities at the contact interface. The true Static Coefficient of friction was determined by considering the effects of the dominant adhesion forces (i.e., van der Waals and capillary forces) on the normal force applied at the sidewall contact interface. The roles of van der Waals and capillary forces in the sidewall friction behavior were analyzed in light of results for the interfacial shear strength and the adhesion force. The major benefits of the present friction micromachine and the developed experimental scheme are discussed in the context of Static Coefficient of friction and adhesion force results obtained under different environmental and loading conditions

  • A Mechanics Approach to Static Friction of Elastic–Plastic Fractal Surfaces
    Journal of Tribology, 2005
    Co-Authors: Jun Yang, Kyriakos Komvopoulos
    Abstract:

    A contact mechanics theory of Static friction is presented for isotropic rough surfaces exhibiting fractal behavior. The analysis is based on a piecewise power-law size distribution and a normal slope distribution of the asperity contacts and elastic-fully plastic deformation models. Numerical integration yields solutions for the normal and friction forces in terms of fractal parameters, elastic-plastic material properties, and interfacial shear strength. The variation of the Static Coefficient of friction with normal load is related to the effect of the surface topography on the dominant deformation mode at the asperity contacts. Plastic deformation of the smaller asperity contacts dominates at low loads and elastic deformation of the larger asperity contacts dominates at high loads. The critical load signifying the transition from predominantly plastic to elastic deformation depends on the fractal parameters and material properties. In the low-load range, the Static Coefficient of friction decreases with the increase of the load, while in the high-load range it increases with the load. Numerical results for copper fractal surfaces illustrate the effects of normal load, surface topography, and interfacial shear strength on the Static Coefficient of friction.

  • Static friction in polysilicon surface micromachines
    Journal of Microelectromechanical Systems, 2005
    Co-Authors: A. Lumbantobing, Kyriakos Komvopoulos
    Abstract:

    Surface micromachines of polycrystalline silicon were used to investigate the dependence of Static friction in microelectromechanical systems on the external load, apparent contact area, and environmental conditions. An analytical model of the micromachine at the inception of sliding was used to determine the normal load consisting of the restoring and levitation forces exerted by the micromachine's comb-drive actuators. The apparent shear strength at the contact interface(s) exhibited a nonlinear dependence on the apparent contact pressure. Relatively higher Static Coefficient of friction and interfacial shear strength were obtained in room air than vacuum ambient. The Static Coefficient of friction was found to depend on the normal load, apparent contact area, and ambient conditions (i.e., relative humidity). Electrical contact resistance measurements indicated that sliding in room air promoted thickening of the native oxide film at asperity contacts. The experimental evidence suggests that modification of the surface topography occurred at the asperity level. However, these submicroscopic changes in the surface topography did not affect the overall Static friction behavior, for the test cycles simulated in the friction experiments.

  • A Mechanics Approach to Static Friction of Elastic-Plastic Fractal Surfaces
    ASME STLE 2004 International Joint Tribology Conference Parts A and B, 2004
    Co-Authors: Jun Yang, Kyriakos Komvopoulos
    Abstract:

    A contact mechanics theory of Static friction is presented for isotropic rough surfaces exhibiting fractal behavior. The analysis is based on a piece-wise power-law size distribution and a normal slope distribution of the asperity contacts and elastic-fully plastic deformation models. Numerical integration yields solutions for the normal and friction forces in terms of fractal parameters, elastic-plastic material properties, and interfacial shear strength. The variation of the Static Coefficient of friction with normal load is related to the effect of the surface topography on the dominant deformation mode at the asperity contacts. Plastic deformation of the smaller asperity contacts dominates at low loads and elastic deformation of the larger asperity contacts at high loads. The critical load signifying the transition from predominantly plastic to elastic deformation depends on the fractal parameters and material properties. In the low-load range, the Static Coefficient of friction decreases with the increase of the load, while in the high-load range it increases relatively faster with the load. Numerical results for copper fractal surfaces illustrate the effects of normal load, surface topography, and interfacial shear strength on the Static Coefficient of friction.Copyright © 2004 by ASME

Natalia Nuño - One of the best experts on this subject based on the ideXlab platform.

  • Static Coefficient of friction between stainless steel and PMMA used in cemented hip and knee implants
    Clinical biomechanics (Bristol Avon), 2006
    Co-Authors: Natalia Nuño, R. Groppetti, Nicola Senin
    Abstract:

    Abstract Background Design of cemented hip and knee implants, oriented to improve the longevity of artificial joints, is largely based on numerical models. The Static Coefficient of friction between the implant and the bone cement is necessary to characterize the interface conditions in these models and must be accurately provided. The measurement of this Coefficient using a repeatable and reproducible methodology for materials used in total hip arthroplasty is missing from the literature. Methods A micro-topographic surface analysis characterized the surfaces of the specimens used in the experiments. The Coefficient of friction between stainless steel and bone cement in dry and wet conditions using bovine serum was determined using a prototype computerized sliding friction tester. The effects of surface roughness (polished versus matt) and of contact pressure on the Coefficient of friction have also been investigated. Findings The serum influences little the Coefficient of friction for the matt steel surface, where the mechanical interactions due to higher roughness are still the most relevant factor. However, for polished steel surfaces, the restraining effect of proteins plays a very relevant role in increasing the Coefficient of friction. Interpretation When the Coefficient of friction is used in finite element analysis, it is used for the debonded stem–cement situation. It can thus be assumed that serum will propagate between the stem and the cement mantle. The authors believe that the use of a Static Coefficient of friction of 0.3–0.4, measured in the present study, is appropriate in finite element models.

  • Static Coefficient of friction between Ti-6Al-4V and PMMA for cemented hip and knee implants
    Journal of biomedical materials research, 2001
    Co-Authors: Natalia Nuño, M. Amabili, R. Groppetti, A. Rossi
    Abstract:

    The Static Coefficient of friction between Ti-6Al-4V and PMMA was determined experimentally. A microtopographic surface analysis of the Ti-6Al-4V and PMMA specimens used in the experiments was performed to characterize the surfaces. The Coefficient of friction between Ti-6Al-4V and PMMA in both dry and wet conditions, using both Ringer's solution and bovine serum, was determined by the standard inclined plane test, following the ASTM 4516-91 method, and by a prototype computerized sliding friction tester. The effects of surface roughness and of contact pressure on the Coefficient of friction also have been investigated. Tests were performed at 26 degrees C and at body temperature of 37 degrees C. Considering all the tests, the overall range of the mean Coefficients of friction varied between 0.17 and 0.32 in dry or wet conditions. For the same surface roughness in contact, in general the Coefficient of friction using Ringer's solution was slightly lower than it was in dry conditions whereas bovine serum had a very high surface tension, which significantly increased the Static Coefficient of friction.