Non-standard contact conditions in generalized continua: microblock contact model for a Cosserat body

The friction and wear of rolling and sliding contacts are critical factors for the operation of machine elements such as bearings, gears, and cam mechanisms. In precision machines, for example, the main concern is to compensate for frictional losses, so as to improve control accuracy. In other applications it is often desirable to minimize friction losses to improve efficiency, though sometimes high friction is desired to prevent sliding and wear. The aim of this study is to simulate the behavior of a test equipment and show that simulations can be used to study and optimize mechanical systems that include rolling and sliding contact. Simulations can be used to study the system as a whole, as well as the contact conditions. The test equipment and the measurement procedure used are described. In the simulations, a contact model designed to handle transient contact conditions is integrated into a system model. The results show that the contact strongly influences the system. The simulations show that the use of a contact model allows the simulation of systems that contain contacts with different amounts of slip, and that such simulations can be used to study the contact as well as the system. Surface roughness influences the contact stiffness and is included in the simulations.

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Thermal Elasto-Plastic Contact Model of Rough Surfaces

World Tribology Congress III, Volume 1 ◽

10.1115/wtc2005-63810 ◽

2005 ◽

Cited By ~ 1

Author(s):

Geng Liu ◽

Tianxiang Liu ◽

Qin Xie ◽

Fanghui Shi

Keyword(s):

Thermal Effects ◽

Rough Surfaces ◽

Frictional Heating ◽

Contact Model ◽

Stress Fields ◽

Real Contact Area ◽

Plastic Behavior ◽

Contact Conditions ◽

Real Contact ◽

Frictional Coefficients

A thermal elasto-plastic contact model is developed in this paper to investigate the influences of steady-state frictional heating on the contact performance of surface asperities and subsurface stress fields. This model takes into account the asperity distortion caused by temperature variation in a tribological process, micro plastic flow of surface asperities, and the coupled thermo-elasto-plastic behavior of materials, with and without considering the strain-hardening property of the materials. The model is verified through the contact analysis between a rigid, isolated cylinder and a plane. Furthermore, the thermal effects on the contact pressure, real contact area, and average gap of rough surfaces in contact with different frictional coefficients and heat inputs under the thermal elasto-plastic contact conditions are studied.

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Non-Thrombogenicity of Clean Glass Revealed by Native Whole Blood Assay in Bead Columns

Thrombosis and Haemostasis ◽

10.1055/s-0038-1665319 ◽

1983 ◽

Vol 50 (04) ◽

pp. 814-820 ◽

Cited By ~ 1

Author(s):

J A Bergeron ◽

J M DiNovo ◽

A F Razzano ◽

W J Dodds

Keyword(s):

Whole Blood ◽

Glass Bead ◽

Factor Xii ◽

Platelet Factor ◽

Serotonin Content ◽

Whole Blood Assay ◽

Vascular Integrity ◽

Blood Assay ◽

Standard Contact ◽

Recalcification Time

SummaryThe previously described native whole blood assay for materials in solution or suspension has been adapted to materials in a bead column configuration. These experiments showed that the glass itself accounts for little or none of the high blood-reactivity observed with conventional glass bead columns. Columns composed solely of soft glass that was “cleaned” by heat treatment (500-595° C 18 hr, electric oven) were benign toward flowing native whole blood for all variables measured (platelet count and platelet-free plasma [C14]-serotonin content, platelet factor 3 and factor XII activities, and recalcification time) with the standard contact protocol. In addition, the effluent successfully maintained perfusion of the isolated kidney, a measure of the ability of platelets to support vascular integrity. Prolonged (30 min) normothermic contact with titrated whole blood increased the subsequent reactivity of initially clean glass toward whole blood albeit to a level much less than that of conventional glass bead columns.

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Failure Classification Study of X70 Pipeline Crossing Earthquake Fault Based on Shell-Contact Model

ICPTT 2011 ◽

10.1061/41202(423)100 ◽

2011 ◽

Author(s):

Xiangzhen Yan ◽

Lisong Zhang ◽

Xiujuan Yang

Keyword(s):

Contact Model ◽

Earthquake Fault ◽

Failure Classification ◽

Pipeline Crossing

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Microstructure simulation of early paper forming using immersed boundary methods

TAPPI Journal ◽

10.32964/10.32964/tj10.11.23 ◽

2011 ◽

Vol 11 (11) ◽

pp. 23-30 ◽

Cited By ~ 5

Author(s):

ANDREAS MARK ◽

ERIK SVENNING ◽

ROBERT RUNDQVIST ◽

FREDRIK EDELVIK ◽

ERIK GLATT ◽

...

Keyword(s):

Early Paper ◽

Contact Model ◽

Fiber Suspension ◽

Beam Equation ◽

Immersed Boundary ◽

Paper Machine ◽

Immersed Boundary Methods ◽

Element Discretization ◽

Microstructure Simulation ◽

Boundary Methods

Paper forming is the first step in the paper machine where a fiber suspension leaves the headbox and flows through a forming fabric. Complex physical phenomena occur as the paper forms, during which fibers, fillers, fines, and chemicals added to the suspension interact. Understanding this process is important for the development of improved paper products because the configuration of the fibers during this step greatly influences the final paper quality. Because the effective paper properties depend on the microstructure of the fiber web, a continuum model is inadequate to explain the process and the properties of each fiber need to be accounted for in simulations. This study describes a new framework for microstructure simulation of early paper forming. The simulation framework includes a Navier-Stokes solver and immersed boundary methods to resolve the flow around the fibers. The fibers were modeled with a finite element discretization of the Euler-Bernoulli beam equation in a co-rotational formulation. The contact model is based on a penalty method and includes friction and elastic and inelastic collisions. We validated the fiber model and the contact model against demanding test cases from the literature, with excellent results. The fluid-structure interaction in the model was examined by simulating an elastic beam oscillating in a cross flow. We also simulated early paper formation to demonstrate the potential of the proposed framework.

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Cosserat Modeling of Size Effects in Crystalline Solids

MRS Proceedings ◽

10.1557/proc-653-z8.2 ◽

2000 ◽

Vol 653 ◽

Author(s):

Samuel Forest

Keyword(s):

Stress State ◽

Size Effects ◽

Elastic Inclusion ◽

Characteristic Size ◽

Infinite Matrix ◽

Crystalline Solids ◽

Generalized Continua ◽

Absolute Size ◽

Kink Bands ◽

The Matrix

AbstractThe mechanics of generalized continua provides an efficient way of introducing intrinsic length scales into continuum models of materials. A Cosserat framework is presented here to descrine the mechanical behavior of crystalline solids. The first application deals with the problem of the stress field at a crak tip in Cosserat single crystals. It is shown that the strain localization patterns developping at the crack tip differ from the classical picture : the Cosserat continuum acts as a bifurcation mode selector, whereby kink bands arising in the classical framework disappear in generalized single crystal plasticity. The problem of a Cosserat elastic inclusion embedded in an infinite matrix is then considered to show that the stress state inside the inclusion depends on its absolute size lc. Two saturation regimes are observed : when the size R of the inclusion is much larger than a characteristic size of the medium, the classical Eshelby solution is recovered. When R is much small than the inclusion, a much higher stress is reached (for an inclusion stiffer than the matrix) that does not depend on the size any more. There is a transition regime for which the stress state is not homogeneous inside the inclusion. Similar regimes are obtained in the study of grain size effects in polycrystalline aggregates of Cosserat grains.

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A Quantitative Theory for the Computation of Tire Friction Under Severe Conditions of Sliding

Tire Science and Technology ◽

10.2346/1.2148766 ◽

1986 ◽

Vol 14 (1) ◽

pp. 44-72 ◽

Cited By ~ 4

Author(s):

C. M. Mc C. Ettles

Keyword(s):

Friction Coefficient ◽

Flash Temperature ◽

Contact Conditions ◽

Quantitative Form ◽

Heating Effects ◽

Rubber Friction ◽

Viscoelastic Effects ◽

Tire Friction ◽

Pavement Friction ◽

Metal Polymer

Abstract It is proposed that tire-pavement friction is controlled by thermal rather than by hysteresis and viscoelastic effects. A numerical model of heating effects in sliding is described in which the friction coefficient emerges as a dependent variable. The overall results of the model can be expressed in a closed form using Blok's flash temperature theory. This allows the factors controlling rubber friction to be recognized directly. The model can be applied in quantitative form to metal-polymer-ice contacts. Several examples of correlation are given. The difficulties of characterizing the contact conditions in tire-pavement friction reduce the model to qualitative form. Each of the governing parameters is examined in detail. The attainment of higher friction by small, discrete particles of aluminum filler is discussed.

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