Presence Of Friction Research Articles

摩擦作用下の四点曲げにおけるはりの大たわみ変形 負荷，反力両支点で摩擦係数が互いに異なる場合

In recent years, it has been found that a widely-used plate spring for a measuring instrument, a multi-purpose plastic, a paper sheet, a fabric and so on have the characteristic of large deflection. Therefore, it is of great technological interest to know, for various loading styles, what kind of deflection occurs and how the deflection appears. In this report, analytical solutions are derived for several flexural quantities such as a deflection, an arc length, a curvature, a bending stress and it is proved that the load bearing capacity of beam becomes higher in the presence of friction. An experiment is performed to confirm the applicability of the proposed large deflection theory. The experimental results agree well with the theoretical ones. Moreover, a reduction technique is presented to estimate easily the specified flexural quantities in large deflection states from a conventional linear bending theory.

Linear finite-element analysis of a cylindrical forging-die under load

Based on the Siebel analysis, the stress distribution generated at the material/die interface during a forging operation within a cylindrical die is predicted. The predicted stress distribution covers the process of forging with flash and without flash in the presence of friction, the coefficient of which is taken as zero or 0.1. Using these stress boundary conditions in a linear finite-element analysis of deformation, the present work explores the influence of a shrink ring, and of friction, on the die under forging load.

Boltzmann statistics of quantum friction

In this paper we investigate the thermodynamic properties of simple quantum-mechanical systems in the presence of friction. Using the propagators for these simple models we calculate the response functions in Boltzmann statics. In the low temperature region the response functions exhibit singular behaviour.

A mixed computational algorithm for plane elastic contact problems—I. formulation

A mixed variational statement and corresponding finite element model are developed for an arbitrary plane body undergoing large deformations (i.e. large displacements, large rotations and small strains) under external loads using the updated Lagrangian formulation. The mixed finite element formulation allows the nodal displacements and stresses to be approximated independently. Two different contact algorithms are presented for the separate cases of a thin plate in contact with a rigid pin and a flexible pin, and the algorithms account for the computational difficulties that arise from the unknown contact area and the presence of friction between the pin and the plate.

Treatment of contact boundaries with friction by direct minimization

This paper deals with linear elastic structures with nonlinear boundary conditions. The source of nonlinearity is the presence of friction in some of the supports. In addition some of these supports may be of the resting/lifting type or may be gap boundaries where movement is restricted between specified limits. Examples are resting supports of piping systems, rigid foundations on soil, guided pipes, etc. A generalized form of the principle of minimum complementary potential within the context of a force formulation is used to cast the problem as a minimization problem. It is shown how this leads to a quadratic programming problem whose minimum provides a direct solution. Numerical examples are given to demonstrate the accuracy of the approach and its efficiency.

Preform design in disk forging

The investigation deals with a preform design problem in an axisymmetric disk forging where it is required to produce a uniformly deformed flat disk under the presence of friction at the die-workpiece interface. The backward tracing scheme by the finite element method was applied with criteria for controlling the boundary conditions during the process. Three design approaches were presented, and the suggested final design was evaluated by performing simulation. It was concluded that satisfactory results can be achieved by the use of the backward tracing method.

Stresses around a pin-loaded hole in orthotropic plates with arbitrary loading direction

Lekhnitskii's method of complex stress function is extensively used to solve the pin-loaded circular hole problem in an infinite orthotropic plate. The approach is similar to the one used earlier by the authors, but extended into a more general fashion. The direction of pin-load is arbitrary and the presence of friction is considered. An analytic solution which satisfies the major displacement boundary conditions on the pin-loaded hole has been obtained. Certain parameters are introduced for simplifying the expressions. These formulas can be used for computing the stress distribution around a pin-loaded hole and estimating the effect of direction of the pin-load and the presence of friction. The degree of such an effect depends on the orthotropy of the material. Some numerical results have been calculated and presented in this paper. They are compared with other results available in the literature.

An analysis of pressure sintering by computer simulation

This paper describes the results of computer simulation of pressure sintering using Finite Element Analysis for isostatic as well as uniaxial pressing conditions. An effective pressure concept for obtaining analytical description of the densification rate in terms of porosity and the basic creep properties of the material is also presented. Equations are also derived to take into account the presence of friction at the die walls. Results of computer analysis are used to corroborate the theoretical derivations.

A Simple Mechanism for Blocking

Numerical experiments show that blocking in a barotropic atmosphere can occur as a resonant enhancement of Rossby lee waves forced by two stationary sources of potential vorticity. In particular, if an upstream source of stationary forcing enhances the northerly flow over orography, then blocking occurs downstream of the mountain. In an analytical study, we show that, in the presence of friction, Rossby lee waves generate a rectified current downstream of the mountain, which does not vanish in the limit of zero friction. The relevance of this study to observed generation of blocking in the Atlantic Ocean and immediately upstream of the Rockies is discussed.

On Modelling the Statistical Strength of Yarns and Cables Under Localized Load-Sharing Among Fibers

This paper describes a statistical model for the strength of long, slender, fibrous structures such as yarns and cables. Emphasis is on the effect of strong mechanical interactions among fibers that arise from the presence of friction or a binding matrix. Basic features are that the structure is viewed as a long chain of statistically and structurally independent bundles whose lengths depend on the local mechanics of fibers at breaks. Within each bundle, localized load-sharing occurs among non-failed fiber elements depending on the local mechanics and fiber spatial geometry. The strengths of the fiber elements vary statistically and are modelled by a Weibull distribution. The analysis is for bundles with few fibers, though previous results under more idealized conditions suggest that the key features of the results will prevail also for much larger bundles. Key conclusions are that, for all practical purposes, a Weibull distribution describes the statistical strength of yarns and cables. The variability in fiber strength has a strong negative effect on the median strength of the yarn or cable and very little effect on its variability in strength. As the load-sharing becomes more diffuse, the median strength of the yarn or cable rises moderately. The size effect for the strength of the cable is very mild when compared to that for the fiber.

Chaos in the segmented disc dynamo

It is shown that the equations describing the segmented disc dynamo in the presence of friction are identical to the Lorenz equations.

On equilibrium in the presence of friction II

On equilibrium in the presence of friction II

Rotating barotropic flow over finite isolated topography

The flow of a rotating, incompressible fluid over isolated topography whose non-dimensional height (i.e. topographic height divided by the mean fluid depth) is large compared with the Rossby number is studied. Attention is restricted to flow which is sufficiently shallow that the free-surface equations provide an adequate description. The flow is forced laterally by a specified upstream inflow (obtained from solutions of the zonally symmetric model equations) and by a prescribed surface stress. Dissipation is incorporated using a Rayleigh friction acting anti-parallel to the flow.Steady-state solutions for uniform inflow on an f-plane are found for (a) linear viscous flow, (b) quasi-geostrophic flow with and without friction and (c) inviscid flow with and without a rigid lid. The presence of friction produces an upstream–downstream flow asymmetry over the obstacle and an associated topographic drag while inertial terms produce left-right (relative to an observer looking downstream) asymmetry. The blocking efficiency B (the percentage of the incident mass flux going around the obstacle rather than over it) of a Gaussian obstacle is largest (∼ 100%) for case (a) when viscous effects are small. In contrast quasi-geostrophic theory calculates no flow blocking (B ≡ O). For inviscid inertial theory, B ∼ 10% and is independent of the Rossby number. The presence of a free surface decreases the blocking for small-Rossby-number flow.Numerical solutions of the appropriate initial, boundary-value problem for the complete model equations confirm these results and extend them to include the effects of (i) horizontal shear in the upstream inflow, (ii) the magnitude and shape of the topography, and (iii) variations in the Coriolis parameter (β-effect).

On equilibrium in the presence of friction I

A known equilibrium rule that refers to rigid bodies possibly subject to some external constraintsK(e), and that is essential in many cases where friction is present, is shown to give unacceptable results in some cases that can be carried out experimentally. Then the same rule is replaced by a new one which is more complex. When the bearings that carry outK(e) are kinematically independent in a suitable sense, the new rule is proved to simplify into the old one. The afore-mentioned cases can be treated satisfactorily by means of another simple rule. However this rule is shown to be too weak to treat other (simple) cases.

Momentum transfer from waves to particles

Momentum transfer from an electromagnetic or electrostatic wave to an electron is calculated in the presence of friction, and it is shown that it can be comparable to the one obtained from the ponderomotive force.

On the dynamical process of fault motion in the presence of friction and inhomogeneous initial stress. II. Relation between tectonic field and source parameters.

The Partial differential equation, which represents approximately the propagation of a crack, obtained by YAMASHITA (1976) is solved numerically, and the dependence on the tectonic field of the source parameters is studied in detail. Main results are as follows:The importance of effective stress and the fracture strength distribution for the dynamical process of fault motion is ascertained from the numerical computation and in the interpretation of observed data. The proportional relation between effective stress and dislocation velocity exists, but the ratio is widely different from BRUNE'S (1970) result. Effective stress is linearly proportional to stress drop. When initial stress fields are represented by a pair of linear functions and a quadratic function of the distance in the direction of dislocation surface, the approximate relations σeff≅10Δσ andσeff≅6Δσ hold respectively. Initial stress field of a Japanese inland earthquake is approximated by a pair of linear functions with small slopes. That of an earthquake along the trench is approximated by a quadratic function with a firly large coefficient. The dislocation velocity is in direct proportion to the stress drop.

Some aspects of modeling rock fracture by the optical polarization method

1. The author's investigations show that it is possible to use the optical-polarization method to investigate the stresses in models of certain aspects of the process of rock fracture. 2. The authors suggest a method of modeling the stresses in the neighborhood of stationary cracks in shear or transverse deformation, taking account of interaction between the flanks of the crack in the presence of friction; this permits investigation of a number of problems which have not been solved theoretically. 3. They develop a method of modeling the process of crack propagation under tension. They show that the velocity varies discontinuously. They establish the conditions for branching of a crack. They show that the dynamic stress intensity coefficient depends on the velocity of the crack. 4. They show that it is possible to use dynamic patterns of interference fringes to record the stress waves initiated at various moments during crack propagation during emergence at the free surface or interaction with various types of nonuniformity.

Slip of a rigid cylinder along a viscoelastic foundation in the presence of friction

The problem of the slip of a rigid infinitely long cylinder along a viscoelastic foundation in the presence of friction forces dependent on the slip rate is solved in a linear quasistatic arrangement. The effect of the rheological characteristics of the foundation material and other factors on the point displacement of the surface in front of the moving cylinder is studied. Rather good agreement is obtained between theoretical and experimental data.

On the dynamical process of fault motion in the presence of friction and inhomogeneous initial stress. I. Rupture propagation.

An equation which represents the crack propagation is obtained by approximating the wave equation and the boundary conditions in the neighborhood of the dislocation surface. The problem of crack propagation with an unsteady finite rupture velocity is solved with the aid of this model and the computation is carried out by using the finite difference method. The proposed model takes the rupture propagation as the diffusive phenomena of the inhomogeneous initial stress field. It is clarified in this paper that the most important focal parameters for the dynamical process of fault motion are the effective stress (defined as the static frictional stress minus the sliding frictional stress) and the fracture strength (defined as the static frictional stress minus the initial stress). The former accelerates the fault motion and the latter decelerates it. All the rupture phenomena can be interpreted by the relative magnitude between these stresses. The importance of both stresses is not ascertained until the inhomogeneous initial stress field is introduced.

The Importance of Interfiber Friction in Wrinkling

Some of the more important consequences of interfiber friction in fabric wrinkling are discussed. A simple approxi mate relation for a linear viscoelastic fabric is obtained which relates the residual set at which the fabric ceases recovering to the length of time it was held bent before release. It is also shown how the presence of friction can allow quite high residual deformations to build up following series of short wrinkle-and-recovery cycles. For a typical single wrinkle-and-recovery cycle the frictional moment interacts with the viscoelastic behavior of the single fibers to impose a limit on the final recovery that a fabric may eventually attain. This concept is interpreted in terms of previously defined parameters V and F obtained from a standard test procedure. The importance of evressing the wrinkling behavior of a fabric in terms of its viscoelastic and frictional components is emphasized.