Effect Of Coulomb Friction Research Articles

Effect of Coulomb friction and viscous forces on interfacial waves at steel-steel boundaries under external pressure

Experimental results for the attenuation and velocity of propagation of interfacial waves along a steel-steel plane interface lubricated with a viscous fluid are presented. The bonding at the interface is varied by the application of an external pressure normal to the interface. These measurements are compared with values predicted by a theoretical model where the shear stress at the interface is assumed to be dependent linearly on the slip in displacement and velocity parallel to the interface. Further, the degree of bonding is assumed to be dependent non-linearly on the external pressure. Agreement between the theoretical model and the experimental data is found to be satisfactory. The implications of these results for testing the adhesion of surfaces are briefly discussed.

Interfacial friction analysis for fibre-reinforced composites during fibre push-down (indentation)

Effects of Coulomb friction and radial clamping stress on the mechanical properties at the fibre/matrix interface are considered for fibre-reinforced composites when an axial compressive stress (or indentation) is used to push on the free-surface end of the embedded fibre. The interfacial frictional shear stress, the elastic stress transfer, the length of the sliding zone, and the fibre and the matrix displacements along the fibre length are analysed analytically. Specific results are calculated for SiC-fibre-reinforced AI2O3 composites. The results show that the interfacial shear stress is not constant, but decreases along the fibre length with increasing distance from the surface. Also, the interfacial shear stress increases as the coefficient of friction, the radial clamping stress, or Poisson’s ratio of the fibre increases, which in turn results in an increase in the elastic stress transfer from the fibre to the matrix, and a decrease in both the length of the sliding zone and the fibre displacement in the loading direction. However, when Poisson’s ratio of the matrix increases, the stress transfer from the fibre to the matrix decreases.

Effect of Coulomb friction on a dynamic vibration absorber system with harmonic base excitation. 3rd report. Coulomb friction both in the main system and in the absorber.

Behavior of a dynamic vibration absorber system with combined viscous and Coulomb friction both in the main system and in the absorber is investigated. In this case, the main system is subjected to harmonic base excitation. The solution for the non-stop steady motion is deduced from the equation of motion refering to the half cycle of relative motion between the main mass and the base by means of the boundary condition method. The numerical results of analytical solution coincide very well with those of digital simulation. A set of empirical formulae for calculating the optimum tuning and damping of the absorber, constructed by composing and correcting the formulae given in the previous reports, are prsented.

The Dynamic Performance of an Electrohydraulic Servovalve/Motor System With Transmission Line Effects

The transient response of an electrohydraulic servovalve coupled to an axial piston ball motor is analyzed. In particular, the effect of long lines between the servovalve and motor is studied together with coulomb friction effects at the motor. The dynamic characteristics of the basic system with short lines is first established via frequency response measurements coupled with a small signal linearized analysis. Longer lines are then added and the method of characteristics, coupled with a quasi-analytical solution for the motor-end equations, is used to predict the large signal transient response. The importance of coulomb friction damping is established together with damping due to servovalve dynamics.

The effect of Coulomb friction and Alfven waves on minor ions in the low corona

The properties of minor ions in the low solar corona are studied on the basis of a quasi‐hydrostatic equilibrium model suitably modified to account for the combined effects of Coulomb friction and Alfven wave acceleration in dragging minor ions out of the corona against the binding solar gravitational force. The analysis therefore generalizes the work of Hollweg (1981) to include the effect of waves which become important in the upper corona and the results, which must be treated with some caution, indicate that provided the proton flux is sufficiently large, the ions are evicted from the corona into the wind at the same speed as the protons with relative abundances which reflect their flux relative to protons in the low corona.

Dynamic vibration absorber system excited by a rotating imbalance. (3rd report Effect of Coulomb friction both in the main system and in the absorber)

Dynamic vibration absorber system excited by a rotating imbalance. (3rd report Effect of Coulomb friction both in the main system and in the absorber)

Motion resistance of avalanches on smooth paths

Dimensionless mathematical models are developed for the dynamics of mass-center avalanches on smooth and circular paths. Equations for velocity as a function of position are derived in terms of two dimensionless, spatially averaged resistance factors. A procedure is outlined to estimate the resistance factors and assess the relative effects of Coulomb friction and speed-dependent resistance on avalanche motion.

Experimental microprocessor-based adaptive control system

The performance characteristics of a representative adaptive position control system were investigated using a single-board microprocessor-based controller and a DC motor actuator. The adaptive controller algorithm is capable of compensating for some Coulomb friction effects and will adapt to changes in the inertia of the DC motor load. The adaptive controller design concept used in this application is described, and laboratory test results for the complete system are presented.

Effect of Coulomb friction on a dynamic vibration absorber system with harmonic base excitation. 2nd report Coulomb friction in the main system.

This report presents the effect of Coulomb friction combined with viscous damping in the main system, to which a viscous-damped dynamic vibration absorber is attached. The main system is subjected to harmonic base excitation, and in the analysis, a similar process is used to that explained in the previous report. The conclusions are : -(1) The numerical results of the analytical solution coincide very well with those of digital simulation. (2) Coulomb friction coexisting with the viscous damping in the main system, with a dynamic vibration absorber tuned so as to suppress the resonant response of the system in considering only viscous damping, reduces the maximum amplitudes of the main mass. The features of two equi-height maximums in the resonance curve vanish. (3) Since conventional expressions for the optimum tuning of the absorber do not fit in this case, other new empirical formulae are recommended.

A normally loaded half-plane with an edge crack

An elastic half-plane is subjected to a uniform pressure over part of its surface. A normal edge crack is assumed to lie at the edge of the loaded region. The effect of Coulomb friction between the crack faces is considered, and the various possibilities involving stick and slip regions along the crack are examined. Stress intensity factors are obtained.

Dynamic vibration absorber system excited by a rotating unbalance. 2nd report Effect of Coulomb friction in the main system.

This report presents the effect of Coulomb friction combined with viscous damping in the main system to which a viscous-damped dynamic vibration absorber is attached. The main mass is excited by a rotating unbalance, and in the analysis, a similar process is used to that explained in the previous report(3). Thus, the conclusions are : - (1) The numerical results of analytical solution coincide very well with those of digital simulation. (2) Coulomb friction coexisting with the viscous damping in the main system, with a dynamic vibration absorber tuned so as to suppress the resonant response of the system in considering only viscous damping, reduces the maximum amplitudes of the main mass. The features of two equi-height maximums in the resonance curve vanish. (3) By reason that conventional expressions for the optimum tuning of the absorber do not fit in this case, other new empirical formulae are recommended.

Effect of Coulomb friction on a dynamic vibration absorber system with harmonic base excitation. (1st report, Coulomb friction in the absorber)

The effect of Coulomb friction combined with viscous damping in a dynamic vibration absorber attached to the primary system with viscous damping subjected to the exciting force P0 sin ωt has already been clarified. This study is devoted itself to the same system as the above in another case, in which the primary system is subjected to the harmonic base excitation, u0 sin ωt. The analysis may be proceeded by replacing the amplitude of exciting force P0 in the previous report by a new apparent force, u0√(k21+(c1ω)2). The results of the numerical analysis are compared with those of the digital simulation (HITAC DDS III) with good coincidence. And, it is conclude that the existence of Coulomb friction in the absorber increases the amplitude of main mass and limits the non-stop motion within the narrow range of frequency. A set of empirical formulae for determining the optimum tuning and damping is constructed for the practical use.

Dynamic Vibration Absorber System Excited by a Rotating Unbalance : 1st Report, Effect of Coulomb Friction in the Absorber

Dynamic Vibration Absorber System Excited by a Rotating Unbalance : 1st Report, Effect of Coulomb Friction in the Absorber

Analysis of Dynamic Absorber System with Viscous and Coulomb Friction : 3rd Report, Effect of Coulomb Friction in Main System and Absorber

Analysis of Dynamic Absorber System with Viscous and Coulomb Friction : 3rd Report, Effect of Coulomb Friction in Main System and Absorber

Destabilizing effect of Coulomb friction on vibration of a beam supported at an axially oscillating mount

This paper is concerned with parametric vibration of a beam having one end supported at a motionless mount and the other at an axially oscillating mount. It is shown that the time-history of the motion of the beam may be expressed in terms of jacobi elliptic functions. The effect of the friction force, resulting from the relative motion of the mount and the beam, on the vibration is studied. The instability regions are found and plotted.

Identification of the dynamic characteristics of a structure with coulomb friction

The effect of coulomb friction on the Kennedy and Pancu vector plot of a single degree-of-freedom system is analyzed by using the method of harmonic balance. It is shown that the resulting diagram no longer conforms to a locus of a circle in the resonant region, which restricts the usual methods of analysis. A technique, based upon the in-phase and quadrature power dissipated when exciting a normal mode, is presented which allows the magnitude of the non-linear friction force and the hysteretic damping constant to be evaluated. The technique is also applied to systems having several degrees-of-freedom and it shows that it is possible to identify the characteristics of a single non-linear coulomb device situated within a structure, but in the case of more than one device, the technique has some restrictions. The theoretical results are compared with experimental data from a structure containing a non-linear coulomb device.

Effect of coulomb friction on transients accompanying forced vibrations

Effect of coulomb friction on transients accompanying forced vibrations

Exact Analysis of Relay Control System with Hysteresis and Coulomb Friction

Exact phase plane analysis of nonlinear system containing two-position relay element, with hysteresis under the consideration of Coulomb friction, is given. Expressions for period and amplitude of stable limit cycle are derived. The effect of Coulomb friction on limit cycle behaviour is also discussed.

The Hunting Behavior of Conventional Railway Trucks

Railway vehicles under certain conditions experience sustained lateral oscillations during which the wheel flanges bang from one rail to the other. It has been found that this behavior, called hunting, only occurs above certain critical forward velocities. Approximations to these critical velocities have been found from a stability analysis of the linear equations of motion for many different railway vehicle models. Hunting is characterized by violent motions that impose large loads on the vehicle and track, and bring several important nonlinear effects into play. This paper reports results of an analysis of nonlinear equations of motion written for two models of a railway truck. The influence of the nonlinear effects on stability is determined and the character of the hunting motion is investigated. One model represents a truck whose axle bearings are rigidly held in the truck frame while the truck frame is connected through a suspension system to a reference that moves along the track with constant velocity. The more complex model includes additional suspension elements between the axle bearings and truck frame. The effects of flange contact, wheel slip and Coulomb friction are described by nonlinear expressions. These results show the significant influence of flange contact on stability, and illustrate the effects of vehicle and track parameters such as rail adhesion, forward velocity, and wheel load on the forces and power dissipation at the wheel-rail interface.

Dynamic response analysis of quasi-rigid mechanical systems using kinematic influence coefficients

The general character of a mechanical system and its boundaries is discussed. Formalization of the analysis is accomplished by introduction of the concepts of the kinematic “influence coefficients” of velocity, acceleration, force, power inertia, etc., thereby making optimization through digital programming more feasible. It is possible to determine the response of mechanical systems to known energy, force, or power crossing the boundaries through the utilization of these influence coefficients. The effect of coulomb friction on the response is also shown to be predictable, a feature which enables the designer to better analyze or design mechanically constrained systems.