Influence Of Dry Friction Research Articles

FEATURES OF VIBRATION DAMPERS APPLICATION IN THE DESIGN OF VIBRATION-RESISTANT METAL CUTTING TOOLS

Dry and viscous friction is used as a damper of oscillation energy in the construction of metal-cutting tools. A mathematical model of a two-mass oscillatory scheme of the insert of an assembled milling cutter was developed and studied, one of the masses of which models the clamped part of the insert - a press connection with dry friction, and the other - the cantilever part, which is subject to self-oscillations that are possible in the process of metal cutting. The influence of dry friction in the press joint of the insert on the amplitude of resonant oscillations of the cutter and the part was analyzed. The possibility of reducing the magnitude of the cutter's self-oscillations is demonstrated by selecting the most suitable parameters for the press connection of inserts with the body of the assembled milling cutter. The influence of internal viscous friction in materials with a high level of energy damping on the amplitude of self-oscillations of the cutter was evaluated and the possibility of their use in the design of a vibration-resistant metal-cutting tool was considered.

Influence of Dry Friction on the Dynamics of Cantilevered Pipes Conveying Fluid

A cantilevered pipe conveying fluid can lose stability via flutter when the flow velocity becomes sufficiently high. In this paper, a dry friction restraint is introduced for the first time, to evaluate the possibility of improving the stability of cantilevered pipes conveying fluid. First, a dynamical model of the cantilevered pipe system with dry friction is established based on the generalized Hamilton’s principle. Then the Galerkin method is utilized to discretize the model of the pipe and to obtain the nonlinear dynamic responses of the pipe. Finally, by changing the values of the friction force and the installation position of the dry friction restraint, the effect of dry friction parameters on the flutter instability of the pipe is evaluated. The results show that the critical flow velocity of the pipe increases with the increment of the friction force. Installing a dry friction restraint near the middle of the pipe can significantly improve the stability of the pipe system. The vibration of the pipe can also be suppressed to some extent by setting reasonable dry friction parameters.

Influence of dry friction on the wear behavior of X52 steel—experimental study and simulation using response surfaces method

Friction and wear phenomena alter the behavior of the material surface, where certain relevant parameters which characterize the surface are influenced. Therefore, the objective of this work is to identify the parameters most influencing the friction coefficient (f), the wear rate (Ws), and the volume parameters (Vmc and Vvv) during the friction test. The friction tests were carried out by adopting the methodology of 23 complete planes with three factors (D, V, and Py), at two levels each. The results show a decrease in the wear rate when all three factors are at their highest level and a decrease in the friction coefficient when using minimum load on speed long distances. In addition, the mathematical models developed allow to reveal a correlation between the test parameters (D, V, and Py), and the responses studied (f, Ws) in their study field. Moreover, the volume parameters Vmc and Vvv were evaluated during the tests, and the morphology of the worn surface shows that the friction under a load of 1 N leads to the predominance of an abrasive wear mechanism, while a load of 10 N promotes an adhesive wear mechanism.

Challenging an experimental nonlinear modal analysis method with a new strongly friction-damped structure

In this work, we show that a recently proposed method for experimental nonlinear modal analysis based on the extended periodic motion concept is well suited to extract modal properties for strongly nonlinear systems (i.e. in the presence of large frequency shifts, high and nonlinear damping, changes of the mode shape, and higher harmonics). To this end, we design a new test rig that exhibits a large extent of friction-induced damping (modal damping ratio up to 15%) and frequency shift by 36% (considered the first bending mode). The specimen, called RubBeR, is a cantilevered beam under the influence of dry friction, ranging from full stick to mainly sliding. With the specimen's design, the measurements are well repeatable for a system subjected to dry frictional force. Then, we apply the method to the specimen and show that single-point excitation is sufficient to track the modal properties even though the deflection shape changes with amplitude. Computed frequency responses using a single nonlinear-modal oscillator with the identified modal properties agree well with measured reference curves of different excitation levels, indicating the modal properties' significance and accuracy.

Experimental and numerical assessment of the seismic response of steel structures with clutched inerters

Supplemental rotational inertia devices provide an efficient means of suppressing ground-induced vibrations over a large range of structural periods. The beneficial effects of the inerter can be further enhanced by coupling it with a clutch system that prevents it from driving the structural response and ensures that its supplemental rotational inertia is only employed to resist the motion. In this paper, we examine the behaviour of single-degree-of-freedom and multi-degree-of-freedom structures equipped with twin inerter-clutch devices subjected to strong ground-motion. The influence of the clutch stiffness, gears play, viscous damping and dry friction, on the non-linear dynamics of the system are explored first, by analysing the stable periodic solutions of a structure with inerters under harmonic-sweeps. We demonstrate that, for the range of parameters typically expected in earthquake engineering practice, the influence of dry-friction and clutch damping are limited, although the clutch stiffness and gear play may need to be accounted for when large inertances or defective clutches are considered. Based on these findings, we propose a simplified numerical modelling strategy suitable for implementation in conventional Finite Element simulations. Small scale experiments on bare elastic structures as well as structures equipped with 3D-printed inerter and inerter-clutch twins are presented and employed for concept demonstration and for the validation of the numerical model proposed. Finally, a series of studies on detailed numerical models of multi-storey steel frames under idealized and real pulse-like ground-motions are used to demonstrate the vibration absorbing capabilities brought about by the twin inerter-clutch system and to highlight practical aspects related to their structural implementation.

Viscoelastic body colliding against a rigid wall with and without dry friction effects

The impact of a body against a rigid wall is studied. The body consists of a rigid block and a viscoelastic rod described by the distributed-order fractional model and in particular its solid-like and fluid-like special cases. Translatory motion of a body is studied in two cases: without and with the influence of dry friction. When present, dry friction is modeled by the Coulomb friction law. The problem is treated analytically by the use of the Laplace transform method and solutions are obtained in a convolution form.

On a mechanical lens

In this paper, we consider the dynamics of a heavy homogeneous ball moving under the influence of dry friction on a fixed horizontal plane. We assume the ball to slide without rolling. We demonstrate that the plane may be divided into two regions, each characterized by a distinct coefficient of friction, so that balls with equal initial linear and angular velocity will converge upon the same point from different initial locations along a certain segment. We construct the boundary between the two regions explicitly and discuss possible applications to real physical systems.

Twin Shaft Rotor System Vibration Damping Experimental Investigation

The influence of dry friction damping on twin shaft model test rig vibration experimental investigation is presented. Experimental investigation method is devised and tested at the work. Dry and Coulomb friction damper is developed. The efficiency of damping is evaluated quantitatively via rotor shaft vibration displacements amplitude determining.

О механической линзе

Abstract In this paper, we consider the dynamics of a heavy homogeneous ball moving under the influence of dry friction on a fixed horizontal plane. We assume the ball to slide without rolling. We demonstrate that the plane may be divided into two regions, each characterized by a distinct coefficient of friction, so that balls with equal initial linear and angular velocity will converge upon the same point from different initial locations along a certain segment. We construct the boundary between the two regions explicitly and discuss possible applications to real physical systems.

Analysis of dry friction hysteresis in a cable under uniform bending

A cable is considered as a system of helical wires and a core with distributed dry friction forces at their interfaces. Deformations of the cable subjected to a uniform bending are analyzed. It is shown that there is a critical bending curvature when a slip at the wire-core interface occurs. It originates at the neutral axis of the cross section of the cable and then spreads symmetrically over the cross section with the increase of bending. The effect of slippage on the cable stiffness is investigated. This model is also used to analyze a cable under the quasi-static cyclic bending. Explicit expression for the hysteretic losses per cycle of bending is derived. Numerical examples are given to show the influence of dry friction and helix angle on the bending stiffness and hysteretic losses in the cable.

A Contribution on Forced Periodic Oscillations With Piecewise Linear and Constant Damping

In control system design and precision mechanics it is important to know the precise motion of excited or self-excited vibration under the influence of dry friction. In this paper, the motion of such a nonlinear oscillator is analyzed with the aid of pointmappings. As an example, a nonlinear function of damping dependent on the velocity can be approximated by piecewise linear functions. For this example, the stability of periodic solutions of the type q (t+T/2) = −q(t), (T = period, t = time), is discussed. The case of “critical stability” leads to potential points of bifurcation (branching-off solutions) which are investigated. Calculated examples are compared with experiments.

Dynamic Accuracy of Hybrid Profiling Mechanisms in Cam Manufacturing

Dynamic accuracy in cam production using hybrid profiling mechanisms in turning with a single point cutting tool is investigated. A profiling mechanism consisting of a four-way, critical-centered spool valve and a symmetrical volume power cylinder with a fixed piston is mathematically modeled and simulated on a hybrid computer to study its dynamic behavior. The model includes the dynamic cutting forces and their interaction with the velocity response of the mechanism, the nonlinear dry friction in the copying slide, and the dynamic behavior of the copying slide, control valve, and the stylus. The kinematic displacement of the stylus in time domain is formulated from the cam profile characteristic and is used as the input function for the simulation. The response of the mechanism to this input describes the shape of the manufactured cam profile in time domain. Based on the results of this investigation, it can be concluded that for a minimum manufacturing error in cam profiling, hybrid profiling mechanisms should be designed with low stylus inertia and high stylus stiffness. Operating a profiling mechanism with high supply pressure, low exhaust pressure, smaller depth of cut, and low angular velcoity of master cam also give high dynamic accuracy. The influence of dry friction in the copying slide and the copy-slide angle γ on the manufacturing error is also presented. Plots are also developed to be used as a guide in the design and operation of these hybrid profiling mechanisms.

Transient Rolling Contact Phenomena

Two cylinders of identical purely elastic materials are pressed together with parallel axes under the action of a normal force so that a contact strip forms. The cylinders are then shifted with respect to each other, which, under the influence of dry friction, gives rise to Cattaneo's (2) traction distribution with two slip areas. Subsequently they are rolled under the influence of a constant couple, reaching eventually Carter's (3) steady state with one slip area. The question arises how the former traction distribution passes into the latter as a function of time. It is answered in the framework of a more general rolling contact problem. The problem is solved numerically under the assumption of vanishing inertial effects, and results are presented. In the problem mentioned above it is found that Carter's (3) distribution is virtually attained when one to two contact widths have been traversed. Presented at the 25th ASLE Annual Meeting in Chicago, May 4–8, 1970

The influence of dry friction and mechanical parameters on the stability and accuracy of an hydraulic copying system

In order to improve the accuracy of an hydraulic copying system, the hydraulic stiffness must be increased and dry friction decreased. Both hydraulic stiffness and dry friction have important influences on the stability of the system, and so have several mechanical parameters. As a pure mathematical study of the influence of the non-linear dry friction is rather difficult, the behaviour of the system will be simulated on an analogue computer. This simulation will provide useful data about the stability criterion and the optimalization of the system.