Stick-Slip Vibration Between Two Large Concentric Circular Discs in Rotational Contact With Multiple Point Loads

2003 ◽  
Vol 125 (4) ◽  
pp. 786-792
Author(s):  
M. Baleri ◽  
F. Sassani ◽  
P. L. Ko
Keyword(s):  
Robotic Manipulators ◽  
Integral Model ◽  
Mathematical Representation ◽  
Multiple Point ◽  
Rotating Platform ◽  
Stick Slip ◽  
System Parameters ◽  
Modeling Simulation ◽  
Contact Loads ◽  
Good Agreement

This paper presents a study of the stick-slip frictional phenomenon when large contact areas subjected to uneven contact loads, such as the rotating platform of excavators and large robotic manipulators, are involved. The objective of the investigation is to a gain better understanding of the phenomenon from experimental observations and to develop a mathematical representation that can be used for modeling, simulation and design purposes. A dynamic integral-model has been proposed and simulations have been carried out. The effects of various system parameters on the behavior of the system have been studied experimentally and analytically. The simulation results using the proposed integral-model are in good agreement with the experimental results. The latter also show that stick-slip vibrations can be influenced by the loading conditions.

Stick-Slip Vibration Between Two Large Concentric Circular Discs in Rotational Contact With Multiple Point Loads

2003 ◽  
Author(s):  
M. Baleri ◽  
F. Sassani ◽  
P. L. Ko
Keyword(s):  
Experimental Results ◽  
Integral Model ◽  
Mathematical Representation ◽  
Multiple Point ◽  
Stick Slip ◽  
System Parameters ◽  
Modeling Simulation ◽  
Contact Loads ◽  
Simulation Results ◽  
Good Agreement

This paper presents a study of the stick-slip frictional phenomenon when large contact areas subjected to uneven contact loads are involved. The objective of the investigation is to gain better understanding of the phenomenon from experimental observations and to develop a mathematical representation that can be used for modeling, simulation and design purposes. A dynamic integral-model has been proposed and simulations have been carried out. The effects of various system parameters on the behavior of the system have been studied experimentally and analytically. The simulation results using the proposed integral-model are in good agreement with the experimental results. The latter also show that stick-slip vibrations can be influenced by the loading conditions.

Vibration Analysis of a Brake Mechanism: Modeling, Simulation and Experimental Results

2005 ◽  
Author(s):  
Mihaela A. Dupac ◽  
P. K. Raju
Keyword(s):  
Vibration Analysis ◽  
Relative Velocity ◽  
System Behavior ◽  
Linear Dynamics ◽  
System Parameters ◽  
Modeling Simulation ◽  
Dynamic Friction Coefficient ◽  
Mechanism Modeling ◽  
Dynamics Method ◽  
Good Agreement

In this paper, an approach for identifying a model capable of representing the dynamics of the brake mechanism is presented. Experimentally acquired in-plane vibrations of the pad were analyzed using the non-linear dynamics method of Lyapunov exponents in order to characterize the system behavior. Friction-induced vibrations were then studied via the associated 4 DOF theoretical model of the brake system. Numerical simulations demonstrated that for a set of system parameters, a certain value of the slope of the mathematical characteristic between the dynamic friction coefficient and relative velocity, triggers the exponential growth of instability with an envelope in good agreement with that approximated from the experimental data. The results obtained from this study provide new insights into brake dynamics and the associated instability mechanisms.

scholarly journals The frequency of Kozai–Lidov disc oscillation driven giant outbursts in Be/X-ray binaries

2019 ◽  
Vol 489 (2) ◽  
pp. 1797-1804 ◽  
Author(s):  
Rebecca G Martin ◽  
Alessia Franchini
Keyword(s):  
Orbital Period ◽  
Time Scale ◽  
Orbital Plane ◽  
Material Flows ◽  
X Ray ◽  
System Parameters ◽  
Be Star ◽  
Chaotic Nature ◽  
X Ray Binaries ◽  
Good Agreement

ABSTRACT Giant outbursts of Be/X-ray binaries may occur when a Be-star disc undergoes strong eccentricity growth due to the Kozai–Lidov (KL) mechanism. The KL effect acts on a disc that is highly inclined to the binary orbital plane provided that the disc aspect ratio is sufficiently small. The eccentric disc overflows its Roche lobe and material flows from the Be star disc over to the companion neutron star causing X-ray activity. With N-body simulations and steady state decretion disc models we explore system parameters for which a disc in the Be/X-ray binary 4U 0115+634 is KL unstable and the resulting time-scale for the oscillations. We find good agreement between predictions of the model and the observed giant outburst time-scale provided that the disc is not completely destroyed by the outburst. This allows the outer disc to be replenished between outbursts and a sufficiently short KL oscillation time-scale. An initially eccentric disc has a shorter KL oscillation time-scale compared to an initially circular orbit disc. We suggest that the chaotic nature of the outbursts is caused by the sensitivity of the mechanism to the distribution of material within the disc. The outbursts continue provided that the Be star supplies material that is sufficiently misaligned to the binary orbital plane. We generalize our results to Be/X-ray binaries with varying orbital period and find that if the Be star disc is flared, it is more likely to be unstable to KL oscillations in a smaller orbital period binary, in agreement with observations.

scholarly journals CAD/CAM System for Additive Manufacturing with a Robust and Efficient Topology Optimization Algorithm Based on the Function Representation

2021 ◽  
Vol 11 (16) ◽  
pp. 7409
Author(s):  
Dmitry Popov ◽  
Yulia Kuzminova ◽  
Evgenii Maltsev ◽  
Stanislav Evlashin ◽  
Alexander Safonov ◽  
...  
Keyword(s):  
Topology Optimization ◽  
Additive Manufacturing ◽  
3D Modeling ◽  
Mechanical Tests ◽  
Simulation Data ◽  
Function Representation ◽  
Modeling Simulation ◽  
Cad Cam ◽  
Design Ideas ◽  
Good Agreement

Additive manufacturing erases the distance between design ideas and finished parts. However, designers must use several software tools to use these advantages. Moreover, these tools operate with different representations of geometry. This paper describes the architecture of a new CAD/CAM system that uses only the function representation of the geometry (FRep). It provides all widely used design operations and allows an engineer to employ robust and efficient topology optimization algorithms. The developed CAD/CAM system consists of 3D modeling, simulation, topology optimization, and direct manufacturing modules. We successfully printed designed parts and performed mechanical tests of printed parts. The results of tests show good agreement with simulation data. The system makes it possible to create structures with the desired properties in a fast and flexible way. The proposed approach significantly helps in designing additive manufacturing process and saves time for its users.

An Integral Model for Natural Convection From an Isothermal Right Circular Cone

2007 ◽  
Author(s):  
Chris J. Kobus ◽  
Yu-Hsien Wu
Keyword(s):  
Boundary Layer Thickness ◽  
Closed Form Solution ◽  
Approximate Model ◽  
Form Solution ◽  
Circular Cone ◽  
Integral Model ◽  
Numerical Techniques ◽  
System Parameters ◽  
Integral Technique ◽  
Individual System

An integral technique approximate model is developed in the current research to predict the convective heat transfer from a right circular cone. Much research has been done regarding stationary circular cones, but all of this prior research was achieved utilizing numerical techniques. As will be shown, the integral model predicts with almost the same precision as the former research. The advantage of the integral technique is its simplicity, culminating in a closed-form solution where the influence of individual system parameters and variables is directly observable. In addition, boundary layer thickness appreas explicitly in the analysis, which again tends to yield more insight at the expense of some accuracy.

Modeling and Identification of a Class of Servomechanism Systems With Stick-Slip Friction

1988 ◽  
Vol 110 (3) ◽  
pp. 324-328 ◽  
Author(s):  
Ka C. Cheok ◽  
Hongxing Hu ◽  
Nan K. Loh
Keyword(s):  
Nonlinear Optimization ◽  
Optimization Problem ◽  
Optimization Procedure ◽  
Simplex Algorithm ◽  
Identification Algorithm ◽  
Stick Slip ◽  
Process Identification ◽  
Nonlinear Optimization Problem ◽  
System Parameters ◽  
Input Signals

This paper describes a technique for modeling and identifying a class of nonlinear servomechanism systems with stick-slip friction. The physics of the stick-slip friction is considered in modeling the process. Identification of the system parameters is formulated as a nonlinear optimization problem. A modified simplex algorithm is proposed as the optimization procedure. The difficulties encountered in choosing identification algorithm and input signals for the problem are discussed. A simulation example of a servomotor system is provided.

The Elastica With End-Load Flip-Over

1988 ◽  
Vol 55 (4) ◽  
pp. 845-848 ◽  
Author(s):  
J. F. Wilson ◽  
J. M. Snyder
Keyword(s):  
Cantilever Beam ◽  
Abrupt Change ◽  
Robotic Manipulators ◽  
Finite Deformations ◽  
Follower Load ◽  
System Parameters ◽  
Small Increment ◽  
Elastic Curves ◽  
Manipulator Arm

A high flexure manipulator arm is modeled as an elastic cantilever beam with a tip payload and an eccentric tip follower load that drives the arm. Shapes of the resulting elastic curves for finite deformations (the elastica) are calculated in terms of nondimensional system parameters. For critical combinations of these parameters, a small increment in the driving follower load causes an abrupt change in the shape of the elastica. The abrupt change in tip angle is typically of the order of π radians. These results are applicable to the design of high flexure robotic manipulators.

scholarly journals Transitions and singularities during slip motion of rigid bodies

2018 ◽  
Vol 29 (5) ◽  
pp. 778-804 ◽  
Author(s):  
P. L. VÁRKONYI
Keyword(s):  
Coulomb Friction ◽  
Rigid Bodies ◽  
Two Dimensions ◽  
Multiple Point ◽  
Point Contacts ◽  
Stick Slip ◽  
Unilateral Contacts ◽  
Rigid Rod ◽  
Body Theory ◽  
Slip Motion

The dynamics of moving solids with unilateral contacts are often modelled by assuming rigidity, point contacts, and Coulomb friction. The canonical example of a rigid rod with one endpoint slipping in two dimensions along a fixed surface (sometimes referred to as Painlevé rod) has been investigated thoroughly by many authors. The generic transitions of that system include three classical transitions (slip-stick, slip reversal, and liftoff) as well as a singularity called dynamic jamming, i.e., convergence to a codimension 2 manifold in state space, where rigid body theory breaks down. The goal of this paper is to identify similar singularities arising in systems with multiple point contacts, and in a broader setting to make initial steps towards a comprehensive list of generic transitions from slip motion to other types of dynamics. We show that – in addition to the classical transitions – dynamic jamming remains a generic phenomenon. We also find new forms of singularity and solution indeterminacy, as well as generic routes from sliding to self-excited microscopic or macroscopic oscillations.

Buoyancy-driven interactions of viscous drops with deforming interfaces

2001 ◽  
Vol 446 ◽  
pp. 253-269 ◽  
Author(s):  
JOSEPH KUSHNER ◽  
MICHAEL A. ROTHER ◽  
ROBERT H. DAVIS
Keyword(s):  
Castor Oil ◽  
Viscosity Ratio ◽  
Bond Number ◽  
Glycerol Water ◽  
System Parameters ◽  
Viscous Drops ◽  
Water Drops ◽  
Pass Through ◽  
Theoretical Results ◽  
Good Agreement

Experiments were conducted on the interactions of two different-sized deformable drops moving due to gravity in an immiscible viscous fluid at low Reynolds number. As the drops come close to each other, several interactions are possible: (i) separation of the drops, (ii) capture of the smaller drop behind the larger drop, (iii) breakup of the smaller drop into two or more drops, and (iv) pass-through of one drop through the other, with possible cycle interaction or leap-frogging. The interactions depend on several system parameters, including the drop-to-medium viscosity ratio, the radius ratio of the two drops, the initial horizontal offset of the two drops at large vertical separation, and the gravitational Bond number (which represents the ratio of buoyant forces to interfacial tension forces for the larger drop and describes how much the drops will deform). Experimental analysis was conducted by videotaping trajectories of glycerol–water drops of various compositions falling in castor oil. The results show good agreement with available theoretical results, both for interaction maps and individual trajectories. The results also provide data beyond the present limitations of theoretical algorithms and reveal the new pass-through phenomenon.

scholarly journals Parallel Manipulation Based on Stick-Slip Motion of Vibrating Platform

Robotics ◽  
2020 ◽  
Vol 9 (4) ◽  
pp. 86
Author(s):  
Mohammad Mayyas
Keyword(s):  
Material Handling ◽  
Amplitude Response ◽  
Stick Slip ◽  
Modeling And Analysis ◽  
System Parameters ◽  
Input Force ◽  
Industrial Material ◽  
Vibrating Platform ◽  
Stick Slip Motion ◽  
Slip Motion

The majority of the industrial material handling mechanisms used in the manipulation or assembly of mesoscale objects are slow and require precision programming and tooling, mainly because they are based on sequential robotic pick-n-place operations. This paper presents problem formation, modeling, and analysis of a sensorless parallel manipulation technique for mimicking real-systems that transfer mesoscale objects based on the vibration of inline-feeder machines. Unlike common stick-slip models that utilize a “mass-on-moving-belt” and avoid totality of the motion, the research obtains differential equations in order to describe the combined physics of stick-slip dynamics of an object traveling along an oscillating platform under smooth and dry friction conditions. The nonlinear dynamics are solved numerically to explain the effect of system parameters on the stick-slip motion. The research provides empirical models based on frequency-analysis identification to describe the total linear speed of an object to an input force. The results are illustrated and tested by time–response, phase plots, and amplitude response diagrams, which compare very favorably with results obtained by numerical simulation of the equation of motion, and this suggests that the vibration of the platform is independent of stick-slip motion when the mass of the object being transported is small relative to the mass of the system.

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