Stick-Slip, Imposition-Removal of Constraints and the Spinning Ball Problem

2000 ◽  
Vol 67 (4) ◽  
pp. 720-726
Author(s):  
S. Djerassi
Keyword(s):  
Computer Program ◽  
Experimental Results ◽  
Stick Slip ◽  
Elastic Bodies ◽  
Cyclic Motion ◽  
Ball Problem

It has been observed that balls pressed between elastic bodies spin when subjected to linear, cyclic motion. This paper proposes an explanation to this phenomenon, based upon the stick-slip theory. To this end, a modified, vectorial formulation of the stick-slip theory is presented. The formulation is applied to a model comprising a ball pressed between pairs of springs and dampers. A computer program based on this formulation is used to predict the resulting motion. Predictions are shown to agree with experimental results. [S0021-8936(01)00701-2]

The effects of grooved rubber blocks on stick–slip and wear behaviours

2018 ◽  
Vol 233 (11) ◽  
pp. 2939-2954 ◽  
Author(s):  
Xiao Cui Wang ◽  
Ji Liang Mo ◽  
Huajiang Ouyang ◽  
Xiao Dong Lu ◽  
Bo Huang ◽  
...  
Keyword(s):  
Relative Velocity ◽  
Surface Modifications ◽  
Experimental Results ◽  
Brake Disc ◽  
Experimental Setup ◽  
Brake Pad ◽  
Stick Slip ◽  
Elastic Rubber ◽  
Disc Configuration ◽  
Rubber Block

This work presents an experimental and theoretical combined study of the effects of the elastic rubber blocks with different surface modifications on the friction-induced stick–slip oscillation and wear of a brake pad sample in sliding contact with an automobile brake disc. The experiments are conducted on the customized experimental setup in a pad-on-disc configuration. The experimental results show that (1) the friction system with the plain rubber block still exhibits visible stick–slip oscillation, but the intensity of the stick–slip oscillation is reduced to a certain degree compared with the Original friction system (without rubber block); (2) the grooved rubber blocks display a better ability to reduce the stick–slip oscillation compared with the plain rubber block; (3) the rubber blocks with a vertical groove (perpendicular to the relative velocity) or a horizontal groove (parallel to the relative velocity) or a diagonal groove (45° inclined to the relative velocity) on their surfaces can suppress the stick–slip oscillation more effectively with various degrees of success. The experimental results also reveal the varying effects of the different rubber blocks on wear. To explain the experimental phenomenon reasonably, a theoretical analysis is conducted to investigate the effects of different rubber blocks on both stick–slip oscillation and wear using ABAQUS. Furthermore, the analysis of the contact pressure on the pad interfaces and the deformation of the rubber blocks are studied to provide a possible explanation of the experimental results.

Prediction of the Phase Behavior Generated by the Enriched-Gas-Drive Process

1965 ◽  
Vol 5 (02) ◽  
pp. 160-166 ◽  
Author(s):  
A.M. Rowe ◽  
I.H. Silberberg
Keyword(s):  
Computer Program ◽  
Phase Behavior ◽  
Oil Recovery ◽  
Miscible Displacement ◽  
Phase Changes ◽  
Experimental Results ◽  
High Concentration ◽  
Gas Drive ◽  
Non Equilibrium ◽  
Vapor Liquid

Abstract A computer program was written to predict the phase behavior generated by the enriched-gas-drive process. This program is based, in part, on a new concept of convergence pressure, which is then used to select vapor-liquid equilibrium ratios (K-factors) for performing a series of flash calculations. The results of these calculations are the equilibrium vapor and liquid phase compositions which define the phase envelopes. The program was used to predict phase envelopes for 11 different hydrocarbon systems on which published experimental data were available. The predicted and experimental results compare favorably. Introduction The reservoir engineer is frequently faced with the problem of predicting what will happen if gas is injected into a reservoir. One aspect of this general problem is predicting the phase changes that will occur when a non-equilibrium gas displaces a reservoir fluid. In particular, a "dry" gas, upon displacing a volatile oil will pick up intermediate components from the oil. On the other hand, a "wet" gas, containing a high concentration of intermediates, will lose some of these components to a relatively low-gravity, non-equilibrium crude. It is this latter process, occurring in the enriched-gas displacement, which is treated in this paper. In the past, these phase changes have been determined experimentally and the results incorporated into various modifications of the Buckley-Leverett analysis. Such experimental work is time consuming, and the results are sensitive to numerous experimental errors. With the wide availability of high-speed digital computing equipment and numerous correlations pertaining to the vapor-liquid equilibria of hydrocarbon systems, it is now practical to calculate such phase behavior. This paper describes a computer program for performing these calculations. THE ENRICHED GAS DISPLACEMENT PROCESS Experimental results have shown that oil recovery can be significantly increased by enriching the displacing gas with intermediate hydrocarbon components. The essential features of the phase behavior generated by this enriched-gas-drive process are commonly illustrated with ternary diagrams such as Fig. 1. In this figure, Gas D, which contains a high concentration of intermediate hydrocarbons with respect to the undersaturated Crude A, is injected into the reservoir. When D contacts A, gas goes into solution until the oil becomes saturated (Point. B). Further contacting of Gas D and saturated Oil B results in a Mixture C which separates into Vapor Y(c) and Liquid X(c). Liquid X(c) is contacted by additional Gas D, resulting in Mixture E which separates into Vapor Y(e) and Liquid X(e). Repeated contacts of the liquid by the injected gas will eventually result in Liquid X(d) of maximum enrichment existing in equilibrium with Gas Y(d). The equilibrium tie-line X(d) Y(d), when extended, passes through the Point D representing the enriched injection gas. For systems of more than three components, the predicted equilibrium states are dependent upon not only reservoir temperature and pressure, but also the compositions of the crude oil and injected gas. If the gas is sufficiently enriched, a miscible displacement is generated. Line is tangent to the phase envelope at the critical point (Point Z) and represents the limiting slope of the tie-lines as the critical state is approached. Point I therefore represents the minimum enrichment of injection gas required to generate a miscible displacement. Point G represents the minimum enrichment required for initial miscibility of the injection gas with Crude A.Attra has presented a method to be used for prediction of oil recovery by the enriched gas displacement process. To develop the phase behavior data needed, he designed the experimental procedure described in the following quotation from his paper SPEJ P. 160ˆ

Zur Bestimmung der optischen Konstanten stark absorbierender Substanzen mit kleinen Probenabmessungen

1981 ◽  
Vol 36 (6) ◽  
pp. 662-664 ◽  
Author(s):  
Alexander v. Petersenn ◽  
Hans-Uwe Schuster
Keyword(s):  
Computer Program ◽  
Optical Constants ◽  
Experimental Results ◽  
Experimental Arrangement ◽  
Small Samples ◽  
Absolute Value ◽  
The Absolute

Abstract To determine the optical constants of small samples a method described by Avery is suitable insofar as it is not necessary to know the absolute value of the reflected intensity of light. The problem of beam-drift during the rotation of the polarizer is solved with a modified experimental arrangement. A computer program for the evaluation of experimental results is outlined. The optical constants of gold as taken from a crystal 0.2 mm in diameter have been measured to check the accuracy of the system

scholarly journals Experimental investigation of a single-degree-of-freedom system with Coulomb friction

2020 ◽  
Vol 99 (3) ◽  
pp. 1781-1799
Author(s):  
Luca Marino ◽  
Alice Cicirello
Keyword(s):  
Experimental Investigation ◽  
Degree Of Freedom ◽  
Experimental Results ◽  
Systematic Observation ◽  
Stick Slip ◽  
Friction Forces ◽  
Single Degree Of Freedom ◽  
Sdof System ◽  
Single Degree ◽  
Set Up

AbstractThis paper presents an experimental investigation of the dynamic behaviour of a single-degree-of-freedom (SDoF) system with a metal-to-metal contact under harmonic base or joined base-wall excitation. The experimental results are compared with those yielded by mathematical models based on a SDoF system with Coulomb damping. While previous experiments on friction-damped systems focused on the characterisation of the friction force, the proposed approach investigates the steady response of a SDoF system when different exciting frequencies and friction forces are applied. The experimental set-up consists of a single-storey building, where harmonic excitation is imposed on a base plate and a friction contact is achieved between a steel top plate and a brass disc. The experimental results are expressed in terms of displacement transmissibility, phase angle and top plate motion in the time and frequency domains. Both continuous and stick-slip motions are investigated. The main results achieved in this paper are: (1) the development of an experimental set-up capable of reproducing friction damping effects on a harmonically excited SDoF system; (2) the validation of the analytical model introduced by Marino et al. (Nonlinear Dyn, 2019. https://doi.org/10.1007/s11071-019-04983-x) and, particularly, the inversion of the transmissibility curves in the joined base-wall motion case; (3) the systematic observation of stick-slip phenomena and their validation with numerical results.

Experimental Investigation of the Stick-Slip Phenomena of the Drill Pipe

2015 ◽  
Author(s):  
Tokihiro Katsui ◽  
Yoshitomo Mogi ◽  
Tomoya Inoue ◽  
Chang-Kyu Rheem ◽  
Miki Y. Matsuo
Keyword(s):  
Drill Pipe ◽  
Small Time ◽  
Numerical Results ◽  
Experimental Results ◽  
Frictional Torque ◽  
Drill Bit ◽  
Stick Slip ◽  
Model Experiments ◽  
Pipe Model ◽  
Weight On Bit

The stick-slip is one of the critical problems for the scientific drilling, because it causes a crushing of the sampled layer. The present study investigates the characteristics of stick-slip phenomena of the drill pipe with the model experiments and numerical methods. The model experiments are carried out using a 1m length drill pipe model made with the Teflon. The angular velocity at the top and the bottom of the pipe are measured with the gyro sensor on some conditions of rotating speed at the pipe top and the weight on bit (load at the pipe bottom). The numerical simulations are also carried out to reproduce the stick-slip phenomena of the model experiments. The stick-slip is a kind of torsional vibration which is governed by the convection equation. By considering the boundary condition at the top and bottom of the pipe, we can obtain a neutral delayed differential equation (NDDE). The solutions of the NDDE is depend on not the initial value but the initial history of the solution, because NDDE contains a delayed function term. Therefore, it should be solved carefully to avoid the numerical error. The NDDE is solved with the 4th order Runge-Kutta scheme with very small time increment until the truncation error could be neglected. And also, we have found out that the effect of the initial history on the solution become to be very small after a certain period of time. The experimental results are compared with the numerical results under the same rotating condition. The experimental results of the stick-slip suggest that the period of the slip is mainly depend on the rotation speed at the pipe top and the magnitude of the slip is mainly depend on the weight on bit. Those characteristics of the stick-slip such as the period or the magnitude of slip are also obtained with the numerical calculations. However, in order to obtain an acceptable numerical results of NDDE, we have to adjust the frictional torque acting on the drill bit. Though, the frictional torque model was determined by reference to the measured torque at the top of the drill pipe model in the present study, it is desired to be improved. Therefore, the physical model of the frictional torque on the drill bit should be evaluated much carefully for the precise estimation of the stick slip in the future.

Prediction of Bend Allowance and Springback in Air Bending

2006 ◽  
Vol 129 (2) ◽  
pp. 342-351 ◽  
Author(s):  
Hyunok Kim ◽  
Ninad Nargundkar ◽  
Taylan Altan
Keyword(s):  
Computer Program ◽  
Analytical Model ◽  
Elastic Recovery ◽  
Experimental Results ◽  
Air Bending ◽  
Acceptable Accuracy ◽  
Geometric Tolerances ◽  
Plastic Elongation ◽  
Bending Process ◽  
User Friendly

In the fabrication industry, one of the critical challenges is to maintain close geometric tolerances in finished products, particularly in the air bending process. In many cases, this problem is related to springback and plastic elongation/compression of the sheet, as it undergoes deformation in bending. Springback refers to the elastic recovery of the bent sheet after unloading, whereas bend allowance refers to the elongation of the sheet during bending. Both factors, if not predicted properly, may lead to dimensional inaccuracies in the finished product and cause difficulties in the assembly. Therefore, it is essential to predict springback and bend allowance in order to obtain the final desired geometry. A new analytical model was developed to predict springback and bend allowance simultaneously in air bending, and a user-friendly computer program, BEND (Version 3.0), was developed. Results obtained from the BEND program were compared to other analytical predictions and experimental results available in the literature. It was concluded that the proposed analytical model and the computer program predicted bend allowance and springback within acceptable accuracy.

The Application of Finite Element Techniques to the Analysis of an Automobile Structure: First Paper: Static Analysis of an Automobile Chassis Frame

1970 ◽  
Vol 185 (1) ◽  
pp. 665-674 ◽  
Author(s):  
R. Ali ◽  
J. L. Hedges ◽  
B. Mills
Keyword(s):  
Finite Element ◽  
Computer Program ◽  
Static Analysis ◽  
Cross Sections ◽  
Experimental Results ◽  
Finite Element Technique ◽  
Beam Elements ◽  
Manufacturing Tolerances ◽  
Element Technique

The finite element technique has been used for the static analysis of a chassis structure. A computer program was developed to predict static deflections under bending and torsion loads. The program is quite general, but its use has been restricted to structures consisting of beam elements only. The effects of shear deflections and tapered beams and manufacturing tolerances of cross sections are also considered. Predictions of static deflections are compared with experimental results.

Numerical Simulation of Mould Filling in Rheo-Diecasting Process of Semi-Solid Magnesium Alloys

2006 ◽  
Vol 116-117 ◽  
pp. 554-557 ◽  
Author(s):  
Shu Sen Wu ◽  
Jun Wen Zhao ◽  
Li Wan ◽  
Jirong Luo
Keyword(s):  
Numerical Simulation ◽  
Magnesium Alloy ◽  
Computer Program ◽  
Magnesium Alloys ◽  
Experimental Results ◽  
Air Entrapment ◽  
Mould Filling ◽  
Slurry Flows ◽  
Semi Solid ◽  
Numeral Simulation

The mould-filling behavior of rheo-diecasting of semi-solid magnesium alloy and diecasting of liquid magnesium alloy has been simulated with the computer program of numerical simulation developed by the authors. Results show that, under the same diecasting conditions, the filling behavior of rheo-diecasting of semi-solid metals is similar to the liquid diecasting, but mould filling of semi-solid slurry is steadier, and the slurry flows into the mould in a state similar to lamellar flow. The air entrapment in semi-solid process is much smaller than that of liquid diecasting, and the castings made with semi-solid rheo-diecasting excel those with liquid diecasting in quality. Experimental results are in accord with the results of numeral simulation.

The Influence of Oil Lubricated Journal Bearings on the Dynamics of Rotating Systems

1976 ◽  
Vol 190 (1) ◽  
pp. 627-633 ◽  
Author(s):  
H. McCallion ◽  
D. R. Wales
Keyword(s):  
Boundary Conditions ◽  
Computer Program ◽  
Translational Motion ◽  
Journal Bearings ◽  
Experimental Results ◽  
Oil Film ◽  
Rotating Systems ◽  
Film Boundary ◽  
Good Agreement

SYNOPSIS A computer program representing a shaft and rotor whirling in bearings which allows for realistic oil film boundary conditions and non-circular bearing profiles has been developed. It gave good agreement with experimental results published by Brown and France. With the aim of increasing understanding of the influence of bearing profile on system instability, the program calculates the timewise variation of the energy in translational motion supplied to the rotor by oil film forces. One case is illustrated.

Nanoscale Friction Dynamic Modeling

2009 ◽  
Vol 131 (6) ◽  
Author(s):  
Fakhreddine Landolsi ◽  
Fathi H. Ghorbel ◽  
Jun Lou ◽  
Hao Lu ◽  
Yuekai Sun
Keyword(s):  
Friction Model ◽  
Experimental Results ◽  
Atomic Scale ◽  
Model Parameters ◽  
Large Set ◽  
Asperity Contact ◽  
State Variables ◽  
Stick Slip ◽  
Proposed Model ◽  
Nanoscale Friction

Friction and system models are fundamentally coupled. In fact, the success of models in predicting experimental results depends highly on the modeling of friction. This is true at the atomic scale where the nanoscale friction depends on a large set of parameters. This paper presents a novel nanoscale friction model based on the bristle interpretation of single asperity contact. This interpretation is adopted after a review of dynamic friction models representing stick-slip motion in macrotribology literature. The proposed model uses state variables and introduces a generalized bristle deflection. Jumping mechanisms are implemented in order to take into account the instantaneous jumps observed during 2D stick-slip phenomena. The model is dynamic and Lipchitz, which makes it suitable for future control implementation. Friction force microscope scans of a muscovite mica sample were conducted in order to determine numerical values of the different model parameters. The simulated and experimental results are then compared in order to show the efficacy of the proposed model.

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