SOME DISCONTINUOUS BIFURCATIONS IN A TWO-BLOCK STICK–SLIP SYSTEM

2001 ◽  
Vol 248 (4) ◽  
pp. 653-669 ◽  
Author(s):  
U. GALVANETTO
Keyword(s):  
Slip System ◽  
Stick Slip ◽  
Discontinuous Bifurcations

Discontinuous Bifurcations in Stick-Slip Mechanical Systems

2001 ◽  
Author(s):  
Ugo Galvanetto
Keyword(s):  
Dynamical Systems ◽  
Dry Friction ◽  
Scientific Literature ◽  
Mechanical Systems ◽  
Stick Slip ◽  
Floquet Multipliers ◽  
Discontinuous Bifurcations ◽  
Active Research ◽  
Grazing Bifurcations

Abstract Non-smooth dynamical systems exhibit continuous and discontinuous bifurcations. Continuous bifurcations are well understood and described in many textbooks, whereas discontinuous bifurcations are still the object of active research. Grazing bifurcations, C-bifurcations and other types of bifurcations characterised by jumps of the relevant Floquet multipliers have been described in the scientific literature. This paper deals with two discontinuous bifurcations found in mechanical systems affected by dry friction.

Stick-slip Whirl Interaction in Drillstring Dynamics

2002 ◽  
Vol 124 (2) ◽  
pp. 209-220 ◽  
Author(s):  
R. I. Leine ◽  
D. H. van Campen ◽  
W. J. G. Keultjes
Keyword(s):  
Bifurcation Theory ◽  
Drilling Mud ◽  
Stick Slip ◽  
Fluid Forces ◽  
Drilling Rig ◽  
Whirling Motion ◽  
Discontinuous Bifurcation ◽  
Discontinuous Model ◽  
Discontinuous Bifurcations ◽  
Stick Slip Motion

This paper attempts to explain the complicated behavior of oilwell drillstring motion when both torsional stick-slip and lateral whirl vibration are involved. It is demonstrated that the observed phenomena in experimental drillstring data could be due to the fluid forces of the drilling mud. A Stick-slip Whirl Model is presented which consists of a submodel for the whirling motion and a submodel for the stick-slip motion, both as simple as possible. The Stick-slip Whirl Model is a simplification of a drillstring confined in a borehole wall with drilling mud. The model is as simple as possible to expose only the basic phenomena but is discontinuous. Bifurcation diagrams of this discontinuous model for varying rotation speeds reveal discontinuous bifurcations. The disappearance of stick-slip vibration when whirl vibration appears is explained by bifurcation theory. The numerical results are compared with the experimental data from a full-scale drilling rig.

Bifurcational Dynamics of a Two-Dimensional Stick-Slip System

2012 ◽  
Vol 20 (3) ◽  
pp. 301-322 ◽  
Author(s):  
Grzegorz Kudra ◽  
Jan Awrejcewicz
Keyword(s):  
Slip System ◽  
Two Dimensional ◽  
Stick Slip

In situ Tensile Experiments at Low Temperatures on Niobium Single Crystals by H.V.E.M.

1975 ◽  
Vol 33 ◽  
pp. 58-59
Author(s):  
F. H. Louchet ◽  
L. P. Kubin
Keyword(s):  
Electron Microscope ◽  
Transition Temperature ◽  
Low Temperature ◽  
Slip System ◽  
Low Temperatures ◽  
Tensile Axis ◽  
Image Intensifier ◽  
Screw Dislocations ◽  
Source Operation

Experiments have been carried out on the 3 MeV electron microscope in Toulouse. The low temperature straining holder has been previously described Images given by an image intensifier are recorded on magnetic tape.The microtensile niobium samples are cut in a plane with the two operative slip directions [111] and lying in the foil plane. The tensile axis is near [011].Our results concern:- The transition temperature of niobium near 220 K: at this temperature and below an increasing difference appears between the mobilities of the screw and edge portions of dislocations loops. Source operation and interactions between screw dislocations of different slip system have been recorded.

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