Stick-slip zone

Figure 3. Geotherm and the Earth crust boundaries (1) - stick-slip zone, (2) - the Moho states...

Zone 2A - It is characterized by brittle zone with rougher surface compared to PP. Parabolic ridges are seen in the micrographs at farther edge. These ridges show the stick slip zone here the crack propagation is slowed down [102]. 

Zone 2B - Stick slip zone is characterized by blend morphology [103], Higher toughness reduces the distance between adjacent ridges. 

Progression of the Stick/Slip Zones in a Dry Wheei-Rail Contact Updating Theories on the Basis of Tribological Reality... 

Progression of the stick / slip zones in a dry wheel-rail contact ... 

Improved accuracy of power train control has highlighted the limits of this optimization technique since the contact conditions of the models, i.e. the stick / slip zones, do not take into account the physical phenomena involved, although they are hardly known. 

To attenuate this difficulty, the recent works presented in this paper, allow describing the tribological reality of a wheel-rail contact, i.e. the progression of the stick / slip zones. This reality is achieved thanks to monitoring the changes in the the characteristics of the third body present between wheel and rail. 

Carter [5] developed the first theory of a onedimensional elastic contact rolling with friction in longitudinal creep, very slow rolling speed (Va) and smooth surfaces. This author experimentally and theoretically proves the coexistence of stick / slip zones in the contact, the distribution of which varies as a function of longitudinal creep. The coexistence of zones is obtained by superimposing the tangential... 

This curve highlights the micro-slip and complete slip phase. These initial results allowed Haines and OUerton [6] to deduct the distribution of the tangential stresses in an elliptical contact for the case of longitudinal creep. Nevertheless, the progression of Carter s curve remains valid, but in the knowledge that the distribution of the stick / slip zones is now elliptic (Figure 3). 

Progression of the Stick / Slip Zones in a Dry Wheel-Raii Contact ... 

The ubiquity of this power-law behaviour in SCG tests on PE has been the subject of considerable discussion, usually based on the assumption of a fibril creep failure mechanism [43, 45, 46, 47, 76, 79]. At high and intermediate K, after a certain induction period, steady-state crack advance is generally observed to occur by a stick-slip mechanism all or part of the fibrillar zone breaks down rapidly after an incubation time during which fibril creep takes place. The crack-tip then advances rapidly over a short distance and a new fibrillar zone stabilises, as sketched in Fig. 12. 

The fault thickness depends on the ratio of solid friction resistance (to slippage) and the strength of the intact rock material. At the transition to the middle crust they begin to have the same order, the breaking of faults edges takes place. The stick-slip phenomenon. Brace (1972), is an indicator of competition of fault asperity crushing and slippage. This happens in the PT zone (III) where the faults are widened due to dilatancy. Then low velocity zones (LVZ) as porous/fractured layers appear. 

On the fnction image (Figure 5.a), one can notice a low friction zone, in the centre of the track, corresponding to the presence of the tribofilm. The low friction effect of the tribofilm lasts for 220 cycles. After that stick-slip occurs. 

Frederich established one of the first progressions [8]. The friction function which it defines results from on site tests. The fnction is a function of the rolling speed and the normal force applied to a wheel. Unfortunately, the relations of macroscopic causes (mechanical parameters) in microscopic effects (variation of the fnction) are not physically known. Therefore, Ohyama carried out laboratory experiments with layers injected into the contact where their shear stress were expressed as a function of the ratio of two coefficients static friction ps and kinematic pd [9]. The first coefficient was defined in the stick zone while the second was in the slip zone (Figure 4). Thus the total tangential force was the integral of the tangential stresses qi (x) and q2(x) of each zone. 

The term "avalanche," as applied to granular and disordered material, has a rich and varied span. The conventional term brings to mind destructive flows of snow, soil, or mud down the surfaces of mountains and hillsides. Indeed, researchers around the world [1,2] are concerned with what happens in such complex flows. Several aspects of these phenomena are key, including the idea of a buildup of stress (here, shear stress), failure, and a dynamical response that typically involves flow until a new stable state is attained. These features are not only unique to avalanches on hillsides, but occur also in polycrystalline magnetic systems, in earthquake fault zones, and in a variety of more idealized granular and frictional systems. These kinds of phenomena are sometimes referred to as stick-slip and... 

The decreasing curve commencing at point F is the result of the frictional resistance while the fibre is being extracted from the matrix, with its embedded length continuously decreasing. This zone is characterized by a stick-slip behaviour, which occurs when the ductile fibre is drawn from the brittle matrix. As a result, the curve in this zone is usually not smooth. 

The feed zone has the most effects on solid conveying of the resin. Three coefficients of friction take place, namely friction between barrel and pellet, between pellet and pellet, and between root of the screw and pellet. Solid conveying is the process wherein the material must stick to the barrel and slip on the screw. Hence, cooling root of screw will reduce the coefficient of friction between the screw and the plastic pellets. Screw cooling should be installed in the core of the screw in the feed section to give another zone of temperature control on the extruder. 

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