Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 68 for “"Stick-Slip"”.
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Transfer lubrication techniques in a stick slip situation.
… lubrication technique as a means of eliminating stick slip vibratory motion. The experimental apparatus consisted of a replaceable disc fastened to a rotor supported in air journal bearings. The disc was driven rotationally via an elastic member and radially loaded by two diametrically opposed …
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Stick-slip behavior of liquid droplets on pillar-arrayed PDMS surfaces
… moves on a rough surface, it usually undergoes a stick-slip motion. However, this phenomenon lacks a proper explanation with micro-level details and analysis. . In this study, a series of experiments were conducted to monitor the contact line (CL) evolution and resistant force over time when …
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Stress and stick-slip analyses for optical fiber pull-out and thin film peel tests
… polarization-maintaining optical fibers, and the stick-slip analyses of the topical fiber pull-out experiment and the thin-film peel test. For the first topic, the exact stress distribution in the fiber cross section is found in a closed form for various optical fibers using the complex variable …
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Mesoscale Forces and Grain Motion in Granular Media Exhibiting Stick-Slip Dynamics: Effects of Friction and Grain Shape
… of mesoscale force chains, and macroscopic stick-slip dynamics of granular materials through novel experiments. In one set of experiments, an intruder is pushed by a spring through an annular cell filled with a quasi-2D monolayer of photoelastic grains that either contact a glass substrate …
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The effect of archwire vibrations on the stick-slip behavior of the bracket-archwire interface utilizing clinically relevant tipping moments
This study evaluated bracket-archwire frictional resistance as a function of ligation method and archwire vibration. In vivo archwire vibrations were measured to obtain frequencies and amplitudes for ex vivo testing. Active and passive ligation methods were compared for 9 vibration scenarios …
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Frictional oscillations in elastomeric sliding
… to determine the conditions under which noise or stick-slip occurs. Elastomers tested include natural rubber with 0,5,10, 20, and 50 phr (parts per hundred rubber) carbon black, butyl, polydimethyl siloxane, and fluorocarbon. The hard counterfaces include chromium oxide, aluminum, epoxy paint, and …
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Frictional vibrations in structural polymers
… were observed - steady sliding, a single stick followed by steady sliding, non-sustained stick-slip oscillations that decayed after several oscillations, and stick-slip oscillations lasting several minutes. Several observations were made regarding the experimental results. It was observed …
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Wetting hysteresis and droplet roll off behavior on superhydrophobic surfaces by Katherine Marie Smyth.
… are still not fully understood. Particularly, stick-slip behavior of the three-phase contact line has been observed and qualitatively attributed to surface or chemical heterogeneities, but the behavior has yet to be quantified. In this thesis, contact line motion particularly focused on …
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Localization and instability in sheared granular materials: role of friction and vibration
Shear banding and stick-slip instabilities have been long observed in sheared granular materials. Yet, their microscopic underpinnings, interdependencies and variability under different loading conditions have not been fully explored. Here, we use a non-equilibrium thermodynamics model, the Shear …
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Influence of Bit Design on the Stability of the Rotary Drilling System
… to drilling dysfunctions such as bit bounce, stick-slip and whirling. These dysfunctions cause premature failure of drill bits and other components within the system, ultimately leading to increased cost of the drilling operation. It is of interest, therefore, to understand the mechanism of …
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Hybrid Modelling and Optimisation of Oil Well Drillstrings
… to torsional and longitudinal stresses caused by stick-slip phenomena during the drilling operation causes great expense to industry. Due to the complicated and harsh drilling environment, modelling of the drillstring becomes an essential requirement in studies. Currently, this is achieved by …
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Effect of hydrogen on the coefficient of friction of iron
… was calculated and the amplitude of the "stick-slip" behavior from each environment was observed. It was found that the coefficient of friction obtained in the hydrogen environment was significantly smaller than the values obtained in laboratory air and nitrogen. Also, the amplitude of the …
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Friction under microscope with trapped ions in optical lattices
… even at the atomic level (nanofriction), where stick-slip processes are known to be the dominant source of dissipation and wear. Friction is studied in this thesis work with unprecedented spatial resolution and control at the individual-atom level in the synthetic frictional interface between …
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The role of system dynamics on the behavior of elastomeric friction
… Three friction regimes were observed which were stick-slip oscillations, quasi-harmonic oscillations, and steady sliding. System stiffness and load were varied to observe changes in the critical velocities bounding each regime. System parameters were varied to determine sliding conditions leading …
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Experimental investigation of frictional properties of the human fingerpad
… sequence shows that the relative motion, or slip, between the fingerpad and the glass plate indentor began at the periphery of the contact region and propagated towards the center. Under all the stroke conditions, the glass plate slipped smoothly across the fingerpad. In contrast, both …
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Ultrahigh vacuum studies of the boundary lubrication of metals
… of clean Cu(111) surfaces was characterized by stick-slip sliding behavior and high static friction coefficients.
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Laboratory analysis of restrenghtening on simulated faults
… been conducted to study the factors that effect stick-slip behavior of bare rock surfaces, and healing of simulated fault gouge under a range of physico-chemical conditions. We have performed experiments to investigate the repetitive stick-slip behavior of initially bare granite surfaces (nominal …
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Thermorheology and processing of polyethylene blends : macromolecular structure effects
… the amplitude of the oscillations in the stick-slip flow regime, known as oscillating melt fracture, were found to scale with the weight fraction of LDPE. Amounts as low as 1 wt% LDPE have a significant effect on the amplitude of pressure oscillations. These effects are clearly due to the …
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Modeling, Identification and Simulation of Dynamics of Structures With Joints and Interfaces
… edges of the elements. Thus, micro-scale stick-slip behavior along the joint interfaces can be captured even with a relatively coarse mesh. Numerical examples demonstrate that the general joint interface element is capable of accounting for the friction and impact damping in joint …
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Advances in hybrid water-lubricated journal bearings for use in ocean vessels
… increased abrasive and adhesive wear as well as stick-slip shaft motion. This project focuses on developing a hybrid journal bearing capable of operating with hydrostatic pump pressure at lower rpm, while still maintaining the capability for hydrodynamic operation at higher rpm. Benefits of such …
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