Tuning the Dissipation in Friction Dampers Excited by Depolarized Waves Across Patterned Surfaces

2016 ◽  
Vol 138 (5) ◽  
Author(s):  
Melih Eriten ◽  
Ahmet D. Usta ◽  
Lejie Liu
Keyword(s):  
Energy Dissipation ◽  
Dynamic Models ◽  
Wave Attenuation ◽  
Homogenization Theory ◽  
Patterned Surfaces ◽  
Practical Utilization ◽  
Wave Depolarization ◽  
Frictional Damping ◽  
Friction Oscillator ◽  
Surface Patterns

Recently, patterned surfaces (elastodynamic meta-surfaces) were shown to cause mechanical wave depolarization resulting in conversion of uniaxial waves to multiaxial vibrations. Frictional oscillators loaded in multiple directions provide more tailorable damping scheme when compared to uniaxially loaded equivalents. This paper utilizes wave depolarization properties of patterned surfaces in tuning frictional damping. In particular, two-dimensional (2D) motion achieved by anisotropic wave reflection and depolarization across patterned surfaces is exerted on a simple friction oscillator; and frictional energy dissipation is studied using the homogenization theory and mechanics of a simple friction oscillator under macro and microslip conditions. The degree of depolarization is shown to control the extent of frictional shakedown (no-dissipation) zones and magnitude of energy dissipation for different incident wave frequencies and amplitudes. Transmission of the depolarized waves from the patterned surface to the friction oscillator enables higher and more uniform frictional damping for broader loading conditions. Uniform damping facilitates predictive linear dynamic models, and tuning the magnitude of damping permits efficient and robust wave attenuation, and energy transfer and localization in dynamic applications. A discussion on modeling assumptions and practical utilization of this potential is also provided. The presented potential of tuning frictional dissipation from very low to high values by simple surface patterns suggests that more sophisticated surface patterns can be designed for spatially varying frequency-dependent wave attenuation.

scholarly journals Wave energy dissipation in the mangrove vegetation off Mumbai, India

2017 ◽  
Author(s):  
Samiksha S. Volvaiker ◽  
Ponnumony Vethamony ◽  
Prasad K. Bhaskaran ◽  
Premanand Pednekar ◽  
MHamsa Jishad ◽  
...  
Keyword(s):  
Energy Dissipation ◽  
Drag Coefficient ◽  
Wave Height ◽  
Wave Attenuation ◽  
Coastal Region ◽  
Measured Data ◽  
Vegetation Density ◽  
Mangrove Vegetation ◽  
Wave Height Attenuation ◽  
Set Up

Abstract. Coastal regions of India are prone to sea level rise, cyclones, storm surges and human induced activities, resulting in flood, erosion, and inundation. The primary aim of the study is to estimate wave attenuation by mangrove vegetation using SWAN model in standalone mode, as well as SWAN nested with WW3 model for the Mumbai coastal region. To substantiate the model results, wave measurements were carried out during 5–8 August 2015 at 3 locations in a transect normal to the coast using surface mounted pressure level sensors under spring tide conditions. The measured data presents wave height attenuation of the order of 52 %. The study shows a linear relationship between wave height attenuation and gradual changes in water level in the nearshore region, in phase with the tides. Model set-up and sensitivity analyses were conducted to understand the model performance to vegetation parameters. It was observed that wave attenuation increased with an increase in drag coefficient (Cd), vegetation density, and stem diameter. For a typical set-up for Mumbai coastal region having vegetation density of 0.175 per m2, stem diameter of 0.3 m and drag coefficient varying from 0.4 to 1.5, the model reproduced attenuation, ranging from 49 to 55 %, which matches well with the measured data. Spectral analysis performed for the cases with and without vegetation very clearly portrays energy dissipation in the vegetation area as well as spectral changes. This study has the potential of improving the quality of wave prediction in vegetation areas, especially during monsoon season and extreme weather events.

Multi-scale surface patterning – an approach to control friction and lubricant migration in lubricated systems

2019 ◽  
Vol 71 (8) ◽  
pp. 1007-1016 ◽  
Author(s):  
Philipp G. Grützmacher ◽  
Andreas Rosenkranz ◽  
Adam Szurdak ◽  
Markus Grüber ◽  
Carsten Gachot ◽  
...  
Keyword(s):  
Laboratory Tests ◽  
Journal Bearing ◽  
Friction Reduction ◽  
Patterned Surfaces ◽  
Test Rig ◽  
Content Type ◽  
Multi Scale ◽  
Surface Patterns ◽  
Lubricant Migration ◽  
Scale Surface

Purpose The paper aims to investigate the possibilities to control friction in lubricated systems by surface patterning, making use of a multi-scale approach. Surface patterns inside the tribological contact zone tend to directly reduce friction, whereas surface patterns located in the close proximity of the contact area can improve the tribological performance by avoiding lubricant starvation and migration. Finally, optimized surface patterns were identified by preliminary laboratory tests and transferred to a journal bearing, thus testing them under more realistic conditions. Design/methodology/approach Surface patterns on a large scale (depth > 10 µm) were fabricated by micro- and roller-coining, whereas surface patterns on a small scale (depth < 2 µm) were produced by direct laser interference patterning. The combination of both techniques resulted in multi-scale surface patterns. Tribologically beneficial surface patterns (verified in ball-on-disk laboratory tests) were transferred onto a journal bearing’s shaft and tested on a special test-rig. To characterize the lubricant spreading behavior, a new test-rig was designed, which allowed for the study of the lubricant’s motion on patterned surfaces under the influence of a precisely controlled temperature gradient. Findings All tested patterns accounted for a pronounced friction reduction and/or an increase in oil film lifetime. The results from the preliminary laboratory tests matched well, with results from the journal bearing test-rig, both tests showing a maximum friction reduction by a factor of 3-4. Numerical investigations, as well as experiments, have shown the possibility to actively guide lubricant over patterned surfaces. Smaller periodicities, as well as greater structural depths and widths, led to a more pronounced anisotropic spreading and/or greater spreading velocities. Multi-scale surfaces demonstrated the strongest effects regarding the lubricant’s spreading behavior. Originality/value Friction, as well as lubricant migration, can be successfully controlled by using micro-coined, laser-patterned and/or multi-scale surfaces. To the best of the authors’ knowledge, the study demonstrates for the first time the unique possibility to transfer results obtained in laboratory tests to a real machine component.

scholarly journals Wheel-rail dynamics with closely conformal contact Part 2: Forced response, results and conclusions

1997 ◽  
Vol 211 (1) ◽  
pp. 27-40 ◽  
Author(s):  
J Bhaskar ◽  
K. L. Johnson ◽  
J Woodhouse
Keyword(s):  
Energy Dissipation ◽  
Dynamic Models ◽  
Single Point ◽  
Point Contact ◽  
Forced Response ◽  
Normal Displacement ◽  
Transit System ◽  
Frictional Energy ◽  
Frictional Energy Dissipation ◽  
Conformal Contact

The linearized dynamic models for the conformal contact of a wheel and rail presented in reference (1) have been used to calculate the dynamic response to a prescribed sinusoidal ripple on the railhead. Three models have been developed: single-point contact with low or high conformity, and two-point contact. The input comprises a normal displacement Δeiwt together with a rotation Δeiwt applied to the railhead. The output comprises rail displacements and forces, contact creepages and forces, and frictional energy dissipation. According to the Frederick-Valdivia hypothesis, if this last quantity has a component in phase with the input ripple, the amplitude of the ripple will be attenuated, and vice versa. Over most of the frequency range, a pure displacement input (Ψ = 0) was found to give rise, predominantly, to a normal force at the railhead. A purely rotational input (Δ = 0) caused a single point of contact to oscillate across the railhead or, in the case of two-point contact, to give rise to fluctuating out-of-phase forces at the two points. The general tenor of behaviour revealed by the three models was similar: frictional energy dissipation, and hence wear, increases with conformity and is usually of such a phase as to suppress corrugation growth. Thus the association, found on the Vancouver mass transit system, of corrugations with the development of close conformity between wheel and rail profiles must arise from some feature of the system not included in the present models.

scholarly journals Carbon nano-ink coated open cell polyurethane foam with micro-architectured multilayer skeleton for damping applications

RSC Advances ◽  
2016 ◽  
Vol 6 (83) ◽  
pp. 80334-80341 ◽  
Author(s):  
Xiao-Chong Zhang ◽  
Fabrizio Scarpa ◽  
Ronan McHale ◽  
Andrew P. Limmack ◽  
Hua-Xin Peng
Keyword(s):  
Carbon Nanotube ◽  
Energy Dissipation ◽  
Polyurethane Foam ◽  
Open Cell ◽  
Frictional Damping ◽  
Open Cell Foams ◽  
Carbon Nanotube Ink

Carbon nanotube ink coated multilayered polyurethane open cell foams utilize the CNT–CNT interfacial frictional damping mechanism, thus dramatically improving the foam energy dissipation capability by 270%.

Towards superlubricity in nanostructured surfaces: the role of van der Waals forces

2018 ◽  
Vol 20 (34) ◽  
pp. 21949-21959 ◽  
Author(s):  
Fernando G. Echeverrigaray ◽  
Saron R. S. de Mello ◽  
Leonardo M. Leidens ◽  
Marcelo E. H. Maia da Costa ◽  
Fernando Alvarez ◽  
...  
Keyword(s):  
Thin Films ◽  
Energy Dissipation ◽  
Van Der Waals ◽  
Van Der Waals Forces ◽  
Nanostructured Surfaces ◽  
Sliding Interface ◽  
Frictional Damping

Energy dissipation associated with frictional damping mechanisms owing to van der Waals (vdW) forces by induced polarizability at the sliding interface of a-C:H thin films.

Analysis of Non-Classical Models which Have been Subjected to Percussive Loads Using Equations of Energy and Power

2014 ◽  
Vol 1036 ◽  
pp. 608-613 ◽  
Author(s):  
Krzysztof Jamroziak ◽  
Miroslaw Bocian
Keyword(s):  
Energy Dissipation ◽  
Impact Energy ◽  
Dynamic Models ◽  
Specific Impulse ◽  
Pulse Excitation ◽  
Classical Dynamic ◽  
Simple Description ◽  
Classical Models ◽  
The One ◽  
The Impact

The article presents an analysis of impact energy dissipation process with selected non-classical dynamic models. Identification of impact energy dissipation phenomena in layered mechanical systems (for example: composite ballistic shields) is a great challenge, because on the one hand a model with parameters responsible for the energy dissipation is being sought on the one hand and on the other it is necessary to optimise the number of parameters. The sought model should be reduced to a simple description of the phenomenon and should contain a complex reproduction of the whole mechanical system. In this case the impact energy dissipation was described using selected degenerate systems. Models were treated by extortion surge having a specific impulse of force. The mathematical description of the pulse excitation was carried out using the energy and potency balance equations. The verification of mathematical identification equations was conducted using a computer simulation technique for the selected model’s parameters.

Inertia Driven Dispersion Between Patterned Surfaces

2005 ◽  
Author(s):  
P. Assemat ◽  
A. Bergeon ◽  
F. Plouraboue´
Keyword(s):  
Reynolds Number ◽  
Velocity Field ◽  
Cross Sections ◽  
Applied Pressure ◽  
Patterned Surfaces ◽  
Surface Patterns ◽  
Passive Tracers ◽  
Smooth Periodic Function ◽  
Micro Systems ◽  
Micro Mixer

Understanding and controlling stirring in micro-systems is necessary for the design of efficient passive micro-mixer. In this study, we focus on the dispersion of passive tracers injected in flows in between two rough surfaces under weak inertia influence (small but non-zero Reynolds number). The flow is induced by a constant applied pressure gradient between two cross-sections of the channel and the velocity field is calculated thanks to an extension of the lubrication approximation taking into account the first order inertial corrections. Tracers trajectories are obtained by integrating numerically the quasi-analytic velocity field. Our purpose is to examine the flow structure for various surface patterns and various Reynolds number. We focus on a simplified aperture field which is a smooth periodic function. This study puts forward interesting behavior of streamlines and show the dispersion of passive tracers in various geometries.

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