Yield stress of oxide dispersions-intermolecular forces of adsorbed small ionic additives and particle surface roughness

Miniature devices including MEMS and the head disk interface in magnetic storage often include very smooth surfaces, typically having root-mean-square roughness, σ of the order of 10 nm or less. When such smooth surfaces contact, or come into proximity of each other, either in dry or wet environments, then strong intermolecular (adhesive) forces may arise. Such strong intermolecular forces may result in unacceptable and possibly catastrophic adhesion, stiction, friction and wear. In the present paper, a model termed sub-boundary lubrication (SBL) adhesion model is used to calculate the adhesion forces, and an elastic-plastic model is used to calculate the contact forces at typical MEMS interfaces. Several levels of surface roughness are investigated representing polished and as-deposited polysilicon films that are typically found in MEMS. The SBL adhesion model reveals the significance of the surface roughness on the adhesion and pull-off forces as the surfaces become smoother. The validity of using the SBL adhesion model to estimate the pull-off forces in miniature systems is further supported by direct comparison with experimental pull-off force measurements performed on silicon and gold interfaces. Finally, the significance of the interfacial forces as relate to the reliability of MEMS interfaces is discussed.

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Pengaruh Shot Peening Terhadap Kekerasan Dan Kekasaran Produk Chemical Milling Paduan Aluminium Yang Telah Di Stretching

JURNAL KAJIAN TEKNIK MESIN ◽

10.52447/jktm.v5i1.2995 ◽

2020 ◽

Vol 5 (1) ◽

pp. 36-41

Author(s):

Yovial Mahyoedin ◽

Jamasri Jamasri ◽

Rizky Arman ◽

Wenny Marthiana ◽

Suryadima Suryadima

Keyword(s):

Surface Roughness ◽

Yield Stress ◽

Shot Peening ◽

Milling Process ◽

Chemical Milling ◽

Al 2024

AbstrakPenelitian ini bertujuan untuk mengetahui pengaruh shot peening terhadap kekasaran permukaan produk pembuatan kimia Al 2524-T3 dan Al 2024-T3 yang telah diregangkan. Paduan ini direntangkan melampaui tegangan luluh, yaitu masing-masing 1%, 3% dan 5%, dan kemudian dilakukan proses penggilingan kimia di satu sisi. Etching yang digunakan dalam proses penggilingan kimia adalah larutan NaOH + Na2S + H2O dengan konsentrasi tertentu. Permukaan dilakukan proses shot peening dengan intensitas yang bervariasi masing-masing 0,03 A, 0,05 A dan 0,07 A. Bahan itu kemudian diuji kekasaran permukaan dan kekerasannya. Hasil penelitian menunjukkan bahwa kekasaran permukaan dan kekerasan material meningkat dengan meningkatnya intensitas peening. Namun, ketebalan Al 2524-T3, yang lebih tipis dari Al 2024-T3 menyebabkan tidak signifikannya proses peening shot yang diberikan pada material.. Kata kunci: Shot Peening, Chemical Milling, Kekerasan, Kekasaran Permukaan AbstractThis study aims to investigate the influence of shot peening on hardness and surface roughness of chemical mlling product Al 2524-T3 and Al 2024-T3 which have been stretched. These alloys were stretched beyond yield stress, namely 1%, 3% and 5% of each, and then performed chemical milling process of one side. The etching used in chemical milling process were NaOH+Na2S+H2O solutions with certain concentration. The surface was performed shot peening process with varying intensity of 0.03 A, 0.05 A and 0.07 A respectively. The material were then tested its surface roughness and hardness. The results show that surface roughness and hardness of material increases with the increase of peening intensity. However, the thickness of Al 2524–T3, which is thinner than Al 2024-T3 causing insignificance of the shot peening process given to the materials. Keywords: Shot Peening, Chemical Milling, Hardness, Surface Roughness

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Effect of Particle Surface Roughness on Densification of Coarse-Textured Soil

Soil Science Society of America Journal ◽

10.2136/sssaj1980.03615995004400040006x ◽

1980 ◽

Vol 44 (4) ◽

pp. 692-697 ◽

Cited By ~ 16

Author(s):

R. M. Cruse ◽

D. K. Cassel ◽

F. G. Averette

Keyword(s):

Surface Roughness ◽

Particle Surface

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Effects of Particle Surface Roughness on In-Die Flow and Tableting Behavior of Lactose

Journal of Pharmaceutical Sciences ◽

10.1016/j.xphs.2019.04.028 ◽

2019 ◽

Vol 108 (9) ◽

pp. 3011-3019 ◽

Cited By ~ 1

Author(s):

Justin Yong Soon Tay ◽

Berlinda Wen Ting Kok ◽

Celine Valeria Liew ◽

Paul Wan Sia Heng

Keyword(s):

Surface Roughness ◽

Particle Surface

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Elastic back-scattering patterns via particle surface roughness and orientation from single trapped airborne aerosol particles

Journal of Quantitative Spectroscopy and Radiative Transfer ◽

10.1016/j.jqsrt.2016.09.018 ◽

2017 ◽

Vol 187 ◽

pp. 224-231 ◽

Cited By ~ 10

Author(s):

Richard Fu ◽

Chuji Wang ◽

Olga Muñoz ◽

Gorden Videen ◽

Joshua L. Santarpia ◽

...

Keyword(s):

Surface Roughness ◽

Aerosol Particles ◽

Particle Surface ◽

Back Scattering

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Molecular Dynamic Simulation of Surface Roughness Effects on Nanoscale Flows

ASME 2009 7th International Conference on Nanochannels, Microchannels and Minichannels ◽

10.1115/icnmm2009-82187 ◽

2009 ◽

Author(s):

Ali Kharazmi ◽

Reza Kamali

Keyword(s):

Surface Roughness ◽

Solid Wall ◽

Intermolecular Forces ◽

Intermolecular Potential ◽

Roughness Effects ◽

Time Step ◽

Restoring Force ◽

Rapid Sampling ◽

Micro Channels ◽

Fifth Order

In the present study, a molecular based scheme has been developed for simulating flows in nano- and micro-channels with roughness. In micro channel flow, there is some difference on the flow friction between roughness and cavitations which is not well studied. The presented approach is based on the molecular dynamics (namely MD) in which different ensemble has been used. For modeling the simulation the classical Newtonian particles are allowed to obey Newtonian mechanics and intermolecular forces are founded by integrating intermolecular potential. Lennard-Jones potential is used to model the interactions between particles. Particles equation of motion is integrated using fifth order Gear predictor-corrector. To ensure rapid sampling of phase space, the time step is made as large as possible. Periodic boundary condition is implemented via minimum image convention. Each atom of the solid wall is anchored at its lattice site by a harmonic restoring force and its temperature has been controlled by utilizing Nose-Hoover thermostat. The roughness is implemented on the lower channel wall. To make a comparison between the effect of roughness and cavitation, the same dimension is used for both for different aspect ratio. To allow comparison with previous results the same fluid density has been used. The effects of surface roughness and cavitation on velocity distribution of hydrophobic and hydrophilic wall undergoing Poiseuille flow are presented.

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A Novel Multi-Scale Particle Morphology Descriptor with the Application of SPHERICAL Harmonics

Materials ◽

10.3390/ma13153286 ◽

2020 ◽

Vol 13 (15) ◽

pp. 3286

Author(s):

Wei Xiong ◽

Jianfeng Wang ◽

Zhuang Cheng

Keyword(s):

Surface Roughness ◽

Scale Effect ◽

Scale Effects ◽

Particle Surface ◽

Relative Length ◽

Particle Morphology ◽

Length Scale ◽

Multi Scale ◽

Rate Of Increase ◽

Macro Scale

Particle morphology is of great significance to the grain- and macro-scale behaviors of granular soils. Most existing traditional morphology descriptors have three perennial limitations, i.e., dissensus of definition, inter-scale effect, and surface roughness heterogeneity, which limit the accurate representation of particle morphology. The inter-scale effect refers to the inaccurate representation of the morphological features at the target relative length scale (RLS, i.e., length scale with respective to particle size) caused by the inclusion of additional morphological details existing at other RLS. To effectively eliminate the inter-scale effect and reflect surface roughness heterogeneity, a novel spherical harmonic-based multi-scale morphology descriptor Rinc is proposed to depict the incremental morphology variation (IMV) at different RLS. The following conclusions were drawn: (1) the IMV at each RLS decreases with decreasing RLS while the corresponding particle surface is, in general, getting rougher; (2) artificial neural network (ANN)-based mean impact values (MIVs) of Rinc at different RLS are calculated and the results prove the effective elimination of inter-scale effects by using Rinc; (3) Rinc shows a positive correlation with the rate of increase of surface area RSA at all RLS; (4) Rinc can be utilized to quantify the irregularity and roughness; (5) the surface morphology of a given particle shows different morphology variation in different sections, as well as different variation trends at different RLS. With the capability of eliminating the existing limitations of traditional morphology descriptors, the novel multi-scale descriptor proposed in this paper is very suitable for acting as a morphological gene to represent the multi-scale feature of particle morphology.

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