Distribution effect of surface texture on the elastic deformation in soft contacts

2019 ◽  
Vol 71 (10) ◽  
pp. 1194-1199
Author(s):  
Binbin Su ◽  
Wei Huang ◽  
Xiaolei Wang
Keyword(s):  
Elastic Deformation ◽  
Surface Texture ◽  
Load Condition ◽  
Elastohydrodynamic Lubrication ◽  
Distribution Patterns ◽  
Content Type ◽  
Lubrication Condition ◽  
Typical Distribution ◽  
Effect Of Surface

Purpose This paper aims to experimentally investigate the elastic deformation behavior of surface texture in soft contacts under lubricated condition. Design/methodology/approach Dimples with two typical distribution patterns are fabricated on the contacting surface by Quasi-LIGA technique. In situ observation on the elastic deformation of contacting surface is performed through optical interferometry. Comparisons of the elastic deformation around the dimples in different distribution patterns are conducted. Findings The results show that the effect of dimple distribution patterns on elastic deformation becomes increasingly serious with the growth of applied load. Dimples in square distribution present a stronger interaction with each other and lead to a more alleviative deformation under heavier load condition. The action range of dimple, especially in square distribution, is seriously compressed by surrounding dimples. Originality/value Square distribution is preferentially suggested for surface texture with respect to minimum elastic deformation in soft contacts under elastohydrodynamic lubrication condition.

Research on sealing performance of oil seals with micro-dimple texture on lips

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Fuying Zhang ◽  
Yuanhao Zhang
Keyword(s):  
Peer Review ◽  
Surface Texture ◽  
Elastohydrodynamic Lubrication ◽  
Friction Torque ◽  
Pumping Rate ◽  
Content Type ◽  
Rotation Direction ◽  
Sealing Performance ◽  
Pumping Efficiency ◽  
Shaft Seals

Purpose The purpose of this paper is to study the pumping efficiency of oil seals with different surface textures at different speeds, and the influence of the rotation direction of triangular texture on the sealing performance was further analyzed. Design/methodology/approach Based on the theory of elastohydrodynamic lubrication and the pumping mechanism of rotary shaft seals, establishing a numerical model of mixed lubrication in oil seal sealing area. The model is coupled with the lip surface texture parameters and the two-dimensional average Reynolds equation considering the surface roughness. Findings The results show that the application of lip surface texture technology has obvious influence on the oil film thickness, friction torque and pumping rate of oil seal. The triangular texture has the most significant effect on the increase of pump suction rate. When the rotation direction of triangular texture is 315 degrees, the pumping rate of oil seal is the largest compared with the other seven directions. Originality/value The model has a comprehensive theoretical guidance for the design of new oil seal products, which provides a certain basis for the application of surface texture technology in the field of sealing in the future. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-06-2020-0198/

A mixed elastohydrodynamic lubrication model based on virtual rough surface for studying the tribological effect of asperities

2018 ◽  
Vol 70 (2) ◽  
pp. 408-417 ◽  
Author(s):  
Hui Zhang ◽  
Guangneng Dong ◽  
Guozhong Dong
Keyword(s):  
Film Thickness ◽  
Rough Surface ◽  
Current Model ◽  
Elastohydrodynamic Lubrication ◽  
Hydrodynamic Pressure ◽  
Surface Pattern ◽  
Curvature Radius ◽  
Content Type ◽  
Stribeck Curves ◽  
Effect Of Surface

Purpose The main purpose of this paper is to present the effort on developing a mixed elastohydrodynamic lubrication (EHL) model to study the tribological effect of asperities on rough surface. Design/methodology/approach The model, with the use of the average flow Reynolds equation and the K-E elasto-plastic contact model, allows predictions of hydrodynamic pressure and contact pressure on the virtual rough surface, respectively. Then, the substrate elastic deformation is calculated by discrete convolution fast-Fourier transform (DC-FFT) method to modify the film thickness recursively. Afterwards, corresponding ball-on-disk tests are conducted and the validity of the model demonstrated. Moreover, the effects of asperity features, such as roughness, curvature radius and asperity pattern factor, on the tribological properties of EHL, are also discussed though plotting corresponding Stribeck curves and film thickness shapes. Findings It is demonstrated that the current model predicts very close data compared with corresponding experimental results. And it has the advantage of high accuracy comparing with other typical models. Furthermore, smaller roughness, bigger asperity radius and transverse rough surface pattern are found to have lower friction coefficients in mixed EHL models. Originality/value This paper contributes toward developing a mixed EHL model to investigate the effect of surface roughness, which may be helpful to better understand partial EHL.

Two-Dimensional Elastohydrodynamic Lubrication Fluid Flow Modeling of Piston Top Ring Considering Elastic Deformation in Initial Engine Start Up

2010 ◽  
Author(s):  
M. Afzaal Malik ◽  
Syed Adnan Qasim ◽  
Ali Usman ◽  
Riaz A. Mufti
Keyword(s):  
Elastic Deformation ◽  
Elastohydrodynamic Lubrication ◽  
Solution Technique ◽  
Two Dimensional ◽  
Lubricating Film ◽  
Start Up ◽  
Lubrication Condition ◽  
Piston Ring Lubrication ◽  
Cylinder Bore ◽  
Engine Start

The absence of Elastohydrodynamic Lubrication (EHL) between the first piston compression ring (top ring) and the liner surface in the initial engine startup causes adhesive wear whereas the presence of such a film enhances engine life by wear prevention. In the current work, a two dimensional model is presented for barrel-faced ring profile by considering elastic deformation and EHL. A non-axisymmetric elliptical cylinder bore and an elastic ring are considered to determine circumferential flow. The EHL film profile is generated by solving the two dimensional Reynolds equation using inverse solution technique and finite difference method in fully flooded lubrication condition. The results show that piston ring lubrication depends on the bore shape or bore out-of-roundness and lubricating film thickness due to which circumferential flow gets significantly reduced during the initial engine start up.

Effect of surface texture on the friction of WC-TiC/Co cemented carbide under a water-miscible cutting fluid environment

2018 ◽  
Vol 70 (7) ◽  
pp. 1350-1359 ◽  
Author(s):  
Minghua Pang ◽  
Xiaojun Liu ◽  
Kun Liu
Keyword(s):  
Friction Coefficient ◽  
Surface Texture ◽  
Cemented Carbide ◽  
Hertzian Contact ◽  
Cutting Fluid ◽  
Textured Surface ◽  
Content Type ◽  
Contact Width ◽  
Fluid Environment ◽  
Effect Of Surface

Purpose This study aims to clarify the influence mechanism of surface texture (arrays of circular/square and concave/convex) on the frictional properties of WC-TiC/Co cemented carbide under a water-miscible cutting fluid (JAEGER SW-105, 5 per cent) environment. Design/methodology/approach Four types of textured cemented carbide surfaces (arrays of circular/square and concave/convex that have different textured densities and sizes) were fabricated using laser surface technology. Pin-on-disc tests between an AISI 304 stainless steel ball and WC-TiC/Co cemented carbide samples were carried out for a variety of normal loads (1, 3 and 5 N) under a water-miscible cutting fluid environment. The effects of textured type, density and size on the friction coefficient were obtained. Findings Compared to a smooth surface, some textured samples successfully resulted in a reduced friction coefficient. The friction coefficient of textured WC-TiC/Co cemented carbide samples depended greatly on the textured type, density and size. Given the increase in textured density (ranging from 10 to 30 per cent), the friction coefficient of the test samples first decreased and then increased for all normal loads (1, 3 and 5 N), and the minimum friction coefficient was obtained at the textured density of 20 per cent. The concave textured surface showed obvious advantages in friction coefficient reduction regardless of textured density, size and normal load compared with the convex textured surface. Finally, the correlation between textured diameter/length and Hertzian contact width was studied for various normal loads and texture sizes. A 2.6 ratio of textured diameter/length to Hertzian contact width is recommended under for lubricated sliding contact with the water-miscible cutting fluid. Originality/value The main contribution of this work is in providing a design reference and obtaining an essential understanding on the effect of surface texture (arrays of circular/square and concave/convex) on the friction of WC-TiC/Co cemented carbide under a water-miscible cutting fluid environment.

Effect of surface roughness and hardness of leadframe on the bondability of gold wedge bonds

2019 ◽  
Vol 36 (2) ◽  
pp. 62-67
Author(s):  
Muhammad Nubli Zulkifli ◽  
Fuaida Harun ◽  
Azman Jalar
Keyword(s):  
Surface Roughness ◽  
Ultrasonic Vibration ◽  
Design Methodology ◽  
Laser Interferometer ◽  
Vertical Axis ◽  
Content Type ◽  
Pull Strength ◽  
The Relationship ◽  
Effect Of Surface

Purpose This paper aims to analyze the effect of surface roughness and hardness of leadframe on the bondability of gold (Au) wedge bond using in situ inspection of laser interferometer and its relationship with the deformation and wire pull strength. Design/methodology/approach The in situ inspection of ultrasonic vibration waveform through the changes of vertical axis (y-axis) amplitude of wire bonder capillary was carried out using laser interferometer to analyze the formation of Au wedge bond. The relationship between the changes of ultrasonic waveform of capillary with the deformation and the pull strength was analyzed to evaluate the bondability of Au wedge bonds. Findings It was observed that the changes in vertical axis amplitude of ultrasonic vibration waveform of wire bonder capillary can be used to describe the process of bonding formation. The loss of ultrasonic energy was exhibited in ultrasonic vibration waveform of wire bonding on leadframe that has higher value of roughness (leadframe A) as compared to that of leadframe that has lower value of roughness (leadframe B). The lower pull strength obtained by Au wedge bond further confirms the reduction of bond formation because of the higher deformation on leadframe A as compared to that of leadframe B. Originality/value The relationship between in situ measurement using laser interferometer with the bondability or deformation and wire pull strength of Au wedge bonds on different surface roughness and hardness of leadframes is still lacking. These findings provide a valuable data in analyzing the bonding mechanisms that can be identified based on the in situ measurement of ultrasonic vibration and the bondability of Au wedge bonds.

Nucleation and initial growth of Pd2Si crystals on Si(111)

1993 ◽  
Vol 51 ◽  
pp. 844-845
Author(s):  
Xianghong Tong ◽  
Oliver Pohland ◽  
J. Murray Gibson
Keyword(s):  
High Vacuum ◽  
Dark Field ◽  
Ultra High Vacuum ◽  
Initial Growth ◽  
Surface And Interface ◽  
Dark Field Imaging ◽  
Transmission Electron ◽  
Initial Stage ◽  
Effect Of Surface

The nucleation and initial stage of Pd2Si crystals on Si(111) surface is studied in situ using an Ultra-High Vacuum (UHV) Transmission Electron Microscope (TEM). A modified JEOL 200CX TEM is used for the study. The Si(111) sample is prepared by chemical thinning and is cleaned inside the UHV chamber with base pressure of 1x10−9 τ. A Pd film of 20 Å thick is deposited on to the Si(111) sample in situ using a built-in mini evaporator. This room temperature deposited Pd film is thermally annealed subsequently to form Pd2Si crystals. Surface sensitive dark field imaging is used for the study to reveal the effect of surface and interface steps.The initial growth of the Pd2Si has three stages: nucleation, growth of the nuclei and coalescence of the nuclei. Our experiments shows that the nucleation of the Pd2Si crystal occurs randomly and almost instantaneously on the terraces upon thermal annealing or electron irradiation.

Pituitary adenoma producing growth hormone and adrenocorticotropin: a histological, immunocytochemical, electron microscopic, and in situ hybridization study

1998 ◽  
Vol 88 (6) ◽  
pp. 1111-1115 ◽  
Author(s):  
Kalman Kovacs ◽  
Eva Horvath ◽  
Lucia Stefaneanu ◽  
Juan Bilbao ◽  
William Singer ◽  
...  
Keyword(s):  
Growth Hormone ◽  
In Situ Hybridization ◽  
Pituitary Adenoma ◽  
Immunoelectron Microscopy ◽  
Secretory Granules ◽  
Cell Types ◽  
Content Type ◽  
Separate Cell ◽  
Fine Print

✓ The authors report on the morphological features of a pituitary adenoma that produced growth hormone (GH) and adrenocorticotropic hormone (ACTH). This hormone combination produced by a single adenoma is extremely rare; a review of the available literature showed that only one previous case has been published. The tumor, which was removed from a 62-year-old man with acromegaly, was studied by histological and immunocytochemical analyses, transmission electron microscopy, immunoelectron microscopy, and in situ hybridization. When the authors used light microscopy, the tumor appeared to be a bimorphous mixed pituitary adenoma composed of two separate cell types: one cell population synthesized GH and the other ACTH. The cytogenesis of pituitary adenomas that produce more than one hormone is obscure. It may be that two separate cells—one somatotroph and one corticotroph—transformed into neoplastic cells, or that the adenoma arose in a common stem cell that differentiated into two separate cell types. In this case immunoelectron microscopy conclusively demonstrated ACTH in the secretory granules of several somatotrophs. This was associated with a change in the morphological characteristics of secretory granules. Thus it is possible that the tumor was originally a somatotropic adenoma that began to produce ACTH as a result of mutations that occurred during tumor progression.

scholarly journals Competition between Metals for Binding to Methanobactin Enables Expression of Soluble Methane Monooxygenase in the Presence of Copper

2014 ◽  
Vol 81 (3) ◽  
pp. 1024-1031 ◽  
Author(s):  
Bhagyalakshmi Kalidass ◽  
Muhammad Farhan Ul-Haque ◽  
Bipin S. Baral ◽  
Alan A. DiSpirito ◽  
Jeremy D. Semrau
Keyword(s):  
Methane Monooxygenase ◽  
High Specificity ◽  
Copper Uptake ◽  
Content Type ◽  
Soluble Methane Monooxygenase ◽  
Sds Page ◽  
Genes Encoding ◽  
Key Factor ◽  
Membrane Bound

ABSTRACTIt is well known that copper is a key factor regulating expression of the two forms of methane monooxygenase found in proteobacterial methanotrophs. Of these forms, the cytoplasmic, or soluble, methane monooxygenase (sMMO) is expressed only at low copper concentrations. The membrane-bound, or particulate, methane monooxygenase (pMMO) is constitutively expressed with respect to copper, and such expression increases with increasing copper. Recent findings have shown that copper uptake is mediated by a modified polypeptide, or chalkophore, termed methanobactin. Although methanobactin has high specificity for copper, it can bind other metals, e.g., gold. Here we show that inMethylosinus trichosporiumOB3b, sMMO is expressed and active in the presence of copper if gold is also simultaneously present. Such expression appears to be due to gold binding to methanobactin produced byM. trichosporiumOB3b, thereby limiting copper uptake. Such expression and activity, however, was significantly reduced if methanobactin preloaded with copper was also added. Further, quantitative reverse transcriptase PCR (RT-qPCR) of transcripts of genes encoding polypeptides of both forms of MMO and SDS-PAGE results indicate that both sMMO and pMMO can be expressed when copper and gold are present, as gold effectively competes with copper for binding to methanobactin. Such findings suggest that under certain geochemical conditions, both forms of MMO may be expressed and activein situ. Finally, these findings also suggest strategies whereby field sites can be manipulated to enhance sMMO expression, i.e., through the addition of a metal that can compete with copper for binding to methanobactin.

scholarly journals Specificity of Associations between Bacteria and the Coral Pocillopora meandrina during Early Development

2012 ◽  
Vol 78 (20) ◽  
pp. 7467-7475 ◽  
Author(s):  
Amy Apprill ◽  
Heather Q. Marlow ◽  
Mark Q. Martindale ◽  
Michael S. Rappé
Keyword(s):  
Small Subunit ◽  
Rrna Genes ◽  
Polymorphism Analysis ◽  
Roseobacter Clade ◽  
Small Subunit Rrna ◽  
Content Type ◽  
Sterile Seawater ◽  
Show Evidence ◽  
Coral Health

ABSTRACTRelationships between corals and specific bacterial associates are thought to play an important role in coral health. In this study, the specificity of bacteria associating with the coralPocillopora meandrinawas investigated by exposing coral embryos to various strains of cultured marine bacteria, sterile seawater, or raw seawater and examining the identity, density, and location of incorporated cells. The isolates utilized in this experiment included members of the Roseobacter and SAR11 clades of theAlphaproteobacteria, aPseudoalteromonasspecies of theGammaproteobacteria, and aSynechococcusspecies of theCyanobacteriaphylum. Based on terminal restriction fragment length polymorphism analysis of small-subunit rRNA genes, similarities in bacterial communities associated with 170-h-old planulae were observed regardless of treatment, suggesting that bacteria may have been externally associated from the outset of the experiment. Microscopic examination ofP. meandrinaplanulae by fluorescencein situhybridization with bacterial and Roseobacter clade-specific oligonucleotide probes revealed differences in the densities and locations of planulae-associated cells. Planulae exposed to either raw seawater or strains ofPseudoalteromonasand Roseobacter harbored the highest densities of internally associated cells, of which 20 to 100% belonged to the Roseobacter clade. Planulae exposed to sterile seawater or strains of the SAR11 clade andSynechococcusdid not show evidence of prominent bacterial associations. Additional analysis of the raw-seawater-exposed planulae via electron microscopy confirmed the presence of internally associated prokaryotic cells, as well as virus-like particles. These results suggest that the availability of specific microorganisms may be an important factor in the establishment of coral-bacterial relationships.

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