Bibliografie tematiche / Interfacial asperities

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Letteratura scientifica selezionata sul tema "Interfacial asperities"

Autore: Grafiati

Pubblicato: 7 settembre 2024

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Articoli di riviste sul tema "Interfacial asperities"

Han, Yujin, Pierre-Marie Thebault, Corentin Audes, Xuelin Wang, Haiwoong Park, Jian-Zhong Jiang e Arnaud Caron. "Temperature and chemical effects on the interfacial energy between a Ga–In–Sn eutectic liquid alloy and nanoscopic asperities". Beilstein Journal of Nanotechnology 13 (23 agosto 2022): 817–27. http://dx.doi.org/10.3762/bjnano.13.72.

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The interfacial energies between a eutectic Ga–In–Sn liquid alloy and single nanoscopic asperities of SiOx, Au, and PtSi have been determined in the temperature range between room temperature and 90 °C by atomic force spectroscopy. For all asperities used here, we find that the interfacial tension of the eutectic Ga–In–Sn liquid alloy is smaller than its free surface energy by a factor of two (for SiOx) to eight (for PtSi). Any significant oxide growth upon heating studied was not detected here, and the measured interfacial energies strongly depend on the chemistry of the asperities. We also observe a weak increase of the interfacial energy as a function of the temperature, which can be explained by the reactivity between SiOx and Ga and the occurrence of chemical segregation at the liquid alloy surface.

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Wiertlewski, Michaël, Rebecca Fenton Friesen e J. Edward Colgate. "Partial squeeze film levitation modulates fingertip friction". Proceedings of the National Academy of Sciences 113, n. 33 (1 agosto 2016): 9210–15. http://dx.doi.org/10.1073/pnas.1603908113.

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When touched, a glass plate excited with ultrasonic transverse waves feels notably more slippery than it does at rest. To study this phenomenon, we use frustrated total internal reflection to image the asperities of the skin that are in intimate contact with a glass plate. We observed that the load at the interface is shared between the elastic compression of the asperities of the skin and a squeeze film of air. Stroboscopic investigation reveals that the time evolution of the interfacial gap is partially out of phase with the plate vibration. Taken together, these results suggest that the skin bounces against the vibrating plate but that the bounces are cushioned by a squeeze film of air that does not have time to escape the interfacial separation. This behavior results in dynamic levitation, in which the average number of asperities in intimate contact is reduced, thereby reducing friction. This improved understanding of the physics of friction reduction provides key guidelines for designing interfaces that can dynamically modulate friction with soft materials and biological tissues, such as human fingertips.

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Wu, Chu Han, Liang Chi Zhang, Shan Qing Li, Zheng Lian Jiang e Pei Lei Qu. "Effect of Asperity Plastic Deformation on the Interface Friction in Metal Forming". Key Engineering Materials 626 (agosto 2014): 222–27. http://dx.doi.org/10.4028/www.scientific.net/kem.626.222.

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This paper investigates the effect of the plastic deformation of surface asperities on the interface friction in metal forming involving multi-scale deformation with random surface topography. The equivalent interfacial layer (EIL) introduced by the authors previously was used to integrate the Reynolds equation with the plastic deformation of the randomly distributed surface asperities. The contributions of solid-lubricant interaction, lubricant viscosity and microscopic deformation were therefore included efficiently in a conventional macroscopic finite element analysis. The merit of the method was demonstrated by an investigation into the metal strip rolling, whose friction, lubrication and pressure distribution are otherwise hard to be characterized accurately.

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Komvopoulos, K., e D. H. Choi. "Elastic Finite Element Analysis of Multi-Asperity Contacts". Journal of Tribology 114, n. 4 (1 ottobre 1992): 823–31. http://dx.doi.org/10.1115/1.2920955.

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The plane-strain contact problem of an elastic half-space indented by a nominally flat rigid surface having a finite number of regularly spaced cylindrical asperities is investigated using the finite element method to gain an understanding of the interactions in multi-asperity contacts. The significance of the number and spacing of asperities on the contact behavior at the center and edges of the interfacial region is examined. Subsurface stress fields of multi-asperity contacts are presented for various asperity distributions and indentation depths. Asperity interaction effects are quantified in terms of representative parameters, such as the maximum contact pressure, normal load, and maximum von Mises equivalent stress, normalized with similar quantities of the single-asperity contact problem. These nondimensional parameters are principally affected by the spacing and radius of asperities and secondarily by the indentation depth. Significant deviations from the single-asperity Hertzian solution may be encountered, especially in the neighborhood of asperity contacts, because of the unloading and superposition mechanisms which depend on the distance and radius of asperities and indentation depth. The finite element results are in fair qualitative agreement with the phenomenological behavior and analytical predictions.

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Komvopoulos, K., N. Saka e N. P. Suh. "The Mechanism of Friction in Boundary Lubrication". Journal of Tribology 107, n. 4 (1 ottobre 1985): 452–62. http://dx.doi.org/10.1115/1.3261108.

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The primary friction mechanism between boundary-lubricated sliding surfaces was investigated. Experiments were performed on well-polished aluminum, copper, and chromium using mineral oil lubricant. It was found that the prevailing boundary lubrication model, which is based on the adhesion between asperities and shearing of the lubricant film, cannot account for the formation of plowing grooves on polished surfaces. Scanning electron micrographs of the worn surfaces and surface profiles have shown that plowing is the dominant mechanism of friction in boundary lubrication. Theoretical analysis has shown that the coefficient of friction depends on the sharpness and the size of the entrapped wear debris or the surface asperities, and the interfacial “frictional” conditions. Reasonable agreement was obtained between theoretical and experimental friction coefficients.

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Komvopoulos, K., e W. Yan. "Three-Dimensional Elastic-Plastic Fractal Analysis of Surface Adhesion in Microelectromechanical Systems". Journal of Tribology 120, n. 4 (1 ottobre 1998): 808–13. http://dx.doi.org/10.1115/1.2833783.

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High adhesion is often encountered at contact interfaces of miniaturized devices, known as microelectromechanical systems, due to the development of capillary, electrostatic, and van der Waals attractive forces. In addition, deformation of contacting asperities on opposing surfaces produces a repulsive interfacial force. Permanent surface adhesion (referred to as stiction) occurs when the total interfacial force is attractive and exceeds the micromachine restoring force. In the present study, a three-dimensional fractal topography description is incorporated into an elastic-plastic contact mechanics analysis of asperity deformation. Simulation results revealing the contribution of capillary, electrostatic, van der Waals, and asperity deformation forces to the total interfacial force are presented for silicon/silicon and aluminum/aluminum material systems and different mean surface separation distances. Results demonstrate a pronounced effect of surface roughness on the micromachine critical stiffness required to overcome interfacial adhesion.

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Komvopoulos, K., N. Saka e N. P. Suh. "Plowing Friction in Dry and Lubricated Metal Sliding". Journal of Tribology 108, n. 3 (1 luglio 1986): 301–12. http://dx.doi.org/10.1115/1.3261181.

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Experimental evidence for plowing under dry and lubricated sliding conditions is presented and analytical expressions for the coefficient of friction due to plowing are obtained. The theoretical friction coefficient was found to be a function of the sharpness of the hard asperities, the interfacial “friction” conditions and the shape of the plastic zone. The agreement between theoretical and experimental friction coefficients from lubricated sliding and cutting experiments was remarkably good. The discrepancy between theory and experiment in the case of dry sliding between like metals was shown to be due to plastic deformation of the asperities. Consequently, a different model for plowing was proposed for the case of dry sliding between like metals which produced estimates for the coefficient of friction in fair agreement with the experimental results.

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Takahashi, Yasuo, Terumi Nakamura, Yoshihiro Asakura e Masakatsu Maeda. "Influence of surface asperities on interfacial extension during solid state pressure welding". IOP Conference Series: Materials Science and Engineering 61 (1 agosto 2014): 012001. http://dx.doi.org/10.1088/1757-899x/61/1/012001.

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Maciejewski, Jan, Sebastian Bąk e Paweł Ciężkowski. "Modelling of Rock Joints Interface under Cyclic Loading". Studia Geotechnica et Mechanica 42, n. 1 (19 marzo 2020): 36–47. http://dx.doi.org/10.2478/sgem-2019-0030.

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AbstractThe problem of numerical simulation of the material interface response under monotonic and cyclic loading is of fundamental scientific and engineering importance. In fact, such interfaces occur in most engineering and geotechnical structures. The present work is devoted to the deformational response analysis of contact interfaces under monotonic and cyclic loads. The class of materials includes rock and structural joints, soil structure interfaces, masonry and cementitious joints, localized shear bands and so on.The aim of the proposed model is to simulate the cyclic shear test under constant normal load. The associated dilatancy effect is associated with the configurational effects of asperity interaction or dilatancy of wear debris layer. The large primary asperities are assumed as responsible for interfacial dilation and small size asperities as governing frictional sliding and hysteresis response. The elliptic loading yield function is assumed to translate and rotate during progressive or reverse loading events. The model formulation is discussed and confronted with experimental data.

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De Meyere, Robin M. G., Kay Song, Louise Gale, Stephen Harris, Ian M. Edmonds, Thomas J. Marrow, Eduardo Saiz, Finn Giuliani, David E. J. Armstrong e Oriol Gavaldà-Diaz. "A novel trench fibre push-out method to evaluate interfacial failure in long fibre composites". Journal of Materials Research 36, n. 11 (23 marzo 2021): 2305–14. http://dx.doi.org/10.1557/s43578-021-00153-1.

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AbstractTraditional fibre push-outs for the evaluation of interfacial properties in long fibre ceramic matrix composites present their limitations—solutions for which are addressed in this work by introducing the novel trench push-out test. The trench push-out makes use of a FIB milling system and an SEM in-situ nanoindenter to probe a fibre pushed into a trench underneath, allowing in-situ observations to be directly correlated with micromechanical events. SiCf/BN/SiC composites—candidate material for turbine engines—were used as model materials in this work. Different fibre types (Hi-Nicalon and Tyranno type SA3) were coated with BN interphases, presenting mean interfacial shear stresses of 14 ± 7 MPa and 20 ± 2 MPa, respectively, during fibre sliding. The micromechanical technique enabled visualisation of how defects in the interphase (voids, inclusions & milled notches) or in the fibre (surface asperities, non-uniform coatings) affected the variability of interfacial property measurement. Graphic abstract

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Più fonti

Tesi sul tema "Interfacial asperities"

Shu, Weiwei. "Analogical modelling of frictional slip on faults : implications for induced and triggered seismicity". Electronic Thesis or Diss., Strasbourg, 2024. http://www.theses.fr/2024STRAH004.

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La rugosité multi-échelle de l'interface d'une faille est à l'origine de multiples aspérités qui établissent un ensemble complexe et discret de contacts réels. Puisque les aspérités contrôlent l'initiation et l'évolution du glissement de la faille, il est important d'explorer les relations intrinsèques entre le comportement collectif des aspérités locales et la stabilité frictionnelle de la faille globale. Nous proposons ici une nouvelle approche expérimentale analogique, qui nous permet de capturer l'évolution temporelle du glissement de chaque aspérité sur une interface de faille. Nous constatons que de nombreux événements déstabilisants à l'échelle de l'aspérité locale se sont produits dans la phase de renforcement du glissement, qui est conventionnellement considérée comme le régime stable d'une faille. Nous calculons le couplage intersismique pour évaluer les comportements de glissement des aspérités pendant la phase de renforcement du glissement. Nous montrons que le couplage intersismique peut être affecté par les interactions élastiques entre les aspérités par l'intermédiaire de la matrice molle encastrée. Les lois d'échelle des événements naturels de glissement lent sont reproduites par notre configuration, en particulier l'échelle moment-durée
The multi-scale roughness of a fault interface is responsible for multiple asperities that establish a complex and discrete set of real contacts. Since asperities control the initiation and evolution of the fault slip, it is important to explore the intrinsic relationships between the collective behavior of local asperities and the frictional stability of the global fault. Here we propose a novel analog experimental approach, which allows us to capture the temporal evolution of the slip of each asperity on a faulting interface. We find that many destabilizing events at the local asperity scale occurred in the slip-strengthening stage which is conventionally considered as the stable regime of a fault. We compute the interseismic coupling to evaluate the slipping behaviors of asperities during the slip-strengthening stage. We evidence that the interseismic coupling can be affected by the elastic interactions between asperities through the embedding soft matrix. Scaling laws of natural slow slip events are reproduced by our setup in particular the moment-duration scaling

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Capitoli di libri sul tema "Interfacial asperities"

"predicting the permissible external loading that a diamond-coated cutting tool can withstand without premature de-bonding. 3.1.6. Wear mechanisms. The failure of CVD diamond-coated inserts during machining can be in the form of flaking (interfacial failure) or abrasive wear (gradual cohesive failure) [22]. Ideally, a test of superb adhesion is when the diamond coating fully deteriorates by wear rather than flaking. Flaking will occur primarily due to poor adhesion between the diamond coating and the carbide substrate [6]. Therefore, flaking is clearly undesirable because the benefit of using a diamond coating is lost, except for the chip breaking assistance of faceted diamond crystals at the rake surface [29, 75]. If the adhesion strength of the CVD diamond coating is sufficient to withstand the machining stresses, then the abrasive action between the workpiece material and the diamond coating becomes the primary failure mechanism. Unless the CVD diamond coating is polished, a two-step wear mechanism is ex pected to occur. The first step is caused by the initial high surface roughness of the CVD diamond coating in which crack initiation occurs at the surface. The mecha nism that describes such behavior was proposed by Gunnars and Alahelisten [56]. They described a three-zone wear model as shown in Fig. 6. In this model, the role of residual stresses becomes significant in controlling crack propagation from the surface to the interface that could lead to interface failure (flaking). As outlined earlier, the high total compressive residual stress present in CVD diamond coatings on carbide inserts was assumed to be biaxial and oriented parallel to the interface. Wear starts to occur at the surface, which, because of geometry, allows stress to relax. A crack is more likely to initiate at protruding grains in zone I and propa gate preferentially along the (111) easy cleavage planes of diamond. The geometry at deeper depths, however, prevents the compressive residual stress from relaxing. Therefore, as the crack propagates deeper in the coating, it encounters higher com pressive stresses that cause the cracks to redirect their paths deviating from cleavage planes to a direction parallel to the interface in region II. The high compressive stress now causes cracks to propagate fast parallel to the interface resulting in a smooth surface in region III. Due to the smoother surface, fewer asperities will be present and it becomes harder to nucleate cracks." In Adhesion Aspects of Thin Films, Volume 1, 100–139. CRC Press, 2014. http://dx.doi.org/10.1201/b11971-20.

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Atti di convegni sul tema "Interfacial asperities"

Jayadeep, U. B., R. Krishna Sabareesh, R. Nirmal, K. V. Rijin e C. B. Sobhan. "Molecular Dynamics Modeling of the Effect of Thermal Interface Material on Thermal Contact Conductance". In ASME 2008 First International Conference on Micro/Nanoscale Heat Transfer. ASMEDC, 2008. http://dx.doi.org/10.1115/mnht2008-52204.

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Thermal contact conductance is used to indicate the resistance offered by a contact interface to the flow of heat. When an interface material is applied as nano-layered coatings on super-finished contacting surfaces, the possibility of size effects necessitates the use of a discrete computation method for its analysis. Hence, a methodology is proposed which utilizes Molecular Dynamics (MD) simulations to obtain the size affected thermal conductivity of the interfacial layer, which in turn characterizes the thermal contact conductance behavior. Molecular Dynamics codes have been developed, making use of Sutton-Chen many-body potential, suitable for metallic materials. The model includes the asperities at the contact interface, assuming the asperities to be of a simplified geometry. The paper also presents the validation of the codes developed, and parametric studies on the effect of temperature, number of asperities and the material used for thermal interface coating on the size-affected interfacial conductivity.

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Jiang, Jishen, Bingqian Xu, Weizhe Wang, Richard Amankwa Adjei, Xiaofeng Zhao e Yingzheng Liu. "FE Analysis of the Effects of TGO Thickness and Interface Asperity on the Cracking Behavior Between the TGO and the Bond Coat". In ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/gt2016-56755.

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Finite element simulations based on an interface cohesive zone model (CZM) have been developed to mimic the interfacial cracking behavior between the α-Al2O3 thermally grown oxide (TGO) and the aluminum rich Pt–Al metallic bond coat (BC) during cooling from high temperature to ambient temperature. A two dimensional half-periodic sinusoidal geometry corresponding to interface undulation is modelled. The effects of TGO thickness and interface asperity on the stress distribution and the cracking behavior are examined by parametric studies. The simulation results show that cracking behavior due to residual stress and interface asperity during cooling process leads to stress redistribution around the rough interface. The TGO thickness has strong influence on the maximum tensile stress of TGO and the interfacial crack development. For the sinusoidal asperities, there exist a critical amplitude above which interfacial cracking is energetically favored. For any specific TGO thickness, crack initiation is dominated by the amplitude while crack propagation is restricted to the combine actions of the wavelength and the amplitude of the sinusoidal asperity.

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Jeng, Yeau-Ren, e Pay-Yau Huang. "A Material Removal Rate Model Considering Interfacial Micro-Contact Wear Behavior for Chemical Mechanical Polishing". In World Tribology Congress III. ASMEDC, 2005. http://dx.doi.org/10.1115/wtc2005-63260.

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Chemical Mechanical Polishing (CMP) is a highly effective technique for planarizing wafer surfaces. Consequently, considerable research has been conducted into its associated material removal mechanisms. The present study proposes a CMP material removal rate model based upon a micro-contact model which considers the effects of the abrasive particles located between the polishing interfaces, thereby the down force applied on the wafer is carried both by the deformation of the polishing pad asperities and by the penetration of the abrasive particles. It is shown that the current theoretical results are in good agreement with the experimental data published previously. In addition to such operational parameters as the applied down force, the present study also considers consumable parameters rarely investigated by previous models based on the Preston equation, including wafer surface hardness, slurry particle size, and slurry concentration. This study also provides physical insights into the interfacial phenomena not discussed by previous models, which ignored the effects of abrasive particles between the polishing interfaces during force balancing.

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Dini, Daniele. "Between Continuum and Atomistic Contact Mechanics: Could We Bridge the Gap?" In ASME/STLE 2007 International Joint Tribology Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/ijtc2007-44446.

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Recently various attempts have been made to compare continuum contact mechanics to atomistic simulations. The general conclusion of these studies is that continuum mechanics is not adequate to study nanoscopic interactions. Although the use of continuum mechanics at the nanometre scale has a number of limitations, some of the results obtained at atomic level using atomistic simulations can be explained at the continuum level by modelling the interacting surfaces as idealised rough contacts. This will be explicitly proven in this paper. The interfacial contact pressure distribution is found for a sphere pressed onto an elastically similar half-space whose surface is populated by a uniform array of spherical asperities (here representing individual atoms). Details of the load suffered by asperities in the contact disk, together with the effects of the roughness on the overall tangential compliance and the frictional energy losses, are found using a recently proposed technique [1]. Results obtained at continuum level are then generalised and compared to those reported in the literature at atomic level. It is shown that the use of the rough contact idealisation described here is capable of reconciling continuum mechanics and atomistic simulations by capturing some of the features that cannot be captured by the means of conventional Hertzian theory.

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Xiao, Huifang, Yunyun Sun, Xiaojun Zhou e Zaigang Chen. "Study on the Normal Contact Stiffness of Rough Surface in Mixed Lubrication". In ASME 2018 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/detc2018-85034.

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In this paper, a general contact stiffness model is proposed to study the mixed lubricated contact between a rough surface and a rigid flat plate, which is the equivalent model for the contact between two rough surfaces and is the general case for engineering contact interfaces. The total interfacial contact stiffness is composed of the dry rough surface contact stiffness and the liquid lubricant contact stiffness. The GW model is used for surface topography description and the contact stiffness of a single asperity is derived from the Hertz contact theory. The whole dry rough contact stiffness is obtained by multiple the single asperity contact stiffness with the number of contact asperities, which is derived based on the statistical model. The liquid film stiffness is derived based on a spring model. The stiffness contributions from the asperity contact part and lubricant layer part are separated and analyzed.

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DelRio, Frank W., Maarten P. de Boer, Leslie M. Phinney, Chris J. Bourdon e Martin L. Dunn. "Van der Waals and Capillary Adhesion of Microelectromechanical Systems". In ASME 2006 International Mechanical Engineering Congress and Exposition. ASMEDC, 2006. http://dx.doi.org/10.1115/imece2006-15169.

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Interfacial adhesion is an important factor in determining the performance and reliability of microelectromechanical systems (MEMS). Van der Waals dispersion forces are the dominant adhesion mechanism in the low relative humidity (RH) regime. At small roughness values, adhesion is mainly due to van der Waals dispersion forces acting across extensive non-contacting areas and is related to 1/Dave2, where Dave is the average surface separation. These contributions must be considered due to the close proximity of the surfaces, which is a result of the planar deposition technology. At large roughness values, van der Waals forces at contacting asperities become the dominating contributor to the adhesion. Capillary condensation of water has a significant effect on rough surface adhesion in the moderate to high RH regime. Above a threshold RH, which is a function of the surface roughness, the adhesion jumps due to meniscus formation at the interface and increases rapidly towards the upper limit of Γ=2 γcos θ=144 mJ/m2, where γ is the liquid surface energy and θ is the contact angle.

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