Role of friction modifiers on the tribological performance of hypereutectic Al–Si alloy lubricated in boundary conditions

Although previous researchers have demonstrated that people often prefer potential rather than achievement when evaluating other people or products, few have focused on the boundary conditions on this effect. We proposed that the preference for potential would emerge when individuals’ perception of economic mobility was high, but the preference for achievement would emerge among individuals with low perceptions of economic mobility. Our results showed that people paid more attention to the future (vs. the present) when their perception of economic mobility was high; this, in turn, promoted more favorable reactions toward potential (vs. achievement). Thus, we suggested circumstances under which highlighting a person’s potential for future success is effective and those when it is not effective. Moreover, we revealed the important role of individual perceptions regarding economic mobility in driving this effect.

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Charge algebra in Al(A)dSn spacetimes

Journal of High Energy Physics ◽

10.1007/jhep05(2021)210 ◽

2021 ◽

Vol 2021 (5) ◽

Author(s):

Adrien Fiorucci ◽

Romain Ruzziconi

Keyword(s):

Boundary Conditions ◽

Dirichlet Boundary ◽

Three Dimensional ◽

Dirichlet Boundary Conditions ◽

Boundary Structure ◽

Asymptotic Symmetry ◽

Renormalization Procedure ◽

Field Dependent ◽

Odd Dimensions

Abstract The gravitational charge algebra of generic asymptotically locally (A)dS spacetimes is derived in n dimensions. The analysis is performed in the Starobinsky/Fefferman-Graham gauge, without assuming any further boundary condition than the minimal falloffs for conformal compactification. In particular, the boundary structure is allowed to fluctuate and plays the role of source yielding some symplectic flux at the boundary. Using the holographic renormalization procedure, the divergences are removed from the symplectic structure, which leads to finite expressions. The charges associated with boundary diffeomorphisms are generically non-vanishing, non-integrable and not conserved, while those associated with boundary Weyl rescalings are non-vanishing only in odd dimensions due to the presence of Weyl anomalies in the dual theory. The charge algebra exhibits a field-dependent 2-cocycle in odd dimensions. When the general framework is restricted to three-dimensional asymptotically AdS spacetimes with Dirichlet boundary conditions, the 2-cocycle reduces to the Brown-Henneaux central extension. The analysis is also specified to leaky boundary conditions in asymptotically locally (A)dS spacetimes that lead to the Λ-BMS asymptotic symmetry group. In the flat limit, the latter contracts into the BMS group in n dimensions.

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Effect of Different Lubricating Environment on the Tribological Performance of CNT Filled Glass Reinforced Polymer Composite

Materials ◽

10.3390/ma14112965 ◽

2021 ◽

Vol 14 (11) ◽

pp. 2965

Author(s):

Sandeep Agrawal ◽

Nishant K. Singh ◽

Rajeev Kumar Upadhyay ◽

Gurminder Singh ◽

Yashvir Singh ◽

...

Keyword(s):

Tribological Performance ◽

Hardened Steel ◽

Dry Sliding ◽

Gfrp Composites ◽

Tribological Behaviour ◽

Reinforced Polymer ◽

Steel Surfaces ◽

Lubrication Properties ◽

Scanning Electron

In recent years, the engineering implications of carbon nanotubes (CNTs) have progressed enormously due to their versatile characteristics. In particular, the role of CNTs in improving the tribological performances of various engineering materials is well documented in the literature. In this work, an investigation has been conducted to study the tribological behaviour of CNTs filled with glass-reinforced polymer (GFRP) composites in dry sliding, oil-lubricated, and gaseous (argon) environments in comparison to unfilled GFRP composites. The tribological study has been conducted on hardened steel surfaces at different loading conditions. Further, the worn surfaces have been examined for a particular rate of wear. Field-emission scanning electron (FESEM) microscopy was used to observe wear behaviours. The results of this study explicitly demonstrate that adding CNTs to GFRP composites increases wear resistance while lowering friction coefficient in all sliding environments. This has also been due to the beneficial strengthening and self-lubrication properties caused by CNTs on GFRP composites, according to FESEM research.

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Role of micro-factors on microstructure and on the tribological performance of HVOF coatings: A review

IOP Conference Series Materials Science and Engineering ◽

10.1088/1757-899x/1017/1/012010 ◽

2021 ◽

Vol 1017 (1) ◽

pp. 012010

Author(s):

Alok Vats ◽

Amar Patnaik ◽

M L Meena ◽

Dinesh Shringi

Keyword(s):

Tribological Performance ◽

Hvof Coatings

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Understanding the critical role of boundary conditions in meso-scale finite element simulation of braided composites

Advanced Composites and Hybrid Materials ◽

10.1007/s42114-021-00284-3 ◽

2021 ◽

Author(s):

Zhenqiang Zhao ◽

Peng Liu ◽

Haoyuan Dang ◽

Yang Chen ◽

Chao Zhang ◽

...

Keyword(s):

Finite Element ◽

Boundary Conditions ◽

Finite Element Simulation ◽

Critical Role ◽

Braided Composites ◽

Element Simulation ◽

Meso Scale

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Mechanics of tubular helical assemblies: ensemble response to axial compression and extension

Acta Mechanica Sinica ◽

10.1007/s10409-021-01068-0 ◽

2021 ◽

Author(s):

Jacopo Quaglierini ◽

Alessandro Lucantonio ◽

Antonio DeSimone

Keyword(s):

Boundary Conditions ◽

Elastic Properties ◽

Central Region ◽

Mechanical Response ◽

Different Boundary Conditions ◽

Kirchhoff Rods ◽

Model Versus ◽

The Individual ◽

Opposite Chirality

Abstract Nature and technology often adopt structures that can be described as tubular helical assemblies. However, the role and mechanisms of these structures remain elusive. In this paper, we study the mechanical response under compression and extension of a tubular assembly composed of 8 helical Kirchhoff rods, arranged in pairs with opposite chirality and connected by pin joints, both analytically and numerically. We first focus on compression and find that, whereas a single helical rod would buckle, the rods of the assembly deform coherently as stable helical shapes wound around a common axis. Moreover, we investigate the response of the assembly under different boundary conditions, highlighting the emergence of a central region where rods remain circular helices. Secondly, we study the effects of different hypotheses on the elastic properties of rods, i.e., stress-free rods when straight versus when circular helices, Kirchhoff’s rod model versus Sadowsky’s ribbon model. Summing up, our findings highlight the key role of mutual interactions in generating a stable ensemble response that preserves the helical shape of the individual rods, as well as some interesting features, and they shed some light on the reasons why helical shapes in tubular assemblies are so common and persistent in nature and technology. Graphic Abstract We study the mechanical response under compression/extension of an assembly composed of 8 helical rods, pin-jointed and arranged in pairs with opposite chirality. In compression we find that, whereas a single rod buckles (a), the rods of the assembly deform as stable helical shapes (b). We investigate the effect of different boundary conditions and elastic properties on the mechanical response, and find that the deformed geometries exhibit a common central region where rods remain circular helices. Our findings highlight the key role of mutual interactions in the ensemble response and shed some light on the reasons why tubular helical assemblies are so common and persistent.

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