The Effects of Interfacial Particles on the Contact of an Elastic Sphere With a Rigid Flat Surface

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Dinçer Bozkaya ◽  
Sinan Müftü
Keyword(s):  
Contact Force ◽  
Removal Rate ◽  
Asperity Contact ◽  
Hertz Contact ◽  
Body Contact ◽  
Abrasive Particles ◽  
Push Down ◽  
Three Body ◽  
Maximum Contact

In chemical mechanical polishing (CMP), a rigid wafer is forced on a rough elastomeric polishing pad, while a slurry containing abrasive particles flows through the interface. One of the important factors that influence the material removal rate in CMP is the magnitude of contact force transmitted to the abrasive particles trapped at the contact interface. The total push-down force is distributed to the direct contact between the wafer and the pad, and to the three-body contact between the wafer, the pad, and the abrasive particles. The presence of the abrasive particles alters the asperity contact, which otherwise can be described by Hertz contact relationships. In this study, the effect of the interfacial particles on the single asperity contact is investigated. An approach used by Greenwood and Tripp (1967, “The Elastic Contact of Rough Spheres,” ASME J. Appl. Mech., 34, pp. 153–160) to study the contact of rough spheres is utilized since the presence of the particles provides a rough character to the contact. The results show that the contact behavior becomes non-Hertzian with decreasing contact force and increasing elastic modulus, particle size, and particle concentration. The role of the interfacial particles is to spread the contact over a larger area while lowering the maximum contact pressure at the center of contact predicted by Hertz contact. The conditions required to transfer the contact force on the particles effectively are also described.

Nano-Tribological Analysis by Molecular Dynamics Simulation—A Review

2006 ◽  
Vol 3 (2) ◽  
pp. 167-188 ◽  
Author(s):  
L. C. Zhang ◽  
K. Mylvaganam
Keyword(s):  
Molecular Dynamics ◽  
Large Scale ◽  
Surface Force ◽  
Atomic Scale ◽  
Dynamics Simulation ◽  
Asperity Contact ◽  
Dynamics Modeling ◽  
Body Contact ◽  
Cutting Regimes ◽  
Three Body

The advent of super computers for large scale atomic simulations and the invention of proximal testing devices such as atomic force microscope, friction force microscope, surface force apparatus, nanoScratcher etc., have led to the development of micro- and nano-tribology. This paper reviews some fundamental concepts and steps involved in molecular dynamics modeling of nanotribology together with some significant aspects such as the mechanisms of wear and friction, the scale effect of asperity contact size on friction, and the deformation induced by two-body and three-body contact sliding on the atomic scale with a focus on the authors' work on copper and silicon. Studies on diamond-copper sliding reveal that there exist four distinct regimes of deformation, and that no-wear deformation can be achieved by using a lower sliding speed, a smaller tip radius and a better lubrication. The variation of the frictional force is a function of contact area in all regimes except that in the cutting regime where the conventional friction law still holds. Investigations into the diamond-silicon sliding show that the amorphous phase transformation is the main deformation in silicon. In a two-body contact sliding, the deformation of silicon falls into no-wear, adhering, ploughing, and cutting regimes while in a three-body sliding it falls into no-wear, condensing, adhering, ploughing and no-damage wear regimes.

scholarly journals Experimental study on tribological characteristics in coke powder lubrication

2020 ◽  
Vol 12 (8) ◽  
pp. 168781402094045
Author(s):  
Jin Xiang ◽  
Zheng Yan
Keyword(s):  
Sliding Friction ◽  
Coke Oven ◽  
Powder Layer ◽  
Lower Velocity ◽  
Body Contact ◽  
Powder Lubrication ◽  
Lubrication Characteristics ◽  
Three Body ◽  
Coke Powder

Pushing coke is an important process in coke oven production. In the process of pushing coke, under the three-body contact state of steel, coke powder, and refractory brick, coke powder plays an important role in lubrication. In this article, a study on the macro- and micro-behavior and mechanism of coke powder lubrication is carried out through tribological tests. The results show that in the process of sliding friction, coke powder plays a role of lubrication through forming a powder layer and shearing occurred inside the powder layer. The load keeps at 5 MPa, under the lower velocity, the powder layer is thinner and delamination occurred in local position. While under the higher velocity, the coke powder can form a compact and complete powder layer and exhibit better lubrication characteristics. However, when the velocity increases to 0.52 m/s, the continuous powder layer is not formed, so the friction coefficient is higher, the frictional surface wears seriously and results in vibration to occur. The velocity keeps at 0.40 m/s, and the powder layer inclines to deteriorate under higher load. When the load increases to 20 MPa, a part of the powder layer is damaged, and severe wear occurs on the surface.

scholarly journals Two- and three-body contacts in the unitary Bose gas

Science ◽  
2017 ◽  
Vol 355 (6323) ◽  
pp. 377-380 ◽  
Author(s):  
Richard J. Fletcher ◽  
Raphael Lopes ◽  
Jay Man ◽  
Nir Navon ◽  
Robert P. Smith ◽  
...  
Keyword(s):  
Bose Gas ◽  
Many Body ◽  
Body Contact ◽  
Wide Range ◽  
Pairwise Correlations ◽  
Efimov Physics ◽  
Many Body Systems ◽  
Three Body ◽  
Profound Insight

In many-body systems governed by pairwise contact interactions, a wide range of observables is linked by a single parameter, the two-body contact, which quantifies two-particle correlations. This profound insight has transformed our understanding of strongly interacting Fermi gases. Using Ramsey interferometry, we studied coherent evolution of the resonantly interacting Bose gas, and we show here that it cannot be explained by only pairwise correlations. Our experiments reveal the crucial role of three-body correlations arising from Efimov physics and provide a direct measurement of the associated three-body contact.

Effect of shape/size and distribution of microgeometries of textures on tribo-performance of crankpin bearing

2021 ◽  
pp. 135065012110105
Author(s):  
Nguyen Van Liem ◽  
Wu Zhenpeng ◽  
Jiao Renqiang
Keyword(s):  
Friction Coefficient ◽  
Friction Force ◽  
Contact Force ◽  
Distribution Density ◽  
Hydrodynamic Lubrication ◽  
Operating Conditions ◽  
Asperity Contact ◽  
Combined Model ◽  
Obvious Effect ◽  
Area Density

The effect of the shape/size and distribution of microgeometries of textures on improving the tribo-performance of crankpin bearing is proposed. Based on a combined model of the slider-crank mechanism dynamic and hydrodynamic lubrication, the distribution density, area density, and shape of spherical textures, square-cylindrical textures, wedge-shaped textures, and a hybrid between spherical texture and square-cylindrical texture on the crankpin bearing's tribo-performance are investigated under different operating conditions of the engine. The tribological characteristic of the crankpin bearing is then evaluated via the indexes of the oil film pressure p, asperity contact force, friction force, and friction coefficient of the crankpin bearing. The research results show that the distribution density with n = 12 and m = 6, and area density with α = 30% of various microtextures have an obvious effect on ameliorating the crankpin bearings tribo-performance. Concurrently, at the mixed lubrication region, the shape of the square-cylindrical texture on improving the tribo-performance is better than the other shapes of the spherical texture, wedge-shaped texture, and spherical and square-cylindrical texture. Particularly, all the average values of the asperity contact force, friction force, and friction coefficient with a square-cylindrical texture are significantly reduced by 14.6%, 19.5%, and 34.5%, respectively, in comparison without microtextures. Therefore, the microtextures of the spherical texture applied on the bearing surface can contribute to enhance the durability and decrease the friction power loss of the engine.

Study of Advanced Technologies of METs for Herbicides Wastewater Treatment with High Salinity

2013 ◽  
Vol 777 ◽  
pp. 326-329
Author(s):  
Tao Li Song ◽  
Xue Nong Yi ◽  
Zhi Qing Li ◽  
Xin Jin
Keyword(s):  
Wastewater Treatment ◽  
High Salinity ◽  
Removal Rate ◽  
Advanced Technologies

Experiments were conducted to study the role of enhanced micro-electrolysis techniques (METs) in treatment of s-atrazine wastewater, regarding atrazine production wastewater as the object of this research. The intensified METs methods included O3and ultrasound (US). With O3METs technology, a better result could be achieved under weak acidity condition. The highest removal rate of TOC reached 18.7%. US before METs could gain higher removal rate of 38.7% compared to the rate of 27.8% by US in METs.

Approximate Macroscale Constitutive Relations Using a Finite Element Based Constitutive Equations for Microscale Contact

2008 ◽  
Author(s):  
Ali Sepehri ◽  
Kambiz Farhang
Keyword(s):  
Finite Element ◽  
Contact Force ◽  
Rough Surfaces ◽  
Constitutive Relations ◽  
Cumulative Effect ◽  
Element Model ◽  
Tangential Component ◽  
Total Force ◽  
Asperity Contact ◽  
Elastic Plastic

Three dimensional elastic-plastic contact of two nominally flat rough surfaces is considered. Equations governing the shoulder-shoulder contact of asperities are derived based on the asperity-asperity constitutive relations from a finite element model of their elastic-plastic interaction. Shoulder-shoulder asperity contact yields a slanted contact force consisting of both tangential (parallel to mean plane) and normal components. Multiscale modeling of the elastic-plastic rough surface contact is presented in which asperity-level FE-based constitutive relations are statistically summed to obtain total force in the normal and tangential direction. The equations derived are in the form of integral functions and provide expectation of contact force components between two rough surfaces. An analytical fusion technique is developed to combine the piecewise asperity level constitutive relations. This is shown to yield upon statistical summation the cumulative effect resulting in the contact force between two rough surfaces with two components, one in the normal direction and a half-plane tangential component.

ZERO AND FINITE TEMPERATURE STUDY OF SINGLE FULLERENE CAGES AND CARBON “ONIONS” — GEOMETRY AND SHAPE

1993 ◽  
Vol 07 (29n30) ◽  
pp. 1883-1895 ◽  
Author(s):  
A. MAITI ◽  
C.J. BRABEC ◽  
J. BERNHOLC
Keyword(s):  
Interatomic Potential ◽  
Critical Size ◽  
Tight Binding ◽  
Configurational Entropy ◽  
Electronic Structure Calculations ◽  
Carbon Onions ◽  
Three Body ◽  
Structure Calculations ◽  
Scaling Arguments

Scaling arguments are used to show that above a critical size of several thousand atoms, there is a stability crossover from single to multilayer cages. Conjugate gradient minimization using a classical three-body interatomic potential, as well as tight-binding electronic structure calculations yield ground-state configurations for large fullerene shells that are polyhedral with clearly faceted geometry. The structure, energetics and configurational entropy associated with low-energy defects are calculated and the number of defects estimated as a function of temperature. The role of these thermally generated defects on the shape of large fullerenes is investigated in order to explain the nearly spherical shapes of the newly discovered carbon “onions”.

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