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Steven Danyluk - One of the best experts on this subject based on the ideXlab platform.
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Contact mechanics and lubrication hydrodynamics of chemical mechanical polishing
Journal of The Electrochemical Society, 1999Co-Authors: John A Tichy, Joseph A Levert, Lei Shan, Steven DanylukAbstract:A preliminary model for the Contact mechanics and fluid mechanics of the chemical mechanical polishing process is presented. Only the basic equations of Elastic Contact surface mechanics and hydrodynamic lubrication are required. Although the model is highly idealized, no ad hoc assumptions or adjustable parameters are required. Some new experimental results are presented, reinforcing the counterintuitive experimental determination of suction fluid pressure below the pad. The model correctly predicts the magnitude of the suction pressure and the effect of load, speed, and roughness.
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Contact mechanics and lubrication hydrodynamics of chemical mechanical polishing
Journal of The Electrochemical Society, 1999Co-Authors: John A Tichy, Joseph A Levert, Lei Shan, Steven DanylukAbstract:A preliminary model for the Contact mechanics and fluid mechanics of the chemical mechanical polishing process is presented. Only the basic equations of Elastic Contact surface mechanics and hydrodynamic lubrication are required. Although the model is highly idealized, no ad hoc assumptions or adjustable parameters are required. Some new experimental results are presented, reinforcing the counterintuitive experimental determination of suction fluid pressure below the pad. The model correctly predicts the magnitude of the suction pressure and the effect of load, speed, and roughness. © 1999 The Electrochemical Society. All rights reserved.
J R Barber - One of the best experts on this subject based on the ideXlab platform.
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the use of static reduction in the finite element solution of two dimensional frictional Contact problems
Proceedings of the Institution of Mechanical Engineers Part C: Journal of Mechanical Engineering Science, 2014Co-Authors: A Thaitirarot, D.a. Hills, R C Flicek, J R BarberAbstract:In this paper, detailed instructions are given for performing static reduction on a finite element description of an Elastic Contact problem, thus reducing the dimensionality of the problem to the set of Contact nodes alone. This significantly reduces the computational time for the solution to evolutionary Contact problems and also gives the user greater control over the detailed implementation of the Contact and friction laws. The reduced stiffness matrix is also an essential ingredient in the determination of the critical coefficient of friction for the problem to be well posed, and it facilitates the determination of the conditions under which a frictional system may shake down under periodic loading.
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frictional Elastic Contact with periodic loading
International Journal of Solids and Structures, 2011Co-Authors: J R Barber, M Davies, D.a. HillsAbstract:Quasi-static frictional Contact problems for bodies of fairly general profile that can be represented as half planes can be solved using an extension of the methods of Ciavarella and Jager. Here we consider the tangential traction distributions developed when such systems are subjected to loading that varies periodically in time. It is shown that the system reaches a steady state after the first loading cycle. In this state, part of the Contact area (the permanent stick zone) experiences no further slip, whereas other points may experience periods of stick, slip and/or separation. We demonstrate that the extent of the permanent stick zone depends only on the periodic loading cycle and is independent of the initial conditions or of any initial transient loading phase. The exact traction distribution in this zone does depend on these factors, but the resultant of these tractions at any instant in the cycle does not. The tractions and slip velocities at all points outside the permanent stick zone are also independent of initial conditions, confirming an earlier conjecture that the frictional energy dissipation per cycle in such systems depends only on the periodic loading cycle. We also show that these parameters remain unchanged if the loading cycle is changed by a time-independent tangential force, provided this is not so large as to precipitate a period of gross slip (sliding).
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shakedown in Elastic Contact problems with coulomb friction
International Journal of Solids and Structures, 2007Co-Authors: Anders Klarbring, M Ciavarella, J R BarberAbstract:Elastic systems with frictional interfaces subjected to periodic loading are sometimes predicted to ‘shake down’ in the sense that frictional slip ceases after the first few loading cycles. The similarities in behaviour between such systems and monolithic bodies with Elastic–plastic constitutive behaviour have prompted various authors to speculate that Melan’s theorem might apply to them – i.e., that the existence of a state of residual stress sufficient to prevent further slip is a sufficient condition for the system to shake down. In this paper, we prove this result for ‘complete’ Contact problems in the discrete formulation (i) for systems with no coupling between relative tangential displacements at the interface and the corresponding normal Contact tractions and (ii) for certain two-dimensional problems in which the friction coefficient at each node is less than a certain critical value. We also present counter-examples for all systems that do not fall into these categories, thus giving a definitive statement of the conditions under which Melan’s theorem can be used to predict whether such a system will shake down. � 2007 Elsevier Ltd. All rights reserved.
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Elastic Contact stiffness and Contact resistance for the weierstrass profile
Journal of The Mechanics and Physics of Solids, 2004Co-Authors: Michele Ciavarella, G Murolo, G Demelio, J R BarberAbstract:The Weierstrass series comprises a system of superposed self-affine sine waves that can be used to define a simple idealization of a two-dimensional fractal rough surface profile. The load–compliance relation for the Contact of this profile with a rigid plane is here estimated using Westergaard's solution for the Contact of a single sine wave with a plane and various approximations concerning the interaction of the different terms in the series. These approximations are compared with a numerical solution for the Contact of the profile defined by the first few terms of the series. Once the load–compliance relation is established, the electrical Contact resistance can be determined, using an analogy between the conduction and incremental Elastic Contact problems. The results show that these simple estimates give quite good predictions of the relations between load, compliance and Contact resistance. They also confirm that these relations are largely determined by the coarse scale features of the surface profile, in contrast to the predictions of classical asperity model theories.
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linear Elastic Contact of the weierstrass profile
Proceedings of The Royal Society A: Mathematical Physical and Engineering Sciences, 2000Co-Authors: Michele Ciavarella, G Demelio, J R Barber, Yong Hoon JangAbstract:A Contact problem is considered in which an Elastic half–plane is pressed against a rigid fractally rough surface, whose profile is defined by a Weierstrass series. It is shown that no applied mean pressure is sufficiently large to ensure full Contact and indeed there are not even any Contact areas of finite dimension — the Contact area consists of a set of fractal character for all values of the geometric and loading parameters. A solution for the partial Contact of a sinusoidal surface is used to develop a relation between the Contact pressure distribution at scale n − 1 and that at scale n . Recursive numerical integration of this relation yields the Contact area as a function of scale. An analytical solution to the same problem appropriate at large n is constructed following a technique due to Archard. This is found to give a very good approximation to the numerical results even at small n , except for cases where the dimensionless applied load is large. The Contact area is found to decrease continuously with n , tending to a power–law behaviour at large n which corresponds to a limiting fractal dimension of (2 − D ), where D is the fractal dimension of the surface profile. However, it is not a ‘simple’ fractal, in the sense that it deviates from the power–law form at low n , at which there is also a dependence on the applied load. Contact segment lengths become smaller at small scales, but an appropriately normalized size distribution tends to a limiting function at large n . † The authors dedicate this paper to the memory of Dr J. F. Archard, 1918–1989.
Andreas A Polycarpou - One of the best experts on this subject based on the ideXlab platform.
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effect of asperity interactions on rough surface Elastic Contact behavior hard film on soft substrate
Tribology International, 2010Co-Authors: Chang-dong Yeo, Raja R Katta, Jungkyu Lee, Andreas A PolycarpouAbstract:Abstract An improved Elastic micro-Contact model of rough surfaces accounting for asperity interactions is proposed. The Contact behavior of a single asperity system is composed of a stiffer hemi-spherical asperity deformation and bellowing softer substrate deformation, which is then extended to rough surface Contact including asperity interactions. Using the solution of substrate deformation, normal positions of individual asperities are adjusted during quasi-static Contact, from which surface interactive forces are obtained. Analytical simulations are performed using the proposed rough surface Contact model, whose results are compared to Greenwood–Williamson-based models and with experimental measurements.
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Improved Elastic Contact Model Accounting for Asperity and Bulk Substrate Deformation
Tribology Letters, 2009Co-Authors: Chang-dong Yeo, Raja R Katta, Andreas A PolycarpouAbstract:An improved Elastic Contact model for a single asperity system is proposed accounting for both the effects of bulk substrate and asperity deformations. The asperity Contact stiffness is based on the Hertzian solution for spherical Contact, and the bulk substrate stiffness on the solution of Hertzian pressure on a circular region of the Elastic half-space. Depending on the magnitude of the applied load, as well as the geometrical and physical properties of the asperity and bulk materials, the bulk substrate could have considerable contribution to the overall Contact stiffness. The proposed single asperity model is generalized using two parameters based on physical and geometrical properties, and is also verified using finite element analysis. A parametric study for a practical range of geometric and physical parameters is performed using finite element analysis to determine the range of validity of the proposed model and also to compare it with the Hertz Contact model. The single asperity model is extended to rough surfaces in Contact and the Contact stiffness from the proposed model and the simpler Greenwood–Williamson asperity model are compared to experimental measurements.
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Elastic Contact Model Accounting for Both Asperity and Substrate Compliance With Application to Patterned Media
ASME STLE 2007 International Joint Tribology Conference Parts A and B, 2007Co-Authors: Chang-dong Yeo, Andreas A PolycarpouAbstract:An improved Elastic Contact stiffness model for a single asperity system is proposed to account for the effects of both bulk substrate and asperity deformations between two Contacting surfaces. Depending upon the applied load, as well as the geometrical and physical properties of the asperity and bulk material, the bulk substrate can have a considerable contribution to the overall Contact stiffness. Finite element analysis is performed to verify the proposed analytical model. The single asperity model is extended to rough surfaces in Contact. The Contact stiffness values from the proposed model are compared to those from the GW model. The proposed Contact model can be directly relevant to analyze the Contact behavior of modern patterned media.© 2007 ASME
I Etsion - One of the best experts on this subject based on the ideXlab platform.
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electrical resistance model of a bilayer coated spherical Contact
IEEE Transactions on Components Packaging and Manufacturing Technology, 2018Co-Authors: Oleg Korchevnik, Roman Goltsberg, Y Kligerman, I EtsionAbstract:A finite-element analysis was used to investigate the Elastic Contact of a bilayered coated sphere compressed by a rigid flat, under the normal loading and “slip” Contact condition. A bilayered coating consisting of a hard outer layer and a soft interlayer relative to the substrate was studied. An electrical analysis was performed on the deformed coated sphere to investigate the effect of the thickness of both the hard and soft coatings and their material properties on the electrical Contact resistance (ECR). It was found that for any given load, under fully Elastic Contact, proper material and thickness of the soft interlayer can increase the Contact area by up to 35% and reduce the electrical resistance by up to 75%, compared to a reference case without the soft interlayer. Increasing the outer hard coating thickness increases the ECR. The increase in the Contact area was found to have a secondary effect on the reduction of the Contact resistance compared to the effect of the material’s conductivity.
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Contact area and maximum equivalent stress in Elastic spherical Contact with thin hard coating
Tribology International, 2016Co-Authors: Roman Goltsberg, I EtsionAbstract:Abstract A finite element analysis was used in order to investigate the Elastic Contact of a sphere with a thin hard coating compressed by a rigid flat. A proper normalization of the dimensional Contact parameters, such as the Contact area, load, interference and maximum equivalent von Mises stresses in the coating and in the substrate was used to obtain a universal model of the Elastic Contact. This model provides empirical relations between these Contact parameters for a wide range of mechanical and geometrical properties, which are different from the classical Hertz solution for a homogeneous sphere compressed by a rigid flat. The model also introduces a new approach for calculating the limit of Elasticity in the coated system.
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a universal model for the load displacement relation in an Elastic coated spherical Contact
Wear, 2015Co-Authors: Roman Goltsberg, I EtsionAbstract:Abstract A finite element analysis was used in order to investigate the Elastic Contact of a coated sphere compressed by a rigid flat. Different coating and substrate geometrical and mechanical properties were analyzed to obtain a universal dimensionless model for the load–displacement relation. Both hard and soft coatings were considered. Dimensionless parameters, which control the behavior of the Elastically loaded coated sphere, were identified. A proper normalization of the dimensional load and displacement was found resulting in a universal model. This model also provides a universal expression for the effective modulus of Elasticity that is based only on mechanical properties of the coating and the substrate.
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The Effect of Determining Topography Parameters on Analyzing Elastic Contact Between Isotropic Rough Surfaces
Journal of Tribology-transactions of The Asme, 2012Co-Authors: Gorakh Pawar, I Etsion, Pawel Pawlus, Bart RaeymaekersAbstract:Elastic Contact between two computer-generated isotropic rough surfaces is studied. First the surface topography parameters, including the asperity density, mean summit radius, and standard deviation of asperity heights of the equivalent rough surface, are determined using an 8-nearest neighbor summit identification scheme. Second, many cross-sections of the equivalent rough surface are traced and their individual topography parameters are determined from their corresponding spectral moments. The topography parameters are also obtained from the average spectral moments of all cross-sections. The asperity density is found to be the main difference between the summit identification scheme and the spectral moments method. The Contact parameters, such as the number of Contacting asperities, real area of Contact, and Contact load for any given separation between the equivalent rough surface and a rigid flat, are calculated by summing the contributions of all the Contacting asperities using the summit identification model. These Contact parameters are also obtained with the Greenwood-Williamson (GW) model using the topography parameters from each individual cross-section and from the average spectral moments of all crosssections. Three different surfaces characterized by a different autocorrelation length, and three different sampling intervals were used to study how the method to determine topography parameters affects the resulting Contact parameters.
John A Tichy - One of the best experts on this subject based on the ideXlab platform.
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Contact mechanics and lubrication hydrodynamics of chemical mechanical polishing
Journal of The Electrochemical Society, 1999Co-Authors: John A Tichy, Joseph A Levert, Lei Shan, Steven DanylukAbstract:A preliminary model for the Contact mechanics and fluid mechanics of the chemical mechanical polishing process is presented. Only the basic equations of Elastic Contact surface mechanics and hydrodynamic lubrication are required. Although the model is highly idealized, no ad hoc assumptions or adjustable parameters are required. Some new experimental results are presented, reinforcing the counterintuitive experimental determination of suction fluid pressure below the pad. The model correctly predicts the magnitude of the suction pressure and the effect of load, speed, and roughness.
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Contact mechanics and lubrication hydrodynamics of chemical mechanical polishing
Journal of The Electrochemical Society, 1999Co-Authors: John A Tichy, Joseph A Levert, Lei Shan, Steven DanylukAbstract:A preliminary model for the Contact mechanics and fluid mechanics of the chemical mechanical polishing process is presented. Only the basic equations of Elastic Contact surface mechanics and hydrodynamic lubrication are required. Although the model is highly idealized, no ad hoc assumptions or adjustable parameters are required. Some new experimental results are presented, reinforcing the counterintuitive experimental determination of suction fluid pressure below the pad. The model correctly predicts the magnitude of the suction pressure and the effect of load, speed, and roughness. © 1999 The Electrochemical Society. All rights reserved.