Elastic Plastic Adhesive Contact Research Articles

Atomistic insights into the loading – Unloading of an adhesive contact: A rigid sphere indenting a copper substrate

A molecular dynamics simulation model is developed to investigate the loading–unloading behavior during nanoindentation of a spherical contact considering material anisotropy and adhesion. A comparison with analytical Hertz solution, JKR and DMT models is performed to determine the differences between macroscale and nanoscale. The single-crystal copper (001) substrate has a sudden jump in contact with the indenter due to adhesion. The simulated critical interference for yielding inception is several orders of magnitude larger than the calculated value using Hertz theory. Plastic yielding caused by intensive dislocation is observed in the sudden load drop region. The JKR and DMT theories used in macro scale are not able to describe accurately the contact behavior in nanoscale. A nearly linear increase in the contact area with the indentation depth is observed in the elastic regime of deformation. The Tabor parameter can be used to evaluate the transition of jump-in or jump-out behavior for the load–displacement curve in an elastic–plastic adhesive contact in nanoscale.

Elastic-Plastic Adhesive Contact of Rough Surfaces Based on Accurate FEA Study Using N-Point Asperity Model

The paper describes a theoretical study of elastic-plastic adhesive contact of rough surfaces based on n-point asperity model and accurate finite element analysis (FEA) of elastic-plastic deformation of single asperity contact. The n-point asperity model developed by Hariri et al (2006) is integrated with the elastic-plastic model of . In this study an attempt is made to extend the work of by incorporating intermediate elastic-plastic regime of deformation. A large range of interference values ranging from fully elastic through elastic-plastic to fully plastic deformation of contacting asperities is considered. The effect of varying load and material parameters is analyzed in terms of well established adhesion index and plasticity index. A comparison between the present analysis with that of model shows significant difference in load–separation behaviour depending on combinations of mean separation, adhesion index and plasticity index.

Adhesion-induced instabilities in elastic and elastic–plastic contacts during single and repetitive normal loading

Adhesive interaction in spherical contacts was modeled with the Lennard-Jones (L-J) potential. Elastic adhesive contact was analyzed by the equivalent system of a rigid sphere with reduced radius of curvature and a half-space of effective elastic modulus. The critical gap at the instant of abrupt surface contact (jump-in) and separation (jump-out) was determined from the deformed surface profile of the elastic half-space and geometrical relationships. A finite element model of a rigid sphere and an elastic–plastic half-space was used to examine elastic–plastic adhesive contact. Surface adhesion was modeled by nonlinear springs with a force–displacement relationship governed by the L-J potential. The evolution of the interfacial force and the central gap distance as well as the occurrence of jump-in and jump-out instabilities were investigated in terms of the Tabor parameter, plasticity parameter, and dimensionless maximum normal displacement. The force–displacement response due to several approach–retraction cycles was interpreted in the context of elastic and plastic shakedown behaviors using dimensionless parameters.

Adhesive contact of curved surfaces

The present study considers an analysis of elastic-plastic contact of rough curved surfaces in the presence of adhesion using the Johnson-Kendall-Roberts model. The mixed asperity contact model for a sphere with rough flats, developed by Kagami et al., is integrated into the elastic-plastic adhesive contact model developed by Roy Chowdhury and Ghosh to consider the loading behaviour in an adhesive contact between a smooth sphere and a rough flat surface. The pressure distributions, contact radius versus load, and compliance versus load behaviour are studied for different conditions that arise because of varying loads, surfaces, and material parameters. Results show that the radius of a curved solid significantly influences the adhesive contact behaviour.

Elastic–plastic adhesive contact of rough surfaces using n-point asperity model

This study considers an analysis of the elastic–plastic contact of rough surfaces in the presence of adhesion using an n-point asperity model. The multiple-point asperity model, developed by Hariri et al (2006 Trans ASME: J. Tribol. 128 505–14) is integrated into the elastic–plastic adhesive contact model developed by Roy Chowdhury and Ghosh (1994 Wear 174 9–19). This n-point asperity model differs from the conventional Greenwood and Williamson model (1966 Proc. R. Soc. Lond. A 295 300–19) in considering the asperities not as fixed entities but as those that change through the contact process, and hence it represents the asperities in a more realistic manner. The newly defined adhesion index and plasticity index defined for the n-point asperity model are used to consider the different conditions that arise because of varying load, surface and material parameters. A comparison between the load–separation behaviour of the new model and the conventional one shows a significant difference between the two depending on combinations of mean separation, adhesion index and plasticity index.

Cyclic loading of an elastic-plastic adhesive spherical microcontact

A previous study of a single load-unload cycle of an adhesive contact between an elastic-plastic microscopic sphere and a rigid flat is extended here for several load-unload cycles. The interacting forces between the sphere and the flat obey the Lennard–Jones potential. Kinematic hardening is assumed for the sphere material to account for possible plastic shakedown, and the difference between kinematic and isotropic hardenings is discussed. The main goal of the current work is to investigate the evolution of the load-approach curves for the elastic-plastic spherical contact during its cyclic loading-unloading. These curves are presented for different physical conditions, represented by three main dimensionless parameters, which affect the behavior of the elastic-plastic adhesive contact. A transition value of the Tabor parameter is found, below which the load-approach curves are always continuous and jump-in and jump-out instabilities are not expected.

Elastic–plastic adhesive contact of rough surfaces with asymmetric distribution of asperity heights

The elastic–plastic adhesive contact of rough surfaces is extended to include asymmetric distribution of asperity heights using the Weibull distribution with skewness as the key parameter to characterize asymmetry. The well-established elastic adhesion index and plasticity index are used to consider the different conditions that arise as a result of varying load and material parameters. The loading and unloading behaviour for different combinations of adhesion index, plasticity index and skewness values are obtained as functions of mean separation between the surfaces. It is seen that surfaces with negative skewness experience higher adhesion compared to surfaces with positive or zero skewness.

Elastic-Plastic Adhesive Contact of Rough Surfaces with Soft Coatings

A numerical study of adhesive contact between rough surfaces with soft coating is presented using an elastic-plastic model of asperity contact deformation. The analysis considers the elastic and plastic deformation of both the coating and the substrate unlike the work available in literature where the coating is considered to be in pure plastic contact. The JKR (Johnson-Kendall-Roberts) adhesion model is used and the well-established adhesion indices (elastic and plastic adhesion indices) are utilized to consider the different conditions of varying load and material and surface properties of the substrate and the coating. Contact load and contact area are obtained as functions of mean separation between surfaces for different combinations of adhesion parameters, material properties and thickness of the coating. The effects of these parameters on contact behavior of coated surfaces are investigated. For thin coating and light loading, contact is strongly influenced by the existence of soft coating that increases the contact area due to plastic deformation of the coating.

Elastic–plastic adhesive contact of rough surfaces based on plastic asperity concept

The paper describes an analysis of adhesive contact between rough surfaces with small-scale surface asperities using an elastic–plastic model of contact deformation based on fictitious plastic asperity concept developed by Abdo and Farhang [Int. J. Non-Linear Mech. 40 (2005) 495]. The model considers simultaneous occurrence of elastic and plastic behaviours for an asperity. The well-established elastic adhesion index and plasticity index are used to consider the different contact conditions that arise as a result of varying load and material parameters. The load-separation behaviour for different combinations of these parameters is obtained. Comparison with previous elastic–plastic model that was based on elastic-then-plastic assumption is made showing significant differences.

Asperity interaction in adhesive contact of metallic rough surfaces

The analysis of adhesive contact of metallic rough surfaces considering the effect of asperity interaction is the subject of this investigation. The micro-contact model of asperity interactions developed by Zhao and Chang (2001 Trans. ASME: J. Tribol. 123 857–64) is combined with the elastic plastic adhesive contact model developed by Chang et al (1988 Trans. ASME: J. Tribol. 110 50–6) to consider the asperity interaction and elastic–plastic deformation in the presence of surface forces simultaneously. The well-established elastic adhesion index and plasticity index are used to consider the different contact conditions. Results show that asperity interaction influences the load-separation behaviour in elastic–plastic adhesive contact of metallic rough surfaces significantly and, in general, adhesion is reduced due to asperity interactions.

Asperity interaction in elastic–plastic contact of rough surfaces in presence of adhesion

This paper presents an analysis of the effect of asperity interaction in elastic–plastic contact of rough surfaces in the presence of adhesion. The micro-contact model of asperity interactions, developed by Zhao and Chang (2001 Trans. ASME: J. Tribol. 123 857–64), is integrated into the elastic–plastic contact model developed by Roy Chowdhury and Ghosh (1994 Wear 174 9–19) to allow the asperity interaction and elastic–plastic deformation in the presence of surface forces to be considered simultaneously. The well-established elastic and plastic adhesion indices are used to consider the different conditions that arise as a result of varying load and material parameters. Results show that asperity interaction influences the loading–unloading behaviour in elastic–plastic adhesive contact of rough surfaces and in general asperity interactions reduce the effect of surface forces.