Finite Element Analysis of the Contact Behavior of Rough Surface (original) (raw)

Finite-elements model for the contact of rough surfaces

Wear, 1994

In this paper the elastoplastic asperity-based model for the contact of rough surfaces is presented. The model adopts most of the basic asperity-based model's assumptions, introducing, however, a more realistic elastoplastic deformation law for the analysis of individual asperity deformation.

Rough surface contact analysis by means of the Finite Element Method and of a new reduced model

Comptes Rendus Mécanique, 2011

This article presents two approaches of a normal frictionless mechanical contact between an elastoplastic material and a rigid plane: a full scale finite element analysis (FEA) and a reduced model. Both of them use a representative surface element (RSE) of an experimentally measured surface roughness. The full scale FEA is performed with the Finite Element code Zset using its parallel solver. It provides the reference for the reduced model. The ingredients of the reduced model are a series of responses that are calibrated by means of FEA on a single asperity and phenomenological rules to account for asperity-asperity interaction. The reduced model is able to predict the load-displacement curve, the real contact area and the free volume between the contacting pair during the compression of a rough surface against a rigid plane. The CPU time is a few seconds for the reduced model, instead of a few days for the full FEA.

A 3D contact investigation of rough surfaces considering elastoplasticity

2008

In this work a homogenization method presented by Bandeira et al is enhanced to obtain by numerical simulation interface laws for the normal contact pressure based on statistical surface models. For this purpose elastoplastic behaviour of the asperities is introduced. Statistical evaluations of numerical simulations lead to a constitutive law for the contact pressure. The resulting law compared with other laws stemming from analytical investigations, like Greenwood Williamson and Yovanovich . The non-penetration condition and interface models for contact taking into account the surface microstructure are investigated in detail. This paper can be regarded as a complementary study to that presented by Bandeira et al . Here the plasticity of the asperities is taken into account by assuming a constitutive equation based on associated von Mises criterium formulated in principal axes.

A self-consistent model for the elastic contact of rough surfaces

The interaction of asperities plays an important role in the contact of rough surfaces. This paper develops a self-consistent contact model, in which the effect of asperity interaction is accounted for by applying the mean pressure around a representative asperity. Based on the Boussinesq's solution of a point force acting on an elastic half-plane, the problem is transformed into a singular integral equation. Using the Gauss-Legendre quadrature formula, we solve the integral equation numerically. The results demonstrate that when the ratio between the real contact area and the nominal one is small, the effect of asperity interaction is negligible and the present mode coincides with the Greenwood-Williamson model. However, when the area ratio gets larger, the interaction of asperities becomes prominent. For a given ratio between the real contact area to the nominal one, the self-consistent contact model predicts a higher load than the Greenwood-Williamson model, in agreement with relevant experimental results.

A Finite Element-Based Elastic-Plastic Model for the Contact of Rough Surfaces

Modelling and Simulation in Engineering, 2011

An elastic-plastic model for contacting rough surfaces that is based on accurate Finite Element Analysis (FEA) of an elasticplastic single asperity contact is presented. The plasticity index Ψ is shown to be the main dimensionless parameter that affects the contact of rough surfaces. Below Ψ = 0.6 the contact problem is purely elastic and above Ψ = 8 it is mostly plastic. The mean real contact pressure is found to be practically independent of the contact load, similarly to the material hardness in fully plastic contact. An "elastic-plastic hardness" in the form 0.4 1/Ψ H can therefore be used to relate the contact load and real area of contact. A comparison with the approximate CEB (Chang, Etsion, Bogy) model shows identical results for pure elastic contacts having plasticity index values below 0.6 but substantial differences for elastic-plastic contacts having plasticity index values above 1.

A Modified Approach in Modeling and Calculation of Contact Characteristics of Rough Surfaces

The Journal of Engineering Research [TJER]

A mathematical formulation for the contact of rough surfaces is presented. The derivation of the contact model is facilitated through the definition of plastic asperities that are assumed to be embedded at a critical depth within the actual surface asperities. The surface asperities are assumed to deform elastically whereas the plastic asperities experience only plastic deformation. The deformation of plastic asperities is made to obey the law of conservation of volume. It is believed that the proposed model is advantageous since (a) it provides a more accurate account of elasticplastic behavior of surfaces in contact and (b) it is applicable to model formulations that involve asperity shoulder-to shoulder contact. Comparison of numerical results for estimating true contact area and contact force using the proposed model and the earlier methods suggest that the proposed approach provides a more realistic prediction of elastic-plastic contact behavior.

A finite element-based model of normal contact between rough surfaces

Wear, 2003

Engineering surfaces can be characterized as more or less randomly rough. Contact between engineering surfaces is thus discontinuous and the real area of contact is a small fraction of the nominal contact area. The stiffness of a rough surface layer thus influences the contact state as well as the behavior of the surrounding system. A contact model that takes the properties of engineering surfaces into account has been developed and implemented using finite element software. The results obtained with the model have been verified by comparison with results from an independent numerical method. The results show that the height distribution of the topography has a significant influence on the contact stiffness but that the curvature of the roughness is of minor importance. The contact model that was developed for determining the apparent contact area and the distribution of the mean contact pressure could thus be based on a limited set of height parameters that describe the surface topography. By operating on the calculated apparent pressure distribution with a transformation function that is based on both height and curvature parameters, the real contact area can be estimated when the apparent contact state is known. The model presented is also valid for cases with local plastic flow in the bulk material.

A numerical method for real elastic contacts subjected to normal and tangential loading

Wear, 1994

Our understanding of the mechanics of contact behaviour for interacting particles has been developed mostly assuming that surfaces are smooth. However, real particles of interest in engineering science are generally rough. While recent studies have considered the influence of roughness on the normal force-displacement relationship, surface roughness was quantified using only a single scalar measure, disregarding the topology of the surface. There are some conflicting arguments concerning the effect of roughness on the tangential or shear force-displacement relationship. In this study, optical interferometry data are used to generate the surface topology for input into a 3D finite element model. This model is used to investigate the sensitivity of the normal force-displacement response to the surface topology by considering different surfaces with similar overall roughness values. The effect of surface roughness on the tangential force-displacement relationship and the influence of loading history are also explored. The results indicate that quantifying roughness using a single value, such as the root mean square height of roughness, S q , is insufficient to predict the effect of roughness upon stiffness. It is also shown that in the absence of interlocking, rough particle surfaces exhibit a lower frictional resistance in comparison with equivalent smooth surfaces.

Finite element simulation of inelastic contact for arbitrarily shaped rough bodies

Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, 2012

Accounting for surface roughness in contact simulation can significantly change the calculated values of contact stresses for many objects. This can be important for high-precision mechanisms where displacements of tens of micrometers are required, such as a machining attachment used to clamp machine elements during processing on high precision machine tools. In this case, even a small deformation changing the shape of asperities can be sufficient to influence the operation of the mechanism. For problems with extensive contact areas and relatively low nominal contact pressures, accounting for surface roughness can change the distribution of the contact stresses and the contact area. Therefore, a contact simulation should be run with minimum set of assumptions. A universal approach to account for surface roughness in the contact of arbitrarily shaped bodies using the finite element method is described. A contact between bodies with nominally flat rough surfaces is considered in order...