On the tangential contact behavior at elastic-plastic spherical contact problems (original) (raw)
Related papers
Elastic–Plastic Spherical Contact Modeling Including Roughness Effects
Tribology Letters, 2010
The effect of material properties and surface roughness on the contribution of asperities and sphere bulk displacements to the total displacement of a rough spherical contact is investigated. A dimensionless transition load, above which the contribution of the bulk displacement exceeds the contribution of the asperities displacement, is found as a function of the plasticity index and dimensionless critical interference of the sphere bulk. A criterion is proposed for evaluating the importance of surface roughness in calculating the displacement of a rough spherical contact. Some experimental results with a spherical micro-contact are presented to verify the model.
Elastic–plastic spherical contact under combined normal and tangential loading in full stick
Tribology Letters, 2006
The behavior of an elastic-plastic contact between a deformable sphere and a rigid flat under combined normal and tangential loading with full stick contact condition is investigated theoretically. Sliding inception is treated as a plastic yield failure mechanism, which allows static friction modeling under highly adhesive conditio ns. Several contact parameters such as: junction tangential stiffness, static friction force and static friction coefficient are extensively investigated. The phenomenon of junction growth and the evolution of the plastic zone in the contact region are briefly described. It is found that at low normal dimensionless loads the static friction coefficient decreases sharply with increasing normal load, in breach with the classical laws of friction. As the normal load further increases the static friction coefficient approaches a constant value that is about 0.3 for many material properties combinations.
Elastic-Plastic Contact Analysis of a Sphere and a Rigid Flat
Journal of Applied Mechanics, 2002
An elastic-plastic finite element model for the frictionless contact of a deformable sphere pressed by a rigid flat is presented. The evolution of the elastic-plastic contact with increasing interference is analyzed revealing three distinct stages that range from fully elastic through elastic-plastic to fully plastic contact interface. The model provides dimensionless expressions for the contact load, contact area, and mean contact pressure, covering a large range of interference values from yielding inception to fully plastic regime of the spherical contact zone. Comparison with previous elastic-plastic models that were based on some arbitrary assumptions is made showing large differences.
Tribology Letters, 2013
Correlation of contact problems is discussed in a detailed manner with focus on spherical contact. The finite element method is used to determine appropriate stress quantities, representative stresses, aiming at a general description of contact quantities such as mean contact pressure, and the size of the contact area. It is shown that the mean contact pressure can be well described by a single master curve, while this is not so for the size of the contact area. The latter feature is explained partly by a pronounced effect from elastic deformation, but is also shown that large deformation effects can have a substantial influence on correlation attempts. The analysis is restricted to classical Mises elastoplasticity, but the results can also serve as a guideline for similar attempts when using more advanced constitutive modeling. An obvious application of the present results concerns material characterization by indentation testing.
ELASTIC PLASTIC NON-CONFORMING CONTACT MODELING PART II: RESULTS AND DISCUSSIONS
imtuoradea.ro
The contact between a rigid sphere and an elastic-plastic half-space is modeled using the newly proposed computer program. The elastic-plastic behavior is described by a power hardening law (Swift). Numerical predictions agree well with results obtained from alternative numerical codes or from finite element analysis. The plastic strain region, initially hemispherical, advances peripherally toward the free surface, enveloping a purely elastic core on the central axis. Numerical simulations predict that residual stresses decrease the peak intensity of the stresses induced by contact pressure, thus impeding further plastic flow. Computed pressure distributions appear flattened compared to elastic case, due to changes in both hardening state and contact conformity.
Computational Particle Mechanics
A contact model for the normal interaction between elastoplastic spherical discrete elements has been investigated in the present paper. The Walton-Braun model with linear loading and unloading has been revisited. The main objectives of the research have been to validate the applicability of the linear loading and unloading models and estimate the loading and unloading stiffness parameters. The investigation has combined experimental tests and finite element simulations. Both experimental and numerical results have proved that the interaction between the spheres subjected to a contact pressure inducing a plastic deformation can be approximated by a linear relationship in quite a large range of elastoplastic deformation. Similarly, the linear model has been shown to be suitable for the unloading. It has been demonstrated that the Storåkers model provides a good evaluation of the loading stiffness for the elastoplastic contact and the unloading stiffness can be assumed as varying linearly with the deformation of the contacting spheres. The unloading stiffness can be expressed in a convenient way as a function of the Young's modulus and certain scaling factor dependent on the dimensionless parameter defining the level of the sphere deformation.
Tribology Letters, 2007
The real contact area between a sphere and a flat during loading, unloading, and cyclic loading-unloading in the elastic-plastic regime of deformations was investigated experimentally. A direct optical technique was used to observe in situ the evolution of the contact area. The experimental results obtained with copper and stainless steel spheres of different diameters that were pressed against a sapphire flat were compared with existing theoretical models, and whenever possible, with previous experimental works. These models are based on the assumption of either perfect slip (i.e., frictionless) or full stick contact condition. Good agreement was found between the experimental and theoretical results for the contact area and mean contact pressure. The existing models for the unloading process fail to accurately predict the residual radius of curvature of fully unloaded spheres, and the irreversibility of multiple loading unloading cycles at least for the several initial cycles. Some recommendations to improve the models are provided.
Experimental Investigation of Fully Plastic Contact of a Sphere Against a Hard Flat
Journal of Tribology, 2006
In this paper we report the experimental investigation to evaluate the published models for the contact of a deformable sphere against a hard flat in the fully plastic contact regime. A new measurement method has been used to measure the contact area. The behavior of the mean contact pressure and the contact area as a function of the contact load are presented. Substantial differences are found between the measurements and the model predictions. A constant value of the mean contact pressure as the load increases is observed, however, the value is lower than the hardness, as often reported. The contact area is found to be a simple truncation of the sphere by a hard flat.
A study of the elasticplastic deformation of heavily deformed spherical contacts
… of Engineering Tribology, 2010
This work uses a finite-element analysis and analytical equations to model elasticplastic large deformations of spheres in contact with rigid flat surfaces. No strain hardening in the sphere or friction between the surfaces has been considered. The case considered here is of a deformable sphere compressed by a rigid flat as opposed to the reverse case of a rigid spherical indenter penetrating a deformable surface. Most previous works only deal with elastic or elastoplastic deformation at much smaller deformations. A model for predicting the contact area, pressure, and force is proposed based on the finite element modelling (FEM) simulations and analytical equations derived from volume conservation. The analytical volume conservation approach is similar to that used to model the barrelling of compressed cylinders. The most important aspect of the model is the resulting equation relating the average pressure to the yield strength during fully plastic deformation. The results are compared with existing models and experimental data.
2010
The present study considers an elastic-plastic contact analysis of a deformable sphere with a rigid flat using finite element method. The effect of strain hardening on the contact behaviour of a non-adhesive frictionless elastic-plastic contact is analyzed using commercial finite element software ANSYS. To study the strain hardening effect we have taken different values of tangent modulus. The result of strain hardening effect clearly shows that a generalized solution can not be applicable for all kind of materials as the effect of strain hardening differently influenced the contact parameters. With the increase in the value of hardening parameter this effect also increases. For higher value of hardening parameter the effect of strain hardening is severe on contact parameters. With the increase in strain hardening the resistance to deformation of a material is increased and the material becomes capable of carrying higher amount of load in a smaller contact area.