Numerical simulations of the normal impact of adhesive microparticles with a rigid substrate (original) (raw)
Related papers
Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2008
The theory of low velocity impact between nano-sized, spherical particles and a rigid plane is developed by assuming fully plastic failure during approach and assuming the Johnson-Kandall-Roberts model of elasticity and adhesion applied during particle recoil. This model predicts initial particle acceleration on approach, followed by either deceleration and eventually instantaneous cessation of particle motion or extreme deformation and possible structural failure of the particle. If the approach motion ceases and the recoil begins, then either the particle is trapped on the surface or it separates. The typical frequency of oscillations of trapped particles is derived. Criteria for the occurrence of the various regimes are derived, together with conditions for when surface adhesion is important.
Predicting the coefficient of restitution of impacting elastic-perfectly plastic spheres
Nonlinear Dynamics, 2010
The current work presents a different methodology for modeling the impact between elastoplastic spheres. Recent finite element results modeling the static deformation of an elasto-plastic sphere are used in conjunction with equations for the variation of kinetic energy to obtain predictions for the coefficient of restitution. A model is also needed to predict the residual deformation of the sphere during rebound, or unloading, of which several are available and compared in this work. The model predicts that a significant amount of energy will be dissipated in the form of plastic deformation such that as the speed at initial impact increases, the coefficient of restitution decreases. This work also derives a new equation for the initial critical speed which causes initial plastic deformation in the sphere that is different than that shown in previously derived equations and is strongly dependant on Poisson's Ratio. For impacts occurring above this speed, the coefficient of restitution will be less than a value of one. This work also compares the predictions between several models that make significantly differ-ent predictions. The results of the current model also compare well with some existing experimental data. Empirical fits to the results are provided for use as a tool to predict the coefficient of restitution.
Energy Loss in the Impact of Elastic Spheres on a Rigid Half-Space in Presence of Adhesion
Tribology Letters, 2014
Adhesion can cause energy losses in asperities or particles coming into dynamic contact resulting in frictional dissipation, even if the deformation occurring is purely elastic. Such losses are of special significance in impact of nanoparticles and friction between surfaces under low contact pressure to hardness ratio. The objective of this work is to study the effect of adhesion during the normal impact of elastic spheres on a rigid half-space, with an emphasis on understanding the mechanism of energy loss. We use finite element method for modeling the impact phenomenon, with the adhesion due to van der Waals force and the short-range repulsion included as body forces distributed over the volume of the sphere. This approach, in contrast with commonly used surface force approximation, helps to model the interactions in a more precise way. We find that the energy loss in impact of elastic spheres is negligible unless there are adhesion-induced instabilities. Significant energy loss through elastic stress waves occurs due to jump-to-contact and jump-out-of-contact instabilities and can even result in capture of the elastic sphere on the half-space.
The theory of low-velocity impact between nano-sized, spherical particles requires consideration of surface energy, which causes approach speeds to increase on first contact, and recoil speeds to reduce, just before geometrical separation. A conceptual model is developed in which six major regimes are identified: the pancake and/or thin-film regime results from extreme particle accelerations and particle flattening from surface energy; the disintegration and/or torus regime results from high kinetic energy causing the particle to disintegrate or to pass through itself (torus); the approach regime results when the particle ceases its approach without extreme geometrical changes (and this leads into the recoil regime); the escape regime results when the particle escapes from the surface; the capture regime occurs when the particle is trapped by the surface, about which it continues oscillating; and the stick regime where the recoil step does not proceed, and the particle remains at the position at the end of the approach regime. The approach regime is described by one non-dimensional parameter, and the recoil regime by another non-dimensional parameter. An upper bound for the duration of the approach regime is obtained which is independent of surface energy and initial approach speed. The recoil regime results in particle escape (capture) when the elastic energy exceeds (is less than or equal to) the surface energy at the beginning of recoil. Stick occurs when the surface energy at the beginning of recoil equals or exceeds twice the corresponding elastic energy.
A coefficient of restitution model for sphere–plate elastoplastic impact with flexural vibrations
Nonlinear Dynamics, 2017
The current work presents an experimentally validated analytical model for low-velocity impact between a sphere and a plate. The model accounts for plastic deformation as well as flexural vibrations. The elastic phases are modeled with a nonlinear Hertzian contact model, and the plastic phase is linearized with a non-homogeneous expression. The results are compared against newly carried out experiments. The model well captures the effect of plate thickness-tosphere diameter ratio, impact velocity, and material properties. The model's generalized framework allows consideration for various expressions of contact parameters, critical velocity, and residual indentation. Moreover, the proposed methodology can be easily incorporated into particle-based or discrete element modeling approaches for granular flows to evaluate the realtime coefficient of restitution as opposed to assuming the constant value beforehand. Simplified relations are provided to assist in evaluating the coefficient of restitution.
Adhesive impact of micromechanical surface contact
In this study, a new generalized adhesion theory of solid sphere is developed to investigate adhesive impact of head-disk surfaces. On the basis of this adhesion theory, deformation and restoration work done is evaluated for multiasperity adhesive impact of head-disk surfaces. From the plot of coefficient of restitution with mean separation, its found COR decreases gradually, with decrement of mean separation approaching to zero value which represents unique characteristic for head-disk impact. It indicates there is possibility of seizure of head-disk due to high adhesion at the interface for high impact.
Adhesive Contact Deformation of a Single Microelastomeric Sphere
Journal of Colloid and Interface Science, 1998
The current work reports primarily on an experimental This paper reports on an experimental study of the adhesive study, with associated theoretical analyses, of the comprescontact of a single microscopic (about 300 mm) elastomer sphere sive deformation behavior of microscopic elastic polymer compressed between two smooth parallel glass platens at small spheres at a small range-imposed strain in ambient air. For imposed deformations. An experimental arrangement that allows a nonadhesive elastic sphere compressed between two paralthe simultaneous measurement of the compressive displacements lel flat platens, the force resisting this deformation depends and the reaction forces is described. A number of interesting pheupon the approach (half of the compressive displacement at nomena, including the pull-off separation and the ''jump'' contact the pole of the deformed sphere) to the 3/2 power for small phenomena of the microsphere and the moving platen supported by a cantilever, are shown in the experimental force-displacement deformations. The theoretical nature of this relationship was curve of a loading and unloading cycle. The pull-off forces are originally described in detail by Hertz and allows the demonstrated to not depend upon the applied dimensionless apdeformation of the sphere in the region of the contacting proach (compressive displacement/initial particle diameter), platens to be fully described, subject to a number of imwhile they increase with the increasing rate at which the interfaces portant assumptions. The principal assumptions are that a are separated. The predictions of an established contact mechaninormally loaded contact exists between the bodies, that the cal adhesive theory, Johnson-Kendall-Roberts (JKR) theory, in material behaves as a linear elastic body, that the radius of which the influence of the surface energy on the contact has been contact area is small compared with the radius of the sphere, taken into account, are in good agreement with these experimental and that there is frictionless contact between the surfaces results. An application of the JKR analysis to the pull-off force resulting in the transfer of only normal stresses between the provides a reasonable estimate of the interfacial free energy of the contact. ᭧ 1998 Academic Press contacting surfaces.