Papers by Keyword: Contact Mechanics

Abstract: Investigation of forming forces in incremental sheet forming (ISF) is of great importance since it provides understanding of the deformation mechanics, monitoring of the forming process, failure prediction, and future means of on-line control and optimization. This paper provides a review of studies on the contact conditions and the effects of the process parameters on forming forces in ISF, followed by the current status on forming force prediction and its potential role in the improvement of ISF technology.

Abstract: A three-dimensional boundary element methodology to study frictionless indentation response of piezoelectric (PE) materials is presented. The boundary element method (BEM) is used in order to compute the electro-elastic influence coeffcients of fully anisotropic piezoelectric solids. The proposed contact formulation is based on the augmented Lagrangian method presented in [33, 34, 35] and makes it possible to consider piezoelectric materials under different mechanical and electrical boundary conditions (i.e. insulating indenter and conducting indenter). The methodology is validated by comparison with theoretical solutions presented in the literature.

Abstract: In this study, the contact problem for a graded elastic half-plane in frictional contact with a rigid stamp is considered. The plane contact problem is assumed to be linear elastic and the Poisson's ratio is assumed to be constant. Analytical formulation of the study includes Fourier transforms of the governing equations and boundary conditions. The resulting integral equation is solved numerically. Contact pressure, in-plane stress and the stress intensity factor at the sharp edges of the contact are evaluated and demonstrated for various stamp profiles. The results are compared with a closed form solution for homogeneous isotropic half-plane indented by rigid stamps. The effects of the nonhomogeneity parameter, coefficient of friction and stamp profiles on the contact and in-plane stresses are analyzed in detail.

Abstract: In the present study contact between elastic-plastic dissimilar spherical particles are investigated. The investigation is based on analytical and numerical methods and in the latter case in particular the finite element method. The results presented are pertinent to force-displacement relations at contact when elastic and plastic deformations are of equal magnitude. Especially, hard metal particles are considered with a typical application area being analysis of powder compaction.

Abstract: Investigation of local plastic deformation between rough surfaces in mechanical components such as gears, camshaft and bearings is very important. Contact between real surfaces occurs at the summits of the highest asperities which vary in height and radius. The plastic deformation of the contact between two asperities was studied in this paper. Asperity contact was modelled as a contact between hemispheres. The commercial finite element software, ABAQUS, was employed to perform the numerical contact analysis of the elastic perfectly-plastic deforming hemispheres with the ratios of radii (R₂/R₁) from 1 to 7. Normal loads of 5000 N, 8000 N and 11000 N were applied to the frictionless contact of the hemispheres. It was shown that the plastic deformation ratio (ω_p1/ω_p2) decreases as the radii ratio increases. The higher normal load showed a lower plastic deformation ratio for high radii ratio. The results indicate that the radii ratio contributes to the severity of the plastic deformation and the total displacement of the contacting asperities.

Abstract: The article deals with the problem of transition quasi-static contact in global slip under cyclic tangential load. The state of stress in partial contact, the laws of friction and scenarios of transition to slip of metal surface was determined. Partial slip is defined by the existence of stick and slip zones within the contact area. Currently, there are two basic concepts concerning surface damage processes: one connected with surface activation, which involves an increase in free energy in a tribological system, and the other connected with surface passivity, when free energy decreases. Experimental and theoretical studies were conducted to determine the contact between a sphere and a plane, which is the most suitable system for simulating small-amplitude fretting (~ 0–3 microns).

Abstract: This paper presents a numerical model to calculate wear during rolling contact due to micro-slip. Having as initial condition a corrugated rail it is shown the influence of the corrugation wavelength and the dynamic effects of the normal force on the wear creation. Experimental results are presented in order to reveal the influence of roughness when studying the stick-slip phenomenon.

Abstract: This article aims at extending the node to surface formulation for contact problems withan area regularization as proposed by [1]. For that purpose, two methods are proposed to computethe equivalent contact area attributed to each slave node. The first method, which is based on a geo-metrical approach through force equivalence, is an original extension of the one proposed in [1] fortwo-dimensional contact problems, i.e. plane stress and plane strain state, to the axisymmetric mod-elling context. The second method relies on an energy consistent way obtained through the virtualwork principle and the same expression for the equivalent contact area as the one originally cited in[2] is then recovered. First, the node to surface strategy with area regularization is introduced and theaforementioned methods for the equivalent contact area are presented in detail and compared. After-wards a consistent linearization technique is applied to achieve a quadratic convergence rate in theNewton Raphson iterative procedure used to solve the non-linear equilibrium equations of the under-lying finite element model. Finally, two axisymmetric numerical examples are provided in order tocompare the aforementioned equivalent contact area evaluations and to demonstrate the performanceand the robustness of the consistent approach especially in the neighbourhood the revolution axis.

Abstract: In this study, the frictional contact with partial slide between two elastic cylinders is considered. According to the Spence’s self-similarity condition, a system of singular integral equations is constructed with respect to the normal pressure and the shear traction in the contacting area. Based on the Goodman’s hypothesis, the preceding system is uncoupled. Based on this, the tangential load in the central sticking zone is possible to be obtained analytically by means of the theory on the singular integral equation. Besides, a nonlinear equation with respect to the ratio of the slip and adhesive zone sizes is derived on the basis of the continuity of the tangential load. The stick zone size can thus be determined by solving the nonlinear equation mention above iteratively. A numerical example is provided to verify and validate the theory proposed in this work.

Abstract: A multibody formulation is used to accurately describe the relation between the different components in chain drive systems and their full dynamics [1]. All components, including sprockets, are represented by rigid bodies connected to each other by revolute clearance joints [2]. The complete formulation is implemented in a computational simulation tool integrating all relevant dynamic characteristics inherent to chain drives and incorporated in the general-purpose multibody program [3]. Penalty contact force models are considered for modelling the revolute clearance joints, particularly those proposed by Lankarani and Nikravesh to quantify the normal contact force [4]. The friction force is accounted for based on the modified Coulombs friction law [2]. This work draws on the influence of dry contact parameters such as friction coefficient, restitution coefficient and clearance value on the dynamics of chain drives. The effect of a pretension level is also analyzed.