• Composites Research
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• v.36 no.3
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• pp.141-153
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• 2023

This review paper presents an introduction of contact mechanics and rubber friction theory for sliding friction of elastomer composites in contact with rough surfaces. Particularly, Klüppel & Heinrich theory considers the self-affine (or fractal) characteristic for rough surfaces to predict adhesion and hysteresis frictions of elastomers based on the contact mechanics of Greenwood & Williamson. Due to dynamic excitation process of elastomer composites while sliding in contact with multiscale surface roughness (or asperity), viscoelastic properties in a wide frequency range becomes major contributor to friction behaviors. A brief description and examples are provided to construct a viscoelastic master curve considering nonlinear viscoelasticity of elastomer composites. Finally, application of rubber friction theory to tire tread compounds in traction with road surfaces is discussed with several experimental and theoretical results.

• Structural Engineering and Mechanics
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• v.21 no.2
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• pp.205-220
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• 2005

This paper presents the possibilities of adapting artificial neural networks (ANNs) to predict the dimensionless parameters related to the maximum contact pressures of an elasticity problem. The plane symmetric double receding contact problem for a rigid stamp and two elastic strips having different elastic constants and heights is considered. The external load is applied to the upper elastic strip by means of a rigid stamp and the lower elastic strip is bonded to a rigid support. The problem is solved under the assumptions that the contact between two elastic strips also between the rigid stamp and the upper elastic strip are frictionless, the effect of gravity force is neglected and only compressive normal tractions can be transmitted through the interfaces. A three layered ANN with backpropagation (BP) algorithm is utilized for prediction of the dimensionless parameters related to the maximum contact pressures. Training and testing patterns are formed by using the theory of elasticity with integral transformation technique. ANN predictions and theoretical solutions are compared and seen that ANN predictions are quite close to the theoretical solutions. It is demonstrated that ANNs is a suitable numerical tool and if properly used, can reduce time consumed.

• Structural Engineering and Mechanics
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• v.25 no.4
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• pp.383-403
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• 2007

The contact problem for an elastic layer resting on an elastic half plane is considered according to the theory of elasticity with integral transformation technique. External loads P and Q are transmitted to the layer by means of two dissimilar rigid flat punches. Widths of punches are different and the thickness of the layer is h. All surfaces are frictionless and it is assumed that the layer is subjected to uniform vertical body force due to effect of gravity. The contact along the interface between elastic layer and half plane will be continuous, if the value of load factor, ${\lambda}$, is less than a critical value, ${\lambda}_{cr}$. However, if tensile tractions are not allowed on the interface, for ${\lambda}$ > ${\lambda}_{cr}$ the layer separates from the interface along a certain finite region. First the continuous contact problem is reduced to singular integral equations and solved numerically using appropriate Gauss-Chebyshev integration formulas. Initial separation loads, ${\lambda}_{cr}$, initial separation points, $x_{cr}$, are determined. Also the required distance between the punches to avoid any separation between the punches and the layer is studied and the limit distance between punches that ends interaction of punches, is investigated. Then discontinuous contact problem is formulated in terms of singular integral equations. The numerical results for initial and end points of the separation region, displacements of the region and the contact stress distribution along the interface between elastic layer and half plane is determined for various dimensionless quantities.

• Structural Engineering and Mechanics
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• v.54 no.4
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• pp.607-622
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• 2015

This paper presents a comparative study of analytical method and finite element method (FEM) for analysis of a continuous contact problem. The problem consists of two elastic layers loaded by means of a rigid circular punch and resting on semi-infinite plane. It is assumed that all surfaces are frictionless and only compressive normal tractions can be transmitted through the contact areas. Firstly, analytical solution of the problem is obtained by using theory of elasticity and integral transform techniques. Then, finite element model of the problem is constituted using ANSYS software and the two dimensional analysis of the problem is carried out. The contact stresses under rigid circular punch, the contact areas, normal stresses along the axis of symmetry are obtained for both solutions. The results show that contact stresses and the normal stresses obtained from finite element method (FEM) provide boundary conditions of the problem as well as analytical results. Also, the contact areas obtained from finite element method are very close to results obtained from analytical method; disagree by 0.03-1.61%. Finally, it can be said that there is a good agreement between two methods.

• Proceedings of the KSR Conference
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• 1998.05a
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• pp.315-322
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• 1998

A two dimensional elasto-plastic finite element program taking into account contact between crack surfaces if developed in order to analyze subsurface cracking in rolling contact. But the friction between upper and lower surface of the crack is not considered. Under the assumptions of small deformation and small displacement, the incremental theory of plasticity is used to describe plastic deformation. J-integral is computed as the applied Hertzian load slides over the surface with friction. J-integral is correlated with wear rate of the rail. The propagation rate of the right tip of the surface crack is fast by 45% than that of the left side.

• Tunnel and Underground Space
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• v.15 no.4 s.57
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• pp.305-315
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• 2005

DDA (Discontinuous Deformation Anlaysis) is one of the latest numerical analysis which has merits of both FEM and DEM. In this research a new edge-to-edge contact algorithm was applied on DDA. With adoption of new edge-to-edge contact state definition, sub-algorithm was improved about open-close iteration, contact state judge, contact detecting, and friction forces acting on joints. Newly applied DDA was verified based on two different cases. The DDA results show good agreement with numerically predicted one.

• Korean Journal of Metals and Materials
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• v.46 no.9
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• pp.585-592
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• 2008

Flip-chip bonding using Cu-Sn mushroom bumps composed of Cu pillar and Sn cap was accomplished, and the contact resistance and the thermal cycling reliability of the Cu-Sn mushroom bump joints were compared with those of the Sn planar bump joints. With flip-chip process at a same bonding stress, both the Cu-Sn mushroom bump joints and the Sn planar bump joints exhibited an almost identical average contact resistance. With increasing a bonding stress from 32 MPa to 44MPa, the average contact resistances of the Cu-Sn mushroom bump joints and the Sn planar bump joints became reduced from $30m{\Omega}/bump$ to $25m{\Omega}/bump$ due to heavier plastic deformation of the bumps. The Cu-Sn mushroom bump joints exhibited a superior thermal cycling reliability to that of the Sn planar bump joints at a bonding stress of 32 MPa. While the contact resistance characteristics of the Cu-Sn mushroom bump joints were not deteriorated even after 1000 thermal cycles ranging between $-40^{\circ}C$ and $80^{\circ}C$, the contact resistance of the Sn planar bump joints substantially increased with thermal cycling.

• Structural Engineering and Mechanics
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• v.84 no.4
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• pp.561-573
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• 2022

This paper presents a new model to obtain the minimum area of the contact surface for rectangular isolated footings, considering that the contact surface works partially to compression (a part of the contact surface of the footing is subjected to compression and the other is not in compression or tension). The methodology is developed by integration to obtain the axial load "P", moment around the X axis "M_x" and moment around the Y axis "M_y". This document presents the simplified and precise equations of the four possible cases of footing subjected to uniaxial bending and five possible cases of footing subjected to biaxial bending. The current model considers the contact area of the footing that works totally in compression, and other models consider the contact area that works partially under compression and these are developed by very complex iterative processes. Numerical examples are presented to obtain the minimum area of rectangular footings under an axial load and moments in two directions, and the results are compared with those of other authors. The results show that the new model presents smaller areas than the other authors presented.

• Structural Engineering and Mechanics
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• v.27 no.5
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• pp.555-574
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• 2007

Static response of an elastic beam on a two-parameter tensionless foundation is investigated by assuming that the beam is symmetrically subjected to a uniformly distributed load and concentrated edge loads. Governing equations of the problem are obtained and solved by pointing out that a concentrated edge foundation reaction in addition to a continuous foundation reaction along the beam axis in the case of complete contact and a discontinuity in the foundation reactions in the case of partial contact come into being as a direct result of the two-parameter foundation model. The numerical solution of the complete contact problem is straightforward. However, it is shown that the problem displays a highly non-linear character when the beam lifts off from the foundation. Numerical treatment of the governing equations is accomplished by adopting an iterative process to establish the contact length. Results are presented in figures to demonstrate the linear and non-linear behavior of the beam-foundation system for various values of the parameters of the problem comparatively.

• Proceedings of the KIEE Conference
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• 1999.07f
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• pp.2508-2511
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• 1999

A non-contact battery charger which transfers energy using magnetic field without any electrical contacts is designed using half-bridge series resonant converter. This converter utilizes series resonance to reduce the undesirable effect of large leakage inductance of the non-contact transformer and ZVS operation can reduce switching losses. In this paper. analysis and design procedure of half-bridge series resonant converter with non-contact transformer is presented. Input voltage is 85VAC ${\sim}$ 270VAC, output voltage and current is 4.1V and 800mA, respectively. Furthermore, a method for calculating the secondary current of the transformer to control battery charging current in constant current charging mode which is required for litium-ion battery is proposed and the performance is verified from experiments.