A Finite Element Algorithm for Electromechanical Contact Problems

In the last hundred years a lot of work is done in describing and measuring the influence of the pressure on the resistance and wear in electrical contacts. But up to now there exists a lack of knowledge in predicting and optimizing the behavior of electrical contacts with numerical simulation tools considering the pressure dependency. The present work provides a new constitutive model for the contact interface in the case of current flow and a new friction law including electrical wear phenomena. Additionally numerical investigations are made to compare the numerical results with experimental data. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Modeling the asymmetry in traffic flow (a): Microscopic approach

The asymmetric characteristic of a vehicle’s ability in deceleration and acceleration, as well as its impact to micro- and macroscopic traffic flow has caused increased attention from both theoretical and practical sides. However, how to realistically model this property remains a challenge to researchers. This paper is one of the two studies on this topic, which is focused on the modeling at the microscopic level from the investigation of car-following behavior. The second part of the study [H. Liu, H. Xu, H. Gong, Modeling the asymmetry in traffic flow (b): macroscopic approach, Appl. Math. Model. (submitted for publication)] is focused on the modeling of this asymmetric property from the macroscopic scale. In this paper, we first present an asymmetric full velocity difference car-following approach, in which a higher order differential equation is developed to take into account the effect of asymmetric acceleration and deceleration in car-following. Then, efforts are dedicated to calibrate the sensitivity coefficients from field data to complete the theoretical approach. Using the data recorded from the main lane traffic and ramp traffic of a segment of the US101 freeway, the two sensitivity coefficients have been successfully calibrated from both congested and light traffic environments. The experimental study reveals that in the studied traffic flow, the intensity of positive velocity difference term is significantly higher than the negative velocity difference term, which agrees well with the results from studies on vehicle mechanics.     

Contact Modeling in Multibody Systems with Elastic Bodies in High-Frequency Applications

This paper discusses the refinement of multibody models by integration of flexible bodies and by considering nonlinearities from contacts. It presents common approaches for contact modeling in multibody simulations and strategies to include flexible bodies. A contact model is implemented in the elastic multibody model. Experimental results show that significant effects of system dynamics can be modeled by use of a multibody model including elastic bodies and contacts. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Homogenization of a Model Problem on Contact Angle Dynamics

In this paper we consider homogenization of oscillating free boundary velocities in periodic media, with general initial data. We prove that there is a unique and stable effective free boundary velocity in the homogenization limit.     

A Microscopic model for a cell-seeded material

The aim of the present paper is to account for the growth of fiber which is observed in a cell-seeded material stimulated in a bioreactor. For this purpose, the change of mass is considered in the balance laws, and the deformation energy is assumed to be a function of varying mass and the Helmholtz free-energy. Fiber growth at the microscopic level causes a macroscopic change of the material's mechanical properties. The study is a first approach towards a micromechanical model accounting for remodelling in cartilage replacement materials. In so doing, constitutive equations for renewable soft tissues are proposed. (© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Steady-State Frictional Heat Generation on a Periodic Sliding Contact

We investigate the motion of a periodic system of rigid, isolated, parabolic dies along the surface of a half-space. The action of friction forces results in heat generation in the contact region. We assume that the surfaces of the dies are thermally insulated and the half-space is a heat conductor. We reduce the problem under consideration to a set of two integral equations for the contact temperature and pressure. We solve these equations numerically and investigate the influence of thermal deformation on the distributions of temperature and pressure and on the dimensions of the contact region.     

Electromechanical modelling of skeletal muscle contractions

In the present paper, the aim was to develop a numerical method for optimisation an existing mechanical material model [1] including muscle activation concerning the excitation of skeletal muscles. The modelling idea was a weak and non-monolithic coupling of an electric current expressed by Ohm's law with a hyperelastic muscle model with transversal isotropic characteristics, see [2]. We confirmed the ability of the proposed model by applying on real reconstructed complex muscle geometry. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

再论各向异性平面弹性中的一个周期接触问题——纪念李国平院士吴新谋教授诞辰100周年

该文对下面的一个弹性接触问题进行了再讨论.一列周期排列刚性压头压入一个各向异性弹性半平面的边界上,并有摩擦力存在, 求应力平衡.此问题在文献[1, 2]中曾讨论过并求出其解.但解法似不完全确切.该文将它进行修正从而获得精确解的封闭形式.     

Electromechanical properties of laminated piezoelectric composites

The general expressions for the effective elastic, piezoelectric, and dielectric coefficients of a laminated piezocomposite composed of laminates in parallel connection are shown. By means of the asymptotic averaging method [12] these effective coefficients are calculated. The effective coefficients as well as physical properties such as electromechanical piezoelectric coupling coefficients, acoustic impedance, and wave velocity for a two-phase composite, where one phase is ceramic and the other one is polymer, are analyzed. A comparison with another results is shown.Presented at the Ninth International Conference on the Mechanics of Composite Materials, Riga, October, 1995.Published in Mekhanika Kompozitnykh Materialov, Vol. 32, No. 3, pp. 410–417, May–June, 1996.     

Modeling cooperation on a class of distribution problems

In this paper we study models of cooperation between the nodes of a network that represents a distribution problem. The distribution problem we propose arises when, over a graph, a group of nodes offers certain commodity, some other nodes require it and a third group of nodes neither need this material nor offer it but they are strategically relevant to the distribution plan. The delivery of one unit of material to a demand node generates a fixed profit, and the shipping of the material through the arcs has an associated cost. We show that in such a framework cooperation is beneficial for the different parties. We prove that the cooperative situation arising from this distribution problem is totally balanced by finding a set of stable allocations (in the core of an associated cooperative game). In order to overcome certain fairness problems of these solutions, we introduce two new solution concepts and study their properties.     

Solution of a Contact Elasticity Problem with a Rigid Inclusion

Computational Mathematics and Mathematical Physics - An equilibrium problem for an elastic body containing a rigid inclusion is solved. There is a delamination crack on a portion of the interface...     

Contact transformations,contact algebras and lifts on a jet bundle

Summary It is shown that any contact preserving map germ on a jet bundle J is the lift of any map germ JJ⁰, satisfying some rank conditions. The different contact preserving homeomorphisms are given as well as the different lifts derived from these constructions. The relation with the infinitesimal and formal case is given.     

On Passivity-Based Control of Non-Classical Electromechanical Systems

Passivity-based control has exclusively been pursued for dynamical systems possessing energetic state functions that are quadratic in the generalized velocities. This assumption does not apply to many dynamical systems, for instance in electromechanics, thus passivity-based control has not been established for these classes of systems. This contribution presents an augmented PD control scheme for such systems. To this end the system dynamics is represented in the event space considered as a Finsler space. It is shown that in this setting the skew symmetry property is retained. A passivity-based augmented PD controller is designed in the event space, and restricted to the configuration space giving rise to a passivity-base control law. (© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Electromechanical properties of continuous fibre-reinforced piezoelectric composites

The objective of this paper is to present analytical expressions of the basic effective constants (for transducer applications) of fibrous piezoelectric composites with a periodic structure. These expressions were obtained on the basis of the asymptotic averaging method, following the same procedure used in [1] for the purely elastic case. The averaged electromechanical properties for these piezocomposites can be calculated from the above formulas. The results obtained from the theoretical predictions with the use of homogenization method show good agreement with the existing experimental results.Published in Mekhanika Kompozitnykh Materialov, Vol. 33, No. 5, pp. 670–680, September–October, 1997.     

On a Class of Contact Riemannian 3-Manifolds

In this paper we classify 3-dimensional complete contact Riemannian manifolds satisfying the following condition “the characteristic vector field is an eigenvector of the Ricci operator with constant eigenvalue”. Moreover we prove that this condition is equivalent with some other characteristic ones.     

Contact Elements on Fibered Manifolds

For every product preserving bundle functor T ^μ on fibered manifolds, we describe the underlying functor of any order (r, s, q), s ≥ r ≤ q. We define the bundle K_k,l^r,s,q YK_{k,l}^{r,s,q} Y of (k, l)-dimensional contact elements of the order (r, s, q) on a fibered manifold Y and we characterize its elements geometrically. Then we study the bundle of general contact elements of type μ. We also determine all natural transformations of K_k,l^r,s,q YK_{k,l}^{r,s,q} Y into itself and of T( K_k,l^r,s,q Y )T\left( {K_{k,l}^{r,s,q} Y} \right) into itself and we find all natural operators lifting projectable vector fields and horizontal one-forms from Y to K_k,l^r,s,q YK_{k,l}^{r,s,q} Y .