Problemas actuales y nuevas tendencias en mecánica de geomateriales

Este trabajo tiene como propósito realizar una discusión general de algunos de los problemas más importantes que se presentan en el análisis inelástico de geomateriales, tales como rocas, suelos y su interacción con las estructuras. En este trabajo se discutirán algunos aspectos esenciales del sistema de análisis inelástico, indicando los tipos de problemas que se investigan actualmente, o que se resolverán en el futuro.The present paper is aimed a general discussion of some major problems encountered in iilelastic analysis of geomaterials such as rocks, soils, and their interaction with structures. In this paper, some essential elements of the system of inelastic analysis will be discussed, indicating types of problems actually investigated or to be solved in the future.Peer Reviewe

Problemas actuales y nuevas tendencias en mecánica de geomateriales

Este trabajo tiene como propósito realizar una discusión general de algunos de los problemas más importantes que se presentan en el análisis inelástico de geomateriales, tales como rocas, suelos y su interacción con las estructuras. En este trabajo se discutirán algunos aspectos esenciales del sistema de análisis inelástico, indicando los tipos de problemas que se investigan actualmente, o que se resolverán en el futuro.The present paper is aimed a general discussion of some major problems encountered in iilelastic analysis of geomaterials such as rocks, soils, and their interaction with structures. In this paper, some essential elements of the system of inelastic analysis will be discussed, indicating types of problems actually investigated or to be solved in the future.Peer Reviewe

From Thomson formula to resonant equivalent diagrams

Until the 1970s, only three basic elements: R, C, and L have been used to construct RLC circuits. These elements are two-ports of zero order (resistances) and of first order (capacitances and inductances). Their presence in electronic circuits causes a certain phase shift between voltage and current. In 1969, Bruton published an inductorless filter. There are two two-ports of second order (supercapacitances) in this circuit. Supercapacitance causes a phase shift of 180 degrees. In the next years, many two-ports of higher orders (e.g. of second and third order) were developed and, in theory, their number may be infinite. The use of such two-ports in resonant circuits makes it possible to obtain other phase shifts. In this paper, we show how to transform basic circuits into their resonant equivalent diagram. The analysis of these diagrams allows us to describe precisely resonant phenomena occurring in the circuit and to identify all resonant circuits, even when the basic diagram does not indicate resonance properties

Comportement hystérétique du frottement anisotrope

Ce papier présente des simulations numériques de problèmes de contact 3D avec une loi de frottement orthotrope et une loi de glissement non associée. L'algorithme de résolution est basé sur la méthode du bi-potentiel appliquée à un système d'équations non linéaires et non différentiables. Une attention particulière est portée aux chargements cycliques car le taux d'usure est fortement couplé à la dissipation par frottement. Cette première étude semble indiquer une grande influence de l'anisotropie du frottement sur l'usure des pièces

Modeling of combined slip and finite sliding at spherical grain contacts

The present paper is aimed at developing the analytical description of the interaction of two contacting spheres for several classes of slip and sliding trajectories, typical in the experimental testing. The analysis accounts for memory effects in the slip regime and configurational effects in the sliding regime, expressed in terms of an active loading surface and memory surfaces within the space of contact forces. Analytical relations for contact response are derived for linear and piecewise-linear motion trajectories of the sphere. The problem of multiple contact interaction of the sphere moving over the regularly packed granular bed is also considered analytically. It is demonstrated that the dual contact activation-separation processes occur within the combined slip–sliding modes, essentially affecting the distribution of contact tractions. The results obtained are relevant for the class of contact problems requiring analysis of interaction of slip and sliding displacements, in particular in testing grain contact interaction aimed at specification of elastic, frictional and wear parameters

Topology design for thermomechanical actuators

The paper deals with topology design of thermomechanical actuators. The goal of shape optimization is to maximize the output displacement in a given direction on the boundary of the elastic body, which is submitted to a thermal excitation that induces a dilatation/contraction of the thermomechanical device. The optimal structure is identified by an elastic material distribution, while a very complacent (weak) mate- rial is used to mimic voids. The mathematical model of an actuator takes the form of semi-coupled system of partial differential equations. The boundary value problem in- clude two components, the Navier equation for linear elasticity coupled with the Poisson equation for steady-state heat conduction. The mechanical coupling is the thermal stress induced by the temperature field. Given the integral shape functional, we evaluate its topological derivative with respect to the nucleation of a small circular inclusion with the thermomechanical properties governed by two contrast parameters. The obtained topo- logical derivative is employed to generate a steepest descent direction within the level set numerical procedure of topology optimization in a fixed geometrical domain. Fi- nally, several finite element-based examples for the topology design of thermomechanical actuators are presented