SOLID MECHANICS

Author: GOMEZ PULIDO MARIA DOLORES.
Year: 2003.
University: POLITÉCNICA DE CATALUÑA.
Place of defense: SALA CONFERÈNCIES CIMNE..
Place of preparation: EDIFICI C1 Campus NORD.

Summary: In this research paper provides a framework for analyzing the phenomenon of the localization of deformation in the context of solid invíscido (independent rate), within the classical theory of continuum. It interprets the location of deformations as a problem that involves strong discontinuities (discontinuous displacement camps), considering the deformation and displacement camps in a distributional. The study has focused on two-dimensional problems, contemplating both the kinematics of infinitesimal deformation as finite. Highlighted below are the most important characteristics of the analytical model studied:-Used kinematics of discontinuity strong to describe the location discontinuous mode (characterized by discontinuous displacement camps and not bounded deformation). Proper adjustment that allows kinematic simulation modes location bounded (discontinuity weak, characterized by continuous displacement camps and discontinuous deformation), which exhibit tracing bands whose width, and its evolution over the loading process, are determined by the model variable bandwidth. - To simulate the behavior of materials used models constituent incremental standard isótropos of classical mechanics of continuous elástico-degradable and elasto-plástico contract cuasi-estático. - Starting location is characterized by the loss of elipticidad of the constitutive equations incremental employed, through the analysis of discontinuous fork (in order to stay within the continuum mechanics). This analysis is necessary to describe the evolution of the discontinuity along the loading process (using an algorithm tracking). - There will always be known as the analysis of sharp discontinuity in laying down the requirements to be verified mathematical model in order to reconcile the kinematics of discontinuity strong and constitutive equations, from a physicist and mathematician. This analysis establishes restrictions tensionales (discontinuity conditions difficult) to be verified during the regime of strong discontinuity. Failure to meet these conditions at the instant of bifurcation requires the use of the so-called model of bandwidth variable bifurcando then regime discontinuity weak, develop a transitional phase until it is able to induce the strong discontinuity resulting discontinuity strong . - As a result of sharp discontinuity analysis is theoretically deduced models discrete (tracción-salto displacement) induced kinematics of sharp discontinuity in the constitutive models continuous (tension). The models that emerge in the discrete problem govern the behavior of the line of discontinuity, but they are not implemented in the algorithm. An interesting finding of this analysis is the fact obtain models discrete anisótropos from models continuous isótropos. It performs an exhaustive study of discrete patterns projected identifying all ingredients that give them the status of constitutive models. From the numerical point of view, below the main features of the finite element formulation used in the research work: - The numerical discretization of the problem, 8 vouchers 3f5 res contour involving discontinuities strengths is based on the method of deformation improved adding in the field of deformation (fair) standard element of a term not improved, the purpose of representing bands location inside the element. The term allows improved localization modes represent limited and not bounded.

Author: GARCIA FERNANDEZ VICTOR GERARDO.
Year: 2004.
University: POLITÉCNICA DE CATALUÑA.
Place of defense: AULA CAPELLA. ETSEIB..
Place of preparation: ETSEIB, PAVELLÓ E Campus SUD.

Summary: It has carried out a study to observe differences in creep behavior of hot brass refined to fire with a purity of 99.9%, the study has helped to propose models to predict the curve and to predict the esfuerzo grain size recristalizado dynamically. The refined copper to fire with a purity of 99.9% are characterized by having a composition of the residual number of other elements, in some cases up to 1000ppm. In brass with at least 99.9% purity that have little residual differences observed during creep hot attributed to the interactions between atoms dissolved and dislocations, specifically interactions with interstitial oxygen. In the electrolytic copper, which consists primarily of high oxygen content, the difference in yield is attributed to increasing numbers of particles Cu2O. This work demonstrates that rather differences effort refined copper found in the fire with a purity of 99.9% are due to the amount of residual oxygen, which is fine precipitates at temperatures intermediate reinforcing metal matrix. Despite the low content of oxygen in the copper studied (26-62ppm) have been characterized precipitates of Cu2O and have been used by precipitation hardening theories that have indicated that precipitates of Cu2O were responsible for the increase in resistance. The interactions between atoms of oxygen and dislocations are unlikely to cause a retro extra effort at temperatures higher than 600Â ° C, which has carried out this work. There were three brass tablet with 26, 46 and 62ppm oxygen around speeds of deformation 0.3s-1, 0.1s-1, 0.03s-1, 0.01s-1, 0.003s-1 and 0.001s-1 and some temperatures from 600Â ° C until 950Â ° C at intervals 50Â º. This study presents evidence of how low oxygen content in copper 99.9% pure may affect behavior esfuerzo and grain size recristalizado dynamically. In addition to having found something and the mechanism responsible for the retro extra effort also presents a mathematical algorithm to study and predict the oscillations of effort during the peak multiple dynamic recrystallization. Previous efforts using models Computarizados Monte Carlo models Cellular Automaton or Mathematical Models for Recristalización Dynamics (XRD) not predict fluctuations effort actual materials and its computation time makes them impractical for process simulation industry. The new Model Avrami with Cosine Amortiguado for DRX is able to predict the transition from XRD peak simple XRD peak multiple. In addition, the new model defines the effort stable state without having to choose a value of an experimental curve may not have reached a steady state. Another contribution of the new model is that it shows that the oscillations are completely predictable in terms of velocity deformation and temperature, a characteristic previously had said to be unlikely. The new model for XRD along with a modified model of Voce-Kocks for restoration dynamics have been successfully implemented for predicting creep hot. In addition to the contributions earlier this paper also presents the 8 relació 3b8 n which is the size of grain recristalizado with temperature and velocity deformation. It is assumed that the copper 99.9% pure, as studied, tend to a grain size of stable state which when at room temperature determine the mechanical properties of the product forged.

Author: MORAN PEREZ ANTONIO.
Year: 2004.
University: POLITÉCNICA DE CATALUÑA.
Place of defense: SALA DE CONFERÈNCIES DEL CIMNE.
Place of preparation: EDIFICI C1 Campus NORD.

Summary: The model has been discretizado spatial beam Cosserat through the finite element method and has made a non-linear analysis using the same formulations tangent and blotting. With the formulation tangent are widespread and extended performance Simó-Géradin, and the formulation blotting has developed a set of theories which allow high-order address the classic problems of structural stability. It has become a special interest in developing the method of posting critical Oñate-Matias and its application to predictive analysis of the critical buckling load of a system composed of structural beams.