Emprego de ferramentas num��ricas na avalia����o do m��dulo de elasticidade em vigas roli��as de madeira

Vigas s��o elementos estruturais encontrados na maioria das constru����es civis. Dentre os materiais de engenharia, destaca-se a madeira, por ter resist��ncia mec��nica satisfat��ria aliada a baixa densidade. A madeira roli��a apresenta-se como boa solu����o na confec����o de vigas, uma vez que n��o precisa ser processada, como �� o caso da madeira serrada. O projeto de elementos estruturais de madeira requer o conhecimento de suas propriedades f��sicas e mec��nicas, obtidas segundo as premissas de documentos normativos. Em se tratando da madeira roli��a, os documentos normativos nacionais que tratam da determina����o das propriedades de resist��ncia e rigidez est��o vigentes h�� mais de vinte anos sem revis��o t��cnica. De forma geral, tanto as normas nacionais como as internacionais idealizam geometria troncoc��nica para as pe��as roli��as de madeira, implicando equa����es simplificadas incapazes de prever a influ��ncia das irregularidades da forma na determina����o do m��dulo de elasticidade longitudinal. Este trabalho objetiva avaliar a influ��ncia das irregularidades da geometria em pe��as roli��as de madeira Corymbia citriodora e Pinus caribaea no c��lculo do m��dulo de elasticidade longitudinal. Para tanto, utilizou-se do ensaio de flex��o est��tica a tr��s pontos, considerando tamb��m um modelo matem��tico simplificado, assumindo se����o circular constante para a forma do elemento. As irregularidades das pe��as s��o consideradas nos modelos num��ricos, constitu��dos de elementos finitos de barra e tridimensionais. Os resultados encontrados revelam equival��ncia estat��stica entre os m��dulos de elasticidade para ambas as formas de c��lculo, indicando ser plaus��vel a considera����o de se����o circular constante para as pe��as de madeira aqui avaliadas.

Finite element analysis of stress distribution in anchor teeth in surgically assisted rapid palatal expansion

The treatment of a transverse maxillary deficiency in skeletally mature individuals should include surgically assisted rapid palatal expansion. This study evaluated the distribution of stresses that affect the expander's anchor teeth using finite element analysis when the osteotomy is varied. Five virtual models were built and the surgically assisted rapid palatal expansion was simulated. Results showed tension on the lingual face of the teeth and alveolar bone, and compression on the buccal side of the alveolar bone. The subtotal Le Fort I osteotomy combined with intermaxillary suture osteotomy seemed to reduce the dissipation of tensions. Therefore, subtotal Le Fort I osteotomy without a step in the zygomaticomaxillary buttress, combined with intermaxillary suture osteotomy and pterygomaxillary disjunction may be the osteotomy of choice to reduce tensions on anchor teeth, which tend to move mesiobuccally (premolar) and distobuccally (molar)

Development of heat sink device by using topology optimization

Small scale fluid flow systems have been studied for various applications, such as chemical reagent dosages and cooling devices of compact electronic components. This work proposes to present the complete cycle development of an optimized heat sink designed by using Topology Optimization Method (TOM) for best performance, including minimization of pressure drop in fluid flow and maximization of heat dissipation effects, aiming small scale applications. The TOM is applied to a domain, to obtain an optimized channel topology, according to a given multi-objective function that combines pressure drop minimization and heat transfer maximization. Stokes flow hypothesis is adopted. Moreover, both conduction and forced convection effects are included in the steady-state heat transfer model. The topology optimization procedure combines the Finite Element Method (to carry out the physical analysis) with Sequential Linear Programming (as the optimization algorithm). Two-dimensional topology optimization results of channel layouts obtained for a heat sink design are presented as example to illustrate the design methodology. 3D computational simulations and prototype manufacturing have been carried out to validate the proposed design methodology.

Experimental and numerical analysis of dry contact in the pin on disc test

The reduction of friction and wear in systems presenting metal-to-metal contacts, as in several mechanical components, represents a traditional challenge in tribology. In this context, this work presents a computational study based on the linear Archard's wear law and finite element modeling (FEM), in order to analyze unlubricated sliding wear observed in typical pin on disc tests. Such modeling was developed using finite element software Abaqus�� with 3-D deformable geometries and elastic���plastic material behavior for the contact surfaces. Archard's wear model was implemented into a FORTRAN user subroutine (UMESHMOTION) in order to describe sliding wear. Modeling of debris and oxide formation mechanisms was taken into account by the use of a global wear coefficient obtained from experimental measurements. Such implementation considers an incremental computation for surface wear based on the nodal displacements by means of adaptive mesh tools that rearrange local nodal positions. In this way, the worn track was obtained and new surface profile is integrated for mass loss assessments. This work also presents experimental pin on disc tests with AISI 4140 pins on rotating AISI H13 discs with normal loads of 10, 35, 70 and 140 N, which represent, respectively, mild, transition and severe wear regimes, at sliding speed of 0.1 m/s. Numerical and experimental results were compared in terms of wear rate and friction coefficient. Furthermore, in the numerical simulation the stress field distribution and changes in the surface profile across the worn track of the disc were analyzed. The applied numerical formulation has shown to be more appropriate to predict mild wear regime than severe regime, especially due to the shorter running-in period observed in lower loads that characterizes this kind of regime.

Structural stability of flexible lines in catenary configuration under torsion

Catenary risers can present during installation a very low tension close to seabed, which combined with torsion moment can lead to a structural instability, resulting in a loop. This is undesirable once it is possible that the loop turns into a kink, creating damage. This work presents a numerical methodology to analyze the conditions of loop formation in catenary risers. Stability criteria were applied to finite element models, including geometric nonlinearities and contact constraint due to riser-seabed interaction. The classical Greenhill's formula was used to predict the phenomenon and parametric analysis shows a ���universal plot��� able to predict instability in catenaries using a simple equation that can be applied for typical risers installation conditions and, generically, for catenary lines under torsion.