Integration of Large Deformation Finite Element and Multibody System Algorithms

This paper presents all overview of research and development efforts that art currently being devoted to integrate large deformation finite element formulations with flexible multibody system algorithms. The goal is to develop computer simulation capabilities for the analysis of physics and engineering models with significant details. The successful development of such new and integrated algorithms will also allow modeling and simulation of systems. that cannot be solved using existing computer algorithms and codes. One Of the main difficulties encountered in this integration process is attributed to the,fact that the solution procedures used in finite element codes differ significantly from those used in general-purpose-flexible multibody system codes. Finite element methods employ the corotational formulations that are often used with incremental solution procedures. Flexible multibody computer codes, oil the other hand, do not, in general, use incremental solution procedures. Three approaches are currently being explored by academic institutions and the software industry. In the first approach, gluing algorithms that aim at performing successful simulations by establishing an interface between existing codes are used. Using different coordinates and synchronizing the time stepping are among several challenging problems that art, encountered when gluing algorithms are used. In the second approach, multibody system capabilities are implemented ill existing finite element algorithms that are based oil large rotation vector formulations. For the most part, corotational formulations and incremental solution procedures are used in this case. In the third approach, a new large deformation finite element formulation that call be successfully implemented in flexible multibody system computer algorithms that employ nonincremental solution procedures is introduced. The approach that is now, being developed in several institutions is based on the finite element absolute nodal coordinate formulation. Such a formulation can be systematically implemented in general-purpose flexible multibody system computer algorithms. Nonlinear constraint equations that describe mechanical joints between different bodies call be formulated in terms of the absolute coordinates in a straightforward manner. The coupling between the motion of rigid, flexible, and very flexible bodies call also be accurately described. The successful integration of large deformation finite element and multibody system algorithms will lead to a new generation of computer codes that can be systematical and efficiently used in the analysis of many engineering applications

Jejunal perforation caused by abdominal angiostrongyliasis Perfuração jejunal causada por angiostrongilíase abdominal

The authors describe a case of abdominal angiostrongyliasis in an adult patient presenting acute abdominal pain caused by jejunal perforation. The case was unusual, as this affliction habitually involves the terminal ileum, appendix, cecum or ascending colon. The disease is caused by the nematode Angiostrongylus costaricensis, whose definitive hosts are forest rodents while snails and slugs are its intermediate hosts. Infection in humans is accidental and occurs via the ingestion of snail or slug mucoid secretions found on vegetables, or by direct contact with the mucus. Abdominal angiostrongyliasis is clinically characterized by prolonged fever, anorexia, abdominal pain in the right-lower quadrant, and peripheral blood eosinophilia. Although usually of a benign nature, its course may evolve to more complicated forms such as intestinal obstruction or perforation likely to require a surgical approach. Currently, no efficient medication for the treatment of abdominal angiostrongyliasis is known to be available. In this study, the authors provide a review on the subject, considering its etiopathogeny, clinical picture, diagnosis and treatment.<br>Os autores descrevem caso de angiostrongilíase abdominal em doente adulto que se manifestou como abdômen agudo devido à perfuração de alça jejunal, evento raro, uma vez que esta afecção geralmente envolve o íleo terminal, apêndice, ceco ou cólon ascendente. A doença é causada pelo nematódeo Angiostrongylus costaricensis cujos hospedeiros definitivos são roedores silvestres e os hospedeiros intermediários são caracóis e caramujos. A infecção em humanos é acidental e ocorre pela ingestão de secreção mucóide destes invertebrados presentes em vegetais ou por contato direto com o muco. A angiostrongilíase abdominal é clinicamente caracterizada pela presença de febre prolongada, anorexia, dor no quadrante inferior direito do abdômen e eosinofilia periférica. Embora a doença seja de natureza benigna, seu curso pode evoluir para formas complicadas como a obstrução ou perfuração intestinais que necessitam de tratamento cirúrgico. Atualmente, não há tratamento medicamentoso eficaz para a angiostrongilíase abdominal. Neste estudo, os autores realizam uma revisão desta afecção em relação à sua etiopatogenia, quadro clínico diagnóstico e tratamento