Mixed-Mode I+II fracture characterization of bonded joints using a multi-mode apparatus

Este trabajo está dedicado a la elaboración y diseño de un aparato inspirado en la soluciónpropuesta por Fernlund y Spelt para caracterizar la fractura de las uniones adhesivas bajoaplicaciones de cargas en modo mixto I + II . El aparato permite una fácil variación delmodo de mezcla y cubre todo el rango de combinaciones posibles (I y II).Además, se propone un procedimiento para tratamiento de datos en función del tamaño degrieta, basado en la teoría de la viga y el concepto de grieta equivalente, superando variasdificultades inherentes a los ensayos realizados. El desarrollo se basa en una metodologíade diseño mediante la validación numérica basada en datos experimentales obtenidos conun equipo de ensayo de doble acción en Virginia Tech. Esta metodología se presenta acontinuación, y está validada con la aplicación experimental del aparato.The present work is dedicated to the development and design of a load jig inspired in theproposed solution by Fernlund and Spelt in order to characterize fracture of bonded jointsunder mixed-mode I+II loading. The jig allows for easy alteration of the mode-mixity andpermits covering the full range of mixed-mode I+II combinations. A data reduction schemebased on specimen compliance, beam theory and crack equivalent concept is proposed toovercome several difficulties inherent to the test analysis. The development was based in adesign methodology using numerical validation based on experimental data obtained with aDual Loading Frame from Virginia Tech. . This methodology is presented and then validatedwith the experimental application of the jig

Design and Development of an Adhesive Joint Testing Apparatus for Mixed-Mode Evaluation

The present work is dedicated to the development and design of a load jig inspired in theproposed solution by Fernlund and Spelt in order to characterize fracture of bonded joints undermixed-mode I+II loading. The jig allows for easy alteration of the mode-mixity and permits coveringthe full range of mixed-mode I+II combinations. A data reduction scheme based on specimencompliance, beam theory and crack equivalent concept is proposed to overcome several difficultiesinherent to the test analysis. The development was based in a design methodology using numericalvalidation based on experimental data obtained with a Dual Loading Frame from Virginia Tech. Thismethodology is presented and then validated with the experimental application of the jig

Determination of the envelopes for mode-mixity evaluation of adhesively bonded steel

This study is about the effect of the adhesive thickness and adhesive ductility on the mixed mode loading of DoubleCantilever Beam joints.The project is divided into three main tasks. The first task is about the development of a finite element model using acohesive zone model to design an experimental device based on the standard ASTM D6671D.The second task is concerned with the generation of experimental results in mixed mode varying the type of adhesiveand the adhesive thickness. In the third task, the experimental results will be used to develop an adhesive toughnessmodel as a function of the mode mixity.A dual actuator load frame from Virginia Techs Engineering Science & Mechanics Dept. was used to obtain theenvelopes for mode mixity for three different adhesives and thicknesses.A proposal for a data reduction scheme for the determination of the strain energy release rate is presented and validatedin this paper without the need of the experimental measure of the crack length

Mixed-Mode I + II fracture characterization of bonded joints using a novel Multi-Mode Apparatus

The present work presents the experimental test results to assess the toughness of an adhesive joint, using a previouslydefined crack equivalent data reduction scheme applied to a new multi-mode apparatus, inspired in a load jig previouslydeveloped by Fernlund and Spelt. The patented jig allows for easy alteration of the mode-mixity and permits coveringthe full range of mixed-mode I+II combinations. A data reduction scheme based on specimen compliance, beam theoryand crack equivalent concept is used to overcome several difficulties inherent to the test analysis. The method assumesthat the performed test can be viewed as a combination of the double cantilever beam and asymmetrically loaded endnotchedflexure tests, which provide modes I and II fracture characterization, respectively. A numerical analysisincluding a cohesive mixed-mode I+II damage model was performed considering different mixed-mode loadingconditions to validate the proposed data reduction scheme. Issues regarding self-similar crack growth and fractureprocess zone development are discussed. It was verified that the considered in-plane mix mode fracture criterion is wellcaptured using the proposed data reduction scheme

Geometric Mixing, Peristalsis, and the Geometric Phase of the Stomach

Mixing fluid in a container at low Reynolds number - in an inertialess environment - is not a trivial task. Reciprocating motions merely lead to cycles of mixing and unmixing, so continuous rotation, as used in many technological applications, would appear to be necessary. However, there is another solution: movement of the walls in a cyclical fashion to introduce a geometric phase. We show using journal-bearing flow as a model that such geometric mixing is a general tool for using deformable boundaries that return to the same position to mix fluid at low Reynolds number. We then simulate a biological example: we show that mixing in the stomach functions because of the "belly phase": peristaltic movement of the walls in a cyclical fashion introduces a geometric phase that avoids unmixing.Comment: Revised, published versio

N. elongata Produces Type IV Pili That Mediate Interspecies Gene Transfer with N. gonorrhoeae

The genus Neisseria contains at least eight commensal and two pathogenic species. According to the Neisseria phylogenetic tree, commensals are basal to the pathogens. N. elongata, which is at the opposite end of the tree from N. gonorrhoeae, has been observed to be fimbriated, and these fimbriae are correlated with genetic competence in this organism. We tested the hypothesis that the fimbriae of N. elongata are Type IV pili (Tfp), and that Tfp functions in genetic competence. We provide evidence that the N. elongata fimbriae are indeed Tfp. Tfp, as well as the DNA Uptake Sequence (DUS), greatly enhance N. elongata DNA transformation. Tfp allows N. elongata to make intimate contact with N. gonorrhoeae and to mediate the transfer of antibiotic resistance markers between these two species. We conclude that Tfp functional for genetic competence is a trait of a commensal member of the Neisseria genus. Our findings provide a mechanism for the horizontal gene transfer that has been observed among Neisseria species

Demostración de resultado económico: percepción del comando da aeronáutica de Brasil

No ano de 2010, uma alteração no quadro normativo brasileiro introduziu a Demonstração do Resultado Econômico (DRE) para o setor público, que busca comparar custos internos de produção com valores de mercado, segundo o conceito de custo de oportunidade. Este estudo procura analisar as possíveis respostas estratégicas dos gestores , buscando perceber se a cultura contábil existente no País permite a aceitação do novo instrumento. Por meio das percepções dos agentes públicos do Comando da Aeronáutica (Comaer), no Brasil, conclui-se que a resposta estratégica dos entrevistados tende para a atitude de aceitação da nova rotina, demonstrando traços de menor conservadorismo e maior interesse pela evidenciação de resultados.In 2010, a change in the Brazilian accounting regulatory framework introduced the Demonstração do Resultado Econômico (DRE) [Economic Income Statement] for the public sector, which seeks to compare the internal costs of production to market values, according to the concept of opportunity cost. This study aims to analyse the possible strategic responses of managers and tries to understand if the existing accounting culture in Brazil facilitates the introduction of the new statement. By means of perceptions of officials of the Aeronautical Command (Comaer), in Brazil, it is possible to conclude that the strategic response of respondents is closer to acceptance of the new routine, showing traces of less conservatism and greater interest for displaying results.En el año 2010, una modificación del cuadro normativo brasileño introdujo la Demostración del Resultado Económico (DRE) para el sector público, que busca comparar los costos internos de producción con los valores del mercado, según el concepto de costo de oportunidad. Este estudio tiene como objetivo analizar las posibles respuestas estratégicas de los gestores, con el fin de percibir si la cultura contable existente en el país permite la aceptación del nuevo instrumento. Por medio de las percepciones de los agentes públicos del Comando da Aeronáutica (Comaer), en Brasil, se concluyó que la respuesta estratégica de los entrevistados tiende a aceptar la nueva rutina, mostrando rasgos de menos conservadurismo y más interés por la manifestación de resultados.Fundação para a Ciência e a Tecnologia (FCT