88,195 research outputs found
Notch stress intensity factors in an array of narrow V-Notches under tension by means of local strain energy density and coarse meshes
No full textOn higher order terms and out-of-plane singular mode
No full textIt is well known that in a plate weakened by a through-the-thickness crack and subjected to remote anti-symmetric loading (mode II), the Poisson's effect leads to the generation of a coupled out-of-plane singular mode (mode O). Recent theoretical and numerical analyses have demonstrated that this effect also occurs in plates weakened by pointed V-notches, and it can play an important role in failure initiation especially in the case of large notch opening angles. Dealing with cracked plates the influence of higher order terms tied to mode II loading on the out-of-plane singular mode has not been investigated until now. The aim of this paper is to fill this gap with an accurate analysis of mode II higher order terms and their effects on mode O. © 2011 Elsevier Ltd. All rights reserved.F. Berto, P. Lazzarin and A. Kotousovhttp://www.elsevier.com/wps/find/journaldescription.cws_home/505659/description#descriptio
On coupled fracture modes and three-dimensional fracture mechanics
No full textA. Kotousov, P. Lazzarin, F. Berto, L.P. Poo
A criterion based on the local strain energy density for the fracture assessment of cracked and V-notched components made of incompressible hyperelastic materials
No full textThe present contribution is devoted to the theoretical and numerical study of the elasto-static fields at a vertex notch under mode I loading. The analysis is based on the plane deformation hyperelasticity theory for an incompressible Mooney-Rivlin material. While for cracked components some contributions can be found in the recent and past literature, studies on V-notched components are instead very limited. The aim of this paper is to partially fill this lack, providing a fracture criterion for the assessment of components weakened by sharp V-notches. In the first part of the paper, a brief description of the analytical frame available for V-notches in hyperelastic material is reported. A Williams' type diagram reporting the degree of singularity for a material obeying a Mooney-Rivlin behavior is present. The asymptotic stress field and the local strain energy density are investigated by means of non-linear finite element analyses. In the second part of the paper, a criterion based on the local energy is proposed and successfully applied to a set of experimental data taken from the literature. Future works are surely necessary to validate the criterion considering more sets of data from sharp and blunt V-notches
On a coupled mode at sharp notches subjected to anti-plane loading
No full textWhen a crack or sharp notch is subjected to anti-plane shear loading the boundary conditions negate the transverse shear stress components at the free surfaces and generate a coupled in-plane shear stress field, which can be singular. For sharp V-notches with zero notch opening angle (or cracks) this 3D phenomenon was known for a long period of time. However this mode was largely ignored in stress analysis of notched components. Till now it is still unclear how significant this mode is and whether it has to be taken into consideration in integrity and failure analysis of engineering structures. The present paper is aimed to investigate this singular mode by means of the 3D Finite Element method, which is applied to notched plates with different notch opening angles and plate thicknesses. The stress state associated with the coupled mode is localised and quickly decays with the distance from the notch tip. Therefore, the obtained theoretical results can be applied to a wide range of notched components provided that the boundaries are sufficiently far from the notch tip. Among these results is the effect of the plate thickness on the intensity of the coupled mode; the latter increases with the decrease of the plate thickness. Significance of these new results to failure and integrity assessments of plate and shell components with sharp notches, including through-the-thickness cracks, is discussed in the final section of the paper. © 2012 Elsevier Masson SAS. All rights reserved.Filippo Berto, Andrei Kotousov, Paolo Lazzarin, Fabio Pegori
Corrigendum to ‘Human corpse model for video-assisted thoracoscopic lobectomy simulation and training’ [Interact CardioVasc Thorac Surg 2020; doi:10.1093/icvts/ivaa169]
No full textIn the originally published version of this article, the surname of Dr Boscolo-Berto was incorrectly formatted and thus incorrectly indexed as Berto RB. This has now been corrected in the article
Al Berto e F. Antonino Bacelar: o erotismo em devaneio
No full textEm um trabalho de teor comparatista, pretende-se fazer a leitura das obras do poeta português Al Berto, O Medo, de 2009, e do amazonense F. Antonino Bacelar, Na flor do maracujá: contos e poemas, de 2010, averiguando a forma que ambos expressam o erotismo em seus poemas. Al Berto, por exemplo, se utiliza das manifestações homoafetivas, em meio ao devaneio, ao delírio, e ao real, instituindo, assim, uma nova dicção no fazer poético contemporâneo de Portugal. Enquanto F. Antonino Bacelar ilustra experiências e sonhos eróticos cujos momentos pueris retornam por meio das recordações de figuras femininas, com corpos sensuais e olhar inebriante, revelando voluptuosos instantes de prazer na juventude. Para tanto, serão utilizadas obras teóricas que sustentem os objetivos deste estudo, como Ética, sexualidade e política, de Michel Foucault, Leituras do sexo, organizado por Christine Greiner e Claudia Amorim, além de Literatura e homoerotismo em questão, de José Carlos Barcellos e A dupla chama: amor e erotismo, de Octávio Paz.
Fibras de vidro a base de Li20 - Zr02 - BaO - Si02 recobertas com Nb205 para utilização em micro-extração em fase sólida
Full text linkTese (doutorado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas. Programa de Pós-graduação em QuímicaNeste trabalho são descritas as metodologias para obtenção e modificações da superfície de fibras de vidro de composição Li2O-ZrO2-BaO-SiO2. Apresenta-se também as aplicações destas fibras na determinação, por SPME, de fenol e de uma mistura de álcoois. Para obtenção das fibras de vidro construiu-se um equipamento, o qual baseia-se na técnica de estiramento. As fibras de vidro foram recobertas utilizando-se duas técnicas: Decomposição de Organometálicos, onde o etóxido de nióbio (V) foi empregado como reagente precursor do óxido de nióbio (V), e Deposição de Vapor Químico, na qual fez-se uso do cloreto de nióbio como precursor do óxido de nióbio (V).Utilizou-se da técnica de Microscopia Eletrônica de Varredura para avaliar a morfologia das fibras sem recobrimento e recobertas. O recobrimento com óxido de nióbio sobre a superfície das fibras foi estudado pela técnica de "Color Map" e as análises químicas realizadas pela Microssonda de Energia Dispersiva, ambas as técnica acopladas ao MEV. A Técnica de Micro-extração em Fase Sólida foi utilizada para avaliar a capacidade de adsorsão de compostos polares e apolares pelas fibras recobertas. Com os resultados obtidos, verficou-se que pela técnica de CVD obtem-se fibras com um recobrimento mais homogêneo e espesso. Estas fibras apresentaram melhor eficiência no processo de adsorção como verificado pelos resultados cromatográficos
A simplified extension of the Crack Analogue model for fretting fatigue with varying normal load
No full textThe stress concentration induced by fretting is studied with a simple "Crack Analogue" model (CA), vaguely inspired by the original CA proposed by MIT 20 years ago, "improved" by the first author to take into account simply both contact loads and bulk stresses loads, and even the case of finite stress concentration in the so-called "Crack Like Notch Analogue" (CLNA) model. We suggest here a very crude extension to include the case of varying normal load, where we don't attempt to solve the contact mechanics problem rigorously, only providing an estimate of the equivalent Stress Intensity Factor from the instantaneous load and contact area. Even this results in a problem which has no equivalent in standard fatigue, since it corresponds to a "crack" that is oscillating in size at each cycle. This defines the cycles of stress in the actual material points in the fretted area, but the uncertainties in the approximations suggest that only some limit cases should be approaches this way: for example, when the peaks of tangential load are obtained at about a "mean contact area" (out-of-phase loading) then the original CLNA model could be used
- …
