Tension fatigue analysis and life prediction for composite laminates

A tension fatigue life prediction methodology for composite laminates is presented. Tension fatigue tests were conducted on quasi-isotropic and orthotropic glass epoxy, graphite epoxy, and glass/graphite epoxy hybrid laminates. Edge delamination onset data were used to generate plots of strain energy release rate as a function of cycles to delamination onset. These plots were then used along with strain energy release rate analyses of delaminations initiating at matrix cracks to predict local delamination onset. Stiffness loss was measured experimentally to account for the accumulation of matrix cracks and for delamination growth. Fatigue failure was predicted by comparing the increase in global strain resulting from stiffness loss to the decrease in laminate failure strain resulting from delaminations forming at matrix cracks through the laminate thickness. Good agreement between measured and predicted lives indicated that the through-thickness damage accumulation model can accurately describe fatigue failure for laminates where the delamination onset behavior in fatigue is well characterized, and stiffness loss can be monitored in real time to account for damage growth

PODA VERDE NA PRODUÇÃO E QUALIDADE DE UVA CV. RUBI (Vitis vinifera L.) NO NORTE DO ESPÍRITO SANTO

A produção de uvas vem ganhando, cada vez mais, destaque na economia do Brasil. O nordeste brasileiro é responsável pela produção das melhores uvas finas de mesa do Brasil, inclusive com qualidade que possibilita a exportação para vários países do mundo. Portanto, não é uma novidade o cultivo da uva em regiões quentes, o que não existia ainda, eram pesquisas com a uva no norte capixaba. A videira Vitis Vinifera L. cv. Rubi é uma das uvas de mesa mais importantes no Brasil. Para o seu cultivo, temos o sistema de poda verde (desponte) que é realizada em videiras com o objetivo de equilibrar o desenvolvimento vegetativo e a produção, visando à alta produtividade e à melhoria da qualidade da uva. Devido à falta de parâmetros científicos em relação à uva cv. Rubi no estado do Espírito Santo, o experimento teve como objetivo avaliar o número ideal de folhas que deve ser deixado nos ramos para se obter melhor produtividade e qualidade de frutos para as condições encontradas na região. O experimento foi conduzido no Sítio São Lázaro, bairro Córrego do Ribeirão, município de São Mateus ES, no período de fevereiro de 2011 a agosto de 2012, com a videira cv. Rubi. O delineamento foi em blocos casualizados, com 5 tratamentos e 4 repetições, e as médias comparadas pelo teste de Tukey ao nível de 5% de probabilidade. Os tratamentos foram compostos de 15,20, 25, 30 folhas seguidas e 22 folhas alternadas, sendo que os ramos foram cortados a partir da última folha contada de cada tratamento. Foram avaliados 5 cachos por repetição, sendo que foi estabelecido um total de 50 bagas por cacho para uniformizá-los. As variáveis avaliadas nos tratamentos foram as características física e química dos cachos e da uva, características fisiológicas da folha e a média de crescimentos dos ramos. Depois de colhidos, os cachos e as folhas foram levados ao laboratório de Fitotecnia do Centro Universitário Norte do Espírito Santo - CEUNES para realização das análises. Após os resultados das análises, verificou-se que o número de folhas deixados através da poda verde (desponte) não influenciou a massa média dos cachos, porém, influenciou no número médio de cachos produzidos por planta, e no comprimento dos cachos, ou seja, influenciando diretamente na produtividade. O diâmetro da baga, o número de sementes por baga e a porcentagem não foram influenciados pelos tratamentos (número de folhas). As características químicas das bagas não foram influenciadas pelos tratamentos. O tratamento com 15 folhas proporcionou aumento na área foliar e também no teor de clorofila a, clorofila b e clorofila total. O crescimento dos ramos não foi influenciado pelos tratamentos, porém, os ramos que apresentavam cachos mostraram maior crescimento e consequentemente maior formação de novas folhas. Com isso, conclui-se que o desponte não influencia na qualidade dos frutos, mas sim na produtividade da videira cv. Rubi, em que 25 folhas obteve a maior produtividade comparado com os demais tratamentos

General relativistic radiation hydrodynamics of accretion flows: II. Treating stiff source terms and exploring physical limitations

We present the implementation of an implicit-explicit (IMEX) Runge-Kutta numerical scheme for general relativistic hydrodynamics coupled to an optically thick radiation field in two existing GR-hydrodynamics codes. We argue that the necessity of such an improvement arises naturally in astrophysically relevant regimes where the optical thickness is high as the equations become stiff. By performing several 1D tests we verify the codes' new ability to deal with this stiffness and show consistency. Then, still in 1D, we compute a luminosity versus accretion rate diagram for the setup of spherical accretion onto a Schwarzschild black hole and find good agreement with previous work. Lastly, we revisit the supersonic Bondi Hoyle Lyttleton (BHL) accretion in 2D where we can now present simulations of realistic temperatures, down to T~10^6 K. Here we find that radiation pressure plays an important role, but also that these highly dynamical set-ups push our approximate treatment towards the limit of physical applicability. The main features of radiation hydrodynamics BHL flows manifest as (i) an effective adiabatic index approaching gamma_effective ~ 4/3; (ii) accretion rates two orders of magnitude lower than without radiation pressure; (iii) luminosity estimates around the Eddington limit, hence with an overall radiative efficiency as small as eta ~ 10^{-2}; (iv) strong departures from thermal equilibrium in shocked regions; (v) no appearance of the flip-flop instability. We conclude that the current optically thick approximation to the radiation transfer does give physically substantial improvements over the pure hydro also in set-ups departing from equilibrium, and, once accompanied by an optically thin treatment, is likely to provide a fundamental tool for investigating accretion flows in a large variety of astrophysical systems

A novel approach to damage localisation based on bispectral analysis and neural network

The normalised version of bispectrum, the so-called bicoherence, has often proved a reliable method of damage detection on engineering applications. Indeed, higher-order spectral analysis (HOSA) has the advantage of being able to detect non-linearity in the structural dynamic response while being insensitive to ambient vibrations. Skewness in the response may be easily spotted and related to damage conditions, as the majority of common faults and cracks shows bilinear effects. The present study tries to extend the application of HOSA to damage localisation, resorting to a neural network based classification algorithm. In order to validate the approach, a non-linear finite element model of a 4-meters-long cantilever beam has been built. This model could be seen as a first generic concept of more complex structural systems, such as aircraft wings, wind turbine blades, etc. The main aim of the study is to train a Neural Network (NN) able to classify different damage locations, when fed with bispectra. These are computed using the dynamic response of the FE nonlinear model to random noise excitation

Nucleon isovector structure functions in (2+1)-flavor QCD with domain wall fermions

We report on numerical lattice QCD calculations of some of the low moments of the nucleon structure functions. The calculations are carried out with gauge configurations generated by the RBC and UKQCD collaborations with (2+1)-flavors of dynamical domain wall fermions and the Iwasaki gauge action ($\beta = 2.13$). The inverse lattice spacing is $a^{-1} = 1.73$ GeV, and two spatial volumes of ((2.7{\rm fm})^3) and ((1.8 {\rm fm})^3) are used. The up and down quark masses are varied so the pion mass lies between 0.33 and 0.67 GeV while the strange mass is about 12 % heavier than the physical one. The structure function moments we present include fully non-perturbatively renormalized iso-vector quark momentum fraction, (_{u-d}), helicity fraction, (< x >_{\Delta u - \Delta d}), and transversity, (_{\delta u - \delta d}), as well as an unrenormalized twist-3 coefficient, (d_1). The ratio of the momentum to helicity fractions, (_{u-d}/_{\Delta u - \Delta d}), does not show dependence on the light quark mass and agrees well with the value obtained from experiment. Their respective absolute values, fully renormalized, show interesting trends toward their respective experimental values at the lightest quark mass. A prediction for the transversity, (0.7 _{\delta u -\delta d} < 1.1), in the (\bar{\rm MS}) scheme at 2 GeV is obtained. The twist-3 coefficient, (d_1), though yet to be renormalized, supports the perturbative Wandzura-Wilczek relation.Comment: 14 pages, 22 figures

Study of quasi-1D SnO2 nanowires

The descriptions of SnO2 nanowires growth procedures are getting more and more frequent in the current literature. However, studies on the growth mechanisms are still lacking. In particular, no investigation has been reported on the growth process when the growth mechanisms are not based, as in the case of whiskers, on vapour-liquid-solid (VLS) transitions. In this paper, a new procedure is reported by the authors for growing SnO2 nanowires, based on the presence of liquid-tin droplets on the substrate. The Sn vapour pressure developed by these droplets, which find themselves very close to the growing tip of the wire, gives rise to a sufficiently high supersaturation to enable the fast growth rate usually observed. The principal features and results of this new procedure, as well as possible growth mechanisms, are also discussed

Accessing High Momentum States In Lattice QCD

Two measures are defined to evaluate the coupling strength of smeared interpolating operators to hadronic states at a variety of momenta. Of particular interest is the extent to which strong overlap can be obtained with individual high-momentum states. This is vital to exploring hadronic structure at high momentum transfers on the lattice and addressing interesting phenomena observed experimentally. We consider a novel idea of altering the shape of the smeared operator to match the Lorentz contraction of the probability distribution of the high-momentum state, and show a reduction in the relative error of the two-point function by employing this technique. Our most important finding is that the overlap of the states becomes very sharp in the smearing parameters at high momenta and fine tuning is required to ensure strong overlap with these states.Comment: 10 page