Effect of uncertainty of material parameters on stress triaxiality and Lode angle in finite elasto-plasticity—A variance-based global sensitivity analysis

This work establishes a computational framework for the quantification of the effect of uncertainty of material model parameters on extremal stress triaxiality and Lode angle values in plastically deformed devices, whereby stress triaxiality and Lode angle are accepted as key indicators for damage initiation in metal forming processes. Attention is paid to components, the material response of which can be represented as elasto-plastic with proportional hardening as a prototype model, whereby the finite element method is used as a simulation approach generally suitable for complex geometries and loading conditions. Uncertainty about material parameters is characterized resorting to probability theory. The effects of material parameter uncertainty on stress triaxiality and Lode angle are quantified by means of a variance-based global sensitivity analysis. Such sensitivity analysis is most useful for apportioning the variance of the stress triaxiality and Lode angle to the uncertainty on material properties. The practical implementation of this sensitivity analysis is carried out resorting to a Gaussian process regression, Bayesian probabilistic integration and active learning in order to decrease the associated numerical costs. An example illustrates the proposed framework, revealing that parameters governing plasticity affect stress triaxiality and Lode angle the most

Efeito de preparados caseiros no controle da queima-acinzentada, na cultura da cebola Alternative formulations for control of Botrytis squamosa on onion

Agricultores do Alto Vale do Itajaí (SC), vem utilizando preparados caseiros no tratamento fitossanitário da cebola, cuja principal doença, durante a fase de muda, é a queima-acinzentada, causada pelo fungo Botrytis squamosa. Neste trabalho, realizado nos anos de 1993, 94 e 95, no período de muda da cebola, durante a fase de canteiro, avaliou-se o efeito de extratos alcóolicos de Matricaria chamomilla, Mentha glacilis, alho e própolis; cinza vegetal e cal; soluções de B+Zn, KMnO4, NaClO, Sílica-gasil, creolina, formalina; calda sulfocálcica, calda bordalesa, cânfora, enxofre, enxofre+silicato+propólis e o fungo antagonista, Gliocladium roseum, sobre o desenvolvimento da queima-acinzentada. A aplicação dos produtos foi semanal e as concentrações foram ajustadas em ensaio preliminar. O estudo de eficiência mostrou que Gliocladium roseum (108 esporos/ml) igualou-se ao fungicida vinclozolin (0,075%), no controle da queima-acinzentada em 1994/95. No ciclo de 1995/96, maior sobrevivência de plantas e/ou maior número de plantas aptas ao transplante foram obtidos nos tratamentos com cinza vegetal, calda bordalesa (0,5%) e a mistura de enxofre + silicato + extrato de própolis, comparados com o tratamento padrão, com fungicida. As soluções de KMnO4, NaClO, cânfora, enxofre e sílica-gasil não mostraram diferença com a testemunha não tratada. A adubação orgânica de base, em 1995, proporcionou mudas com menor intensidade de B. squamosa e maior índice de sobrevivência das mesmas do que adubação mineral, independentemente da formulação.<br>Santa Catarina State farmers in the "Alto Vale do Itajaí" region are using several home-made products to control onion pests, where leaf blight of onion (Botrytis squamosa) is the main nursery disease. This research was carried out during the nursery period in 1993, 94 and 95, in order to evaluate traditional formulations against leaf blight of onion. The formulations studied were alcoholic extracts of Matricaria chamomilla, Mentha glacilis, garlic and propolis; wood ash, lime, solution of B+Zn, KMnO4, NaClO, "silica-gasil", creoline, formalin, Bordeaux mixture, sulphur, camphor, and the antagonist Gliocladium roseum. The formulations were used weekly in concentrations previously tested to avoid phytotoxicity. In the onion cycle 1994/95, G. roseum (108 spores/ml) reduced leaf blight of onion with the effect comparable to the standard fungicide vinclozolin (0.075%). In 1995/96, the survival of onion and the number of plants suitable for transplanting were highest using wood ash, Bordeaux mixture (0.5%) and a mixture of sulphur + Na2SiO4 + propolis extract, when compared to the fungicide used as a standard treatment. No leaf blight control effect was observed with sprays of KMnO4, NaClO, "camphor", sulphur and "sílica-gasil". Organic fertilizer increased the survival of onion seedlings and reduced Botrytis squamosa, irrespective of formulation, during the 1995/97 period