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A finite element-experimental study of the impact of spheres on aluminium thin plates
Giancarlo B. Micheli,Larissa Driemeier,Marcílio Alves 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.55 No.2
This paper describes a study of the collision of hard steel spheres against aluminium thin circular plates at speeds up to 140 m/s. The tests were monitored by a high speed camera and a chronoscope, which allowed the determination of the ballistic limit and the plate deformation pattern. Quasi-static material parameters were obtained from tests on a universal testing machine and dynamic mechanical characterization of two aluminium alloys were conducted in a split Hopkinson pressure bar. Using a damage model, the perforation of the plates was simulated by finite element analysis. Axisymmetric, shell and solid elements were employed with various parameters of the numerical analysis being thoroughly discussed, in special, the dynamic model parameters. A good agreement between experiments and the numerical analysis was obtained.
Kim, T. W.,Barry, J. P.,Micheli, F. Copernicus GmbH 2013 Biogeosciences Vol.10 No.11
<P><p><strong>Abstract.</strong> Exposure of nearshore animals to hypoxic, low-pH waters upwelled from below the continental shelf and advected near the coast may be stressful to marine organisms and lead to impaired physiological performance. We mimicked upwelling conditions in the laboratory and tested the effect of fluctuating exposure to water with low-pH and/or low-oxygen levels on the mortality and growth of juvenile red abalone (<i>Haliotis rufescens</i>, shell length 5&ndash;10 mm). Mortality rates of juvenile abalone exposed to low-pH (7.5, total scale) and low-O<sub>2</sub> (40% saturation, mg L<sup>&minus;1</sup>) conditions for periods of 3 to 6 h every 3-5 days over 2 weeks did not differ from those exposed to control conditions (O<sub>2</sub>: 100% saturation, 12 mg L<sup>−1</sup>; pH 8.0). However, when exposure was extended to 24 h, twice over a 15-day period, juveniles experienced 5-20% higher mortality in the low-oxygen treatments compared to control conditions. Growth rates were reduced significantly when juveniles were exposed to low-oxygen and low-pH treatments. Furthermore, individual variation of growth rate increased when juveniles were exposed simultaneously to low-pH and low-O<sub>2</sub> conditions. These results indicate that prolonged exposure to low-oxygen levels is detrimental for the survival of red abalone, whereas pH is a crucial factor for their growth. However, the high individual variation in growth rate under low levels of both pH and oxygen suggests that cryptic phenotypic plasticity may promote resistance to prolonged upwelling conditions by a portion of the population.</p> </P>