494 research outputs found
Multibeam bathymetry from SONNE cruises SO104 and SO244 and Marcus G. Langseth cruise MGL1610
No full textMultibeam bathymetric data were acquired during R/V SONNE Cruises SO104, SO244, and R/V Marcus G. Langseth Cruise MGL1610. The datasets were individually processed and gridded with grid cell sizes of 75 m. For the combined grid, depth information from SO244 was used wherever possible. If no SO244 data were available, MGL1610 data were preferred over SO104 data
Buckling resistance of multistiffened aluminium plates in compression: experimental and numerical study
No full textCalibration of a constitutive material model for sub-sea pipelines
No full textThe bulk transport of oil and gas are today carried out by pipelines, and the maximum economical and feasible transport distance and installation environment is constantly extended. This has challenged the need for advanced technology for the whole life cycle of pipelines. New design challenges have to be dealt with concerning arctic environmental loads, but also accidental loads such as anchoring, dropped objects, fishing activities, vessel impact, and of course ice gouging. Thus, considering the actual and increasingly high demands for energy and the challenges with respect to inspection, monitoring and repairing, reliable design criteria are fundamental. Here, numerical simulations are important tools, but the reliability of such simulations of pipelines subjected to different load scenarios rely on a proper modelling of the pipe material. Hence, the aim of this paper is the calibration of a suitable constitutive model for a typical material used in a sub-sea pipeline. Starting from a large experimental test matrix, executed on specimens cut directly from a pipe, the calibration of a material model with an anisotropic yield function and a ductile failure criterion is presented in some detail. In particular the choice of a suitable yield surface to take into account the strong anisotropic flow properties found in the experimental tests is underlined
Formation and hydrothermal alteration of a volcanic center: Melt pooling and mass transfers at Langseth Ridge (Gakkel Ridge, Arctic Ocean)
No full textVolcanic centers are characteristic features of ultraslow-spreading mid-ocean ridges, the least-explored parts of the global ridge system. Volcanic centers can provide insights into deep magmatic and metamorphic processes at these ridges. Here, we present data from the largest volcanic center on the Gakkel Ridge, the Langseth Ridge, situated at 60-62 degrees E. Langseth is similar to 10 km wide, consisting of three peaks that rise to 585 m water depth, some 3-4 km above the surrounding seafloor. It strikes perpendicular to Gakkel's spreading direction and can be traced for similar to 40 km, which translates to an age of similar to 8 Myr. Seafloor imaging revealed abundant (pillow) basalt but also fissures and geologic faults across the Langseth Ridge. Basaltic rocks were sampled at all summits and diabase at the slope of the northern summit that dips into the rift valley. Our samples are of normal to depleted mid-ocean ridge basalt composition and exhibit a wide range of major and trace element contents, due to magmatic processes, accumulation of macrocrysts, and hydrothermal alteration. Radiogenic isotope ratios, most notably Nd-143/Nd-144 and Pb-208/Pb-206, trend from typical rift valley compositions to isotopically enriched values with increasing distance to the rift valley. This trend may imply melt pooling from different sources, potentially representing a shift from shallow melting beneath the rift valley to deeper melting of enriched sources and higher degrees of melting underneath Langseth. Mineral compositions and plagioclase sieve textures imply prolonged storage of magma at depth prior to eruption. Hydrothermal alteration occurred over a range of conditions. Basalt from the summits is weakly altered at temperatures 300 degrees C. These assemblages and temperatures are typical for lower crustal levels and imply uplift of the samples of >1 km. Diabase samples from the Afanasenkov Seamount, another volcanic center on the Gakkel Ridge that we investigated for comparison, were altered under comparable conditions. Our findings suggest a combined volcanic-tectonic origin of the studied volcanic centers, potentially implying that such complexes may generally form due to the interplay of magmatism and tectonics. Researching volcanic centers has the potential to further our understanding of both deep and shallow crustal processes at ultraslow-spreading ridges, providing further insights into the role of these centers as linkages between lithosphere and hydrosphere and the (deep) biosphere they sustain
Parameters identification in strain-rate and thermal sensitive visco-plastic material model for an alumina dispersion strengthened copper
No full textThe main objective of this paper is getting strain-hardening, thermal and strain-rate parameters for
a material model in order to correctly reproduce the deformation process that occurs in high strain-rate
scenario, in which the material reaches also high levels of plastic deformation and temperature. In
particular, in this work the numerical inverse method is applied to extract material strength parameters
from experimental data obtained via mechanical tests at different strain-rates (from quasi-static loading
to high strain-rate) and temperatures (between 20 C and 1000 C) for an alumina dispersion
strengthened copper material, which commercial name is GLIDCOP. Thanks to its properties GLIDCOP
finds several applications in particle accelerator technologies, where problems of thermal management,
combined with structural requirements, play a key role. Currently, it is used for the construction of
structural and functional parts of the particle beam collimation system. Since the extreme condition in
which the material could operate, it is fundamental to characterize it in a wide range both in strain-rate
and temperature.
The numerical inverse method used in this work is particularly useful to reproduce experimental
results when the stressestrain fields in the specimen cannot be correctly described via analytical models.
Furthermore this procedure is useful to take into account thermal phenomena generally affecting high
strain-rate tests in which the heat conversion of plastic work produces an adiabatic overheating. So, the
applicability of this method is particularly indicated in special fields, such as aerospace engineering,
ballistic, crashworthiness studies or particle accelerator technologies.
The attention is focused on evaluating the most suitable strategy of material model parameters
optimization to obtain the best fit between experimental data and numerical results. In this regards, it is
important to determine which material model coefficients can be considered as optimization variables
and for each of them the most suitable range of variation.JRC.G.5 - European laboratory for structural assessmen
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