Finite element modeling of laser assisted friction stir welding of carbon steels for enhanced sustainability of welded joints

Part of: Seliger, Günther (Ed.): Innovative solutions : proceedings / 11th Global Conference on Sustainable Manufacturing, Berlin, Germany, 23rd - 25th September, 2013. - Berlin: Universitätsverlag der TU Berlin, 2013. - ISBN 978-3-7983-2609-5 (online). - http://nbn-resolving.de/urn:nbn:de:kobv:83-opus4-40276. - pp. 247-251.In Friction stir welding (FSW) of carbon steels, process parameters must be set to avoid defects such as warm holes. Proper selection of process parameters also affects the final grain microstructure and phase transformations and, ultimately, the weld’s mechanical properties. Process parameters, including laserassisted heating, of AISI 1045 carbon steel were investigated via a 3D finite element method (FEM) model. The laser action was modeled as heat source with constant flux. The simulation findings favorably agree with experiments reported in the literature and suggesting that with laser-assisted-FSW welding can be performed at higher traverse speeds (400 vs. 100 mm/min) while maintaining defect free weld. Also, evolved phase transformations are predicted across the weld geometry as time progresses. Such findings will help in the prediction of sound welding parameters and in estimating the mechanical properties of the various regions of the weld leading to more sustainable joints

Organic carbon export and loss rates in the Red Sea

The export and fate of organic carbon in the mesopelagic zone are still poorly understood and quantified due to lack of observations. We exploited data from a BGC‐Argo float that was deployed in the Red Sea to study how a warm and hypoxic environment can affect the fate of the organic carbon in the ocean’s interior. We observed that only 10% of the particulate organic carbon (POC) exported survived at depth due to remineralization processes in the upper mesopelagic zone. We also found that POC exported was rapidly degraded in a first stage and slowly in a second one, which may be dependent on the palatability of the organic matter. We observed that AOU‐based loss rates (a proxy of the remineralization of total organic matter) were significantly higher than the POC‐based loss rates, likely because changes in AOU are mainly attributed to changes in dissolved organic carbon. Finally, we showed that POC‐ and AOU‐based loss rates could be expressed as a function of temperature and oxygen concentration. These findings advance our understanding of the biological carbon pump and mesopelagic ecosystem

Low-cost, biodegradable and highly effective adsorbents for batch and column fixed bed adsorption processes of methylene blue

This work reports the preparation of low-cost and ecological bioadsorbents and study of their adsorption properties in the elimination of methylene blue dye (MB) from wastewater Unmodified citrus peels (UCP) and unmodified citrus peels encapsulated with calcium alginate (UCP/A) were characterized by elementary analysis, FTIR, DRX, SEM. Isotherm studies in the batch system were investigated and the maximum adsorbed amounts were found to be 185.83 and 964.54 mg/g respectively for UCP and UCP/A. The Langmuir model fitted well experimental data of isotherms with high coefficient correlation R-2, low RMSE and chi(2). Fixed bed adsorption was studied with operational conditions such as the bed height, MB flow rate and MB inlet concentration to test the performance of column. The breakthrough curves and the break time increase with the decrease of the rate flow and with the increased bed height. The highest bed capacity of 31.45 mg/g and highest percentage of MB solution treated (93.6%) was obtained using 2 mL/min rate flow, 200 mg/L inlet MB concentration and 3.5 cm (4 g) bed height. The breakthrough curves were fitted using Thomas and Yoon and Nelson models. The behaviors of the breakthrough and the R-2 founded by these models are high (R-2 > 0.97) which shows good applicability of models