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Oslo, Norway

Ramirez J.E.,DNVGL
Welding Journal | Year: 2014

Ti-clad steel welded joints made with different interlayer material-joining process combinations were evaluated using microhardness, bend, and shear-bond strength testing. The effect of thermal cycling on the shear-bond strength was evaluated as well. In general, all the welded joints present the highest hardness level at the interlayer-Ti interface and across the first Ti layer. The maximum hardness in welded joints made with the Ni-Ti, NiCu-Ti, and NiCr-Ti interlayer systems was 607,568, and 554 HV0.5, respectively. In the V-Ti and Ti-V systems, the respective maximum hardnesses were 307 and 409 HV0.5, respectively, at the Fe-V interface. The maximum hardness observed in welded joints made with the Cu-Ti interlayer ranged from 300 to 350 HV0.5. Different softening responses to either thermal cycles of additional Ti layers or PWHT were observed in different types of joints. Most of the joints failed the bend tests in the as-welded and PWHTed conditions. The Ni-Ti-, NiCu-Ti-, and NiCr-Ti-welded joints failed along the interlayer-Ti interface and through the Ti weld layers. The Cu-Ti welded joints made with the CSC-GMAW process failed along the Cu-Ti interface. The bond-shear strength of both Fe-Cu and Cu-Ti interfaces in Cu-Ti welded joints made with a combination of CSC-GMAW and GTAW-P processes in the as-welded, PWHTed, and thermally cycled conditions ranged from 204.5 to 259.8 MPa (29.6 to 37.6 ksi). The Fe-Cu interface showed a larger displacement under maximum load as compared to that observed in the Cu-Ti interface.

Storhaug G.,DNVGL
International Journal of Naval Architecture and Ocean Engineering | Year: 2014

Whipping/springing research started in the 50’ies. In the 60’ies inland water vessels design rules became stricter due to whipping/springing. The research during the 70-90’ies may be regarded as academic. In 2000 a large ore carrier was strengthened due to severe cracking from North Atlantic operation, and whipping/springing contributed to half of the fatigue damage. Measurement campaigns on blunt and slender vessels were initiated. A few blunt ships were designed to account for whipping/springing. Based on the measurements, the focus shifted from fatigue to extreme loading. In 2005 model tests of a 4,400 TEU container vessel included extreme whipping scenarios. In 2007 the 4400 TEU vessel MSC Napoli broke in two under similar conditions. In 2009 model tests of an 8,600 TEU container vessel container vessel included extreme whipping scenarios. In 2013 the 8,100 TEU vessel MOL COMFORT broke in two under similar conditions. Several classification societies have published voluntary guidelines, which have been used to include whipping/springing in the design of several container vessels. This paper covers results from model tests and full scale measurements used as background for the DNV Legacy guideline. Uncertainties are discussed and recommendations are given in order to obtain useful data. Whipping/springing is no longer academic. © 2014, Society of Naval Architects of Korea. All rights reserved.

Kamal R.H.,DNVGL | Coop M.R.,City University of Hong Kong | Jardine R.J.,Imperial College London | Brosse A.,Geotechnical Consulting Group
Geotechnique | Year: 2014

A detailed study is described of the post-yield behaviour of four medium-plastioity heavily over-consolidated UK stiff clays. Sub-layers of the stiff-to-hard Gault, Kimmeridge and Oxford clays were identified, sampled and tested; these, along with fades investigated in an earlier London Clay study, had broadly similar depositional histories. The intention in considering a spread of similar sediments from the Jurassic to the Eocene was to allow any strong effects of geological age, or burial depth, to be identified. A strongly fissured meso-structure was present in three of the four clays, which had a controlling influence on their effective shear strengths, considering that the representative element volume is of paramount importance in measuring the strengths of such soils. All four soils were brittle in shear and, when sheared to sufficient displacements, developed low residual shear strengths. The stiff clays were investigated further through comparisons between natural and reconstituted behaviour, using the latter to normalise the effective stress data for volume and also considering the clays' oedometer swell sensitivities, Normal compression tests, when normalised for void index, implied different degrees of ‘structure’ than undrained shear tests, showing that a more elaborate micro- and meso-fabric framework is needed to capture the behaviour of highly overconsolidated and aged geomaterials. This paper focuses on describing the study sites’ geotechnical profiles and the stiff clays' yielding behaviours under one-dimensional compression and in triaxial compressive shear. © 2014, (publisher). All rights reserved.

Jun J.,Ohio State University | Frankel G.S.,Ohio State University | Sridhar N.,DNVGL
Journal of Solid State Electrochemistry | Year: 2015

Diffusion-controlled pit growth of Super 13Cr stainless steel (S13Cr) was studied using a one-dimensional (1D) pit electrode in 0.1–3 M NaCl solutions at 85 °C. High anodic potential was applied to dissolve 1D S13Cr electrode to a target pit depth. Removal and reprecipitation of salt film on the growing 1D pit was then performed by applying low and high anodic potential in sequence. Finally, the potential of the 1D pit was scanned downward until the pit stopped growing. Diffusion-limited current density measured during pit growth and calculated pit depth were used to determine the product of diffusion coefficient (D) and saturation concentration (Csat) of metal ion. D∙Csat value decreased as bulk NaCl concentration increased. A pit dissolution model incorporating the effect of bulk NaCl concentration and temperature on D and Csat was developed for comparison of the results. The D∙Csat value predicted from the pit model resulted in a good fit with the D∙Csat value determined experimentally for different NaCl concentrations. To evaluate the effect of temperature on pit growth, D∙Csat values obtained in different temperatures were compared. The value of D∙Csat was found to increase at higher temperature because of higher Csat and larger D. © 2015, Springer-Verlag Berlin Heidelberg.

Abi-Samra N.,DNVGL | McConnach J.,Castle Hill Engineering Services | Mukhopadhyay S.,GT B Institute of Technology | Wojszczyk B.,Manila Electrical Company
IEEE Power and Energy Magazine | Year: 2014

Preparing for, responding to, coping with, and managing the aftermath of severe impacts on electrical power system grids due to extreme weather events resulting from climate change are all receiving growing attention. Recent severe events in North America and across the globe have stressed the ability of electrical utilities to maintain the continuity and reliability of supply, with many customers experiencing extended power outages. Hurricane Sandy, recent severe winter snow and ice storms in the northeastern United States and eastern Canada, Supercyclone Phailin in India, and Typhoon Haiyan in the Philippines are prime examples. This article is sponsored by members of the Climate Change Technology Subcommittee of the IEEE Power & Energy Society Energy Development and Power Generation Committee, whose chair is Tom Baumann. © 2014 IEEE.

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