Okumus, S. Cem; Karslioglu, Ramazan; Akbulut, Hatem
Aluminum-lithium based unreinforced (Al-8090) alloy and Al-8090/SiCp/17 vol.% metal matrix composite produced by extrusion after spray co-deposition. A dry ball-on disk wear test was carried out for both alloy and composite. The tests were performed against an Al2O3 ball, 10 mm in diameter, at room temperature and in laboratory air conditions with a relative humidity of 40-60%. Sliding speed was chosen as 1.0 ms-1 and normal loads of 1.0, 3.0 and 5.0 N were employed at a constant sliding distance of 1000 m. The wear damage on the specimens was evaluated via measurement of wear depth and diameter. Microstructural and wear characterization was carried out via scanning electron microscopy (SEM). The results showed that wear loss of the Al-8090/SiC composite was less than that of the Al-8090 matrix alloy. Plastic deformation observed on the wear surface of the composite and the matrix alloy, and the higher the applied load the greater the plastic deformation. Scanning electron microscopy examinations of wear tracks also reveal that delamination fracture was the dominant wear mechanism during the wear progression. Friction coefficient was maximum at the low applied load in the case of the Al-8090/SiC composite while a gradual increase was observed with applied load for the matrix alloy.
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about recreational and commercial vessel accidents, including on- water collisions, allisions, and pollution discharge incidents. Accidents that involve...engineering, geospatial sciences, water resources, and environmental sciences for the Army, the Department of Defense, civilian agencies, and our nation’s...26 Figure 4. A) U.S. export and import value transported via water : 2007-2013; B) U.S. export
Copping, Andrea [Coastal Division, Pacific Northwest National Laboratory, Seattle Washington USA; Breithaupt, Stephen [Coastal Division, Pacific Northwest National Laboratory, Seattle Washington USA; Whiting, Jonathan [Coastal Division, Pacific Northwest National Laboratory, Seattle Washington USA; Grear, Molly [Coastal Division, Pacific Northwest National Laboratory, Seattle Washington USA; Tagestad, Jerry [Coastal Division, Pacific Northwest National Laboratory, Seattle Washington USA; Shelton, Gregory [Shelton International, Seattle Washington USA
Offshore wind energy development is planned for areas off the Atlantic coast. Many of the planned wind development areas fall within traditional commercial vessel routes. In order to mitigate possible hazards to ships and to wind turbines, it is important to understand the potential for increased risk to commercial shipping from the presence of wind farms. Using Automatic Identification System (AIS) data, historical shipping routes between ports in the Atlantic were identified, from Maine to the Florida Straits. The AIS data were also used as inputs to a numerical model that can simulate cargo, tanker and tug/towing vessel movement along typical routes. The model was used to recreate present day vessel movement, as well as to simulate future routing that may be required to avoid wind farms. By comparing the present and future routing of vessels, a risk analysis was carried out to determine the increased marginal risk of vessel collisions, groundings, and allisions with stationary objects, due to the presence of wind farms. The outcome of the analysis showed little increase in vessel collisions or allisions, and a decrease in groundings as more vessels were forced seaward by the wind farms.