Mechanical Engineering
Permanent URI for this communityhttp://hdl.handle.net/1903/2263
Browse
2 results
Search Results
Item An Analysis of the Coast Guard's Surface Fleet Reliability Program for Medium Endurance Cutters(2011) Koski, Heidi Landry; Herrmann, Jeffrey; Reliability Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The United States Coast Guard continues to conduct major environmental and humanitarian response efforts in addition to the other mandated missions that must be performed. In 2009, the Coast Guard Surface Forces Logistics Center implemented a reliability engineering program in an effort to improve the availability of its aging surface fleet. This thesis is an exploratory analysis of the current status of the newly implemented reliability engineering program using Soft Systems Methodology (SSM) and statistical analysis techniques with the objective of determine how the shift to reliability-centered maintenance approaches and procedures has affected the availability of the medium endurance cutters, which have long been the workhorses of the modern Coast Guard. A key goal of this work is to determine what improvements can be made to the current reliability engineering program to enable the US Coast Guard to better achieve its mission. The SSM analysis discovered several key issues including procedures, personnel training, data mining, and data reporting. Further, the analysis led to examination of eight (8) years of cutter machinery failure data as a measure to transform cutter maintenance activities into constructive mission availability information using Goal Tree - Success Trees and Boolean logic. This preliminary analysis revealed lower than desired availability percentages and a decrease in cutter availability over time. The root causes for these results are examined and found to include program implementation issues, lack of proper training, a lack of adequate funding, the age of existing fleet assets, and the Coast Guard culture. Key research questions are answered and several key opportunities for improvement are identified. Several next steps or areas for future work are proposed. A more detailed analysis of the maintenance data could assist in improving the allocation of maintenance funding and logistics support. Additionally, analyzing the data by cutter operating location and associated maintenance costs could provide useful information regarding resource allocation. With the completion of these steps, the Coast Guard can adapt its program to fit the needs of the service.Item Physics of Breaking Bow Waves: A Parametric Investigation using a 2D+T Wave Maker(2009) Maxeiner, Eric; Duncan, James H; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)A mechanical 2-dimensional wave maker with a flexible surface was used to create waves similar to those formed at the bow of a moving ship. Utilizing the 2D+T approximation, the wave maker was programmed so that its deformable wave board creates a time sequence of shapes that simulate the line of intersection between one side of the hull of a slender ship model moving at constant speed and an imaginary vertical plane oriented normal to the ship model track. Instead of trying to simulate a particular ship hull, however, the wave maker simulates a parametric set of flat plate motions that contain components of typical bow shapes. The resulting surface waves were measured using a cinematic laser-induced fluorescence technique and the resulting wave profiles were analyzed. A tremendous variation of wave shapes was observed. A variety of wave characteristics including the peak contact point height, peak wave height, wave crest speed and plunging jet thickness distribution were measured and related to the corresponding wave maker motion parameters. Despite the complexity of the wave maker motions, it was observed that wave maker velocity and acceleration along the water line were the wave maker parameters with the strongest influence on many of the measured wave characteristics. Additional analysis reveals that the initial acceleration of the wave maker affects some wave characteristics, especially those related to plunging jet behavior, but does not significantly affect the overall size and shape of the wave. It was also observed that the behavior of wave formation and breaking ranged between two distinct modes. The first mode consists of an overdriven wave that contains a pronounced vertical jet along the face of the wave maker. The overdriven wave breaks close to the wave maker, before a wave crest has fully formed. The second mode is a more slowly developing wave that breaks further away from the wave maker. The developing waves do not contain the pronounced vertical jet observed in overdriven waves. The two modes appear to be related to the initial wave maker acceleration and amount of water displaced by the wave maker.