Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1995. / Includes bibliographical references. / by Timothy John McCoy. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1994. / Includes bibliographical references (p. 90). / by Kirko Kimitar Kirkov. / M.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1994. / Includes bibliographical references (leaves 154-157). / by Joseph E. Bondaryk. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1994. / Includes bibliographical references (p. 123-125). / by Charles J. Gerard. / M.S.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 2005. / Includes bibliographical references (p. 129-131). / The dynamics of flapping remains a subject a great theoretical and practical interest. Propulsion and maneuvering by flapping, optimized through years of evolution, is ubiquitous in nature, yet marine pulsars inspired by examples of highly maneuverable marine life or aquatic birds remain unheard of. The motivation of this research stems from the notion that better propulsive strategies could be obtained from flapping foils; presenting superior alternatives to the conventional propeller for waterborne propulsion. The propulsive properties of a Nasa 0012 linearly tapered rigid foil, with a .5.5 cm average chord and 24.6 cm span performing a combined roll and pitch motion are investigated. The mean planform area thrust coefficient and efficiency are recorded over a paramtetric space that included three roll amplitudes, with induced heave (at 0.7 span) to chord ratio, ḣ₀.₇ / c = 1.0, 1.5 and 2.0; Strouhal numbers ranging from 0.2 to 0.6 and maximum angle of attack varying from 15 to 45 degrees. Results show that a maximum planform area thrust coefficient of 2.09 is achieved at h₀.₇ / c = 1.5, St = 0.6 and ,[alpha][max] = 30⁰. The thrust and efficiency data also reveal a useful performance trend where at low [alpha][max], high thrust and efficiency can be gained at sufficiently high Strouhal numbers. / (cont.) DPIV is next used to study the vortical signature created by the flapping foil. Two planes of view, at mid- and 0.8 span were recorded over regimes of low and high thrust. Results show that the vortex patterns are heavily influenced by the foil geometry and kinematics. Three distinct patterns were observed. In particular, the interaction from the shedding of a mixed vortex pair in the wake unveils evidence of strong thrust production. Vorticity control through the replication of this wake vortex pattern can potentially offer optimal solutions for flapping foil propulsion. / by Keith K.L. Lim. / S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 2005. / Includes bibliographical references (p. 391-402). / One of the most important failure modes of thin-walled structures is fracture. Fracture is predominantly tensile in nature and, in most part, is operated by the physical mechanisms of void nucleation, growth, and linkage. For ductile sheet, fracture is preceded by necking. Prediction of necking which limits sheet metal formability is well established and has been developed over the past several decades. However, an in-depth understanding of the mechanical process inside the neck leading to sheet metal fracture is lacking. This is true for both static and high intensity, short duration loads. Furthermore, there is an ever increasing need to raise the safety envelope of existing protective structures against localized extreme loading. The present thesis addresses four parts of the many outstanding issues in sheet metal fracture. In the first part, the new Bao-Wierzbicki (BW) fracture criterion formulated in terms of the accumulated equivalent plastic strain with the stress triaxiality as a weighting function is considered. Using the equations of plane stress von-Mises plasticity and the strain-to-stress mapping procedure, the BW fracture criterion is transformed to the spaces of the principal tensile strains and stresses in a sheet and compared with experimental results for various materials. An extensive comparative study of the most widely used fracture criteria is then conducted. / (cont.) The applicability and expected errors of those criteria are investigated. In the second part, calibration methods for the determination of the stress-strain curve after necking and critical damage parameters are discussed. Most importantly, a simple method of calibrating for fracture from a round or flat specimen tensile test is developed ans shown to be valid in a wide range of stress triaxiality. In the third part, experimental, numerical, and analytical studies on the deformation and fracture of thin plates subjected to localized static and impulsive loadings are conducted. A new method of constructing a Fracture Forming Limit Diagram (FFLD), which is understood as the locus of fracture strain in the principal strain space, is proposed and confirmed by the classical problem of punch indentation in thin plates. Moreover, it is demonstrated that the present fracture criterion captures the formation and propagation of cracks in thin plates. In the fourth part, extensive parametric studies on the transient responses and fracture of various core arrangements in sandwich structures under explosive loading are carried out. A new Blast Resistant Adaptive Sandwich (BRAS) structure is proposed, which substantially increases fracture resistance during static and dynamic loading events. / (cont.) In particular, the threshold impulse to initial fracture of the optimized BRAS is 1.8 times higher than the optimized conventional sandwich structure (USDH). Also the maximum reduction of the ruptured area with the optimized BRAS is 90%, as compared to the optimized USDH. / by Young-Woong Lee. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1996. / Includes bibliographical references (p. 93-95). / by Christopher Andrew Linder. / M.S.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 2005. / Includes bibliographical references (leaves 87-89). / This thesis describes the role of short sea shipping within the transportation network in the European Union. It examines the existence of externalities relating to congestion, infrastructure, air pollution, noise, and accidents in the transportation sector. It evaluates the level of these externalities and also their effects on the Community. It then explains current attempts to internalize these factors, or incorporate them into the cost of transportation that the user pays. It concludes that current efforts are lacking and do not produce the most beneficial situation for the citizens of Europe. Consequently, the thesis investigates other possible methods of internalization that may produce more advantageous results and analyzes their possible effects on the transportation sector. The value of short sea shipping is examined in regards to the previously mentioned externalities. It concludes that, with the exception of the emission of sulfur dioxide, maritime transportation outperforms other modes of transportation by producing relatively few external effects. / (cont.) The current status of the short sea shipping industry is then described, followed by a discussion of intermodal transportation and the initiative within the European Community to increase the use of intermodal transportation. Two case studies are then reviewed, which demonstrate the economy of intermodal transportation solutions compared to all-road alternatives. The thesis concludes by summarizing the benefits of short sea shipping. Some of the obstacles which prevent the realization of the full potential of short sea shipping are discussed. Suggestions for improving the current situation are included as well as a description of some of the measures adopted by the European Commission to increase the use of short sea shipping as an alternative to road transportation. / by Goksel Tenekecioglu. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 2001. / Includes bibliographical references (leaves 35-37). / by Sheri A. Cheng. / S.M.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1995. / Includes bibliographical references (leaves 113-114). / by Frédéric Buchoux. / M.S.