Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004. / Includes bibliographical references (leaves 30-31). / Electrical Discharge Machining (EDM) is a non-traditional process that uses no mechanical forces to machine metals. It is extremely useful in machining hard materials. With the advantages EDM has to offer and its presence as a common and useable technique, along with the other machining processes available to the industrial world, there is an added strain on the environment. The scope of this thesis includes analyzing the various inputs into EDM and the resulting outputs into the environment. A simplified model is used to analyze the process. The main categories of flow scrutinized in the model are material flow and energy flow. The most hazardous effect to the environment is found in the resin interaction of the wire EDM process where depending on the type of material machined, there is a potential presence of hazardous materials. There are efforts to recycle all salvageable materials such as wire and metal wastes, but currently no accountability system exists as manufacturers are responsible for their actions. / by Margaret H. Cho. / S.B.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005. / Includes bibliographical references (leaf 72). / This research involves the design, manufacture, and testing of a small, < lm³, < 1Okg, low cost, unmanned submersible. High maneuverability in the ROV as achieved through a high thrust-to- mass ratio in all directions. One identified solution is moving the primary thrusters in both the pitch and yaw directions. The robot is propelled by a pair of 2 DOF thrusters, and is directly controlled in heave, surge, sway, yaw, and roll. Pitch is controlled through passive buoyancy and, potentially, active manipulation of added mass and gyroscopic effects. This system is compared against a traditional fixed-thruster system in terms of cost, size, weight, and high/low speed performance. Preliminary results indicate that the actuated system can provide an improved thrust-to-mass metric at the expense of increased system complexity. This margin of improvement increases with increasing thruster size. The system has applications in high accuracy positioning areas such as ship hull inspection, recovery, and exploration. / by Daniel G. Walker. / S.B.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005. / Includes bibliographical references (p. 335-343). / Each year, about 700,000 people in the United States have a stroke, making it a leading cause of serious, long-term disability. Modalities of therapy often assume the processes underlying motor recovery and motor learning are similar because both exhibit activity- dependent neural plasticity. However, the impact of other factors unique to recovery such as re-acquisition of muscle strength and resolution of abnormal muscle tone confounds the validity of this assumption. By implementing an adaptive impedance controller that collapses from a "virtual slot" between two targets to a "virtual spring" at the desired target, a new performance-based progressive therapy (PBPT) algorithm was developed to test whether recovery would be enhanced by incorporating learning strategies like repetition, goal specification, and positive reinforcement. A study of chronic stroke patients (8 to 95 months post-stroke) who were in a clinically verified "stable" phase of recovery was conducted with the PBPT protocol, in which patients made over 12,000 visually guided, point-to-point movements. / (cont.) Though prior clinical results suggested that recovery would plateau 6 months post-stroke, two studies using sensorimotor (SM) and progressive resistance (PR) therapy protocols achieved significant, though modest, reductions in impairment. The new PBPT protocol produced significantly larger impairment reductions with over 6,000 fewer movements than SM and PR. By design, the adapting PBPT parameters, namely, the time allotted to move between targets and the virtual slot sidewall stiffness, serve as indicators of patients' abilities to move and aim (as parameters decrease (increase), patients move faster (slower) and require less (more) aiming assistance). By analyzing the parameters' evolution throughout the PBPT protocol, it was shown that motor recovery follows an exponential progression similar to a motor learning "law of practice". In addition, a serendipitous benefit of the PBPT protocol occurred - a sustained reduction in abnormal muscle tone, a factor unrelated to learning. A spectral impedance estimation method suitable for a clinical setting was developed and validated by identifying known mechanical systems. In addition, preliminary data was collected on unimpaired subjects and stroke patients. / by Jerome J. Palazzolo. / Ph.D.

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1995. / Includes bibliographical references (p. 127-129). / by Rahul Dighe. / Sc.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007. / Includes bibliographical references (p. 263-282). / There are many practical reasons for studying the deformational behavior or rheological properties of a dough system. The mass production of bread has led to a need of machines that are able to handle and process large volumes of dough. An understanding of the deformational properties can aid in designing machines of this kind. Less obviously, the texture of the bread we eat is governed by the mechanical properties of the dough from which it is proofed and baked from. During the bread making process, large non-linear deformations feature prominently. In mixing and kneading, dough is stretched and sheared by hand or by specially designed mixing devices, while in proofing and baking, the expansion of gas cells causes significant extensional strain on the surrounding dough. Other than directly affecting the moduli of the fibers and membranes in the solid phase of bread, a link between the rheology of dough and the baked loaf volume has also been established. In this thesis, we first develop consistent and accurate techniques for measuring the rheological properties of the dough. Good experimental techniques and protocols are essential for studying the mechanical properties of such a sticky, visco-elasto-plastic, time-dependent material. We modify some of the standard rheometric hardware and protocols to accommodate this unusual material. Special attention is given to nonlinear deformations such as uniaxial extensional flows and large amplitude oscillatory shear flows (LAOS). We use the new techniques to probe the microstructure of dough and its constituents from a mechanical viewpoint. The strongly nonlinear rheological properties of dough arise from the interactions of a protein matrix and a high filler concentration consisting of hydrated starch particles. / (cont.) We demonstrate that the gluten protein that imbues the dough with its characteristic viscoelasticity should be considered as a transient network that is interconnected by finitely extensible biopolymer segments (-20nm mesh size) and held together by hydrogen bonds and/or hydrophilic interactions. Using this renewed understanding of the microstructure, we construct appropriately frame-invariant constitutive equations (generalized gel equation and a multi-mode FENE network model) that describe the rheology of gluten gels with a minimal number of parameters. The behavior of gluten gels can then be related to prototypical flour-water doughs by the effects of the starch filler using the concept of strain amplification. Finally, this general framework of microstructure and rheological properties of gluten gels and flour-water dough are applied to practical situations. We discuss the utility of this work in context to some specific case studies of rheological aging, the effects of water content and flour-type variations. / by Trevor Shen Kuan Ng. / Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 113-116). / The generation of 2D and 3D internal wave fields is extensively studied via planarand stereo- Particle Image Velocimetry (PIV) flow field measurement techniques. A benchmark was provided by an experiment involving tidal flow over a 2D Gaussian ridge; this study providing a counterpart with which studies of a 3D incised Gaussian ridge could be compared with. To further benchmark the 3D wave field studies an experiment involving the canonical setup of a vertically oscillating sphere was performed and the results compared with the latest theory; the excellent agreement obtained provided confidence in the stereo-PIV method for studying fully three-dimensional internal waves. The 3D incised Gaussian ridge generates a wave field characterized by noticeable, though weak, out-of-plane forcing that evolves from a relatively strong to a weakly localized quantity as the wave field transitions from super- to subcritical, while the in-plane velocity field appears nearly identical to its 2D counterpart. / by Sasan John Saidi. / S.M.

Thesis (S.B.)--Massachusetts Institute of Technology, Department of Mechanical Engineering, 2013. / Cataloged from PDF version of thesis. / Includes bibliographical references (page 34). / This thesis documents Katarina Popovic's contribution to the design of hydraulic cylinder actuation system for day to day solar trough sun tracking, a semester long project within 2.752 Development of Mechanical Products class. The primary goal of this project was to design a robust mechanical system while reducing the complexity and thus overall cost of the solar trough assembly for the production line. The mechanism suggested in this thesis actuates both sides of the solar trough simultaneously, as well as exploit hydraulic cylinder's full range stroke in order to deliver +/-110° rotational requirement. The rotational motion is achieved through a pulley and a wire rope system, actuated by a single, double action double rod cylinder. As this project funding was received from our sole sponsor, an Italian multinational energy company, during the design process the ultimate goal of eventual production line was kept in mind. However slight design modifications have been made in order to install and test the actuation system on the already existing 4m solar trough prototype on site in Pittsfield, New Hampshire. / by Katarina Popović. / S.B.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2003. / Includes bibliographical references (p. 61-63). / by Nicholas J. Conway. / S.M.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1999. / Includes bibliographical references (p. 45). / An experimental study was perfonned to determine which materials are best suited for internal aircraft noise reduction. An impedance tube with dimensions of a scaled aircraft was constructed and evaluated, and eleven materials were tested and compared based on their noise reduction properties, weight, and thickness. Polyvinylidene Fluoride was tested for use in active noise control for a large space. / by Djuna S. Copley-Woods. / S.B.

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 67-68). / The Atlantic razor clam (Ensis directus) burrows by contracting its valves, fluidizing the surrounding soil and reducing burrowing drag. Moving through a fluidized, rather than static, soil requires energy that scales linearly with depth, rather than depth squared. In addition to providing an advantage for the animal, localized fluidization may provide significant value to engineering applications such as vehicle anchoring and underwater pipe installation. This thesis presents the design of RoboClam 2, a self-actuated, radially expanding burrowing mechanism that utilizes E. directus burrowing methods. The device is sized to be a platform for an anchoring system for autonomous underwater vehicles. The scaling relationships necessary for the creation of this internally actuated burrowing robot are presented. These relationships allow for designing devices of different sizes for other applications, and describe optimal sizing and power needs for various size subsea burrowing systems. RoboClam 2 is a proof of concept iteration of a digging mechanism that utilizes localized fluidization. It will be used for testing digging parameters in a laboratory setting and validating the theory presented. / by Daniel S. Dorsch. / S.M.