Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 62). / The author sought out the opportunity to design and implement a system for pumping oxygenated fluid and mixing it with saline, for the purpose of providing sufficient levels of oxygen for patients undergoing forms of asphyxia. The machine is able to pump oxygenated fluid by means of a low-density polyurethane bellows, which is powered by a stepper motor. A peristaltic pump simultaneously pumps saline fluid in another branch of the system. The two branches come together, the fluids are mixed, and bubbles are removed before the fluid is ready to be injected into a patient. Solid modeling as well as machine tools were used to create the physical structure, while LabView was used as the program regulating the controls of the device. The pump operates and can successfully mix both fluids. Flow rate can be controlled via the LabView program, and variables such as force, displacement, and flow rate can be read as outputs. The modular design of the pump allows it to be easily upgraded or altered. Because of all these features, the pump is an excellent research tool for developing a method of mixing and injecting viscous oxygenated fluid. / by Alexander M. Mason IV. / S.B.

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 109-113). / We review and present techniques for effecting and controlling the reorientation of structures "floating" in angular-momentum-conserving environments, applicable to both space robotics and small satellite attitude control. Conventional orientation control methods require either the usage of continuously rotating structures (e.g. momentum wheels) or the jettisoning of system mass (e.g. hydrazine thrusters). However, the systems proposed herein require neither rotating structures nor mass ejection; instead, orientation is controlled by the imposition of a bounded cyclic shape change-the canonical example of such a system is a cat righting herself while falling, thereby always landing on her feet-coupled with the conservation of angular momentum, which acts analogously to a nonholonomic constraint on the system dynamics. Further, by considering the reduced system dynamics, we extend the concept to consider the class of structures where the requisite cyclic shape change is attainable via dynamical effects, such as the normal modes of structural vibration for structures with finite stiffness. This is the central novel result of this thesis and has implications for the design of space structures where the attitude control hardware is integrated directly into the preexisting structure, the development of orientation control techniques for soft robots in space and underwater, and the design of MEMS attitude control actuators for very tiny satellites. We apply mathematical tools drawn from differential geometry and geometric mechanics, which can be intimidating but which provide a comprehensive and powerful framework for understanding a wide range of locomotion problems fundamental to robotics and control theory. These tools allow us to make succinct statements regarding gait design, controllability, and optimality that would be otherwise inaccessible. / by Nathan S. Tyrell. / S.M.

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1993. / Includes bibliographical references (leaf 30). / by Robert D. Rockwell, Jr. / B.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / "February 2006." / Includes bibliographical references (p. 145-153). / Future robotics and mechatronics applications will require systems that are simple, robust, lightweight and inexpensive. A suggested solution for future systems is binary actuation. Binary actuation is the mechanical analogy to digital electronics, where actuators "flip" between two discrete states. Systems can be simple since low-level feedback control, sensors, wiring and electronics are virtually eliminated. However, conventional actuators, such as DC motors and gearbox are not appropriate for binary robotics because they are complex, heavy, and expensive. This thesis proposes a new actuation technology for binary robotics and mechatronics based on dielectric elastomer (DE) technology. DE actuators are a novel class of polymer actuators that have shown promising low-cost performance. These actuators were not well understood and, as a result, faced major reliability problems. Fundamental studies conducted in this thesis reveal that reliable, high performance DE actuation based on highly viscoelastic polymers can be obtained at high deformation rates, when used under fast, intermittent motion. / (cont.) Also, analytical models revealed that viscoelasticity and current leakage through the film govern performance. These results are verified by an in-depth experimental characterizion of DE actuation. A new DE actuator concept using multi-layered diamond-shaped films is proposed. Essential design tools such as reliability/performance trade-offs maps, scaling laws, and design optimization metrics are proposed. A unit binary module is created by combining DE actuators with bistable structures to provide intermittent motion in applications requiring long-duration stateholding. An application example of binary robots for medical interventions inside Magnetic Resonance Imaging (MRI) systems illustrates the technology's potential. / by Jean-Sébastien Plante. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2002. / Includes bibliographical references (leaves 118-122). / A crystal-mechanics-based constitutive model for polycrystalline shape-memory materials has been developed. The model has been implemented in a finite-element program. Finite-element calculations of polycrystal response were performed using two methods: (1) The full-finite element method where each element represents a single crystal chosen from a set of crystal orientations which approximate the initial crystallographic texture; (2) A simplified model using the Taylor assumption (1938) where each element represents a collection of single crystals at a material point. The macroscopic stress-strain responses are calculated as volume averages over the entire aggregate. A variety of superelastic experiments were performed on initially-textured Ti-Ni rods and sheets. The predicted stress-strain curves from finite-element calculations are shown to be in good accord with the corresponding experiments. For the Ti-Ni sheet, strain-temperature response at a fixed stress was also experimentally studied. The model was also shown to accurately predict the results from these important experiments. Further, by performing superelastic experiments at moderately high strain rates, the effects of self-heating and cooling due to the phase transformations are shown to be captured well by the constitutive model. The thermo-mechanically-coupled theory is also able to capture the resulting inhomogeneous deformations associated with the nucleation and propagation of transformation fronts. Finally, an isotropic constitutive model has also been developed and implemented in a finite-element program. This simple model provides a reasonably accurate and computationally-inexpensive tool for purposes of engineering design. / Prakash Thamburaja. / Ph.D.

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 112-117). / Wind field analysis is one of the most important components for designers to achieve a thermally-comfortable and energy-efficient building design. Designers need a fast and relatively accurate wind field model to get integrated into the design workflow, but current platforms to work on are either costly and time-consuming conventional Computational Fluid Dynamics (CFD) tools or over-simplified data correlation factors, which makes the workflow undesirable for designers' use. In this thesis, a novel Lattice-Boltzmann Wind Field Model (LBWFM) is developed and integrated in a designer-relevant Rhino-based environment. Lattice-Boltzmann Method (LBM) is introduced as the solver due to its open-source and parallelism natures, and coded in C# language for three-dimensional urban airflows. Results of the model are validated with experimental measurements as well as conventional CFD tools for both wind velocity and pressure fields. To further enhance the computational efficiency, proper settings of inlet wind profile and optimal modeling domain size are investigated for the LBWFM. And the relative wind pressure coefficient calculated out of the model is then applied in the analysis of wind-driven natural ventilation potential with the indicator of air exchange flow rate. Finally the limitation of the model is stated and future work is discussed on the modifications of buoyancy effect and potential extension is addressed in the application of LBWFM. / by Tianyi Chen. / S.M.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1996. / Includes bibliographical references (p. 47). / by Josh Schifter. / M.S.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006. / Includes bibliographical references (p. 46). / The MIT community and the City of Cambridge embarked on initiatives to reduce energy consumption and Greenhouse Gas emissions in accordance with the Kyoto Protocol which calls for a 20 % reduction in 1990 levels of GHG emissions by 2010. This thesis seeks to expand our understanding of how the MIT campus consumes energy and with that knowledge recommend methods of reducing energy consumption by eliminating irresponsible energy use. Based on the GHG emission map created by Tiffany Groode in her 2004 thesis A Methodology for Assessing MIT's Energy Use and Greenhouse Gas Emissions, the second largest energy consuming building per square foot, Building 18, was selected and analyzed in detail. This thesis proves the high hood density, lack of an exhaust heat recovery system, and irresponsible fume hood use necessitate Building 18's wasteful consumption of energy. Research revealed that, on average, 67 hoods were left open at night, and 88 were open during daytime use. Of those open hoods, only 5 were in use during the night, and 48 were in use during the day. If the unused hoods were closed the consumption of electricity, steam, and chilled water could be decreased by approximately 17% and save the Institute $350,000 a year in utility costs. / by Steven Thomas Amanti. / S.B.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 77-86). / Silk is a hierarchically structured protein fiber with exceptional tensile strength and extensibility, making it one of the toughest and most versatile biocompatible materials. While experimental studies have shown that the molecular structure of silk has a direct influence on the stiffness, toughness, and failure strength of silk, few molecular-level analyses of the nanostructure of silk assemblies, in particular under variations of genetic sequences, have been published. Here, atomistic-level structures of wildtype as well as modified MaSp1 protein from the N. clavipes spider dragline silk sequences are reported, obtained using an in silico approach based on replica exchange molecular dynamics (REMD) and explicit water molecular dynamics. In particular, the atomistic simulations discussed in this parametric study explore the effects of the poly-alanine length of the N. clavipes MaSpi peptide sequence, solvent conditions, and nanomechanical loading conditions on secondary and tertiary structure predictions as well as the nanomechanical behavior of a unit cell of 15 strands with 900-1000 total residues used to represent a cross-linking 7-sheet crystal node in the network within a fibril of the dragline silk thread. Understanding the behavior of this node at the molecular scale is critical for potentially bypassing strength limits at this length scale and vastly improving silk for medical and textile purposes as well as synthetic elastomers and polymer or aramid fiber composites with a similar molecular structure and noncovalent bonding for aerospace, armor, and medical applications. The main hypothesis tested is that there exists a critical minimum length of the poly-alanine repeat that ensures the formation of a robust cross-linking the [beta]-sheet crystal. Confirming earlier experimental and computational work, a structural analysis reveals that poly-alanine regions in silk predominantly form distinct and orderly [beta]-sheet crystal domains while disorderly regions are formed by glycine-rich repeats that consist of 310-helix type structures and 7-turns. These predictions are directly validated against experimental data based on dihedral angle pair calculations presented in Ramachandran plots combined with an analysis of the secondary structure content. The key results of this study are: e A strong dependence of the resulting silk nanostructure on the poly-alanine length. The wildtype poly-alanine repeat length of six residues defines a critical minimum length that consistently results in clearly defined [beta]-sheet nanocrystals allowing for misalignment. For poly-alanine lengths below six residues, the /-sheet nanocrystals are not well-defined or not visible at all, while for poly-alanine lengths above six the characteristic nanocomposite structure of silk emerges with no significant improvement of the quality of the sheet nanocrystal geometry. A simple biophysical model is presented that explains the minimum length scale based on the mechanistic insight gained from the molecular simulations. The efficient stacking of the [beta]-sheets of a well-defined crystal reinforces local hydrophobicity and prevents water diffusion into a crystal above a critical size. Nanomechanical testing reveals that the combination of the 12-alanine length case and central pull-out loading conditions results in delayed failure by employing a hierarchy of strong [beta]-sheets and soft, extensible semi-amorpous regions to overcome a predicted H-bond saturation. This work constitutes the most comprehensive study to-date of the molecular structure prediction and nanomechanical behavior of dragline silk. Building upon previous computational studies that used similar methods for structure prediction and mechanical analysis, e.g. REMD and force-control loading, this work presents: the first results of the near-native structures determined by REMD after equilibration in TIP3P explicit solvent, the first parametric study of the effects of modifying the wildtype poly-alanine segment length to values outside the range naturally observed for MaSp1 on structure prediction and nanomechanical behavior, and, the first comparison between previously published loading conditions, i.e. the Stretch test, and the novel Pull-out loading conditions that are hypothesized to be more appropriate for modeling of the in situ loading of the cross-linking [beta]-sheet crystal. Further parametric studies in peptide sequence to optimize bulk fiber properties must involve changes in simulated nanomechanical loading conditions to properly assess the effects of the changes in peptide sequence. These findings set the stage for understanding how variations in the spidroin sequence can be used to engineer the structure and thereby functional properties of this biological superfiber, and present a design strategy for the genetic optimization of spidroins for enhanced mechanical properties. The approach used here may also find application in the design of other self-assembled molecular structures and fibers and in particular biologically inspired or completely synthetic systems. / by Graham Hayden Bratzel. / S.M.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1991. / Includes bibliographical references (leaves 205-210). / by Julie Chen. / Ph.D.