Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017. / Cataloged from PDF version of thesis. / Includes bibliographical references. / Viable electrical energy storage is essential for the development of sustainable energy technologies, such as renewable power and electric vehicles. Electrochemical energy storage devices are promising candidates for these applications, and lithium-ion batteries are the leading available technology. However, the current cost and performance of these devices limit their widespread adoption. In this thesis, we develop materials and design guidelines for positive electrodes and solid-state electrolytes to address these challenges. The positive electrode is one of the main limitations to improving both the capacity and cost of lithium-ion batteries. Organic molecules represent a class of materials, which if selected correctly, can address these issues. The electrochemical properties of various polycyclic aromatic hydrocarbons (PAHs), which are organic molecules produced in significant quantities as industrial waste products, were investigated for use as positive electrodes. By introducing PAHs within a functionalized few-walled carbon nanotube (FWNT) matrix, we developed high-energy and high-power positive electrodes. The redox potential and capacity of various PAHs were correlated with their chemical and electronic structures, and their interaction with the functionalized FWNT matrix. Another challenge limiting the adoption of lithium-ion batteries is the flammability and instability of the organic liquid electrolyte, which increases the risk of dangerous battery failures and limits the use of higher energy-density electrodes. One promising solution is to replace the organic liquid electrolyte with a solid-state lithium-ion conductor. However, the ionic conductivity of solid-state electrolytes are typically several orders of magnitude lower than organic liquid electrolytes. Using lattice dynamics, we developed a framework to understand the migration of lithium through crystalline solid-state electrolytes. The understanding of the use of organic materials in positive electrodes and solid-state lithium-ion conductors as electrolytes provides insight for the design of next-generation electrochemical energy storage solutions. / by John Christopher Bachman. / Ph. D.

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 107-111). / In this thesis, I improved the design of a high-speed Atomic Force Microscope (AFM) for jumping mode operation. The relations between important imaging parameters and physical limitations of the system were established first to identify the aspects of improvement. Two control algorithms to improve the imaging speed and probe sample interaction force for jumping mode atomic force microscopy operation have been proposed and investigated both in simulation and experiment. A new generation of multi-actuated sample scanner has been designed to address the dynamic coupling, thermal expansion and range issues in the previous design. Improvements to the optical beam deflection system, photodiode circuit, signal conditioning circuit and cantilever probe holder with actuators have been implemented. The combined optimization and design work improved the capability of the original custom made high-speed AFM setup in both subsystem performance and jumping mode operation. / by Fangzhou Xia. / S.M.

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Cataloged from student-submitted PDF version of thesis. / Includes bibliographical references (pages 89-91). / This thesis details the hardware and control development for a low-cost modular actuator, intended for use in highly dynamic robots. A small 12 degree of freedom quadruped robot has built using these actuators, on which several control experiments have been performed. Despite the relatively low cost of the actuators, the quadruped has demonstrated unprecedented dynamic behaviors for a robot of this scale and number of degrees of freedom, such as a full 360° backflip from standing on flat ground. Several other implementations of these actuators are also discussed, a including bilateral teleoperation and haptic feedback system and a 6 degree of freedom lower-body biped robot. / by Benjamin G. Katz. / S.M.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006. / Includes bibliographical references (leaf 52). / Modeling manufacturing systems is a necessary tool in the process of finding a way to analyze and improve design. Increasingly complex systems are now being modeled, and two such systems are the focus of this report. The Tandem and Re-Entrant systems allow for multiple part types to be sent through a single line of processing machines. The parts have different priorities which determine the order in which they are produced. The Re-Entrant system is unique because it produces a single part that is processed through the same machine line multiple times. As the part travels through the processing line, it loops back to the beginning at the end of every run as a higher priority part. These simulations were tested for their validity by running with different input parameters to see how the system reacted. These programs can be used in the future with more complex systems and the knowledge gained from the results of these simulations can be applied to improving these systems and maximizing their efficiency. / by Christina C. Royce. / S.B.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005. / Includes bibliographical references (p. 185-188). / The split-Hopkinson pressure bar (SHPB) technique has been in use in one form or another for more than fifty years and has recently gained a great deal of attention for its ability to characterize materials such as metals, plastics, and even stiff foams at strain rates of up to 105 sec-1. Historically, however, numerous obstacles have stood in the way of applying this technique to softer biological tissues. This study is aimed at bridging this gap by employing various innovations in the field of split-Hopkinson pressure bar techniques (including hollow aluminum and solid polymeric pressure bars) to the characterization of trabecular bone. A preliminary study is conducted on a polyurea (PU) blend to assess the advantages and shortcomings of these approaches, as well as to validate the results obtained with each. Bovine trabecular bone with marrow in-situ, which was chosen for its ability to be tested with a wide spectrum of techniques, is then characterized with the selected techniques at rates of up to 1300 s-1 and strains of 0.07. The results are presented for each technique in the form of engineering stress vs. engineering strain curves. / (cont.) Average trend curves are also provided. Unfortunately, many of the samples were too damaged to allow for accurate measurement of apparent density. Consequently, a study into the effect of density on high strain rate responses is left as future work. Recommendations are made for increasing the strain imposed on the samples and suggestions for future studies on both trabecular bone and softer biological tissues are put forward. / by Timothy Paul Mahal Johnson. / S.M.

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1963. / MICROFICHE COPY AVAILABLE IN ENGINEERING. MIT copy bound with: Ball milling process / Yagiv Krzepicki. 1963. / Includes bibliographical references (leaf 32). / by Sandra Lensch Cunningham. / B.S.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 55). / The purpose of this research is to develop the best possible means and methods of building a six axis metrology system given cost and space constraints. Six axis measurements are a crucial part of precision engineering and characterizing machine performance, however commercially available sensors are not cost-efficient and are difficult to incorporate into meso-scale machines. The novel approach presented here uses three pairs of laser diodes and quadrant photodiodes to achieve six axis measurements. This paper presents a general parametric model that can predict the output of the photodiodes due to translations and rotations of the target for any geometry of the system. The device has performance characteristics of translational resolution in the range of microns depending on the geometry of the system, a bandwidth of 17.5 MHz, and dominant noise in the sensor of ±1.6 nm. This device will be useful in a variety of applications including nanomanufacturing, bio instrumentation, Dip Pen Nanolithography, AFM, and many more. / by Ryan N. King. / S.B.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 71). / A recently proposed method [Apelfeld, Y., Depth Discrimination of an Acoustic Source Based on Modal Energy Distribution. MIT, 2007] for rough, but fast and robust depth classification of acoustic sources was investigated in realistic towing scenarios. The method uses modal energy distribution as a categorical indicator for the source depth. In this study we analyzed the method performance in two major towing patterns: the "yo-yo" pattern and the "one-time" depth sampling pattern. The position of the array elements was obtained using the MOOS-IvP simulation package. Among the main towing parameters of the performance evaluation was the pitch angle of the array. The main finding of this study is the discovery of a relationship between vertical orientation of the array and the relative source bearing. Thus, downward array orientation leads to relatively high separation capability for sources located at 00 relative bearing. In the contrary, upward array orientation leads to high separation capability for sources located at the opposite horizontal relative bearing (1800). This relationship implies direct tactical considerations on the AUV deployment that are discussed and summarized in this study. / by Jakov Kostjukovsky. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 55-57). / The objective of this research is to enable large part or high volume manufacturing processes to make consumer or industrial products from a cork reinforced polymer composite, similar to current applications of glass reinforced polyester. The low initial investment and high flexibility of the spray lay-up process make it an attractive candidate to study. A spray lay-up apparatus was successfully constructed and employed in manufacturing parts from a hybrid material composed of granulated cork, chopped glass strand, and a polyester matrix. The material was tested for tensile and flexural properties following relevant ASTM standards. The material was found to have a tensile strength of 4.4 MPa and tensile modulus of 850 MPa. The flexural strength and modulus were 9 MPa and 830 MPa, respectively. Adding a fiberglass skin to the cork hybrid significantly improved its flexural strength. Additionally, a small turbine blade prototype was created as a proof of concept. It is recommended that further work focus on optimizing the hybrid material's properties, re-designing and optimizing the apparatus used for the spray-up process, and demonstrating material viability by manufacturing a cross section of a large turbine blade. / by Benjamin J. Pope. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 99-107). / Knowledge of phonon mean free path (MFP) distribution is critically important to engineering size effects. Phenomenological models of phonon relaxation times can give us some sense about the mean free path distribution, but they are not accurate. Further improvement of thermoelectric performance requires the phonon MFP to be known. In this thesis, we improve recently developed thermal conductivity spectroscopy technique to experimentally measure MFPs using ultrafast transient thermoreflectance method. By optically heating lithographically patterned metallic nanodot arrays, we are able to probe heat transfer at length scales down to 100 nm, far below the diffraction limit for visible light. We demonstrate the new implementation by measuring MFPs in sapphire at room temperature. A multidimensional transport model based on the grey phonon Boltzmann equation is developed and solved to study the quasi-ballistic transport occurring in the spectroscopy experiments. To account for the nonlinear dispersion relation, we present a variance reduced Monte Carlo scheme to solve the full Boltzmann transport equation and compare the simulation results with experimental data on silicon. / by Lingping Zeng. / S.M.