Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1988. / Title as it appeared in MIT Graduate list, June, 1988: Development of a new wall shear stress gauge for fluid flow. / Includes bibliographical references. / by Yuksel Gur. / M.S.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1985. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING / Bibliography: leaves 87-88. / by Magin F. Briceño B. / M.S.

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 70-71). / Reducing energy consumption without compromising the quality of products and the comfort of occupants is important in maintaining the competence of a pharmaceutical company. An energy management tool is developed to monitor the energy efficiency and calculate the cooling load. After analyzing the Energy Utilization Index (EUI) and cooling load, the Heating, Ventilation and Air-Conditioning (HVAC) system is identified as the major energy consumer in the plant. The AHU operation schedule in the office building is modified to reduce waste while accommodating the working schedule of employees. Motion detection lighting control is implemented in office areas to reduce waste from unnecessary lighting. Revision of the AHU operating schedule in manufacturing building can reduce electricity use by 16.5% while the implementation of other recommendations can save more than $50,000 in a six month period. A spreadsheet is developed to optimize the dehumidifier setting and the set point temperature of chilled water and off coil air. / by Haoyu Liu. / M.Eng.

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 83-88). / Rapid Prototyping has transitioned from only being able to produce delicate prototypes to being capable of producing robust production parts. As part of this transition, it has been renamed Additive Manufacturing (AM). As a true manufacturing technology, it has become important to deliberately design parts for Additive Manufacturing, and research has begun in how best to achieve this. This thesis explores the background of Additive Manufacturing, the growth in its use as a manufacturing technology, and the advantages and challenges of the technology. Following background information, this thesis progresses to different design approaches and technologies that promise to be effective when paired with AM. A design methodology using topology optimization is proposed, detailed and then tested on two case studies. The first case is a high-speed mirror for imaging and the second case is an aircraft bracket for the 2013 GrabCAD-GE design challenge. This thesis also includes an examination of the implementation of the proposed methodology on these case studies and the resulting designs. The design from both case studies achieved a greater than 60% weight reduction through the use of design methodology tailored for AM. The final section of the thesis shifts from the design process to the development process where the impact of AM is examined. In order to gain an understanding of the influence that Additive Manufacturing has on production, this thesis includes a synthesis of the literature from Additive Manufacturing as well as Design and Management. The benefits are approached from an economic perspective, reviewing the first order benefits that have been extensively studied and then progressing to the second order benefits, and indirect benefits, which have not been examined in detail before. To understand the full effect of Additive Manufacturing on product development, the consideration of advantages such as high fidelity prototypes, decreased risk, faster time to market and late stage design flexibility are assessed. / by Michael L. Stern. / S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2002. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Includes bibliographical references. / thermal softening behavior at temperatures above 900 K. This thermal softening behavior limits the turbine inlet temperature, which in turn significantly degrades the overall engine efficiency. Previous studies have shown that hybrid structures of silicon and silicon carbide have good potential for improved engine performance. Detailed design of Si/SiC hybrid structures for high temperature micro-turbomachinery, however, has been hampered by the relatively poor performance of single crystal Si at elevated temperatures and high stresses and by the unavailability of accurate material properties data for both Si and SiC at the temperatures of interest. From previous work, the critical structures and materials issues to be resolved, in order to proceed with the design of high temperature Si/SiC hybrid structures, were identified as follows: 1. the safety margin of the Si/SiC hybrid structures based on the upper yield strength of Si 2. reliable estimation of the service life of the Si/SiC hybrid structures 3. structural instabilities caused by the combination of stress concentrations and strain softening. In the course of this thesis, these issues provided the key motivations of the work, and have been substantially resolved. As a first step, it is critical to obtain a better understanding of the mechanical behavior of this material at elevated temperatures in order to properly exploit its capabilities as a structural material. Creep tests in simple compression with n-type single crystal silicon, with low initial dislocation density, were conducted over a temperature range of 900 K to 1200 K and a stress range of 10 MPa to 120 MPa. The compression specimens were machined such that the multi-slip <100> or <111> orientations were coincident with the compression axis. / (cont.) The creep tests reveal that the response can be delineated into two broad regimes: (a) in the first regime rapid dislocation multiplication is responsible for accelerating creep rates, and (b) in the second regime an increasing resistance to dislocation motion is responsible for the decelerating creep rates, as is typically observed for creep in metals. An isotropic elasto-viscoplastic constitutive model that accounts for these two mechanisms has been developed in support of the design of the high temperature turbine structure of the MIT microengine. From the experimental observations and model validation, basic guidelines for the design of Si/SiC hot structures have been provided. First, the use of the upper yield strength of single crystal Si for design purpose is non-conservative. Also from the perspective of the design of Si hot structures, the lower yield strength is insufficient, particularly for micro-turbomachinery operating at elevated temperatures and high stresses. The recommended approach to the design of Si hot structures is to use the Si model for extracting appropriate operating conditions, and to reinforce the Si structures with SiC in strategic locations. Second, at high temperatures, the effect of stress concentrations is not crucial ... / by Hyung-Soo Moon. / Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006. / Includes bibliographical references (p. 117-120). / The piston ring-pack contributes approximately 25% of the mechanical losses in an internal combustion engine. Both lubricant viscosity and surface texturing were investigated in an effort to reduce this ring-pack friction and increase engine efficiency. While both optimizing viscosity and surface texturing are predicted to cause a reduction in ring/liner friction individually, a combined approach may cause an even greater friction reduction while mitigating unwanted side-effects such as oil consumption and wear. Existing MIT models, with some modifications and supplementary programs to allow investigation of the parameters of interest, were used to conduct this research. A ring-pack model based on average flow-factor Reynolds analysis was used for both studies, with a modified form of this program, along with a supplementary deterministic model for surface analysis, used for the study of surface texturing. Although these advanced models are applicable in a wide range of cases, the surface textures studied in this research are very different than a typical cylinder liner surface, and can be represented only approximately by the averaged Reynolds analysis upon which the ring simulation is based. / (cont.) For this reason, the analysis of surface features has focused on a parametric study, whose goal is to analyze trends relating ring/liner friction to surface parameters, and to make a general evaluation of the potential of surface texturing to reduce ring-pack losses. Study of lubricant viscosity effects throughout the engine cycle indicated that conditions in the mid-stroke region have the main influence (compared to the end-strokes) on friction power losses, and that reducing viscosity here could lead to a reduction in ring-pack FMEP of -7%. Changes in cylinder liner surface texturing, also, can lead to significant friction reductions. Patterns of both grooves and round dimples were shown to reduce ring/liner friction by increasing hydrodynamic pressure in the lubricant, thus increasing oil film thickness and reducing both asperity contact and hydrodynamic friction. Also, because the effect of reducing viscosity is to decrease oil film thickness, and that of the surface texturing considered is to increase it, these two parameters can be optimized together, and balanced so that oil film thickness remains constant. Then, negative side-effects such as wear (due to decrease in film thickness) and oil consumption (resulting from an increase in film thickness) can be negated, even as friction is reduced even further than is possible using viscosity or surface effects alone. / by Rosalind Takata. / S.M.

Massachusetts Institute of Technology. Dept. of Mechanical Engineering. Thesis. 1974. Ph.D. / MICROFICHE COPY ALSO AVAILABLE IN BARKER ENGINEERING LIBRARY. / Table l. 237 folded. Vita. / Includes bibliographical references. / Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007. / Includes bibliographical references (p. 156-157). / Fundamental to the design of an Ackerman steered autonomous ground vehicle is the development of a low-level controller that effectively performs trajectory or path tracking. Though ample literature is available on various methods for controlling ground vehicles, little information is presented on the implementation and tuning of such controllers. Moreover, few sources extend ground vehicle control to driving in reverse. This work presents a novel approach to the implementation of the traditional "pure pursuit" style controller in which a dynamic vehicle model is used to map from the path curvature specified by the pure pursuit algorithm to the vehicle's actual steering angle. Additionally, an analytical methodology using a linear model of straight-line path following is used to tune the pure pursuit look-ahead distance. This pure pursuit controller is then contrasted with a simulation-based controller that uses a kinematic model to predict the vehicle's response to a series of different steering inputs; a performance metric is used to select the best command given these predictions. Successful trajectory control results are presented at speeds up to 22 mph. The second focus of this work is the control of a front-wheel steered vehicle driving in reverse. Novel to this work is the presentation of pure pursuit as a stable solution to this problem. Pure pursuit is then contrasted with the mechanism-based controller that was developed by Patwardhan et al. at the University of California Berkeley. In presenting this controller, a new method employing a linear kinematic vehicle model is used to tune the controller parameters. It is then shown that, under specific conditions, the mechanism-based controller and the pure pursuit controller are identical. Both controllers are then compared with the simulation-based controller adapted for driving in reverse. / (cont.) Results are presented at speeds up to 6.7 mph. Results for the implementation of these controllers were collected using a 2006 Land Rover LR3 developed for MIT's entry into the 2007 DARPA Urban Challenge. Results ultimately illustrate the respective strengths and weaknesses of the pure pursuit class of controllers. / by Stefan F. Campbell. / S.M.

Thesis (Nav. E. and S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, June 2009. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Includes bibliographical references (p. 42-43). / Propellers are typically optimized to provide the maximum thrust for the minimum torque at a specific number of revolutions per minute (RPM) at a particular ship speed. This process allows ships to efficiently travel at their design speed. However, it is useful to know how the propeller performs during off-design conditions. This is especially true for naval warships whose missions require them to perform at a wide range of speeds. Currently the Open-source Propeller Design and Analysis Program can design and analyze a propeller only at a given operating condition (i.e. a given propeller RPM and thrust). If these values are varied, the program will design a new optimal propeller for the given inputs. The purpose of this thesis is to take a propeller that is designed for a given case and analyze how it will behave in off-design conditions. Propeller performance is analyzed using non-dimensional curves that depict thrust, torque, and efficiency as functions of the propeller speed of advance. The first step in producing the open water diagram is to use lifting line theory to characterize the propeller blades. The bound circulation on the lifting line is a function of the blade geometry along with the blade velocity (both rotational and axial). Lerbs provided a method to evaluate the circulation for a given set of these conditions. This thesis implements Lerbs method using MATLAB® code to allow for fast and accurate modeling of circulation distributions and induced velocities for a wide range of operating conditions. These values are then used to calculate the forces and efficiency of the propeller. The program shows good agreement with experimental data. / by Kevin M. Flood. / Nav.E.and S.M.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1999. / Includes bibliographical references (p. 311-327). / by Joseph A. Doeringer. / Ph.D.