Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015. / Cataloged from PDF version of thesis. / Includes bibliographical references (page 36). / In order to create an injection-molded battery clip for the Chibitronics Circuit Sticker kit, both manufacturing and product design principles were considered to inform product feel and form as well as ensure manufacturability in future iterations of the clip. Prototypes were initially designed using modeling clay. These prototypes were then developed in Solidworks and printed on a MakerBot 3D printer. Three iterations of prototypes were tested and design decisions were made based on user need and aesthetic appeal of the battery clips. These prototypes were used to determine a final design decisions and the creation of a mold that will be used in future manufacturing of these battery clips. / by Paelle M. Powell. / S.B.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1998. / Includes bibliographical references (leaves 48-50). / by Qiutao Wang. / S.M.

Thesis: M. Eng. in Manufacturing, Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 153-156). / This thesis deals with the introduction of Highly Accelerated Life Testing (HALT) in a multinational corporation as part of a reliability improvement process for printed circuit boards (PCBs). More specifically, the thesis focuses on drafting a standard operating procedure (SOP) to standardize the fixture setup process so as to minimize variation in vibrational responses attributed to fixture setup. This study proposes a three phase approach to meet the objective. The first phase aims to minimize variation in the gauges and the vibration table. A gauge repeatability and reproducibility (gauge R&R) test is conducted on two triaxial accelerometers to determine the most suitable gauge for HALT. Next, a spatial uniformity test is conducted on the vibration table using design of experiments (DOE) method to determine the region with the most consistent vibration levels for testing. The second phase aims to reduce variation in fixture usage by introducing a generic fixture design base on fixture design principles. The last phase involves proposing a short-run statistical process control (SPC) method to detect setup variability. The results from the gauge R&R test show that mechanically mounted accelerometers have the least gauge variance. Using an SOP, switching from wax-mounting to threaded stud-mounting reduces gauge variance by approximately 90%. However, wax-mounted accelerometers are still relevant for measuring vibrational responses from PCBs due to its non-invasive properties. The drawback will be that the gauge becomes a key contributor to measurement variation. The spatial uniformity test reveals that the center of the vibration table has the least variation and is selected for the fixture setup. Further limitations on the HALT chamber are highlighted. Evaluation on the proposed generic fixture demonstrates that the fixture has met the key design criteria and manage to induce consistent failures to the PCBs. Limitations on the fixture design are also considered. The proposed SPC method is able to detect at least 88% of the assignable sources of variation in a simulation test. Finally, a custom SOP for the fixture setup is drafted for the company. / by Dexter Chew Xuan Han. / M. Eng. in Manufacturing

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005. / Includes bibliographical references. / A method is needed to make a critical splice for a downhole tool in the petroleum industry. The goal is to connect two wires, cover the connection with a protective coating, and then assess the integrity of the finished splice. This project investigates how ultrasonic welding and injection molding can be employed in making the splice. After equipment and a process are designed, splices are produced and testing proceeds. Then an overall assessment of the method is made: connecting the wires in manufacturing should be done by ultrasonic welding and coating the wires using injection molding is a viable option. Further testing should investigate the reliability and failure modes of the coating at high pressures and temperatures along with how the coating method can be improved for quality assurance. Using the system designed during this project and the information gleaned, the plastic injection method should be compared with different methods, such as shrink-tubing, in order to make a final decision on the best coating method to be optimized for employment in manufacturing. / by Lauren A. Killian. / S.M.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1994. / by Adeeb William Mohammed Shana'a. / M.S.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007. / 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. 71-73). / Two physical models of diffusion in absorbing porous media are proposed on two length scales. One models diffusion in the pore space of a random medium with absorbing interfaces while the other is a reaction diffusion model where particles are absorbed in the bulk. Typical particle traveling distances and a bulk absorption coefficient are described in terms of general geometrical characteristics of a random medium and the analytical relations are found to compare well with numerical experiments. For the case of geometries consisting of randomly placed cubes, absorption in the bulk scales with the solid fraction to the two-thirds power. The statistical distribution of reaction rates in these models is found to be inversely related to the reaction rate. A quasi-static Monte-Carlo model is also investigated. The more complex problem of microbial extracellular enzyme distributions in marine sediment was an inspiration for this work. / by David C. Forney, III. / S.M.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2001. / Includes bibliographical references (p. 44-45). / The production of composite materials continues to be an expensive process. The WEB-Based Cost Estimation Model enables one to approximate the cost of manufacturing composites, so as to assist the user in making sound economic decisions. An extensive, up-to-date materials database is an essential part of such a cost estimator. This paper presents a list of materials to be added to the existing database and also derives a materials selection chart for six manufacturing processes. / by John R. Boyer. / S.B.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005. / Includes bibliographical references (p. 108-114). / Many biological, natural and synthetic materials possess a networked or micro-truss-like microstructure. In this thesis work, a general microstructurally-informed continuum level constitutive model of the large stretch behavior of membranes possessing a triangulated network or truss-like structure is developed. As a specific example, a constitutive model of the stress-strain behavior of the red blood cell membrane is developed. The mechanical behavior of the membrane of the red blood cell is governed by two primary microstructural features: the lipid bilayer and the underlying spectrin network. The lipid bilayer is analogous to a 2D fluid in that it resists changes to its planar area, yet poses little resistance to planar shear. A skeletal network of spectrin molecules is crosslinked to the lipid bilayer and provides the shear stiffness of the membrane. The planar triangulated structure of the spectrin network is used to identify a representative volume element (RVE) for the model. A strain energy density function in terms of an arbitrary planar deformation field is proposed using the RVE. Differentiation of the strain energy density function provides expressions for the general multiaxial stress-stretch behavior of the material. / (cont.) The stress-strain behavior of the membrane when subjected to uniaxial and simple shear loading conditions in different directions is given, showing the capabilities of the proposed microstructurally-detailed constitutive modeling approach in capturing the evolving anisotropic nature of the mechanical behavior. The proposed constitutive model also provides a framework to explore the contributions of mechanically-induced unfolding. The force-extension behavior of a single modular macromolecule exhibits a "saw-tooth" pattern due to unfolding giving a sequence of force rise to a peak followed by a load drop. Using the introduced continuum approach together with single molecule force-extension behavior and a transition state model of unfolding, large deformation behavior of two-dimensional networks of biomacromolecules is studied for various loading conditions. The effect of the strain-rate on the mechanical response is investigated. / by Melis Arslan. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006. / Includes bibliographical references (p. 218-224). / Model buildings were created for simulation to describe typical office buildings from different construction periods. A simulation program was written to predict the annual energy consumption of the buildings in their original state and after performing retrofit projects. A scenario analysis was performed to determine the most effective retrofit techniques. This information was used to determine to what degree the national energy consumption of office buildings could be reduced through demand side management. The results of the analysis showed that it was possible to reduce the annual energy consumption of the office buildings to a minimum of about 70 km,. If all buildings in the country were to perform these retrofits, the total energy consumption of office buildings would be reduced by about 75%. The most economical choices of retrofit projects for reducing energy consumption were elements of the controls system and the HVAC system. Retrofits to the windows were also beneficial though more costly. Retrofits to the other facade elements and the other energy services system were shown to produce small changes in annual energy consumption for the required investment cost. / by Lisa A. Engblom. / S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006. / Includes bibliographical references (leaves 210-217). / Polymer/clay nanocomposites have been observed to exhibit enhanced thermal/mechanical properties at low weight fractions (We) of clay. Continuum-based composite modeling reveals that the enhanced properties are strongly dependent on particular features of the second-phase "particles"; in particular, the particle volume fraction (f,), the particle aspect ratio (L/t), and the ratio of particle thermal/mechanical properties to those of the matrix. These important aspects of as-processed nanoclay composites require consistent and accurate definition. A multiscale modeling strategy is employed to account for the hierarchical morphology of the nanocomposite: at a lengthscale of thousands of microns, the structure is one of high aspect ratio particles within a matrix; at the lengthscale of microns, the clay particle structure is either (a) exfoliated clay sheets of nanometer level thickness or (b) stacks of parallel clay sheets separated from one another by interlayer galleries of nanometer level height, and the matrix, if semi-crystalline, consists of fine lamella, oriented with respect to the polymer/nanoclay interfaces. Here, quantitative structural parameters extracted from XRD patterns and TEM micrographs (the number of silicate sheets in a clay stack, N, and the silicate sheet layer spacing, d(ool)) are used to determine geometric features of the as-processed clay "particles", including L/t and the ratio of fp to We. / (cont.) These geometric features, together with estimates of silica lamina elastic and thermal expansion properties obtained from molecular dynamics simulations, provide a basis for modeling effective thermal/mechanical properties of the clay particle. In the case of the semi-crystalline matrices (e.g., nylon 6), the transcrystallization behavior induced by the nanoclay is taken into account by modeling a layer of matrix surrounding the particle to be highly textured and therefore mechanically anisotropic. Micromechanical models (numerical as well as analytical) based on the "effective clay particle" were employed to calculate the overall anisotropic elastic constants, anisotropic coefficient of thermal expansion (CTE), and anisotropic yield surface of the amorphous and semi-crystalline polymer-clay nanocomposites and to compute their dependence on the matrix and clay properties as well as internal clay structural parameters. The proposed modeling technique captures the strong modulus enhancements observed in elastomer/clay nanocomposites as compared with the moderate enhancements observed in glassy and semi-crystalline polymer/clay nanocomposites. / (cont.) For the case where the matrix is semi-crystalline, the enhancements of composite modulus and strength are found to rely on different functions of the clay: while the modulus enhancement can be explained by the conventional role of "stiff filler", the strength enhancement of the nanocomposite mainly lies in the improvements of the matrix property achieved through the matrix transcrystallization induced by nanoclay the "nucleation sites". When the nanocomposite experiences a morphological transition from intercalated to completely exfoliated, an abrupt jump in the composite initial yield strength, as opposed to the moderate increase in the overall composite modulus, was predicted. The elastic moduli and anisotropic CTE for MXD6-clay and nylon 6-clay nanocomposites predicted by the micromechanical models are in excellent agreement with experimental data. In summary, continuum-based micromechanical models can provide robust predictions of the overall thermal/mechanical properties of polymer/clay nanocomposites, with the employment of a reliable method to account for the intrinsically hierarchical morphology of the nanoclay, and for the special matrix morphology and properties adjacent to the nanoclay. / by Nuo Sheng. / Ph.D.