Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1979. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaves 201-208. / by William Simon Dershowitz. / M.S.

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Lamina Emergent Mechanisms (LEMs) are a class of compliant mechanisms that can be manufactured from sheet goods and possess motion out of the plane of fabrication. LEMs can be designed to perform sophisticated motions. This thesis expands LEM understanding and increases the ability to utilize them in applications by introducing the fundamentals of spherical LEMs, creating joints suitable for LEMs, and providing an example of a LEM application. In this thesis, the fundamentals of spherical LEMs are developed. This includes classification of all possible spherical 4R LEMs and a discussion of the motion characteristics of the various mechanisms. The motion characteristics associated with spherical 4R LEMs are then used to predict the motion of spherical 6R LEMs and arrays of spherical LEMs. Multiple spherical LEM prototypes are shown and discussed. A common difficulty of working with compliant mechanisms, especially LEMs, is creating suitable joints. There is often a trade off between flexibility in the desired direction of deflection, and stiffness in directions of undesired deflection. For this thesis, LEM joints that possess higher off-axis stiffness, especially in tension and compression, than previous designs were developed: the I-LET, the T-LET, and the IT-LET. Joint geometries were optimized and then modeled in commercial finite element analysis (FEA) software capable of nonlinear analysis. These models were used to predict the bending of tensile/compressive stiffnesses of the joints. As a benchmark, lamina emergent torsional (LET) joints were modeled and optimized for maximum tension and compression loading while maintaining the same bending stiffness as the joint being compared. Mechanisms that utilized the new joints were created and are briefly discussed. The use of these joints allows for minimized parasitic motion under tension and compression loads and expands the capability of LEM joints. The Lens Lift™ was developed to demonstrate an application of LEMs. The Lens Lift™ is a LEM device that allows for easier and more sterile use of disposable contact lenses. It possesses a monolithic structure and can be fabricated using simple manufacturing processes. As the contact lens user opens the blister pack used to store the lens, the lens is lifted out of the pack and presented to the user. The user can then lift the lens with one touch and place it in the eye. A provisional patent has been filed for the device and the device currently being evaluated by a major contact lens manufacturer for further development.

This thesis presents an application of a numerical formulation incorporating the effects of joints, cracks, and fractures to a soil subsidence predictions problem, and the extension of that formulation to combined discrete slip planes and jointed media continua formulations. The results obtained are compared to each other and to a physical centrifuge simulation performed previously on the same problem.

Thesis: M.S., Massachusetts Institute of Technology, Department of Mechanical Engineering, 1980 / Bibliography: leaves 216-232. / by Francis Joseph Halcomb, III. / M.S. / M.S. Massachusetts Institute of Technology, Department of Mechanical Engineering

No / This paper described the finite element modelling of the semi-rigid composite beam-column joints with the composite steel beams and precast hollowcore slabs which can accurately simulate the moment-rotation response of the connections. Using the general purpose finite element software ABAQUS, a three dimensional model of the composite joint is set up. The techniques of simulating the bolt force, the endplate, the concrete elements, the reinforcement, the shear connectors and the interaction between the slabs and the steel beams are discussed. The results are presented and compared with the experimental data and good agreement is obtained. Parametric studies using the developed model will be performed to gain better understanding of this form of composite joints.

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