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Thesis (M.S.)--Brigham Young University. Dept. of Mechanical Engineering, 2007. / Includes bibliographical references (p. 39-40).

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Origami-adapted mechanisms form the basis of an increasing number of engineered systems. As most of these systems require the use of non-paper materials, various methods for accommodating thickness have been developed. These methods have opened new avenues for origami-based design. This work introduces approaches for the design of two new classes of thick-origami systems and demonstrates the approaches in hardware. One type of system, called "conceal-and-reveal,'' is introduced, and a method of designing these mechanisms is developed. Techniques are also developed for designing folding printed circuit boards which are fabricated from a single sheet of material. This enables areas of regional flexibility, leaving other areas stiff. This allows components to be attached to stiff regions and folding to occur at flexible regions. An optimization method is presented to design the geometry of surrogate hinges to aid in monolithic origami-based mechanisms such as flexible PCBs. Examples are shown which demonstrate each of these new techniques.

The goal of this thesis is to develop an efficient finite element model of a particular micro-positioning(MP) system, known as the 3RRR Mechanism. MP systems are capable of delivering accurate and controllable motion in the micro-metre to sub-micrometre range. Conventional mechanisms, which are often composed of rigid links with pinned connections are prone to friction, backlash and stiction, which are magnified at small displacements. As such MP systems utilize a new structure known as the compliant mechanism. The structure of most compliant mechanisms is based on conventional mechanisms; however they are monolithic devices which utilize flexible elements, instead of pins, to transform the input to a useful output position. One common flexible element found in compliant mechanisms is the right circular flexure hinge. The seminal work on flexure hinges was done by Paros and Weisbord(1965), the basis of which was to calculate compliance (the reciprocal of stiffness) in order to characterize the behaviour of the hinge when loaded. However they essentially modelled the flexure hinge as a 1-D beam, when it is in fact 3-D in nature. Researchers completing finite element models of MP systems and flexure hinges have extended the model to 2-D elements, still resulting in poor results when compared to experimental data. The task of completing a full 3-D finite element model of a MP system, let alone a right circular flexure hinge, is a major computational effort. For instance, a full 3-D model of the 3RRR mechanism would require over 1,000,000 degrees of freedom(DOF) dedicated to the flexure hinges alone. A 2-D model requires approximately 45,000 DOF in total; however, this number is still regarded as large. Given these facts, a new technique called the Equivalent Beam Methodology(EBM) has been developed to model the 3-D stiffness of any right circular flexure hinge with a low number of DOF. This method essentially maps the 3-D stiffness of the hinge to a number of 1-D beam elements. For comparison, the finite element model of the 3RRR mechanism which incorporates the beams of the EBM has under 300 DOF in total, and is more accurate than the 2-D model. This method is extremely accurate, easy to use, and has a very low number of DOF, which makes it suitable to many advanced finite element modelling analyses such as topographic optimization, dynamic and modal analysis.

The goal of this thesis is to develop an efficient finite element model of a particular micro-positioning(MP) system, known as the 3RRR Mechanism. MP systems are capable of delivering accurate and controllable motion in the micro-metre to sub-micrometre range. Conventional mechanisms, which are often composed of rigid links with pinned connections are prone to friction, backlash and stiction, which are magnified at small displacements. As such MP systems utilize a new structure known as the compliant mechanism. The structure of most compliant mechanisms is based on conventional mechanisms; however they are monolithic devices which utilize flexible elements, instead of pins, to transform the input to a useful output position. One common flexible element found in compliant mechanisms is the right circular flexure hinge. The seminal work on flexure hinges was done by Paros and Weisbord(1965), the basis of which was to calculate compliance (the reciprocal of stiffness) in order to characterize the behaviour of the hinge when loaded. However they essentially modelled the flexure hinge as a 1-D beam, when it is in fact 3-D in nature. Researchers completing finite element models of MP systems and flexure hinges have extended the model to 2-D elements, still resulting in poor results when compared to experimental data. The task of completing a full 3-D finite element model of a MP system, let alone a right circular flexure hinge, is a major computational effort. For instance, a full 3-D model of the 3RRR mechanism would require over 1,000,000 degrees of freedom(DOF) dedicated to the flexure hinges alone. A 2-D model requires approximately 45,000 DOF in total; however, this number is still regarded as large. Given these facts, a new technique called the Equivalent Beam Methodology(EBM) has been developed to model the 3-D stiffness of any right circular flexure hinge with a low number of DOF. This method essentially maps the 3-D stiffness of the hinge to a number of 1-D beam elements. For comparison, the finite element model of the 3RRR mechanism which incorporates the beams of the EBM has under 300 DOF in total, and is more accurate than the 2-D model. This method is extremely accurate, easy to use, and has a very low number of DOF, which makes it suitable to many advanced finite element modelling analyses such as topographic optimization, dynamic and modal analysis.

Abstract This paper reports about a precision positioning XY stage utilizing flexure hinges and piezoelectric actuators. XY stage was designed with the aim of reducing the stress-concentration of flexure hinges and the low interference between two actuating axes. Utilized the expression of matrix to figure out the properties of the bellow-type flexure hinges, and proved these by mathematical software. Experiments demonstrated that the stage actuated by a stairstep driving signal with maximum displacement 1.3£gm and interference 50nm along X axis; along Y axis with maximum displacement 0.8£gm and interference 11nm. The stage actuated by a ramp signal with maximum displacement 1.2£gm and interference 45nm along X axis; along Y axis with maximum displacement 0.9£gm and interference 35nm. The finite element method (FEM) was used to analyse the stress-concentration of the stage. and the simulated results were compared with the experiments. Referred to the testing results, the target object could be moved in the aimed position accurately.

The New Zealand Structural Loading Standard, until its latest revision, was using the structural displacement ductility factor as a measure of the deformation demand of all potential plastic hinges in a structure. In the revised version of New Zealand Structural Loading Standard for Earthquake Actions (NZS 1170.5:2004) the detailing of potential plastic regions is determined according to the local inelastic deformation demand in these regions. The change has been prompted by evidence that the structural ductility factor gives a poor indication of the demand on individual plastic regions. This is a major paradigm shift in international design codes. This new approach has been adopted by the New Zealand Concrete Structures Standard (NZS 3101:2006) which classifies potential plastic regions into three categories (namely ductile, limited ductile and nominally ductile) based upon their inelastic deformation demand which has been specified in terms of material strain limits in the form of curvatures or shear deformations. The values of material strain limits currently used in New Zealand Concrete Standard (NZS 3101:2006) to categorise the plastic regions are based on limited evidence and need a closer revision. This research attempts to obtain more justifiable values of material strain limits through experimental data existing in literature. Moreover, experimental testing is also conducted to compensate for a lack of data in the nominally ductile range of detailing. The experimental work explores the effects of transverse reinforcement arrangement, reinforcing steel grade and plastic hinge type. Together the literature review and experimental work provide a sound basis for re-defining the material strain limits for different plastic regions.