Conceptual design and analysis of a large antenna utilizing electrostatic membrane management

Conceptual designs and associated technologies for deployment 100 m class radiometer antennas were developed. An electrostatically suspended and controlled membrane mirror and the supporting structure are discussed. The integrated spacecraft including STS cargo bay stowage and development were analyzed. An antenna performance evaluation was performed as a measure of the quality of the membrane/spacecraft when used as a radiometer in the 1 GHz to 5 GHz region. Several related LSS structural dynamic models differing by their stiffness property (and therefore, lowest modal frequencies) are reported. Control system whose complexity varies inversely with increasing modal frequency regimes are also reported. Interactive computer-aided-design software is discussed

Mechanical loss and its significance in the test mass mirrors of gravitational wave detectors

The work of this thesis involves the analysis of mechanical losses associated with coated test masses manufactured from fused silica, to determine the existence and level of excess loss associated with the coatings on these substrates. In particular, a major part of this analysis requires the calculation of the ratio of the strain energy stored in the dielectric coating to the strain energy stored in the substrate for a number of the resonant modes of the test mass. This is extremely difficult to calculate analytically for all but the simplest of modes. Finite element analysis had to be used to calculate the modeshapes of a number of resonant modes of the test masses. A piece of analytical software was specifically written to use the output of the finite element analysis package to calculate these energy ratios. The majority of this thesis is concerned with the methodology and usage of this software in the context of a number of analyses of different coated test masses. In addition, a technique was developed to allow experimental determination of modeshapes. This method could then be used to confirm or identify the nature of different modes. An initial investigation suggested that the loss associated with the coating s may prove significant for future generations of detectors such as Advanced LIGO. Further investigations suggested that the principle source of coating loss was due to the materials used in the coatings themselves. These investigations also suggested that for the coatings used, which were manufactured using tantalum pentoxide and silica, the tantalum pentoxide had a higher mechanical loss than the silica. Investigations into different coating materials have been initiated. Finally, preliminary tests on a coated sapphire mirror have been completed which give an upper limit to the loss of a coating on a sapphire mass. These tests required comprehensive changes to be made to the analytical energy ratio software to allow the analysis of anisotropic materials such as sapphire and to allow the output from different finite element packages to be used

3-D inelastic analysis methods for hot section components (base program)

A 3-D inelastic analysis methods program consists of a series of computer codes embodying a progression of mathematical models (mechanics of materials, special finite element, boundary element) for streamlined analysis of combustor liners, turbine blades, and turbine vanes. These models address the effects of high temperatures and thermal/mechanical loadings on the local (stress/strain) and global (dynamics, buckling) structural behavior of the three selected components. These models are used to solve 3-D inelastic problems using linear approximations in the sense that stresses/strains and temperatures in generic modeling regions are linear functions of the spatial coordinates, and solution increments for load, temperature and/or time are extrapolated linearly from previous information. Three linear formulation computer codes, referred to as MOMM (Mechanics of Materials Model), MHOST (MARC-Hot Section Technology), and BEST (Boundary Element Stress Technology), were developed and are described

Processing, microstructure and mechanical properties of beta-type titanium porous structures made by additive manufacturing

Tissue engineering through the application of a low modulus, high strength format as a potential approach for increasing the durability of bone implants has been attracting significant attention. Titanium alloys are widely used for biomedical applications because of their low modulus, high biocompatibility, specific strength and corrosion resistance. These reasons affirm why titanium alloy is selected as the specific material to research. The development of low modulus biomaterials is considered to be an effective method to remove the mismatch between biomaterial implants and surrounding bone tissue, thereby reducing the risk of bone resorption. So far, Ti–24Nb–4Zr–8Sn alloy (abbreviated hereafter as Ti2448) is considered to be a biomedical titanium alloy with low modulus, and was invented for biomaterial application. However, the modulus of Ti2448 (42-50 GPa) is still higher than that of bone (1-30 GPa). A scaffold is an ideal structure for bone implants; such a structure can further reduce the modulus of an implant. This structure also has the desired effect of promoting bone in-growth. Additive manufacturing could prepare porous titanium parts with mechanical properties close to those of bone tissue. However, the properties of scaffolds are affected by manufacturing strategies and parameters such as the scanning speed, the input power, the layer thickness, the scanning strategy, the temperature of the platform and the hatch distance. Each of these parameters can affect a scaffold’s properties and performance in terms of density, hardness, super-elastic property, compressive and fatigue properties. For the Ti2448 alloy, all of these manufacturing parameters are still not clear enough to develop the perfect porous structure. This study will examine the performance of biomaterial Ti2448 scaffolds by tuning the main parameters of additive manufacturing (AM) systems through an analysis of the microstructure and the mechanical properties of the produced components

Simultaneous measurement for material parameters using self-mixing interferometry

Material related parameters such as Young’s modulus and internal friction are important for mechanical and material engineering. These parameters play key roles in the material performances. It has been a great interest to measure the value of these parameters. Traditional methods including tensile test, flexure test, and others are destructive methods often cause damages to specimen and have low accuracy. In recent years, the impulse excitation technique (IET), a non-destructive technique to determine Young’s modulus and internal friction of the material has attracted great attention. The detection system used for IET is normally microphone, accelerometer and so on. Selfmixing interferometry (SMI), an emerging sensing technique, which is non-destructive, non-contact, compact structure, and low-cost has been developed for high accuracy sensing applications, such as displacement, velocity and distance measurement and so on is suitable for the material related parameters measurement. A normal SMI system consists of a laser diode (LD) and a target to form the external cavity of the LD. When a portion of the light is reflected or backscattered to the laser cavity, leading to a modulated laser power of LD. This modulated laser power is referred as SMI signal, which carries the information of vibration of the target. In this thesis, a measurement method combining IET with SMI for material related parameters measurement is proposed. By applying wavelet transform onto the SMI signal, both resonant frequency and damping factor of the specimen vibration can be retrieved at the same time. Therefore, both Young’s modulus and internal friction of the specimen can be calculated simultaneously. The optical fibre is introduced to the system. With the installation of the optical fibre, the flexibility of the measurement is greatly improved. The measurement results show the feasibility for simultaneous measurement of material related parameters. A graphical user interface is designed to improve the user experience for the measurement

Development of engineering tools to analyze and design flexible structures in open ocean environments

Methods to effectively predict system response in marine settings are critical in the engineering design process. The high energy ocean environment can subject structures to large wave and current forces, causing complex coupled motions and loads. This research focused on the development of effective methods to predict flexible system response and the structural integrity of marine High Density Polyethylene (HDPE) components. Numerical modeling tools were developed to analyze and design flexible structures in open ocean environments. Enhancements to the University of New Hampshire\u27s Aqua-FE finite element computer program were performed, including expansion of the element library to include spherical geometries and implementation of various hydrodynamic effects such as Stokes 2nd order waves and water velocity reduction due to component shadowing. Two case studies, involving laboratory and field experiments, were performed evaluating the software modifications and examining the response of flexible systems in various environmental conditions. Practical applications of the numerical model are presented, focusing on the design, analysis and deployment of a submerged grid mooring 10 km from Portsmouth, NH. The system was recovered after a seven year deployment and inspected. The numerical model proved to be a valuable engineering tool for investigating a system\u27s motion dynamics and mooring tension response in marine environments. High density polyethylene is a primary structural component for marine systems such as fish containment, wave attenuators and marine defense barrier systems. The fundamental engineering issues with the compliant HDPE material are associated with how the material changes its stiffness and strength depending upon the service life, load rate and temperature. Structural modeling techniques were developed to determine effective methods of analyzing marine systems constructed of HDPE. This included the investigation of the mechanical behavior of new and environmentally fatigued HDPE specimens, obtained from commercial fish farms, at different strain rates and validation of the modeling approach with laboratory experiments. The operational limits, loads and modes of a failure of the HDPE cage frame were estimated, providing valuable information on the survivability of these large, flexible systems in offshore environments

3D Printing of Functional Materials: Surface Technology and Structural Optimization

There has been a surge in interest of 3D printing technology in the recent 5 years with respect to the equipment and materials, because this technology allows one to create sophisticated and customized parts in a manner that is more efficient regarding both material and time consumption. However, 3D printing has not yet become a mainstream technology within the established manufacturing routes. One primary factor accounting for this slow progress is the lack of a broad variety of 3D printable materials, resulting in limited functions of 3D printed parts. To bridge this gap, I present an integrated strategy to fabricate a variety of functional materials/devices through the post-printing surface modification and target-motivated structural topology. A reusable 3D printed filter was first demonstrated to remove metal ions from water. This filter was functionalized with a layer of bio-adsorbent grown on its surface using post-printing modification, and the capacity was improved through structural optimization. To further improve the working efficiency, a customized 3D all-in-one printable material system was employed, which uses only one 3D printing material, but can realize various functionalities through a post-printing process. This material system is applicable for all types of photo-polymerization based 3D printing routes, including DLP, SLA, polyjet and other emerging technologies. It has significantly extended the capacity of current 3D printing technology. The 3D printed structures were converted into useful devices with new functions or new structural metamaterials with novel properties, that are attributed to both their materials composition and structural design. For example, we have showcased the magnetically manipulated robot, strength-enhanced lattice materials with high effective strength, ultralight metal materials and mechanical-metamaterials. In this thesis, a new generation of initiator-integrated material system was also developed. Beyond being able to successfully 3D print functional devices/materials with desirable properties, I also demonstrated that this initiator-laden material can be utilized to locally repair the surface damage, allowing a self-healing ability. In general, the developed 3D printing process that incorporates surface modification and structural topology enables a new class of functional devices/materials to be produced, and opens a door for further research and development of an increasing variety of 3D printing applications. Through the work presented in this dissertation, I substantially build upon and further establish the strategy and material system for 3D printing functional devices/materials, keeping in mind components, design, engineering and application

異種ダイレット積層を用いたフレキシブルハイブリッドデバイスの集積技術に関する研究

Tohoku University福島誉史課