Infrared (IR) imaging is a key technology in a variety of military and civilian applications, especially for night vision and remote sensing. Compared with cryogenically cooled IR sensors, uncooled infrared imaging devices have the advantages of being low cost, light weight, and superior reliability. The electro-thermal analysis of a microbolometer pixel is critical to determine both device performance and reliability. To date, most microbolometer analysis research has focused on performance optimization and computation of thermal conductance directly from the geometry. However, modeling of the thermal distribution across the microbolometer pixel is critical for the comprehensive analysis of system performance and reliability. Therefore, this thesis investigates the electro-thermo-mechanical characteristics of a microbolometer pixel considering the effects of joule heating and incoming IR energy. The contributions of the present research include the electro-thermal models for microbolometer and methods of validating thermal distribution using experimental results. The electro-thermal models explain the effect of microbolometer material properties and geometry on device performance and reliability. The research also contributes methods of estimating the thermal conductivity of microbolometer, which take into account different heat transfer mechanisms, including radiation and convection. Previous approaches for estimating the thermal conductance of uncooled microbolometer consider heat conduction via legs from the geometry of the pixel structure and material properties [2]. This approach assumes linear temperature distribution in the pixel legs structure. It also leaves out the various electro-thermal effects existing for multilayer structures. In the present research, a different approach is used to develop the thermal conductance of microbolometer pixel structure. The temperature distribution in the pixel is computed from an electro-thermal model. Then, the average temperature in the pixel microplate and the total heat energy generated by joule heating is utilized to compute the thermal conductance of the structure. The thesis discusses electro-thermal and thermo-mechanical modeling, simulation and testing of Polysilicon Multi-User MEMS Process (PolyMUMPs®) test devices as the groundwork for the investigation of microbolometer performance and reliability in space applications. An electro-thermal analytical and numerical model was developed to predict the temperature distribution across the microbolometer pixel by solving the second order differential heat equation. To provide a qualitative insight of the effect of different parameters in the thermal distribution, including material properties and device geometry, first an explicit formulation for the solution of the electro-thermal coupling is obtained using the analytical method. In addition, the electro-thermal model, which accounts for the effect of IR energy and radiation heat transfer, spreading resistance and transient conditions, was studied using numerical methods. In addition, an analytical model has been developed to compute the IR absorption coefficient of a Thin Single Stage (TSS) microbolometer pixel. The simulation result of this model was used to compute absorbed IR energy for the numerical model. Subsequently, the temperature distribution calculated from the analytical model is used to obtain the deflections that the structure undergoes, which will be fundamental for the reliability analysis of the device. Finite element analysis (FEA) has been simulated for the selected device using commercial software, ANSYS® multiphysics. Finite element simulation shows that the electro-thermal models predict the temperature distribution across a microbolometer pixel at steady-state conditions within 2.3% difference from the analytical model. The analytical and numerical models are also simulated and results for a temperature distribution within 1.6% difference. In addition, to validate the analytical and numerical electro-thermal and thermo-mechanical models, a PolyMUMPs® test device has been used. The test results showed a close agreement with the FEM simulation deflection of the test device.

Diffraction Enhanced X-ray Imaging (DEI) uses synchrotron X-ray beams prepared and analyzed by perfect single crystals to achieve imaging contrast from a number of phenomena taking place in an object under investigation. The crystals used in DEI for imaging requires high precision positioning due to a narrow rocking curve. Typically, the angular precision required should be on the order of tens of nanoradians.<p>One of the problems associated with DEI is the inability to control, set, and fix the angle of the analyzer crystal in relation to the beam exiting the monochromator in the system. This angle is used to interpret the images acquired with an object present and the usual approach is to determine where the image was taken after the fact. If the angle is not correct, then the image is wasted and has to be retaken. If time or dose is not an issue, then retaking the image is not a serious problem. However, since the technique is to be developed for live animal or eventually human imaging, the lost images are no longer acceptable from either X-ray exposure or time perspectives.<p>Therefore, a mechanical positioning system for the DEI system should be developed that allows a precise setting and measurement of the analyzer crystal angles. In this thesis, the fundamental principles of the DEI method, the DEI system at the National Synchrotron Light Source (NSLS) and the sensitivity of the DEI system to vibration and temperature has been briefly studied to gain a better understanding of the problem. The DEI design at the NSLS was analyzed using finite element analysis software (ANSYS) to determine the defects in the current design which were making the system dimensionally unstable. Using the results of this analysis, the new analyzer support was designed aiming to eliminate the problems with the current design. The new design is much stiffer with the natural frequency spectrum raised about eight times. <p> This new design will improve the performance of the system at the National Synchrotron Light Source (NSLS) of Brookhaven National Laboratory, New York, USA and should assist in the development of a new DEI system for the Bio-Medical Imaging and Therapy (BMIT) beamline at the Canadian Light Source (CLS), Saskatoon, CANADA.

The bottleneck of forming small radius tube is that traditional processing methods can¡¦t effectively produce smaller bend radius tube in domestic industry now. First, this study will propose methods without mandrel, based on traditional bending way of rotary draw bending to form small bending radius tubes. This paper investigate results of traditional bending mode without mandrel in second part. By using finite element analysis, find the effects on wall-thinning, wall-thickening and ovility with different processing parameters. Also using the research results to obtain forming ranges. Through heating tubes we explore the possibility of hot forming of parameters and to find the impacts on bending tubes which heating under different parameters. We use the results above to find out the hot forming ranges. In heating and quenching of rotary draw bending experiments, we found that heating tubes under the same processing parameter can effectively enhance the formability and successfully derive better products of small radius bending tubes, to accomplish non-mandrel rotary bending process of small bending radius.

This study focused on analysis and experiment of hot extrusion of aluminum and magnesium alloys, an extrusion die with an inclination angle leads to non- uniform velocity distribution at the cross-section of the die, and results in different strain and strain rate distributions. This kind of design can make the grain size at the material surface smaller and get a material with larger surface hardness. This study aims to conduct hot extrusion with different die inclination angles, and obtain a material with gradient micro-structures. At first, die with different inclination angles are designed, and the temperature at the die exit and effective strain, effective strain rate distributions are discussed using the finite element analysis. At last, aluminum and magnesium extrusion experiments are conducted and the micro-structures of the materials are observed to understand the effects of the die inclination angles at 15 degrees on the grain size distribution and hardness test at the cross-section of the material. The grain size is about 17.2£gm at around center of the cross-section and hardness is about 68.2HV. The smallest grain size is 4.1£gm at the edge of the cross-section and the highest hardness is 83.8HV.

This study is to analyze and test the extrusion process of a hollow spur gear and a solid helical product with magnesium alloy. In the hollow spur gear part, firstly, a design criterion to determine the forming parameters is proposed. Then, the Finite Element Analysis is used to simulate the flow pattern of the billet from separating channel, welding chamber to die bearing part. From a series of simulation results, the effect of separating channel length, mandrel entrance angle, welding chamber height, etc. on the radial filling ratio, welding pressure, extrusion load, etc. are found. By using the Taguchi Methods, we can find the most important parameters. Finally, a better die geometry is designed to obtain a sound product. In the helical product part, the Finite Element Analysis is used to get the understandings of radical filling ratio of magnesium alloy in the helical zone. Then, a better die geometry is designed from the results of analyses. Finally, hot extrusion experiments of a hollow spur gear and a solid helical product are conducted. The experimental values of the extrusion load and the product¡¦s dimension are compared with the analytic values to verify the validity of the analytic models.

The temperature and thermal stress distributions and variations of the high power LED module were studied in this work. The thermal-elastic-plastic 3D finite element models of MSC.marc software package are employed to simulate these performances for the high power LED module. Two high power white light LED module designs are investigated¡G one is the traditional phosphorescent silicone with blue LED module and the other is a phosphor glass lens with blue LED module. The distributions of temperature and thermal stress of in these two operating LED modules are compared and discussed. The effects of different packaging parameters¡Ge.g. bonding materials, substrate materials, lens materials on the temperature and thermal stress have also been studied in this work. The simulated results reveal that the serious thermal crack may occur for these two designs if the power of single die is over 10 watt. The simulated results also indicate that an attached fin cooler may improve these thermal crack disadvantaged significantly. The effect of fin design parameters on the peak temperature reduction has studied. A feasible fin design for the high power LED module has also been proposed.

Screws are produced by four manufacturing processes : extrusion, drawing, heading and thread-rolling. This paper will develop the related manufacturing technology of LZ91 magnesium alloy screws. At first, finite element simulation is adopted to analyze the effects of each process parameters on the formability. Then, each process experiments are conduted to manufacture an M6 magnesium alloy screw. Comparisous between analytical and experimental results verify the suitability and accuracy of the analytical models. In the extrusion process, by the finite element simulations the extrusion load is obtained. Then bar extrudsion experiments with high extrusion ratioto manufacture two bars of 6.5 and 7 mm in diameter using a 350 ton extrusion machine . In the drawing process, the effects of reduction and friction factor on the optimal semi-die angle are discussed, and the relationship is found. Then a rod of 7.0 mm in diameter is drawn into 6.5 mm experimentally. In the heading process, three stages in it`s process are designed. The arc shape and axial length of the die for the first stage are found out. Finally, heading experiments are conducted and sizes between the product and the simulation results are compared. In thread-rolling process, the effects of the screw plate gap on the formability are discussed numerically. Then, thread-rolling experiments are conducted to compare the sizes of the product and the simulation results. In addition, microstructure observation and hardness test are conducted to understand the effects of drawing process on the strength of the product.

Profile strips have been used in various industries and now the demand of profile strip is still growing. Due to different reductions at different parts of the strips, profile strips after rolling generate a defect which looks like a wave. This study will design and manufacture a four-high profile rolling mill, which can roll profile strips. Experiments and finite element simulation are conducted to discuss the effects of different parameters on strip size and the defect of the profiled strips. In this study, a finite element analysis software is used to establish profile rolling models with different material setting mode, reduction, temperature, material, tension, and roll shape. From the simulation results, the effects of these parameters on the defects are discussed. Secondly, profiled rolls are designed and a heating equipment is added on the four-high rolling mill, and rolling experiments with different reduction, materials, passes of process, roll shape and temperature are conducted. From the experimental results the effects of these parameters on size of the defect of profile strip are discussed. Finally, from the comparisons between simulation results and experiment results, the feasibility of finite element models are verified.

Anti ram perimeter barriers are part of the protection of important facilities such as power plants, air ports and embassies against unrestricted vehicle access. Many different systems can be used to achieve the containment goal. One of these systems makes use of soil embedded posts either single posts if the soil is hard enough or groups of soil embedded posts tied together by beams if the soil is not hard enough for a single post to stop the in-coming truck. The design of these soil embedded posts needs to take account a number of influencing factors which include the soil strength and stiffness, the post strength and stiffness, the mass of the vehicle and its approach velocity. This dissertation describes the work done to develop a set of design recommendations to select the embedment of a single post or group of posts. The post is a steel beam with an H shape cross section: W14X109 for the single post system and W14X90 for the group system with a double beam made of square hollow steel section HSS8X8X1/2. The spacing of the posts for the group includes 2.44 m, 4.88 m, and 7.32 m. The soil strength varies from loose sand and soft clay to very dense sand and very hard clay. The vehicle has a mass of 6800 kg and the velocities include 80 km/h, 65 km/h, and 50 km/h. The design guidelines presented here are based on 10 medium scale pendulum impact tests, 2 medium scale bogie impact tests, 1 full scale impact test on a single post, 1 full scale impact test on a group of 8 side by side posts with a 5.2 m spacing and connected with two beams, approximately 150 4-D numerical simulations of full scale impact tests using LS-DYNA, as well as fundamental theoretical concepts.

This thesis employs a finite element (FE) method for numerically simulating the mechanical response of constituents in a fiber-reinforced polymer (FRP) composite to indentation. Indentation refers to a procedure that subsumes a rigid indenter of specific geometry to impress the surface of a relatively softer material, with a view of estimating its mechanical properties. FE analyses are performed on a two-dimensional simplified microstructure of the FRP composite comprising perfectly bonded fiber, interphase and matrix sections. Indentation response of the constituents is first examined within the context of linearized elasticity. Time-dependent response of the polymer matrix is invoked by modeling the respective constituent section as a linear isotropic viscoelastic material. Furthermore, indentation responses to non-mechanical stimulus, like moisture absorption, is also simulated through a sequentially coupled analysis. A linear relationship describing the degradation of elastic moduli of the individual constituents with increasing moisture content has been assumed. The simulations subsume a point load idealization for the indentation load eventually substituted by indenter tips with conical and spherical profiles. Results from FE analyses in the form of load-displacement curves, displacement contours and stress contours are presented and discussed. With the application of concentrated load on linearly elastic constituents for a given/known degree of heterogenity in the FRP, simulations indicated the potential of indentation technique for determining interphase properties in addition to estimating the matrix-fiber interphase bond strength. Even with stiffer surrounding constituents, matrix characterization was rendered difficult. However, fiber properties were found to be determinable using the FE load-displacement data, when the load-displacement data from experimentation is made available. In the presence of a polymer (viscoelastic) matrix, the surrounding elastic constituents could be characterized for faster loading rates when viscoelastic effects are insignificant. Displacements were found to be greater in the presence of a polymer matrix and moisture content in comparison with a linearly elastic matrix and dry state. As one would expect, the use of different indenter tips resulted in varying responses. Conical tips resulted in greater displacements while concentrated load produced greater stresses. Further it was found that, despite the insignificant effects due to surrounding constituents, analytical (Flamant) solution for concentrated, normal force on a homogeneous, elastic half-plane becomes inapplicable in back calculating the elastic moduli of individual FRP constituents. This can be attributed to the finite domain and the associated boundary conditions in the problem of interest.