The term Gossamer is used to describe ultra-lightweight spacecraft structures that solve the aerospace challenge of obtaining maximum performance while reducing the launch costs of the spacecraft. Gossamer structures are extremely compliant, which complicates control design and ground testing in full scale. One approach is to design and construct smaller test articles and verify their computational models experimentally, so that similar computational models can be used to predict the dynamic performance of full-scale structures. Though measurement of both in-plane and out-of-plane displacements is required to characterize the dynamic response of the surface of these structures, this thesis lays the groundwork for dynamic measurement of the in-plane component. The measurement of thin films must be performed using non-contacting sensors because any contacting sensor would change the dynamics of the structure. Moreover, the thin films dealt with in this work are coated with either gold or aluminum for special applications making the film optically smooth and therefore requiring a surface pattern. A Krypton Fluoride excimer laser system was selected to fabricate patterns on thin-film mirror test articles. Parameters required for pattern fabrication were investigated. Effects of the pattern on the thin-film dynamics were studied using finite element analysis. Photogrammetry was used to study the static in-plane displacement of the thin-film mirror. This was performed to determine the feasibility of the photogrammetric approach for future dynamic tests. It was concluded that photogrammetry could be used efficiently to quantify dynamic in-plane displacement with high-resolution cameras and sub-pixel target marking.

Many geological numerical models are initiated with a background stress state of zero. Often these numerical results are compared directly to geodetic data. Recent work (Kenner and Simons, 2004) has shown that modeled deformation rates can change as the model is cycled-up following repeated earthquakes or rifting events. In this study, we investigate model cycle-up in the context of time-dependent deformation following rifting during the 1975-1984 Krafla eruption in Iceland. We consider the number of rifting cycles required for complete cycle-up, variations in cycle-up time at different locations in the model, background stress magnitudes in fully cycled-up models, and errors incurred when the models are not properly cycled-up. The modeling is done using the commercial software ABAQUS. In ABAQUS a user-defined subroutine is used to apply repeated rifting events within the finite element model. We have generated various 3D models with different fault/rift geometries. The models include (1) a straight rift oriented perpendicular to the far-field velocity boundary conditions, (2) a rift oriented at an angle to the far-field velocities, (3) a model containing two intersecting rifts, one perpendicular to the far-field velocities and the other rift intersecting the first at an angle, and (4) overlapping rift segments in which the overlapped region is bounded by strike-slip faults.

Friction stir processing (FSP) is one of the new and promising thermomechanical processing techniques that alters the microstructural and mechanical properties of the material in single pass to achieve maximum performance with low production cost in less time using a simple and inexpensive tool. Preliminary studies of different FS processed alloys report the processed zone to contain fine grained, homogeneous and equiaxed microstructure. Several studies have been conducted to optimize the process and relate various process parameters like rotational and translational speeds to resulting microstructure. But there is only a little data reported on the effect of the process parameters on the forces generated during processing, and the resulting microstructure of aluminum alloys especially AA5052 which is a potential superplastic alloy. In the present work, sheets of aluminum alloys were friction stir processed under various combinations of rotational and translational speeds. The processing forces were measured during the process and the resulting microstructure was analyzed using TEM. The results indicate that the processing forces and the microstructure evolved during FSP are sensitive to the rotational and translational speed. It is observed that the forces generated increase with the increasing rotational speed. The grain refinement was observed to vary directly with rotational speed and inversely with the translational speed. Also these forces generated were proportional to the grain refinement i.e., greater refinement of grains occurred at lower forces. Thus the choice of process parameters especially the rotational speed has a significant effect on the control and optimization of the process.

Capacitive displacement sensors have many applications where non-contact, high precision measurement of a surface is required. Because of their non-contact nature they can easily measure conductive surfaces that are flexible or otherwise unable to be measured using a contact probe. Since the output of the capacitance gage is electrical, data points can be collected quickly and averaged to improve statistics. It is often necessary for capacitive displacement sensors to gage the distance from a curved (non-flat) surface. Although displacements can easily be detected, the calibration of this output can vary considerably from the flat case. Since a capacitance gage is typically factorycalibrated against a flat reference, the experimental output contains errors in both gain and linearity. A series of calibration corrections is calculated for rectifying this output. Capacitance gages are also limited in their overall displacement travel. A support stage is described that, along with control electronics, allow the properties of the capacitance gage to be combined with an interferometer to overcome this displacement limitation. Finally, an application is proposed that would make use of the capacitance sensor and support stage assembly.

Multi-piece wheels or rims used on large vehicles such as trucks, tractors, trailers, buses and off-road machines have often been known for their dangerous properties because of the large number of catastrophic accidents involving them. The main causes for these accidents range from dislocation of the rim components in the assembly, mismatch of the components, manufacturing tolerances, corrosion of components to tires. A finite element analysis of a two-piece rim design similar to one manufactured by some of the prominent rim manufacturers in the USA is undertaken. A linear static deformation analysis is performed with the appropriate loading and boundary conditions. The dislocation of the side ring with respect to the rim base and its original designer intent position is established using simulation results from ANSYS and actual rim failure cases. Reliability of the multi-piece rims is analyzed using the failure data provided by the rim manufacturers in connection with a lawsuit (Civil Action No. 88-C-1374). The data was analyzed using MINITAB. The effect of an OSHA standard (1910.177) on servicing multi-piece rims was studied for change in failure patterns of different rims. The hazard functions were plotted and failure rates were calculated for each type of rim. The failure rates were found to be increasing suggesting that the standard had minimal effect on the accidents and failures. The lack of proper service personnel training and design defects were suggested as the probable reasons for the increasing failure rates.

This project was concerned with the development of a finite element model capable of simulating a drop-impact event of handheld radio devices. Handheld radios call for exceptional robustness and reliability due to their deployment in critical applications. The development of a drop-impact finite element model aims to provide greater understanding of impact behaviours, this insight would ultimately be used to develop more robust and optimised handheld electronic products. Before such analysis tools can be introduced into the product development cycle an understanding of finite element methods, of setup parameters for the finite element solver and the accuracy of simulation results must be considered. Experimental results were used throughout the project to validate the finite element models developed. A drop-impact test rig was designed and constructed to control both impact orientation and velocity of the handheld radios tested. Drop-impact modelling of a handheld radio is extremely challenging because of the complex interaction of the contacting surfaces, the complex stress-strain and damping characteristics of the materials, and the excitation of the high frequency modes. For this reason, the finite element model was developed in two stages: a simplified radio was used to develop the understanding of the above complexities and then the understanding implemented in a more detailed radio model. The mesh size of the finite elements, the elastic and the damping characteristics of the materials and the contact conditions for the simplified radio model were varied to understand their influence on the simulation results. The finite element input settings and parameters were altered to give better agreement with the experimental results of the simplified radio model. The detailed radio was subsequently modelled. The lessons learnt from the simplified radio model were applied to the analysis of the detailed radio assembly. Despite general agreements, there were some differences between the finite element and experimental results which was attributed to the high complexity of the model. The project delivered a workable finite element model capable of analysing the drop-impact event of handheld radio devices. Suggestions have been provided that would further improve the quality of the model.

The main objective of this research work is to develop a simulation procedure for modeling the soil-tool interaction for a blade of arbitrary shape. The primary motivation for this study is developing agricultural robots with limited power and pulling force to help farmers in crop production. In this thesis, a finite element (FE) investigation of soil-blade interaction is presented. The soil is considered as an elastic-plastic material with the non-associated Drucker-Prager constitutive law. A separation procedure to model the cutting of soil and a method of calculating the forces acting on the blade are proposed and discussed in detail. The procedure uses a separation criterion that becomes active at consecutive nodes on the predefined separation surfaces. In order to mimic soil-blade sliding and soil-soil cutting phenomena contact elements with different properties are applied. To verify correctness of the FE model developed and the procedures used, the FE results are first compared with analytical results available for straight rectangular blades from classical soil mechanics theories; and then the FE results are compared with the experimental ones. Also the effects of blade width, depth and rake angle on blade’s draft force were studied by simulating soil-blade interaction with different blade’s dimensions. After the analytical and experimental validation of the results for straight rectangular blade, the rectangular curved shape blade was modeled in order to investigate the effects of changing the blade’s radius of curvature on the blade’s draft force. The soil interaction with straight triangular blade in different rake angles was simulated next. Since the analytical solutions are limited to rectangular blades, calculated draft forces for triangular blade were verified only experimentally. The triangular and rectangular blades with the same width and depth of interaction were also investigated. The results showed that triangular blade draft force is around half of the amount of force acting on the rectangular blade with the same rake angle. Also the effect of triangular blade’s sharpness and changing the blade’s radius of curvature on draft force was discussed. By changing the blade’s sharpness, the draft forces of triangular blade were calculated in two conditions of constant blade’s width and constant blade’s contact length. The approach presented in this thesis can be used to investigate the soil-tool interactions for real and more complex blade geometries and soil conditions, and ultimately for improving design of blades to be used in tillage operations.

The goal of this thesis is to improve the understanding of the stitch bonding process in microelectronic wire bonding. In particular, it focuses on investigating the effect of the process parameters bonding force, scrub amplitude, and skid on experimental bond quality responses, including qualitative (non-sticking, sticking, and tail-lifting) and quantitative (stitch pull force, tail pull force). In addition to the experimental work, a finite element (FE) model is developed for the stitch bonding process using ABAQUS software, and compared with the experimental observations. For the first set of experiments, the stitch bonding is performed with a 18 ??m diameter Pd coated Cu (PCC) wire on a ???low bondability??? Au/Ni/Pd plated quad-flat non-lead (QFN) substrate. Results showed that a high bonding force, a high scrub amplitude, and a positive skid provoke the sticking of the stitch bond and reducing the chance of non-sticking observation. However, such parameters also increase the chance of tail-lifting. As a trade-off for a low bondability substrate, a process parameter combination containing a high bonding force and a high scrub amplitude and a negative skid could ensure a strong enough stitch bonding process with low chance of tail-lifting. For the second set of experiments, the stitch bonding is performed with a 18 ??m diameter uncoated Cu wire on a ???high bondability??? Ag plated QFN substrate. Statistical analysis of stitch and tail pull force showed that the skid and scrub parameters have a more significant influence than bonding force. A positive skid can degrade the stitch pull force, while enhancing the tail pull force. A high scrub amplitude is found to degrade both the stitch and the tail pull forces. The bonding force is shown to improve the stitch and tail pull forces slightly. Performing an optimization, process parameters of 70 gf (687 mN) bonding force, 3 ??m scrub amplitude, and zero skid result in acceptable stitch and tail pull forces, along with a reliable stitch bond appearance (low peeling and shallow capillary tool impression). The influence of the process parameters is significantly different depending on if bonding on low or high bondability substrates. For example, a positive skid increases the chances of sticking and tail-lifting on low bondability substrate, but it decreases the tail pull force and increases the tail pull force for high bondability substrate. This indicates that finding a general experimental rule for understanding the effect of process parameters on the stitch bond quality is difficult if not impossible. In other words, instead of general rule, it is more likely to find individual rules for specific individual applications. To improve the understanding of stitch bonding a three dimensional (3D) dynamic explicit FE model is developed in ABAQUS. The model components and boundary conditions are constructed and applied to reflect the experimental conditions. The bonding force, scrub, and skid are successfully implemented into the model. Mass scaling is applied carefully to save calculation time while ensuring there are no artificial effects of inertia. The model is able to render the conventional responses reported in the past including stress and strain distributions. However, these conventional outputs were not sufficient to provide a correlation between model and experiment. Therefore, new candidate responses were developed and extracted from the numerical results. The new responses are based on accepted welding mechanisms. One of the mechanisms is interfacial cleaning by frictional energy which is beneficial for bonding. Thus the friction energy accumulated during the simulated bond duration is extracted as a candidate response. For classical cold welding processes, the interfacial surface expansion is a key mechanism, as it opens up cracks in the surface contamination and oxide layers and thereby generates paths to bring the fresh metals together under pressure. Therefore, candidate responses related to surface expansion at the contact interface are extracted from the model. The complete set of new responses extracted from the numerical model includes contact areas, surface expansion per areas, frictional energy, and combination of frictional energy combined with surface expansions per areas. In addition the bond interface is divided into ???wedge??? and ???tail??? regions. The model is run for the same DOE cells as used in the first set of experiments and candidate responses are extracted and compared with the experimental observations. By ranking the correlation coefficients of each individual candidate responses, for the first time correlations that are relatively strong are found between a numerical response and experimental observations of stitch bonding. Responses that have correlation coefficients of 0.79 and 0.85 were found for wedge sticking and tail-lifting, respectively. Such relatively strong correlation indicates that the friction enhanced cleaning and the surface expansion mechanisms are proper theories for the current stitch bonding system. These theories can be used for developing similar models for other types of the solid-state bonding processes. Based on the best candidate responses, a procedure to determine numerical process windows is demonstrated for a specific application. Such a window defines the parameter ranges which result in an acceptable stitch bonding process and is an excellent indication of how suitable a process is for mass production. Depending on the application, materials, geometries, and tools, the FE model and process window procedure allow a variety of numerical process windows to be produced and compared.

A background of concentrated solar power, and finite element analysis are provided, along with further technical details on the physics of parabolic light concentration and classical plate theory. The concept of optical efficiency is outlined, including the 5 contributing factors: the cosine effect, mirror reflectivity, blocking and shadowing, atmospheric attenuation, and surface irregularities. Surface irregularities are identified as the least predictable factor of optical efficiency, making them the subject of the experimental section. Physical and computational experimentation is conducted to determine a desirable selection for material of reflector substrate, thickness of reflector substrate, holding method of reflector, and aspect ratio of reflector. Physical and computational results are compared with one another to add validity to both sets of results. Recommendations are made for each design criteria selection, however it is found that in many cases the selection of reflector properties falls to an economic decision.

The objective of this research was to better understand how impact angle influences headform dynamic response and brain tissue deformation. A bare headform was impacted using a pneumatic linear impactor at 5.5 m/s. The impacts were directed on the front and side location at angles of 0, 5, 10 and 15° rightward rotations as well as -5, -10 and -15° (leftward) rotations at the side to examine the characteristics of the head and neckform on the results. Peak resultant linear and rotational accelerations from the headform as well as peak maximum principal strain (MPS) and von Mises stress (VMS) estimated from a brain finite element model were used to measure the effect of impact angle. Significant results were dependent upon the impact angle and location as well as the dependent variable used for comparison (p <0.05). Impact angle produced significant differences in rotational acceleration and MPS at both the front and side; however angle only had an effect on VMS and linear acceleration at the front and side locations, respectively. These findings show that the effect of impact angle is asymmetrical and is specific to the dependent variable. This study suggests that varying impact angle alone may not be as influential on headform dynamic response and brain tissue deformation and that the severity of an impact may be more of a function of how both location and angle create high risk conditions.