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To evaluate the impact of reduced truck tire pressure on strain response of low volume spring-restricted roads, research was conducted on two instrumented pavement sections in Manitoba, Canada. Tire pressure control systems tests were carried out at the sections in spring and fall 2009. Measured maximum tensile strain at the bottom of asphalt layer decreased by 15-20% when tire pressure was reduced by 50%. Measured strain at the bottom of asphalt layer in fall is about 50% less than in spring. The effects of gauge orientation, truck speed, and tire offset from the strain gauge were also analyzed. A finite element model with static load was developed and verified. The bearing capacity is lower in spring than in normal condition for flexible pavements subject to deep frost action. Reduced tire pressure is effective to reduce bottom up failure of the pavement, and is less effective to prevent rutting.

In this thesis, a two-dimensional (2D) finite element (FE) model was developed from the patient’s hip DXA image to evaluate osteoporotic fracture risk. The loading configuration was designed to simulate a lateral fall onto the greater trochanter. Bone inhomogeneous mechanical properties (e.g. Young’s modulus) assigned to the FE model were correlated to bone mineral density captured in DXA image using empirical functions. In-house MATLAB codes were developed to investigate the effects of different factors such as bone mineral density, femoral neck length, neck diameter, neck angle and patient’s body weight on fracture risk. The 2D FE model constructed from DXA image was able to de-termine the factors which affect fracture risk to a greater extent based on the location of femur. The model developed here can be considered as a first attempt for investigating the effects of different parameters on fracture risk using patient specific 2D FE method.

Laser forming is an innovative technique that uses a defocused laser beam to form sheet metal by thermal stresses rather than external forces. Promising potential applications of laser forming include rapid prototyping, straightening, aligning and adjusting of macro/micro-metallic components. Research to-date on laser forming has been largely focused, theoretically and experimentally, on the problem of characterization of process parameters on the forming results, and computational simulations of laser forming remain limited only providing the insight into the process. This study investigates the laser forming processes using the finite element analysis with respect to material responses during the processes, including complex processes, process optimization, process reliability and the effects of thermal and mechanical material properties. The first part of this thesis describes a nonlinear transient three-dimensional heat transfer finite element model and a rate dependent three-dimensional deformation model, which are developed for the laser forming simulations. Simulations are performed using an indirect coupled thermal-structural method for the processes of a straight-line heating, a circle-line heating, and a laser micro-adjustment. The thermo-mechanical behaviours during the straight-line heating process are presented in terms of temperature, stress and strain, and displacement distributions. The emphasis in the circle-line heating simulations is placed on the characterization of the quality of the deformed geometry by obtaining the radial and circumferential waviness. The micron size movements induced by laser point heating are focused the simulations of the micro-adjustment process. Simulation results are validated by comparison with published data or correlation to engineering point of view. The second part of this thesis presents the development of an effective method to determine optimum process parameters in laser forming. For the process optimization, design optimisation techniques are introduced into the finite element analysis of the laser forming process. The optimum parameter values to produce a predefined bend angle of 3° in the straight-line heating process are sought by two optimization procedures - one is the procedure involving the non-gradient method and the other is the gradient-based method. Optimum values of laser power, feed rate, beam diameter and number of passes are determined to produce a predefined bend angle in a multiple straight-line heating process using the two optimization procedures. A more suitable optimisation method for laser forming is chosen, which is used for a new optimisation problem to generate a maximum bend angle in a single pass of laser forming. In the third part of this thesis, a strategy to assess the reliability of the laser forming process is established by employing a well-known reliability analysis method, the Monte Carlo simulation. Robustness of the straight-line heating process of producing 3° with the optimum parameters determined by process optimization is evaluated with regard to the uncertain input variables of laser power, feed rate, plate thickness and coefficient of thermal expansion via the Monte Carlo simulations based on the finite element simulations of the process. The final part of this thesis identifies the effects of material properties on the bend angle resulting from laser forming. Process sensitivity to the properties of coefficient of thermal expansion, thermal conductivity, specific heat capacity and elastic modulus is investigated by measuring the Pearson product-moment correlation coefficient between the properties and the bend angle, which are based on the Monte Carlo simulations of laser forming. The conclusion is that the developed finite element models contribute to a better understanding of the laser forming process, and the optimization procedure is able to be used for straightening, aligning and adjusting of components.

This thesis first describes the reverse method of transformer design. An existing magnetic model for full-core shell-type transformers, based on circuit theory, is summarised. A magneto-static finite element model is introduced and two sample transformers are analysed. The magnetic model based on finite element analysis is shown to be more accurate than the model based on circuit theory. Partial-core resonant transformers are then introduced and their characteristics are explained using an equivalent circuit model. A method of measuring the winding inductances under resonant operation is developed and used to investigate the characteristics of two different tuning methods. A finite element model of the partial-core resonant transformer is developed by adopting the model for full-core shell-type transformers. The model results accurately match the measured inductance variation characteristics of three sample transformers and predict the onset of core saturation in both axial-offset and centre-gap arrangements. A new design of partial-core resonant transformer is arrived at, having an alternative core and winding layout, as well as multiple winding taps. The finite element model is extended to accommodate the new design and a framework of analysis tools is developed. A general design methodology for partial-core resonant transformers with fixed inductance is developed. A multiple design method is applied to obtain an optimal design for a given set of specifications and restrictions. The design methodology is then extended to devices with variable inductance. Three design examples of partial-core resonant transformers with variable inductance are presented. In the first two design examples, existing devices are replaced. The new transformer designs are significantly lighter and the saturation effects are removed. The third design example is a kitset for high-voltage testing, with the capability to test any hydro-generator stator in New Zealand. The kitset is built and tested in the laboratory, demonstrating design capability. Other significant test results, for which no models have yet been developed, are also presented. Heating effects in the core are reduced by adopting an alternative core construction method, where the laminations are stacked radially, rather than in the usual parallel direction. The new kitset is yet to be used in the field.

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.