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The thesis work investigates the possibility of replacing the Body-In-White (BIW) sections used in a physical test with a fixture. Volvo-cars perform several sub-system tests on its car components taken from various car models for different issues. Squeak and Rattle in Cockpits is one such important phenomenon investigated through its sub-system tests. Currently, the Body-in-White (BIW) sections taken from car body are used in holding the cockpits for Squeak and Rattle physical testing on a vibrating rig, the idea is to design a fixture that can replace these BIW sections for the test. Additionally, it is ensured that the fixture is designed to accommodate a variety of cockpits through the flexibility in its structure. Models from two different car segments were considered for performing the thesis. The development process started by researching the theory behind squeak and rattle along with investigating the important design parameters which would determine the requirements on the fixture. This is followed up with benchmarking the parameters and a physical test which would help later in comparison and evaluation of fixture performance against the BIW. The result from benchmarking were then used for topology optimization in obtaining a material layout to provide a basis for fixture design. Then, a basic CAD model is generated which is adapted to provide flexibility using Aluflexmechanisms. The final design comprises of a sufficiently rigid main structure made of hollow steel beams upon which Aluflex mechanisms are attached to provide flexibility in accommodating a variety of cockpit models. The fixture is analyzed and evaluated by comparing with benchmarked data. With the thesis, a fixture with generic (flexible) features which is manufacturable has been designed. It was concluded that at its current stage it cannot completely replace the BIW since the fixture is performing better than BIW in some respects and failing to conform to the requirements in others. The possible reason for the fixture failing to meet the requirements in the few aspects has been explored. As future work, it was proposed to explore into stiffness varying mechanisms (spring mechanisms) that could alter the stiffness requirements on the fixture as per the cockpit used for testing. It was also suggested to look for alternatives to Aluflex which would provide better stiffness at the connection points. Further, it was suggested to look for alternatives in the design concept which would avoid the connection part in extending too much away from the main structure thereby retaining high stiffness at the connection point.

Dams are vital infrastructure for society as they provide various services (e.g., flood prevention, storage of byproducts from mining operations, water storage for irrigation and hydropower generation) by the impoundment of liquids. However, the storage of considerable volumes of liquids introduces a risk of uncontrolled discharge, due to dam failure, which could result in catastrophic outcomes. Consequently, the safety must be ensured throughout a dam’s service life and thus regular assessments are required. For concrete dams, the current practices of stability assessment methods found in guidelines and regulatory rules require idealizations. This need for idealization is a weakness of current assessment methods as elucidated by the appended scientific articles. The essence of the results of the appended articles demonstrates that certain parameters and features of a dam, which are commonly neglected in current dam assessment, significantly influences the load capacity of a dam. Therefore, this study primarily deals with alternative assessment methods that can be used for dams. Therefore, as an outcome of an extensive literature review on probabilistic analysis and scale model testing, summarized in the chapters of the thesis, a framework for concrete dam assessment is proposed. Even though the methods can be individually employed to assess the stability and safety of a dam, an approach that integrates the strengths of each method is currently not available. The proposed framework is novel and combines scale model testing, finite element analysis, probabilistic analysis and is intended to resolve issues identified with current assessment methods. The framework integrates the strengths of each method provides a robust assessment strategy where cross-validation of the failure mode and capacity is achieved by utilizing both finite element analysis and scale model testing. Furthermore, in contrast to current dam assessment methods, it allows for large geometrical variations in the rock-concrete interface to be included in the analysis, which contributes significantly to the capacity of a concrete dam as elucidated by the appended articles. The work in this thesis presents the theoretical foundation of the framework. It is intended to be applied in a future case study to evaluate its performance on an existing buttress dam.

Cardiovascular diseases, including heart failure, are a global health concern, necessitating advancements in non-invasive diagnostic tools and treatments. Computational modeling offers an invaluable approach to simulate and understand the intricacies of cardiac flow dynamics. This study aims to identify critical blood flow properties in the left atrium, a crucial component of the heart responsible for receiving oxygenated blood from the lungs and pumping it into the left ventricle. Building on previous work, this project implemented an idealized model of the left atrium using Finite Element Method (FEM) and simulated various properties related to its geometry, revealing crucial aspects of fluid dynamics. Specifically, analysis revealed a U-shaped inflow profile, pressure variations due to flow jets and presence of vortices, asymmetrical outflow due to differences in pulmonary vein geometry, and the presence of longitudinal vortex structures within the atrium. These properties can provide valuable insights about the blood flow in a healthy heart. This research presents a foundation for future work aiming to integrate models of the left ventricle and left atrium, offering a more comprehensive understanding of the left heart's functionality and potential pathologies. Further studies should focus on in-depth analysis, extension and validation of these properties using real patient data to enhance their diagnostic potential.

The objective of this work is to develop an evolution equation for the ductile growth of a spherical void in a highly strain rate and temperature dependent material. The material considered in this work is stainless steel 304L at 982 °C. The material is characterized by a physically-based internal state variable model derived within consistent kinematics and thermodynamics — Evolving Microstructure Model for Inelasticity. Through this formulation, the degradation of the elastic moduli due to damage has been naturally acquired. An elastoviscoplasticity user material subroutine has also been developed and implemented into a commercially available finite element software ABAQUS. The subroutine utilizes a return mapping algorithm, where a purely elastic trial state (elastic predictor) is followed by a plastic corrector phase (return mapping). A conditionally stable fully-implicit scheme, derived from the backward Euler integration method, has been employed to calculate the values of the internal state variables in the elastoviscoplasticity integration routine. A repeating unit cell problem is set up by introducing a spherical void inside a matrix material that simulates a periodic array of voids in a component. Using finite element analysis, a database is generated by recording the responses of the unit cell under various combinations of loading conditions, porosity, and state variables. Functional forms of the void growth equations are constructed by utilizing normalization techniques to collapse all the data into master curves. The evolution equations are converted to a form consistent with the continuum damage variable in the complete thermal-elastic-plastic-damage version of the physically-based internal state variable model.

Mechanical structure-property relations have been quantified for AISI 4140 steel under different strain rates and temperatures. The structure-property relations were used to calibrate a microstructure-based internal state variable plasticity-damage model for monotonic tension, compression and torsion plasticity, as well as damage evolution. Strong stress state and temperature dependences were observed for the AISI 4140 steel. Tension tests on three different notched Bridgman specimens were undertaken to study the damage-triaxiality dependence for model validation purposes. Fracture surface analysis was performed using Scanning Electron Microscopy (SEM) to quantify the void nucleation and void sizes in the different specimens. The stress-strain behavior exhibited a fairly large applied stress state (tension, compression dependence, and torsion), a moderate temperature dependence, and a relatively small strain rate dependence.

Rutting failures are prominent in expedient airfields constructed with AM2 landing mats over soft existing subgrades. There are many issues that must be addressed when approaching this multiaceted problem. The load transfer mechanism occurring at interlocking mat joints and the mat-soil interface bonding condition affect near surface subgrade response. The repeated loading coupled with lateral aircraft wander causes significant principal stress rotation in the subgrade. This kneading action then causes variations in the excess pore-water pressure and a subsequent softening of the soil. The purpose of this study is to investigate the critical factors that lead to subgrade rutting failures in landing mats constructed over soft subgrades. A three dimensional finite element (3D FE) model of a landing mat system over soft subgrade is implemented under both static and pseudo-dynamic loading conditions with aircraft wander. To capture the complex stress histories induced by the simulated moving gear loads over the unique structural features of the AM2 mat system, an elastoplastic kinematic hardening constitutive model, the Multi-Mechanical Model, is developed, calibrated and used to represent the subgrade response. Under both static and pseudo-dynamic loading, the FE model results match very well with the stress and deformation results from full-scale instrumented testing of the AM2 mat over 6 CBR subgrade. Results show that incorporating the load transfer mechanism occurring at the mat joints and varying the mat-soil interface condition affect the near surface subgrade deformation and stress responses that contribute to rutting failures. Furthermore, rotation of the principal stress axes and changes in excess pore-water pressures occur in the subgrade because of the moving tire load. These phenomena contribute to extension of the field of deformation influence around the trafficked area in the subgrade and upheaval at the edges of the test section. Findings of this study show that although layered elastic analysis procedures are the basis of current airfield design methodologies, critical design features and the corresponding deformation responses can be better modeled using the FE approach. Furthermore, the proposed 3D modeling approach implementing aircraft wander can provide a reliable platform for accurately simulating the subgrade response under pseudo-dynamic loading conditions.

In this study, the teeth of the Carcharodon carcharias (Great White) and the Galeocerdo cuvier (Tiger) sharks were analyzed to examine their optimized structure-property relationships and edge serrations with regards to shearing. Structure-property analysis was conducted using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy, X-ray diffraction, and optical microscopy to study the teeth using parametric optimization. Quantifying the structural properties also focused on the tooth serrations, which were captured in SEM and micrographs and were analyzed for geometric parameters using ImageJ software. Nanoindentation was performed to determine the material's mechanical properties. Further, finite element analysis (FEA) of the sharks' teeth serrations were carried out to quantify the optimum shearing performance of each serration type – zeroth (no serrations), first (a single array of serrations), and second (a secondary array of serrations upon the first array) order serration. Here, serration order, bite velocity, and angle-of-impact for ascertaining sharks' teeth shearing performance were analyzed. FEA results showed that serrated edges reduced the energy required to pierce and shear materials as the angle of penetration moved away from perpendicular to the surface. These bioinspired findings will help advance the design and optimization of engineered cutting tools.

This thesis presents the development and implementation of a generalized optimization framework for use in sheet-stamping process simulation by finite element analysis. The generic framework consists of three main elements: a process simulation program, an optimization code, and a response filtering program. These elements can be filled by any combination of applicable software packages. Example sheet-stamping process simulations are presented to demonstrate the usage of the framework in various forming scenarios. Each of the example simulations is presented with a sensitivity analysis. These examples include analysis of a 2-dimensional single-stage forming, a 2-dimensional multi-stage forming, and two different 3-dimensional single-stage forming processes. A forming limit diagram is used to define failure in the 3-dimensional process simulations. Optimization results are presented using damage minimization, thinning minimization, and springback minimization with aluminum alloy 6061-T6 blanks.

A study has been conducted to compare conventional pavements and perpetual pavements with a particular emphasis on perpetual pavements. One of the main drawbacks of conventional pavements and motivations for this work is the maintenance required for hot mix asphalt (HMA) pavements with sub-drainage systems. Perpetual pavements, as the name suggests, are designed with a long life. However, this is a relatively new concept and there are still many unknowns concerning their performance. This dissertation was written to answer some of the questions. The study examines structural response and performance of perpetual pavements. Also, deterioration and performance of perpetual pavements will be contrasted to conventional pavements. Empirical data from the National Center of Asphalt Technology (NCAT) Test Track study was obtained, analyzed and used as a basis for evaluating theoretical models. Computational models for both conventional and perpetual pavements were constructed and analyzed using the general purpose finite element analysis software ABAQUS. Geometry, materials and loading are modeled with sufficient accuracy. This research examined several types of responses of perpetual pavements. It extends the traditional criteria of pavement distress by suggesting that longitudinal strain at the surface of a pavement HMA layer as an important criterion. Shear strain was studied and it provides a reasonable explanation of some distresses in pavements. By studying the FEA results from conventional and perpetual pavements and a thorough investigation of the thickness effects, it provides some rationale on why strain at the top of thick pavements is critical. The effects of dynamic wheel loadings are presented. Finally, the effect of environment, specifically temperature and moisture, on perpetual pavements are studied.