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.

The finite element method (FEM) is commonly used to design the reinforcement in concrete slabs. In order to simplify the analysis and to be able to utilize the superposition principle for evaluating the effect of load combinations, a linear analysis is generally adopted although concrete slabs normally have a pronounced non-linear response. This type of simplification in the modeling procedure will generally lead to unrealistic concentrations of cross-sectional moments and shear forces. Concrete cracks already at service loads, which leads to redistribution of moments and forces. The moment- and force-peaks, obtained through linear finite element analysis, can be redistributed to achieve a distribution more similar to what is seen in reality. The topic of redistribution is however poorly documented and design codes, such as the Eurocode for concrete structures, do not give descriptions of how to perform this in practice. In 2012, guidelines for finite element analysis for the design of reinforced concrete slabs were published in a joint effort between KTH Royal Institute of Technology, Chalmers University of Technology and ELU consulting engineers, which was financially supported by the Swedish Transport Administration. These guidelines aim to include the non-linear response of reinforced concrete into a linear analysis. In this thesis, the guidelines mentioned above are followed to obtain reinforcement plans based on crack control, for a fictitious case study bridge by means of a 3D finite element model. New models were then constructed for non-linear analyses, where the reinforcement plans were implemented into the models by means of both shell elements as well as a mixture of shell and solid elements. The results from the non-linear analyses have been compared to the assumptions given in the guidelines. The results from the non-linear analyses indicate that the recommendations given in the aforementioned guidelines are indeed reasonable when considering crack width control. The shell models yield crack widths equal to approximately half the design value. The solid models, however, yielded cracks widths that were 15 - 20$\%$ lower than the design value. The results show that many factors attribute to the structural behavior during cracking, most noticeably the fracture energy, a parameter not featured in the Eurocode for concrete structures. Some limitations of the models used in this thesis are mentioned as well as areas for further improvement.

The overall goal of this work is to predict the mechanical response of an as-built Ti-6Al-4V directed energy deposition component by a dislocation mechanics-based internal state variable model based on the component's geometry and processing parameters. Previous research has been performed to connect additive manufacturing (AM) process parameters including laser power and scanning strategy to different aspects of part quality, such as porosity, mechanical properties, fatigue life, microstructure, residual stresses, and distortion. The lack of predictive capabilities to fully estimate residual stresses and distortion within parts produced via AM have hindered part qualification; however, modeling the AM process can aide in process and geometry optimization compared to traditional trial-and-error methods. The presence of unwanted thermally induced residual stresses and distortion can lead to tolerancing issues, reduced fatigue life, and decreased mechanical performance compared to similar components fabricated with traditional manufacturing methods such as casting and machining. A three-dimensional thermomechanical finite element model calibrated using dual-wave pyrometer thermal image datasets along with temperature- and strain rate-dependent mechanical data is utilized for this work. The purpose of this work is to understand the relationship between a component's temperature history and its resultant distortion and residual stresses.