The Caribbean and Central America region (CCAR) undergoes the entire spectrum of earthquake types due to its complex tectonic setting comprised of transform zones, young oceanic spreading ridges, and subduction along its eastern and western boundaries. CCAR is, therefore, an ideal setting in which to study the impacts of long-term tectonic deformation on the distribution of present-day seismic activity. In this work, we develop a revised continuous tectonic strain rate model based on interseismic, secular geodetic data. We compare it with its predecessor, the Global Strain Rate Model v2.1 (GSRM). Specifically, we compare predicted fault types with known active faults and evaluate the style of predicted fault types with present-day earthquake focal mechanism data. We first create a 0.25$^{circ}$ x 0.25$^{circ}$ finite element grid that is comprised of block geometries defined from previous studies. Second, we isolate and remove anomalous signals that are inconsistent with rigid block motion from the latest open access community Global Navigation Satellite System (GNSS) velocity solution from UNAVCO and combine it with GNSS data compiled for the GSRM. In a third step, we delineate zones of deformation and rigidity by creating a buffer around the boundary of each block that varies depending on the size of the block and the expected deformation zone, which are based on locations of GNSS data consistent with rigid block motion. Fourth, we assign the regions within the buffer of zero for the deforming areas and a plate index outside the buffer to constrain plate rigidity. Finally, we calculate a tectonic strain rate and continuous velocity model for CCAR using the Haines and Holt finite element approach to fit bicubic Bessel splines to the GNSS data assuming block rotation for zones of rigidity. Our model of the CCAR is consistent with compression along subduction zones, extension across the East Pacific Rise, and a combination of compression and extension across the North America - Caribbean plate boundary with a few exceptions due to limitations with the modeling approach. Modeling results are then used to calculate expected faulting behaviors that we compare with seismic activity, the GSRM, and mapped geologic faults. We find the accumulation of strain rates in areas near the Middle American Trench, Hispaniola, the northeastern Caribbean, and northern South America indicate tectonic deformation that may result in seismic events. We conclude the tectonic deformation plays a critical role in explaining present-day seismicity along land masses adjacent to the subduction zone and the Hispaniola block. / Master of Science / Central America and the Caribbean are areas with high occurrences of earthquakes. This is due to the various types of tectonic plate boundaries that occur in the region. When plates move in relation to each other, they can accumulate strain, which plays a role in the size and type of earthquakes that occur. In this work, we aim to determine the effects on strain on earthquakes. To do this, we utilize an inversion method to calculate strain rates from Global Navigation Satellite System (GNSS) data. In our model, we first create a grid of points and a geometry of the regional tectonic blocks. We then gather data from public and published sources. The model also requires that we define where the plates are allowed to deform (accumulate strain) and where they remain rigid. Using the Haines and Holt method, we invert the GNSS velocities for strain rates and velocities. We find long-term tectonic deformation dominates the present-day seismic activity in three key regions: along the Middle America Trench and across the Hispaniola block.

Robert Agnew proposed a new version of strain theory in 1992. In this article, Agnew argued that strain is not only a result of the blocked opportunity to achieve goals as Merton had argued, but that strain also results from the removal of positively valued stimuli and the presence of negative stimuli. With such a theory, criminologist had focused on how this may explain juvenile delinquency. Yet very little attention was given to how this may affect adult criminality as well. Similarly, Hirschi (1969) presented social control theory as a means of describing the causes of juvenile delinquency. While these theories have been repeatedly tested and supported with respect to delinquency, they have rarely been used to describe adult criminality. This paper intends to compare the utility of Agnew's general strain theory and Hirschi's control theory in explaining the criminal behavior of fathers. For general strain theory, it is predicted that fathers who have either high contact and low relationship quality or who have low contact and high relationship quality will have significantly higher criminal activity than those who have high contact and relationship quality or low contact and relationship quality. Conversely, social control theory predicts that fathers who have low relationship qualities with their children are more likely to commit criminal acts. This paper aims to ascertain which of these hypotheses is more accurate. / Master of Science

Sensor-embedded tires, known as intelligent tires, have been widely studied because they are believed to provide reliable and crucial information on tire-road contact characteristics e.g., slip, forces and deformation of tires. Vehicle control systems such as ABS and VSP (Vehicle Stability Program) can be enhanced by leveraging this information since control algorithms can be updated based on directly measured parameters from intelligent tire rather than estimated parameters based on complex vehicle dynamics and on-board sensor measurements. Moreover, it is also expected that intelligent tires can be utilized for the purpose of the analysis of tire characteristics, taking into consideration that the measurements from the sensors inside the tire would contain considerable information on tire behavior in the real driving scenarios. In this study, estimation methods for the tire-road contact features by utilizing intelligent tires are investigated. Also, it was discussed how to identify key tire parameters based on the fusion technology of intelligent tire and tire modeling. To achieve goals, extensive literature reviews on the estimation methods using the intelligent tire system was conducted at first. Strain-based intelligent tires were introduced and tested in the laboratory for this research. Based on the literature review and test results, estimation methods for diverse tire-road contact characteristics such as slippages and contact forces have been proposed. These estimation methods can be grouped into two categories: statistical regressions and model based methods. For statistical regressions, synthetic regressors were proposed for the estimation of contact parameters such as contact lengths, rough contact shapes, test loads and slip angles. In the model-based method, the brush type tire model was incorporated into the estimation process to predict lateral forces. Estimated parameters using suggested methods agreed well with measured values in the laboratory environment. By utilizing sensor measurements from intelligent tires, the tire physical characteristics related to in-plane dynamics of the tire, such as stiffness of the belt and sidewall, contact pressure distribution and internal damping, were identified based on the combination of strain measurements and a flexible ring tire model. The radial deformation of the tread band was directly obtained from strain measurements based on the strain-deformation relationship. Tire parameters were identified by fitting the radial deformations from the flexible ring model to those derived from strain measurements. This approach removed the complex and repeated procedure to satisfy the contact3 constraints between the tread and the road surface in the traditional ring model. For tires with different specifications, identification using the suggested method was conducted and their results are compared with results from conventional methods and tests, which shows good agreements. This approach is available for the tire standing still or rolling at low speeds. For tires rolling at high speeds, advanced tire model was implemented and associated with strain measurements to estimate dynamic stiffness, internal damping effects as well as dynamic pressure distributions. Strains were measured for a specific tire under various test conditions to be used in suggested identification methods. After estimating key tire parameters step by step, dynamic pressure distributions was finally estimated and used to update the estimation algorithm for lateral forces. This updated estimation method predicted lateral forces more accurately than the conventional method. Overall, this research will serve as a stepping stone for developing a new generation of intelligent tire capable of monitoring physical tire characteristics as well as providing parameters for enhanced vehicle controls. / PHD / Tires are very crucial components in a vehicle because they are only objects in contact with the road surface on which the vehicle drive. They support the weight of the vehicle and generate forces which make the vehicle drive, stop and turn. Thus, the improvement of vehicle performances such as handling, ride quality and braking can be achieved by understanding and by optimizing tire properties as well as improving the design of the vehicle itself. These days, diverse vehicle control systems such as anti-lock braking and cornering stability control systems have been widely adopted to improve the stability of the vehicle when it is braked or turned. These stability controls usually require information about slippages and forces occurring between the tire and the road surface. These quantities can be indirectly estimated by monitoring vehicle motions, which are measured by sensors installed on the vehicle frame. Although these traditional methods have worked successively, the control algorithms can be improved further by directly sensing the tire behaviors using sensors embedded in the tire. These sensor-embedded tires are often called as ‘intelligent tire’ because tires themselves serve as the monitoring device on driving conditions as well as conduct traditional functions. Also, the measured quantities inside the tire can be effectively used to understand tire characteristics because they have valuable information on tires, especially, mechanism how the tire deforms and generate contact forces when it rolls over the road surface. In this research, strains are measured at the inner surface of the tire during it rolling and cornering on the flat road surface under different loads on the indoor test rig. A strain represents the relative displacement between particles. Based on experimental results, estimation algorithms for test loads, contact lengths, cornering angles and cornering forces are developed. These estimation methods can be incorporated in the vehicle control algorithm in the real driving scenario for improved vehicle controls. A tire is a complex system comprising various composite materials, so their behaviors or characteristics show sever non-linearity which difficult to understand. They have been simplified and modeled in a various way based on diverse physical principles to understand how they are deflected and generate forces and moments during rolling on the road surface under a vertical load. These models are called ‘physical tire model’. To extract and analyze tire physical characteristics, measured strains at the inner surface are combined with these tire models. In this research, tires are modeled as a flexible ring which is supported by viscoelastic materials and this tire model called as a ‘flexible ring model’ which have been utilized to analyze vibration properties and contact phenomena of tires. Strain measurements were fed into the model and crucial tire characteristics are extracted such as tire stiffness, pressure distributions and internal damping. These properties can be used to analyze the tire performance like wear, rolling resistance, ride qualities and the capacity of cornering forces. Since intelligent tire systems are applied for the real driving situation, tire characteristics extracted in this way would have closer links to vehicle performances rather than those measured in the laboratory. Overall, this research will serve as a stepping stone for developing a new generation of intelligent tire capable of monitoring physical tire characteristics as well as providing parameters for enhanced vehicle controls.

The liver is one of the most frequently injured abdominal organs in motor vehicle collisions. Although previous studies have quantified the tensile failure properties of human liver parenchyma at 48hrs postmortem, it is currently unknown how the material properties change between time of death and 48hrs postmortem. Therefore, the purpose of this study was to quantify the effects of postmortem degradation on the tensile material properties of bovine liver parenchyma when stored in DMEM or saline. Fourteen fresh bovine livers were obtained from a local slaughter house and stored in either DMEM or saline as large blocks, small blocks, or slices of tissue. Multiple parenchyma dog-bone samples from each liver were tested once to failure at three time points: ~6hrs, ~24hrs, and ~48hrs postmortem. The data were then analyzed to determine if there were significant changes in the material properties with respect to postmortem time. The results showed that the failure strain decreased significantly between 6hrs and 48hrs after death when stored as large blocks in saline. Conversely, neither the failure stress nor failure strain changed significantly with respect to postmortem time when stored as large blocks in DMEM. The modulus did not significantly change for tissue stored as large blocks in either fluid. Preliminary results indicated that reducing the tissue storage size had a negative effect on the material properties and cellular architecture. Overall, this study illustrated that the effects of postmortem liver degradation varied with respect to the preservation fluid, storage time, and storage block size. / MS / Although the liver is one of the most frequently injured abdominal organs in motor vehicle collisions (MVCs), currently accepted anthropomorphic test devices are unable to predict abdominal organ injury risk. Consequently, finite element models are becoming an important tool for assessing abdominal organ injury risk in MVCs. However, these models must be validated based on biomechanical data in order to accurately assess injury risk. Given that previous studies that have quantified the tensile failure properties of human liver parenchyma have been limited to testing at 48hrs postmortem, it is currently unknown how the material properties change between time of death and 48hrs postmortem. Therefore, the purpose of this study was to quantify the effects of postmortem degradation on the tensile material properties of bovine liver parenchyma with increasing postmortem time when stored in DMEM or saline. A total of 148 uniaxial tension tests were successfully conducted on parenchyma samples of fourteen bovine livers acquired immediately after death. Tissue was immersed in DMEM or saline and kept cool during preparation and storage. Twelve livers were stored as large blocks of tissue, while two livers were stored as small blocks and slices. Multiple dog-bone samples from each liver were tested once to failure at three time points: ~6hrs, ~24hrs, and ~48hrs after death. The data were then analyzed using a Linear Mixed Effect Model to determine if there were significant changes in the failure stress, failure strain, and modulus with respect to postmortem time. The results of the current study showed that the failure strain of bovine liver parenchyma decreased significantly between 6hrs and 48hrs after death when stored as large blocks in saline and refrigerated. Conversely, neither the failure stress nor failure strain changed significantly with respect to postmortem time when stored as large blocks in DMEM. The modulus did not significantly change for tissue stored as large blocks in either saline or DMEM. In addition, preliminary results indicated that reducing the tissue storage size had a negative effect on the material properties and cellular architecture. Overall, this study illustrated that the effects of postmortem liver degradation varied with respect to the preservation fluid, storage time, and storage block size.

Using data from the Chicago Homicide Dataset for years 1988-1992 and the Chicago Community Area Demographics, multiple regression and mediation analysis are used to examine various community level factors’ impact on Intimate Partner Homicide (IPH) rates per Chicago community area. The relationship between the percentage of non-white and IPH rate per Chicago community area is significant and positive, but disappears once economic strain is taken into account, as well as when family disruption is included in the model. There is a weak, but positive relationship between population density and IPH rates, but neither economic strain nor family disruption mediates the relationship between population density and IPH rates. Economic deprivation is positively related to IPH rates, but economic strain and family disruption partially mediate the relationship between economic deprivation and IPH rates. Finally, the relationship between the percentage of males aged 30-59 and IPH rates per community area in Chicago is moderately negative, but this relationship disappears once economic strain is accounted for in the model. However, family disruption does not mediate the relationship between the percentage of males aged 30-59 and IPH rates. These results indicate that some structural covariates impact IPH rates and that some relationships are mediated by economic strain and family disruption. These results also lend support to a modified approach to general strain theory (GST). More research is necessary to validate these results.

Background Running is a popular form of exercise that more than 55 million Americans actively participate. Endurance running like marathon and half- marathon is getting increasingly popular among active runners. Although the effect of running is considered beneficial to bone health, the direct relationship between strains and strain gradients occurred during long distance running and bone changes is still not clear. Especially, given a high rate of injury associated with the first-time marathon, understanding the direct effect of strain stimuli on bone health is an important issue. Based on the previous studies, we hypothesized that the higher values of strain will induce bone adaptation more effectively and will lead to higher bone osteogenic changes. Since osteocytes sense shear stress caused by the interstitial fluid flow, which is created by the deformations, and regulate activities of osteoblasts and osteoclast that govern bone adaptation, we also hypothesized that the local strain gradient will create pressure differences within the interstitial fluid network and will increase fluid flow. Furthermore, due to that increased fluid flow, the regions with the higher strain gradient will experience a higher amount of bone adaptation. Thus, in this study, our purpose was to define the effect of the strains and strain gradients on bone changes within distal tibia, which is the most prone anatomical site to low risk stress fracture, during training for first-time marathon. Methods High-resolution and low-resolution computed tomographic (CT) images of the distal tibia were obtained before and after a self-selected training from runners who were actively training to participate in their first-time marathon in the next calendar year. The low resolution scan covered a 69.864 mm length of the distal end of the tibia while the high resolution CT scan covered a 9.02 mm region of the distal tibia. Using low resolution CT image based subject specific finite element (FE) models, the strains and strain gradients of the distal tibia at the instance of the peak ground reaction force (GRF) were calculated. The baseline and follow-up high resolution CT scans were used in high resolution peripheral quantitative CT (HRpQCT) analysis and the estimation of bone changes over the training period. Finally, the effect of strains and strain gradients on the distal tibia bone changes was estimated based on the FE model driven strain values and HRpQCT analysis driven bone changes. We used a linear mixed model to define the relationship between strain values and bone changes in the distal tibia. Results The strain values that occurred during marathon training had significant effects on bone changes in the distal tibia. Particularly, the strain gradients showed a higher effect than the strains. In the cortical compartment, the strain gradients, which were calculated as a strain difference of a node from the surrounding nodes (Strain Gradient-1), affected the bone mineral density (BMD) negatively, and per 1000 µε increase resulted in 2.123% decrease in the cortical BMD. The strain gradients, which were calculated as a strain difference of a node from the surrounding nodes normalized to distance to surrounding nodes (Strain Gradient-2), presented a positive effect on the cortical bone volume with a slope of 4.335% / 1000 µε. In the trabecular compartment, the strain gradient-1 showed negative effects on the percent change in BMD and bone mineral density (BMC), whereas the strain gradient-2 showed positive effects on the percent change in BMD and BMC. Conclusion The linear mixed model analysis revealed a statistically significant (p < 0.05) relationship between strain gradients that occurred during running and distal tibia bone changes. The strains, biometrics, and initial parameters of bone did not show any significant effect on the bone changes. The connection between local strain environment and bone changes in the distal tibia investigated in this study is an important step to understand the mechanism of mechanically induced bone adaptation.

Introdução: O strain do átrio esquerdo (AE) permite uma análise quantitativa da função do AE. A relevância clínica desta medida é dependente da informação incremental à análise da função do ventrículo esquerdo (VE), particularmente importante em indivíduos portadores de insuficiência cardíaca (IC). O objetivo deste estudo foi avaliar o impacto prognóstico da disfunção atrial em pacientes com IC. Método: Ecocardiograma foi realizado em 217 pacientes em ritmo sinusal com IC e fração de ejeção (FE) do VE<40%. A análise do strain do AE foi avaliada por meio do speckle tracking, usando o QRS como referência. O seguimento foi realizado prospectivamente para avaliar a ocorrência de morte e transplante cardíaco (desfecho primário), além de infarto agudo do miocárdio (IAM), acidente vascular encefálico (AVE) e internação por IC. A associação do strain de reservatório, de conduto e de contração ativa com os desfechos foram avaliados por meio de análise univariada e multivariada de regressão de Cox. Resultados: Pacientes apresentaram idade média de 58±12 anos, sendo 62% homens e FE média de 29%±6. O tempo de seguimento médio foi de 2,8 anos. Os desfechos primário e secundário ocorreram em 18 e 54%, respectivamente. O strain de reservatório e de contração ativa estiveram relacionados com os desfechos primários, e o strain de reservatório e conduto estiveram relacionados com o desfecho secundário independentemente da idade, sexo, FE, classe funcional, regurgitação mitral ou grau de disfunção diastólica (p<0,05). Conclusão: O strain de reservatório do AE é um marcador independente de eventos adversos em pacientes portadores de IC e disfunção ventricular moderada e importante. Nossos achados sugerem que o strain do AE pode auxiliar na estratificação de risco de pacientes com IC. / Background: Left atrial (LA) strain imaging enables the quantitative assessment of LA function. The clinical relevance of these measurements is dependent on the provision of information incremental to the left ventricular (LV) evaluation, particulary important in heart failure (HF). The aim of this study was analyze the potential prognostic role of LA function in patients with HF. Methods: Echocardiography was undertaken in 217 patients with HF, left ventricular ejection fraction(EF)<40% and sinus rhythm. LA function was analyzed by speckle-tracking, using R-R gating. A prospective follow-up was conducted to report death and cardiac transplantation (primary endpoint), in addition to acute myocardial infarction, stroke and hospital admission (secondary endpoint). The association between LA reservoir, conduit and pump strain with adverse outcomes were assessed using univariate and multivariate Cox regression model. Results: Patients mean age 58±12 years, 62% men and mean EF 29±6%. Mean follow-up time was 2,8 years. The primary and secondary endpoints ocurred in 18 and 54%, respectively. LA reservoir and pump were associated with the primary endpoint, and LA reservoir and conduit were associated with secondary endpoint independently of age, sex, EF, functional class, mitral regurgitation or diastolic function (p<0,05). Conclusion: LA reservoir strain is an independent predictor of adverse events in pacients with moderate and severe HF. This finding suggests that LA strain can help as a marker in the risk stratification of patients with HF.

Cells regularly take on various types of force in the body. They have structures that are able to mediate, transfer and respond to the forces. A mutation in force regulating proteins such as lamin in the nucleus or the KASH domain which connects the nucleus to the cytoskeleton of the cell can cause catastrophic events to occur. The aims of this study were to better understand the response of the nucleus when structural proteins are mutated or are not present while under force. Progeria, a rare disease where an additional farnesyl group is attached to lamin was used in this study. Different types of forces were used to represent similar conditions in the body. Confinement of endothelial cell width showed an increase of surface defects. When restricting proteins such as actin was removed the nucleus appeared to rupture. This was shown to occur at a higher rate in the progeria groups. Endothelial cells under shear force showed high amount of nuclear rupture in progeria expressing group. prolonged exposure showed more rupture which eventually cased cell death and cells to come off the surface. Progeria expressing smooth muscle cells under cyclic stretch also showed similar results as endothelial cells. The amount and rate of deformation of the nucleus when the cytoskeleton is connected and not was looked at. When the connected the rate of deformation was higher. The high rate of nuclear defects and rupture while under force in progeria expressing cells shows that the nuclei have different structural properties and are weaker. It’s also been shown that the LINC complex contributes to nuclear deformation when stretching.

Heat stress is one of many physical agents to which thousands of workers are under constant exposure. Oftentimes it is necessary to work above the WBGT-based heat stress exposure limits. It is therefore important to consider alternative measures that include an exposure time limit to manage the heat stress. Predicted Heat Strain (PHS) (ISO7933) is one of those alternatives. PHS uses both personal factors like height and weight and job factors of environment, metabolic rate and clothing. The purpose of this project is to determine whether the PHS is an adequate method to predict short term exposure limits. The project’s data were taken from a prior experimental study where twelve participants were exposed to five different heat stress levels while over three different clothing ensembles. A total of 15 combinations of clothing and environment were tried. The PHS process was adapted to an Excel function using Visual Basic for Applications (VBA) (called fPHSTre). fPHSTre predicted a rectal temperature (Tre) at the exposure limit using both personal and job factors and then using standard values for personal factors. Based on analysis of variance, the fPHSTre adequately accounted for clothing, specifically evaporative resistance, using either fixed or individual data for predicted Tre on the experimental trials. In general, the PHS model could be used to reliably assess time limiting safe exposures in occupational settings for workers in hot environments.

En raison de l'augmentation de la demande d’allègement pour les véhicules automobiles, des solutions doivent être créées pour permettre aux constructeurs automobiles de passer d'aciers hautement formables mais lourds à des alliages d'aluminium moins formables mais plus légers pour les carrosseries en blanc. Les alliages d'aluminium de la série 6xxx, basés sur le système Al-Mg-Si-Cu, se sont révélés prometteurs en termes de résistance mécanique et de résistance à la corrosion, mais, l'une de leurs principales limitations concerne leur formabilité. Cette thèse vise à comprendre l'effet des additions de Si, Mg et Cu sur les propriétés mécaniques et de formabilité de la série AA6xxx. La calorimétrie différentielle à balayage et les essais de dureté sont utilisés pour identifier les effets de l'addition de solutés sur la microstructure d’amas de solutés après vieillissement naturel et pré-vieillissement. Les essais de traction donnent accès aux principales propriétés mécaniques : limite d'élasticité, résistance à la traction, taux d’écrouissage et allongement uniforme. Le test de sensibilité à la vitesse de déformation est effectué à l'aide de sauts de vitesse afin d'obtenir non seulement la sensibilité à la vitesse ascendante, mais moins classiquement la sensibilité à la vitesse descendante. Enfin, à l'aide d'équations constitutives, les propriétés mécaniques sont utilisées dans une modélisation par éléments finis pour saisir l'évolution de la déformation et de la vitesse de déformation dans la transition de la striction diffuse à localisée. Dans le cas du vieillissement naturel d'un mois (NA1m), deux types d'amas ont été détectés, une espèce moins stable thermiquement ayant une forte dépendance aux teneurs en Cu et Mg, et une espèce plus stable thermiquement ayant la même sensibilité à toutes les espèces de solutés. Lorsque les échantillons sont pré-vieillis, puis laissés pendant un mois (sNA1m), seule l’espèce d’amas thermiquement plus stables et également sensible à tous les ajouts de solutés existe. La formation de ces différents types d’amas en fonction du traitement thermique s'est traduite par les effets de l'ajout de solutés spécifiques sur les propriétés mécaniques observées. Dans l'état NA1m, les effets des additions de Cu et de Mg à l'alliage ont montré les plus fortes augmentations de la limite d'élasticité et du taux d’écrouissage, par rapport aux additions de Si. Ceci contraste avec la condition sNA1m pour laquelle les additions de Cu, Mg et Si augmentent toutes la limite d'élasticité de façon égale tandis que les additions de Cu se sont avérées avoir le plus fort effet sur l'augmentation du taux de durcissement par déformation, suivies par l'effet d’additions de Si, tandis que les additions de Mg n'ont pas eu d'effet. Les tests de sensibilité à la vitesse de déformation ont révélé une asymétrie entre les tests de variation vers le haut et vers le bas, selon laquelle la sensibilité à la vitesse de variation vers le bas est plus grande que la sensibilité à la vitesse de variation vers le haut. De plus, on a constaté que les ajouts de Si augmentent à la fois la sensibilité à la vitesse de déformation à variation ascendante et à variation descendante dans les conditions NA1m et sNA1m. Enfin, l'application de ces propriétés mécaniques à l'étude de l'évolution des strictions diffuse et locale a démontré que l'augmentation de l'exposant d’écrouissage retarde l'apparition du col diffus, par ailleurs l’augmentation de la sensibilité à la vitesse de déformation permet une distribution plus uniforme des déformations et des vitesses de déformation, permettant ainsi la stabilisation et la propagation du col de striction et retardant l'apparition du col local. L'effet de la sensibilité à la vitesse de déformation ascendante s'est révélé plus important que la variation descendante en raison de l'intensité de l'augmentation de la vitesse de déformation à l'intérieur du col sur une zone beaucoup plus petite. / Due to the increased demand for light weighting in automotive vehicles, solutions need to be created to allow automotive manufacturers to switch from highly formable but heavy steels to less formable but lighter aluminium alloys for body-in-white components; doors, roofs, hood. The 6xxx-series of aluminium alloys, based on the system of Al-Mg-Si-Cu, have shown promise for providing adequate strength and corrosion resistance but still, in the current state, one of their main limitations concerns their formability. This thesis aims to understand the effect of Si, Mg, and Cu additions under two different processing routes on the mechanical and formability properties of the AA6xxx-series. Differential scanning calorimetry and hardness testing are used to identify the effects of solute additions on the cluster states after natural ageing and pre-ageing. Tensile testing is used to capture the main mechanical properties: yield strength, tensile strength, strain hardening rate, and uniform elongation. Strain rate sensitivity testing is performed using dynamic strain rate changes to obtain not only the strain rate sensitivity due to rate-change increases (termed up-change), but uniquely, the strain rate sensitivity for rate-change decreases (termed down-change). Finally, using constitutive equations, the mechanical properties are used in combination with finite element modeling to capture the evolution of the strain and strain rate distribution in the evolution and transition of diffuse to local necking. It was found that in the case of natural ageing for one month (NA1m) two cluster types were detected, a less thermally stable species having a high dependency on the Cu and Mg contents, and a more thermally stable species being equally sensitive to all solute species. When samples were first pre-aged, then allowed to naturally age for one month (sNA1m) only the more thermally stable cluster species being equally sensitive to all solute additions existed. The formation of these different cluster types dependent on the heat treatment translated into the effects of specific solute additions on the observed mechanical properties. In the NA1m condition, the effects of Cu and Mg additions to the alloy showed the largest increases on the yield strength and strain hardening rate, as compared to Si additions. This is in contrast to the sNA1m condition whereby Cu, Mg, and Si additions all increased the yield strength equally while Cu additions proved to have the strongest effect on increasing the strain hardening rate, followed by the effect of Si additions, while Mg additions did not have an effect. From the strain rate sensitivity tests, an asymmetry between the up-change and down-change tests was observed whereby the down-change strain rate sensitivity was found to be larger than the up-change strain rate sensitivity. Additionally, Si additions were found to increase both the up-change and down-change strain rate sensitivity in both the NA1m and sNA1m conditions. Finally, the application of these mechanical properties to the onset and evolution of the diffuse and local neck demonstrated that increasing the strain hardening exponent delays the onset of diffuse necking, while increasing both the up-change and down-change strain rate sensitivities provides a more uniform strain and strain rate distribution around the neck, permitting the stabilization and propagation of the neck and delaying the onset of local necking. The effect of the up-change strain rate sensitivity was found to be more important than the down-change due to the intensity of the strain rate increase in the interior of the neck occurring over a much smaller area.