In order to effectively and efficiently hydroform new automotive components, the formability of new tubular steels must be evaluated. Standard forming limit diagrams have been used for decades to evaluate and predict the formability of sheet steel formed along linear strain paths. However, tube hydroforming can present a problem since the pre-bending stage used in many hydroforming operations causes multiple non-linear strain paths. This thesis has modified a formability test method that deforms small-scale sheet steel samples in a single plane. The sample geometries were designed such that the strain paths achieved at the center of the samples were very near the plane strain condition. The four steels chosen for this study were: a deep drawing quality (DDQ), a high strength low alloy (HSLA) and two dual phase steels (DP600 and DP780). The plane strain formability for each of the four steels was tested in both the rolling and transverse directions. Three objective criteria were employed to evaluate and directly compare the formability of the four steels tested: difference in strain, difference in strain rate and local necking. The DDQ steel showed the highest formability followed in order by the HSLA, DP600 and DP780 steels. The repeatability in determining the forming limit strains using the difference in strain, the difference in strain rate and the local necking criteria for a 95% confidence interval was ± 1.5%, ± 1.2% and ± 3.2% engineering strain, respectively. The forming limit data collected for this thesis has been compared to results from full-scale tube hydroforming operations and free expansion tube burst tests carried out by researchers at the University of Waterloo on the same four materials. It was found that local necking results could be used to predict failure of hydroformed HSLA steel tubes with low levels of end-feed. However, this same method could only predict the failure of hydroformed DP600 steel tubes at higher levels of end-feed. The three objective criteria were not found to be suitable for predicting failure of free expansion tube burst tests. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2007-09-27 15:00:35.873

Zircaloy-2 is used extensively in the nuclear industry as a structural material for the reactor core in both light and heavy water reactors. The intergranular strains and texture greatly affect the mechanical properties of the material while in operation. Understanding the plastic deformation of Zircaloy-2 will improve on current plastic deformation models, particularly for twinning mechanisms, which are more active at lower temperatures, and are not yet well understood. For this study, neutron diffraction was used to track the lattice spacing and peak intensity in warm-rolled and recrystallized Zircaloy-2 slab for various crystallographic orientations at 77 K. Tests were performed in all three principle directions under tension and compression. The texture was measured for the deformed samples to help interpret the dominant deformation systems and then Electron Back Scattering Diffraction was used to identify and image the active twinning modes. Prism <a> slip, basal <a> slip, {10-12} and {11-2 1} tensile twinning, and {11-2 2} compression twinning were found to be contributing deformation systems in Zircaloy-2 at 77K. In this study, the diffraction elastic constants for Zircaloy-2 at room temperature and 77K are reported for the first time in open literature. These values will be useful in future experimental work by allowing a conversion between lattice spacing and residual stress. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2009-09-24 13:41:25.371

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Understanding the mechanical properties of Abdominal Aortic Aneurysms is paramount to improving treatment of this deadly condition. Here, we present work that makes strides in understanding not only the mechanical behavior and constitutive parameters of the two vessels that experience AAAs in different models, but also the effects of three major components of AAA formation. Biaxial mechanical tests were performed using a modified computer- controlled device. We examined the solid mechanics of the infrarenal and suprarenal aorta to examine why non-targeted models of AAAs (like Ang-II infusion) form exclusively in the suprarenal aorta whereas in humans the lesions preferentially form in the infrarenal aorta. The major difference between the two vessels is the elastin content and lamellar thickness in the suprarenal aorta. We analyzed the mechanical and constitutive effects of an acute loss of functional elastin via intraluminal exposure to elastase. We found that after elastase exposure, vessels were less distensible and experienced non-uniform, but modest dilatation. The constitutive parameters reflect elastin loss and increased collagen loading. We detailed the loss of smooth muscle cell contractility as found in human lesions that form in the thoracic aorta. We examined wild-type (WT), heterozygous (HET), and null (KO) a-smooth muscle actin (a-SMA) mice. The data and associated constitutive parameters were nearly identical amongst the three groups. We studied the biaxial mechanical tests on Angiotensin-II-infused ApoE-/- mice. This model is common model of AAA; however, instead of dilation and a thinning of the wall as in AAAs, Ang-II results in a dissecting aneurysm with adventitial growth. The pressure-diameter curves show a lack of sigmoidal shape attributed to elastin, there is some distensibility. The pressure-force behavior of these vessels is similar to a native vessel, unlike the pressure-force behavior of the elastase vessels. We have added a piece to the puzzle in understanding why AAAs occur preferentially in the suprarenal in mice as opposed to the infrarenal in humans. Our work with the a-SMA mice, introduces the idea that missense mutations in the ACTA2 gene, rather than the knocking out of the gene, leads to vascular diseases. We have increased the knowledge of the Ang-II infusion model by presenting biaxial mechanical data of the resulting dilatations. We have also further explored this widely used AAA model via histology to determine that in it is not a model for aneurysm development, but is a dissecting adventitial disease.

Cement-based composite materials are widely used in engineering applications. The strength and damage patterns of such materials depend upon the properties of the constituent components as well as the microstructure. Three scale levels are generally recognized in the analysis of the mechanical behaviour of composites, namely, macro-scale, meso-scale, and nano- or atomistic scale. Modelling of the mechanical properties at the meso-level provides a powerful means for the understanding of the physical processes underlying the macroscopic strength and failure behaviour of the composite materials under various loading conditions. This thesis endeavours to develop effective and efficient mesoscale models for cement-based composites, especially concrete, with a focus on dynamic analysis applications and in a three-dimensional stress-strain environment. These models are subsequently applied to investigate the intrinsic microscopic mechanisms governing the behaviour of such material under complex and high rate loadings, such as those due to shock, impact and blast. To cater to the needs of dynamic analysis under complex stress conditions, a general 2-dimensinal (2D) mesoscale modelling framework is further developed with the incorporation of the 3-D effect. This framework integrates the capabilities of MATLAB programming for the generation of the mesoscale geometric structure, ANSYS-CAE for finite element mesh generation, and the hydrocode LS-DYNA for solving the dynamic response of the model. The 3D effect is incorporated via a novel pseudo-3D modelling scheme such that the crucial lateral confinement effect during the transient dynamic response can be realistically represented. With the above mesoscale model a comprehensive investigation is conducted on the dynamic increase factor (DIF) in the concrete strength under compression, with particular focus on the variation trend at different strain rate regimes, and the key influencing factors. The wave propagation effect under high strain rate is scrutinised from a strip-by-strip perspective, and the correlation between the externally measured stress-strain quantities and the actual processes within the specimen is examined. The contribution of the material heterogeneity, as well as the structural effect (inertia), in the dynamic strength enhancement is evaluated. The classical Brazilian (splitting) test for the dynamic tensile behaviour of concrete is also investigated with the aid of the mesoscale model. Of particular interest here is the validity of such an indirect setup in reproducing the tensile behaviour of the specimen under high strain rates, as well as the effect of the heterogeneity in the dynamic tensile strength. Complications are found to arise as the loading rate increases. The change of the damage patterns with increase of the loading rate and the implications on the interpretation of the results are discussed. As an ideal solution to modelling of the 3-D effects, a methodology for the creation of a complex real 3-dimensional mesoscale model is put forward in the last part of the thesis. A geometric concept, called convex hull, is adopted for the representation of aggregates, and this makes it possible to utilize the relevant algorithms in computational geometry for the present purpose of generation of random 3-D aggregates. A take-and-place procedure is employed to facilitate the generation of the complete 3-D meso-structure. Associated techniques are developed for fast detection of particle inclusion-intersection. An example 3D mesoscale model is presented and representative numerical simulations are carried out to demonstrate the performance of the 3-D mesoscale modelling scheme.

Ekokardiografi är en mycket användbar teknik som bland annat kan bedöma vänsterkammarensfunktion hos hjärtat med hjälp av ejektionsfraktion (EF) och global longitudinell strain (GLS). EF är idag den metoden som används mest vid bedömning av vänsterkammarfunktionen och beräknas enligt Simpsons biplanmetod. GLS är en ny metod som mäter myokardiets deformation och har i tidigare studier visat sig vara en känslig metod och kan upptäcka förändringar i myokardiet tidigare än EF. Vid behandling av bröstcancer kan hjärtat påverkas toxiskt och därmed genomgår denna patientgrupp regelbundna kontroller med ekokardiografi.   Syftet med denna studie är att jämföra två ekokardiografiska metoder hos 20 stycken kvinnliga bröstcancerpatienter. Jämförelser har gjorts mellan EF beräknat med Simpsons biplanmetod (EFbi) och GLS samt mellan EFbi och EF beräknat från GLS (EFGLS). Detta är en kvantitativ retrospektiv studie där data insamlats mellan oktober-december 2014 på avdelningen klinisk fysiologi vid Länssjukhuset Ryhov i Jönköping. Den analysmetod som använts är McNemar´s test samt kappavärde. Resultatet av studien visar att EFbi och GLS gav en dålig överenstämmelse mellan metoderna och en rimlig överenstämmelse sågs mellan EFbi och EFGLS. Slutsatsen har dragits utifrån kappavärdet. / Echocardiography is a useful technique which can value the function of the left chamber of the heart by using ejection fraction (EF) and global longitudinal strain (GLS). Today EF is the most common method in assessments of the left chamber function and is calculated by Simpson´s biplanemethod. GLS is a new method that measures the myocardial deformation. It has been proved to be a sensitive method and can detect changes in the myocardium earlier than EF.   The purpose of this study is to compare two echocardiographic methods among 20 female breast cancer patients. Comparisons have been made between EF calculated with Simpson´s biplanemethod (EFbi) and GLS, and between EFbi and EF calculated by GLS (EFGLS). This is a quantitative retrospective study. The data used in this study was collected between October – December 2014 at the Department of Clinical Physiology at the Hospital Ryhov in Jönköping. The method used to analyse the results was McNemar´s test and Kappa value. The results of the study showed that EFbi and GLS gave a modest correspondence between the methods. A reasonable correspondence were observed between EFbi and EFGLS. The conclusion has been drawn from the kappa value.

The foundation of the education of our country lies in the hands of the primary school teachers. Unfortunately, teachers have to juggle many roles - not only are they expected to teach diverse classes and be a role model, but they also have to deal with social problems - all for very little remuneration. Our teachers are becoming less motivated, frustrated and very despondent and as a result, an increasing number of teachers are suffering from burnout. The objective of this research was to investigate the job characteristics associated with burnout as well as the burnout-strain relationship among primary school teachers in the North-West Province. A stratified random sample of 646 primary school teachers in the North West Province was taken. The Maslach Burnout Inventory - General Survey (MBEGS), Job Characteristics Scale and Your Health Questionnaire (third questionnaire of the ASSET) were used as measuring instruments. Cronbach alpha coefficients, inter-item correlation coefficients, Pearsonproduct correlation coefficients and canonical correlation coefficients were used to analyse the data. Structural equation modelling (SEM) methods were used to construct job characteristic models of burnout. The results showed that overload leads to exhaustion, which leads to cynicism and in turn to lack of professional efficacy. Job resources was found to be related to all three dimensions of burnout, while rewards played a moderating effect between both overload and exhaustion, and job resources and burnout. Exhaustion and lack of professional efficacy lead to physical and psychological strain. Recommendations were made for further research. / Thesis (M.Com. (Industrial Psychology))--North-West University, Potchefstroom Campus, 2004.