Global ETD Search

1	Noninvasive assessment of mental, physical and respiratory stressors on cardiovascular function Looi, Jennifer C. January 2007 (has links) Thesis (M.S.)--Rutgers University, 2007. / Includes bibliographical references (p. 89-91). "Graduate Program in Biomedical Engineering." Includes bibliographical references (p. 89-91).
2	The response of silt-clay mixtures to cyclic loading Raybould, Matthew James January 1991 (has links) No description available. 631.4
3	Human skill maintenance in complex work environments : applications to extended spaceflight Sauer, Juergen January 1997 (has links) This thesis examines human performance under sub-optimal working conditions during work with complex and highly-automated process control systems. The operational context focuses on applications in extended spaceflight but the generic approach allows for generalisations beyond this target work environment The methodological approach is based on the use of a computerised multiple-task environment to carry out generic simulations of real work environments (micro-worlds) with a high level of ecological validity. For that purpose, a PC-based task. environment was developed to simulate the operation of a life support system in a spacecraft. This task environment has been used in lab-based experiments with trained participants from the student population and with real space crews during large-scale mission simulations. A series of six experiments was carried out (3lab and 3 field studies) to investigate the impact of different configurations of sub-optimal working conditions and unfavourable operator states, using the following independent variables: sleep deprivation, dialogue control, social isolation and confinement, training, noise, extended lay-off period and different types of system faults (corresponding to variations in workload). The task environment comprised up to five tasks, allowing for the observation of differential effects of the independent variables on different levels of cognitive activity. Dependent variables included primary task performance, secondary task performance, system control behaviour, information sampling behaviour, and subjective state measures. The findings suggested that primary performance was rarely affected, whereas certain secondary task measures and, notably, information sampling strategies appeared to be good indicators of changes in demand under the unfavourable conditions. The isolation and confinement experiments revealed no serious breakdown of performance among the crew but some indications of strain were observed. The use of two different training approaches displayed a very complex picture, with no method showing clear superiority over the other concerning performance, though there were differences in knowledge structure and system management behaviour. An important implication of the experimental work is that a broad methodological approach is needed in order to investigate the complex adjustment patterns displayed by individuals during the management of task demands under unfavourable conditions. 150
4	Grain boundary engineering for intergranular stress corrosion resistance in austenitic stainless steel Engelberg, Dirk Lars January 2006 (has links) Austenitic stainless steels are frequently used for engineering applications in aggressive environments. Typical sources of component failures are associated with localized attack at grain boundaries, such as intergranular corrosion and stress corrosion cracking. To prevent premature failures, structural integrity assessments are carried out, with the aim of predicting the maximum likelihood of cracking that may develop. For accurate predictions it is of great importance to know the interaction of parameters involved in life-determining processes. This PhD thesis investigates the effect of microstructure and stress on intergranular stress corrosion cracking in Type 302 / Type 304 austenitic stainless steels. High-resolution X-ray tomography has been successfully applied to examine, for the first time in 3-dimensions, in-situ, the interaction between microstructure and crack propagation. The development and subsequent failure of crack bridging ligaments has been observed and correlated with regions of ductile tearing persistent on the fracture surface. These ductile regions were consistent with the morphology of low-energy, twin-type grain boundaries, and are believed to possess the capability of shielding the crack tip. Following this observation, a new grain bridging model has been developed, in order to quantify the effect of static stress and crack bridging on the maximum likely crack length. The model was compared and evaluated with in the literature available percolation-like models. Intergranular stress corrosion tests in tetrathionate solutions have been designed and carried out to validate the new model. The assessment comprised,(i) a thorough examination of the microstructure and analysis parameters employed,(ii) the determination of the degree of sensitisation with subsequent crack path investigations,(iii) the identification of a suitable test system with associated grain boundary susceptibility criteria,(iv) the application of Grain Boundary Engineering (GBE) for microstructure control,(v) statistical crack length assessments of calibrated IGSCC test specimens. The results of these tests showed that the new model successfully predicts the magnitude of stress and the effect of grain boundary engineering on the maximum crack lengths. 620.1
5	Grundlagen der Elasto-Plastizität in Creo Simulate - Theorie und Anwendung / Basics of Elasto-Plasticity in Creo Simulate - Theory and Application Jakel, Roland 10 May 2012 (has links) (PDF) Der Vortrag beschreibt die Grundlagen der Elasto-Plastizität sowie die softwaretechnische Anwendung mit dem FEM-Programm Creo Simulate bzw. Pro/MECHANICA von PTC. Der erste Teil des Vortrages beschreibt die Charakteristika plastischen Verhaltens, unterschiedliche plastische Materialgesetze, Fließkriterien bei mehrachsiger Beanspruchung und unterschiedliche Verfestigungsmodelle. Im zweiten Vortragsteil werden Möglichkeiten und Grenzen der Berechnung elasto-plastischer Probleme mit der Software dargestellt sowie Anwendungstipps gegeben. Im dritten Vortragsteil schließlich werden verschiedene Beispiele vorgestellt, davon besonders ausführlich das Verhalten einer einachsigen elasto-plastischen Zugprobe vor und nach dem Eintreten der Einschnürdehnung. / This presentation describes the basics of elasto-plasticity and its application with the finite element software Creo Simulate (formerly Pro/MECHANICA) from PTC. The first part describes the characteristics of plastic behavior, different plastic material laws, yield criteria for multiaxial stress states and different hardening models. In the second part, the opportunities and limitations of analyzing elasto-plastic problems with the FEM-code are described and user information is provided. The last part finally presents different examples. Deeply treated is the behavior of a uniaxial tensile test specimen before and after elongation with necking appears. Elasto-Plastizität Creo Simulate Mechanica FEM Plastitzität kleiner Dehnungen Plastitzität großer Dehnungen technische Spannung wahre Spannung technische Dehnung logarithmische Dehnung kinematische und isotrope Verfestigung plastische Materialgesetze sprödes und duktiles Verhalten Mehrachsigkeit Lastschritte Entlasten Elasto-plasticity Creo Simulate Mechanica FEM small strain plasticity finite strain plasticity engineering stress true stress engineering strain logarithmic strain yield criteria kinematic and isotropic hardening elasto-plastic material laws brittle and ductile behavior multi-axial plasticity characteristic measures for plasticity load steps unloading meshing uniaxial tensile test with necking ddc:629 Fließbedingung Plastizität Dehnung Mehrachsigkeit Vernetzung
6	Grundlagen der Elasto-Plastizität in Creo Simulate - Theorie und Anwendung / Basics of Elasto-Plasticity in Creo Simulate - Theory and Application Jakel, Roland 10 May 2012 (has links) Der Vortrag beschreibt die Grundlagen der Elasto-Plastizität sowie die softwaretechnische Anwendung mit dem FEM-Programm Creo Simulate bzw. Pro/MECHANICA von PTC. Der erste Teil des Vortrages beschreibt die Charakteristika plastischen Verhaltens, unterschiedliche plastische Materialgesetze, Fließkriterien bei mehrachsiger Beanspruchung und unterschiedliche Verfestigungsmodelle. Im zweiten Vortragsteil werden Möglichkeiten und Grenzen der Berechnung elasto-plastischer Probleme mit der Software dargestellt sowie Anwendungstipps gegeben. Im dritten Vortragsteil schließlich werden verschiedene Beispiele vorgestellt, davon besonders ausführlich das Verhalten einer einachsigen elasto-plastischen Zugprobe vor und nach dem Eintreten der Einschnürdehnung. / This presentation describes the basics of elasto-plasticity and its application with the finite element software Creo Simulate (formerly Pro/MECHANICA) from PTC. The first part describes the characteristics of plastic behavior, different plastic material laws, yield criteria for multiaxial stress states and different hardening models. In the second part, the opportunities and limitations of analyzing elasto-plastic problems with the FEM-code are described and user information is provided. The last part finally presents different examples. Deeply treated is the behavior of a uniaxial tensile test specimen before and after elongation with necking appears. info:eu-repo/classification/ddc/629 ddc:629

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