Thesis (Ph.D.)--University of Delaware, 2007. / Principal faculty advisor: Todd D. Royer, Dept. of Health, Nutrition, and Exercise Sciences. Includes bibliographical references.

Thesis (M.S.)--University of Delaware, 2006. / Principal faculty advisor: James G. Richards, College of Health Sciences. Includes bibliographical references.

Fibromyalgi (FM) är ett tillstånd av kronisk smärta, förutom smärtan karaktäriseras sjukdomen även av sömnstörningar, extrem trötthet och kognitiva störningar. Att ständigt leva med smärta innebär en stor stressfaktor och både fysiska, psykiska och stressrelaterade symtom är vanliga. Den ständigt närvarande upplevelsen av fatigue liknar den som beskrivs vid kroniskt trötthetssyndrom. Fatigue definieras som ett tillstånd av onaturlig och onormal eller extrem trötthet i hela kroppen, som inte är relaterat till aktivitet eller ansträngning. Syftet med studien var att beskriva vilka icke-farmakologiska interventioner som förekommer för att lindra fatigue hos patienter med FM. Metoden som användes var en litteraturstudie. Tolv vetenskapliga artiklar granskades och sammanställdes. Resultatet visade att interventioner som kombinerade träning och kognitiv inriktning hade bäst effekt för att lindra fatigue under en längre tid. Vikten av tro på patientens upplevelse av både smärta och fatigue visades sig vara betydelsefullt för att komma vidare i livet. Att stödja patienten med kunskap och engagemang från flera yrkeskategorier belystes som viktiga delar i vården av patienter med FM. Vidare forskning kring teambaserad vård behövs för att tydliggöra resultatet ytterligare.

Most components or structures experience in service a variety of cyclic stresses. In the case of cyclic constant amplitude loading the fatigue crack growth depends only on the crack, the component geometry and the applied loading. In the case of variable amplitude loading it also depends on the preceding cyclic loading history. Various types of load sequence (overloads, under-loads, or combination of them) may induce different load-interaction effects which can cause either acceleration or reduction of the fatigue crack growth rate. The previously developed UniGrow fatigue crack growth model for constant amplitude loading histories which was based on the analysis of the local stress-strain material behaviour at the crack tip has been improved, modified and extended to such a level of sophistication that it can be used for fatigue crack growth analyses of cracked bodies subjected to arbitrary variable amplitude loading spectra. It was shown that the UniGrow model enables to correctly predict the effect of the applied compressive stress and tensile overloads by accounting for the existence of the internal (residual) stresses induced by the reversed cyclic plasticity around the crack tip. This idea together with additional structural memory effect model has been formalized mathematically and coded into computer program convenient for predicting fatigue crack growth under arbitrary variable amplitude loading spectra. The experimental verification of the proposed model was performed using 7075-T6, 2024-T3, 2324-T7, 7010-T7, 7050-T7 aluminium alloys, Ti-17 titanium alloy, and 350WT steel. The good agreement between theoretical and experimental data proved the ability of the UniGrow model to predict fatigue crack growth and fatigue crack propagation life under a wide variety of real variable amplitude loading spectra.

Most components or structures experience in service a variety of cyclic stresses. In the case of cyclic constant amplitude loading the fatigue crack growth depends only on the crack, the component geometry and the applied loading. In the case of variable amplitude loading it also depends on the preceding cyclic loading history. Various types of load sequence (overloads, under-loads, or combination of them) may induce different load-interaction effects which can cause either acceleration or reduction of the fatigue crack growth rate. The previously developed UniGrow fatigue crack growth model for constant amplitude loading histories which was based on the analysis of the local stress-strain material behaviour at the crack tip has been improved, modified and extended to such a level of sophistication that it can be used for fatigue crack growth analyses of cracked bodies subjected to arbitrary variable amplitude loading spectra. It was shown that the UniGrow model enables to correctly predict the effect of the applied compressive stress and tensile overloads by accounting for the existence of the internal (residual) stresses induced by the reversed cyclic plasticity around the crack tip. This idea together with additional structural memory effect model has been formalized mathematically and coded into computer program convenient for predicting fatigue crack growth under arbitrary variable amplitude loading spectra. The experimental verification of the proposed model was performed using 7075-T6, 2024-T3, 2324-T7, 7010-T7, 7050-T7 aluminium alloys, Ti-17 titanium alloy, and 350WT steel. The good agreement between theoretical and experimental data proved the ability of the UniGrow model to predict fatigue crack growth and fatigue crack propagation life under a wide variety of real variable amplitude loading spectra.

Bakgrund: Sömnen är viktig för att människan ska kunna fungera optimalt. Nattetid utsöndras hormonet melatonin som gör kroppen trött, vilket försvårar skiftarbete. Några av världens största olyckor har skett under just de timmar kroppen biologiskt är som svagast. Att vara trött kan även jämföras med att ha en mindre mängd promillehalt av alkohol i blodet.Syfte: Syftet med studien var att beskriva hur sömnbrist hos omvårdnadspersonal påverkar vårdkvalitén och därmed patientsäkerhetenMetod: Uppsatsen gjordes som en litteraturstudie där elva vetenskapliga artiklar genomförda med antingen kvantitativ eller kvalitativ metod inkluderades. Artiklarna kvalitetsgranskades och analyserades med hjälp av en analysmall.Resultat: Av analysen framkom att långa arbetspass ledde till sömnbrist som i sin tur påverkade patientsäkerheten negativt då risken för att omvårdnadspersonalen skulle göra misstag ökade. Slutsats: Roterande skiftjobb och nattskiftsarbete är oundvikligt inom sjukvården då många av patienterna behöver vård dygnet runt. Sömnbrist är ett problem värt att uppmärksammas då det ger konsekvenser för både personal och patienter. Att vara ouppmärksam är en del av sömnbristen och det kan orsaka patienterna vårdlidande när omvårdnadspersonalen begår onödiga misstag.

The increasing use of alpha/beta Ti-Al alloys in critical aircraft gas turbine engine and airframe applications necessitates the further development of physically-based constitutive models that account for their complex microdeformation mechanisms. Alpha/beta Ti-Al alloys are dual-phase in nature consisting of a mixture of hcp (alpha) and bcc (beta) crystal structures, which through variation in alloying elements and/or processing techniques can be produced in a wide range of microstructural compositions and morphologies. A constitutive model for these materials should address the various sources of material anisotropy and heterogeneity at both the micro and macroscales. The main sources of anisotropy in these materials are the low symmetry of the hcp phase, the texture, the relative strengths of different slip systems, non-planar dislocation core structures, phase distributions, and dislocation substructure evolution. The focus of this work is the development of a 3-D crystal plasticity model for duplex Ti-6Al-4V (Ti-64), an (alpha+beta) alloy. The model is used to study the process of attachment fatigue. Attachment fatigue is a boundary layer phenomenon in which most of the plastic deformation and damage accumulation occurs at depths on the order of tens of microns and encompasses regions of only a few grains into the depth of the material. The use of computational micromechanics-based crystal plasticity models to study attachment fatigue is a relatively new approach. This approach has the potential to offer additional insight to classical homogeneous plasticity models, since the length scales over which relative slip and crack initiation occur during this process is on the order of microstructural dimensions. Emphasis is placed on understanding the effects that texture, slip strength anisotropy, and phase distribution have on the surface and subsurface deformation fields during attachment fatigue. The deformation fields are quantified in terms of cumulative effective plastic strain distributions, plastic strain maps, and plastic strain-based critical plane multiaxial fatigue parameters.

Aerospace structures are optimally designed and analyzed to specifically-defined engineering parameters. Thus, there is a strong drive to understand fatigue properties of materials, enabling an engineer determine their influence on these constraints. Space structures are usually designed to minimize weight and volume; hence thin designs utilizing strong, lightweight materials are ultimately desired. The goal of this research is to address an innovative testing technique of material properties not readily obtained from current test methods. The properties studied in this research include crack growth rates of small diameter rods in both the radial and transverse grain directions under a constant-amplitude tensile load at room temperature. This approach is illustrated on I-beam specimen manufactured from Aluminum 7075-T7351 Bar. The crack growth rates from the experimental data are then compared with literature results for plates, sheets, and extrusions of the same material. The research completed reveals the test results have comparable [Paris relationship] exponential m-values. The significance of quantifying small diameter metallic material properties have potential for great impact on the future of space structures, but are not limited to one part of the industry.

In order to keep up with the world’s energy demands, oil and gas producing companies have taken the initiative to explore offshore reserves or drill deeper into previously existing wells. The consequence of this, however, has to deal with the high temperatures and pressures encountered at increasing depths. For an oil well to maintain its integrity and be produced effectively and economically, it is pertinent that a complete zonal isolation is achieved during well completion. This complete zonal isolation can be compromised due to factors that come into play when oil well cement experiences cyclic loading conditions which can lead to fatigue failure as a consequence of extensive degradation of the microstructure of the cement material depending on stress levels and number of cycles. There have been a lot of research and experimental investigations on the mechanism of fatigue failure of concrete structures but the fatigue behavior of oil well cement is still relatively unknown to engineers. Research in the area of oil well cement design has led to improved cement designs and cementing practices but yet many cement integrity problems persist and this further strengthens the need to understand the mechanism of cement fatigue. This research seeks to develop a better understanding of the performance of the casing cement bond under HPHT well conditions that can lead to best practices and a model to predict well life. An analytical model, which can be used to evaluate stresses in the cement sheath based on actual wellbore parameters, was developed and combined effectively with finite element models to evaluate the fatigue and static loading behavior of a well. Based on the findings of this investigation, the mechanical properties of the casing, cement and formation as well loading conditions play a very big role in the static and fatigue failure of well cement. Finally, recommendations for future work on this subject were also presented in order to understand all tenets of cement fatigue and to develop governing equations.

The Strain Index was originally designed to analyze mono-task jobs. An experiment using a grip dynamometer was used to simulate six multiple task jobs to study the effect of complex tasks on localized muscle fatigue and to evaluate six different models used to calcula te a Complex Strain Index score. These models included average Strain Index score, unadjusted summation, duration adjusted summation, complex equation, minimum intensity, and peak intensity. Two methods of calculating a continuous Strain Index score were also analyzed. Ratings of perceived exertion, hand and forearm fatigue and discomfort, Difficulty Rating, maximum voluntary contraction (MVC), and percent strength loss were recorded for each of the six treatments. Electromyography (EMG) was also recorded for the 24 subjects (12 males and females) who completed the experiment. The EMG signal was analyzed using root mean square (RMS), initial mean power frequency (IMnPF), and slope of the mean power frequency (MnPF). Each treatment, lasting one hour each, contained a primary exertion (Task 1) of either 10% or 40% MVC for three seconds and a secondary exertion (Task 2) of either 10% or 40% MVC for one or three seconds. Subjective variables linearly increased (R2 > 0.88) over the duration of the treatments and significantly differed between treatments (p < 0.05). Percent strength loss was the only variable with a gender effect (p < 0.05). RMS values did not indicate fatigue and were constant over each treatment, but were highly correlated with percent MVC. A significant difference was not found in IMnPF between pre and post treatment values or between treatments (p > 0.05). A significant difference was found for MnPF slope pre and post treatment, but no treatment effect was found (p > 0.05). The complex equation method of calculating a Strain Index score was the only model of the six evaluated that met all criteria for being an acceptable method of calculating a Complex Strain Index score. The two continuous methods presented for calculating a Strain Index score should not be used for job analysis until further research evaluates their reliability, validity, and critical scores for Hazard Classification.