Browsing by Subject "FATIGUE"

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    Characterization of tensile, creep, and fatigue properties of 3D printed Acrylonitrile Butadiene Styrene
    (2016-08) Zhang, Hanyin; Zhang, Jing; Ryu, Jong Eun; Jones, Alan S.; Anwar, Sohel
    Acrylonitrile Butadiene Styrene (ABS) is the most widely used thermoplastics in 3D printing for making models, prototypes, patterns, tools and end-use parts. However, there is a lack of systematic understanding of the mechanical properties of 3D printed ABS components, including orientation-dependent tensile strength, creep, and fatigue properties. These mechanical properties are critically needed for design and application of 3D printed components. The main objective of this research is to systematically characterize key mechanical properties of 3D printed ABS components, including tensile, creep, and fatigue properties. Additionally, the eff ects of printing orientation on the mechanical prop- erties are investigated. There are two research approaches employed in the thesis: rst, experimental investigation of the tensile, creep, and fatigue properties of the 3D printed ABS components; second, laminate based finite-element modeling of tensile test to understand the stress distributions in different printing layers. The major conclusions of the thesis work are summarized as follows. The tensile test experiments show that the 0 printing orientation has the highest Young's modulus, 1.81 GPa, and ultimate strength, 224 MPa. The tensile test simulation shows a similar Young's modulus as the experiment in elastic region, indicating the robustness of laminate based finite element model. In the creep test, the 90 printing orientation has the lowest k value of 0.2 in the plastics creep model, suggesting the 90 is the most creep resistant among 0 , 45 , and 90 printing orientations. In the fatigue test, the average cycle number under load of 30 N is 3796 revolutions. The average cycle number decreases to 128 revolutions when the load is below 60N. Using the Paris Law, with the crack size of 0.75 mm long and stress intensity factor is varied from 352 to 700 MN -m^3/2 , the predicted fatigue crack growth rate is 0.0341 mm/cycle.
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    A longitudinal analysis of the impact of fatigue on return to activities of daily living during the first year after liver transplantation
    (Office of the Vice Chancellor for Research, 2012-04-13) Bah, Fatoumata; Winslow, Emily; Scott, Patricia J.
    Liver transplantation is often thought of as organ recovery and lifesaving surgery. The reality is a prolonged and stressful time for the patient and their family (Scott & Brown, 2011). The persistence of fatigue after liver transplantation is well documented in the research literature (Aadahl, Hansen, Kirkegaard, & Groenvold, 2002; van den Berg-Emons et al., 2006; Van Ginneken et al., 2010). However, there is no evidence as to the timing of how this fatigue dissipates during the early transplanted period and its impact on quality of life. Furthermore, studies on changes in fatigue do not start until 6 months after transplant, leaving a gap in knowledge of the patient’s experience post-surgery up to this point. This ongoing longitudinal study is aimed at better understanding the recovery process. Patients from a Midwest medical center (N=21) were followed post-discharge, at weeks 1-8 and at months 3, 6, 9, and 12. The FACIT-Fatigue Scale (Cella, 1997) indicates a decrease in fatigue scores (less fatigue) in those subjects without adverse events. Adverse events including re-hospitalization, surgical complications and organ rejection were associated with higher FACIT scores (higher level of fatigue) and less resolution over this first year. Through this research Dr. Scott and her team hope to translate their findings into educational resources for patients and their families to understand what to anticipate during the post-transplant recovery period.