The Effects Of Alloying And Grain Size On Fatigue Life Behavior, Cyclic Stress-Strain Behavior, and Microstructural Evolution of Unalloyed Mg and A Mg-Al Alloy

Mg and Mg alloys are important materials in structural applications where light weighting is important since the material exhibits an excellent strength to weight ratio and has a lower density than alloys such as Al and Ti. The formation of these materials requires thermomechanical processing during which the material undergoes deformation and then subsequent annealing which leads to recrystallization and grain growth. Both of these mechanisms have a significant influence on the cyclic stress-strain response and the fatigue life during cyclic loading. Therefore, understanding the influence of grain size and alloying on the microstructural evolution that occurs during annealing and its effect on low cycle fatigue behavior is important for increased use of these materials in structural applications. The influence of grain size and alloying on the microstructural evolution that occurs during static recrystallization and grain growth and its effect on the mechanical behavior during fatigue is being investigated. It is widely understood that grain characteristics (e.g. size and crystallographic orientation) can have a significant effect on the mechanical behavior of metallic materials. The static recrystallization behavior of unalloyed Mg and Mg-4Al was characterized over a range of annealing temperatures. The electron backscatter diffraction grain orientation spread technique was used to quantify the level of recrystallization at various annealing times. Recrystallization kinetics were characterized using the Johnson-Mehl-Avrami-Kolomogorov (JMAK) relationship and it was found that two sequential annealing stages exist. Stage 1 involves heterogeneous nucleation of recrystallization in regions with a high stored energy, including twins and grain boundaries. During Stage 2, recrystallization occurred predominately in the interior of deformed grains with incomplete recrystallization generally observed even at annealing times in excess of two weeks. Increasing the starting grain size in the unalloyed Mg condition led to a significant delay in recrystallization. The addition of Al had minimal effect on the recrystallization kinetics of Mg. To understand the influence of grain size and alloying on mechanical behavior, low cycle fatigue experiments using in-situ and ex-situ techniques were performed. The twinning and detwinning behavior of extruded fine-grained unalloyed Mg and Mg-4Al was investigated using in-situ high energy x-ray diffraction (HEXD) under displacement controlled, fully-reversed low cycle fatigue conditions. Measurements were conducted at three levels of applied strain. At cycle strains greater than 0.5%, tension-compression loop asymmetry was observed during cyclic loading which can be related to twinning during the compressive portion of the cycles followed by detwinning during the unloading (from peak compression) and tensile loading portions of the cycles. The twinning and detwinning were characterized by monitoring the evolution of x-ray diffractions peaks associated with the basal {0002} planes throughout a cycle. It was determined that the stress needed to initiate twinning during compression was independent of grain size and Al addition and that the stress needed for complete detwinning was closely related to the twin volume fraction. Ex-situ, strain-controlled LCF experiments were performed on both fine and coarse grained unalloyed Mg alloys as well as Mg-4Al. It was also found that for a given total strain amplitude the fatigue life was slightly increased in the fine-grained unalloyed Mg condition.PHDMaterials Science and EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/150010/1/aerielm_1.pd

An assessment of high touch object cleaning thoroughness using a fluorescent marker in two Australian hospitals

An Unassigned Group, An Unassigned DepartmentFull Tex

Supernovae, Landau Levels, and Pulsar Kicks

We derive the energy asymmetry given the proto-neutronstar during the time when the neutrino sphere is near the surface of the proto-neutron star, using the modified URCA process. The electrons produced with the anti-neutrinos are in Landau levels due to the strong magnetic field, and this leads to asymmetry in the neutrino momentum, and a pulsar kick. Our main prediction is that the large pulsar kicks start at about 10 s and last for about 10 s, with the corresponding neutrinos correlated in the direction of the magnetic field.Comment: 10 pages, seven figure

Library Monthly - February 2018

In this issue: 10th Annual Published Faculty Reception Nominate Students\u27 Best Papers for Our 3rd Annual Student Research Award! Lynn Library\u27s Creative Writing Contest Library Usage Fantastic Library Assistants Masterclass: Learning Through Observation 7 Amazing and Totally Free Things You Can Do on the Library Websitehttps://spiral.lynn.edu/libpubs/1013/thumbnail.jp

Providing an Adaptive Research Data Infrastructure for Clinical and Translational Investigators

Data in its many forms is a critical component of effective and productive research. As technology continues to evolve, and the volume and variety of sources of data continue to grow, accessing and leveraging all of this information is an ever increasing challenge. Concurrently, technology and information science is also driving novel ways to analyze, visualize, process and store this increasing amount of data. The ability to take advantage of these growth areas in order to aid the research efforts of the university is a critical need. The challenge to bring all of these various components into a unified resource for the university is a prodigious and multidimensional one. A subsection of the target data streams and sources include primary source clinical data, secondary source research data, clinical trials research data, financial data, genomic data to name a few. These sources reside in multiple SQL databases, HL7 message streams, hospital tracking systems, billing systems, surveys and others. To aid in overcoming this challenge, there is an ambitious effort underway to create a platform that will facilitate the aforementioned goals. The IT department, through the efforts of its Research Computing Services division will be embarking on this leading-edge, collaborative, and much needed data repository. The proposed design of the repository will take the form of a data aggregation layer capable of handling many disparate data feeds and sources, storing data in ways that support multiple access and analysis methods, all while providing researchers with increased tools and visibility.If our ability to manage and learn from this rapid increase of information and technologies grows, then so will our research opportunities. The effect will bring new innovations to the research community here at the university and by extension the community at large

Library Monthly - September 2016

In this issue: We\u27re Here to Help You! New Library Resources Don\u27t Cancel Class Initiative Where is Mozart? Solving the Textbook Problem Welcome, Hunter Murphy! New and Improved Juvenile Collectionhttps://spiral.lynn.edu/libpubs/1007/thumbnail.jp

On the Progenitors of Core-Collapse Supernovae

Theory holds that a star born with an initial mass between about 8 and 140 times the mass of the Sun will end its life through the catastrophic gravitational collapse of its iron core to a neutron star or black hole. This core collapse process is thought to usually be accompanied by the ejection of the star's envelope as a supernova. This established theory is now being tested observationally, with over three dozen core-collapse supernovae having had the properties of their progenitor stars directly measured through the examination of high-resolution images taken prior to the explosion. Here I review what has been learned from these studies and briefly examine the potential impact on stellar evolution theory, the existence of "failed supernovae", and our understanding of the core-collapse explosion mechanism.Comment: 7 Pages, invited review accepted for publication by Astrophysics and Space Science (special HEDLA 2010 issue

Implant Design Affects Walking and Stair Navigation after Total Knee Arthroplasty:a double-blinded randomised controlled trial

Background: Dissimilar total knee arthroplasty implant designs offer different functional characteristics. This is the first work in the literature to fully assess the Columbus ultra-congruent mobile (UCR) system with a rotating platform. Methods: This is a double-blinded randomised controlled trial, comparing the functional performance of the low congruent fixed (CR DD), ultra-congruent fixed (UC) and UCR Columbus Total Knee Systems. The pre-operative and post-operative functional performance of twenty-four osteoarthritic patients was evaluated against nine control participants when carrying out everyday tasks. Spatiotemporal, kinematic and kinetic gait parameters in walking and stair navigation were extracted by means of motion capture. Results: The UC implant provided better post-operative function, closely followed by the UCR design. However, both the UC and UCR groups exhibited restricted post-operative sagittal RoM (walking, 52.1 ± 4.4° and 53.2 ± 6.6°, respectively), whilst patients receiving a UCR implant did not show an improvement in their tibiofemoral axial rotation despite the bearing’s mobile design (walking, CR DD 13.2 ± 4.6°, UC 15.3 ± 6.7°, UCR 13.5 ± 5.4°). Patients with a CR DD fixed bearing showed a statistically significant post-operative improvement in their sagittal RoM when walking (56.8 ± 4.6°). Conclusion: It was concluded that both ultra-congruent designs in this study, the UC and UCR bearings, showed comparable functional performance and improvement after TKA surgery. The CR DD group showed the most prominent improvement in the sagittal RoM during walking. Trial registration: The study is registered under the clinical trial registration number: NCT02422251. Registered on April 21, 2015