Conferences, Lectures, & Seminars
Events for April
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Inertial Effects in Fluid Locomotion
Wed, Apr 08, 2009 @ 03:30 PM - 04:30 PM
Aerospace and Mechanical Engineering
Conferences, Lectures, & Seminars
Steve Childress Professor Courant Institute of Mathematical SciencesNew York UniversityNew York, NY Inertial effects emerge in fluid locomotion as the Reynolds number reaches the range 1-10. The transition to flapping flight in a small mollusc suggests a bifurcation to thrust production at a finite Reynolds number. We describe a simple table-top experiment where this bifurcation could be observed. In order to study models at arbitrary Reynolds number we revisit the classic problem of swimming of a sheet, studied by G.I. Taylor in Stokes flow. At finite and large Reynold number Taylor's result is modified. The known results are reexamined for large Reynolds number using boundary-layer theory, and the nature of the expansions is clarified for wave-like motions of the sheet. We apply this approach to recoil swimming, a mechanism of locomotion that is known to work in a perfect fluid, thus extending the theory to a slightly viscous fluid.
Location: Seaver Science Library (SSL) - , Rm 150
Audiences: Everyone Is Invited
Contact: April Mundy
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Processing of bulk nanocrystalline oxide materials for optical and magnetic applications
Wed, Apr 15, 2009 @ 03:30 PM - 04:30 PM
Aerospace and Mechanical Engineering
Conferences, Lectures, & Seminars
Javier E. GarayDepartment of Mechanical EngineeringMaterials Science and Engineering ProgramUniversity of California, RiversideNanocrystalline materials display significantly different properties and behaviors than their microcrystalline counterparts, yet their direct application in products has been hindered by the difficulty in producing them reliably and efficiently. One reason is that consolidation of nanocrystalline powders usually results in large grain size increase and therefore loss of enhanced nanocrystalline properties. Recently, the versatile material processing technique of spark plasma sintering (SPS) has proven effective in overcoming the grain growth challengeit is now possible to efficiently produce viable nanocrystalline parts. The method draws its effectiveness from large electric current densities that serve to heat the materials and also alter the processing kinetics. After an overview of our processing techniques, I will present results on large-sized, fully dense oxides with grain sizes much less that 100 nm. The materials have very different properties than traditional materials. Properties presented include improved visible light transmittance, enhanced toughness, and ferri-antiferromagnetic coupling leading to exchange bias. The results will be discussed in terms of crystal length scale effects and proximity of nanoscale phases.
Location: Seaver Science Library, Rm 150
Audiences: Everyone Is Invited
Contact: April Mundy
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Fabrication of Bulk Metallic Glass Foams via Severe Plastic Deformation
Wed, Apr 29, 2009 @ 03:30 PM - 04:30 PM
Aerospace and Mechanical Engineering
Conferences, Lectures, & Seminars
Dr. Suveen N. MathaudhuMaterials EngineerWeapons and Materials Research DirectorateU.S. Army Research LaboratoryAbstract:Personnel protection for soldiers requires thin, shock-absorbing components in composite vest plate. Metallic foams exhibit outstanding energy absorption, due to ductile densification by plastic deformation of their struts. Foams based on bulk metallic glasses (BMG), which have the highest strength of any metals, and as such, should be optimal. An obstacle to the use of BMG foams is the brittle behavior. However, recent demonstrations show that the thin, sub-millimeter, struts of BMG foams are ductile in compression, with outstanding energy absorption. The work presented here will demonstrate that equal channel angular extrusion (ECAE) can be used to create composites of BMG powders and metallic powders (Cu, Ni, W) which can subsequently be converted to BMG open-cell foams by leaching of the metallic second phase. These foams show excellent mechanical properties and particularly high energy absorption. Comparisons with similar melt cast BMG foams will be made. The talk will cover the overview of severe plastic deformation processing, metallic glass powder consolidation and foam fabrication by ECAE.Short Bio:
Dr. Suveen Mathaudhu is a Materials Engineer with the Weapons and Materials Research Directorate of the U.S. Army Research Laboratory. Dr. Mathaudhu received his B.S. in Mechanical Engineering from Walla Walla College (College Place, WA) and his PhD in Mechanical Engineering from Texas A&M University (College Station, TX). Upon graduating, he accepted a post-doctoral fellowship, and subsequently a civil servant position at the U.S. Army Research Laboratory (Aberdeen Proving Ground, MD) with the purpose of establishing a deformation processing laboratory for research on advanced materials of interest to the DoD.
Location: Seaver Science Library, Rm 150
Audiences: Everyone Is Invited
Contact: April Mundy