High energy diffraction microscopy studies of fatigue and failure in superalloys

High Energy X-ray Diffraction Microscopy (HEDM) is a suite of synchrotron-based measurement techniques that probe structural responses in bulk polycrystals on the grain and subgrain length scales and do so nondestructively. Near-field HEDM yields three-dimensional maps of crystal lattice orientations including intragranular variations with a spatial resolution of ~2 micron and orientation resolution of 0.1 degree. Far-field HEDM adds strain sensitivity with \u3c1e–4 resolution, grain center-of-mass positions, and minority phase detection. Absorption or phase contrast computed tomography yields density contrast that can be used to detect voids, cracks, and micron scale sample deformation. With advanced instrumentation, these measurements can all be performed essentially simultaneously and during in-situ loading. This discussion will illustrate, through studies of fatigue fracture surfaces and crack formation in nickel superalloys, the power as well as limitations of multimodal high energy X-ray measurements. As a case study, measurements have been performed on two pins extracted from overlapping regions of the two fracture surfaces of a failed specimen. We have reassembled the two pieces (virtually) so that microstructural characteristics of the fracture surface can be studied. Inter- and transgranular regions of the fracture are identified and characterized. Deformation levels in grains, sensed through orientation variations, are compared as a function of distance from the fracture; the grain-to-grain dispersion is found to be large compared to any trend in the average. This study motivates proposed new measurements using in-situ loading and using both nf- and ff-HEDM combined with tomography

Father and son agreements

Cover title.Includes bibliographical references (page 23)

Compare your dairy business with an analysis of 56 central Missouri farms, 1952

Cover title.Includes bibliographical references

Trichobothrial mediation of an aquatic escape response: Directional jumps by the fishing spider, Dolomedes triton, foil frog attacks

Fishing spiders (Pisauridae) frequent the surfaces of ponds and streams and thereby expose themselves to predation by a variety of aquatic and semi-aquatic vertebrates. To assess the possibility that the impressive jumps of fishing spiders from the water surface function in evading attacks by frogs, attacks by bullfrogs (Rana catesbiana) and green frogs (R. clamitans) on Dolomedes triton Abbreviation: / a: acceleration (m s−2) fps: frames per second HS: high-speed video v: velocity (m s−1

Late Quaternary Facies and Sea Level History, Southwest Louisiana Continental Shelf.

Abstract Not Available

Let's study your farm business : an analysis of 45 farms, central Missouri, 1952

Cover title

Machinery use and investment on Missouri farms, 1951

This bulletin is a report on Department of Agricultural Economics Research Project Number 88, entitled 'Cost and Practice Problems of Farm Power and Machinery Modernization'--P. [2].Digitized 2007 AES.Includes bibliographical references

Asymmetric Dark Matter May Not Be Light

It is often said that asymmetric dark matter is light compared to typical weakly interacting massive particles. Here we point out a simple scheme with a neutrino portal and $\mathcal{O}(60 \text{ GeV})$ asymmetric dark matter which may be ''added'' to any standard baryogenesis scenario. The dark sector contains a copy of the Standard Model gauge group, as well as (at least) one matter family, Higgs, and right-handed neutrino. After baryogenesis, some lepton asymmetry is transferred to the dark sector through the neutrino portal where dark sphalerons convert it into a dark baryon asymmetry. Dark hadrons form asymmetric dark matter and may be directly detected due to the vector portal. Surprisingly, even dark anti-neutrons may be directly detected if they have a sizeable electric dipole moment. The dark photons visibly decay at current and future experiments which probe complementary parameter space to dark matter direct detection searches. Exotic Higgs decays are excellent signals at future $e^+ e^-$ Higgs factories.Comment: 8 pages, 3 figure