The ability to non-destructively map the residual strain field inside an engineering component is important for predicting its fatigue life or developing processing methods to prevent failure or enhance performance. In this paper, we describe a new residual strain mapping program at the Advanced Photon Source, Argonne National Laboratory. The new program is based on energy dispersive x-ray diffraction (EDXRD). It is capable of non-destructively penetrating a several-cm thick polycrystalline sample fabricated from engineering alloys using high-energy x-rays and measuring the residual strain field with mm or better spatial resolution and approximately $$\pm 1 \times 10^{-4}$$ strain resolution. A multi-element detector array is employed to measure multiple strain components simultaneously. The residual strain mapping setup is augmented with a high-energy tomography capability, allowing precise alignment of the material volume of interest for residual strain mapping and providing a complementary view of the structure to understand the measured strain field. These measurement capabilities are demonstrated using several strain mapping examples ranging from polycrystalline structural alloys to biological materials. We also provide some guidance for the future users of the program for a successful residual strain mapping experiment. We are expanding the capabilities of the new setup with various in situ capabilities including thermo-mechanical loading.

A suite of finite element simulations was executed to find optimal values for high-temperature single crystal elastic moduli of low solvus high refractory (LSHR) nickel super alloy from high energy x-ray diffraction microscopy (HEDM) measurements. In the experiment, a polycrystalline specimen was scanned in an unloaded state to determine a three-dimensional spatial map of lattice orientations in the gauge volume. The specimen was then heated and loaded while performing in situ X-ray measurements to determine grain-averaged elastic strain tensors at several macroscopic loads. The finite element simulations, utilizing three meshes of increasing resolution, mimicked the experimental loading. Initial simulations were conducted to find a box containing the optimal moduli, from which a finer grid of trial moduli was created. A suite of simulations was then executed using these meshes and moduli. For each simulation, an error was determined by comparing the simulated strain field to the measured one, with the resulting data set providing rich information about this fitting process. Anisotropy of the optimal moduli was studied relative to the level of mesh refinement, and a tendency for the anisotropy to decrease as the mesh refinement increases was found. Optimal values of anisotropic moduli and isotropic moduli were determined using the presented optimization methodology; the anisotropic moduli gave appreciably better results. Furthermore, we examined the sensitivity of the error to changes in the moduli; the takeaway was that size of the modulus had a primary effect on the sensitivity, with larger moduli being harder to fit.

The plastic deformation of crystalline materials is usually modeled as smoothly progressing in space and time, yet modern studies show intermittency in the deformation dynamics of single-crystals arising from avalanche behavior of dislocation ensembles under uniform applied loads. However, once the prism of the microstructure in polycrystalline materials disperses and redistributes the load on a grain-by-grain basis, additional length and time scales are involved. Thus, the question is open as to how deformation intermittency manifests for the nonuniform grain-scale internal driving forces interacting with the finer-scale dislocation ensemble behavior. In this work we track the evolution of elastic strain within individual grains of a creep-loaded titanium alloy, revealing widely varying internal strains that fluctuate over time. The findings provide direct evidence of how flow intermittency proceeds for an aggregate of similar to 700 grains while showing the influences of multiscale ensemble interactions and opening new avenues for advancing plasticity modeling.

Residual stress in an engineering component induced from processing is pervasive and can impact the component’s performance significantly. There are numerous destructive and non-destructive techniques that are available to determine the residual stresses in a component. In this work, an interference fit sample was manufactured from a titanium alloy. The sample was equipped with a set of strain gauges to measure the strains induced by the interference process used for sample assembly. Energy dispersive diffraction experiment using synchrotron radiation was conducted to measure the lattice strains in the interference fit sample. Hole drilling measurements were also conducted on the sample. The non-destructive X-ray result is compared with strain gauge measurements, and found to be in good agreement when appropriately averaged.

The Seyfert 1 galaxy, Ark 120, is a prototype example of the so -called class of bare nucleus AGN, whereby there is no known evidence for the presence of io nized gas along the direct line of sight. Here deep ( > 400 ks exposure), high resolution X-ray spectroscopy of Ark 120 is presented, fromXMM-Newtonobservations which were carried out in March 2014, together with simultaneousChandra/HETG exposures. The high resolution spectra confirmed the l ack of intrinsic absorbing gas associated with Ark 120, with the only X-ray absorption present originating from the ISM of our own Galaxy, with a possible slight enhancement of the Oxygen abundance required with respect to the expected ISM values i n the Solar neighbourhood. However, the presence of several soft X-ray emission lines are r ev aled for the first time in the XMM-NewtonRGS spectrum, associated to the AGN and arising from the He an d H-like ions of N, O, Ne and Mg. The He-like line profiles of N, O and Ne appear velocity broadened, with typical FWHM widths of∼ 5000 km s, whereas the H-like profiles are unresolved. From the clean measurement of the He-like triplets, we deduce tha t the broad lines arise from gas of densityne ∼ 10 cm, while the photoionization calculations infer that the emi tting gas covers at least 10% of 4π steradian. Thus the broad soft X-ray profiles appear coincid e t with an X-ray component of the optical–UV Broad Line Region on sub-p c scales, whereas the narrow profiles originate on larger pc scales, perhaps coincident w ith the AGN Narrow Line Region. The observations show that Ark 120 is not intrinsically bare nd substantial X-ray emitting gas exists out of our direct line of sight towards this AGN. Subject headings: galaxies:active — Seyferts: individual: Ark 120 — X-rays: g alaxies Center for Space Science and Technology, University of Mary land Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA: jreeves@umbc.edu Astrophysics Group, School of Physical and Geographical Sc iences, Keele University, Keele, Staffordshire, ST5 5BG, U K; j.n.reeves@keele.ac.uk Observatoire Astronomique de Strasbourg, Université de S trasbourg, CNRS, UMR 7550, 11 rue de l’Université, F-67000 Strasbourg, France INAF Osservatorio Astronomico di Brera, Via Bianchi 46 I-2 3807 Merate (LC), Italy Dept of Physics and Astronomy, University of Leicester, Uni versity Road, Leicester LE1 7RH, UK Department of Physics, University of Maryland Baltimore Co unty, 1000 Hilltop Circle, Baltimore, MD 21250, USA

Journal Article Changing the Paradigm for Engineering Design by Merging High Energy X-ray Data with Materials Modeling Get access PA Shade, PA Shade Air Force Research Laboratory, Materials & Manufacturing Directorate, Wright-Patterson AFB, OH 445433, USA Search for other works by this author on: Oxford Academic Google Scholar JC Schuren, JC Schuren Air Force Research Laboratory, Materials & Manufacturing Directorate, Wright-Patterson AFB, OH 445433, USA Search for other works by this author on: Oxford Academic Google Scholar JV Bernier, JV Bernier Lawrence Livermore National Laboratory, Engineering Directorate, Livermore, CA, 94550, USA Search for other works by this author on: Oxford Academic Google Scholar SF Li, SF Li Lawrence Livermore National Laboratory, Engineering Directorate, Livermore, CA, 94550, USA Search for other works by this author on: Oxford Academic Google Scholar B Blank, B Blank PulseRay, Beaver Dams, NY, 14812, USA Search for other works by this author on: Oxford Academic Google Scholar J Lind, J Lind Carnegie Mellon University, Pittsburgh, PA, 15213, USA Search for other works by this author on: Oxford Academic Google Scholar P Kenesei, P Kenesei Advanced Photon Source, Argonne National Laboratory, Argonne, IL, 60439, USA Search for other works by this author on: Oxford Academic Google Scholar U Lienert, U Lienert DESY-Petra III, Hamburg, Germany Search for other works by this author on: Oxford Academic Google Scholar RM Suter, RM Suter Carnegie Mellon University, Pittsburgh, PA, 15213, USA Search for other works by this author on: Oxford Academic Google Scholar TJ Turner, TJ Turner Air Force Research Laboratory, Materials & Manufacturing Directorate, Wright-Patterson AFB, OH 445433, USA Search for other works by this author on: Oxford Academic Google Scholar ... Show more DM Dimiduk, DM Dimiduk Air Force Research Laboratory, Materials & Manufacturing Directorate, Wright-Patterson AFB, OH 445433, USA Search for other works by this author on: Oxford Academic Google Scholar J Almer J Almer Advanced Photon Source, Argonne National Laboratory, Argonne, IL, 60439, USA Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 20, Issue S3, 1 August 2014, Pages 1444–1445, https://doi.org/10.1017/S1431927614008952 Published: 27 August 2014

We present the results of a new spectroscopic study of Fe K-band absorption in active galactic nuclei (AGN). Using data obtained from the Suzaku public archive we have performed a statistically driven blind search for Fe XXV He alpha and/or Fe XXVI Ly alpha absorption lines in a large sample of 51 Type 1.0-1.9 AGN. Through extensive Monte Carlo simulations we find that statistically significant absorption is detected at E greater than or similar to 6.7 keV in 20/51 sources at the P-MC = 95 per cent level, which corresponds to similar to 40 per cent of the total sample. In all cases, individual absorption lines are detected independently and simultaneously amongst the two (or three) available X-ray imaging spectrometer detectors, which confirms the robustness of the line detections. The most frequently observed outflow phenomenology consists of two discrete absorption troughs corresponding to Fe XXV He alpha and Fe XXVI Ly alpha at a common velocity shift. From xstar fitting the mean column density and ionization parameter for the Fe K absorption components are log (N-H/cm(-2)) approximate to 23 and log (xi/erg cm s(-1)) approximate to 4.5, respectively. Measured outflow velocities span a continuous range from < 1500 km s(-1) up to similar to 100 000 km s(-1), with mean and median values of similar to 0.1 c and similar to 0.056 c, respectively. The results of this work are consistent with those recently obtained using XMM-Newton and independently provides strong evidence for the existence of very highly ionized circumnuclear material in a significant fraction of both radio-quiet and radio-loud AGN in the local universe.

A numerical study using crystal plasticity finite element method was performed in order to investigate the influence of the grain boundary morphology (stair-case or smooth/flat) and the selection of different mesh types (hexahedral and tetrahedral meshes) on the distribution of simulated plasticity heterogeneities. A bicrystal (a hard grain and a soft grain) sphere embedded in a cubic grain was utilized to perform the current numerical study. The volume averaged responses for the simulated plasticity values (von Mises stress, total accumulated slip system shear and maximum accumulated slip system shear) showed no significant dependence on the grain boundary representation and mesh type. However, the bicrystal represented by uniform hexahedral meshes with stair-case grain boundaries tends to show more extreme local plasticity values (in the head and tail of the distribution), particularly populated in the grain boundary region. Differences in local plasticity values between the stair-case and the smooth (or flat) grain boundary cases and between the hexahedral and the tetrahedral mesh cases were largest in the grain boundary region, and the degree of the differences depended upon the plasticity susceptibility of the grain. The simulation results suggest that the grain boundary represented by the stair-case morphology can be a source and/or a sink for local extreme plasticity, compared to the grain boundary represented by the smooth (or flat) morphology.

This work presents two integrated experimental and modeling approaches for examining polycrystals at different length scales, which utilize different experimental techniques but the same elasto-crystal plasticity based finite element model (CPFEM). The goal of this work is to calibrate modeling approaches through experimental data, and then use the models to gain insight into the mechanics of deformation in nickel and nickel-base superalloy polycrystals. The first study utilized a micro-tensile test specimen of pure nickel with 259 grains, where the CPFEM simulations were initiated with the explicit 3D microstructure as measured with 3D-Electron Back Scattering Detection (EBSD) serial sectioning and compared with surface deformations measured with Digital Image Correlation (DIC). The second study utilized a larger polycrystalline nickel-base superalloy specimen with approximately 50,000 grains, where the CPFEM simulation results are compared with lattice strain data obtained through high energy x-ray diffraction utilizing a synchrotron x-ray source. In both cases the simulations are compared with different aspects of the experimental strain information (surface strain or lattice strain), and then the simulations are used to explore aspects of the heterogeneous nature of the deformation that are difficult or impossible to measure experimentally.

This work presents an integrated experimental and modeling approach for examining the deformation of a pure nickel polycrystal utilizing micro-mechanical testing and a crystal-based elasto-viscoplastic finite-element model (CPFEM). The objective is to study the influence of microstructure on the heterogeneous deformation in polycrystalline materials, and to utilize a modeling framework to explore aspects of the deformation that are difficult or impossible to measure experimentally. To accomplish this, a micro-tension specimen containing 259 grains was created from a pure nickel foil material and deformed in uniaxial tension. After the deformation, the specimen was destructively serial sectioned in concert with electron back scattering diffraction, and these data were used to instantiate a CPFEM simulation. The material parameters in the CPFEM model were calibrated by matching the experimental macroscopic stress-strain response of the micro-tension specimen, and then the simulation results were compared with experimental surface deformations measured with digital image correlation. After validating the simulation results by comparing measured and predicted surface strain distributions, a parametric study of the influence of both crystallographic texture and grain morphology is presented to better understand the influence of microstructure on the development of heterogeneous deformation in the pure nickel polycrystalline material.

This work presents a three tiered modeling approach to examine grain boundary interfaces in a pure Nickel foil material utilizing a crystal plasticity based finite element model (CPFEM). The goal of this work is to calibrate a modeling approach through comparison to experimental data, and then use the models to gain insight into deformation at grain boundaries in Nickel and Nickel-base superalloy polycrystals. The first study utilizes a multi-crystal micro-tension specimen and simulations to calibrate the CPFEM model and examine the development of “hot-spots” or localized plasticity near the grain boundaries. Some orientation combinations exhibit localized plasticity along the boundary (bad-actor boundaries) while others do not. Insight from the deformation of this model is then used to instantiate simulations of Nickel bi-crystals which exhibit localized plasticity near the boundary. The third study embeds the grain boundary interfaces of interest, as determined from the bi-crystal simulations, into a larger polycrystalline simulation utilizing the same CPFEM framework. Using these interfaces we study deformation at these “characteristic” interfaces when subjected to the generalized loading conditions present in a polycrystalline microstructure.

Isothermal, uniaxial compression tests and accompanying numerical simulations were conducted on Waspaloy-ingot specimens to quantify deformation heterogeneity during hot working of coarse, columnar-grain materials. This was used as a means to approximate deformation processing in ingot materials. Electron-backscatter-diffraction (EBSD) measurements were made before and after compression testing to quantify microstructure evolution. A crystal-plasticity finite-element-method model, in which the starting microstructure was instantiated using EBSD scans of the undeformed material, was used to simulate the deformation. Good agreement was found between observations and simulation predictions of specimen profiles and intra-grain misorientations. The simulation results also revealed that the grain neighborhood appeared to be a principal factor controlling the heterogeneity of deformation at the grain scale. Significant differences in the simulated deformation of a given grain were noted for various arrangements of the orientations of its neighbors. In particular, the first-and second-nearest neighbors of a given grain have the most significant effect on heterogeneous deformation behavior.

Reverberation from scattering material around the black ho le in active galactic nuclei is expected to produce a characteristic signature in a Fourier analysis of the time delays between directlyviewed continuum emission and the scattered light. Narrowline Seyfert 1 galaxies (NLS1) are highly variable at X-ray energies, and are ideal candidates for the detection of X-ray reverberation. We show new analysis of a small sample of NLS1 that clearly sho w the expected time-delay signature, providing strong evidence for the existence of a high covering fraction of scattering and absorbing material a few tens to hundreds of gravitation l radii from the black hole. We also show that an alternative interpretation of time delays in the NLS1 1H 0707–495, as arising about one gravitational radius from the black hole, is stron gly disfavoured in an analysis of the energy-dependence of the time delays.

Mechanism-based models for the evolution of defects during the thermomechanical processing of aerospace titanium- and nickel-based alloys are reviewed. These defects include those comprising microstructural/metal-flow irregularities and those that are damage related (i.e., cracks and cavities). The development of undesirable/nonuniform microstructures and cavities during the mill processing of alpha/beta titanium alloys is addressed first. Relatively simple, diffusion-based models of spheroidization and coarsening are applied to quantify the propensity for microstructure nonuniformities. Similarly, first-order micromechanical models have been formulated to estimate the effect of local crystallographic texture on nonuniform flow, the generation of triaxial stresses, and cavity growth/closure in alpha/beta titanium alloys with a colony-alpha microstructure. The occurrence of nonuniform grain structures (and so-called ALA, or “as large as,” grains) in cast, wrought, and powder-metallurgy superalloys is also discussed. A physics-based model to treat the topology of recrystallization and the evolution of ALA grains in such materials is proposed.

A methodology for incorporating a description of material structure into a finite element formulation is presented. This work describes an experiment/simulation - based methodology for characterizing attributes of material structure, and then incorporating those attributes into a modeling frame work. The modeling framework was used to study the development of deformation induced surface roughening in thin sheets machined from? AA 7050 thick plate. Predicting this roughening phenomenon necessitates the quantification and representation of material structure and processes that exist over several size scales. Electron backscatter diffraction experiments were used for material structure characterization, which included crystallographic texture, distributions in grain sizes, and a distribution in intragrain misorientation. These distributions in structure were incorporated in digital microstructures which represented virtual specimens composed of finite element-discretized crystals. A continuum slip-poly,crystal plasticity model was coupled with the digital microstructures to study the differences in roughening seen in specimens deformed along the rolling direction and transverse direction of the plate material. The success of these simulations build additional insight into how to incorporate material structure into deformation simulations, and build representative virtual specimens that can be used to study the complicated processes that underlie deformation mechanics in polycrystalline materials.

The deformation response and recrystallization behavior of a coarse, columnar-grain superalloy ingot material, Waspaloy, with a < 100 > fiber texture were established. For this purpose, isothermal hot compression tests were performed on cylindrical and double-cone samples at supersolvus temperatures under both monotonic (constant strain rate) and multi-hit conditions. Plastic flow showed a noticeable dependence on test direction relative to the columnar-grain orientation; the observed anisotropy in peak flow stress and flow softening were explained on the basis of the evolution of crystallographic texture during recrystallization. Similarly, anisotropy in dynamic recrystallization kinetics with respect to test direction was interpreted in terms of the effect of initial texture on the plastic work imposed per increment of macroscopic strain. Nevertheless, the broad kinetics for the coarse-grain, ingot material deformed under both monotonic and multi-hit conditions were comparable to those previously measured for fine-grain, wrought Waspaloy. Such an effect was attributed to the beneficial influence of the nucleation of recrystallization at both grain boundaries and carbide particles in the ingot material. In addition, a spatial non-uniformity in recrystallization was found in the ingot material and was interpreted in the context of the grain-boundary character and non-uniform strain at the grain/intragrain scale. A suite of tools being developed to model recrystallization phenomena during the breakdown of superalloy ingots is described. These tools include a mechanistic cellular automata; a mesoscale, mechanism-based model; and the crystal-plasticity finite-element method.

We present results from Chandra HETGS (250 ks over two epochs) and XMM-Newton EPIC and RGS (60 ks) observations of NGC 2110, which has been historically classified as a narrow emission line galaxy. Our results support the interpretation that the source is a Seyfert 2 viewed through a patchy absorber. The nuclear X-ray spectrum of the source is best described by a power law of photon index Γ ∼ 1.7, modified by absorption from multiple layers of neutral material at a large distance from the central supermassive black hole. We report the strong detections of Fe Kα and Si Kα lines, which are marginally resolved with the Chandra HETGS, and we constrain the emission radius of the fluorescing material to ≳1 pc. There is some evidence for modest additional broadening at the base of the narrow Fe Kα core with a velocity ~4500 km s−1. We find tentative evidence for ionized emission (O VIII Lyα, an O VIII RRC feature, and possibly a Ne IX forbidden line) in the Chandra MEG and XMM-Newton RGS spectra, which could be associated with the known extended X-ray emission that lies ~160 pc from the nucleus. We suggest that the 1023 cm−2 partially covering absorber originates in broad-line region clouds in the vicinity of the AGN, and that the 3 × 1022 cm−2 coverer is likely to have a more distant origin and have a flattened geometry in order to allow the small-scale radio jet to escape.