Stress analysis of V-notches with and without cracks, with application to foreign object damage

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The Kondo Resonance in Electron Spectroscopy

The Kondo resonance is the spectral manifestation of the Kondo properties of the impurity Anderson model, and also plays a central role in the dynamical mean-field theory (DMFT) for correlated electron lattice systems. This article presents an overview of electron spectroscopy studies of the resonance for the 4f electrons of cerium compounds, and for the 3d electrons of V_2O_3, including beginning efforts at using angle resolved photoemission to determine the k-dependence of the resonance. The overview includes the comparison and analysis of spectroscopy data with theoretical spectra as calculated for the impurity model and as obtained by DMFT, and the Kondo volume collapse calculation of the cerium alpha-gamma phase transition boundary, with its spectroscopic underpinnings.Comment: 32 pages, 11 figures, 151 references; paper for special issue of J. Phys. Soc. Jpn. on "Kondo Effect--40 Years after the Discovery

The application of asymptotic analysis for modes I and III semi-infinite wedge solutions to a circumferentially notched shaft

Mode I and mode III solutions for sharp notch roots are derived and compared with representative full-field solutions. The example geometry studied is a circumferentially notched shaft, loaded in both tension and torsion. The calibration for the notch root intensity factors has been carried out using the finite element method. The combined effects of tension and torsion have been briefly considered as an example

Evaluation and analysis of residual stresses due to foreign object damage

Foreign object damage (FOD) in gas turbine engines occurs due to the ingestion of small inorganic particles (small stones and sand particles). The damage caused to the blade leading edge may lead to premature crack initiation and ultimately blade failure due the action of time-varying tensile loads. The problem of evaluating the severity of FOD and the induced reduction of component life was investigated in the laboratory, by reproducing the damage conditions accurately and subjecting the impacted blade to fatigue loading simulating the service conditions. One particular aspect of post-FOD analysis focuses on the evaluation of residual stresses in the vicinity of the notch. Residual stresses play an important role in controlling the rate of crack initiation and propagation, and may be responsible for accelerated crack growth if they are tensile ahead of the incipient crack, or can cause retardation otherwise. The present study was aimed at experimental and numerical investigate the magnitude and spatial variation of residual stresses in this region. Experimentally, a gas gun was used to introduce the damage by firing a hardened steel cube "point first". Following impact the residual stresses were evaluated using two different experimental techniques involving X-ray diffraction: laboratory low energy monochromatic stress measurement, and high-energy white beam synchrotron stress measurement. The results are compared with the numerical model of the impact phenomenon that was constructed for a selected portion of the blade material, and from which the residual stress pattern following simulated impact was calculated using Bammann damage material model. Both sets of experimental measurements are critically compared with the numerical result, and the relationship between them is discussed