@article{MuellerCooperLangeetal.2017,
  author    = {M{\"u}ller, B. R. and Cooper, R. C. and Lange, A. and Kupsch, Andreas and Wheeler, M. and Hentschel, M. P. and Staude, A. and Pandey, A. and Shyam, A. and Bruno, Giovanni},
  title     = {Stress-induced microcrack density evolution in beta-eucryptite ceramics},
  series = {Acta materialia},
  volume    = {144},
  journal   = {Acta materialia},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {1359-6454},
  doi       = {10.1016/j.actamat.2017.10.030},
  pages     = {627 -- 641},
  year      = {2017},
  abstract  = {In order to investigate their microcracking behaviour, the microstructures of several beta-eucryptite ceramics, obtained from glass precursor and cerammed to yield different grain sizes and microcrack densities, were characterized by laboratory and synchrotron x-ray refraction and tomography. Results were compared with those obtained from scanning electron microscopy (SEM). In SEM images, the characterized materials appeared fully dense but computed tomography showed the presence of pore clusters. Uniaxial tensile testing was performed on specimens while strain maps were recorded and analyzed by Digital Image Correlation (DIC). X-ray refraction techniques were applied on specimens before and after tensile testing to measure the amount of the internal specific surface (i.e., area per unit volume). X-ray refraction revealed that (a) the small grain size (SGS) material contained a large specific surface, originating from the grain boundaries and the interfaces of TiO2 precipitates; (b) the medium (MGS) and large grain size (LGS) materials possessed higher amounts of specific surface compared to SGS material due to microcracks, which decreased after tensile loading; (c) the precursor glass had negligible internal surface. The unexpected decrease in the internal surface of MGS and LGS after tensile testing is explained by the presence of compressive regions in the DIC strain maps and further by theoretical arguments. It is suggested that while some microcracks merge via propagation, more close mechanically, thereby explaining the observed X-ray refraction results. The mechanisms proposed would allow the development of a strain hardening route in ceramics.},
  language  = {en}
}
@article{NellesenLaquaiMuelleretal.2018,
  author    = {Nellesen, Jens and Laquai, R. and M{\"u}ller, B. R. and Kupsch, Andreas and Hentschel, M. P. and Anar, N. B. and Soppa, E. and Tillmann, W. and Bruno, Giovanni},
  title     = {In situ analysis of damage evolution in an Al/ Al2O3 MMC under tensile load by synchrotron X-ray refraction imaging},
  series = {Journal of materials science},
  volume    = {53},
  journal   = {Journal of materials science},
  number    = {8},
  publisher = {Springer},
  address   = {New York},
  issn      = {0022-2461},
  doi       = {10.1007/s10853-017-1957-x},
  pages     = {6021 -- 6032},
  year      = {2018},
  abstract  = {The in situ analysis of the damage evolution in a metal matrix composite (MMC) using synchrotron X-ray refraction radiography (SXRR) is presented. The investigated material is an Al alloy (6061)/10 vol MMC after T6 heat treatment. In an interrupted tensile test the gauge section of dog bone-shaped specimens is imaged in different states of tensile loading. On the basis of the SXRR images, the relative change of the specific surface (proportional to the amount of damage) in the course of tensile loading was analyzed. It could be shown that the damage can be detected by SXRR already at a stage of tensile loading, in which no observation of damage is possible with radiographic absorption-based imaging methods. Moreover, the quantitative analysis of the SXRR images reveals that the amount of damage increases homogeneously by an average of 25\% with respect to the initial state. To corroborate the experimental findings, the damage distribution was imaged in 3D after the final tensile loading by synchrotron X-ray refraction computed tomography (SXRCT) and absorption-based synchrotron X-ray computed tomography (SXCT). It could be evidenced that defects and damages cause pronounced indications in the SXRCT images.},
  language  = {en}
}