Multiscale analysis of piezoelectric material by using EBSD-measured realistic model

Material properties of a polycrystal piezoelectric ceramic, a barium titanate BaTiO3, were analyzed by the two-scale crystallographic homogenization method. Threedimensional (3-D) micro-finite element (FE) model was constructed based on the electron backscatter diffraction (EBSD) measured crystal orientation distribution images. The images are piled up to a 3-D voxel data of crystal orientation distribution by repeating mechanically and chemically polishing, and EBSD measurement of the ceramic. We obtained 13 EBSD images of 128×100 pixels, which measurement interval was 0.635μm in-plane and the average amount of polishing was 1.66μm in thickness (normal) direction of specimen. Each voxel of EBSD was assigned into 8-node solid FE in-plane with maintaining resolution of EBSD measurement, and was divided into three FEs along thickness direction with same crystal orientation, because of improvement of aspect ratio of FE. The total number of FEs was 499,200 (=128×100×13×3) which corresponded to over two millions degrees of freedom. In order to realize a large-scale micro-analysis using EBSD-measured voxel FE model, the coupled problem of the piezoelectric material was solved by parallel conjugate gradient (CG) method combined with the block Gauss-Seidel (BGS) method. The coupled micro-FE equation to obtain characteristic function vectors was separated into two linear equations, such as the elastic deformation and electrostatic analyses, by employing the BGS method, and then the equations were solved by the parallel CG solver while substituting coupling terms each other. Therefore, nested iterative scheme was constructed on a PC cluster. In addition, the representative volume element (RVE) size was determined based on the orientation distribution function analyses of EBSD voxel data. The least RVE size was 25,000μm3, which corresponded to include 150 crystal grains

Highly Stretchable Stress-Strain Sensor from Elastomer Nanocomposites with Movable Cross-links and Ketjenblack

Practical applications like very thin stress-strain sensors require high strength, stretchability, and conductivity, simultaneously. One of the approaches is improving the toughness of the stress-strain sensing materials. Polymeric materials with movable cross-links in which the polymer chain penetrates the cavity of cyclodextrin (CD) demonstrate enhanced strength and stretchability, simultaneously. We designed two approaches that utilize elastomer nanocomposites with movable cross-links and carbon filler (ketjenblack, KB). One approach is mixing SC (a single movable cross-network material), a linear polymer (poly(ethyl acrylate), PEA), and KB to obtain their composite. The electrical resistance increases proportionally with tensile strain, leading to the application of this composite as a stress- strain sensor. The responses of this material are stable for over 100 loading and unloading cycles. The other approach is a composite made with KB and a movable cross-network elastomer for knitting dissimilar polymers (KP), where movable cross-links connect the CD-modified polystyrene (PSCD) and PEA. The obtained composite acts as a highly sensitive stress-strain sensor that exhibits an exponential increase in resistance with increasing tensile strain due to the polymer dethreading from the CD rings. The designed preparations of highly repeatable or highly responsive stress-strain sensors with good mechanical properties can help broaden their application in electrical devices

Hyper-IgG4 disease: report and characterisation of a new disease

BACKGROUND: We highlight a chronic inflammatory disease we call 'hyper-IgG4 disease', which has many synonyms depending on the organ involved, the country of origin and the year of the report. It is characterized histologically by a lymphoplasmacytic inflammation with IgG4-positive cells and exuberant fibrosis, which leaves dense fibrosis on resolution. A typical example is idiopathic retroperitoneal fibrosis, but the initial report in 2001 was of sclerosing pancreatitis. METHODS: We report an index case with fever and severe systemic disease. We have also reviewed the histology of 11 further patients with idiopathic retroperitoneal fibrosis for evidence of IgG4-expressing plasma cells, and examined a wide range of other inflammatory conditions and fibrotic diseases as organ-specific controls. We have reviewed the published literature for disease associations with idiopathic, systemic fibrosing conditions and the synonyms: pseudotumour, myofibroblastic tumour, plasma cell granuloma, systemic fibrosis, xanthofibrogranulomatosis, and multifocal fibrosclerosis. RESULTS: Histology from all 12 patients showed, to varying degrees, fibrosis, intense inflammatory cell infiltration with lymphocytes, plasma cells, scattered neutrophils, and sometimes eosinophilic aggregates, with venulitis and obliterative arteritis. The majority of lymphocytes were T cells that expressed CD8 and CD4, with scattered B-cell-rich small lymphoid follicles. In all cases, there was a significant increase in IgG4-positive plasma cells compared with controls. In two cases, biopsies before and after steroid treatment were available, and only scattered plasma cells were seen after treatment, none of them expressing IgG4. Review of the literature shows that although pathology commonly appears confined to one organ, patients can have systemic symptoms and fever. In the active period, there is an acute phase response with a high serum concentration of IgG, and during this phase, there is a rapid clinical response to glucocorticoid steroid treatment. CONCLUSION: We believe that hyper-IgG4 disease is an important condition to recognise, as the diagnosis can be readily verified and the outcome with treatment is very good