Search results for " pressure effect"
showing 3 items of 3 documents
EMBEDDED STRAIN GAUGES: EFFECT OF THE STRESS NORMAL TO THE GRID
2005
: In general, a strain gauge embedded in a model is subjected to a stress normal to the grid, whereas a gauge on the external surface is free from such a stress. This paper concerns the effect of the stress normal to the grid on the output of the strain gauge; usually, the influence of such a stress has a negligible effect, however, in some cases a notable influence has been noted. Therefore, the output of the strain gauge is determined in function of the strains in the plane of the gauge, ɛl and ɛt, and of the stress, σn, normal to the grid. The analysis shows that the output of the strain gauge is influenced by the coupled effect of transverse sensitivity and pressure sensitivity of the …
Evidence for a different electronic configuration as a primary effect during compression of orthorhombic perovskites: The case of NdM3+ O3 (M=Cr, Ga)
2018
(Mg,Fe)SiO3 perovskite is the most abundant mineral of the Earth's lower mantle, and compounds with the perovskite structure are perhaps the most widely employed ceramics. Hence, they attract both geophysicists and material scientists. Several investigations attempted to predict their structural evolution at high pressure, and recent advancements highlighted that perovskites having ions with the same formal valence at both polyhedral sites (i.e., 3+:3+) define different compressional patterns when transition metal ions (TMI) are involved. In this study, in situ high-pressure synchrotron XRD measurements coupled with ab initio simulations of the electronic population of NdCrO3 perovskite are…
Synthetic and natural chromium bearing spinels: an optical spectroscopy study
2014
Four samples of synthetic chromium-bearing spinels of (Mg, Fe2+)(Cr, Fe3+)2O4 composition and four samples of natural spinels of predominantly (Mg, Fe2+)(Al, Cr)2O4 composition were studied at ambient conditions by means of optical absorption spectroscopy. Synthetic end-member MgCr2O4 spinel was also studied at pressures up to ca. 10 GPa. In both synthetic and natural samples, chromium is present predominantly as octahedral Cr3+ seen in the spectra as two broad intense absorption bands in the visible range caused by the electronic spin-allowed 4A2g → 4T2g and 4A2g → 4T1g transitions (U- and Y-band, respectively). A distinct doublet structure of the Y-band in both synthetic and natural spine…