56,308 research outputs found
High-Voltage Electron Microscopy of the Early Stages of Recrystallization in CuMn
No full textCuMn-specimens were observed by HVEM to obtain information about the recrystallization process influenced by foreign atoms. Up to a concentration of 10 at.% Mn the SFE of this system does not change. Along the grain boundaries the orientations of the recrystallized grains and of the deformation microstructure were determined to establish the local orientation relationships. The grain orientations can be described by twinning of the deformation microstructure. Only 20-30° and 40-50° orientation relationships were found. Known from growth selection experiments these orientation relationships are already the final ones of the recrystallization texture. Because of the SFE and the large misfit between Cu and Mn these orientation relationships were formed rapidly after nucleation. Thus, the orientation formation process is finished after several æm of growth
Dedicated to the Memory of Professor Günter Wassermann
No full text- and -oriented copper single crystals were tensile deformed to a final strain of 20% and 4%, respectively. Specimens prepared from these crystals were abraded at one end. During the subsequent annealing treatment (750 K, 2 h for the -oriented crystals and 750 K, 90 min for the -oriented crystals) the recrystallization process started on this side. In both cases the orientation relationships between the largest recrystallized grains and the uniformly oriented deformed microstructure can be characterized by the following relations: 22.6° , 21.8° , 46.8° and 129.8° . Additionally, in the crystals other orientation relationships were found. This is caused by the different dislocation densities in the specimens. The -oriented crystals represent the early stage of recrystallization whereas the -oriented crystals show the orientations of the late recrystallization stage. Between these stages a further selection of orientations occur
Numismatic finds from the Roman site of Soline on Sv. Klement island in the Pakleni Archipelago near Hvar
No full textČlanak obrađuje numizmatičke nalaze koji su pronađeni tijekom arheoloških istraživanja rimske vile u uvali Soline na otoku Sv. Klement (Pakleni otoci, Hvar) u srednjoj Dalmaciji. Riječ je o 32 primjerka novca, od kojih su najstarije monete ilirskog kralja Baleja te rimski republikanski novac. Slijedi rimski carski novac, među kojim su najbrojniji kasnoantički primjerci, dok je najmlađa moneta kovana u Mletačkoj Republici. Tipološka, kulturno-povijesna, statistička te kontekstualna analiza ovih nalaza omogućava bolje razumijevanje kronologije ljudskih aktivnosti u okviru prirodnog i kulturnog krajolika otoka Sv. Klement te ujedno pridonosi poznavanju optjecaja najstarijeg novca, pa tako i gospodarsko-političkih prilika na prostoru srednje Dalmacije.The article analyzes the coins found during archaeological excavations at a Roman villa in Soline Cove on the island of Sv. Klement in the Pakleni Archipelago off the Central Dalmatian island of Hvar. The earliest among the 32 coins found there are the coins of Illyrian King Ballaios and Roman Republican coins. Then follow Roman Imperial coins (with the ones from Late Antiquity being the most numerous) and a coin struck in the Venetian Republic. The typological, cultural-historical, statistical and contextual analyses of these finds can help us better understand the chronology of human activities in the natural and cultural landscape of the island of Sv. Klement and improve our knowledge of the circulation of the earliest coins and economic and political situation in Central Dalmatia of the day
Recrystallization Experiments in Tensile Deformed <100>-Oriented Single Crystals of Copper-Phosphorus and Copper-Manganese Alloys
No full textThe recrysallization process in specimens of dilute CuP and CuMn alloys was investigated to determine those orientation relationships between recrystallized grains and deformation microstructure, which favour rapid grain growth. The specimens were prepared from tensile deformed -oriented single crystals. In the CuP alloy the largest recrystallized grains have near 20° or 53° orientation relationships to the deformation microstructure. In the CuMn alloy only the two orientation relationships 30° and 48° were found
A Dynamic Subfilter-scale Stress Model for Large Eddy Simulations Based on Physical Flow Scales
No full textWe propose a new definition of the length scale in an eddy-viscosity model for large-eddy simulations (LES). This formulation extends and generalizes a previous proposal [Piomelli, Rouhi and Geurts, Proc. ETMM10, 2014], in which the LES length scale was expressed in terms of the integral length-scale of turbulence determined by the flow characteristics and explicitly decoupled from the simulation grid; this approach was named Integral Length-Scale Approximation (ILSA). As in the original ILSA, the model coefficient was determined by the user, and required to maintain a desired contribution of the unresolved, subfilter scales (SFS) to the global transport. We propose a local formulation (local ILSA) in which the model coefficient is local in space, allowing a precise control over SFS activity as a function of location. This new formulation preserves the properties of the global model; application to channel flow and backward-facing step verifies its features and accuracy
Large-eddy simulation of a separated flow with a sub-filter scale model based on the integral length-scale
No full textA new sub-filter scale model for large-eddy simulations, which uses a length-scale proportional to the integral scale of the turbulence instead of the grid resolution to parametrize the modelled stresses, will be assessed in the prediction of the flow of a boundary-layer over a rough surface, which includes separation and reattachment
Near Wall PIV-Measurements on the Windward Slope of a Hill
No full textThe turbulent flow over periodic hills was measured near to the wall, using planar Particle-Image-Velocimetry (PIV) at high spatial resolution. Our focus is on the near wall turbulence structure on the windward slope of the hill. For large-eddy simulation (LES) we suspect that, if this was not predicted accurately, it affects the prediction of the velocity profiles over the hill crest which in turn will affect the recirculation length downstream of the hill. Regarding the time averaged velocities, we were able to resolve the linear viscous region of the boundary layer. The velocity distribution and also the Reynolds stress does not comply with the law of the wall as it is valid for a turbulent boundary layer at equilibrium
Energy dissipation and flux laws for unsteady turbulence
No full textDirect Numerical Simulations of spatially periodic unsteady turbulence show that the high Reynolds number scalings of the instantaneous energy dissipation rate and interscale energy flux at intermediate wavenumbers are qualitatively different from the well-known cornerstone scalings of equilibrium turbulence where and are time-dependent rms velocity and integral length-scales. Instead, they both scale as where and are length and velocity scales characterizing initial/overall unsteady turbulence conditions
Direct numerical simulation of turbulent Couette-Poiseuille flow with zero skin friction
No full textThe near-wall scaling of mean velocity U(y) is addressed for the case of zero skin friction on one wall of a fully turbulent channel flow. The present DNS results can be added to the evidence in support of the conjecture that U is proportional to √yw in the region just above the wall at which the mean shear dU/dy = 0
Real-space Manifestations of Bottlenecks in Turbulence Spectra
No full textAn energy-spectrum bottleneck, a bump in the turbulence spectrum between the inertial and dissipation ranges, is shown to occur in the non-turbulent, one-dimensional, hyperviscous Burgers equation and found to be the Fourier-space signature of oscillations in the real-space velocity, which are explained by boundary-layer-expansion techniques. Pseudospectral simulations are used to show that such oscillations occur in velocity correlation functions in one- and three-dimensional hyperviscous hydrodynamical equations that display genuine turbulence
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