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Equivalent Diameter (equivalent + diameter)

Distribution by Scientific Domains
Polymers and Materials Science40%

Selected Abstracts

Suppression of Ni4Ti3 Precipitation by Grain Size Refinement in Ni-Rich NiTi Shape Memory Alloys,

ADVANCED ENGINEERING MATERIALS, Issue 8 2010
Egor A. Prokofiev
Severe plastic deformation (SPD) processes, such as equal channel angular pressing (ECAP) and high pressure torsion (HPT), are successfully employed to produce ultra fine grain (UFG) and nanocrystalline (NC) microstructures in a Ti,50.7,at% Ni shape memory alloy. The effect of grain size on subsequent Ni-rich particle precipitation during annealing is investigated by transmission electron microscopy (TEM), selected area electron diffraction (SAD, SAED), and X-ray diffraction (XRD). It is observed that Ni4Ti3 precipitation is suppressed in grains of cross-sectional equivalent diameter below approximately 150,nm, and that particle coarsening is inhibited by very fine grain sizes. The results suggest that fine grain sizes impede precipitation processes by disrupting the formation of self-accommodating particle arrays and that the arrays locally compensate for coherency strains during nucleation and growth. [source]

Microstructure evolution in age-hardenable aluminium alloy during processing by hydrostatic extrusion

JOURNAL OF MICROSCOPY, Issue 1 2006
M. LEWANDOWSKA
Summary In the present work, scanning and transmission electron microscopy were used to investigate the microstructural evolution occurring during the hydrostatic extrusion of an age-hardenable aluminium alloy. It was shown that processing by hydrostatic extrusion leads to grain refinement to 95 nm in equivalent diameter. Hydrostatic extrusion also influences the geometrical parameters of two different types of particle: intermetallic inclusions and precipitates. The intermetallic inclusions slightly decrease in mean equivalent diameter, but their size remains at the micrometre level. The precipitates are fragmented to nanoscale spherical particles, and their evolution delays the process of grain refinement. [source]

A Simple Approximate Formula for the Aspect Ratio of Oblate Particles

PARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 6 2007
Willi Pabst
Abstract A simple approximative formula is derived, which can be used to quantify the shape of oblate particles or an average shape of the corresponding particle system, when the results of sedimentation analysis (Stokes equivalent diameters) are known and results from either microscopic image analysis (assuming stable orientation, i.e., with the plane perpendicular to the direction of observation) or laser diffraction (assuming random orientation) are available for the same sample. In the latter case Cauchy's stereological theorem is applied to account for random orientation. Furthermore, it is shown that for sufficiently large aspect ratios, this formula is very close to the well-known Jennings-Parslow relation and can replace this more complicated expression in many practical cases, e.g., in the routine characterization of ceramic raw materials (kaolins and oxide or non-oxide platelet powders). [source]

Momentum Balance for Two-Phase Horizontal Pipe Flow Part 1: Friction Factors

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1-2 2004
P. L. Spedding
Estimations of gas wall, liquid wall and interfacial friction factors for two-phase horizontal co-current pipe flow are discussed critically after being checked against reliable data obtained under a wide range of conditions. The use of equivalent diameters and the Blasius relation were shown to be valid for estimation of the gas wall friction. Prediction of liquid wall and interfacial friction factors proved to be more difficult but estimation improved if consideration was given to the effects of liquid holdup and interfacial liquid shape. [source]