Area Fraction Distribution Research Articles

Nuevo modelo para la predicción de la microestructura final y los parámetros de recristalización dinámica de materiales metálicos policristalinos. Aplicación a la aleación de magnesio AZ31

The study starts from a new constitutive equation able to reproduce the stress-strain curves for each strain rate and temperature. Using this equation, the characteristic parameters of dynamic recrystallization for each of the flow curves can be obtained. An experimental study of final grain sizes, their frequency and distribution and area fractions has been made. These parameters together with those mentioned above allow establishing predictive models for the final microstructure conditions of polycrystalline metallic materials. These models have been applied to the hot deformation of AZ31 magnesium alloy. Mean final grain sizes, area fraction distributions and their frequency are predicted. In addition, the characteristic dynamic recrystallization parameters of the material that constitute elements of control of the deformation process are also predicted.

Flow-induced melting of condensed domains within a dispersed Langmuir film

During phase transition from the liquid-expanded to the liquid-condensed state, a dispersed Langmuir film of pentadecanoic acid is submitted to an annular shear flow of moderate Reynolds number (Re=10–100). The mesoscopic morphology of this two-phase Langmuir film is investigated based on area fraction distribution of the condensed phase after a permanent regime is established. The distribution demonstrates radially inwards packing along the liquid surface induced by centripetal flow originating from centrifugation of the subphase along the rotating floor. For a growing level of centrifugation, a circular Reynolds ridge arises along the liquid surface. The Langmuir film experiences a strong morphological transition driven by a balance between surface shear and reduced line tension. As a result, a shear-induced melting of the condensed domains generates a new patterning which can be described as a regular and monodispersed matrix of tiny condensed droplets.

Solid area fraction distribution of solid–liquid food mixtures during flow through a straight tube

The solid area fraction (areal porosity) distribution within a tube during continuous flow was determined experimentally. Cubes, rectangular prisms and cylinders (potato and green beans) at volume fractions of 30% and 50% in a 5% agar solution were tested. The flowing mixture was rapidly immobilized by cooling-induced gelation. Samples were then sliced to determine solids area fractions. Results of the solid fraction distribution showed a normal distribution. Increasing solid concentration flattened the distribution. The solid concentration was the only significant factor that affected both the area and flowing solid volume fraction. Solid volume fraction always was lower than solid area fraction. The aspect ratio and the shape effect were not statistically significant but they had slight effects on the mean and standard deviation. Rectangular solids exhibited lower solid area fraction and flattened the distribution more than cylinders at high solid concentration.

Permeability of periodic porous media

The permeability of the two-dimensional periodic arrays of cylinders is obtained numerically as a function of the dimensionless wave number $\mathrm{kD}$, where k is the wave number based on the distance between particles in the streamwise direction and D is the diameter. To isolate the $\mathrm{kD}$ dependence, D and the porosity are held fixed. The latter is achieved by making the product of distance between particles in the cross-stream and streamwise directions constant. The numerical results show that the permeability increases with $\mathrm{kD}$, but the increase is not monotonic. In particular, the permeability decreases for $\ensuremath{\sim}5<\mathrm{kD}<\ensuremath{\sim}7.7$, and becomes locally minimum at $\mathrm{kD}\ensuremath{\approx}7.7$. This value of $\mathrm{kD}$ is significant because it is the smallest wave number for which the streamwise area-fraction spectrum is zero. For $\mathrm{kD}<5$ and $7.7<\mathrm{kD}<11$, the permeability increases with $\mathrm{kD}$. Our numerical simulations also show that for $\mathrm{kD}\ensuremath{\approx}7.7$ the pressure distribution in the cross-stream direction is relatively flat which again is a consequence of the fact that the area-fraction distribution in the flow direction is approximately constant.