Visualization Of Pores Research Articles

Role of inherent anisotropy in infiltration mechanism of suffusion with irregular granular skeletons

Suffusion, the process of particle migration and clogging within porous media, exerts a remarkable impact on various natural and engineered systems. Properties of the coarse-grained skeletons are crucial during suffusion, while the influence of the inherent anisotropy remains insufficiently explored. In this study, numerical model using the coupled computational fluid dynamics and the discrete element method (CFD-DEM) is performed to simulate the suffusion evolution of different fabric anisotropy configurations under controlled flow conditions. Granular skeletons are generated considering different initial rotational degrees of freedom (RDoFs) and orientations of irregular coarse particles, based on which the motion mechanism of migratory fines is investigated. The infiltration process is quantified by multi-scale parameters, including particle distribution, velocity evolution, visualization of pores and throats, force network, contact statistics and anisotropic characteristics. The results illustrate the non-negligible influence of inherent anisotropy on pore structure, consequently impacting the motion behavior of fine particles and the stress transmission within the granular skeletons. Such insights will contribute to advancing a fundamental understanding of suffusion, which enables the development of effective strategies for predicting and controlling in geotechnical and environmental engineering catastrophes.

Determination of pore types in coquinas carbonates and their effects on formation factors and porosity exponents

ABSTRACT Calculation of the saturation of carbonates with various pore types and complicated pore structures in electrical resistivity models requires data on pore types and their effects on electrical resistivity. Therefore, the objectives are to determine the pore types and to investigate their effects on electrical resistivity. The pore types of three coquinas samples were determined by the distributions of experimental porosities and porosity exponents in the cross-plot of the dual porosity model and pore visualization from X-ray computerized tomography. A process-based method was applied to reconstruct the pore-scale models with different pore types. Their pore networks and electrical resistivity were extracted and calculated by the maximal ball and finite element methods, respectively. Fracture reduced the formation factor and porosity exponent. Connected vug increased the pore space that swept by the electrical current to reduce the formation factor while increasing the porosity exponent. Isolated vug undermined the pore space to increase the formation factor and porosity exponent. The effects of the tiny vug were much more obvious than the effects of the large one. This investigation will help to classify the pore types and propose electrical resistivity models that correspond to specific pore types and vug sizes in carbonate reservoirs.

Three-dimensional (3D) microstructural characterization and quantification of reflow porosity in Sn-rich alloy/copper joints by X-ray tomography

Abstract In this paper high resolution X-ray tomography was used to characterize reflow porosity in Sn–3.9Ag–0.7Cu/Cu solder joints. The combination of two segmentation techniques was applied for the three-dimensional (3D) visualization of pores in the joints and the quantification on the characteristics of reflow porosity, including pore size, volume fraction and morphology. The size, morphology and distribution of porosity were visualized in 3D for three different solder joints. Since the results are relatively similar for all three, only the results of one joint are presented. Solder reflow porosity was mostly spherical, segregated along the solder/Cu interface, and had an average pore size of 30 μm in diameter. A few large pores (larger than 100 μm in diameter) were present, some of which had lower sphericity, i.e., they were more irregular. The presence of these large pores may significantly influence the mechanical behavior of solder joints.

Three-dimensional (3D) visualization of reflow porosity and modeling of deformation in Pb-free solder joints

The volume, size, and dispersion of porosity in solder joints are known to affect mechanical performance and reliability. Most of the techniques used to characterize the three-dimensional (3D) nature of these defects are destructive. With the enhancements in high resolution computed tomography (CT), the detection limits of intrinsic microstructures have been significantly improved. Furthermore, the 3D microstructure of the material can be used in finite element models to understand their effect on microscopic deformation. In this paper we describe a technique utilizing high resolution (< 1 µm) X-ray tomography for the three-dimensional (3D) visualization of pores in Sn-3.9Ag-0.7Cu/Cu joints. The characteristics of reflow porosity, including volume fraction and distribution, were investigated for two reflow profiles. The size and distribution of porosity size were visualized in 3D for four different solder joints. In addition, the 3D virtual microstructure was incorporated into a finite element model to quantify the effect of voids on the lap shear behavior of a solder joint. The presence, size, and location of voids significantly increased the severity of strain localization at the solder/copper interface.

Visualization of pores (export sites) correlated with cellulose production in the envelope of the gram-negative bacterium Acetobacter xylinum.

The Gram-negative bacterium Acetobacter xylinum assembles a cellulse ribbon composed of a number of microfibrils in the longitudinal axis of its envelope. The zone of ribbon assembly was investigated by freeze-etch electron microscopy. Freeze-etching revealed, beneath the cellulose ribbons, a linear array of pores on the lipopolysaccharide membrane. These pores have a rim diameter of 120--150 A and a central hole or deepening of approximately 35 A. The axes of pore arrays closely coincide with linear arrays of 100 A particles on the E- and P-faces of the fractured lipopolysaccharide membranes. Pores and particles in the lipopolysaccharide membrane are probably congruent. The pores are hypothesized to be the export sites (penetration sites) for cellulose.