4th International Congress on 3D Materials Science (3DMS) 2018: Porous and Nanostructured Materials II
Program Organizers: Hugh Simons, Denmark Technical University; Henning Poulsen, Denmark Technical University; David Rowenhorst, Naval Research Laboratory; Peter Voorhees, Northwestern University; Satoshi Hata, Kyushu Univ; McLean Echlin, UC Santa Barbara
Tuesday 1:30 PM
June 12, 2018
Room: Lille Scene
Location: Kulturværftet (Culture Yard) Conference Center
Session Chair: Ashley Spear, University of Utah
1:30 PM Invited
Correlating 3D Structural Characteristics to Micro-mechanical Behavior of Nanoporous Gold: Erica Lilleodden1; Kaixiong Hu; Markus Ziehmer; 1Helmholtz-Zentrum Geesthacht
The mechanical behavior of NPG has been shown to be strongly dependent on its average ligament width, with local stresses approaching the theoretical strength of gold, underscoring the “smaller is stronger” paradigm. Such size-dependent strength can be exploited in NPG through targeted annealing in order to tailor the structural length-scales. Yet strong deviations from classical laws for cellular structures have been found for NPG, pointing to the need for developing new scaling laws for the prediction of mechanical properties as a function of structural length. This in turn is reliant on a more detailed investigation of the 3D network structure and crystallographic domain sizes, and a better understanding of the underlying structure-property relations governing mechanical response. By employing a combination of high-resolution tomographic characterization, micro-Laue diffraction and in situ micromechanical testing, the structure-property relations and mechanisms of deformation of this NPG have been explored and quantified. Using focused ion beam (FIB) based tomography applied to as-dealloyed and isothermally annealed NPG samples, we show that the ligament width distributions coarsen in a sufficiently self-similar, time-invariant manner, while the scaled connectivity density shows a self-similar ligament network topology, best described as a load-bearing ring structure. Such a ring structure has been quantified through an analysis of the mean principal curvatures, results from which are correlated to observations from in situ micromechanical experiments showing that the ring structure – rather than the solid volume fraction – governs structural stiffness.
Quantifying Enhanced Oil Recovery in Synthetic Media with MicroCT: Sidnei Paciornik1; Kamila Scheffer1; Marcio Carvalho1; Yves Méheust2; 1PUC-Rio; 2Université Rennes 1
Enhanced oil recovery methods are tested and optimized in synthetic media, emulating porosity and permeability of real oil-bearing rocks. Such a medium was produced with sintered bi-disperse glass beads and microCT images (4 µm resolution) were acquired at different stages of fluid motion through the medium. Synthetic seawater with or without oil/water emulsion was used to recover oil previously saturating the medium´s pores. The water was doped with KI to fine tune X-ray absorption. Thus, 3D images showing the beads, doped water and residual oil presented a 3-modal histogram. After denoising with a non-local means filter, the images were segmented and the distribution of residual oil ganglia was visualized and quantified. Probability density functions of volumes (~10^4 ganglia spanning 8 orders of magnitude) show well defined exponential behaviors for the displacement of oil by water, while the use of emulsions provides better recovery efficiency with larger numbers of larger ganglia.
Analysis of Cone Penetration Tests in Snow with X-ray Tomography: Isabel Peinke1; P. Hagenmuller1; E. Ando2; F. Flin1; G. Chambon3; J. Roulle1; 1Météo-France - CNRS; 2UGA, CNRS; 3UGA, Irstea
Cone penetration tests (CPT) are common to get vertical profiles of snow hardness. To link the measured penetration strength, especially its high-frequency fluctuations, to microstructural snow characteristics such as grain size or density, it is necessary to understand the processes occurring next to the cone tip. Indeed, the snow closed to the cone tip gets compacted during the indentation, which affects the strength measurements. To decipher this link, we combined 3D micro-tomography imaging of snow and highly-resolved CPTs. Several samples spanning different snow types were imaged twice at a resolution of 15 microns: once before and once after a CPT. We developed an algorithm to fully recover and quantify the displacements between the pre-CPT and post-CPT images, which is a difficult task due to the presence of very large discontinuous displacements. The method combines image correlation and grain matching based on morphological criteria. The 3D displacement field will give us information of the re-organization of the bonds and thus new insights to interpret CPT in terms of microstructural characteristics.
X-ray CT Based 3D Characterization of Closed-cell Aluminium Foams to Explore the Structure-property Relationship during Impact: Mohammad Saadatfar1; Abdul Kader2; 1Australian National University; 2University of New South Wales
Closed-cell aluminium foams are mostly used to mitigate the impact and blast load in order to safe products and personnel. The mechanical properties including the impact energy absorption capacity of foams are the direct consequences of their topological/geometrical collapse mechanisms during impact. In the present study, interrupted drop-weight impact experiments have been conducted to investigate the deformation evolution/collapse mechanisms of closed-cell aluminium foams. The sample has been compressed with total 21 interrupted drop impacts at strain rate ~ 40 s-1 and the post impacted samples have been imaged at four different strain states with high-resolution x-ray computed tomography. Our results show that the deforming microstructure creates strong correlations across a range of geometrical and shape characteristics. Further, we show that the deformation mechanism leaves topological signatures in the evolving microstructure, which can be used to better understand the mechanical response of the specimen at various stages of impact-deformation.
Stress Test of a PVC Sample – DVC and Pore Network Modeling Analysis: Cornelia Vacar1; 1Thermofisher Scientific
This study analyzes the effect of applying an increasing pressure on a PVC sample. The deformation of the sample through time is studied as it extends due to applying increasing amounts of load. Once a critical amount of load is reached, the material tears. By looking at the structure of the material (porous plastic) we can anticipate based on the pore density, the pore size and throat size where the tear is more likely to appear. Moreover, by applying a Digital Volume Correlation analysis and studying how the forces are distributed in the volume, we investigate a potential relation between the Pore Network Model of the material and the stress distribution in the volume. The PNM and the DVC are computed using the Avizo software and the data is provided by Shimadzu Techno-Research, Inc.
3:20 PM Break