The X-ray microtomography lab at Luleå University of Technology (LTU), Sweden shares interesting insights
The snow sample represents fresh snow acquired only minutes after snowfall. The width of the snow crystal is approximately 0.85 mm. The width (diameter) of the center tunnel ranges from 60 micron (at the entrance) to 220 micron on the opposite side.
The sample bed was 6 mm in diameter and 5 mm in height (initially). The scans were carried out using a spatial resolution of 4 micron. The in-situ loading was carried out using a Deben CT5000TEC load stage with a 500 N load cell. Four XMT scans were acquired along the load cycle 0N-10N-18N-25N, at a constant temperature of -15°C. Quantitative analysis of microstructure (shape of crystals, porosity etc.) was obtained from 3D image analysis using the software Dragonfly Pro (ORS), and the compaction of the snow bed was analyzed by digital volume correlation (DVC) using software from LaVision.
One great benefit of using the Deben stage is the flexibility in using different load cells depending on material and application. The software interface is also easy to use and supported by the Scout and Scan software from ZEISS that is used for control of ZEISS Xradia Versa.
A recent study that we are very proud of is 3D quantitative in-situ imaging of micro scale snow crystals and how they respond to compaction. This study was quite challenging, and required a lot of careful planning, but turned our very well. It’s received a lot of positive feedback from both the scientific community as well as from media. In fact, the first results from this study were broadcast on national television (in Sweden) only a few hours after performing the scans. These measurements would have been hard to achieve without the Deben CT5000TEC stage as they required precise control of both the mechanical load and the temperature (freezing capability) at the same time.
Fredrik Forsberg, Associate Senior Lecturer , Luleå University of Technology
Conclusions: 3D quantitative analysis of snow compaction
X-ray microtomography and digital volume correlation allows the researchers at LTU to perform quantitative in-situ studies of snow compaction. These tools also allow them to study the compaction process at multiple spatial scales – global phenomena and grain-to-grain interactions.
X-ray microtomography and the use of a load stage with temperature control, such as Deben CT 5000TEC, allows studies of snow crystal microstructure and snow compaction behaviour in a way that until recently had not been possible.
About the X-ray microtomography lab at Luleå University of Technology (LTU), Sweden
The research goal at the X-ray microtomography lab at LTU, Sweden is to develop methods and tools that help us better understand heterogeneous materials and how they behave in different environments, and at different spatial scales.
A new state-of-the-art X-ray microtomography system was installed at LTU in 2016. The 3D imaging system – ZEISS Xradia 510 Versa – together with the Deben CT5000TEC in-situ load module, which allows both mechanical and thermal loading, is completely unique in Sweden. It enables 3D in-situ imaging and characterization of materials, including minerals, rocks, metals, composites and wood, with sub-micron resolution. From the acquired 3D data, it is possible to make a quantitative characterization of internal features such as porosity, cracks, grains, fibers etc., as well as determine material deformation and strain.