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Mechanics of Ice and Snow as a Granular Material
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.ORCID-id: 0000-0001-6231-8944
2024 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

In this thesis, the mechanical properties of ice and dry snow as a class of granular materials are investigated through a series of experiments, analyses, and simulations. The primary focus is on understanding the intricate details of ice sintering, capillary bridge formation, and the behavior of snow under varying conditions.

The investigation into ice sintering reveals a formulation of the sintering force, considering temperature, pressing force, contact duration, and particle size during the primary sintering stage. The results indicate a nearly linear increase in sintering force with external pressing force, while dependency on contact duration and particle size follows a nonlinear power-law relationship. The temperature dependence of the sintering force is nonlinear, aligning with the Arrhenius equation. The ultimate tensile strength of ice and the axial stress concentration factor are identified as crucial factors in determining the sintering force. Additionally, observations near the melting point reveal the formation of a liquid bridge between contacted ice particles.

Moving on to capillary bridge formation, the experiments demonstrate the presence of a liquid bridge between an ice particle and a smooth (or rough) aluminum surface at controlled temperature conditions. The separation distance is found to be proportional to the cube root of the bridge volume, which decreases with decreasing temperature. Notably, for a rough surface, capillary bridge formation diminishes under the considered experimental conditions.

The significance of snow in various contexts prompts an exploration of its mechanical properties. Utilizing micro-computed tomography imaging and quasi-static mechanical loading, a methodology for mapping the density-dependent material properties of manufactured snow is established. The study investigates structural parameter variations during loading, revealing insights into the three-dimensional structure, relative density, and mechanical behavior of snow. Results from Burger’s model show an increasing trend in modulus and viscosity terms with density. Digital volume correlation aids in calculating full-field strain distribution, highlighting particle characteristics and changes in specific surface areas during loading.

Expanding the scope to natural snow, cutting-edge techniques like micro-tomography are integrated with traditional loading methods. Employing CT imaging and uniaxial compression tests, along with digital volume correlation, density-dependent material properties are analyzed. The study incorporates two snow samples, revealing density-dependent trends in modulus and viscosity terms. The results provide valuable insights into the non-homogeneous behavior of natural snow and contribute to fields such as glacier dynamics and avalanche prediction.

Finally, the discrete element method with a variable bond model is used to simulate the behavior of granular materials, specifically focusing on snow. The model incorporates temperature dependent cohesion and effectively captures the angle of repose and stress-strain behavior of snow.

In summary, this thesis presents an investigation into the mechanical properties of ice, capillary bridge formation, manufactured snow, natural snow, and granular materials, providing insights and contributing to the understanding of ice and snow in various environmental and engineering contexts.

sted, utgiver, år, opplag, sider
Luleå: Luleå University of Technology, 2024.
Serie
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
Emneord [en]
micro tomography, mechanics, ice and snow, sintering force, thin liquid layer, discrete element method
HSV kategori
Forskningsprogram
Experimentell mekanik
Identifikatorer
URN: urn:nbn:se:ltu:diva-105285ISBN: 978-91-8048-558-6 (tryckt)ISBN: 978-91-8048-559-3 (digital)OAI: oai:DiVA.org:ltu-105285DiVA, id: diva2:1855122
Disputas
2024-06-12, E632, Luleå University of Technology, Luleå, 10:00 (engelsk)
Opponent
Veileder
Tilgjengelig fra: 2024-04-29 Laget: 2024-04-29 Sist oppdatert: 2024-05-22bibliografisk kontrollert
Delarbeid
1. Ice sintering: Dependence of sintering force on temperature, load, duration, and particle size
Åpne denne publikasjonen i ny fane eller vindu >>Ice sintering: Dependence of sintering force on temperature, load, duration, and particle size
Vise andre…
2022 (engelsk)Inngår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 131, nr 2, artikkel-id 025109Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

We present experiments along with an approximate, semi-analytic, close-form solution to predict ice sintering force as a function of temperature, contact load, contact duration, and particle size during the primary stage of sintering. The ice sintering force increases nearly linear with increasing contact load but nonlinear with both contact duration and particle size in the form of a power law. The exponent of the power law for size dependence is around the value predicted by general sintering theory. The temperature dependence of the sintering force is also nonlinear and follows the Arrhenius equation. At temperatures closer to the melting point, a liquid bridge is observed upon the separation of the contacted ice particles. We also find that the ratio of ultimate tensile strength of ice to the axial stress concentration factor in tension is an important factor in determining the sintering force, and a value of nearly 1.1 MPa can best catch the sintering force of ice in different conditions. We find that the activation energy is around 41.4KJ/mol41.4KJ/mol, which is close to the previously reported data. Also, our results suggest that smaller particles are “stickier” than larger particles. Moreover, during the formation of the ice particles, cavitation and surface cracking is observed which can be one of the sources for the variations observed in the measured ice sintering force.

sted, utgiver, år, opplag, sider
American Institute of Physics (AIP), 2022
HSV kategori
Forskningsprogram
Experimentell mekanik
Identifikatorer
urn:nbn:se:ltu:diva-88792 (URN)10.1063/5.0073824 (DOI)000746515900007 ()2-s2.0-85123639304 (Scopus ID)
Merknad

Validerad;2022;Nivå 2;2022-01-17 (johcin)

Tilgjengelig fra: 2022-01-17 Laget: 2022-01-17 Sist oppdatert: 2024-05-06bibliografisk kontrollert
2. Capillary Bridge in Contact with Ice Particles Can Be Related to the Thin Liquid Film on Ice
Åpne denne publikasjonen i ny fane eller vindu >>Capillary Bridge in Contact with Ice Particles Can Be Related to the Thin Liquid Film on Ice
Vise andre…
2024 (engelsk)Inngår i: Journal of cold regions engineering, ISSN 0887-381X, E-ISSN 1943-5495, Vol. 38, nr 1, artikkel-id 04023021Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

We experimentally demonstrate the presence of a capillary bridge in the contact between an ice particle and a smooth aluminum surface at a relative humidity of approximately 50% and temperatures below the melting point. We conduct the experiments in a freezer with a controlled temperature and consider the mechanical instability of the bridge upon separation of the ice particle from the aluminum surface at a constant speed. We observe that a liquid bridge forms, and this formation becomes more pronounced as the temperature approaches the melting point. We also show that the separation distance is proportional to the cube root of the volume of the bridge. We hypothesize that the volume of the liquid bridge can be used to provide a rough estimate of the thickness of the liquid layer on the ice particle since in the absence of other driving mechanisms, some of the liquid on the surface must have been pulled to the bridge area. We show that the estimated value lies within the range previously reported in the literature. With these assumptions, the estimated thickness of the liquid layer decreases from nearly 56 nm at T = −1.7°C to 0.2 nm at T = −12.7°C. The dependence can be approximated with a power law, proportional to (TM − T)−β, where β < 2.6 and TM is the melting temperature. We further observe that for a rough surface, the capillary bridge formation in the considered experimental conditions vanishes.

sted, utgiver, år, opplag, sider
American Society of Civil Engineers (ASCE), 2024
HSV kategori
Forskningsprogram
Experimentell mekanik
Identifikatorer
urn:nbn:se:ltu:diva-102441 (URN)10.1061/JCRGEI.CRENG-738 (DOI)001143507100005 ()2-s2.0-85175442634 (Scopus ID)
Merknad

Validerad;2023;Nivå 2;2023-11-15 (sofila);

Full text license: CC BY

Tilgjengelig fra: 2023-11-13 Laget: 2023-11-13 Sist oppdatert: 2024-05-06bibliografisk kontrollert
3. Mapping of density-dependent material properties of dry manufactured snow using μCT
Åpne denne publikasjonen i ny fane eller vindu >>Mapping of density-dependent material properties of dry manufactured snow using μCT
Vise andre…
2024 (engelsk)Inngår i: Applied Physics A: Materials Science & Processing, ISSN 0947-8396, E-ISSN 1432-0630, Vol. 130, artikkel-id 16Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Despite the significance of snow in various cryospheric, polar, and construction contexts, more comprehensive studies are required on its mechanical properties. In recent years, the utilization of μ CT has yielded valuable insights into snow analysis. Our objective is to establish a methodology for mapping density-dependent material properties for dry manufactured snow within the density range of 400–600 kg/m 3 utilizing μ CT imaging and step-wise, quasi-static, mechanical loading. We also aim to investigate the variations in the structural parameters of snow during loading. The three-dimensional (3D) structure of snow is captured using μ CT with 801 projections at the beginning of the experiments and at the end of each loading step. The sample is compressed at a temperature of − 18 o C using a constant rate of deformation (0.2 mm/min) in multiple steps. The relative density of the snow is determined at each load step using binary image segmentation. It varies from 0.44 in the beginning to nearly 0.65 at the end of the loading, which corresponds to a density range of 400–600 kg/m 3 . The estimated modulus and viscosity terms, obtained from the Burger’s model, show an increasing trend with density. The values of the Maxwell and Kelvin–Voigt moduli were found to range from 60 to 320 MPa and from 6 to 40 MPa, respectively. Meanwhile, the viscosity values for the Maxwell and Kelvin–Voigt models varied from 0.4 to 3.5 GPa-s, and 0.3–3.2 GPa-s, respectively, within the considered density range. In addition, Digital Volume Correlation (DVC) was used to calculate the full-field strain distribution in the specimen at each load step. The image analysis results show that, the particle size and specific surface area (SSA) do not change significantly within the studied range of loading and densities, while the sphericity of the particles is increased. The grain diameter ranges from approximately 100 μ m to nearly 400 μ m, with a mode of nearly 200 μ m. The methodology presented in this study opens up a path for an extensive statistical analysis of the material properties by experimenting more snow samples.

sted, utgiver, år, opplag, sider
Springer Nature, 2024
Emneord
Micro tomography, Material modeling, Stress-strain response, Digital volume correlation, Image analysis, Snow
HSV kategori
Forskningsprogram
Experimentell mekanik; Strömningslära
Identifikatorer
urn:nbn:se:ltu:diva-103511 (URN)10.1007/s00339-023-07167-y (DOI)001123446400001 ()2-s2.0-85179360802 (Scopus ID)
Merknad

Validerad;2024;Nivå 2;2024-02-26 (signyg);

Full text license: CC BY

Tilgjengelig fra: 2024-01-08 Laget: 2024-01-08 Sist oppdatert: 2024-05-06bibliografisk kontrollert
4. Material mapping strategy to identify the density-dependent properties of dry natural snow
Åpne denne publikasjonen i ny fane eller vindu >>Material mapping strategy to identify the density-dependent properties of dry natural snow
Vise andre…
2024 (engelsk)Inngår i: Applied Physics A: Materials Science & Processing, ISSN 0947-8396, E-ISSN 1432-0630, Vol. 130, nr 2, artikkel-id 141Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

The mechanical properties of natural snow play a crucial role in understanding glaciers, avalanches, polar regions, and snow-related constructions. Research has concentrated on how the mechanical properties of snow vary, primarily with its density; the integration of cutting-edge techniques like micro-tomography with traditional loading methods can enhance our comprehension of these properties in natural snow. This study employs CT imaging and uniaxial compression tests, along with the Digital Volume Correlation (DVC) to investigate the density-dependent material properties of natural snow. The data from two snow samples, one initially non-compressed (test 1) and the other initially compressed (test 2), were fed into Burger’s viscoelastic model to estimate the material properties. CT imaging with 801 projections captures the three-dimensional structure of the snow initially and after each loading step at -18C, using a constant deformation rate (0.2 mm/min). The relative density of the snow, ranging from 0.175 to 0.39 (equivalent to 160–360 kg/m), is determined at each load step through binary image segmentation. Modulus and viscosity terms, estimated from Burger’s model, exhibit a density-dependent increase. Maxwell and Kelvin–Voigt moduli range from 0.5 to 14 MPa and 0.1 to 0.8 MPa, respectively. Viscosity values for the Maxwell and Kelvin–Voigt models vary from 0.2 to 2.9 GPa-s and 0.2 to 2.3 GPa-s within the considered density range, showing an exponent between 3 and 4 when represented as power functions. Initial grain characteristics for tests 1 and 2, obtained through image segmentation, reveal an average Specific Surface Area (SSA) of around 55 1/mm and 40 1/mm, respectively. The full-field strain distribution in the specimen at each load step is calculated using the DVC, highlighting strong strain localization indicative of non-homogeneous behavior in natural snow. These findings not only contribute to our understanding of natural snow mechanics but also hold implications for applications in fields such as glacier dynamics and avalanche prediction.

sted, utgiver, år, opplag, sider
Springer Nature, 2024
Emneord
Material mapping, Micro tomography, Compression test, Digital volume correlation, Snow and ice
HSV kategori
Forskningsprogram
Experimentell mekanik; Strömningslära
Identifikatorer
urn:nbn:se:ltu:diva-104236 (URN)10.1007/s00339-024-07288-y (DOI)001153419300002 ()2-s2.0-85183678465 (Scopus ID)
Merknad

Validerad;2024;Nivå 2;2024-02-12 (joosat);

CC BY Full text license

Tilgjengelig fra: 2024-02-12 Laget: 2024-02-12 Sist oppdatert: 2024-05-06bibliografisk kontrollert

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