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  • 1.
    Bahaloo, Hassan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Mechanics of Ice and Snow as a Granular Material2024Doctoral thesis, comprehensive summary (Other academic)
    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.

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  • 2.
    Bahaloo, Hassan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Casselgren, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Forsberg, Fredrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Sjödahl, Mikael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Discrete element simulation of dry snow using the developed analytic bond model2021In: IOP Conference Series: Materials Science and Engineering, Institute of Physics (IOP), 2021, Vol. 1190, article id 012015Conference paper (Refereed)
    Abstract [en]

    Snow is a heterogenous, hot material which is constituted from ice particles. The bonding behavior of ice particles is an important parameter determining the macroscopic behavior of snow. Discrete Element Method (DEM) is usually used as a tool to model dry snow. The most important input data required into the DEM is bonding behavior of ice particles since ice particles can adhere to form bonds when they brought into contact. This study had two aims: first, an analytical formulation was derived to predict the bond diameter of ice-ice contacts as a function of time, compressive load, and strain rate. Using the previously published data for strain rate of ice, a solution method was developed. The results of bond diameter development with time were compared to experimental data and a good agreement was found. Second, a DEM for dry snow was developed and programmed in MATLAB and the developed bond model was employed in the simulation to study the deposition behavior of snow in a container under gravity acceleration. A specific beam element with implemented damage model was developed in implemented in the simulation using the bond data obtained from the analytical approach. The simulated parameters were macroscopic angle of repose, packing density, and surface conditions as a function of temperature and filling rate. The results showed that discrete element simulations were able to verify the existing published experimental data. Specifically, the simulation results showed that angle of repose of snow decreased rapidly with decreasing the temperature, the surface became very irregular due to the particles rotation and re-arrangement for lower falling speeds of particles, and density increased with depth of deposition. These findings were all matched with experimental observations.

  • 3.
    Bahaloo, Hassan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Eidevåg, Tobias
    Department of Chemistry and Chemical Engineering, Chalmers University of Technology, SE-41296 Gothenburg Sweden; Contamination and Core CFD, Volvo Car Corporation, SE-405 31 Gothenburg, Sweden.
    Gren, Per
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Casselgren, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Forsberg, Fredrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Abrahamsson, Per
    Technical Analysis, Fluid Mechanics, AFRY, Gothenburg, Sweden 412 63.
    Sjödahl, Mikael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Ice Sintering: Dependence of Sintering Force on Temperature, Load, Duration, and Particle Size2022In: Svenska Mekanikdagar 2022 / [ed] Pär Jonsén; Lars-Göran Westerberg; Simon Larsson; Erik Olsson, Luleå tekniska universitet, 2022Conference paper (Refereed)
  • 4.
    Bahaloo, Hassan
    et al.
    Faculty of Industrial Engineering, Mechanical Engineering and Computer Science, School of Engineering and Natural Sciences, University of Iceland, Reykjavik, Iceland; Institute for Biomechanics, ETH-Zürich, Zurich, Switzerland.
    Enns-Bray, William S.
    Institute for Biomechanics, ETH-Zürich, Zurich, Switzerland.
    Fleps, Ingmar
    Institute for Biomechanics, ETH-Zürich, Zurich, Switzerland.
    Ariza, Oscar
    Institute for Biomechanics, ETH-Zürich, Zurich, Switzerland; Orthopaedic and Injury Biomechanics Group, University of British Columbia, Vancouver, Canada; Centre for Hip Health and Mobility, University of British Columbia, Vancouver, Canada; Department of Mechanical Engineering, University of British Columbia, Vancouver, Canada.
    Gilchrist, Seth
    Orthopaedic and Injury Biomechanics Group, University of British Columbia, Vancouver, Canada; Centre for Hip Health and Mobility, University of British Columbia, Vancouver, Canada; Department of Mechanical Engineering, University of British Columbia, Vancouver, Canada.
    Soyka, R. Widmer
    Institute for Biomechanics, ETH-Zürich, Zurich, Switzerland.
    Guy, Pierre
    Centre for Hip Health and Mobility, University of British Columbia, Vancouver, Canada; Department of Orthopedics, University of British Columbia, Vancouver, Canada.
    Palsson, Halldor
    Faculty of Industrial Engineering, Mechanical Engineering and Computer Science, School of Engineering and Natural Sciences, University of Iceland, Reykjavik, Iceland.
    Ferguson, Stephen J.
    Institute for Biomechanics, ETH-Zürich, Zurich, Switzerland.
    Cripton, Peter A.
    Orthopaedic and Injury Biomechanics Group, University of British Columbia, Vancouver, Canada; Centre for Hip Health and Mobility, University of British Columbia, Vancouver, Canada; Department of Mechanical Engineering, University of British Columbia, Vancouver, Canada; Department of Orthopedics, University of British Columbia, Vancouver, Canada.
    Helgason, Benedikt
    Institute for Biomechanics, ETH-Zürich, Zurich, Switzerland; School of Science and Engineering, Reykjavik University, Reykjavik, Iceland.
    On the failure initiation in the proximal human femur under simulated sideways fall2018In: Annals of Biomedical Engineering, ISSN 0090-6964, E-ISSN 1573-9686, Vol. 46, p. 270-283Article in journal (Refereed)
    Abstract [en]

    The limitations of areal bone mineral density measurements for identifying at-risk individuals have led to the development of alternative screening methods for hip fracture risk including the use of geometrical measurements from the proximal femur and subject specific finite element analysis (FEA) for predicting femoral strength, based on quantitative CT data (qCT). However, these methods need more development to gain widespread clinical applications. This study had three aims: To investigate whether proximal femur geometrical parameters correlate with obtained femur peak force during the impact testing; to examine whether or not failure of the proximal femur initiates in the cancellous (trabecular) bone; and finally, to examine whether or not surface fracture initiates in the places where holes perforate the cortex of the proximal femur. We found that cortical thickness around the trochanteric-fossa is significantly correlated to the peak force obtained from simulated sideways falling (R 2 = 0.69) more so than femoral neck cortical thickness (R 2 = 0.15). Dynamic macro level FE simulations predicted that fracture generally initiates in the cancellous bone compartments. Moreover, our micro level FEA results indicated that surface holes may be involved in primary failure events.

  • 5.
    Bahaloo, Hassan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Forsberg, Fredrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Casselgren, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lycksam, Henrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Sjödahl, Mikael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Mapping of density-dependent material properties of dry manufactured snow using μCT2024In: Applied Physics A: Materials Science & Processing, ISSN 0947-8396, E-ISSN 1432-0630, Vol. 130, article id 16Article in journal (Refereed)
    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.

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  • 6.
    Bahaloo, Hassan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Gren, Per
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Casselgren, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Forsberg, Fredrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Sjödahl, Mikael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Capillary Bridge in Contact with Ice Particles Can Be Related to the Thin Liquid Film on Ice2024In: Journal of cold regions engineering, ISSN 0887-381X, E-ISSN 1943-5495, Vol. 38, no 1, article id 04023021Article in journal (Refereed)
    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.

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  • 7.
    Bahaloo, Hassan
    et al.
    Department of Mechanical Engineering, University of New Hampshire, Durham.
    Li, Yaning
    Department of Mechanical Engineering, University of New Hampshire, Durham.
    Micropolar Modeling of Auxetic Chiral Lattices With Tunable Internal Rotation2019In: Journal of applied mechanics, ISSN 0021-8936, E-ISSN 1528-9036, Vol. 86, no 4Article in journal (Refereed)
  • 8.
    Bahaloo, Hassan
    et al.
    Department of Mechanical and Industrial Engineering, Northeastern University, Boston, USA. Department of Mechanical and Industrial Engineering, Qatar University, Doha, Qatar.
    Papadopolus, Jim
    Department of Mechanical and Industrial Engineering, Northeastern University, Boston, USA. Department of Mechanical and Industrial Engineering, Qatar University, Doha, Qatar.
    Ghosh, Ranajay
    Department of Mechanical and Industrial Engineering, Northeastern University, Boston, USA.
    Mahdi, Elsadig
    Department of Mechanical and Industrial Engineering, Qatar University, Doha, Qatar.
    Vaziri, Ashkan
    Department of Mechanical and Industrial Engineering, Northeastern University, Boston, USA.
    Nayeb-Hashemi, Hamid
    Department of Mechanical and Industrial Engineering, Northeastern University, Boston, USA.
    Transverse vibration and stability of a functionally graded rotating annular disk with a circumferential crack2016In: International Journal of Mechanical Sciences, ISSN 0020-7403, E-ISSN 1879-2162, Vol. 113, p. 26-35Article in journal (Refereed)
  • 9.
    Bahaloohoreh, Hassan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Experiments and simulations on the mechanics of ice and snow2023Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this study, experiments and simulations were conducted to investigate ice and snow. The ice sintering force as a function of temperature, pressing force (contact load), contact duration, and particle size during the primary stage of sintering was formulated using experimental methods along with an approximate, semi-analytic, close-form solution. It was shown that the ice sintering force increases nearly linear with increasing external pressing force but best approximated as a power law for dependency on both contact duration and particle size. Moreover, 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 highly nonlinear and follows the Arrhenius equation. It was observed that at temperatures closer to the melting point, a liquid bridge is observed upon these paration of the contacted ice particles. The ratio of ultimate tensile strength of ice to the axial stress concentration factor in tension is found as an important factor in determining the sintering force, and a value of nearly 1.1 MPa was estimated to best catch the sintering force of ice in different conditions. From the temperature dependency, the activation energy is calculated to be around 41.4 kJ/mol, which is close to the previously reported value. Also, the results for the sintering force suggest that smaller particles are “stickier” than larger particles. Moreover, cavitation and surface cracking is observed during the formation of the ice particles and these can be one of the sources for the variations observed in the measured ice sintering force values.

    The presence of a capillary bridge in contact between an ice particle and a "smooth" (or rough) Aluminum surface at relative humidity around 50% and temperatures below the melting point was experimentally demonstrated. Experiments were conducted under controlled temperature conditions and the mechanical instability of the bridge upon separation of the ice particle from the Aluminum surface with a constant speed was considered. It was observed that a liquid bridge with a more pronounced volume at temperatures near the melting point is formed. It was showen that the separation distance is proportional to the cube root of the volume of the bridge. The volume of the liquidbridge is used to estimate the thickness of the liquid layer on the ice particle and the estimated value was shown to be within the range reported in the literature. The thickness of the liquid layer decreases from nearly 56 nm at -1.7◦C to 0.2 nm at -12.7◦C. The dependence can be approximated with a power law, proportional to (TM − T)−β, where β < 2.6. We further observe that for a rough surface, the capillary bridge formation in the considered experimental conditions vanishes.

    The Discrete Element Method (DEM) was employed to simulate the filling behavior of dry snow. Snow as a heterogeneous, hot material which is constituted from spherical ice particles which can form bonds. The bonding behavior of ice particles is important in determining the macroscopic behavior of snow. The bond diameter of ice-ice contacts as a function of time, compressive load, and strain rate is used and a DEM for dry snow was developed and programmed in MATLAB. A beam element with implemented damage model was used in the simulation. The simulated parameters were macroscopic angle of repose, packing density, and surface conditions as a function of temperature and fillingrate. The DEM results were able to verify the existing published experimental data. The simulation results showed that angle of repose of snow decreased with decreasing the temperature, the surface became irregular due to particles rotation and re-arrangement for lower falling speeds of particles, and density increased with depth of deposition.

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  • 10.
    Bahaloohoreh, Hassan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Eidevåg, Tobias
    Department of Chemistry and Chemical Engineering, Chalmers University of Technology, SE-41296 Gothenburg, Sweden; Contamination and Core CFD, Volvo Car Corporation, SE-405 31 Gothenburg, Sweden.
    Gren, Per
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Casselgren, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Forsberg, Fredrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Abrahamsson, Per
    Technical Analysis, Fluid Mechanics, AFRY, Gothenburg 412 63, Sweden.
    Sjödahl, Mikael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Ice sintering: Dependence of sintering force on temperature, load, duration, and particle size2022In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 131, no 2, article id 025109Article in journal (Refereed)
    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.

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  • 11.
    Bahaloohoreh, Hassan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Forsberg, Fredrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lycksam, Henrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Casselgren, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Sjödahl, Mikael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Material mapping strategy to identify the density-dependent properties of dry natural snow2024In: Applied Physics A: Materials Science & Processing, ISSN 0947-8396, E-ISSN 1432-0630, Vol. 130, no 2, article id 141Article in journal (Refereed)
    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.

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  • 12.
    Bahaloohoreh, Hassan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Gren, Per
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Casselgren, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Forsberg, Fredrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Sjödahl, Mikael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Capillary bridge in contact of ice particles reveals the thin liquid film on ice2023Manuscript (preprint) (Other academic)
  • 13.
    Bahaloohoreh, Hassan
    et al.
    Middle East Petro Gas Co., Tehran, Iran.
    Samadi, Mostafa
    Middle East Petro Gas Co., Tehran, Iran.
    Ebrahimi, Alireza
    Middle East Petro Gas Co., Tehran, Iran.
    Misalignment modeling in rotating systems2009Conference paper (Refereed)
  • 14.
    Enns-Bray, William S
    et al.
    Institute for Biomechanics, ETH-Zürich, Switzerland.
    Bahaloo, Hassan
    Faculty of Industrial Engineering, Mechanical Engineering and Computer Science, School of Engineering and Natural Sciences University of Iceland, Reykjavik, Iceland.
    Fleps, Ingmar
    Institute for Biomechanics, ETH-Zürich, Switzerland.
    Ariza, Oscar
    Orthopaedic and Injury Biomechanics Group University of British Columbia, Vancouver, Canada; Centre for Hip Health and Mobility University of British Columbia, Vancouver, Canada; Department of Mechanical Engineering University of British Columbia, Vancouver, Canada.
    Gilchrist, Seth
    Orthopaedic and Injury Biomechanics Group University of British Columbia, Vancouver, Canada; Centre for Hip Health and Mobility University of British Columbia, Vancouver, Canada; Department of Mechanical Engineering University of British Columbia, Vancouver, Canada; Department of Orthopaedics University of British Columbia, Vancouver, Canada.
    Widmer, Rene P
    Institute for Biomechanics, ETH-Zürich, Switzerland.
    Guy, Pierre
    Centre for Hip Health and Mobility University of British Columbia, Vancouver, Canada; Department of Orthopaedics University of British Columbia, Vancouver, Canada.
    Pálsson, Halldor
    Faculty of Industrial Engineering, Mechanical Engineering and Computer Science, School of Engineering and Natural Sciences University of Iceland, Reykjavik, Iceland.
    Ferguson, Stephen J
    Institute for Biomechanics, ETH-Zürich, Switzerland.
    Cripton, Peter A
    Orthopaedic and Injury Biomechanics Group University of British Columbia, Vancouver, Canada; Centre for Hip Health and Mobility University of British Columbia, Vancouver, Canada; Department of Mechanical Engineering University of British Columbia, Vancouver, Canada; Department of Orthopaedics University of British Columbia, Vancouver, Canada.
    Helgason, Benedikt
    Institute for Biomechanics, ETH-Zürich, Switzerland.
    Material mapping strategy to improve the predicted response of the proximal femur to a sideways fall impact2018In: Journal of The Mechanical Behavior of Biomedical Materials, ISSN 1751-6161, E-ISSN 1878-0180, Vol. 78, p. 196-205Article in journal (Refereed)
  • 15.
    Enns-Bray, William S
    et al.
    Institute for Biomechanics, ETH Zürich, Zürich, Switzerland.
    Bahaloo, Hassan
    School of Engineering and Natural Sciences, University of Iceland, Reykjavik, Iceland.
    Fleps, Ingmar
    Institute for Biomechanics, ETH Zürich, Zürich, Switzerland.
    Pauchard, Yves
    McCaig Institute for Bone and Joint Health, University of Calgary, Calgary, Canada.
    Taghizadeh, Elham
    Institute for Surgical Technology and Biomechanics, University of Bern, Bern, Switzerland.
    Sigurdsson, Sigurdur
    The Icelandic Heart Association Research Institute, Kopavogur, Iceland.
    Aspelund, Thor
    The Icelandic Heart Association Research Institute, Kopavogur, Iceland.
    Büchler,, Philippe
    Institute for Surgical Technology and Biomechanics, University of Bern, Bern, Switzerland.
    Harris, Tamara
    Laboratory of Epidemiology and Population Sciences, National Institute on Aging, Bethesda, MD, USA.
    Gudnason, Vilmunder
    The Icelandic Heart Association Research Institute, Kopavogur, Iceland.
    Ferguson, Stephen J
    Institute for Biomechanics, ETH Zürich, Zürich, Switzerland.
    Pálsson, Halldor
    School of Engineering and Natural Sciences, University of Iceland, Reykjavik, Iceland.
    Helgason, Benedikt
    Institute for Biomechanics, ETH Zürich, Zürich, Switzerland; School of Science and Engineering, Reykjavik University, Reykjavik, Iceland.
    Biofidelic finite element models for accurately classifying hip fracture in a retrospective clinical study of elderly women from the AGES Reykjavik cohort2019In: Bone, ISSN 8756-3282, E-ISSN 1873-2763, Vol. 120, p. 25-37Article in journal (Refereed)
  • 16.
    Safari Loaliyan, Soheil
    et al.
    Department of Mechanical and Industrial Engineering, Northeastern University, Boston, Massachusetts 02115, USA.
    Bahaloo, Hassan
    Department of Mechanical and Industrial Engineering, Northeastern University, Boston, Massachusetts 02115, USA.
    Ghosh, Ranajay
    Department of Mechanical and Aerospace Engineering, University of Central Florida, Orlando, Florida 32816, USA.
    Nayeb-Hashemi, Hamid
    Department of Mechanical and Industrial Engineering, Northeastern University, Boston, Massachusetts 02115, USA.
    Vaziri, Ashkan
    Department of Mechanical and Industrial Engineering, Northeastern University, Boston, Massachusetts 02115, USA.
    Energy harvesting using snap-through deformation in lattice structures2018In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 113, no 25Article in journal (Refereed)
    Abstract [en]

    We demonstrated the feasibility of harvesting mechanical energy through the proper design and installation of a lattice structure which undergoes snap-through deformation under applied mechanical loading. First, the theoretical formulations for both symmetric and asymmetric modes of the snap-through deformation in a 2D lattice structure were derived. Then, experiments were conducted on the prototype to measure the energy harvesting ability at different frequencies and to investigate the capability of charging a capacitor connected to the lattice prototype. Finally, the effects of the defect in the lattice on energy harvesting were discussed. Our results showed that the average generated voltage across a 25 kΩ resistor increased by increasing the frequency of loading. However, energy stored in a capacitor was independent of loading frequency. For a defective structure with a fixed vertex, the generated voltage is lower yet increasing with the frequency of loading. The designed structure is robust and provides sustainable energy output under cyclic loading even with the presence of defects and imperfections.

  • 17.
    Zheng, Yue
    et al.
    Department of Mechanical and Industrial Engineering, Northeastern University, Boston, MA 02115, USA.
    Bahaloo, Hassan
    Department of Mechanical and Industrial Engineering, Northeastern University, Boston, MA 02115, USA.
    Mousanezhad, Davood
    Department of Mechanical and Industrial Engineering, Northeastern University, Boston, MA 02115, USA.
    Mahdi, Elsadig
    Mechanical and Industrial Engineering Department, Qatar University, Doha, Qatar.
    Vaziri, Ashkan
    Department of Mechanical and Industrial Engineering, Northeastern University, Boston, MA 02115, USA b.
    Nayeb-Hashemi, Hamid
    Department of Mechanical and Industrial Engineering, Northeastern University, Boston, MA 02115, USA b.
    Stress analysis in functionally graded rotating disks with non-uniform thickness and variable angular velocity2016In: International Journal of Mechanical Sciences, ISSN 0020-7403, E-ISSN 1879-2162, Vol. 119, p. 283-293Article in journal (Refereed)
    Abstract [en]

    Stress field in functionally graded (FG) rotating disks with non-uniform thickness and variable angular velocity is studied numerically. The elastic modulus and mass density of the disks are assumed to be varying along the radius as a power-law function of the radial coordinate, while the Poisson's ratio is kept constant. The governing equations for the stress field is derived and numerically solved using the finite difference method for the case of fixed-free boundary conditions. Additionally, the effect of material gradient index (i.e., the level of material gradation) on the stress field is evaluated. Our results show that the optimum stress field is achieved by having a thickness profile in the form of a rational function of the radial coordinate. Moreover, a smaller stress field can be developed by having greater mass density and elastic modulus at the outer radius of the disk (i.e., ceramic-rich composites at the outer radius). The numerical results additionally reveal that deceleration results in shear-stress development within the disks where a greater deceleration leads to greater shear stress; however this has almost no effect on the radial and circumferential stresses. Furthermore, the shear stress can cause a shift in the location of the maximum Von Mises stress, where for small deceleration, maximum Von Mises stress is located somewhere between the inner and outer radii, while for large deceleration it is located at the inner radius.

  • 18.
    Zheng, Yue
    et al.
    Department of Mechanical and Industrial Engineering, Northeastern University, Boston..
    Bahaloo, Hassan
    Department of Mechanical and Industrial Engineering, Northeastern University, Boston..
    Mousanezhad, Davood
    Department of Mechanical and Industrial Engineering, Northeastern University, Boston..
    Vaziri, Ashkan
    Department of Mechanical and Industrial Engineering, Northeastern University, Boston..
    Nayeb-Hashemi, Hamid
    Department of Mechanical and Industrial Engineering, Northeastern University, Boston..
    Displacement and stress fields in a functionally graded fiber-reinforced rotating disks with nonuniform thickness and variable angular velocity2017In: Journal of engineering materials and technology, ISSN 0094-4289, E-ISSN 1528-8889, Vol. 139, no 3Article in journal (Refereed)
    Abstract [en]

    Displacement and stress fields in a functionally graded (FG) fiber-reinforced rotating disk of nonuniform thickness subjected to angular deceleration are obtained. The disk has a central hole, which is assumed to be mounted on a rotating shaft. Unidirectional fibers are considered to be circumferentially distributed within the disk with a variable volume fraction along the radius. The governing equations for displacement and stress fields are derived and solved using finite difference method. The results show that for disks with fiber rich at the outer radius, the displacement field is lower in radial direction but higher in circumferential direction compared to the disk with the fiber rich at the inner radius. The circumferential stress value at the outer radius is substantially higher for disk with fiber rich at the outer radius compared to the disk with the fiber rich at the inner radius. It is also observed a considerable amount of compressive stress developed in the radial direction in a region close to the outer radius. These compressive stresses may prevent any crack growth in the circumferential direction of such disks. For disks with fiber rich at the inner radius, the presence of fibers results in minimal changes in the displacement and stress fields when compared to a homogenous disk made from the matrix material. In addition, we concluded that disk deceleration has no effect on the radial and hoop stresses. However, deceleration will affect the shear stress. Tsai–Wu failure criterion is evaluated for decelerating disks. For disks with fiber rich at the inner radius, the failure is initiated between inner and outer radii. However, for disks with fiber rich at the outer radius, the failure location depends on the fiber distribution.

1 - 18 of 18
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