The Experts below are selected from a list of 66 Experts worldwide ranked by ideXlab platform

Karen Hapgood - One of the best experts on this subject based on the ideXlab platform.

  • experimental study of the deformation and breakage of 3d printed agglomerates effects of packing density and inter Particle Bond strength
    Powder Technology, 2018
    Co-Authors: Ruihuan Ge, Mojtaba Ghadiri, Tina Bonakdar, Zongyan Zhou, Ian Larson, Karen Hapgood
    Abstract:

    Characterization of the mechanical properties of agglomerates is important in order to understand their deformation and breakage. However, research progress has been hampered by limitations in our ability to manufacture reproducible agglomerates with well-controlled and fully characterised mechanical properties. In this paper, we report on the preparation and testing of agglomerates with tuneable properties using 3D printing technology. Two typical agglomerate structures with different packing densities were designed and printed using a PolyJet 3D printer. Each agglomerate consisted of rigid primary Particles connected by either rigid or rubber-like inter-Particle cylindrical Bonds. Compression tests (using speeds in the range 0.02–0.5 mm/s) and drop weight impact tests were carried out to investigate the effect of Bond material and strain rate on mechanical properties of the agglomerates. The results show that strain rate affects their deformation and breakage significantly, and breakage patterns of the two structures are different under uniaxial compression and impact test conditions. These results demonstrate the broad utility of 3D printed agglomerates as ideal “test” agglomerates for a range of breakage studies, including validating computer simulations of DEM breakage.

Lennart Bergström - One of the best experts on this subject based on the ideXlab platform.

  • Relating the molecular structure of comb-type superplasticizers to the compression rheology of MgO suspensions
    Cement and Concrete Research, 2006
    Co-Authors: Ane M. Kjeldsen, Robert J. Flatt, Lennart Bergström
    Abstract:

    We have investigated the effect of superplasticizers on the rheological properties of concentrated MgO suspensions. The comb-type anionic polymers with grafted polyethylene oxide chains adsorb onto the MgO surface and infer a steric repulsion where the range scales with the length of the PEO side chains. Consolidation experiments, where the volume fraction gradient of Particle networks has been determined in response to a centrifugal force field, offer a simple, yet accurate, way of investigating flocculated, partly stabilized and stable suspensions under compression. The compression rheology behaviour could be related to the estimated thickness of the adsorbed superplasticizers and a scaling analysis was used to quantitatively assess the importance of the length of the grafted PEO-chains on the magnitude of the inter-Particle Bond strength.

  • Relating the molecular structure of comb-type superplasticizers to the compression rheology of MgO suspensions
    Cement and Concrete Research, 2006
    Co-Authors: Ane M. Kjeldsen, Robert J. Flatt, Lennart Bergström
    Abstract:

    We have investigated the effect of superplasticizers on the rheological properties of concentrated MgO suspensions. The comb-type anionic polymers with grafted polyethylene oxide chains adsorb onto the MgO surface and infer a steric repulsion where the range scales with the length of the PEO side chains. Consolidation experiments, where the volume fraction gradient of Particle networks has been determined in response to a centrifugal force field, offer a simple, yet accurate, way of investigating flocculated, partly stabilized and stable suspensions under compression. The compression rheology behaviour could be related to the estimated thickness of the adsorbed superplasticizers and a scaling analysis was used to quantitatively assess the importance of the length of the grafted PEO-chains on the magnitude of the inter-Particle Bond strength. © 2006 Elsevier Ltd. All rights reserved.

Ane M. Kjeldsen - One of the best experts on this subject based on the ideXlab platform.

  • Relating the molecular structure of comb-type superplasticizers to the compression rheology of MgO suspensions
    Cement and Concrete Research, 2006
    Co-Authors: Ane M. Kjeldsen, Robert J. Flatt, Lennart Bergström
    Abstract:

    We have investigated the effect of superplasticizers on the rheological properties of concentrated MgO suspensions. The comb-type anionic polymers with grafted polyethylene oxide chains adsorb onto the MgO surface and infer a steric repulsion where the range scales with the length of the PEO side chains. Consolidation experiments, where the volume fraction gradient of Particle networks has been determined in response to a centrifugal force field, offer a simple, yet accurate, way of investigating flocculated, partly stabilized and stable suspensions under compression. The compression rheology behaviour could be related to the estimated thickness of the adsorbed superplasticizers and a scaling analysis was used to quantitatively assess the importance of the length of the grafted PEO-chains on the magnitude of the inter-Particle Bond strength.

  • Relating the molecular structure of comb-type superplasticizers to the compression rheology of MgO suspensions
    Cement and Concrete Research, 2006
    Co-Authors: Ane M. Kjeldsen, Robert J. Flatt, Lennart Bergström
    Abstract:

    We have investigated the effect of superplasticizers on the rheological properties of concentrated MgO suspensions. The comb-type anionic polymers with grafted polyethylene oxide chains adsorb onto the MgO surface and infer a steric repulsion where the range scales with the length of the PEO side chains. Consolidation experiments, where the volume fraction gradient of Particle networks has been determined in response to a centrifugal force field, offer a simple, yet accurate, way of investigating flocculated, partly stabilized and stable suspensions under compression. The compression rheology behaviour could be related to the estimated thickness of the adsorbed superplasticizers and a scaling analysis was used to quantitatively assess the importance of the length of the grafted PEO-chains on the magnitude of the inter-Particle Bond strength. © 2006 Elsevier Ltd. All rights reserved.

Mingjing Jiang - One of the best experts on this subject based on the ideXlab platform.

  • numerical study of inter Particle Bond failure by 3d discrete element method
    International Journal for Numerical and Analytical Methods in Geomechanics, 2016
    Co-Authors: Zhifu Shen, Mingjing Jiang
    Abstract:

    Summary The cohesive-frictional nature of cementitious geomaterials raises great interest in the discrete element method (DEM) simulation of their mechanical behavior, where a proper Bond failure criterion is usually required. In this paper, the failure of Bond material between two spheres was investigated numerically using DEM that can easily reproduce the failure process of brittle material. In the DEM simulations, a Bonded-grain system (composed of two Particles and Bond material in between) was discretized as a cylindrical assembly of very fine Particles connecting two large end spheres. Then, the Bonded-grain system was subjected to compression/tension, shear, rolling and torsion loadings and their combinations until overall failure (peak state) was reached. Bonded-grain systems with various sizes were employed to investigate Bond geometry effects. The numerical results show that the compression strength is highly affected by Bond geometry, with the tensile strength being dependent to a lesser degree. The shear, rolling and torsion strengths are all normal force dependent; i.e., with an increase in the normal force, these strengths first increase at a declining rate and then start to decrease upon the normal force exceeding a critical value. The combined actions of shear force, rolling moment and torque lead to a spherical failure envelope in a normalized loading space. The fitted Bond geometry factors and Bond failure envelopes obtained numerically in this three-dimensional study are qualitatively consistent with those in previous two-dimensional experiments. The obtained Bond failure criterion can be incorporated into a future Bond contact model. Copyright © 2015 John Wiley & Sons, Ltd.

  • Numerical study of inter‐Particle Bond failure by 3D discrete element method
    International Journal for Numerical and Analytical Methods in Geomechanics, 2015
    Co-Authors: Zhifu Shen, Mingjing Jiang
    Abstract:

    Summary The cohesive-frictional nature of cementitious geomaterials raises great interest in the discrete element method (DEM) simulation of their mechanical behavior, where a proper Bond failure criterion is usually required. In this paper, the failure of Bond material between two spheres was investigated numerically using DEM that can easily reproduce the failure process of brittle material. In the DEM simulations, a Bonded-grain system (composed of two Particles and Bond material in between) was discretized as a cylindrical assembly of very fine Particles connecting two large end spheres. Then, the Bonded-grain system was subjected to compression/tension, shear, rolling and torsion loadings and their combinations until overall failure (peak state) was reached. Bonded-grain systems with various sizes were employed to investigate Bond geometry effects. The numerical results show that the compression strength is highly affected by Bond geometry, with the tensile strength being dependent to a lesser degree. The shear, rolling and torsion strengths are all normal force dependent; i.e., with an increase in the normal force, these strengths first increase at a declining rate and then start to decrease upon the normal force exceeding a critical value. The combined actions of shear force, rolling moment and torque lead to a spherical failure envelope in a normalized loading space. The fitted Bond geometry factors and Bond failure envelopes obtained numerically in this three-dimensional study are qualitatively consistent with those in previous two-dimensional experiments. The obtained Bond failure criterion can be incorporated into a future Bond contact model. Copyright © 2015 John Wiley & Sons, Ltd.

Zhifu Shen - One of the best experts on this subject based on the ideXlab platform.

  • numerical study of inter Particle Bond failure by 3d discrete element method
    International Journal for Numerical and Analytical Methods in Geomechanics, 2016
    Co-Authors: Zhifu Shen, Mingjing Jiang
    Abstract:

    Summary The cohesive-frictional nature of cementitious geomaterials raises great interest in the discrete element method (DEM) simulation of their mechanical behavior, where a proper Bond failure criterion is usually required. In this paper, the failure of Bond material between two spheres was investigated numerically using DEM that can easily reproduce the failure process of brittle material. In the DEM simulations, a Bonded-grain system (composed of two Particles and Bond material in between) was discretized as a cylindrical assembly of very fine Particles connecting two large end spheres. Then, the Bonded-grain system was subjected to compression/tension, shear, rolling and torsion loadings and their combinations until overall failure (peak state) was reached. Bonded-grain systems with various sizes were employed to investigate Bond geometry effects. The numerical results show that the compression strength is highly affected by Bond geometry, with the tensile strength being dependent to a lesser degree. The shear, rolling and torsion strengths are all normal force dependent; i.e., with an increase in the normal force, these strengths first increase at a declining rate and then start to decrease upon the normal force exceeding a critical value. The combined actions of shear force, rolling moment and torque lead to a spherical failure envelope in a normalized loading space. The fitted Bond geometry factors and Bond failure envelopes obtained numerically in this three-dimensional study are qualitatively consistent with those in previous two-dimensional experiments. The obtained Bond failure criterion can be incorporated into a future Bond contact model. Copyright © 2015 John Wiley & Sons, Ltd.

  • Numerical study of inter‐Particle Bond failure by 3D discrete element method
    International Journal for Numerical and Analytical Methods in Geomechanics, 2015
    Co-Authors: Zhifu Shen, Mingjing Jiang
    Abstract:

    Summary The cohesive-frictional nature of cementitious geomaterials raises great interest in the discrete element method (DEM) simulation of their mechanical behavior, where a proper Bond failure criterion is usually required. In this paper, the failure of Bond material between two spheres was investigated numerically using DEM that can easily reproduce the failure process of brittle material. In the DEM simulations, a Bonded-grain system (composed of two Particles and Bond material in between) was discretized as a cylindrical assembly of very fine Particles connecting two large end spheres. Then, the Bonded-grain system was subjected to compression/tension, shear, rolling and torsion loadings and their combinations until overall failure (peak state) was reached. Bonded-grain systems with various sizes were employed to investigate Bond geometry effects. The numerical results show that the compression strength is highly affected by Bond geometry, with the tensile strength being dependent to a lesser degree. The shear, rolling and torsion strengths are all normal force dependent; i.e., with an increase in the normal force, these strengths first increase at a declining rate and then start to decrease upon the normal force exceeding a critical value. The combined actions of shear force, rolling moment and torque lead to a spherical failure envelope in a normalized loading space. The fitted Bond geometry factors and Bond failure envelopes obtained numerically in this three-dimensional study are qualitatively consistent with those in previous two-dimensional experiments. The obtained Bond failure criterion can be incorporated into a future Bond contact model. Copyright © 2015 John Wiley & Sons, Ltd.