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Abderrahim Michrafy - One of the best experts on this subject based on the ideXlab platform.

  • A combined DEM & FEM approach for modelling roll Compaction Process
    Powder Technology, 2018
    Co-Authors: Alon Mazor, Luca Orefice, Abderrahim Michrafy, Alain De Ryck, Johannes Khinast
    Abstract:

    Roll Compaction is a continuous manufacturing Process aiming to produce particulate granules from powders. A roll press typically consists of a screw feeding system, two rolls and a side sealing. Despite its conceptual simplicity, numerical modelling of the Process is challenging due to the complexity involving two different mechanisms: feeding by the screw and powder Compaction between the rolls. To represent the materials' behaviour both in the feeding zone and in the Compaction area, a combined three-dimensional Discrete Elements Method (DEM) and Finite Elements Method (FEM) is developed in this work. The DEM, which is a more suitable method to describe the flow of granular material, is used to model the motion of particles in the feeding zone. As the granular material deforms under high pressure between rolls, FEM offers a more versatile approach to represent the powder behaviour and frictional conditions. In the proposed approach the DEM and FEM are treated as complementary methods, enabling us to take advantages of the strengths of both. In this proposed approach, the time dependent velocity field of the particles at the end of the screw feeder is evaluated as a continuous field using the coarse graining (CG) framework, which was used as input data for the FEM model. FEM is then used to simulate the powder Compaction in between the rolls, and the resultant roll pressure and ribbon relative density are obtained. Our results show a direct correlation between the particle velocity driven by the screw conveyor and the roll pressure, both oscillating with the same period. This translates into an anisotropic ribbon with a density profile varying sinusoidally along its width, with a period equal to the duration of a screw turn.

  • a combined dem fem approach for modelling roll Compaction Process
    Powder Technology, 2017
    Co-Authors: Alon Mazor, Luca Orefice, Abderrahim Michrafy, Alain De Ryck, Johannes Khinast
    Abstract:

    Abstract Roll Compaction is a continuous manufacturing Process aiming to produce particulate granules from powders. A roll press typically consists of a screw feeding system, two rolls and a side sealing. Despite its conceptual simplicity, numerical modelling of the Process is challenging due to the complexity involving two different mechanisms: feeding by the screw and powder Compaction between the rolls. To represent the materials' behaviour both in the feeding zone and in the Compaction area, a combined three-dimensional Discrete Elements Method (DEM) and Finite Elements Method (FEM) is developed in this work. The DEM, which is a more suitable method to describe the flow of granular material, is used to model the motion of particles in the feeding zone. As the granular material deforms under high pressure between rolls, FEM offers a more versatile approach to represent the powder behaviour and frictional conditions. In the proposed approach the DEM and FEM are treated as complementary methods, enabling us to take advantages of the strengths of both. In this proposed approach, the time dependent velocity field of the particles at the end of the screw feeder is evaluated as a continuous field using the coarse graining (CG) framework, which was used as input data for the FEM model. FEM is then used to simulate the powder Compaction in between the rolls, and the resultant roll pressure and ribbon relative density are obtained. Our results show a direct correlation between the particle velocity driven by the screw conveyor and the roll pressure, both oscillating with the same period. This translates into an anisotropic ribbon with a density profile varying sinusoidally along its width, with a period equal to the duration of a screw turn.

  • Effect of roll compactor sealing system designs: A finite element analysis
    Powder Technology, 2016
    Co-Authors: Alon Mazor, Alain De Ryck, Lucia Perez-gandarillas, Abderrahim Michrafy
    Abstract:

    In the pharmaceutical industry, the roll Compaction is part of the dry granulation Process, densifying fine powders into ribbons that will be later milled to produce granules with good flowability for subsequent die Compaction Process. Roll compactors are constructed with a sealing system, limiting the loss of powder from the sides. However, the sealing system may result in unwanted non-uniformity of the ribbon's properties. In this work, a 3D Finite Elements Method (FEM) modeling is used to analyze the roll Compaction Process and the effect of sealing system designs on the compacted ribbon's density distribution. A density dependent Drucker-Prager Cap (DPC) constitutive model for microcrystalline cellulose (Avicel PH-101) was calibrated and implemented in Abaqus/Explicit. Two different FEM models were investigated, one with a fixed side sealing called cheek plates and another where the side sealing is integrated with the bottom roll called rimmed-roll. Both numerical and experimental results clearly show the non-uniform roll pressure and density distribution for the cheek plates assembly, whereas the rimmed-roll shows an overall more uniformly distributed resultant pressure and density distribution. These results demonstrate the capability of FEM modeling to provide insight and help achieving a better understanding of the roll Compaction Process.

  • Analysis of strain stress state in roller Compaction Process
    Powder Technology, 2011
    Co-Authors: Abderrahim Michrafy, Harona Diarra, John A. Dodds, Mohammed Michrafy, Luc Penazzi
    Abstract:

    The Process of drawing and densification of powdered microcrystalline cellulose by roller press in a steady state operation is analyzed using a 2D modeling with the finite element method and the modified Drucker-Prager Cap model as material behavior. Distributions of Process variables in contact surface between powder and roller such as pressure, shear stress and relative speed were predicted and used to analyze the basic mechanisms of the transport and the densification of powder between rolls. The results show clearly the existence of three contiguous zones: a phase where the powder is drawn between rolls by a sliding mechanism, a sticking phase where the powder is transported with the same velocity as the roll and where the densification by deforming the powder bed is achieved under the increase of roll pressure that reaches its peak before the neutral angle. The formed compact is then expulsed out of the gap by a slip mechanism resulting from the change of the sign of the shear stress. The predicted density distribution between the rolls, shows a gradual increase. The density reaches its maximum before the neutral point and shows values in agreement with the density of strips prepared with an instrumented roll press. The effect of varying the material parameters on the maximum pressure and the nip angle s also investigated. Beyond the description of the basic mechanisms of roller Compaction, this modeling shows a real potential of the optimization of the roller Compaction Process.

  • Analysis of strain stress state in roller Compaction Process
    Powder Technology, 2011
    Co-Authors: Abderrahim Michrafy, Harona Diarra, John A. Dodds, Mohammed Michrafy, Luc Penazzi
    Abstract:

    Symposium on Science and Technology of Powders and Sintered Materials (STPMF 2009), Montpellier, FRANCE, MAY 25-27, 2009International audienceThe Process of drawing and densification of powdered microcrystalline cellulose by roller press in a steady state operation is analyzed using a 2D modeling with the finite element method and the modified Drucker-Prager Cap model as material behavior. Distributions of Process variables in contact surface between powder and roller such as pressure, shear stress and relative speed were predicted and used to analyze the basic mechanisms of the transport and the densification of powder between rolls. The results show clearly the existence of three contiguous zones: a phase where the powder is drawn between rolls by a sliding mechanism, a sticking phase where the powder is transported with the same velocity as the roll and where the densification by deforming the powder bed is achieved under the increase of roll pressure that reaches its peak before the neutral angle. The formed compact is then expulsed out of the gap by a slip mechanism resulting from the change of the sign of the shear stress. The predicted density distribution between the rolls, shows a gradual increase. The density reaches its maximum before the neutral point and shows values in agreement with the density of strips prepared with an instrumented roll press. The effect of varying the material parameters on the maximum pressure and the nip angle s also investigated. Beyond the description of the basic mechanisms of roller Compaction, this modeling shows a real potential of the optimization of the roller Compaction Process

A K Ariffin - One of the best experts on this subject based on the ideXlab platform.

  • Numerical simulation and experimentation of warm metal powder Compaction Process
    Key Engineering Materials, 2011
    Co-Authors: Mujibur Rahman, A K Ariffin, Faris Tarlochan, Ramesh Singh, S.s.m. Nor
    Abstract:

    Powder Compaction at elevated temperature or known as warm Compaction is a Process of producing green compacts from metal powder, which is generally conducted between the ambient and the recrystalization temperature of the main powder constituent. Even though, warm Compaction was initiated at around 1998, not a lot of information can be found in the literature especially on the numerical simulation of the Process. Therefore, this paper presents the simulation of warm metal powder forming Process by using the developed computer code. The Elliptical Cap yield model has been used to represent the deformation behaviour of the powder mass during the forming Process at above ambient temperature. The material properties of powder mass, i. e., friction coefficient, elastic index, and plastic index, at different forming temperature, are established through warm Compaction experiment. The simulation was conducted to generate a green compact of a plain bush component. Some numerical simulation results were validated through experimentation, where a good agreement was found between the numerical simulation and the experimental results.

  • development of a finite element model of metal powder Compaction Process at elevated temperature
    Applied Mathematical Modelling, 2009
    Co-Authors: Mujibur Rahman, A K Ariffin
    Abstract:

    This paper presents the finite element modelling of metal powder Compaction Process at elevated temperature. In the modelling, the behaviour of powder is assumed to be rate independent thermo-elastoplastic material where the material constitutive laws are derived based on a continuum mechanics approach. The deformation Process of metal powder has been described by a large displacement based finite element formulation. The Elliptical Cap yield model has been used to represent the deformation behaviour of the powder mass during the Compaction Process. This yield model was tested and found to be appropriate to represent the Compaction Process. The staggered-incremental-iterative solution strategy has been established to solve the non-linearity in the systems of equations. Some numerical simulation results were validated through experimentation, where a good agreement was found between the numerical simulation results and the experimental data.

  • the effect of lubrication in reducing net friction in warm powder Compaction Process
    Journal of Materials Processing Technology, 2008
    Co-Authors: Mujibur Rahman, B Shahida, Faris Tarlochan, A K Ariffin
    Abstract:

    Abstract Warm powder Compaction Process is an advanced type of the conventional cold Compaction Process in producing a green compact, which is conducted at elevated temperature. Metal powder inside a die is compressed completely after heating the whole system at elevated temperature ranges from 100 °C to 150 °C. During the Compaction Process, friction occurs between the metal powder, the die surface and between the powders itself. The entire Compaction phases as well as the density of green compact are eventually affected because of the Process. The aim of this paper is to discuss the effect of lubrication in term of the mixing time, weight percent of lubricant and the density of metal powder through warm Compaction. The metal powder that used was in the Process was an iron ASC 100.29. The Compaction experiments have been conducted at 130 °C and the lubricants used was zinc stearate and carbon. It was found that the Compaction phases (Compaction and ejection) are strongly dependant on the variables used.

  • Thermal–mechanical model of warm powder Compaction Process
    Journal of Materials Processing Technology, 2001
    Co-Authors: A K Ariffin, Rahman, Norhamidi Muhamad, Jaafar Sahari
    Abstract:

    Abstract A coupled mechanical and thermal analysis of powder during the warm Compaction Process has been investigated. This paper presents the development of the numerical model to generate a green compact through uniaxial die Compaction. The powder is considered to be the rate independent thermo-elastoplastic material. The constitutive laws are derived based on a continuum approach and the governing equations are developed where the thermal strain is taken into account together with elastic and plastic strains. The Elliptical Cap failure criterion is considered to model the yielding of the material during the Process. A large displacement based finite element approach is used considering an updated Lagrangian strategy. The non-linear systems of equations are solved employing the staggered-incremental-iterative solution strategy.

Alon Mazor - One of the best experts on this subject based on the ideXlab platform.

  • A combined DEM & FEM approach for modelling roll Compaction Process
    Powder Technology, 2018
    Co-Authors: Alon Mazor, Luca Orefice, Abderrahim Michrafy, Alain De Ryck, Johannes Khinast
    Abstract:

    Roll Compaction is a continuous manufacturing Process aiming to produce particulate granules from powders. A roll press typically consists of a screw feeding system, two rolls and a side sealing. Despite its conceptual simplicity, numerical modelling of the Process is challenging due to the complexity involving two different mechanisms: feeding by the screw and powder Compaction between the rolls. To represent the materials' behaviour both in the feeding zone and in the Compaction area, a combined three-dimensional Discrete Elements Method (DEM) and Finite Elements Method (FEM) is developed in this work. The DEM, which is a more suitable method to describe the flow of granular material, is used to model the motion of particles in the feeding zone. As the granular material deforms under high pressure between rolls, FEM offers a more versatile approach to represent the powder behaviour and frictional conditions. In the proposed approach the DEM and FEM are treated as complementary methods, enabling us to take advantages of the strengths of both. In this proposed approach, the time dependent velocity field of the particles at the end of the screw feeder is evaluated as a continuous field using the coarse graining (CG) framework, which was used as input data for the FEM model. FEM is then used to simulate the powder Compaction in between the rolls, and the resultant roll pressure and ribbon relative density are obtained. Our results show a direct correlation between the particle velocity driven by the screw conveyor and the roll pressure, both oscillating with the same period. This translates into an anisotropic ribbon with a density profile varying sinusoidally along its width, with a period equal to the duration of a screw turn.

  • Modelling of roll Compaction Process by finiite element method
    2017
    Co-Authors: Alon Mazor
    Abstract:

    In the pharmaceutical industry, dry granulation by roll Compaction is a Process of size enlargement of powder into granules with good flowability for subsequent die Compaction Process. Understanding the roll Compaction Process and optimizing manufacturing efficiency is limited using the experimental approach due to the high cost of powder, time-consuming and the complexity of the Process. In this work, a 3D Finite Element Method (FEM) model was developed to identify the critical material properties, roll press designs and Process parameters controlling the quality of the product. The Drucker-Prager Cap (DPC) model was used to describe the powder Compaction behavior and was determined based on standard calibration method. To overcome the complexity involving two different mechanisms of powder feeding by the screw and powder Compaction between rolls, a novel combined approach of Discrete Element Method (DEM), used to predict the granular material flow in the feed zone and the Finite Elements Method (FEM) employed for roll Compaction, was developed. Lastly, for a more realistic roll Compaction modelling, allowing the fluctuation of the gap between rolls, a Coupled-Eulerian Lagrangian (CEL) approach was developed. FEM simulation results clearly show the effect of different Process parameters on roll pressure and density distribution in the Compaction zone of powder between the rolls. Moreover, results show that using a cheek-plates sealing system causes a nonuniform roll pressure and density distribution with the highest values in the middle and the lowest at the edges. On the other hand, the resultant pressure and density distributions with the rimmed-roll obtained higher values in the edges than in the middle and overall a more uniform distribution. The combined DEM-FEM methodology clearly shows a direct correlation between the particle velocity driven by the screw conveyor to the feed zone and the roll pressure, both oscillating in the same period. This translates into an anisotropic ribbon with a density profile varying sinusoidally along its length. To validate the results, the simulations are compared with literature and experimentally measured values in order to assess the ability of the model to predict the properties of the produced ribbons.

  • a combined dem fem approach for modelling roll Compaction Process
    Powder Technology, 2017
    Co-Authors: Alon Mazor, Luca Orefice, Abderrahim Michrafy, Alain De Ryck, Johannes Khinast
    Abstract:

    Abstract Roll Compaction is a continuous manufacturing Process aiming to produce particulate granules from powders. A roll press typically consists of a screw feeding system, two rolls and a side sealing. Despite its conceptual simplicity, numerical modelling of the Process is challenging due to the complexity involving two different mechanisms: feeding by the screw and powder Compaction between the rolls. To represent the materials' behaviour both in the feeding zone and in the Compaction area, a combined three-dimensional Discrete Elements Method (DEM) and Finite Elements Method (FEM) is developed in this work. The DEM, which is a more suitable method to describe the flow of granular material, is used to model the motion of particles in the feeding zone. As the granular material deforms under high pressure between rolls, FEM offers a more versatile approach to represent the powder behaviour and frictional conditions. In the proposed approach the DEM and FEM are treated as complementary methods, enabling us to take advantages of the strengths of both. In this proposed approach, the time dependent velocity field of the particles at the end of the screw feeder is evaluated as a continuous field using the coarse graining (CG) framework, which was used as input data for the FEM model. FEM is then used to simulate the powder Compaction in between the rolls, and the resultant roll pressure and ribbon relative density are obtained. Our results show a direct correlation between the particle velocity driven by the screw conveyor and the roll pressure, both oscillating with the same period. This translates into an anisotropic ribbon with a density profile varying sinusoidally along its width, with a period equal to the duration of a screw turn.

  • Effect of roll compactor sealing system designs: A finite element analysis
    Powder Technology, 2016
    Co-Authors: Alon Mazor, Alain De Ryck, Lucia Perez-gandarillas, Abderrahim Michrafy
    Abstract:

    In the pharmaceutical industry, the roll Compaction is part of the dry granulation Process, densifying fine powders into ribbons that will be later milled to produce granules with good flowability for subsequent die Compaction Process. Roll compactors are constructed with a sealing system, limiting the loss of powder from the sides. However, the sealing system may result in unwanted non-uniformity of the ribbon's properties. In this work, a 3D Finite Elements Method (FEM) modeling is used to analyze the roll Compaction Process and the effect of sealing system designs on the compacted ribbon's density distribution. A density dependent Drucker-Prager Cap (DPC) constitutive model for microcrystalline cellulose (Avicel PH-101) was calibrated and implemented in Abaqus/Explicit. Two different FEM models were investigated, one with a fixed side sealing called cheek plates and another where the side sealing is integrated with the bottom roll called rimmed-roll. Both numerical and experimental results clearly show the non-uniform roll pressure and density distribution for the cheek plates assembly, whereas the rimmed-roll shows an overall more uniformly distributed resultant pressure and density distribution. These results demonstrate the capability of FEM modeling to provide insight and help achieving a better understanding of the roll Compaction Process.

Luc Penazzi - One of the best experts on this subject based on the ideXlab platform.

  • Analysis of strain stress state in roller Compaction Process
    Powder Technology, 2011
    Co-Authors: Abderrahim Michrafy, Harona Diarra, John A. Dodds, Mohammed Michrafy, Luc Penazzi
    Abstract:

    The Process of drawing and densification of powdered microcrystalline cellulose by roller press in a steady state operation is analyzed using a 2D modeling with the finite element method and the modified Drucker-Prager Cap model as material behavior. Distributions of Process variables in contact surface between powder and roller such as pressure, shear stress and relative speed were predicted and used to analyze the basic mechanisms of the transport and the densification of powder between rolls. The results show clearly the existence of three contiguous zones: a phase where the powder is drawn between rolls by a sliding mechanism, a sticking phase where the powder is transported with the same velocity as the roll and where the densification by deforming the powder bed is achieved under the increase of roll pressure that reaches its peak before the neutral angle. The formed compact is then expulsed out of the gap by a slip mechanism resulting from the change of the sign of the shear stress. The predicted density distribution between the rolls, shows a gradual increase. The density reaches its maximum before the neutral point and shows values in agreement with the density of strips prepared with an instrumented roll press. The effect of varying the material parameters on the maximum pressure and the nip angle s also investigated. Beyond the description of the basic mechanisms of roller Compaction, this modeling shows a real potential of the optimization of the roller Compaction Process.

  • Analysis of strain stress state in roller Compaction Process
    Powder Technology, 2011
    Co-Authors: Abderrahim Michrafy, Harona Diarra, John A. Dodds, Mohammed Michrafy, Luc Penazzi
    Abstract:

    Symposium on Science and Technology of Powders and Sintered Materials (STPMF 2009), Montpellier, FRANCE, MAY 25-27, 2009International audienceThe Process of drawing and densification of powdered microcrystalline cellulose by roller press in a steady state operation is analyzed using a 2D modeling with the finite element method and the modified Drucker-Prager Cap model as material behavior. Distributions of Process variables in contact surface between powder and roller such as pressure, shear stress and relative speed were predicted and used to analyze the basic mechanisms of the transport and the densification of powder between rolls. The results show clearly the existence of three contiguous zones: a phase where the powder is drawn between rolls by a sliding mechanism, a sticking phase where the powder is transported with the same velocity as the roll and where the densification by deforming the powder bed is achieved under the increase of roll pressure that reaches its peak before the neutral angle. The formed compact is then expulsed out of the gap by a slip mechanism resulting from the change of the sign of the shear stress. The predicted density distribution between the rolls, shows a gradual increase. The density reaches its maximum before the neutral point and shows values in agreement with the density of strips prepared with an instrumented roll press. The effect of varying the material parameters on the maximum pressure and the nip angle s also investigated. Beyond the description of the basic mechanisms of roller Compaction, this modeling shows a real potential of the optimization of the roller Compaction Process

Mujibur Rahman - One of the best experts on this subject based on the ideXlab platform.

  • Numerical simulation and experimentation of warm metal powder Compaction Process
    Key Engineering Materials, 2011
    Co-Authors: Mujibur Rahman, A K Ariffin, Faris Tarlochan, Ramesh Singh, S.s.m. Nor
    Abstract:

    Powder Compaction at elevated temperature or known as warm Compaction is a Process of producing green compacts from metal powder, which is generally conducted between the ambient and the recrystalization temperature of the main powder constituent. Even though, warm Compaction was initiated at around 1998, not a lot of information can be found in the literature especially on the numerical simulation of the Process. Therefore, this paper presents the simulation of warm metal powder forming Process by using the developed computer code. The Elliptical Cap yield model has been used to represent the deformation behaviour of the powder mass during the forming Process at above ambient temperature. The material properties of powder mass, i. e., friction coefficient, elastic index, and plastic index, at different forming temperature, are established through warm Compaction experiment. The simulation was conducted to generate a green compact of a plain bush component. Some numerical simulation results were validated through experimentation, where a good agreement was found between the numerical simulation and the experimental results.

  • development of a finite element model of metal powder Compaction Process at elevated temperature
    Applied Mathematical Modelling, 2009
    Co-Authors: Mujibur Rahman, A K Ariffin
    Abstract:

    This paper presents the finite element modelling of metal powder Compaction Process at elevated temperature. In the modelling, the behaviour of powder is assumed to be rate independent thermo-elastoplastic material where the material constitutive laws are derived based on a continuum mechanics approach. The deformation Process of metal powder has been described by a large displacement based finite element formulation. The Elliptical Cap yield model has been used to represent the deformation behaviour of the powder mass during the Compaction Process. This yield model was tested and found to be appropriate to represent the Compaction Process. The staggered-incremental-iterative solution strategy has been established to solve the non-linearity in the systems of equations. Some numerical simulation results were validated through experimentation, where a good agreement was found between the numerical simulation results and the experimental data.

  • the effect of lubrication in reducing net friction in warm powder Compaction Process
    Journal of Materials Processing Technology, 2008
    Co-Authors: Mujibur Rahman, B Shahida, Faris Tarlochan, A K Ariffin
    Abstract:

    Abstract Warm powder Compaction Process is an advanced type of the conventional cold Compaction Process in producing a green compact, which is conducted at elevated temperature. Metal powder inside a die is compressed completely after heating the whole system at elevated temperature ranges from 100 °C to 150 °C. During the Compaction Process, friction occurs between the metal powder, the die surface and between the powders itself. The entire Compaction phases as well as the density of green compact are eventually affected because of the Process. The aim of this paper is to discuss the effect of lubrication in term of the mixing time, weight percent of lubricant and the density of metal powder through warm Compaction. The metal powder that used was in the Process was an iron ASC 100.29. The Compaction experiments have been conducted at 130 °C and the lubricants used was zinc stearate and carbon. It was found that the Compaction phases (Compaction and ejection) are strongly dependant on the variables used.