C-DEMPack2 manual

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(Created page with "Model Section ============= 1. General Application Data Domain Options This section allows the user to choose between a 2D or 3D simulation. 2. DEM The DEM section is very simi...")
 
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Model Section
+
==Model Section==
=============
+
  
1. General Application Data
+
 
 +
===General Application Data===
 
Domain Options
 
Domain Options
 
This section allows the user to choose between a 2D or 3D simulation.
 
This section allows the user to choose between a 2D or 3D simulation.
  
2. DEM
+
===DEM===
 
The DEM section is very similar to that of the non-cohesive DEMPack. Please,
 
The DEM section is very similar to that of the non-cohesive DEMPack. Please,
 
refer to [[Manual2_whatever]] for a full description of the menus in this
 
refer to [[Manual2_whatever]] for a full description of the menus in this
Line 12: Line 12:
 
will be explained.
 
will be explained.
  
2.1. Cohesive Groups
+
====Cohesive Groups====
 
This subsection allows the user to integrate one or more GiD groups into a
 
This subsection allows the user to integrate one or more GiD groups into a
 
single cohesive group with a particular collective behavior. Any GiD group with
 
single cohesive group with a particular collective behavior. Any GiD group with
 
no cohesive group assigned will be treated as a discontinuum DEM mass.
 
no cohesive group assigned will be treated as a discontinuum DEM mass.
  
2.2. Advanced Options
+
====Advanced Options====
Tangency tolerance: Choose if you want to set manually the maximum gap between  
+
*'''Tangency tolerance''': Choose if you want to set manually the maximum gap between  
 
particles at the beginning of the computation (Absolute) or if you prefer an  
 
particles at the beginning of the computation (Absolute) or if you prefer an  
 
automatic gap that tries to match a certain average Coordination Number.
 
automatic gap that tries to match a certain average Coordination Number.
Tangency tolerance value: Choose the maximum admissible gap between two particles  
+
 
 +
*'''Tangency tolerance value''': Choose the maximum admissible gap between two particles  
 
to consider them cohesive at the beginning of the computation.
 
to consider them cohesive at the beginning of the computation.
Accepted gap between neighbours: If the gap between two spheres is bigger than  
+
 
 +
*'''Accepted gap between neighbours''': If the gap between two spheres is bigger than  
 
this value, they are no longer neighbours and the bond between them breaks.
 
this value, they are no longer neighbours and the bond between them breaks.
Maximum allowed amplification ratio of the search radius: The search radius must  
+
 
 +
*'''Maximum allowed amplification ratio of the search radius''': The search radius must  
 
be amplified after the first search because particles separate, but a bond still  
 
be amplified after the first search because particles separate, but a bond still  
 
joins them. In order to keep finding all neighbours, search is amplified according  
 
joins them. In order to keep finding all neighbours, search is amplified according  
 
the the mechanical resistance, but up to this limit.
 
the the mechanical resistance, but up to this limit.
Virtual mass coefficient: for no mass reductio, set this value to 1.
+
 
Calculate rotations: If activated, torques and rotations will be calculated on the  
+
*'''Virtual mass coefficient''': for no mass reduction, set this value to 1.
 +
 
 +
*'''Calculate rotations''': If activated, torques and rotations will be calculated on the  
 
Discrete Elements. Will increase computation time slightly.
 
Discrete Elements. Will increase computation time slightly.
Rolling friction: If activated, rolling friction between particles will be  
+
 
 +
*'''Rolling friction''': If activated, rolling friction between particles will be  
 
considered.
 
considered.
Compute stress tensor: If activated, the Stress Tensor will be computed. It will  
+
 
 +
*'''Compute stress tensor''': If activated, the Stress Tensor will be computed. It will  
 
increase computation time and memory consumption.
 
increase computation time and memory consumption.
Add Poisson Effect: If active, the Poisson effect will be taken into account.
+
 
Add the effect of shear strains parallel to bonds:
+
*'''Add Poisson Effect''': If active, the Poisson effect will be taken into account.
Don't search until failure: When active, the shear strains parallel to bonds will  
+
 
 +
*'''Add the effect of shear strains parallel to bonds''':
 +
 
 +
*'''Don't search until failure''': When active, the shear strains parallel to bonds will  
 
be included in the computations.
 
be included in the computations.
Material Analysis: Activate this option to show the material test (UCS, BTS)  
+
 
 +
*'''Material Analysis''': Activate this option to show the material test (UCS, BTS)  
 
additional options.
 
additional options.
Thermal Analysis: Changes the default DEM element to Thermal-type elements and  
+
 
 +
*'''Thermal Analysis''': Changes the default DEM element to Thermal-type elements and  
 
shows additional options.
 
shows additional options.
  
2.3. Material Test
+
====Material Test====
 
When setting the Material Analysis option to Yes, this menu will show up. It allows
 
When setting the Material Analysis option to Yes, this menu will show up. It allows
 
the user the access to a Material Test Virtual Lab where several kinds of tests are  
 
the user the access to a Material Test Virtual Lab where several kinds of tests are  
 
possible, they are: UCS, Triaxial, Oedometric, Hydrostatic and BTS.
 
possible, they are: UCS, Triaxial, Oedometric, Hydrostatic and BTS.
Test type: The user must select here any of the five different test previouly listed.
+
 
Load velocity: The velocity that will be imposed to the presses that will compress  
+
*'''Test type''': The user must select here any of the five different test previouly listed.
 +
 
 +
*'''Load velocity''': The velocity that will be imposed to the presses that will compress  
 
the tested specimen.
 
the tested specimen.
Confinement pressure: This field will show up only when selecting the Triaxial or  
+
 
 +
*'''Confinement pressure''': This field will show up only when selecting the Triaxial or  
 
Hydrostatic tests.
 
Hydrostatic tests.
Mesh type: The user can choose to use the current mesh in the problem or a predefined  
+
 
 +
*'''Mesh type''': The user can choose to use the current mesh in the problem or a predefined  
 
mesh that will be loaded from a file.
 
mesh that will be loaded from a file.
Mesh path: Path to the file when using a Predefined Mesh.
+
 
Specimen length: Length of the specimen given in meters.
+
*'''Mesh path''': Path to the file when using a Predefined Mesh.
Specimen diameter: Diameter of the specimen in meters.
+
 
Top measuring group: The top press group must be assigned here. The user has also the
+
*'''Specimen length''': Length of the specimen given in meters.
 +
 
 +
*'''Specimen diameter''': Diameter of the specimen in meters.
 +
 
 +
*'''Top measuring group''': The top press group must be assigned here. The user has also the
 
possibility of printing the forces and/or torques acting in this group.
 
possibility of printing the forces and/or torques acting in this group.
Bottom measuring group: The bottom press group must be assigned here. As before, forces  
+
 
 +
*'''Bottom measuring group''': The bottom press group must be assigned here. As before, forces  
 
and/or torques can be printed for the group.
 
and/or torques can be printed for the group.
  
2.4. Thermal results
+
====Thermal results====
 
When setting the Thermal Analysis option to Yes, this menu will show up. It allows
 
When setting the Thermal Analysis option to Yes, this menu will show up. It allows
 
the user to set values of the thermal parameters. This section is currently under  
 
the user to set values of the thermal parameters. This section is currently under  
 
development.
 
development.
  
2.5. Results
+
====Results====
 
This problem type has some additional results available for printing, they are:
 
This problem type has some additional results available for printing, they are:
Skin Spheres: the contour spheres will be mark with a different color with respect to  
+
 
 +
*'''Skin Spheres''': the contour spheres will be mark with a different color with respect to  
 
the rest.
 
the rest.
Poisson Ratio: the local Poisson Ratio will be printed in a sphere-to-sphere-bond  
+
 
 +
*'''Poisson Ratio''': the local Poisson Ratio will be printed in a sphere-to-sphere-bond  
 
fashion.
 
fashion.
Print Virtual Sea Surface: This option can be used to print a virtual sea surface as  
+
 
 +
*'''Print Virtual Sea Surface''': This option can be used to print a virtual sea surface as  
 
a mesh in PostProcess. When activated, four pairs of coordinates must be entered which  
 
a mesh in PostProcess. When activated, four pairs of coordinates must be entered which  
 
will define the quadrilateral surface representing the virtual sea surface. A z=0 sea  
 
will define the quadrilateral surface representing the virtual sea surface. A z=0 sea  
 
level is assumed. This option is related to the simulation of ice in the problem type  
 
level is assumed. This option is related to the simulation of ice in the problem type  
 
and is still under development.
 
and is still under development.
 +
 
When activating the Thermal Analysis, additional thermal post-processing information  
 
When activating the Thermal Analysis, additional thermal post-processing information  
 
will be available. Nevertheless, this section is still under development.
 
will be available. Nevertheless, this section is still under development.
Show bond elements: When activating this option, the bonds connecting the center of  
+
 
 +
*'''Show bond elements''': When activating this option, the bonds connecting the center of  
 
every pair of spheres will be shown in the postprocess. The user has then the option  
 
every pair of spheres will be shown in the postprocess. The user has then the option  
 
of printing the following variables:
 
of printing the following variables:
Contact sigma: Normal stress between every pair of spheres.
+
 
Contact tau: Tangential stress between spheres.
+
*'''Contact sigma''': Normal stress between every pair of spheres.
Local contact force: Local force in the contact point of any two spheres.
+
 
Failure criterion state: Shows the current failure state or how close is the considered  
+
*'''Contact tau''': Tangential stress between spheres.
 +
 
 +
*'''Local contact force''': Local force in the contact point of any two spheres.
 +
 
 +
*'''Failure criterion state''': Shows the current failure state or how close is the considered  
 
contact to reach complete failure.
 
contact to reach complete failure.
Failure Id: Labels every contact with its corresponding Failure Type.
+
 
Mean contact area: Displays the calculation area in every contact.
+
*'''Failure Id''': Labels every contact with its corresponding Failure Type.
 +
 
 +
*'''Mean contact area''': Displays the calculation area in every contact.
  
  
Materials Section
+
==Materials Section==
=================
+
  
 
This section is very similar to that of the discontinuous DEM, but with additional fields  
 
This section is very similar to that of the discontinuous DEM, but with additional fields  
Line 109: Line 140:
 
last is addressed to study specific materials like membranes or clothes, as well as cables.
 
last is addressed to study specific materials like membranes or clothes, as well as cables.
 
Both KDEM and DEMPack laws have the following fields in common:
 
Both KDEM and DEMPack laws have the following fields in common:
Rolling Friction: value for the rolling friction. It may increase computation time slightly.
+
 
Tangential Strength: Maximum shear strength for the material.
+
*'''Rolling Friction''': value for the rolling friction. It may increase computation time slightly.
Normal Tensile Strength: Maximum tensile strength of the material.
+
 
Internal Friction Angle Coefficient: value of the static friction coefficient.
+
*'''Tangential Strength''': Maximum shear strength for the material.
 +
 
 +
*'''Normal Tensile Strength''': Maximum tensile strength of the material.
 +
 
 +
*'''Internal Friction Angle Coefficient''': value of the static friction coefficient.
 +
 
 
When activating the KDEM Mohr-Coulomb law, two specific fields show up that the user must  
 
When activating the KDEM Mohr-Coulomb law, two specific fields show up that the user must  
 
fill: the associated M-C Cohesion and Friction angle. On the other hand, when choosing the KDEM  
 
fill: the associated M-C Cohesion and Friction angle. On the other hand, when choosing the KDEM  
Line 118: Line 154:
 
It refers to the moment resistance, where 0 means no resistance at all and 1 a maximum resistance,  
 
It refers to the moment resistance, where 0 means no resistance at all and 1 a maximum resistance,  
 
which would be equivalent to the base KDEM.
 
which would be equivalent to the base KDEM.
 +
 
Finally, when activating the DEMPack constitutive law, a list of several parameters show up,  
 
Finally, when activating the DEMPack constitutive law, a list of several parameters show up,  
 
which are related to the plastic and damage branches of the stress-strain graph. They are the  
 
which are related to the plastic and damage branches of the stress-strain graph. They are the  
 
following:
 
following:
LCS1: First stiffness reduction point.
+
 
LCS2: Second stiffness reduction point.
+
*'''LCS1''': First stiffness reduction point.
LCS3: Third stiffness reduction point.
+
 
YRC1: First reduction coefficient.
+
*'''LCS2''': Second stiffness reduction point.
YRC2: Second reduction coefficient.
+
 
YRC3: Third reduction coefficient.
+
*'''LCS3''': Third stiffness reduction point.
Plastic Young Modulus: Material stiffness in the plastic zone.
+
 
Plastic Yield Stress: Plastic yield point.
+
*'''YRC1''': First reduction coefficient.
Damage Deformation Factor: Energy stored after bond fracture.
+
 
Shear Energy Coefficient: Energy stored due shear effects.
+
*'''YRC2''': Second reduction coefficient.
 +
 
 +
*'''YRC3''': Third reduction coefficient.
 +
 
 +
*'''Plastic Young Modulus''': Material stiffness in the plastic zone.
 +
 
 +
*'''Plastic Yield Stress''': Plastic yield point.
 +
 
 +
*'''Damage Deformation Factor''': Energy stored after bond fracture.
 +
 
 +
*'''Shear Energy Coefficient''': Energy stored due shear effects.
 +
 
 
Details on the previous parameters are shown in the picture that follows:
 
Details on the previous parameters are shown in the picture that follows:
  

Revision as of 15:05, 24 January 2017

Contents

Model Section

General Application Data

Domain Options This section allows the user to choose between a 2D or 3D simulation.

DEM

The DEM section is very similar to that of the non-cohesive DEMPack. Please, refer to Manual2_whatever for a full description of the menus in this section. In this manual only the particular characteristics of this problem type will be explained.

Cohesive Groups

This subsection allows the user to integrate one or more GiD groups into a single cohesive group with a particular collective behavior. Any GiD group with no cohesive group assigned will be treated as a discontinuum DEM mass.

Advanced Options

  • Tangency tolerance: Choose if you want to set manually the maximum gap between

particles at the beginning of the computation (Absolute) or if you prefer an automatic gap that tries to match a certain average Coordination Number.

  • Tangency tolerance value: Choose the maximum admissible gap between two particles

to consider them cohesive at the beginning of the computation.

  • Accepted gap between neighbours: If the gap between two spheres is bigger than

this value, they are no longer neighbours and the bond between them breaks.

  • Maximum allowed amplification ratio of the search radius: The search radius must

be amplified after the first search because particles separate, but a bond still joins them. In order to keep finding all neighbours, search is amplified according the the mechanical resistance, but up to this limit.

  • Virtual mass coefficient: for no mass reduction, set this value to 1.
  • Calculate rotations: If activated, torques and rotations will be calculated on the

Discrete Elements. Will increase computation time slightly.

  • Rolling friction: If activated, rolling friction between particles will be

considered.

  • Compute stress tensor: If activated, the Stress Tensor will be computed. It will

increase computation time and memory consumption.

  • Add Poisson Effect: If active, the Poisson effect will be taken into account.
  • Add the effect of shear strains parallel to bonds:
  • Don't search until failure: When active, the shear strains parallel to bonds will

be included in the computations.

  • Material Analysis: Activate this option to show the material test (UCS, BTS)

additional options.

  • Thermal Analysis: Changes the default DEM element to Thermal-type elements and

shows additional options.

Material Test

When setting the Material Analysis option to Yes, this menu will show up. It allows the user the access to a Material Test Virtual Lab where several kinds of tests are possible, they are: UCS, Triaxial, Oedometric, Hydrostatic and BTS.

  • Test type: The user must select here any of the five different test previouly listed.
  • Load velocity: The velocity that will be imposed to the presses that will compress

the tested specimen.

  • Confinement pressure: This field will show up only when selecting the Triaxial or

Hydrostatic tests.

  • Mesh type: The user can choose to use the current mesh in the problem or a predefined

mesh that will be loaded from a file.

  • Mesh path: Path to the file when using a Predefined Mesh.
  • Specimen length: Length of the specimen given in meters.
  • Specimen diameter: Diameter of the specimen in meters.
  • Top measuring group: The top press group must be assigned here. The user has also the

possibility of printing the forces and/or torques acting in this group.

  • Bottom measuring group: The bottom press group must be assigned here. As before, forces

and/or torques can be printed for the group.

Thermal results

When setting the Thermal Analysis option to Yes, this menu will show up. It allows the user to set values of the thermal parameters. This section is currently under development.

Results

This problem type has some additional results available for printing, they are:

  • Skin Spheres: the contour spheres will be mark with a different color with respect to

the rest.

  • Poisson Ratio: the local Poisson Ratio will be printed in a sphere-to-sphere-bond

fashion.

  • Print Virtual Sea Surface: This option can be used to print a virtual sea surface as

a mesh in PostProcess. When activated, four pairs of coordinates must be entered which will define the quadrilateral surface representing the virtual sea surface. A z=0 sea level is assumed. This option is related to the simulation of ice in the problem type and is still under development.

When activating the Thermal Analysis, additional thermal post-processing information will be available. Nevertheless, this section is still under development.

  • Show bond elements: When activating this option, the bonds connecting the center of

every pair of spheres will be shown in the postprocess. The user has then the option of printing the following variables:

  • Contact sigma: Normal stress between every pair of spheres.
  • Contact tau: Tangential stress between spheres.
  • Local contact force: Local force in the contact point of any two spheres.
  • Failure criterion state: Shows the current failure state or how close is the considered

contact to reach complete failure.

  • Failure Id: Labels every contact with its corresponding Failure Type.
  • Mean contact area: Displays the calculation area in every contact.


Materials Section

This section is very similar to that of the discontinuous DEM, but with additional fields accounting for several constitutive laws available trying to simulate the behaviour of different cohesive materials, as well as the thermal parameters. Two main classes of constitutive laws exist: the DEMPack and the KDEM. The former is addressed to study materials following a non-linear elastoplastic behavior including damage, while the latter is specially designed to simulate elastobrittle materials. The KDEM constitutive law has several derived laws, which are KDEM_Rankine, KDEM_Mohr_Coulomb and KDEM_Fabric. The first one, the base KDEM, is a standard linear-brittle behaviour constitutive law, the second and third simulate the same behavior of the first but by following the particularities of Rankine and Mohr-Coulomb criteria respectivelly, while the last is addressed to study specific materials like membranes or clothes, as well as cables. Both KDEM and DEMPack laws have the following fields in common:

  • Rolling Friction: value for the rolling friction. It may increase computation time slightly.
  • Tangential Strength: Maximum shear strength for the material.
  • Normal Tensile Strength: Maximum tensile strength of the material.
  • Internal Friction Angle Coefficient: value of the static friction coefficient.

When activating the KDEM Mohr-Coulomb law, two specific fields show up that the user must fill: the associated M-C Cohesion and Friction angle. On the other hand, when choosing the KDEM Fabric law, a Fabric Coefficient must be given. The value of this parameter goes from 0 to 1. It refers to the moment resistance, where 0 means no resistance at all and 1 a maximum resistance, which would be equivalent to the base KDEM.

Finally, when activating the DEMPack constitutive law, a list of several parameters show up, which are related to the plastic and damage branches of the stress-strain graph. They are the following:

  • LCS1: First stiffness reduction point.
  • LCS2: Second stiffness reduction point.
  • LCS3: Third stiffness reduction point.
  • YRC1: First reduction coefficient.
  • YRC2: Second reduction coefficient.
  • YRC3: Third reduction coefficient.
  • Plastic Young Modulus: Material stiffness in the plastic zone.
  • Plastic Yield Stress: Plastic yield point.
  • Damage Deformation Factor: Energy stored after bond fracture.
  • Shear Energy Coefficient: Energy stored due shear effects.

Details on the previous parameters are shown in the picture that follows:

FOTO MATERIALS_THEORY

This section is completed with two standard thermal parameters for the material: the Thermal Conductivity and the Specific Heat.

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