C-DEMPack Tutorial 1: Cohesive DemPack 2.0

Introduction

Before starting with this tutorial, the user is strongly encouraged to follow the G-DEMPack Tutorial 2: DemPack 2.0 to get a feeling of how the problem type works, and in particular the DEM section. This tutorial will focus mainly in the parcularities of the cohesive DEM. The user should start by downloading the File:D DEMPack2 Tutorial 5.zip. This file has already both created and assgined the groups that will be used in the simulation, as well as the mesh sizes for all groups.

Geometry

The geometry of study consists of four different continuum-DEM groups as well as two DEM-FEM rigid entities. The four cohesive groups are composed of an inlet of deformable cluster elements, a highly cohesive material in the shape of a sphere, a very little cohesive material in the shape of a paralelepiped and a membrane-like material. The program is also capable of simulating cables and solving thermal problems, as will we shown in a upcoming tutorial. It is also possible to simulate the behaviour of ice, even though this aspect is still under development. See http://www.cimnemultimediachannel.com/vpage/2/0/technology/technology/Discrete-Element-Method#11 to check the capabilities of the program in that respect.

DEM Elements

As a reference, a screenshot of the characteristics of the elements used in this simulation will be given. The user is encouraged to modify these settings to experiment a little bit and get familiar with the program. The assignation was the following:

Cohesive Groups

This section is unique and it does not exist neither in G-DEMPack nor F-DEMPack. The user must assign this attribute to any group containing cohesive entities. Only the particles tagged with this attribute will have cohesive properties and use a continuum material law. Double click on Cohesive Groups to start adding adding the different groups in this section. Note that different cohesive groups can have the same identification number, meaning that the entities belonging to those groups are cohesive among them. However, in this case there are three independent cohesive groups. The next picture shows the assignation in our sample case as a reference.

Boundary Conditions

This section is in practice identical to that of the G-DEMPack. The most significant difference is that the inlet cluster elements are deformable and breakable. The simulation captures at the end of this tutorial show an example of the behavior of this kind of cluster elements.

General Options

The structure of this section is the same as in G-DEMPack, but with a much more extense subsection of Advanced Options. The settings for this simulation are given in the picture that follows as a reference. A detailed explanation of each of the fields in this section can be found here C-DEMPack2 manual.

Solution Strategy

This section is identical to that of G-DEMPack, so no further explanation is needed. A screenshot with the value of the parameters chosen in this example can be found in the picture that follows.

Results

The structure of this section is the same as in G-DEMPack, but with an additional subsection on Postprocessing bond-related results and some other parameters linked to the Poisson ratio and the skin of the materials in the simulation. Check the C-DEMPack2 manual for a detailed explanation of every field in this section. The user is left free to choose the desired set of results to be printed.

Materials

For this example, the materials of all groups has been already set. The user is encouraged to play a little bit using different materials and compare the results. Check the C-DEMPack2 manual for a reference on the different options available. The materials used in this example were the following:

Meshing and Running

After the user has checked that everything is correctly assigned and the corresponding cohesive groups have been created, the only thing that is missing is to mesh the geometry. As said at the beginning of this tutorial, all the meshing details have been previously set for this problem, so the user must only press Ctr-G, enter a value of 0.4 and hit OK. A mesh very similar to the one that follows should be obtained:

Once obtained a valid mesh and to run the example, press Ctrl-s to save the file and hit F5 to launch the simulation.

Results

After some minutes, the simulation should be complete. Shift to Post-Process to load the results. The next four captures show the resulting simulation at different times. The user should obtain results very similar to those.

Additional DEM Tutorials

Other tutorials can be found here.