Input file

The Abaqus Input file (Show View > Input File) is the deck that defines the model. It contains multiple sections or option blocks, each corresponding to a specific part or characteristic of the model. The Input file tab shows the complete structure of the deck, including all its sections, while the other tabs allow you to review and edit the content of individual sections.

Keywords in the Abaqus™ simulator start with an asterisk (*), while comment lines start with two asterisks (**). For more information on the Abaqus input language, refer to the Abaqus™ manual.

Input file  General information and a description of the entire model. Section keywords are replaced by a link (shown as the section name in brackets), that points to the corresponding section of the Abaqus job description:

[Parts]

[Assembly]

[Boundary conditions]

[Materials]

Parts  The Parts tab describes the parts of the Abaqus model. Each part contains a set of parameters that define the geometry for that part.

Assemblies  The Assemblies tab contains the input to position the ‘Instances’ and ‘Parts’ data so that the model can be created. A model may contain only one assembly.

Instances  Instances represent each individual part being used in the construction of the model. The instances are defined in the Instances tab and are used in the Assemblies tab.

Important   The Parts, Assemblies and Instances tabs describe the shape and the elements of the 3D mesh. It is recommended not to change this data as it could lead to unexpected or incorrect results.

Interaction properties  Interaction properties are important when modeling fault slip. This tab describes the properties of the fault slip zone behavior on both sides of the fault. For more information, see Modeling slipping faults.

Materials  For every layer used to build the model a ‘material’ is generated. (A material is identified with the name of the horizon at the top of the layer.) The Materials tab defines the properties of the materials in the mesh. The tab consists of three frames.

The left frame shows the list of materials in the model. The upper right frame shows the minimum set of material behavior types needed to define a material in the geomechanical model such as density and elastic properties.

To be able to use mapped properties on the 3D mesh, the Abaqus material behavior types are linked to field variables within the input file. In the 'Initial conditions' (which is described in this table), the field variables are included as references to files which describe the property.

In the Dependencies field you specify which field variable(s) a material behavior type is dependent on. When focused on a material behavior type its dependency fields appears in the lower right frame.

Be aware that the dependency number you specify is an inclusive number, for example, a number 3 selects field variables 1 to 3 as dependencies, and all three will appear in the lower right frame. If this includes a field variable that is not relevant, its values are 0.

You can add other material behavior types to the material:

  • Click in the next empty Type entry field and select a type.
  • Set a dependency or enter a specific value.
  • If you add a dependency to a field variable and that variable does not yet exist in Initial conditions tab, it must be added there first. Simply type a new ‘INITIAL CONDITIONS, TYPE=FIELD, VARIABLE=sequential#, INPUT=relevant file name’ in the Initial conditions tab.
  • Add the relevant file to the Includes tab.
Important   It is not recommended to change the order or numbering of the default field variables in the Initial Conditions tab (Density, Young’s Modulus, Poisson’s Ratio). Changing this after setting the dependencies may lead to errors or unexpected results. When adding a new variable, it is suggested that you add it as the next variable in the list.

Boundary conditions  This tab defines the displacement boundary conditions, which are fixed for each simulation step. BOTTOM and OUTSIDE refer to node sets; direction 1 is east-west, direction 2 is north-south, and direction 3 is up-down.

Contact interactions  This tab is used when modeling fault slip. It describes how the two sides of a fault interact. If no fault slip occurs, the sides remain in contact; if slip occurs, modeling introduces a ‘slip zone’ with specific properties defined in the Interaction properties tab. For more information, see Modeling slipping faults.

Initial conditions  This tab is used to define the initial conditions of pore pressure stress, void ratio, field variables, and any other condition that is necessary to calculate the equilibrium between gravity, density and the initial stresses at the start of the simulation. The initial conditions may refer to certain default files, which you can edit in the Includes tab if necessary. You can also add field variables (e.g., Temperature). Make sure you add a relevant include file in the Includes tab. If you make a material dependent on the new field variable, add it in the Materials tab as well.

Steps  On this tab, the various steps for the simulation case are described. While steps are most easily created on the Steps form, this tab allows you to inspect and select the steps to be used.

To delete a step, select the step and click the Delete button. You will be prompted to confirm whether you want to remove the associated Include files. Select No if you want to use these files in a new step; select Yes, to remove them along with the deleted step.

Equilibrium_step is used during Initialization (and by default repeated at simulation to ensure equilibrium at start). It calculates the equilibrium between gravity, density and the initial stresses with which the simulation can start.

Includes  The include files describe which property or pressure field variable values the Abaqus solver applies to specific parts of the mesh or to specific node or element sets. Many include files are automatically generated during the mesh building and default file creation, but you may need to add or adapt an include file yourself. To create an include file, enter its name in the first column of the last row of the table and set the parameters. Connect the include file to a step by using its name as the file name in the relevant step (Steps tab).

Assembly includes  This tab contains a list of the assemblies included in the deck. It is strongly recommended not to make any changes, as this may lead to unexpected simulation behavior or issues.