Usage of Impact

Impact can be run from two different modes: GUI and Command modes. There is a complete GUI based environment available where a solution can be run from model to analysis. It is also possible to run the Impact solver from command line.

GUI Modules

The GUI is divided into separate modules which are described as follows

It is simple to open Impact GUI Environment. If you are using windows 32 bits, for example, just double click ImpactGUI_OGL_windows_i586.bat

If you are using Linux 64 bits, for example, you can run the shell script using the terminal command from Impact folder:

bash ImpactGUI_OGL_linux_amd64.sh
or
sh ImpactGUI_OGL_linux_amd64.sh

Pre Processor

Pre Processor is the starting point for the user. It is used for:

Pre Processor operates on a full 3D view which can be zoomed and rotated using the third mouse button either alone or in combination with CTRL and/or SHIFT key.

On the left hand side is a tree structure of the elements in the model. Elements can be selected here or in the 3D view directly.

By double clicking on a element, the properties of that element will be displayed and can be updated in the lower left corner.

There are also a range of commands:

On the top left side is a selection menu of the Graphics mode. Several options are available such as Surface which displays a shaded model. Wireframe is faster since no shading occurs. Solid is used for completely shaded view.

Modelling principles

The preprocessor works with two types of graphical objects: Geometry and Mesh. The geometry is CAD geometry but with build in mesh attributes. A curve for example can have a mesh attached to it. It can also have a material and a thickness which is automatically transferred to the mesh.

To generate a model, the user should start with points and then create curves based on these points. Finally, surfaces should be created based on the curves. If a point is later moved, the curve based on this points will change and finally the surface when the users presses the rebuild model button.

By double clicking on a geometry, the attributes of that geometry will appear on the edit field in the lower left corner. The user can change any attribute and press update to modify the model. The mesh of a surface is automatically based on the mesh of the curves which created the surface. If the mesh is modified on a curve, the mesh on the surface is also changed.

To create geometry there is a Draw tab available containing the following commands:

Curve defining commands Surface defining commands Point and Curve generating commands Finite element direct generating commands

A second tab, Modify, contains all the commands for modifying one or several objects.

Processor

The processor is where the calculation is made. It consists of a prompt window where the solver printout is shown, an editor where the indata file can be modified and a model viewer where the model described by the .in file can be seen and rotated.

The starting point is a .in file which has been saved from the preprocessor (or one written by hand). This must be loaded into the processor by the open model button. The solution process is then started by the start/stop button.

The results will automatically be written to a .flavia.res file which can be loaded into the postprocessor.

The view of the three dimensional model can be adjusted with these commands:

Post Processor

Post Processor is used to view the results from the solver. These are saved in a file ending with .flavia.res and consists of multiple time steps which can be selected on the left hand side of the viewer. This is also where you can decide what should be viewed.

To the left of the view, there is a menu to control what is to be shown


Show - This menu contains the following commands:

Result - This is where the type of element results are selected. The user can select element stresses or strains of various types.

Time step - Just on click on the time step to be shown. Try holding down the mouse button and move up/down for animation.

Graph

The grapher is used to view the results from trackers or directly from elements as curves.

Help

This is the tab to use for documentation.

Command Mode

The solution process is made in three stages:

Preparation of model

Impact has a build-in Pre Processor to prepare Fembic input file to run in Impact solver. Impact supports a range of Pre/Post Processors. To design models, you have two additional choices. Gmsh, which is completely free and unlimited; GiD which is commercial but can be run for free under a limited academic license.

Should you want to try GiD, make sure you use a version later than 6.2 since Impact uses features that are currently being implemented. You can download GiD from http://gid.cimne.upc.es

This is how you should set up GiD to Impact interface for processing:

Using Impact interface in GiD:

This is how you should set up and use Gmsh for Preprocessing:

Solving of model

The solution of the problem is initiated from the GUI by loading the file into the processor editor and pressing the run button.

In Linux system you can run the command sh Impact.sh file from the terminal, where file is the path and name of the indata file (for example, examples/3.in).

In Windows system you can run the command Impact.bat file from the command prompt, where file is the path and name of the indata file.

In the case of loading a Fembic file, make sure it ends with .in because otherwise Impact will not recognise the format. It is also important that you are in the impact directory at the time of execution.

If all goes well, you should now see the indata file being parsed by impact and the solution process initiated. Each time results are written, a notice will be written to the screen and you will see that execution is in progress. A solution can take considerable time, so be patient.

Visualization of results of calculation

The results are printed to the flavia.res and flavia.msh files. They will end up in the same directory as your indata sourcefile. These are readable from the GiD Post Processor

If you want to view the results with the internal Impact GUI Post Processor, just switch to the Post Processor tab and load the .flavia.res file. The model should now show up on the screen. Rotation, moving and zooming is done by holding down any of the mouse buttons while moving the mouse.

If you want to use GiD as a viewer:

Impact Cluster Implementation

As of version 0.5.3, Impact supports calculations performed across a networked set of clients often referred to as a cluster. This allows Impact to split up a model into smaller parts and distribute them over the network, letting a client calculate only a unique section of the model and thereby speeding up the calculation. There is no need to have a special type of network although a capacity of 100Mbit or greater is preferable. This is standard today on most PC:s.

The network communication and synchronisation is a complex topic. Therefore, Impact uses a special software to handle all this, called JavaParty. Developed by the University of Karlsruhe this software is 100% java in itself which means no further dependencies. Furthermore, JavaParty assumes there is a way to connect from one client to another without a password. Default setup uses ssh (secure shell) login and how to set this up correctly is explained at the JavaParty webpage. A link to JavaParty as well as downloads is avalilable on the Impact webpage

Impact assumes that your directory is shared across the clients in the network. This is the most common setup on a LAN and is accomplished by NFS or similar. If this is not the case, you have to arrange this with the system administrator. Reason for this assumption is that the printout of the results become significantly simpler to implement since all the clients can access the same file.

For more details on the cluster implementation, see the programmers manual