Impact Users Manual
This chapter is intended for the user more than the programmer. Reference
for the Fembic indata program is also included
Installation
Impact is a Java program which means that there is no compilation of
sourcecode or similar to be done. However, there are some programs you need to
install to be able to run Impact and to see the results.
Start by downloading the program files of impact from http://sourceforge.net/projects/impact
The file is a .zip file and must be untarred using the command
tar -xvf filename.zip if you are running Linux. For Windows users the
Winzip program will handle the expansion.
You will now have a directory for impact (highly originally called impact)
where some files and directories will reside. They should be:
- README
- jama (dir) - The directory containing classes for matrix algebra
- run (dir) - All the source code for Impact
- gui (dir) - All the source code for ImpactGUI
- Impact.gid (dir) - Configuration files for the GID pre/post processor
- manual_Users (dir) - Users manual
- manual_Programmers (dir) - Programmers manual and program installation
- examples (dir) - All the example problems for Impact (.in)
Prerequisites
To get
Impact working you need:
- A Java engine
- A Pre- and Postprocessor (optional but recommended)
Java_engine
A good Java engine is the Sun version which can be found at http://java.sun.com/j2se/1.4/download.html.
You can take either the Runtime environment or the Software Development Kit.
There are several alternative Java engines. IBM has one which is very fast
and is also recommended.
After installation, you can run the solver by going to the processor tab (assuming
you have started impact GUI and then loading in one of the examples from the examples
directory. Solution is then started by pressing the play button.
Impact will now create two outdatafiles:
- xxxxx.in.flavia.res
- xxxxx.in.flavia.msh
These files can be read by the internal postprocessor or alternatively by GID
pre-and postprocessor. Make sure to always select the .res file when viewing the results.
Solving problems with impact
The solution process is made in three stages:
- Creation of a model using a pre-processor or direct writing of the
Fembic indata file
- Solution using the Impact program
- Presentation of the results using a post-processor and the result
files from the solution
It is simplest to run Impact and the built in pre- and postprocessors from the GUI. To do that, just run the ImpactGUI.bat file in this directory if you are a Windows user
or make the ImpactGUI.sh runnable (chmod 777 ImpactGUI.sh) and run that with ./ImpactGUI if you are a Linux/Unix/Mac user.
Alternatively, just write bash ImpactGUI.sh to start.
Pre- and Postprocessor
Impact supports a range of pre- and postprocessors. The GUI actually contains a fully
functional postprocessor with a preprocessor under construction. To design models, you have
two additional choises. Gmsh, which is completely free and unlimited; GID which is commersial
but can be run for free under a limited academic license.
Should you want to try GID, you will need to download a version later than
6.2.0d 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 and use GID for Preprocessing:
- Run the installation file for GID and install the program.
- If you haven't installed Impact, proceed to do this.
- Look in the GID directory for a subdirectory called problemtypes and go there
- Make a new subdirectory called Impact
- Now copy the directory Impact.gid from where you installed Impact, making sure all files
come with it (you will find this directory under the Interfaces directory)
- The directory structure should now be GiD/problemtypes/Impact/Impact.gid/some files
- If you now start GiD, you should find Impact as an option under the DATA menu.
- Start by selecting Impact as your solver by Data->Problemtype->Impact->Impact
- Fill in the problem datas under Data->Problem Data->...
- Create a model and mesh it (read the GiD manual for how to do this)
- Set materials on all elements using Data->Materials
- Set boundary conditions on the nodes using Data->Conditions
- GiD can now export indata files to Impact via the File->Export->CalculationFile menu
This is how you should set up and use Gmsh for Preprocessing:
- Download Gmsh from http://www.geuz.org/gmsh and install.
- If you haven't installed Impact, proceed to do this.
- Create models in Gmsh and save them in format 1.0 of gmsh mesh format
- Import the .msh file into the Impact processor editor. It will then be translated.
Solving
The solution of the problem is initiated from the GUI by
loading the file into the editor and pressing the play button. You can
also write java -Xmx500m run.Impact file at the command prompt,
where file is the name of the indata file and 500m represents
allocation of 500 Megabytes of memory. If you have less you can reduce this
amount with the risk of getting out of memory errors for large models.
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 placed in the impact directory at the time
of execution.
If you are running some of the example problems supplied, you need to
add the path to the examples directory. The syntax then becomes:
java run.Impact -Xmx500mexamples/file where file applies as above.
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.
Reading the results
The results are printed to the flavia.res and flavia.msh files. They will
end up in the same directory as your sourcefile. These
are tailor made for the internal post processor, but are also
readable from the GID postprocessor
If you want to view the results with the internal postprocessor, just swith
to the postprocessor 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, start by firing up GID and switch to post
processing mode. Next read in the result file flavia.res. The mesh (flavia.msh)
file will be read automatically.
You should now see the model on the screen.
Press ctrl-d to set the timestep for deformation. Go from the top of the
menu, starting by selecting deformation and then time analysis. Select
timestep 0, magnification factor 1.0 and then press apply.
Next press ctrl-v and select the results , time analysis and contour fill.
Finally, select gausspointstress and apply.
Finally, press ctrl-m. You should now see the results as an animation.
There are plenty of ways to view your results, but I refer to the GID users
manual for that.
Summary of how you should use GiD for Post-processing (looking at the results)
- Fire up GID and switch to post-processing mode.
- Open the xxxxx.in.flavia.res
file. If all goes well, you should be able to see your model.
- Press ctrl-d to set the timestep for deformation.
- Go from the top of the menu, starting by selecting deformation and then
time analysis.
- Select timestep 0,
magnification factor 1.0 and then press apply.
- Next press ctrl-v and select the results , time analysis and contour fill.
- Finally, select gausspointstress and apply.
- Next press ctrl-m to get a nice animation!
Contact handling in Impact
Contacts in impact are handled by two element types:
- Contact_Triangle (CT)
- Contact_Line (CL)
The CT is used to sense contact between nodes and surfaces and the
CL senses contact against other CL elements. Together, these two
elements can be used to enable contact detection for most cases and
models. Both of them are classified as elements which means that they
can directly be part of a model mesh as all elements. The user can for
example model a wall or a complex rigid contact surface with them.
Since they only have the sole purpose of sensing contact, the have
no stiffness at all. This means that if they are used on their own in
the model, the nodes connecting them should be fixed by constraints to
prevent them from drifting when in contact. It also means that the user
can use them in combination with ordinary elements to provide contact
sensing where this is not default.
One example where this is useful is
when a body has been meshed using solid elements, for example an engine
block in a car. This body can then be "dressed" on the outside with a
second mesh of contact elements to provide the contact sensitivity
against other elements in the car. Any contact sensing inside the
engine block is not needed and valuable calculation time can then be
saved with this approach.
Some elements have contact sensing as default. Examples of these
are:
- Shell_C0_3
- Shell_BT_4
- Rod_2
- Beam_2
When any of these elements is created, one or several contact
elements are created by default. These are embedded inside the element
and share the element nodes. The rod and beam elements use the
Contact_Line element to sense contact. The Shell elements use the
Contact_Triangle element to sense contact against the surface and
optionally Contact_Line elements at the edges to sense contact against
other edges.
The contact elements drain quite a bit of computing resources and
as the number of elements increase, so does the amount of computing
power since the increase is more than linear. Therefore, some of the
elements have options to reduce the contact resolution. This means that
the contact sensing will be less accurate during large deformation of
the elements, but the solution will run faster. For this reason,
contact sensing has also not been implemented in the solid elements
since the user can best minimise the amount of calculations needed, by
distributing the contact element where they are needed.
The details of how contact sensing is implemented is explained in
the programming manual.
Units
Impact can handle any unit of indata as long as the user is consistent
between the different types. The following table summarizes possible
combinations for SI units, but similar principles also works for any other units:
Length |
Time |
Mass |
Force |
Pressure |
Velocity |
Density |
Energy |
Gravity |
m |
s |
Kg |
Kg m/s2 |
N/m2 |
m/s |
Kg/m3 |
Kgm2/s2 |
9.81 |
m |
s |
Kg |
N |
Pa |
m/s |
m Kg/l |
J |
9.81 |
m |
s |
g |
mN |
mPa |
m/s |
micro Kg/l |
mJ |
9.81 |
m |
s |
Mg (ton) |
KN |
KPa |
m/s |
Kg/l |
KJ |
9.81 |
m |
ms |
Kg |
MN |
MPa |
Km/s |
m Kg/l |
MJ |
9.81e-6 |
m |
ms |
g |
KN |
KPa |
Km/s |
micro Kg/l |
KJ |
9.81e-6 |
m |
ms |
Mg (ton) |
GN |
GPa |
Km/s |
Kg/l |
GJ |
9.81e-6 |
mm |
s |
Kg |
mN |
KPa |
mm/s |
M Kg/l |
micro J |
9.81e+3 |
mm |
s |
g |
micro N |
Pa |
mm/s |
g/mm3 |
nJ |
9.81e+3 |
mm |
s |
Mg (ton) |
N |
MPa |
mm/s |
Mg/mm3 |
mJ |
9.81e+3 |
mm |
ms |
Kg |
KN |
GPa |
m/s |
M Kg/l |
J |
9.81e-3 |
mm |
ms |
g |
N |
MPa |
m/s |
K Kg/l |
mJ |
9.81e-3 |
mm |
ms |
Mg (ton) |
MN |
TPa |
m/s |
G Kg/l |
KJ |
9.81e-3 |
cm |
ms |
g |
daN |
10^5 Pa (bar) |
dam/s |
Kg/l |
dJ |
9.81e-4 |
cm |
ms |
Kg |
10^4 N (KdaN) |
10^8 Pa (Kbar) |
dam/s |
K Kg/l |
hJ |
9.81e-4 |
cm |
ms |
Mg (ton) |
10^7 N(MdaN) |
10^11 Pa (Mbar) |
dam/s |
M Kg/l |
10^5 J |
9.81e-4 |
cm |
micro s |
g |
10^7 N (MdaN) |
10^11 Pa (Mbar) |
10^4 m/s |
Kg/l |
10^5 J |
9.81e-10 |
The Impact Translator Mode
Impact has a mode where it works as a translator between different file formats.
This happens when the solver is invoked with both an infile and an outfile.
Alternatively, this feature is available from the GUI by using the file import button
available in the editor.
Currently, Impact supports files that have been opened with a .msh ending and a .nas ending.
These represents a file from Gmsh or a file in Nastran format respectively, so make sure that
your sourcefile has the right ending.
Activating the translator can also be done from outside the GUI by writing the follwing at
the command prompt:
java run.Impact infile outfile
Nastran models
Impact now supports a basic Nastran to Fembic file format translation.
It can mainly be used for translating nodes and elements.
Do not expect materials or constraints to be transferred correctly.
Currently, only MAT1 and SPC1 types are available, so if you have problems translating
files, rename the materials or boundary conditions to get the processing done.
Also,if the nodes are expressed in some kind of coordinate system other than the global,
do not expect proper geometry.
The translator also has a problem with the way that engineering number format is
expressed. An example can be 0.7800-8. This will not work. When this happens, change
the number in an editor to 0.780e-8 instead.
Some programs export a nastran file where the command for a node (GRID) is expressed
as GRID*. The same applies for elements i.e. CBAR becomes CBAR*. The solution here is to
replace all * with a simple whitespace and then it should translate correctly.
To speed up the process of translation, always place the property commands (
PSHELL or similar) at the top of the file. Unless you do that, it will take ages to
translate a file.
Gmsh models
The Open Source Pre and Postprocessor Gmsh is now supported by Impact. The output
from the preprocessor (Version 1.0 of the .msh format) can be translated into
Fembic format in the same manner as for the nastran .nas file.
When creating models in Gmsh, you can configure the mesh with a couple of special
parameters that have been defined especially for interface with Impact. These parameters
are available in a .geo file which you will find in the interface directory in the Impact
file structure. The file is called impact.geo
How to use the parameters are shown in another file in the same directory called
bumper.geo. The geometry should be meshed with the mesh 2D button when running Gmsh
and then exported as a .msh file (Version 1.0 file format).
This file can then be read into the Impact editor and then saved as .in file.
The file will then automatically be translated into Fembic file format (Impacts native
file format).
The user then needs to edit the file to set the timestep and other parameters as wanted.
Fembic Indata Format
The fembic indata format is the default indata format for Impact. It is
designed to be simple to read and understand, and is written in free format
which means that you can type as you wish and do not have to put data at
specific locations in the file. A file which is written in Fembic should
have a name which ends with .in and be in ASCII format.
Comments may be included on any line but must be preceded by a # character.
Every text written behind this sign will be ignored and the parser will
continue on the next line instead.
The General syntax for this manual is that letters in bold are
required input for the command. Input in normal writing are optional.
Block Structure
A fembic file is structured in blocks. Each block starts with a keyword,
followed by data related to that block. The blocks can come in any order
and may be repeated. A block must start on a new line using any of the
keywords. Each keyword and the related data will now be described.
Commands
Command |
Elements |
Block |
Elements |
Description |
The elements that make up the finite element model
are defined within this block. Only one type of elements can be defined
within each block. |
Syntax
|
Elements of Type eltype
|
Options |
eltype |
Any type of element: Rod_2, Beam_2, Solid_Iso_6, Shell_BT_4, Contact_Triangle
|
|
Example
|
Elements of Type Shell_BT_4
|
See also
|
Rod_2, Beam, Solid_Iso_6, Shell_BT_4, Shell_C0_3
|
Command |
Beam_2 |
Block |
Elements |
Description |
This is a simple Beam element which means that it will transfer moment
and also take node rotation into account. The cross section is assumed
solid circular. |
Syntax
|
nr nodes = [node1,node2] D=diameter material=
elmaterial
|
Options |
nr |
The element number. Must be a unique number in the
model, i.e. another element cannot have the same number.
|
node1,2,.. |
The number of the first node etc.
|
diameter |
the cross section diameter of the Beam. The cross
section is solid circular.
|
elmaterial |
The name of the material that the Beam element
uses. This name must be defined under the material block.
|
|
Example
|
1 nodes = [23,24] D = 4.73 material = steel
|
See also
|
Elements, Materials, Nodes
|
Command |
Contact_Triangle |
Block |
Elements |
Description |
This is a 3 node contact element.
It has no other purpose than detecting if other nodes are about to penetrate it's surface.
If this is the case, the element will repel the node with a resulting reaction force onto itself.
This element is useful to model contact surfaces. It is also used in most of the other
finite elements to handle contact detection. |
Syntax
|
nr nodes = [node1,node2,node3] T =
thickness factor = factor friction = friction
|
Options |
nr |
The element number. Must be a unique number in the
model, i.e. another element cannot have the same number.
|
node1,2,.. |
|
Nodes are defined in a counter clockwise direction as shown in the
figure. Results from the element can be local stresses and strains.
The picture shows the local axes where the x-axis direction are
primarily defined by node 1 and 2.
The z-axis is normal to the shell surface.
The local y-axis is defined to be octagonal to the x-axis and z-axis.
|
|
thickness |
is the thickness of the contact element. The thickness
is assumed to be constant over the element width. Nodes outside the thickness are not assumed to
be in contact. The contact zone extends to half the thickness on each side of the element.
|
factor |
The repelling force to be used when a node penetrates.
The force will increase linearly as the node intrudes further.
|
friction |
The friction coefficient to be used. Usually between 0.2 and 0.8
depending on material and condition. Only useful if contact is enabled.
If not set, friction is disabled.
|
|
Example
|
1 nodes = [113,118,110] t = 1.0 factor = 100 friction = 0.2
|
See also
|
Elements, Nodes, Shell_C0_3, Shell_BT_4, Contact_Line
|
Command |
Contact_Line |
Block |
Elements |
Description |
This element is a two node contact element of a line segment. The element
will provide contact sensitivity within the diameter of the line. Also ends are detected
within the radius. Contact is sensed against nodes and other contact_line elements. |
Syntax
|
nr nodes = [node1,node2] D=diameter
factor = c_factor friction = c_friction contact = c_type
|
Options |
nr |
The element number. Must be a unique number in the
model, i.e. another element cannot have the same number.
|
node1,2,.. |
The number of the first node etc.
|
diameter |
the cross section diameter of the element. The cross
section is solid circular.
|
c_factor |
The contact factor. This is the reaction force at full penetration of contact node.
If nothing is specified, default is 10.
|
c_friction |
The friction coefficient to be used. Usually between 0.2 and 0.8
depending on material and condition. Only useful if contact is enabled.
If not set, friction is disabled.
|
c_type |
Contact type. Can be OFF to disable contact. Default contact type is BASIC which means
that contact sensing is enabled.
|
|
Example
|
1 nodes = [23,24] D = 4.73
|
See also
|
Elements, Nodes, Shell_C0_3, Shell_BT_4, Contact_triangle
|
Command |
Rod_2 |
Block |
Elements |
Description |
This element is a two node element of a Rod. The cross section
will shrink as the element extends which is important as the rod leaves
the elastic state and becomes plastic. |
Syntax
|
nr nodes = [node1,node2] D=diameter material=
elmaterial factor = c_factor friction = c_friction contact = c_type
|
Options |
nr |
The element number. Must be a unique number in the
model, i.e. another element cannot have the same number.
|
node1,2,.. |
The number of the first node etc.
|
diameter |
the cross section diameter of the rod. The cross
section is solid circular.
|
elmaterial |
The name of the material that the rod element
uses. This name must be defined under the material block.
|
c_factor |
The contact factor. This is the reaction force at full penetration of contact node.
If nothing is specified, default is the same as for the contact_line element.
|
c_friction |
The friction coefficient to be used. Usually between 0.2 and 0.8
depending on material and condition. Only useful if contact is enabled.
If not set, friction is disabled.
|
c_type |
Contact type. Can be OFF to disable contact. Default contact type is BASIC which means
that a Contact_Line element will represent the rod.
|
|
Example
|
1 nodes = [23,24] D = 4.73 material = steel
|
See also
|
Elements, Materials, Nodes
|
Command |
Beam_Spring_2 |
Block |
Elements |
Description |
This element is a two node beam spring element. Since it is a spring, both
the stiffness and damping can be defined in six directions. The element relies on a local
coordinate system which is set up along the element. Therefore, this spring cannot be used if
the nodes are at identical position, i.e. the element length is 0. The coordinate system
is constantly updated as the element moves. Note that time step issues for this element often be
related to the fact that inertia has not been defined on both the connecting nodes.
|
Syntax
|
nr nodes = [node1,node2,node3] material=
elmaterial D = diameter factor = c_factor friction = c_friction contact = c_type
|
Options |
nr |
The element number. Must be a unique number in the
model, i.e. another element cannot have the same number.
|
node1,2,3 |
Node 1 and 2 are the start and end nodes respectively. The third
node is a control node which defines the plane for the local y-axis of the element.
The local x-axis runs from node 1 to node 2. This axis, together with the control node
sets up a plane wherein the y-axis will be. The Y-axis is always perpendicular to the
x-axis. The local z-axis is then perpendicular to the plane.
|
elmaterial |
The name of the material that the spring element
uses. This material must be of type spring and be defined in the material block.
The material defines all the stiffness attributes for the element.
|
diameter |
The cross section diameter of the spring. This is only used for
the contact search. Any node within this diameter will be concidered in contact.
This does not have to be defined if contact is not enabled.
|
c_factor |
The contact factor. This is the reaction force at full penetration of contact node.
If nothing is specified, default is the same as for the contact_line element. This
does not have to be defined if contact is not enabled.
|
c_friction |
The friction coefficient to be used. Usually between 0.2 and 0.8
depending on material and condition. Only useful if contact is enabled.
If not set, friction is disabled.
|
c_type |
Contact type. Can be set to BASIC to enable contact. Contact is disabled
by default for this element.
|
|
Example
|
1 nodes = [23,24,27] material = attrib1
|
See also
|
Elements, Materials, Nodes
|
Command |
Shell_BT_4 |
Block |
Elements |
Description |
This is a 4 node shell element based on the classical Belytchko-Tsai formulation.
It is a very robust design which has become the workhorse in explicit finite
element simulations. The element has only one integration point which means
that the result are only calculated in one point which is situated in the
middle of the element. The advantage is that the element is very fast. The
drawback is that it is sensitive to hourglassing. To prevent this, there
is an additional compensation built in to the formulation, called hourglass
control. |
Syntax
|
nr nodes = [node1,node2,node3,node4] T =
thickness material = elmaterial NIP = noip PIP = nopip SHEAR_FACTOR =
shearfactor HOURGLASS = hglass MHC = mhc OOPHC = oophc
RHC = rhc LOAD = loadname FACTOR = c_factor CONTACT = c_type
FRICTION = friction THINNING = thinning
|
Options |
nr |
The element number. Must be a unique number in the
model, i.e. another element cannot have the same number.
|
node1,2,.. |
|
Nodes are defined in a counter clockwise direction as shown in the
figure. Results from the element can be local stresses and strains.
The picture shows the local axes where the x-axis direction are
primarily defined by node 1 and 2.
The z-axis is normal to the shell surface.
The local y-axis is defined primarily by node 1 and 4.
|
|
thickness |
is the thickness of the shell. The thickness
is assumed to be constant over the element width.
|
elmaterial |
The name of the material that the shell element
uses. This name must be defined under the material block.
|
noip |
the number of integration points through the thickness
of the element. All from 1 up to 5 integration points are possible. A minimum
of three integration points are recommended.
|
nopip |
the number of the integration point which results will be
printed in the result file. Can be anything from 1 up to NIP.
If nothing is specified, it will be the middle point in the shell thickness, for
example if NIP = 5, PIP will be equal to 3.
|
shearfactor |
the arbitrary parameter used to enforce the Kirchhoff
normality condition as the shell become thin. Default value is 1.0.
|
hglass |
a switch to enable or disable hourglass control on the
element. It can be either ON or OFF. Default is ON.
|
mhc |
the Membrane Hourglass Control factor. This factor is multiplied
with the calculated hourglass forces acting in the shell membrane plane.
Default is 0.1.
|
oophc |
the Out Of Plane Hourglass Control factor. This factor
is multiplied with the calculated hourglass forces acting out of the membrane
plane, causing ex. twist of the element. Default is 0.1.
|
rhc |
the Rotational Hourglass Control factor. This factor is
multiplied with the calculated hourglass moments. Default is 0.1.
|
loadname |
Name of a load defined under the load block. Pressure onto the shell element is defined this way.
|
c_factor |
The contact factor. This is the reaction force at full penetration of contact node.
|
c_type |
Contact type. Can be OFF to disable contact. Default contact type is BASIC which means
that two Contact_Triangle elements will represent the surface. This works fine for small deformations of the
element. ADVANCED will use four Contact_Triangle elements and be able to handle self contact within the element
itself, but at a cost of calculation time. EDGE enables edge contact sensitivity along the edges
of the element together with the standard surface contact sensitivity. ADVANCED_EDGE does the latter but together
with the advanced contact surface model which uses four Contact_Triangle elements.
|
friction |
The friction coefficient to be used. Usually between 0.2 and 0.8
depending on material and condition. Only useful if contact is enabled.
If not set, friction is disabled.
|
thinning |
Determines if the shell should reduce thickness at large
strains. Useful in pressing simulations. Default is ON. It can be disabled by
setting equal to OFF.
|
|
Example
|
1 nodes = [113,118,110,106] nip = 5 t = 1.0 material = steel load = pres
|
See also
|
Elements, Materials, Nodes, Shell_C0_3
|
Command |
Shell_C0_3 |
Block |
Elements |
Description |
This is a 3 node shell element based on the classical C0 formulation by Belytchko et. al.
It complement the BT_4 shell and is common in explicit finite element simulations.
The element has only one integration point which means that the result are only calculated in one point
which is situated in the middle of the element. The advantage is that the element is very fast. Unlike
the BT_4 element, this element does not need hourglass control. Triangulars are however by it's nature
stiffer than the BT_4 element which means it should be used with care. |
Syntax
|
nr [node1,node2,node3] T =
thickness material = elmaterial NIP = noip PIP = nopip LOAD = loadname
FACTOR = c_factor CONTACT = c_type FRICTION = friction
THINNING = thinning
|
Options |
nr |
The element number. Must be a unique number in the
model, i.e. another element cannot have the same number.
|
node1,2,.. |
|
Nodes are defined in a counter clockwise direction as shown in the
figure. Results from the element can be local stresses and strains.
The picture shows the local axes where the x-axis direction are
primarily defined by node 1 and 2.
The z-axis is normal to the shell surface.
The local y-axis is defined to be octagonal to the x-axis and z-axis.
|
|
thickness |
is the thickness of the shell. The thickness
is assumed to be constant over the element width.
|
elmaterial |
The name of the material that the shell element
uses. This name must be defined under the material block.
|
noip |
the number of integration points through the thickness
of the element. All from 1 up to 5 integration points are possible. A minimum
of three integration points are recommended.
|
nopip |
the number of the integration point which results will be
printed in the result file. Can be anyting from 1 up to NIP.
If nothing is specified, it will be the middle point in the shell thickness, for
example if NIP = 5, PIP will be equal to 3.
|
loadname |
Name of a load defined under the load block. Pressure onto the shell element is defined this way.
|
c_factor |
The contact factor. This is the reaction force at full penetration of contact node.
|
c_type |
Parameter to set contact sensitivity type. Can be set to OFF to disable contact.
If unspecified, contact is enabled for surface only. If set to EDGE, the surface contact will be complemented
with edge contact sensitivity.
|
friction |
The friction coefficient to be used. Usually between 0.2 and 0.8
depending on material and condition. Only useful if contact is enabled.
If not set, friction is disabled.
|
thinning |
Determines if the shell should reduce thickness at large
strains. Useful in pressing simulations. Default is ON. It can be disabled by
setting equal to OFF.
|
|
Example
|
1 nodes = [113,118,110] nip = 5 t = 1.0 material = steel load = pres
|
See also
|
Elements, Materials, Nodes, Shell_BT_4
|
Command |
Solid_Iso_6 |
Block |
Elements |
Description |
This is a simple isoparametric solid element with eight integration points
as showed in the figure. The element is available with either one integration
point which is then situated in the middle of the element, or eight integration
points. The benefit of having eight points are the the element will be
more stable since hourglass modes cannot occur. At the time of writing,
there is no hourglass control algorithm implemented which enables a stable
use of one integration point which means that this configuration is currently
not recommended. The results from the element are stresses and strains in
global directions. |
Syntax
|
nr [node1,node2,node3,node4,
node5,node6,node7,node8] material=
elmaterial NIP=noip
|
Options |
nr |
The element number. Must be a unique number in the
model, i.e. another element cannot have the same number.
|
node1,2,.. |
|
Nodes are defined as shown in the figure where the local axes are shown as well.
Results from the element can be local stresses and strains.
Other types of solid elements can be created by collapsing the element edges. This
is achieved by assigning the same node number to the original nodes on the cube element.
For example, the wedge would be achieved by assigning node nr 1 on position 1 and 2 for
the solid element.
In general, the collapse of elements are not as good as rewriting them from scratch.
They are however possible to use, but will not give optimal results, so be aware of this
when using them. Note also that the autostep currently does not work well for a degenerated
element. A fixed timestep must be set.
|
|
noip |
the number of integration points in the element;
can either be 1 or 8. This will also change the result files since results
are calculated in each integration point and the data from each point
will then be printed.
|
elmaterial |
The name of the material that the rod element
uses. This name must be defined under the material block.
|
|
Example
|
1 nodes = [23,24,34,42,65,76,89,33] material = steel nip = 8
2 nodes = [23,23,34,42,65,65,89,33] material = steel nip = 8
|
See also
|
Elements, Materials, Nodes
|
Command |
Nodes |
Block |
Nodes |
Description |
The node block starts with the keyword nodes on a single line. The
following lines should then specify the nodes with one node per line. Impact
is designed for three dimensional space problems which means that for each
node, all three space coordinates must be defined at all times. If a two
dimensional problem is to be solved, each node must be constrained from
movement in the third dimension. |
Syntax
|
Nodes
|
Options |
- |
Example
|
Nodes
|
See also
|
Node
|
Command |
Node |
Block |
Nodes |
Description |
This command defines a node. Impact
is designed for three dimensional space problems which means that for each
node, all three space coordinates must be defined at all times. If a two
dimensional problem is to be solved, each node must be constrained from
movement in the third dimension. |
Syntax
|
nr X = xcoord Y = ycoord Z = zcoord
constraint = cname loads = lname M = mass Ixx = x_inertia
Iyy = y_inertia Izz = z_inertia Ixy = xy_inertia Iyz = yz_inertia Ixz = xz_inertia
|
Options |
xcoord, ycoord, zcoord |
the space coordinates for the
node in respective direction. The numbers can contain decimals.
|
cname |
the name of the constraint set that the node should obey.
The constraint set must be defined elsewhere in the file under the constraint
block. Only one constraint set can be applied on each node. This is an
optional parameter and does not have to be defined if the node is free.
|
lname |
the name of the load set that the node should use. The
load set must be defined elsewhere in the file under the load block. Only
one load set can be applied to each node. This is an optional parameter
and does not have to be defined if there is no load on the node.
|
mass |
the weight of the concentrated mass applied to the node. The mass is applied to all spatial directions.
|
x_inertia |
The inertia around global x-axis applied to the node. |
y_inertia |
The inertia around global y-axis applied to the node. |
z_inertia |
The inertia around global z-axis applied to the node. |
xy_inertia |
The xy inertia component. The yx component is assumed equal. |
yz_inertia |
The yz inertia component. The zy component is assumed equal. |
xz_inertia |
The xz inertia component. The zx component is assumed equal. |
|
Example
|
Nodes
|
See also
|
Node
|
Command |
Constraints |
Block |
Constraints |
Description |
Under this block heading, the constraint sets are defined. Each set must
be defined on a single line. |
Syntax
|
Constraints of type ctype
|
Options |
ctype |
Any type of constraint: Boundary_Condition, Rigid_Body
|
|
Example
|
Constraints of type Boundary_Condition
|
See also
|
Constraint, Node, Load
|
Command |
Boundary_Condition |
Block |
Constraints |
Description |
Defines a boundary condition constraint. A constraint controls movement for the
nodes in different directions by setting the acceleration and velocity
for the node. Any given combination can be set. There is no need to define
all the variables. If none is set, the default value is that the node will
be uncontrolled in that direction. |
Syntax
|
name ax = value ay = value az = value
vx = value vy = value vz = value arx = value
ary = value arz = value vrx = value vry = value
vrz = value axis = [node1,node2,node3] update = upd
|
Options |
name |
Name of the constraint. Must be unique.
|
value |
Value of the constraint. Can be either a simple number (constant)
or alternatively a variable over time defined as [t1,y1,t2,y2,...,tn,yn] where y1
is the value at time t1 and so on. At this stage, y1 can also be off which means
that the constraint will not be effective from this time forward until a new value is set.
|
node1,node2,node3 |
These nodes set up the local coordinate system for the boundary
condition. If these are specified, the values specified in the constraint will be
assumed to be relating to this local coordinate system. The local x-axis of the
system runs from node1 to node2. Local z-axis is then normal to the plane defined
by this x-axis and a vector from node1 to node3. Finally, the y-axis is normal to
the x- and z-axis.
|
upd |
The update option is connected to the axis option. If the local
coordinate system is defined and update is set to ON, the nodes defining the
coordinate system will be continuosly scanned and the system updated. This means
the system can rotate over time.
|
|
Example
|
exampleconstraint ax = [0,0,1,1.5,5,off,6,3,100,3] ay = 3.0 az = 0.0
|
See also
|
Node, Load
|
Command |
Rigid_Body |
Block |
Constraints |
Description |
Defines a rigid body constraint. The nodes referring to this constraint
are all considered part of a single rigid body. They are all connected to the master node.
If specified, the master node can automatically be placed in the centre of gravity for the body.
The movement of the body will be controlled from the master node, on which an ordinary boundary
condition or load can be placed. The master node will automatically be given the mass and inertia
for the rigid body, based on the slave nodes mass, inertia and position. |
Syntax
|
name master_node = nnum update_position = updt
|
Options |
name |
Name of the constraint. Must be unique.
|
nnum |
Node number of the master node. The node will be moved automatically
to the centre of gravity of the rigid body before the solution starts.
|
updt |
If this is set to ON, the master node will automatically be moved
to the centre of mass for the rigid body before the solution starts.
|
|
Example
|
rb1 master_node = 25
|
See also
|
Boundary_Condition, Node
|
Command |
Loads |
Block |
Loads |
Description |
Under this block heading, the load sets are defined. Each set must
be defined on a single line. |
Syntax
|
Loads
|
Options
|
- |
Example
|
Loads
|
See also
|
Load, Node, Constraint
|
Command |
Load |
Block |
Loads |
Description |
The loads block is initiated by the heading above on a single line. The
loads themselves follows, defined one per line. A load set is applied
on nodes or some elements. It consists of concentrated forces in any direction defined by
their x,y and z components. Accelerations, such as gravity can also be
defined here. Pressure can also be defined. |
Syntax
|
name fx = value fy = value fz = value
mx = value my = value mz = value ax = acc
ay = acc az = acc arx = acc ary = acc
arz = acc p = pressure
|
Options |
name |
Name of the load. Must be unique.
|
value |
Value of the load. Can be either a simple number (constant)
or alternatively a variable over time defined as [t1,y1,t2,y2,...,tn,yn] where y1
is the value at time t1 and so on. At this stage, y1 can also be off which means
that the load will not be effective from this time forward until a new value is set.
|
acc |
Value of the acceleration. Accelerations are added to the load on a node which
makes this the way to simulate gravity. Acceleration can be either a simple number (constant)
or alternatively a variable over time defined as [t1,y1,t2,y2,...,tn,yn] where y1
is the acceleration at time t1 and so on. At this stage, y1 can also be off which means
that the acceleration will not be effective from this time forward until a new value is set.
|
pressure |
Value of the pressure. Can be either a simple number (constant)
or alternatively a variable over time defined as [t1,y1,t2,y2,...,tn,yn] where y1
is the pressure at time t1 and so on. At this stage, y1 can also be off which means
that the pressure will not be effective from this time forward until a new value is set.
|
|
Example
|
exampleload ax = [0,0,1,1.5,5,off,6,3,100,3] p = 3.0
|
See also
|
Node, Load
|
Command |
Materials |
Block |
Materials |
Description |
A specific material is defined by setting the parameters of a specific
material law. There are several material laws available, depending on material
choice. There are laws that are suitable for metals and other more suitable
for foams, which may behave differently. The material law is then assigned
to one or several elements in the element definition. |
Syntax
|
Materials of type mtype
|
Options |
mtype |
The name of a specific material law. After
each block heading, the specific materials are listed with the parameters
defined. One material per line.
|
|
Example
|
Materials of Type Elastic
|
See also
|
Elastic, Elastoplastic
|
Command |
Elastic |
Block |
Materials |
Description |
This is a simple elastic material law. |
Syntax
|
name E = yvalue RHO = dvalue NU = nuvalue FAILURE_STRAIN = fstrain FAILURE_STESS = fstress |
Options |
name |
Name of the material. Must be unique. |
yvalue |
Young's modulus for the material. |
dvalue |
The density of the material. |
nuvalue |
Poisson's constant of the material. |
fstrain |
The strain at which the material fractures. If an element reaches this
strain, it will be removed from the simulation. |
nuvalue |
The stress at which the material fractures. If an element reaches this
stress, it will be removed from the simulation. |
|
Example
|
steel E = 210 D = 0.0000078 NU = 0.3
|
See also
|
Elements, Materials, Elastoplastic
|
Command |
Elastoplastic |
Block |
Materials |
Description |
This is an isoparametric elasto-plastic material law. The elastic Young's modulus
defines the stress-strain relation up to the yield stress. Above yield stress, there are several options.
The plastic behaviour can be described by the plastic modulus (EP) which defines a linear relation between
the stress and effective plastic strain. This relation can also be a curve, defined by a range of stress/strain
coordinates. The EP in this case has no function and can be omitted. Finally, the relation can also be
dependent on the strain rate in which several stress/strain curves are defined together with a parameter
setting the velocity for which each curve is representative. The stress for a certain effective strain value is
detemined as a linear interpolation from these curves. |
Syntax
|
name E = yvalue RHO = dvalue NU = nuvalue YIELD_STRESS = svalue
EP = fvalue Y1,Y2.. Y9 = svalue V1,V2..V9 = vvalues FAILURE_STRAIN = fstrain FAILURE_STESS = fstress |
Options |
name |
Name of the material. Must be unique. |
yvalue |
Young's modulus for the material. |
dvalue |
The density of the material. |
nuvalue |
Poisson's constant of the material. |
svalue |
The yield stress of the material. If this is a single number,
the EP variable must be set in order to define a linear plastic
relation. The second option is to define the yield stress as a
range of strain/stress coordinate pairs.
Example is [eps0,stress0,eps1,stress2,....,epsn,stressn]. Remember
that the strain is effective plastic strain which is equal to
zero at initial yield. When the Y1,2... parameters are used, this
stress/strain curve is defined for a certain strain rate, defined
in the corresponding vvalue |
fvalue |
is the plastic modulus or tangent modulus in the plastic region.
If a curve is defined for the yield stress, this parameter is not
needed. |
vvalue |
is the strain rate for which the Yx curve is defined. The V1 value
defines the strain rate for Y1 and so on. The stress/strain curve for
a zero velocity is defined in the ordinary YIELD_STRESS parameter. |
fstrain |
The strain at which the material fractures. If an element reaches this
strain, it will be removed from the simulation. |
nuvalue |
The stress at which the material fractures. If an element reaches this
stress, it will be removed from the simulation. |
|
Example
|
epsteel E = 210 RHO = 0.0000078 NU = 0.3 YIELD_STRESS = 0.180 EP = 0.1
steel2 E = 210 RHO = 0.0000078 NU = 0.3 YIELD_STRESS = [0,0.180,0.3,0.220,2.0,0.250]
v_steel E = 210 RHO = 0.0000078 NU = 0.3 YIELD_STRESS = [0,0.180,0.3,0.220] V1 = 0.2 Y1 = [0,0.200,0.3,0.240]
|
See also
|
Elements, Materials, Elastic
|
Command |
Spring |
Block |
Materials |
Description |
This is a dummy material which defines all the spring stiffnesses and
damping for a spring element. It cannot be used together with any other element types. Stiffness
and damping can be defined as a function or constant for all directions. |
Syntax
|
name KX = kxvalue KY = kyvalue KZ = kzvalue KRX = krxvalue KRY = kryvalue KRZ = krzvalue
CX = cxvalue CY = cyvalue CZ = czvalue CRX = crxvalue CRY = cryvalue CRZ = crzvalue |
Options |
name |
Name of the material. Must be unique. |
kxvalue |
The stiffness along the local x-axis. Can be defined as a constant or a function of the local x-displacement.
If a function is wanted, the syntax shuld be kx = [d0,K0,d1,K1,...,dN,KN]. By default, this stiffness is assumed 0. |
kyvalue |
The stiffness along the local y-axis. Can be defined as a constant or a function of the local y-displacement.
By default, this stiffness is assumed to be the same as for KX. |
kzvalue |
The stiffness along the local z-axis. Can be defined as a constant or a function of the local z-displacement.
By default, this stiffness is assumed to be the same as for KX. |
krxvalue |
The stiffness around the local x-axis. Can be defined as a constant or a function of the local x-rotation.
By default, this stiffness is assumed 0. |
kryvalue |
The stiffness around the local y-axis. Can be defined as a constant or a function of the local y-rotation.
By default, this stiffness is assumed to be the same as for KRX. |
krzvalue |
The stiffness around the local z-axis. Can be defined as a constant or a function of the local z-rotation.
By default, this stiffness is assumed to be the same as for KRX. |
cxvalue |
The damping along the local x-axis. Can be defined as a constant or a function of the local x-displacement.
If a function is wanted, the syntax shuld be cx = [d0,C0,d1,C1,...,dN,CN]. By default, this damping is assumed 0. |
cyvalue |
The damping along the local y-axis. Can be defined as a constant or a function of the local y-displacement.
By default, this damping is assumed to be the same as for CX. |
czvalue |
The damping along the local z-axis. Can be defined as a constant or a function of the local z-displacement.
By default, this damping is assumed to be the same as for CX. |
crxvalue |
The damping around the local x-axis. Can be defined as a constant or a function of the local x-rotation.
By default, this damping is assumed 0. |
cryvalue |
The damping around the local y-axis. Can be defined as a constant or a function of the local y-rotation.
By default, this damping is assumed to be the same as for CRX. |
crzvalue |
The stiffness around the local z-axis. Can be defined as a constant or a function of the local z-rotation.
By default, this damping is assumed to be the same as for CRX. |
|
Example
|
attrib KX = 10 CX = [0,0,1,20,2,off,3,30,45,0]
|
See also
|
Elements, Materials, Elastoplastic
|
Command |
Trackers |
Block |
Trackers |
Description |
The trackers are used to track result data from a solution. There are several different
trackers, each specially tailored for different results. |
Syntax
|
Trackers of Type ttype
|
Options |
ttype |
Any type of tracker: Nodeforce, Sectionforce, etc
|
|
Example
|
Trackers of Type Nodeforce
|
See also
|
Nodeforce, Sectionforce
|
Command |
Nodeforce |
Block |
Trackers |
Description |
This tracker reads the forces from one or several nodes and plots the result into a file.
The file is currently readable by the GID pre/postprocessor but the tracker can also print in a different
fileformat. This is controlled by the Trackwriter command. Target is a value set by the user. If this
value is reached during simulation, a file will be written (with extension .target). This is useful
when debugging new versions of Impact. |
Syntax
|
nr nodes = [tnode,tnode,...,tnode] DIRECTION = dir FILENAME = fname TARGET = [ttime,timetol,tvalue,valuetol]
|
Options |
nr |
The tracker number. Must be a unique number in the
model, i.e. another nodetracker cannot have the same number.
|
tnode |
The number of the node to track forces from.
|
dir |
The direction of the force to track. Can be either 'X', 'Y' or 'Z'. It is also
possible to select components thereof by adding a - or +, i.e. 'X+' will plot the component
acting in the positive X direction. If only X is used, the sum of the positive and negative
component will be plotted.
|
filename |
The name of the file of which the nodetracker should write. Must be a unique name for each
nodetracker.
|
ttime |
The time where the target is to be checked.
|
ttol |
The tolerance for the target time
|
tvalue |
The target value.
|
valuetol |
The tolerance for the target value
|
|
Example
|
1 nodes = [23] direction = x+ filename = nodeforce.trk
|
See also
|
Trackwriter, Sectionforce, Trackers
|
Command |
Nodemoment |
Block |
Trackers |
Description |
This tracker reads the moments from one or several nodes and plots the result into a file.
The file is currently readable by the GID pre/postprocessor but the tracker can also print in a different
fileformat. This is controlled by the Trackwriter command. Target is a value set by the user. If this
value is reached during simulation, a file will be written (with extension .target). This is useful
when debugging new versions of Impact. |
Syntax
|
nr nodes = [tnode,tnode,...,tnode] DIRECTION = dir FILENAME = fname TARGET = [ttime,timetol,tvalue,valuetol]
|
Options |
nr |
The tracker number. Must be a unique number in the
model, i.e. another nodetracker cannot have the same number.
|
tnode |
The number of the node to track moments from.
|
dir |
The direction of the moment to track. Can be either 'X', 'Y' or 'Z'. It is also
possible to select components thereof by adding a - or +, i.e. 'X+' will plot the component
acting in the positive X rotation direction. If only X is used, the sum of the positive and negative
component will be plotted.
|
filename |
The name of the file of which the nodetracker should write. Must be a unique name for each
nodetracker.
|
ttime |
The time where the target is to be checked.
|
ttol |
The tolerance for the target time
|
tvalue |
The target value.
|
valuetol |
The tolerance for the target value
|
|
Example
|
1 nodes = [23] direction = x+ filename = nodemoment.trk
|
See also
|
Trackwriter, Nodeforce, Sectionforce, Trackers
|
Command |
NodeDisplacement |
Block |
Trackers |
Description |
This tracker reads the displacement of a single node and plots the result into a file.
The file is currently readable by the GID pre/postprocessor but the tracker can also print in a different
fileformat. This is controlled by the Trackwriter command. Target is a value set by the user. If this
value is reached during simulation, a file will be written (with extension .target). This is useful
when debugging new versions of Impact. |
Syntax
|
nr node = [tnode] DIRECTION = dir FILENAME = fname TARGET = [ttime,timetol,tvalue,valuetol]
|
Options |
nr |
The tracker number. Must be a unique number in the
model, i.e. another nodetracker cannot have the same number.
|
tnode |
The number of the node to track displacement from.
|
dir |
The direction of the displacement to track. Can be either 'X', 'Y' or 'Z'
|
filename |
The name of the file of which the nodetracker should write. Must be a unique name for each
nodetracker.
|
ttime |
The time where the target is to be checked.
|
ttol |
The tolerance for the target time
|
tvalue |
The target value.
|
valuetol |
The tolerance for the target value
|
|
Example
|
1 node = [23] direction = z filename = nodedisp.trk
|
See also
|
Trackwriter, Sectionforce, Trackers
|
Command |
NodeAcceleration |
Block |
Trackers |
Description |
This tracker reads the acceleration of a single node and plots the result into a file.
The file is currently readable by the GID pre/postprocessor but the tracker can also print in a different
fileformat. This is controlled by the Trackwriter command. Target is a value set by the user. If this
value is reached during simulation, a file will be written (with extension .target). This is useful
when debugging new versions of Impact. |
Syntax
|
nr node = [tnode] DIRECTION = dir FILENAME = fname TARGET = [ttime,timetol,tvalue,valuetol]
|
Options |
nr |
The tracker number. Must be a unique number in the
model, i.e. another nodetracker cannot have the same number.
|
tnode |
The number of the node to track acceleration from.
|
dir |
The direction of the acceleration to track. Can be either 'X', 'Y' or 'Z'
|
filename |
The name of the file of which the nodetracker should write. Must be a unique name for each
nodetracker.
|
ttime |
The time where the target is to be checked.
|
ttol |
The tolerance for the target time
|
tvalue |
The target value.
|
valuetol |
The tolerance for the target value
|
|
Example
|
1 node = [23] direction = z filename = nodeacc.trk
|
See also
|
Trackwriter, Sectionforce, Trackers
|
Command |
Sectionforce |
Block |
Trackers |
Description |
This tracker collects the nodal forces from a range of nodes. The first three of the nodes
is the basis of a plane of which a normal axis is calculated. The force from each node is calculated in this
direction, summarised and then plotted. A minimum of three nodes must be specified. This tracker is suitable for measuring the load through a cross section
of a member or a beam. |
Syntax
|
nr nodes = [node1,node2,node3,nodeN] direction = dir filename = fname
|
Options |
nr |
The tracker number. Must be a unique number in the
model, i.e. another sectionforcetracker cannot have the same number.
|
node1,2,.. |
The number of the first node etc. The first three nodes are mandatory. The rest are optional.
|
dir |
The direction of the forces to be collected. Can only be equal to "negative". When set, all the
forces acting in the opposite direction to the section normal will be summed. If this parameter is not specified
at all, the forces acting in the same direction as the section normal will be summed (default).
|
filename |
The filename of the result file of which the tracker should print the results. Must be unique for
each tracker.
|
|
Example
|
1 nodes = [23,24,12,34,15] filename = sectionforce_1.trk
|
See also
|
Nodeforce, Trackwriter, Trackers
|
Command |
Energy |
Block |
Trackers |
Description |
This tracker reads the energy from the model and plots it. There are
several different energy types that can be plotted, but only one per tracker |
Syntax
|
nr TYPE = ttype FILENAME = fname TARGET = [ttime,timetol,tvalue,valuetol]
|
Options |
nr |
The tracker number. Must be a unique number in the
model, i.e. another nodetracker cannot have the same number.
|
ttype |
The type of energy to plot. Can be one of
- contact - for contact energy.
- external - for external applied energy.
- internal - for internal absorbed energy.
- hourglass - for hourglass energy used to stabilize some elements.
|
filename |
The name of the file of which the energytracker should write. Must be a unique name for each
energytracker.
|
ttime |
The time where the target is to be checked.
|
ttol |
The tolerance for the target time
|
tvalue |
The target value.
|
valuetol |
The tolerance for the target value
|
|
Example
|
1 type = external filename = energy_external.trk
|
See also
|
Trackwriter, Sectionforce, Trackers
|
Command |
NodeDistance |
Block |
Trackers |
Description |
This tracker calculates the distance between two nodes and plots it
as a function of time into a selected file. The distance is the shortest space distance. |
Syntax
|
nr node = [node1,node2] FILENAME = fname TARGET = [ttime,timetol,tvalue,valuetol]
|
Options |
nr |
The tracker number. Must be a unique number in the
model, i.e. another NodeDistance tracker cannot have the same number.
|
node1,node2 |
The number of the nodes to track distance between.
|
filename |
The name of the file of which the tracker should write. Must be a unique name for each
tracker.
|
ttime |
The time where the target is to be checked.
|
ttol |
The tolerance for the target time
|
tvalue |
The target value.
|
valuetol |
The tolerance for the target value
|
|
Example
|
1 node = [23,15] filename = nodedist.trk
|
See also
|
Trackwriter, Sectionforce, Trackers
|
Command |
RodForce |
Block |
Trackers |
Description |
This tracker reads the local force from a given Rod_2 element. The force
is then plotted into a file as a function of time. Note that the force is always local and
not plotted in any global direction. |
Syntax
|
nr element = [telem] FILENAME = fname TARGET = [ttime,timetol,tvalue,valuetol]
|
Options |
nr |
The tracker number. Must be a unique number in the
model, i.e. another RodForce tracker cannot have the same number.
|
telem |
The number of the Rod_2 element to track force from.
|
filename |
The name of the file of which the tracker should write. Must be a unique name for each
tracker.
|
ttime |
The time where the target is to be checked.
|
ttol |
The tolerance for the target time
|
tvalue |
The target value.
|
valuetol |
The tolerance for the target value
|
|
Example
|
1 element = [23] filename = rodforce.trk
|
See also
|
Trackwriter, Sectionforce, Trackers
|
Command |
BeamSpring |
Block |
Trackers |
Description |
This tracker reads the local force from a given Beam_Spring_2 element. The force or moment
is then plotted into a file as a function of time. Note that the force or moment is always local and
not plotted in any global direction. |
Syntax
|
nr element = [telem] FILENAME = fname COMPONENT = comp TARGET = [ttime,timetol,tvalue,valuetol]
|
Options |
nr |
The tracker number. Must be a unique number in the
model, i.e. another BeamSpring tracker cannot have the same number.
|
telem |
The number of the Beam_Spring_2 element to track force or moment from.
|
filename |
The name of the file of which the tracker should write. Must be a unique name for each
tracker.
|
comp |
Sets which component to track. Can be one of: FX, FY, FZ, MX, MY, MZ.
If nothing is set here, the default is to track the FX component.
|
ttime |
The time where the target is to be checked.
|
ttol |
The tolerance for the target time
|
tvalue |
The target value.
|
valuetol |
The tolerance for the target value
|
|
Example
|
1 element = [23] filename = beamspring_mz.trk component = mz
|
See also
|
Trackwriter, Sectionforce, Trackers, Beam_Spring_2
|
Command |
Controls |
Block |
Controls |
Description |
The control block is initiated with the word control on a single
line. There can only be one control block in any give indata file. All
commands designed to control the solution process is defined here. One
command with it's associated parameters is defined on each line. |
Syntax
|
Controls
|
Options |
|
Example
|
Controls
|
See also
|
Run, Print
|
Command |
Run |
Block |
Controls |
Description |
This command controls the solution process. The starting time and the
end time are mandatory while control of the step size is optional. if this
is left blank, impact will choose the most optimal step size for each step
during the solution process. |
Syntax
|
Run from svalue to evalue step stpvalue |
Options |
svalue |
Start time for the solution |
evalue |
End time for the solution. |
stpvalue |
Stepsize for the solution. Specifying this value disables autostep.
The value can be a single number but could also vary with time.
It should then be specified within brackets with time, timestep
specified in pairs: [t1,ts1,t2,ts2....tn,tsn]
|
|
Example
|
Run from 0.0 to 1.2
Run from 0.0 to 1.2 step 0.0001
Run from 0.0 to 2.0 step [0,off,1.8,1e-5,2.0,1e-5,2.01,off,10,off]
|
See also
|
Controls, Print |
Command |
Print |
Block |
Controls |
Description |
This command controls the print process during the solution.
The command can also be repeated with the tracker word if the printing interval
is to be set specifically for the trackers. Impact will print the results
with the interval specified. Depending on how the element perform it's internal
calculations, the output may be local or global stresses and strains.
Displacements of nodes are also printed so that mesh deformation can be followed.
If no specific interval will be set for the trackers, they will print at the
same time as the general printing occurs. |
Syntax
|
print tracker every value step |
Options |
value |
Step time for printing. |
|
Example
|
Print every 0.01 step |
See also
|
Controls, Run
|
Command |
For |
Block |
Controls |
Description |
This command selects which Writer and Trackwriter to use. This selection determines
the output format for the result files and thereby the selection of postprocessor. The default is that
both the resultfiles and tracker files are printed in GID format. This command is entirely optional and is
often left out. |
Syntax
|
For writertype use selected_type |
Options |
writertype |
Choice of writer type to specify. Can be either Writer or TrackWriter. |
selected_type |
The selected type. For writers this can currently only be GIDWriter.
Future extensions include Dynawriter and Radiosswriter
For Trackwriters this can currently only be GIDTrackWriter.
Future extensions include DynaTrackwriter and RadiossTrackwriter
|
|
Example
|
For Writer use GIDWriter |
See also
|
Trackers, Elements
|
Other Indata and Outdata Formats
Impact is designed to handle other indata and outdata formats. At the
time of writing, there are no additional formats supported but the process
of extending Impact is documented in the programmers manual for those who
would like to.