Here are a few common tips and workarounds for MADYMO.
Tip 1 -
Element orientation visualisation
A plug-in for Altair HyperMesh can be obtained from
the MADYMO customer download area, which allows element
orientations to be visualised. This is particularly
useful when specifying orthotropic friction for FE
belts, as the direction of the friction coefficients
is determined by the element orientation. Orthotropic
friction is a MADYMO R6.2 feature.
Tip
2 - Using Multibyte Characters in Your Input Deck
If you wish to include multibyte characters in your
XML input deck {for example: ü, ä or ß},
remember to include the encoding attribute to the
XML declaration on the first line of the file.
<?xml version = "1.0" encoding= "ISO-8859-1" ?>
The XML parser on some platforms may have difficulties
in reading the multibyte characters, if the encoding
attribute is not included.
Tip
3 - Translation of R 6.01 airbag models to R 6.1
containing IMM2
IMM2 is often used for In Position airbag modelling
cases. The initial state of the airbag shape is often
scaled/shrunk instead of folded. By specifying two
lists of co-ordinates the airbag initial shape and
the reference (inflated) shape of the airbag are defined.
Shrunken elements
In versions prior to MADYMO R 6.1 elements in a shrunken
state had a damping characteristic (IMM_DAMP). In
6.1 functionality was added that enables, amongst
others, to specify stiffness (IMM_STIF_REDUC) for
shrunken elements. For backward-compatibility reasons
the translator defines a zero value for the stiffness
reduction value. The default value (0.01) will be
applied if an input deck is translated to R 6.1 format “by
hand”. The consequence of translating an input
deck manually might be that the airbag starts to
move due to the added IMM stiffness. This phenomenon
can be prevented by defining a zero or very low value
for the IMM_STIF_REDUC parameter. This will help
only for elements that are shrunken w.r.t. the reference
state.
Stretched elements
Stretched elements need to be handled differently.
The preferred method is to scale the initial shape
of the airbag such that no stretched elements exist
anymore. Another possibility is to define an IMM_STRAIN
value. By activating the element MAX_STRETCH_PRINT
in the CONTROL_IMM.METHOD2, the reprint file will
list those elements that are stretched the most.
In the next example the differences between manual
and automatic translating are given. It should be noted
that not only the reduction stiffness value, but also
the IMM damping method are different.
Damping method 0 (default) is the preferred method.
Good results have been obtained for this method by
defining an IMM_DAMP value of [0.1,..,0,2]. The translator
will, for backward compatibility reasons, define the
original damping method (damping method 2). For R6.2
IMM2 airbag models the preferred method is also: damping
method 0 with a damping value of ~ 0.1 to 0.2, a zero
or very low IMM reduction stiffness value and no stretched
elements.
Part of R 6.0.1 input deck
<PROPERTY.MEM3
ID="1"
NAME="fabric_pro"
THICK="3.500000E-04"
IMM_DAMP="1.000000E-04"
..
/>
Part of R 6.1 reprint file (translator)
PROPERTY ID : /1/1/1 ( /S1/Bag/fabric_pro )
TYPE : MEM3
THICKNESS : 3.5000E-04
IMM DAMPING : 1.0000E-04
.. ..
IMM STIFFNESS REDUCTION : 0.0
IMM DAMPING METHOD : 2
Part of R 6.1 reprint file (manual)
PROPERTY ID : /1/1/1 ( /S1/Bag/fabric_pro )
TYPE : MEM3
THICKNESS : 3.5000E-04
IMM DAMPING : 1.0000E-04
IMM STIFFNESS REDUCTION : 0.01
IMM DAMPING METHOD : 0
Tip
4 - Buffer flushing on Windows Platforms
In MADYMO R6.2 a bug in the write buffer flushing mechanism
was fixed on the Windows platform. Buffer flushing
enables the user to view the output files during
the simulation. This mechanism didn’t function
on Windows in MADYMO versions prior to R6.2. However,
the buffer flushing can slow down the simulation.
This depends on the type and size of simulation,
the amount of output requested, the output time step
and the hardware configuration.
Until this problem is fixed, it is advised only to
select output strictly needed, and to keep the output
time step as large as possible. Note that this is not
an issue on other platforms than Windows. This problem
has been fixed in 6.2 patch level 1, released on July
31, 2004.
Tip
5 - SGI parallel performance improvement
For SMP computations on SGI systems use the following
environment settings in order to get a better parallel
performance:
setenv _DSM_PPM 2
setenv _DSM_PLACEMENT ROUND_ROBIN
Tip
6 - MADYMO/Translator dat2miff
When a large MADYMO model in 5.4.1 format is translated
to .xml format with MADYMO R 6.1 using
madymo61 –dat2mif
file.dat
the –isize, -rsize and –csize options can
not be used for this translation. Instead, the user
must set the environment variables MD_CFEMST_SIZE (characters),
MD_IFEMST_SIZE (integers) and MD_RFEMST_SIZE (double
precisions) manually before translating.
In MADYMO R6.2 the problem has been solved.
Tip
7 - Running MADYMO R6.1 in the background
In MADYMO R6.1 the Unix option “-bg” does
not exist anymore. Hence Madymo R6.1 always runs in
the foreground. A user wanting to run in the background,
should issue the following command:
madymo61 file.xml > /dev/null &
An alias e.g. mad61 could be specified for this:
alias mad61 ‘madymo61 \!* > /dev/null &
Tip
8 - The “–stopit” option
The option “-stopit” is not supported anymore
on any platform in MADYMO R6.1.
Use the following command to end a running simulation
under Unix:
kill -HUP <processID>
Under Windows there is no proper alternative for the
old “–stopit” option.
Tip
9 - Restart
1. Restarted simulations can write NaN’s to the
KIN3 (.kn3) files in MADYMO 6.0.1 and MADYMO 6.1 due
to a missing initialisation in the code. The solution
is to use MADYMO 6.1 patch level 2 or higher in which
this problem has been solved.
2. When restarting MADYMO 6.1 using the command
madymo61 -rst simul.rst simul_restart.xml
the XML translator generates the error message:
Unable to translate the file /xxx/xxx/xxx/simul_restart.xml.
DOCTYPE root element is unknown
A workaround is to use the –nopretrans option:
madymo61 -rst simul.rst -nopretrans simul_restart.xml
This problem is solved in MADYMO 6.2.
3. When restarting in MADYMO 6.1 with simulation filenames
longer than 40 characters (i.e. more than 40 characters
in front of .xml), memory is overwritten. This can
result in an abort, so we recommend that filenames
not exceed 40 characters. This problem is solved in
MADYMO 6.2.
