Hi Hamish and all.

It is nice to find an other airplane homebuilder here in the forum with interest in FEA.

If we can make such scripts I can write a step by step tutorial how to calculate a framework fuselage
of a little sportplane.

About Z88 and Z88 Aurora: Z88 works with .dxf data, .txt scripts and files from other FEA-Software.
Z88 Aurora handle also .step and .stl like other FEA software will do.
Step parts made in MoI without extra lines and other objekts can be used in Z88 Aurora problemless.
There are a lot of different FEA-types that can be used for volume and surface calculations.

Two types are made for 2D and 3D framework. Type 9 and Type 4.
Normaly we need Autocad .dxf files to prepair a structure for Z88.
It is a complycated way with a lot of layer that is discripted in a extra Z88 tutrial.
It is easy to produce a lot of error and spend a very long time to get the propper file.

It is more easy to filter the needed information from a .dxf file and a special architektural software in a .txt file
and save that in Z88. But not for everybody and it is much to expencive.

My idea was to draw the framestructure in MoI, sample the information in one or more .txt files and build the
input file z88i1.txt from it.

The attachment show a typical structure like a part of a crane ore a tailbeam of a helicopter.
It was made first from lines and than marked with points where the knots of the structure are.

A script like "Save Points" coud give the information of the point-koordinates together with an index of the points.
The ideal form is:
Point-number Dimension of the frame X Y Z

1 3 0 0 0
2 3 520 600 0
and so on.

The next script gives an index of the lines and the startpoint and the endpoint of the lines.
Nice to have is an option to set the number of the "Type" into the text.
For example:
Number of line Type of line
Number of startpoint Number of endpoint

1 4
1 2
2 4
3 5
3 4
2 3
...........

The third script gives the same index for the lines and the true length of each line.
This we need for later calculation of the rigth tube diameter and wall thicknes.

1 453
2 621
3 516
..............

Next time I prepair a z88i1.txt file to show the complete input file.

I hope it is not to much complicated.

Hans

Hi Hans,

Great! I look forward to learning more and taking a closer look when you send the next file.

I get the general gist, and, unless I completely misunderstand something fundamental in MoI's script-ability, the task doesn't appear impossible.

As I mentioned earlier, I'm a novice programmer, so any advice from the other script guru's about best approach to this problem would be much appreciated. And if anyone else wants to jump on this - please go ahead - I'm sure to be left in the dust. :)
I'd equally be agreeable to collaborating on this via github or any other code-collaboration site.

To get the ball rolling, I envisage doing something along the lines of:

for each line object in the geometry database, do:
get length;
get xyz of start
get xyz of end
Sort data? By what criteria??
Export to text file.

I guess at a later stage it would be advantageous to be able to deconstruct a solid into a mesh and then export to the txt file, in much the same way as the STL and other polygonal export engines already function? Could Max's scripts be utilised perhaps - Max?

Cheers,
Hamish

Hi Hamish,


> for each line object in the geometry database, do:

There isn't any convenient way set up for a script to know if a curve is a line or a general bendy curve. But you can get a list of all curves in the geometry database by doing:
var curves = moi.geometryDatabase.getObjects().getCurves();


> get length;

The length of a curve can be retrieved using curve.getLength();


> get xyz of start

The start point can be retrieved using var pt = curve.getStartPt();


> get xyz of end

var pt = curve.getEndPt();


> Sort data? By what criteria??
> Export to text file.

A script can write to a text file using moi.filesystem.openFileStream(), check out the updated version of SavePointFile for an example: http://kyticka.webzdarma.cz/3d/moi/#SavePointFile


Currently it can be pretty difficult to write these kinds of scripts, it has not been a priority area for MoI as of yet and so there aren't things like tutorials and documentation and things like that. At some point in the future that will probably change but for now it can be pretty difficult to make stuff like what you are describing.

- Michael

Hi Hans

Try the attached script.

Usage:
Select lines
Run script
Paste data from clipboard to a text (or excel) file

data structure:
points coordinates
[point id] [dimension] [x] [y] [z]

endpoints
[line id] [start point id] [end point id]

length
[line id] [length]

Nice one Max! :)

Hi at all.

Thank you all for your fast answers. Believe me, I need much more time to understand what you have done for me than you needed to see what I want. :)
On Friday I have more time to answer you all. Please give me a little time for translating.

Thanks a lot
Hans

Hi at all.

Found a little bit time this morning.
My students are busy (I work as trainer for Solidworks) and I am not at home where we have some visitors over the Eastertime.

Here is an overlook about the workflow with MoI and Z88.

1. Drawing the framestructure in MoI (closer description will follow)
2. Editing of the z88i1.txt file (wirh the help of Max´s script; example next time) and save it in Z88
- we can see now the structure in Z88 with the labeling of the knots and the struts -
3. for different loads we make different files z88i2.txt (needs also a description)
4. we calculate every load in its own process
5. from Z88 we will get every time a file named z88o3.txt (here we have the tension and compression loads for the struts between the knots)
6. we take an excel sheet and put the inhold of the z88o3.txt in a column. After all calculations we have horizontaly all loadcases and verticaly
all struts. With an excel funtion we filter horizontaly all worst loads of tension and compression from our struts (max/min funktion)
7. As essence from all calculations we make a second excel sheet.
-Number of strut- startpoint (knot)- endpoint (knot)- true length- tension load- compression load- wall thickness- weight of strut
8. Now we calculate the outer diameter of our tubes (for this I have a little software in "dos" I would like to spend).
If the result shows Ø 14,58 we take Ø15 from our hardware dealer for example
9. Now we can draw the real structure

Every step will have later it´s own little tutorial with pictures.

In the first moment it seems a little bit complicated. But sometimes we have more then 200 struts an maybe 80 ore more knots in a 3D structure and
I had sometimes more then 30 loadcases. To calculate this needs many weeks. (If it is possible).

At next I try to test the script from Max.

Have a good time

Hans

maybe a missunderstood-

>some weeks of calculation>
with a handcalculator and a pencil

Hans

Hallo Hans and Max,

I look forward to taking a closer look when I'm home next week.

Cheers,
Hamish

Hi Max, Michael, Hamish an all

Max, your script is wonderfull!!

We need only a little bit finetuning to make it perfect.

Michael, thank you for substituting.

Hamish, thank you too.

Now to the script:

Z88 calculate 2D structures and 3D structures.
The different is only a "2" instead of a "3" in the line of the point coordinates
and the Type of the line (strut) is "9" for 2D- and "4" for 3D structures.

The input files in z88 have no dimensions.
We can take it for yards or feet or inch or mm
The load may be Newton or pound or tons.

With mm and Newton like I prefer, decimals for length or load are not necessary.
If the projekt is a big one (the Eiffel Tower for example) the result could be more
exact with one or two decimals in the length of the struts because the dimensions in the background are bigger.

Now we come to the mistakes of my explainings!

Max, you write

== endpoints ==
number of strut startpoint endpoint
1 1 2
2 3 2
...............................................

We need:

number of strut type of strut

startpoint endpoint

1 4
1 2
2 4
3 2
3 4
3 4
4 4
3 1
............

Can we have a little command window with the script?

like this:
------------
2D 3D

decimals 0;1;2;3

OK
-------------------
If we choose [2D] we will have a 2 in the line of point coordinates and a 9 as type of the struts
and with [3D] a 3 and a 4

After OK we can paste it like bevor.

With every new projekt we have to write a headline and a feetline and into a few seconds the z88i1.txt file
is ready.

At the 16. of April I have a meeting with the people of the Bayreuth University at the Hannover Fair.
I know that they look for a software that fit to her Z88. Some people asked for a good and not so expencive cad-programm.
Your script helps me to construct my little sportsplane, helps a lot of engeneers to build everything from bridges to framestructures
for satelites and I hope it helps Michael to give some more licenses into the world.

Happy Eastertime

Hans

Hi Hans,

Could you post here an examples of those Z88i1.txt files? With headers, footers etc..
It will help me to create a proper structure exactly as you want.

Hi Max,

I will prepare it this afternoon.

Thanks
Hans

I downloaded Z88AuroraV2, for Windows7.
The pdf file "theoryguide" shows the "GENERAL STRUCTURE DATA Z88I1.TXT" starting on page 54, and much more... Z88I2.TXT, Z88I5.TXT...file checker Z88VRY.

The explanation for the KFlag for cylindrical coordinates versus Cartesian coordinates seemed contradictory?

There is also DXF CONVERTER Z88X which is supposed to convert dxf r12 files to the 3 .TXT files.
There is an STL CONVERTER, Z88GEOCON...
Perhaps a .js converter could be checked with the above two converters?

(I've never used Z88)

- Brian

How load a file inside Z88 ? :)
I suppose it works only with DXF format ?

PS You don't like this free one ? :)
http://geuz.org/gmsh/ reload IGES, Step from moi ;)
http://geuz.org/gmsh/screencasts/
+ http://www.calculix.de/

or even Salome + Netgen http://www.salome-platform.org/ + http://www.hpfem.jku.at/netgen/index.html

Hi Max and all.

Here is the example of z88i1.txt.
It is the input file of the "Kranträger".

Pilou: In the past I allways worked with the open source version Z88 10.
Please copy the file in the main folder.

To work with Z88 is not a simple process. Max´s script will make it much more easy.

Z88 I like because it calculate the forces between the knots. Most importend if we build a "new Eiffel Tower" is
to construct the struts resistant against the bending loads. (Euler cases)
Colourfull pictures of "von Mises tension" do not help. Under load a frame structure will be destroyed when the
struts bend out.

Please stay patient. We will see what a powerfull tool MoI is not only in design also in development and engeneering.

Happy and optimistic Eastertime

Hans

Thx: take your time we will be very patient! ;)

NOTE: I should have opened the Informationen file in a proper word processor. :-( It comes pre-parsed.

 

I did a Parse of the Kranträger file in an attempt to understand it, and reconcile it with theoryguidePDF.
A few differences and questions resulted.

// Header is the first group, and has seven entries. (Versus 5 ???)
// #Dimensions = 3
// #Knots (or #Nodes) = 26
// #Struts (or #Elements) = 72
// DegreesOfFreedom = 60 (3 times 26 = 78, not 60 ???) (Maybe because structure is open, not closed?)
// LawOfE-modulus (What is this?)
// Flag (KFLAG is 0 for cartesian coordinates)
// Flag (Why are there two flags?)

3 26 72 60 1 0 0
========================================

// The second group has entries for each of the 26 KnotNodes.
// Knot#, DegreesFreedomThisNnot, Xcoord, Ycoord, Zcoord.
1 3 20 20 0
2 3 0 0 0
3 3 10 10 25
4 3 0 20 0
5 3 20 0 0
6 3 30 10 25
7 3 40 20 0
8 3 40 0 0
9 3 50 10 25
10 3 60 20 0
11 3 60 0 0
12 3 70 10 25
13 3 80 20 0
14 3 80 0 0
15 3 90 10 25
16 3 100 20 0
17 3 100 0 0
18 3 110 10 25
19 3 120 20 0
20 3 120 0 0
21 3 130 10 25
22 3 140 20 0
23 3 140 0 0
24 3 150 10 25
25 3 160 20 0
26 3 160 0 0
========================================

// The third group is explained on page 55 of theoryguidePDF.
// not sure if this is the correct parse.
1 4
1 2

2 4
3 2

3 4
3 4

4 4
3 1
etcetera (Did not parse the rest of the file)

- Brian

Hi Hans

Check the new version.
At the moment it supports 3D knots only.

I have the same question about DegreesOfFreedom. Why 60?

If the first 3 nodes, and the last 3 nodes are fixed, or boundary condition, maybe they do not count?
3 X (26 - 6) = 60.
(There is so much I do not know about FEA :-)
There is supposed to be a book...

- Brian

Hi at all.

Sorry, my mistake.

26 x 3 = 78

I had a handbook with an example beside and wrote the wrong number.

bemfarmer:

Z88 take about 24 different type of elements. Some need special flags - some not.
For my structures I used only Type 4 and Type 9.
As a user I have no clue wy it has to be a 0. It´s inside the programm.

E-law - is the direkt translation of "E-Gesetz".
It is the same as E-Modulus.


Max: Thank you. I write a little bit later again.

Hans