||____ User's Guide ______________|
The usage of LFE MMT is as simple as possible: executable input-file
The input-file is a text file. It should look like
part-A.nas and part-B.nas are NASTRAN files, containing triangles
to describe the watertight surface of part-A and part-B . RESOLUTION is the size of the geometry details.
The LFE-MMT-output is a NASTRAN file MMT.nas . It contains tetras to represent part-A and
part-B and the fluid outside. MMT.nas also contains triangles to represent the surface
of part A and part B and the common boundary, if there is any. If part-A and part-B intersect,
Boolean subtract is performed, the latter part wins.
____ Further LFE MMT input: __ IO ____________
is a comment. Blank lines are allowed.
Your input parts may be ABAQUS formatted.
You give a name to the NASTRAN formatted output.
You give a name to the ABAQUS formatted output.
You give a name to the ABAQUS formatted output. The Tetras are quadratic i.e. each edge carries a midpoint.
Your ABAQUS formatted output consist of 4 files.
ABAQUS**2 may be used as well.
Your input consist of at least 38 parts. The largest set of face-connected Tetras of parts 1 to 14 is stored as the first file.
And so on.
____ Further LFE MMT input ______________
Sharp edge definition, default = 20 degree.
Free menory to run LFE-MMT is calculated from system information. This value can be changed.
CAUTION: Do not choose a value larger than the available memory.
0 iterations: octree-refine the initial tetra
4 iterations: octree-refine tetras, which hit the all-part-bounding-box
40 iterations: refine edges > RESOLUTION, which cause trouble in the Marching Tetra step.
Stop before 40 iterations if there are no edges > RESOLUTION to be refined.
1 catch sharp edges
1 Marching Tetra step
Default: 0 4 40 1 1
terminates mesh refinement globally: edges < 20.0 are not refined
terminates mesh refinement locally: edges < 2.0 of parts 16 .. 29 are not refined
1 improve or do not improve (= 0)
3 repeat (edge collapse, face collapse, edge swap) 3 times
7 each edge collapse, face collapse, edge swap is repeated 7 times
Default: 1 3 7
Barycentric limits. Default = 0.01
____ Support to run LFE MMT ______________
Read the mesh via NASTRAN or ABAQUS
Automatic free edge repair closes holes given by closed polygons of free edges.
Sometimes a twin pair of them should not be closed but instead of this the tube in between should be meshed.
75680 76092 are nodes of these twin circles to start the tube mesh.
split – separate surface data
____ DPT Bike ______________
Download the digital prototype (DPT). 1 file of stl data.
Merge nodes (merge radius 0.0) and store the DPT as NASTRAN or ABAQUS data.
Separate the surface data i.e. create parts via LFE SPLIT.
Since this stl-bike originally was not intended to be FE-analysed we have to repair 5 parts and create 2 new ones: Tire and wheel, front and rear and pedal wheel have free twin circles.
These twin circles are repaired using LFE REPAIR-CYLINDER. The front brake has to be fixed with an axis of rotation to the frame of the bike. For this purpose we create 2 cylinders. We remove the
spokes and replace them by rod elements in our computation model.
More than 100 parts are not watertight, but we can rely on the LFE MMT's automatic repair.
Now we change the order of the parts
part 1 to part 15 left hand side of the front brake
part 16 to part 28 right hand side of the front brake
part 29 to part 592 the other parts of the bike
part 593 and part 594 front wheel and tire
Now we are ready to run LFE MMT, this is the input file:
This is the screen output:
This is the LFE MMT tetra mesh: