||____ User's Guide ______________|
The LINUX 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.
____ Input + Output via NASTRAN + ABAQUS ____________
// Input starts at column 1. This is a comment.
... is a comment. Blank lines are allowed.
... Your input parts are ABAQUS formatted.
... Your output parts are NASTRAN formatted. Triangles between different parts ( imprint )
are indicated by triangle properties n*1000 + nn ( part n and part nn , n < nn). Part m tetras are marked by property 10000 + m.
... Your output parts are ABAQUS formatted. Triangles between different parts ( imprint )
are indicated by triangle sets. Parts are marked by tetra sets.
... You give a name to the 1 file output.
... You give a name to the output directory. One file for each part.
... The output tetras are quadratic i.e. each edge carries a midpoint.
OUT-CONNECTED 1 14
OUT-CONNECTED 15 27
OUT-CONNECTED 28 36
OUT-CONNECTED 37 38
... Your input consist of at least 38 parts.
... Your ABAQUS formatted output consist of 4 files.
... The largest set of face-connected Tetras of parts n to nn is stored .
____ 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.
REFINE 0 4 40 1 1
... define the adaptive Multigrid hierarchy
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
RESOLUTION-PART 16 29 2.0
... terminates mesh refinement locally: edges < 2.0 of parts 16 .. 29 are not refined
IMPROVE 1 3 7
... define mesh Improvement
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
GOOD ELEMENTS 0.01
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 to the bicycle fork. 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:
594 NASTRAN lines for 594 parts, then
This is the screen output:
This is the LFE MMT tetra mesh:
The RESULUTION parameter for the front brake parts is 2.0, whereas the global RESOLUTION is 20.0.