Notes on Beam Data
Notes on beam data
| (1) |
Hughes-Liu (integrated) beams locate their integration point(s) at mid-span,
and have a constant shear force and moment along their length.
The location and number of integration points through the thickness at mid span depends on the beam shape. See the *SECTION_BEAM keyword in the Ansys LS-DYNA manual for more information. |
| (2) |
Belytschko-Schwer (resultant) beams calculate the moment variation along
the beam, so may have different Myy and Mzz terms at ends one and two.
This presents a problem when only the basic force and moment vector is
written since only one Myy and one Mzz term are output.
These are in
fact the values at end 1.
So if you have a cantilever fixed at end
2, with a point load at end 1, you will not see any moment in it if you
only plot the basic Myy or Mzz data components (although the moment will
be there and it will behave correctly). Furthermore, the sign of the end 1 Myy and Mzz moments written to the extra data slots is opposite to the sign of the basic moment vector Myy and Mzz moments so care must be taken in interpreting the direction of moments when switching between basic and extra data component moments.
The best solution to this problem is to write the "extra" data since, as is shown in the table below, separate end 1 and end 2 moments are then written to file. |
| (3) |
At present there is no way to tell from the database whether the "extra"
data is for Belyschko-Schwer (resultant) or Hughes-Liu (integrated) beams.
So both sets of options may be extracted from the same dataset.
The table below shows how the different sets of data overlap in these data slots: it is your responsibility to interpret your data correctly. |
How resultant and integrated "extra" beam data components overlap in the Ansys LS-DYNA output file
Ansys LS-DYNA re-uses the same "extra" data slots, as stipulated by BEAMIP on *DATABASE_EXTENT_BINARY, to contain integrated and resultant beam data. There will be 5 * BEAMIP such slots, and they will contain the following data components:
|
Slot
|
Resultant
|
Integrated
|
|
|
1
|
Total axial strain
|
Int pt 1
|
XX axial stress
|
|
2
|
Plastic energy end 1
|
YZ shear stress
|
|
|
3
|
Plastic energy end 2
|
ZX shear stress
|
|
|
4
|
Y plastic rotation end 1
|
Plastic strain
|
|
|
5
|
Y plastic rotation end 2
|
Axial strain
|
|
|
6
|
Z plastic rotation end 1
|
Int pt 2
|
XX axial stress
|
|
7
|
Z plastic rotation end 2
|
YZ shear stress
|
|
|
8
|
Y bending moment end 1
|
ZX shear stress
|
|
|
9
|
Y bending moment end 2
|
Plastic strain
|
|
|
10
|
Z bending moment end 1
|
Axial strain
|
|
|
11
|
Z bending moment end 2
|
Int pt 3
|
XX axial stress
|
|
12
|
Axial energy
|
YZ shear stress
|
|
|
13
|
Internal energy
|
ZX shear stress
|
|
|
14
|
Plastic torsional rotation
|
Plastic strain
|
|
|
15
|
Spare
|
Axial strain
|
|
|
16
|
Slots #16 onwards not used
|
etc for further int pts
in blocks of 5 values |
|
If a model contains a mixture of integrated and resultant beams, and BEAMIP is >= 3 (that is 15 or more "extra" data values are written per beam), before v21 D3PLOT cannot know how to interpret the data, that is which column to use in the table above for any given beam. As a result it makes both sets of data component available for plotting, and it is up to you do choose the correct ones for the beams in your model. From v21 D3PLOT will use data in the ZTF file, if available, to identify beam element type (integrated or resultant) and will, by default, only plot integrated beam components on integrated beam elements and only plot resultant beam components on resultant beam elements. If the ZTF file is not available the behaviour will be as for earlier versions of D3PLOT. It is possible to switch the behaviour to the old behaviour, i.e. to ignore beam type when contouring, by using the Ignore Beam Type switch in Beam Symbols. Alternatively you can set the preference d3plot*ignore_beam_type:ON.
You need to exercise extreme care when interpreting results in this situation and it suggested either that you do not mix the two beam types in a model, or if this is necessary then you assign the PART numbers of each type of beam to different label ranges, or perhaps use some common identifier in the PART names, making it easy to control what is displayed by blanking.