How can I add Non structural Mass to Solid elements?
There is an option for NSM for PShell elements. What would be the best option for PSolid elements to add non structural mass. Currently I'm using a CONM2 point mass that is distributed across a surface using 1D rigid elements. Is that the only/best way? It seems a little messy.
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Altair EmployeeThere are as well other option like NSMADD and so on.
Suggest to have a look at OptiStruct manual from which I just grabbed an extract
Hope this helps.
Regards
Michele
Hi Michele,
Thank you for your reply. I'm only trying to apply this NSM to a part of the model. The methods above seem to apply it to the whole model when applied to a subcase. Is this correct or can I define the PSolid ID in this line below
BEGIN BULK NSM,12,PSOLID,3,0.3 NSM,13,PSOLID,3,0.7
and it would only apply to that particular property?<br /><br />
Regards
Shoaib
Altair EmployeeShoaib,
yes, NSM can be used to select a subset by property
NSM
Bulk Data EntryDefines non-structural mass per unit Length, per unit Area, or per unit Volume for a list of elements or properties.
Format
| (1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) |
|---|---|---|---|---|---|---|---|---|---|
| NSM | SID | TYPE | ID | VALUE | ID | VALUE | ID | VALUE | |
| + | ID | VALUE | etc. | etc. | etc. | etc. | etc. | etc. |
Example 1
| (1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) |
|---|---|---|---|---|---|---|---|---|---|
| NSM | 4 | PSHELL | 155 | 0.06 |
Example 2
| (1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) |
|---|---|---|---|---|---|---|---|---|---|
| NSM | 6 | ELEMENT | 12 | 0.03 | 13 | 0.06 | 14 | 0.03 | |
| + | 18 | 0.02 | 36 | 0.03 |
Definitions
| Field | Contents | SI Unit Example |
|---|---|---|
| SID | Non-structural mass set identification number. No default (Integer > 0) | |
| TYPE | This can be one of the properties PSOLID, PSHELL, PCOMP, PBAR, PBARL, PBEAM, PBEAML, PROD, CONROD, PSHEAR, or PTUBE, in which case the list of IDs will refer to properties of the stated type, or it can be ELEMENT, in which case the list is of individual element IDs of elements that can have NSM. It can also be of type ELSET, in which case, it is an element SET ID. No default | |
| ID | Property ID, Element ID, or Element Set ID depending on the TYPE definition. No default (Integer > 0) | |
| VALUE | Non-structural mass per unit Length (1D elements), per unit Area (2D elements), or per unit Volume (3D elements). No default (Real) |
For me NSM looks promising as alternative to point masses. It can be defined for optistrup in hypermesh from Tools>Mass Trmimming panel. The single NSML can be applied to Load Step by selection NSM in subcase definition and works as expected. I have several NSMs in my model applied to sets of elements describing different types of weights.
however I have to change mass configuration between load cases.
In documentation I found that I should use NSMADD.
https://2021.help.altair.com/2021/hwdesktop/hm/topics/panels/help407.htm
I suppose definition from Load Collectors shall be used in some way. The problem is that I cannot find a path to efficiently apply created NSMADD to specific Load Cases. It does not appear in subcase definition NSM=.
How shall I define different mass configurations for sequence of load cases?
I cannot believe how stupid definition of NSMADD in Altair HW is. From GUI of HyperMesh NSMADD cannot be applied to Subcase Information directly, where it should be possible according to documentation. But it can be achieved from GUI by trick, by changing SID of NSMADD to one selected in Subcase Information NSM.
see comments: https://2021.help.altair.com/2021.2/hwsolvers/os/topics/solvers/os/nsmadd_bulk_r.htm
I believe this is an source of 1M bugs, as no reference is tracked properly in GUI.
I cannot believe how stupid definition of NSMADD in Altair HW is. From GUI of HyperMesh NSMADD cannot be applied to Subcase Information directly, where it should be possible according to documentation. But it can be achieved from GUI by trick, by changing SID of NSMADD to one selected in Subcase Information NSM.
see comments: https://2021.help.altair.com/2021.2/hwsolvers/os/topics/solvers/os/nsmadd_bulk_r.htm
I believe this is an source of 1M bugs, as no reference is tracked properly in GUI.
It seems that NSMADD is treated as a load collector instead of as a group (like NSM is).
If you want to target all of the subcases with a single NSMADD, you can do this by creating a Case Control Card and choosing your NSMADD under the NSM checkbox:
Choosing a specific NSM group in the subcase will override the global case control NSM. If you want to do this, you need a LOADADD card, in which you will group your subcase specific loads and subcase specific NSMADD. Then use this LOADADD in the load field of the subcase.
NSM
Subcase Information EntryThe NSM command can be used to select a non-structural mass set for mass generation.
Format
NSM = option
Example 1