As a result of an optimization run, OptiStruct produces one or more new design files depending on the type of optimization performed. These files contain minimum information resulting from the optimization, and can be combined with the original model by reading the model back into HyperMesh and creating a new, combined model.
To avoid this operation, which can be time consuming and take up disk space, especially for large models, it is possible to combine these files with the original model within OptiStruct. File combination in OptiStruct is done by reading the original, complete model, and applying the changes using the "ASSIGN,UPDATE,update_filename" control card. The file uses the same format as the bulk deck, but it can contain only modification cards (GRID, MATx, Property, or STACK). All of the cards in this file must be identical to the cards in the original data, but with different values for all optimized quantities. If there is an ECHO request in the original deck, then the resulting printout reflects modified values.
As an example, The GRID card in the update_file must have the same ID as a card in the original input deck, and must match on the CD, PS, and SEID fields. New values of X, Y, and Z fields will be used in analysis.
| • | All integer and text fields in the update cards must match the original cards in the input deck. All real valued fields can have different values than those in the original deck. Most of the consistency conditions are verified during reading, but not all. For example, most text fields are not verified. With the exceptions noted below, all real valued data are taken from the update deck, and all remaining information will be retained as in the original deck. |
| • | Every card in the update deck must have its counterpart in the original deck, but not all cards from the original deck need to be in the update file. All cards in the update deck must be unique, unless SYSSETTINGS,UPDATE,permissive is used in control section. |
| • | SYSSETTINGS,UPDATE,unique disallows repeat cards in the update deck, but with this card, the update deck can contain all bulk cards, and all non-accepted cards will generate only a warning. The default mode is SYSSETTINGS,UPDATE,strict. |
| • | Only one ASSIGN,UPDATE is allowed in the input data, however the update file can contain INCLUDE cards, which allows for the combination of multiple files. |
| • | GRID: On grid card, new X, Y, and Z coordinates can be defined in the same coordinate system as the original card (CP field) or in the global base system (CP is blank). |
| • | PCOMP: The updated version of this card must have the same number of layers, and it has to use the same MID values, but it can result from shuffling optimization, that is the order of layers can change. |
| • | CQUAD/CTRIA: New values for T are allowed, however these cause an error if such an element is in the designable domain. This means that the result of topology optimization cannot be used in further optimization, only in ANALYSIS runs. |
| • | During the reading of an update deck, all blank fields will be accepted as zero value, not as a default value suggested by reference manual. For example, on the MAT1 card, it is normally accepted to leave one of the E, G, or NU fields blank and it will be computed from consistency rules - but during update, such fields will be treated as if explicit 0.0E0 were present in the data.
This is usually not a problem for data generated by OptiStruct from an optimization run, because such fields will be filled with actual default value. |
