Analysis Files for Optimization (FEM_INPUT)

Optimization with SIMULIA Tosca Structure always refers to one or more analysis files which provide the design space and necessary values for the optimization as results of a finite element analysis run.

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FEM_INPUT

A single finite element file or several finite element files are referenced in the item FILE in the command FEM_INPUT or the folder MODEL_LINK in Tosca ANSA® environment. However, all finite element files should have the same number of elements, nodes, material properties, element groups, nodes groups etc. The only difference allowed between the different input finite element files is that the analysis types can vary. The analysis type can either be linear static, non-linear static, modal eigenfrequency or frequency response analysis.

The FEM_INPUT command is applied for reading the finite element files in the following way:

FEM_INPUT
 ID_NAME = id_read_files
 FILE = fe_file_name_1
 FILE = fe_file_name_2
 FILE = fe_file_name_3
 ...
END_

Working with Tosca ANSA® environment, all three files can be entered into the MODEL_LINK folder in a similar way.

The possibilities available to the user for loading the analysis model when creating the optimization model depend on the chosen solver (see Postprocessing of Optimization Results and Solver Specific Features) and the option set (OPTIONS). The model data is loaded using an internal interface. After reading the model, the following FE objects are available for further reference in the optimization task:

  • node groups
  • element groups
  • nodes
  • elements
  • coordinate systems
  • materials
  • properties
  • element types
  • boundary conditions (depending on the OPTIONS)
  • load cases

Analysis results used as terms for objective or constraint, so called design responses (DRESP), are built by referring the load case numbers for the desired responses.

The load cases in the first file (fe_file_name_1) are numbered using the original load case numbers used in the finite element file.

The load cases in the second file (fe_file_name_2) are numbered using the original load case numbers used in the finite element file plus 10.000.

The load cases in the third file (fe_file_name_3) are numbered using the original load case numbers used in the finite element file plus 20.000 and etc.

E.g. the load cases 1, 3 and 4 in the first finite element file have the numbers 1, 3 and 4 in the parameter file, the load cases 1, 3 and 4 in the second finite element file have the numbers 10001, 10003 and 10004 in the parameter file, the load cases 1, 3 and 4 in the third finite element file have the numbers 20001, 20003 and 20004 in the parameter file and etc.

In Solver Specific Features the different allowed analysis types for the specific solvers are described. Furthermore, About Load Case Specification (LC_SET) describes how the load case numbers for the different finite element solvers are applied in the design response definitions (DRESP). This is especially important for the finite element input decks using no numbers when defining load cases. For the finite element solvers using no numbers the general rule is that the load cases have the numbers according to the order within they are defined. Meaning that the load case number one will always have the load number of one for SIMULIA Tosca Structure etc.

Remarks

  1. A model link can only be made once for an optimization task, i.e. the command FEM_INPUT can only be used once in a parameter file.
  2. Several analysis files can be added, i.e. the item FILE can be repeated several times. The first file in the list of files will be handled as master file, which means that the configuration of the finite element model will be read from this file. The second and all later referenced files will be used to perform a finite element calculation. The model in these files has to be identical to the original FE model. The files will be modified during the optimization.