Remarks for Sensitivity-Based Optimizations

Prescribed Accelerations for Sensitivity-Based Topology Optimization

Prescribed acceleration loading are often caused by gravity fields, centrifugal loading and rotary acceleration loads. This chapter defines which kind of acceleration types for the ANSYS® are feasible for sensitivity-based topology optimization.

The following commands are supported (In global Cartesian directions):

• ACEL specifies the linear acceleration of the structure.
• OMEGA specifies the rotational velocity of the structure.
• DOMEGA specifies the rotational acceleration of the structure.

The following commands are supported (About another reference coordinate system):

• CGLOC specifies the origin location of the acceleration coordinate system.
• CGOMEGA specifies the rotational velocity of the global origin.
• DCGOMG specifies the rotational acceleration of the global origin.

The following commands are supported (For element components):

• CMDOMEGA specifies the rotational acceleration of an element component about a user-defined rotational axis.
• CMOMEGA specifies the rotational velocity of an element component about a user-defined rotational axis.

Note:

• Applying lumped mass matrices can be enforced using LUMPM,OFF
• Applying consistent mass matrices can be enforced using LUMPM,ON

Multi CPU-Processors (MPI) in Combination with Sensitivity-Based Topology Optimization

Tosca Limitations:

Important: There are Ansys elements (e.g.: MPC184) that are not supported during Ansys MPI (or the so called Distributed ANSYS) run. Those elements are not allowed when using Tosca with Ansys MPI ! There are Ansys commands (e.g.: PSOLVE, ELFORM) that are not supported during Ansys MPI run. Thus Ansys fails to deliver all results requested by SIMULIA Tosca Structure sensitivity-based topology optimization when an Ansys analysis is executed in Distributed mode in combination with SIMULIA Tosca Structure sensitivity-based topology optimization. Ansys failing to deliver all results requested by SIMULIA Tosca Structure sensitivity-based topology optimization is solved by adding the following in the OPT_PARAM command in the ".par" file,

OPT_PARAM
   ....
   PROCESSORS = MULTI
   ....
END_ 

• Default is PROCESSORS = SINGLE.
• Design responses for reaction forces and internal forces cannot be applied when PROCESSORS = MULTI is activated.

Nonlinear Sensitivity-Based Optimizations (ANSYS® 14 Required)

Displacements, internal and reaction forces and stress values (i.e. all design responses except of compliance) extracted from nonlinear static analysis require information (pseudoloads) from ANSYS® perturbation steps for sensitivity-based optimization. These perturbation analyses are only available in ANSYS® 14 or newer and allow for the elements enlisted in the table below.

Important: Nonlinear optimizations using pseudo loads with ANSYS® versions < 14 are no longer supported! If you want to use this kind of optimizations please make sure you are using at least ANSYS® 14.

Linear perturbations in ANSYS® currently only allow the following element types:

Important: Other element types are not allowed in the model for nonlinear optimizations using pseudo loads in SIMULIA Tosca Structure.