Materials and Properties

Tosca Structure supports linear elastic material for static and modal analysis for all optimization types (topology, shape, bead, sizing) inside and outside the design domains. In addition, the following nonlinear material types are supported for shape, bead, and sizing optimizations inside and outside the design domain and for topology optimizations outside the design domain only: Mooney and Ogden.

This page discusses:

Material Definitions

The interface to ANSYS® recognizes and supports a wider range of material-related features, including:

  • All properties specified for a material in the original model are assigned (and modified, if necessary) to the materials created by Tosca Structure during topology optimization.
  • Anisotropic materials get scaled for all material-directions.
  • Temperature-dependent properties are supported for both MPxxx and TBxxx-types of commands.
  • The following TB command variants are supported by the interface for modification, that is, for all optimization types both outside and inside the design domain:

TB

TBOPT

Anisotropic Elastic Material

ANEL

Anisotropic Constants

ANISO

Bilinear Isotropic Hardening Constants

BISO

Bilinear Kinematic Hardening Constants

BKIN

Cast Iron Plasticity Material Constants

CAST

ISOTROPIC (*)

Drucker-Prager Constants

DP

Hyperelastic Material Models

HYPER

BOYCE, BLATZ, FOAM, GENT, MOONEY, NEO, OGDEN, POLY, YEOH

Kinematic Hardening Constants

KINH

PLASTIC (*)

MKIN

Multilinear Elastic Constants

MELAS

Multilinear Isotropic Hardening Constants

MISO

Nonlinear Isotropic Hardening Constants

NLISO

VOCE (*), POWER (*)

Plastic Strain

PLASTIC

MISO (*), KINH (*)

Uniaxial Behavior

UNIAXIAL

TENSION,

COMPRESSION

(*) TBOPT is optional

Shell Properties

Bead Optimization
Thickness and Offset information of shell properties are supported. Example:
SECTYPE,1,SHELL
SECDATA,0.006,1,,
SECCONTROL,,,,,,,
SECOFFSET,BOT

Remarks

Important:

  • The use of nonlinear Materials requires a Tosca Structure.nonlinear.r license.
  • Tosca Structure needs different properties for different element types. For example, it is not allowed that a solid element and a shell element share the same element property.
  • Geometrical nonlinear modeling might cause convergence issues in the FE-solver for the void elements (in topology optimization) because the void elements might have semidefinite or negative definite elemental matrices. Especially, for geometrical nonlinear modeling combined with nonlinear material convergence issues emerge in the FE-solver. No unique solution exists if convergence issues occur for the void elements. However, a potential candidate for a solution could be to use SOFT_DELETE (see Relation between Relative Density and Stiffness or OPT_PARAM) or increasing the relative minimum density (parameter DENSITY_LOWER in OPT_PARAM). Additional, the user should check if the most favorable settings for solving the nonlinear equilibrium are applied in the FE-solver.
  • With Tosca Structure 8.0 SECBLOCK-sections for shell elements are supported in both sizing and topology optimization.
  • Shell properties for elements used for sizing must be defined using the SECBLOCK option. Elements using only the RLBLOCK definition are not admitted for sizing optimization with Tosca Structure. This implies that only shell elements of type SHELL181 and SHELL281 are admitted for sizing optimization.