Penalty conditions (BEAD_MIN_STRESS and BEAD_MAX_MEMBRANE)

Areas with either low stresses or low bending/membrane stress ratios shall be disregarded from the optimization.

Two penalty functions are available in SIMULIA Tosca Structure.bead:

  • BEAD_MIN_STRESS = <penalty_value>
  • BEAD_MAX_MEMBRANE = <penalty_value>

The functions make sure that the areas that either have very low stresses or a low bending/membrane stress ratio are disregarded by the optimization.

The BEAD_MIN_STRESS penalty value is the relative to the maximal Von Mises stress in the design area. If a element has a lower Von Mises stress than this value, the element is left out of the optimization.

The penalized elements are dark blue. Left is the BEAD_MIN_STRESS criteria used, and right is the BEAD_MAX_MEMBRANE used:

The BEAD_MAX_MEMBRANE is based on the ratio between the highest principal of the two tensors, Differential Stress Tensor and Membrane Stress Tensor, respectively. The Differential Stress Tensor is a measure for the bending of a plate whereas the Membrane Stress Tensor is a measure for inplane stress.

Left with no penalization criteria used and right with both:

Important:
  • The default settings are: BEAD_MIN_STRESS = 0.001, BEAD_MAX_MEMBRANE = 1.0. This means that if an element has less than 0.1% of the Von Mises stress or the membrane stress is higher than the bending stress, it will not be optimized.
  • Both penalty conditions can be shut off by setting the parameters to zero: BEAD_MIN_STRESS = 0.0, BEAD_MAX_MEMBRANE = 0.0.
  • After optimization or after a run of the type TEST2, the penalized areas can be visualized by generating a bead_ctrl-vtfx-file. The penalized areas for BEAD_MAX_MEMBRANE and BEAD_MIN_STRESS have the "Bead-values" -3 and -4, respectively in the resulting bead_ctrl-plot.