Erosion is a numerical technique used to remove elements from the simulation to combat element distortion in Lagrange meshes. The following erosion criteria are available:
Erode on Geometric Strain
Elements are removed from the simulation if the geometric strain of the element exceeds that which is specified in the Erosion Strain. There is the option to use Incremental or Instantaneous Geometric Strain as the erosion criteria. See the note below for further information.
Erode on Plastic Strain
Elements are removed from the simulation if the plastic strain of the element exceeds that which is specified in the Erosion Strain.
Note: The limit set in Erode on Plastic Strain in Engineering Data is compared to strain variable EFFPL_NBS, which is available in Autodyn but not exposed in Explicit Dynamics in Mechanical. Explicit Dynamics can plot other strain variables but they are not used to check if erosion is occuring. This is valid for tetrahedral elements where the Tet Integration is set to Nodal Strain in Analysis Settings.
Erode on Failure
Elements are removed from the simulation if they have failed due to meeting any failure criterion specified in the material model.
Erode on Timestep
Elements are eroded if the CFL timestep for the element is smaller than that which is specified in the Minimum Timestep.
Note: When using Erosion on Geometric Strain, either the Incremental or Instantaneous Geometric Strain can be used. The EFF_STN variable will plot the Instantaneous Strain in an element if the material in the element has Erode on Instantaneous Geometric Strain. It will plot the Incremental Strain in an element if the material in the element has Erode on Incremental Geometric Strain. The Instantaneous Geometric Strain for an element is calculated every cycle from the global strain components using the following formula:
 | (11–19) |
The Incremental Geometric Strain for an element is incremented every cycle by an effective strain increment, which is calculated from the global strain increments using the following formula:
 | (11–20) |