Error estimators and indicators

The currently supported values of eetype are in table 5.5.

• EET_SEI - Represents scalar error indicator. It indicates element error based on the value of some suitable scalar value (for example damage level, plastic strain level) obtained from the element integration points and corresponding material model.
• EET_ZZEE - The implementation of Zienkiewicz Zhu Error Estimator. It requires the special element algorithms, which may not be available for all element types.

  Please note, that in the actual version, the error on the element level is evaluated using default integration rule. For example, in case of ZZ error estimator, the error (L2 or energy norm) is evaluated from the difference of computed and ``recovered'' stresses, which are approximated using the same interpolation functions as displacements). Therefore, in many cases, the default integration rule order is not sufficient and higher integration must be used on elements (consult element library manual and related NIP parameter).

• EET_CZZSI - The implementation of combined criteria: Zienkiewicz Zhu Error Estimator for elastic regime and scalar error indicator in non-linear regime.

Table 5.5: Supported error estimators and indicators.

Error estimator/indicator	eetype
EET_SEI	0
EET_ZZEE	1
EET_CZZSI	2

The sets of parameters (errorestimatorparams field) used to configure each error estimator are different

• EET_SEI
  

  	[regionskipmap #(ia)]
  	vartype #(in)
  	minlim #(rn) maxlim #(rn)
  	mindens #(rn) maxdens #(rn) defdens #(rn)
  	[remeshingdensityratio #(rn)]

  
  
  • regionskipmap parameter allows to skip some regions. The error is not evaluated in these regions and default mesh density is used. The size of this array should be equal to number of regions and nonzero entry indicates region to skip.
  • vartype parameter determines the type of internal variable to be used as error indicator. Currently supported value is 1, representing damage based indicator.
  • If the indicator value is in range given by parameters (minlim, maxlim) then the proposed mesh density is linearly interpolated within range given by parameters (mindens, maxdens). If indicator value is less than value of minlim parameter then value of defdens parameter is used as required density, if it is larger than maxlim then maxdens is used as required density.
  • remeshingdensityratio parameter determines the allowed ratio between proposed density and actual density. The remeshing is forced, whenever the actual ratio is smaller than this value. Default value is equal to 0.80.
• EET_ZZEE
  

  	[regionskipmap #(ia)]
  	normtype #(in)
  	requirederror #(rn)
  	minelemsize #(rn)

  
  
  • regionskipmap parameter allows to skip some regions. The error is not evaluated in these regions and default mesh density is used. The size of this array should be equal to number of regions and nonzero entry indicates region to skip.
  • normtype Allows select the type of norm used in evaluation of error. Default value is to use L2 norm (equal to 0), value equal to 1 uses the energy norm.
  • requirederror parameter determines the required error to obtain (in percents/100).
  • minelemsize parameter allows to set minimum limit on element size.
• EET_CZZSI - combination of parameters for EET_SEI and EET_ZZEE; the in elastic regions are driven using EET_SEI, the elastic are driven by EET_ZZEE.