**process fatigue_E

Description

This post-processor is used to predict fatigue lifetime using a strain measure. This strain measure can be a plastic strain, or another one such as the total strain. The critical variable is the amplitude of the strain (plastic) for uni-axial loading with a generalization pertinent for multi-dimensional loading (see the post computation range). If the loading is well known, the user can give simply the output “maps” necessary to calculate this amplitude (mode n1 n2 in **output_number). In the other case, a period of loading must be input (mode n1-n2 in **output_number).

The strain amplitude is denoted DEQ. The post calculation will generate a single result record for the entire loading history. The number of cycles to failure is defined as follows:

\[N_f = {\left(\frac{\bf DEQ}{A}\right)}^{-\alpha}\]

Syntax

**process fatigue_E \(~\,\) *var name \(~\,\) [ *type scalar | tensor ] \(~\,\) [ *scale lin | log] \(~\,\) [ *range section ]

name is the name of the variable to use as input to the computation.

For multi-dimensional loading the amplitude calculation will be made using a range type post-computation. In order to be able to input options to the range processor, the user can give a section number for that user input after the *range keyword.

The computation requires input of the coefficients A and alpha in the material file.

Output is given as number of cycles to failure in the variable NF_E. If the user specifies a logarithmic scale using the *scale option, the output variable will be LNF_E.

Example

**process fatigue_E
  *var eto
  *scale log
% The following syntax must be used in the material file :
**process fatigue_E
   A         1.7
   alpha     2.