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*GENSTRESS
Data format:
One line with one value IGR
Purpose :
To define the residual stresses to be distributed along a given group of elements
Restriction :
The group of element must be composed of rigid beam elements.
Details :
| Parameter | Description |
|---|---|
| IGR | Identification number of the group. This group must have been previously defined with keyword RISER, CASING or *GROUP. |
The residual stress file has the following format :
Lines starting with $ stand for comments
| $ ip | s | sigma(1) | sigma(2) | sigma(3) | epsil(1) | epsil(2) | epsil(3) | alpha(1) | alpha(2) | alpha(3) | dpe0 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| $ - | (m) | (Pa) | (Pa) | (Pa) | (-) | (-) | (-) | (Pa) | (Pa) | (Pa) | (-) |
| 1 | Sbeg | Value | Value | Value | Value | Value | Value | Value | Value | Value | Value |
| 1 | Send | Value | Value | Value | Value | Value | Value | Value | Value | Value | Value |
| 2 | Sbeg | Value | Value | Value | Value | Value | Value | Value | Value | Value | Value |
| 2 | Send | Value | Value | Value | Value | Value | Value | Value | Value | Value | Value |
| 3 | Sbeg | Value | Value | Value | Value | Value | Value | Value | Value | Value | Value |
| 3 | Send | Value | Value | Value | Value | Value | Value | Value | Value | Value | Value |
| 4 | Sbeg | Value | Value | Value | Value | Value | Value | Value | Value | Value | Value |
| 4 | Send | Value | Value | Value | Value | Value | Value | Value | Value | Value | Value |
| 5 | Sbeg | Value | Value | Value | Value | Value | Value | Value | Value | Value | Value |
| 5 | Send | Value | Value | Value | Value | Value | Value | Value | Value | Value | Value |
| 6 | Sbeg | Value | Value | Value | Value | Value | Value | Value | Value | Value | Value |
| 6 | Send | Value | Value | Value | Value | Value | Value | Value | Value | Value | Value |
| 7 | Sbeg | Value | Value | Value | Value | Value | Value | Value | Value | Value | Value |
| 7 | Send | Value | Value | Value | Value | Value | Value | Value | Value | Value | Value |
| 8 | Sbeg | Value | Value | Value | Value | Value | Value | Value | Value | Value | Value |
| 8 | Send | Value | Value | Value | Value | Value | Value | Value | Value | Value | Value |
Note
Between two abscissa of a riser Sbeg and Send, for each section point ip (Here eight section points are defined), the characteristics of the residual stresses (Sigma, Epsilon, Alpha and dpe0) must be defined.
By convention, the local reference frame is defined by the two bending axes (1, 2) and the third axis is the pipe axis.
Sigma : The stress tensor in the local frame writes
$$ \underline{\underline{\sigma}} = \begin{bmatrix} \sigma_{rr} & 0 & \sigma_1 \ 0 & \sigma_{\theta \theta} & \sigma_2 \ \sigma_1 & \sigma_2 & \sigma_3 \end{bmatrix} $$
where \(\sigma_{rr}\) and \(\sigma_{qq}\) are the radial and hoop stresses. \(\sigma_1\), \(\sigma_2\) and \(\sigma_3\) are linked to the beam kinematics.
An elastoplastic material behaviour with non-linear kinematic and isotropic hardening may be represented by a J2 (Mises) type. The yield criterion is then written as follows:
(1.)
$$ f(\underline{\underline{\sigma}}, \underline{\underline{\alpha}}, \kappa) = [(\underline{\underline{\sigma'}} - \underline{\underline{\alpha'}}): (\underline{\underline{\sigma}}' - \underline{\underline{\alpha'}})]^{\frac{1}{2}} - \sqrt{\frac{2}{3} \kappa(\overline{\varepsilon}^{\gamma})} $$ (1.)
\(\sigma\) (sigma) : Strain tensor,
\(\alpha\) (alpha) : back stress tensor,
Dpe0: The residual plastic deformation, e.g. the integral in time of the
plastic strain rate 
s: abscissa along the guide.
