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*DELTAX
Data format:
A single line with 4 parameters, as follows:
DELTX_S DELTR_S DELTX_D DELTR_D
Status:
Optional.
Purpose:
To set upper bounds to incremental displacements at nodes within the Newton- Raphson iterations. Setting bounds to the incremental displacements is intended to prevent numerical oscillations and help achieving convergence.
Details :
| Parameter | Description |
|---|---|
| DELTX_S | The maximum allowable displacement correction used within static and quasi static analyses for translational degrees of freedom between two steps of the Newton Raphson static iterations. If one or more component of the additional displacement vector exceed this value , the whole vector is multiplied by DELTX_S/(max.component). |
| DELTR_S | The maximum allowable displacement correction used within static and quasi static analyses for rotational degrees of freedom between two steps of the Newton Raphson static iterations. If one or more component of the additional displacement vector exceed this value , the whole vector is multiplied by DELTR_S/(max.component). |
| DELTX_D | The maximum allowable displacement correction used within static and quasi static analyses for translational degrees of freedom between two steps of the Newton Raphson dynamic iterations. If one or more component of the additional displacement vector exceed this value , the whole vector is multiplied by DELTX_D/(max.component). |
| DELTR_D | The maximum allowable displacement correction used within static and quasi static analyses for rotational degrees of freedom between two steps of the Newton Raphson dynamic iterations. If one or more component of the additional displacement vector exceed this value , the whole vector is multiplied by DELTR_D/(max.component). |
Note
- DELTX and DELTR must be >0 (even if DELTR is not used).
- This feature happens to be a really efficient tool for convergence acceleration. It prevents for excessive oscillations during the first iterations of the static calculation.
- Values of DELTX < or = to 1/10 of the maximum expected deflection of the initial model, seems to give good results.
- Default values of DELTX is 1/15 of the average element length
- Default values of DELTR is 0.07 (rad)
