Obsah
Nonlinear statics
Computational flowchart
Computational steps
1. Preparing the computation
The solution of this problem must be preceded by the first four steps of the linear elastostatic problem solution, which include the calculation of element stiffness matrices $\mathbf{K}$. The following conditions apply:
- Only isoparametric elements can be used.
- Analytical prescription of symmetry or periodicity cannot be used.
- Material properties are specified according to the Material properties page and Appendix Nonlinear material in the Reference Manual.
- Load cases are specified according to the Load case sequence page.
| Program | RMD2, RPD2, SRH2, FEFS (2D problem) / RMD3, RPD3, SRH3, FEFS (3D problem) |
|---|---|
| Inputs | name.i1, name.i2, name.i3, name.i4 |
| Logs | name.o1, name.o2, name.o3, name.o4 |
| Outputs | binary files |
| Details | Linear elastostatics, Computation overview / Reference Manual: Inputs |
2. Processing the loading history and the computational model
Input data are written to the text file name.iP.
The loading history is specified according to the Load case sequence page.
If the computation has already been performed (i.e., the nonlinear problem has been successfully solved), additional loading can be appended using the $\mathtt{KREST}=2$ key (see Load case sequence).
| Program | HPP2 (2D problem) / HPP3 (3D problem) |
|---|---|
| Inputs | name.iP, binary files from the previous steps |
| Log | name.oP |
| Outputs | binary files |
| Details | Computation overview, Load case sequence, Computational model specification / Reference Manual: Inputs |
3. Solving the system of equations
Input data are written to the text file name.iL. The recommended solution algorithm is the BFGS method ($\mathtt{KMET}=2$).
If the solution is terminated prematurely because the maximum number of iterations $\mathtt{NITER}$ has been exceeded, the program must be run again. The last iteration of the interrupted solution is automatically used as the initial approximation for the new run. Before restarting the program, it is possible (but not necessary) to change the input data in the name.iL file.
| Program | HPLS (2D / 3D problem) |
|---|---|
| Inputs | name.iL, binary files from the previous steps |
| Log | name.oL |
| Outputs | binary files (the solution is in the name.PLS file) |
| Details | Computation overview, Solver control parameters / Reference Manual: Inputs |
4. Calculating the strains and stresses
Input data are written to the text file name.i5, where the problem type key is $\mathtt{KPROB}=2$.
The parameter $\mathtt{ILC}$ must always be specified according to the actual number of solved load cases.
In the name.STR (name.STB) file, the effective plastic strain is denoted as SCALAR1 and the effective creep strain as SCALAR2.
| Program | STR2 (2D problem) / STR3 (3D problem) |
|---|---|
| Inputs | name.i5, binary files from the previous steps |
| Log | name.o5 |
| Outputs | name.STR (optional), name.STB (optional) |
| Details | Computation overview / Reference Manual: Inputs |