Nonlinear dynamics

Computational flowchart

Computational steps

1. Preparing the computation

The solution of this problem must be preceded by the calculation of element stiffness matrices $\mathbf{K}$ (i.e., the first three steps of the linear elastostatic problem solution). The following conditions apply:

Only isoparametric elements with linear shape functions (i.e., without midside nodes) 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 (2D problem) / RMD3, RPD3, SRH3 (3D problem)
Inputs	`name.i1`, `name.i2`, `name.i3`
Logs	`name.o1`, `name.o2`, `name.o3`
Outputs	binary files
Details	Linear elastostatics, Computation overview / Reference Manual: Inputs

2. Calculating the mass matrices

Input data are written to the text file name.iM. The program generates consistent (thus positive-definite) mass matrices $\mathbf{M}$ of elements.

Program	HMOT (2D / 3D problem)
Inputs	`name.iM`, binary files from the previous steps
Log	`name.oM`
Outputs	binary files
Details	Computation overview / Reference Manual: Inputs

3. Processing the loading history and the computational model

Input data are written to the text file name.iP. The loading history is defined 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

4. Solving the system of equations

Input data are written to the text file name.iN. The solution algorithm is the central difference method ($\mathtt{KMET}=1$). The last iteration of the completed solution is automatically used as the initial approximation for a new run of the program. Before restarting the program, it is possible (but not necessary) to change the input data in the name.iN file.

Program	HDYN (2D / 3D problem)
Inputs	`name.iN`, binary files from the previous steps
Log	`name.oN`
Outputs	binary files (the solution is in the `name.PLS` file)
Details	Computation overview, Solver control parameters / Reference Manual: Inputs

5. Calculating the strains and stresses

Input data are written to the text file name.i5, where the problem type key is $\mathtt{KPROB}=2$.

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