Hello, is it planned to implement in PrePoMax the initial condition feature of Calculix per *7.75 INITIAL CONDITIONS of the User manual http://www.dhondt.de/ccx_2.19.pdf#page481 for mechanical analysis (initial displacement, plastic strain, stress) ?
Thanks
In the long run, yes but this is the first request of this type so this was not yet planned in the near future. Do you have a specific scenario in mind that you would need?
I have in mind residual stress / strain / displacement due to prior processing of a structural part. Such prior processing can be for example welding, brazing or plastic forming.
Is there another or better way to do this in your opinion than with the *INITIAL CONDITION feature?
Hello, I just want to share that I figured out that how to do it by properly defining a multi-step non-linear analysis. Initial condition feature seems to be not mandatory for what I intended to do as described above.
Cheers
That is great. The difference between multi-step analysis and using initial conditions is that using multi-step analysis requires all the steps to be computed at each analysis run. If the first couple of steps are always the same the restart option would come in handy (I think) or initial conditions could be used.
Yeah this is very interesting to me because usually I want to know if the structure, after it has reached equilibrium via known boundary conditions will react differently to new conditions. For example in a microscope or a telescope where they have a temperature dependent displacement, what effect would a heat source have on the displacement of one of the optics? For example, a transformer or power converter is located near the body of the telescope or a fan is blowing towards the bottom of a microscope. Normally we know the steady state displacement, but then we want to know if moving that heat source elsewhere or adding a new one will improve focus or alignment.
It would be great if one could run an analysis, then save the results and use them as the initial conditions to the next step without having to run the first step again.
I believe *RESTART functionality of Calculix will do the job as suggested previously. You need to use the Keyword Editor in PrePoMax to use this functionality.
I also think that for this kind of application *Restart functionality is more appropriate. Initial conditions are usually only meant for one field variable, like temperature, displacements, and stresses.
i follow up again about this feature, it could be useful when initial condition type stress based on element set is available in menus. Modeling of residual stress for steel section due to fabrication by hot rolled or welding process become more convenient, alternate method of bolt pretension also.
Definitely. One of the big limitations of CalculiX is that there’s no equivalent of import functionality available in Abaqus. You can export and reuse a deformed mesh but there’s no easy way to apply a stress/plastic strain field. It would have to be done manually. That’s where a preprocessor could help a lot.
indeed, even possible externally by scripting to read element set recorded to add any necessary definition. Also, these file can be saved and read back by *Include keyword in editor (PrePoMax) but it’s not convenient workflow.
Below example of initial stress for bolt pretension as alternate methods, i can imagine it will be quite fast in modeling and running. Probably, this usefulness applies in definition of residual stress in steel section also.
