would it be possible to implement a load factor contour plot into the postprocessing of PrepoMax?
load factor = Mises Stress (or other stresses) / characteristic design value (e.g. yield strength)
The scale would range from 0 to 1 or more depending on how utilized the material is.
I think it would be nice to share such a plot with people who do not the max. allowable stress for a specific material or loading (one-time, cycling, …)
If such a calculation would be set up in a more general way one could maybe use it to generate other contour plots also… Design values (such as yield strength, tensile strength, fatigue limit…) could be filled into the material library and used for automatic contour plot generation.
Right now I did this a few times in a real cumbersome way by converting .frd result file to vtk/vtu (Paraview format). Within Paraview I run a small script to generate such a contour plot.
For postprocessing, the free but closed source FEA program Nufuss (with ABAQUS input file syntax) is a good inspiration. It implements the calculations according to FKM code, see Steibler Lebensdauerberechnungen mit FEM | SpringerLink
Safety factor (that’s how it’s usually called) contour plots are typically available in CAD-embedded FEA modules but not in pure FEA postprocessors. For example, Abaqus doesn’t have such a predefined output variable. In these cases, it’s necessary to create user-defined field output based on equations and that was requested for PrePoMax some time ago. The problem with safety factor plots is that they can be based on different characteristic quantities so it might be better to just implement custom equation-based field output.
ParaView has a Calculator filter that can easily divide the output by a given value. But I assume that you needed a script to make it more automated or to account for the presence of different materials in the model, right ?
I also think that a more general way is the way to go. So in the next versions, support for equation based user-defined fields will be added. Whit this, the user could easily create a safety factor/load factor plot. The only problem with this procedure is that it operates on the whole mesh = all materials. So some additional functionality is needed in case there multiple materials are used.
So support for equations inside the increment is needed, like: SMAX - SMIN. The variables used would be field components. And this equation would be evaluated for each increment of each step of the results.
The next question is, is there a need for combining results from multiple increments. In this case, the variables would probably be entire fields with all components and they would have to be used together with increment and step id. Something like U.1.1 + U.1.3.
Personally, I would vote for an approach similar to the one used in Abaqus - an option to create field output:
From fields - creating custom output variables using equations based on existing outputs (e.g. stress divided by yield strength) - something like a Calculator filter in ParaView, such custom variables would be available at all increments
From frames - operations on results from multiple increments - sum, finding min, finding max - resulting in a single frame
The first option is more important for me, especially since the second one has limited usage in the case of CalculiX because typical load case functionality is not supported by this solver (although results from multistep analyses representing load cases could also be evaluated this way).
Maybe highly requested transformation to user-defined coordinate systems could be implemented on this occasion as well.
I hope this feature gets implemented. I would like to be able to add/import temperature based yield/uts etc. data and obtain ratio plots to desired stress results (Mises, principals etc.).
