Automatic Creation of Multiple Loads


Hi all,


Does NX have a framework in which a number of load subcases can be automatically created? For example, say I want to analyse the effect of a vehicle passing over a bridge. I would build a model of the bridge, and represent the vehicle by applying forces at each point a wheel touches the bridge deck. To analyse what the effect of the vehicle is over the entire bridge, I would incrementally shift these loads along the bridge, and end up with results that show the effect of the vehicle at a number of locations on the bridge. This becomes quite time-consuming when the model is quite large, and I might want to create over 100 subcases to get an accurate idea of the effect on the bridge. 


NX I-DEAS had a feature where you could load a "program file", which was essentially a text file that could be generated by an Excel macro, which auto-created a number of different load cases, thus representing the vehicle moving along a bridge in the example above. Does any version of NX have a functionality similar to this?


My current idea of doing something like this is building the mesh in NX, then writing this to a .dat Nastran file, and using a script to generate the loads that could then be inserted into the .dat file and input into NX again. This seems like quite a round-about way of doing things however and I'm hoping to know if there is any alternative.




Re: Automatic Creation of Multiple Loads

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You can certainly do something similar in Simcenter using NX Open. NX Open uses programming languages (Python, VB, VC#, Java, C++) rather than macros, however, looping and program flow are much easier in these languages than it was in I-deas program files.


Simcenter does offer a couple of alternative approaches as well:


1) You can RMB on the solution and create multiple subcases. Once your subcases are created, you can RMB on the solution again and open the Subcase Manager. Here you can quickly toggle load entities on and off in each subcase, or assign scale factors to load entities in each subcase. You can edit the table in the UI, in a spreadsheet, or import/export a CSV file:


2) You could use a pseudo time static solution (i.e. SOL 401). Here you would define time dependent loads inthe global case. Time would have no dynamic affect, but would be a driver for time based load scaling fields. Output at specific time points would be requested via time step increments or at subcase end times. For the latterm you could create multiple subcases in the same manner as above. Each subcase would have an end time defined (where output would occurr), but would not have any loads defined in them.