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Start a simulation with a Pre-Stress from a previous one


Hello Everyone, 


I want to know if there is any way in NX to have a solution on which the load is applied on a model which is pre-stressed already (elements or nodes). 


Here is what I want to do:


1- I have two beams: both of them have a square section of 10x10 mm. The first beam is straight and is 5000 mm long. The second beam is also 5000mm long but is slightly curved.


2- I modelled both beams on NX


3- The beams are to be welded together. 


4- In practice, and with a jig, the curved beam will be clamped to the straight one, so I can weld them together. Meaning that with an external load (the clamps of the jig), the curved been will be elastically straightened for welding


5- I want to know the amount of stress in the weld, due to the curved beam wanting to spring back to its original position.


6- I know the load needed to straighten the curved beam and the amount of stress in it. 


7-I want to estimate the residual stress in the weld as follows: I model 2 straight beams that are perfectly watching each other, with one of them pre-stressed as the curved beam. 


8- I ''glue'' them in NX, with the weld modelled too. The spring back effect of one of the beams will induce stress in the weld. That's what I want to estimate and quantify. 


Is there any way in NX to do that?


Thank you  


Re: Start a simulation with a Pre-Stress from a previous one

Solution Partner Valued Contributor Solution Partner Valued Contributor
Solution Partner Valued Contributor

I think you may be approaching this differently to what is normally done. Funadametal FEA says that stress is proportional to deformation of elements, you would have to deform the elements in initial setup so Nastran can interpret this as strain and then stress. Not recommended.


I'd rather get two subcases going, first one that deforms the beam with enforced motion constraints and the second that will remove these EMCs and then fully fixes the beam along the weld seams. You can then read the forces the welds will counteract from the reaction forces.