Load step

[thirumalai]

Hi gentlemen,
I am condidering 3 load steps in my problem in each forces are acting in x,y & z axes respectively. I could see at the end the summed up result. But if I am deleting the Y force after solving the 2nd step & applying Z force in 3rd step, I could not see the effect of Y force at the end but at the end of 2nd step I could see the effect of X Y forces.
My question is How should it be taken for understanding? Practically If I am applying a Y force & then removing it at the end time before the 3rd one, will it not affect the material. If that force is creating any plastic strains at the time end(of 2nd step), then how that has to be taken into account?
Then for plotting plastic strains, if i use PLNSOL,EPPL,X,0,1 command its printing an error EPPL data unavailable. How to plot that?
Thanking u, Thiru.

 

[dollarbulldog]

Hi

I am not sure I understand your question exactly. As I understand you are trying to capture the stress envelop caused by different loading combination. Of course, for nonlinear problem, the final results may totally different for different set of loadings even though this is not so obvious for some problem. However, for J2 plasticy this may show up very different results i.e. X load is pressure, Y load is shear and again Z is pressure. Applying X,Z then Y at the last step obviously result the different responses of structure since plasticity will not occur before Y is applied. Is this your question?

Bests,

 

[bkal]

I am not sure which program are you using, and whether your subsequent steps are perturbations from the previous steps. What appears to be the case is that your second step is a perturbation from the first step, and that is why you see X+Y in your results. However, it seems that in defining the third step, you are actually starting from the zero state (i.e. no previous steps to be accounted for) - though it is not clear if you see X results in the third step (which I would doubt). On the other hand, if your third step is a pertubration of the second, than I would imagine you have applied your Y force in the opposite direction to that in the second step (to get rid of it) and than applied the Z force. In that case, I would imagine that the results shuld be adeqaute.

However, in dealing with nonlinear problems, you should bear in mind that the results are path dependant, and you need to apply your 'loading history' correctly.