Thanks for your helpful reply
1. I do have a question that If I use the 5s instead of 20s, even though everything will go 5 times faster, but what about the results, does it still have the high fidelity? Since the real case of the running time of the experiment is 25s. That is what I am concerning, you could make it less time with enough data points, but the thing is that 5s with 200Hz(suppose it is the highest) and 200*20*5=20000(data points), compared with the 20s with 200Hz(suppose it is the highest) and 200*20*20=80000(data points). Does this two cases give the same results? since it is nonlinear case, I think if the frequency sweep time is not slow or long enough, the nonlinear vibratory effect is very difficult to be noticed or attained. Do you have some suggestion?
2. If I have 2 cases: Case 1: Link the transient structural with the Modal Analysis and running them by mode superposition which is fairly linear. Case 2: Use just the single transient structural but turn off the large deflection and the nonlinear effects. What is the difference between case 1 and case 2?