I would like to ask about the stability of the Newmark-Beta method used for the forced vibration analysis of laminated plate. In many books, stated that if the coefficients, alfa and beta are respectively taken as 1/2 and 1/4, the results are unconditionally stable which means the change of time step size does not effect the results. However, in my results, I have divided 1[s] into 40 and 100 time steps and it seems that the transverse mid-displacement time histories of the two cases do not match with each other.
Has anyone ever faced with a problem like this and what could you advise me for this problem ?
Best Regards,
Ahmet
What is the excitation frequency? The problem might be related to the Nyquist theorem.
@Lubos Smolik There are two different materials with seperate mass per unit volumes, inside the laminated plate.
Kazim Ahmet Hasim Can you share the underlying finite element model in an appropriate format?
I have solved the problem and want to share what the problem is. First of all, under a uniform constant load during time, there could not be such a transient response figure that looks like as if there would be a harmonic excitation. The problem is I have selected the duration of the analysis randomly such as 1[s]. I have thought that there would be no problem since Newmark-Beta constant average acceleration method (alpha=1/2-beta=1/4) is unconditionally stable. However, I have learnt that there is a limit obtained from the calculation of the maximum angular free vibration frequency while selecting the time step size to make the results stable. I hope it works for all.
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