Learning Forum

[abhay mahar]

how to calculate time step in transient modal analysis ?

[Keyur Kanade]

Usually time step < (min mesh size / velocity) 

Please check courant no. and then decide time step size. 

 

[abhay mahar]

i have excel data in form of time .time from .002 to 1.5 sec, with interval of .02 sec. how can i find velocity ? it is modal analysis with transient

[peteroznewman]

This is a Transient Structural model, right?

What is the highest frequency you want to include in your Transient simulation?  How many Modes did you request in the Modal analysis and what was the frequency of the highest mode?

You say your Excel data has an interval of 0.02 seconds. Is that a typo? That is a sampling frequency of 50 Hz which is very low.  Since your first time is 0.002 s, I think that is the interval, which means a 500 Hz sampling frequency. It is recommended to have 20 points per cycle of vibration in your time-history. That means you could simulate frequencies up to 25 Hz.

What quantity is the Excel data?  I assume it is acceleration, but maybe it's displacement. Where was this Excel data measured? How many axes were measured? If only one axis, what direction was measured? What are the boundary conditions for the Modal analysis?

If the accelerometer was on the ground, you can apply that acceleration to the model and solve. Once solved, Velocity is one of the results you can plot.

Regards,
Peter