Dynamic Analysis

Altair Forum User
Altair Forum User
Altair Employee
edited October 2020 in Community Q&A

Hello,

Good Afternoon.

I have a model to which I need to apply a base excitation. I am basically trying to simulate a forced vibration case wherein I have 2 load cases, which are as follows:-

·     LC1: 5 – 10 Hz : ±8 mm (Constant displacement)

·     LC2: 10–500 Hz : ±18 m/sec2 (Const. Acceleration)

I am doing it with the FREQUENCY RESPONSE (MODAL) LOAD STEP. I have used all the standard cards that are required for such an analysis like SPCD, RLOAD, DLOAD, FREQ, TABLED1 etc. Let's say I am exciting my model in the X direction, I have checked DOF1(scaled to 1) and unchecked all other DOF's. But the results seem to directly vary with that scale factor which it should but aren't matching with my benchmark results.When i use TABRAND1 instead of TABLED1 i get satisfactory results but I am not sure if I am supposed to do so. I am yet to establish the correct methodology for this sort of forced vibration cases.

 

Could you please help me out.

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