I have recently been looking for some information regarding ASD graphs which are derived from Random Vibration analysis. Frequency analysis as Random Vibration FEA simulation is relatively new for me and I was wondering whether someone could help me with the issue I keep getting.
After running the actual simulation, the main output I am interested is acceleration response from various nodes in the model. What I noticed is that at the start of response data taken with Define Response Graph tool there is a difference in respect of the input load – most of the time values which were taken with aforementioned tool are lower than the input load (you can see this in the picture below).
I could be wrong (and please correct me if I am), but up to the first fundamental frequency values from every node in the model should be the same as ones from the input load. Sometimes I get this relationship, sometimes I don’t.
Can someone please explain me what am I missing here? Is it something with the software or the actual decrease in value can be theoretically explained?
Thank you in advance
Info regarding the graph:
- red dashed line is the input load.
- blue, grey and orange lines represent acceleration response from different nodes in the model.
*1st fundamental frequency is not reached.