Hello,
I'm in the process of doing a vibration analysis for a client, who wishes to derisk their design with respect to vibration.
I was able to successfully get the model to run, performed the modal analysis,and determined the modal shapes and natural frequencies. However, when looking at the displacements predicted by Pro-Mechanica thru the modal analysis, the displacements seem very large. My first question is, since I haven't put any loads or inputs into the system yet, what are these displacements that mechanica is predicting?
I subsequently ran a dynamic frequency analysis with a number of measure points (monitoring acceleration) at areas of interest per the modal analysis. I was able to generate acceleration vs. frequency curves which seemed reasonable, and showed amplification at some of the natural frequencies.
I then reran the dynamic frequency simulation with some measure points monitoring displacement. I set these to monitor the Z axis displacement, at a point, with Time/Frequency Eval set to on, with Dynamic Evaluation set to "At Each Step".
When I plot this measurement, I get a graph that at 0 Hz is at an impossibly large displacement of 400 m, falling to 0 m in a linear fashion at around 250 Hz, and remaining 0 m for the rest of the spectrum. At this point, I'm a little perplexed what the graph is telling me.
I'm in the process of doing a vibration analysis for a client, who wishes to derisk their design with respect to vibration.
I was able to successfully get the model to run, performed the modal analysis,and determined the modal shapes and natural frequencies. However, when looking at the displacements predicted by Pro-Mechanica thru the modal analysis, the displacements seem very large. My first question is, since I haven't put any loads or inputs into the system yet, what are these displacements that mechanica is predicting?
I subsequently ran a dynamic frequency analysis with a number of measure points (monitoring acceleration) at areas of interest per the modal analysis. I was able to generate acceleration vs. frequency curves which seemed reasonable, and showed amplification at some of the natural frequencies.
I then reran the dynamic frequency simulation with some measure points monitoring displacement. I set these to monitor the Z axis displacement, at a point, with Time/Frequency Eval set to on, with Dynamic Evaluation set to "At Each Step".
When I plot this measurement, I get a graph that at 0 Hz is at an impossibly large displacement of 400 m, falling to 0 m in a linear fashion at around 250 Hz, and remaining 0 m for the rest of the spectrum. At this point, I'm a little perplexed what the graph is telling me.
