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It depends. They would be different.
One of them will give you the bracket frequency alone, considering only ita stiffness as it is bolted. But normally this information alone is not so important, as you probably won't have it operating by itself.
Usually we would model the assembly of bracket plus the motor as this is the operating condition.
Take care with modal analysis as you will have influence both of the bracket itself but also the motor has stiffness added to the system.
So if you model only mass, your frequency will probably be lower than the real life, as you add mass but not stiffness. As an analogy f~srqt(k/m)
The bottom line is that depending on how you sinplify your model, you will get different results, and some modes might not be captured due to the stiffness representation.
as u said , stiffness also influence. BUt how can i model the motor for modal analysis . Any idea ??
Altair Employeehave a motor attached in bracket with four bolted joint. To find the natural frequency of that bracket
can you share an image ? to see the system
, should i use that bracket alone or i should attach the mass of the motor also??
if you intent an operational study thenYou have to consider the mass of the motor, as you are considering an operational study I think you should
best regards
You can start with some simple representation, such as only a shell cylinder with the mass as a concentrated mass tied to your cylinder through an rbe3.
Then you can adjust your thickness to get a nice correlation. This is an idea.
i used conm2 card , but i cant get whether the concentrated mass was created or not . I did so many times as per procedure, any pdf file pls attach for reference
It depends. They would be different.
One of them will give you the bracket frequency alone, considering only ita stiffness as it is bolted. But normally this information alone is not so important, as you probably won't have it operating by itself.
Usually we would model the assembly of bracket plus the motor as this is the operating condition.
Take care with modal analysis as you will have influence both of the bracket itself but also the motor has stiffness added to the system.
So if you model only mass, your frequency will probably be lower than the real life, as you add mass but not stiffness. As an analogy f~srqt(k/m)
The bottom line is that depending on how you sinplify your model, you will get different results, and some modes might not be captured due to the stiffness representation.