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Why the flexible body deflection is dependent on the number of modes? I believe I already have sufficient number of modes in my MNF.

Abbas Shafiee
I have a flexible shaft in my model by importing an MNF file. I have found the deflection of the shaft (simply supported) is dependent to the number of modes. Only a radial load is applied to the shaft center and I need to confirm the shaft center displacement with classical formulations. I already have 14 modes and I doubled it to 28 and the results changed. Why does this dependency happen? The 60mm diameter shaft spins at a low speed 100 rpm
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    Well, clearly you don't have enough modes.
    This is a part of model tuning that is often forgotten or ignored. But you are doing the right thing, increase number of modes until your results converges. Remember that the interface modes adds six modes each. Often very high frequent, but smeared out among all modes through the Craig-Bampton process.
    All too often I see models with over a dozen interface modes, but only a handful modes are active. That rarely gives a converged behavior.
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    Well, clearly you don't have enough modes.
    This is a part of model tuning that is often forgotten or ignored. But you are doing the right thing, increase number of modes until your results converges. Remember that the interface modes adds six modes each. Often very high frequent, but smeared out among all modes through the Craig-Bampton process.
    All too often I see models with over a dozen interface modes, but only a handful modes are active. That rarely gives a converged behavior.
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