In ABAQUS help I read the applications of direct solution in steady state dynamic analysis as follows , what are the examples of applications and where I can NOT use this method ? I would appreciate a comprehensive answer , thank youhttp://ivt-abaqusdoc.ivt.ntnu.no:2080/v6.11/books/usb/default.htm?startat=pt03ch06s03at09.htmlThe direct-solution steady-state analysis procedure can be used in the following cases for which the eigenvalues cannot be extracted (and, thus, the mode-based steady-state dynamics procedures are not applicable):
- for nonsymmetric stiffness;
- when any form of damping other than modal damping must be included; and
- when viscoelastic material properties must be taken into account.
Hi Farzad
Direct solutions cover all modal cases. It is mainly limited by the problem having to be linear and time invariant, though one can cheat a little with the latter and give things frequency depending properties that do not necessarily comply with causality when examined in the time domain.
Direct solutions are more precise than modal but come at a higher computational cost and, possibly less help in understanding results - modes, after all, are a powerful analysis tool.
So, anything truly nonlinear or time varying would be a No No.
/Claes
Thank you very much Claes Richard Fredö , shall you please exemplify ?
Load dependant springs, mechanisms like latches, any large amplitude motion, etc.
Perhaps it is easier to help if you try instead to state what you try to do?
I am not solving a problem, I was just wondering why this option was added in Abaqus
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