springs as restraints?

[bnrg]

I have been reviewing some of the models in the book 'Building better products with FEA' by Adams and Askenazi and am having trouble with the boundary condition examples that they use with the link on page 295. The link is a tension member loaded by forces applied on 2 pins. In example '8.16a' they 'constrain' the mechanica model only with the applied loads and some springs. I am using WF3 and cannot find a way to get this to work as there are no applied constraints, the analysis won't even start without this. Can some one explain to me what I am missing? My understanding is that mechanica requires actual applied constraints-it does not consider balanced loads or springs to make a constrained model.

 

[OnlineFEASolver]

I would avoid running a model without any constraints. I am surprised such a book would recommend just holding it with springs . Just replace one of the force on your pins with a contraint in the same direction.

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[mloew]

A modal analysis is valid without constraints. You still need to removed the first 6 rigid body modes.

An inertia relief solution will also be valid when under constrained.

Perhaps the ends of the springs were to ground; this would effectively constrain the models.


Best regards,

Matthew Ian Loew

http://www.cometsolutions.com