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Modeling 3D elements

Modeling 3D elements

Modeling 3D elements

(OP)
Is it possible to add new element types to Cardre_Pro 3.2? I need to model bricks and wonder if I can add elements to the code on a custom basis?

RE: Modeling 3D elements

No the elements types are fixed:
Constant Section beam, tapered beam, pinned beam with variable fixity, wire, deep (shear significant) beam, axial spring, triangular plate (in-plane loads).

RE: Modeling 3D elements

(OP)
Can the behavior of solid bricks be approximated using beams or plates arranged as "boxes" with internal "beams"? I've got a rotating machine shaft with a keyway that I want to model.

RE: Modeling 3D elements

You can model almost anything if you have the pacience and are willing to accept the approximations and the work needed to validate the model. I would start with a cylinder of beams, then artifically set properties until the shaft performed correctly under load by comparing with classical solutions of a real shaft. Having said that, I am reminded of a quote from Robert D. Cook -Concepts and Applications in Finite Element Analysis- "Finite element analysis is the most versatile tool, but not the best analytical tool for every problem"

RE: Modeling 3D elements

(OP)
So far so good - but what about a keyway? Could several cylinders be used and connected using beams? The area with the keyway would then have a unique geometry...

RE: Modeling 3D elements

No, the elements are fixed. The solver in CADRE Pro is not a "standard" solver, it is our own custom design to allow some of the unique elements that are provided in CADRE Pro. The pinned elements with variable flexibility and the constant section beam elements, for example, actually become non-linear beam columns for the advanced solution methods. These kinds of features are not available in most FEM software. That is just one of those tradoffs that a manufacturer must make.

RE: Modeling 3D elements

(OP)
So a 3d triangular grid of beam elements would not make a good estimate of stress in a true 3d solid object? If the beams are pinned and analyzed in increments, would a good estimate of the stress stae at a shaft keyway corner be possible?

RE: Modeling 3D elements

I do not believe you would ever get even close to approximating concentrated stresses in corners of solid objects with a FEM model made of beams. You would need solid elements (and a whole lot of them) and even then the concentrated stresses at the corners would be questionable.

RE: Modeling 3D elements

(OP)
Thanks for your help - can you recommend a good PC based program for such analysis?

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