Nonlinear structure and nonlinear element for nonlinear analysis

[flyingcow1999a]

I am not sure about my understanding for some issues in nonlinear structural analysis using FEM. And want to ask your experts. Exclude material nonlinearity.

In my understanding, there are two cases regarding nonlinear analysis.

1. nonliear global structural deflection and nonlinear local elemental deformation (eg. warping and shear deformation of beam elements). In this case, both nonlinear numerical method for solving and nonlinear elemnt for modeling are needed.

2. nonliear global structural deflection and linear local elemental deformation. Eg. pin connected slender truss structure - there is geometrical structural nonlinearity but no elemental nonlinear deformation. In this case, only nonlinear numerical method for solving is needed. Linear element can be used for modeling.

Do I understand it correctly? Thank you all.

 

[flyingcow1999a]

Wondering why not a single reply. I did not make it clear or no one has interest in this issue at all? Thanks.

 

[321GO]

Maybe because similar questions have been asked numerous times before and are also readily available on the internet.

Try the search function.

 

[flyingcow1999a]

321GO, thanks for your reply.

Though it is a basic fea tipoc, I do not think it is well understood to every people using FEM. I searched online and have not gotten a satisfied answer yet. Therefore, I posted this here.

 

[ESPcomposites]

- Just so you are aware, there are other types of nonlinearites besides geometry and material. Contact is another form for example.

- Within geometric nonlinearity, there two forms that I am familiar with. One is large deformation (i.e. sine theta no longer approximates theta). Typically the effects known as "stress stiffening" and "stress softening" are considered geometric nonlinearities.

- The local element deformation you refer to is not a "linear vs. nonlinear" effect as you are implying. Rather, it is inherent to the formulation of the element. For example, a basic beam element may not include shear deformation, but a more advanced one would. If you expect to see these effects, then choose the element type accordingly. Some software have more than one variation for a given element type.

Brian

http://www.espcomposites.com