Question about structural softwares

[amateur mariner]

Hi,

When we do a structural analysis in some structural software like ansys, we apply a force and also constrain some point in some or all DOF.Can somebody tell me what is the reason for this?

Also please tell me that after some analysis is done due to a dynamic force we animate the results and see. In animations we observe severe movements of the structure which I feel are extreme.What actually we need to understand from these animations?

Cheers.

[Ad Hoc]

Well, firstly if you do not know why applying a force requires restraint in some or all of the DOF in your model, you should either
1) read the manual
2) not be using FEA
3) go on a training course
4) understand basic structural principals.

Since any of the above 4 listed once 'done' all becomes obvious!

If it is still a mystery i strongly recommend that you do no use the FEA, since you will be restraining your model incorrectly and hence obtaining incorrect answers and not know it! This could lead to a serious disaster, depending upon the structure you are analysing..

[alidesigner]

The golden rule of FEA

Garbage in = garbage out.

That's my biggest concern about 3D cad programs incorporating FEA wizards. Just because a load can be applied and a pretty picture displayed doesnt mean the results are correct.

Very dangerous in the wrong hands.

If you are going to play with FEA you must understand the mathematics behind each element type.

There is a great book available on amazon. It uses nastran in its examples but gives a great balance between theory and practical application.

www.tinyurl.com/fea-book

[Ad Hoc]

alidesigner

well said.

I learnt these lessons the hard way...luckily crane bases used as a "test" to see all those pretty pictures didnt work out too bad...hahaha

FEA is far to complex to be taken ligthly...the more you think you have mastered it, the more there is to learn. It must be the slave, not the master!