Cheat sheet for finite element 3

[frztrb]

Hello everybody

I was searching for a good cheat sheet for FEM to review it , but could n't find a good one , please if you have any access or link , or you can share it with me

 

[rb1957]

we don't like cheaters !

are you looking for a step-by-step guide for making an FEM ?

Quando Omni Flunkus Moritati

 

[inline6]

or a check sheet?

 

[frztrb]

ok , sorry , yes , I think the step by step guide , I want to make a code of 1D in Matlab , I just needed to have the FEM data at reach , if you have this guide or I should search it

 

[rb1957]

if you want to make your own code there are many texts that can help. the structures detail (for a 1D element) is pretty straightforward, the difficult stuff is in solving the matrix.

Quando Omni Flunkus Moritati

 

[IRstuff]

There are 75 hits in the Matlab file exchange for "FEM"

http://www.mathworks.com/matlabcentral/fileexchange/index?utf8=✓&term=fem

TTFN
faq731-376

Need help writing a question or understanding a reply? forum1529

 

[frztrb]

Thanks a lot for your responses

actually I was studying this file attached , on page 19 there is a function defined that I don't understand , I think the rest is straight forward , and if I undeerstand this 1D , the 2D would not be so much different , and what is the difficulty in solving the matrixes ?

I appreciate all the responses and answers

thank you very much

 

[rb1957]

i'm thinking that the structural aspects of FEA theory are pretty basic. i thought if you were writing your own code, then solving a very large marix gets involved (mathematically), but it looks like MATLAB does it for you (much like excel does).

what was on pg 19 that you couldn't follow ?

Quando Omni Flunkus Moritati

 

[frztrb]

well I am trying to understand this code so will understand the Fem code writing well , just as a start , in that page the IEN and LM are two matrices calculated that for LM is written like :

global degree-of-freedom=LM (local degree-of-freedom, element number)

that when a node 's degree of freedom is one , the IEN and LM are identical , (why ?) , then I don't get the two dof node condition

 

[rb1957]

local dofs are based on the element, like axial load in a rod.
global dofs are based on an external co-ord system, ie components of rod load.

the element stiffness matrix is in terms of local dofs.
the structure stiffness matrix is in terms of global dofs.

that said i disagree with "when a node 's degree of freedom is one , the IEN and LM are identical".
global and local dofs are identical (IMO) if the element is aligned to a global axis.

Quando Omni Flunkus Moritati

 

[frztrb]

Thank you for the responses , but I really wish somebody open the pdf file I uploaded and tell me what is happening step by step in the matlab file , I mean how we form the matrices and the solver , like page 21 , this could be a good guide for me to understand both coding and FEM steps

 

[frztrb]

my problem is mostly the matrice assembly

 

[frztrb]

I do not understand this page : I haven't found a complete explanation to how to code and adress the elements to move from connectivity to EFT then to global

http://fab.cba.mit.edu/classes/MAS.864/people/Rory_Clune/Project/Modeling.html

 

[IceBreakerSours]

Have you tried solving some Direct Stiffness Method exercises by hand? I guess if you tried that, some of your concerns will be addressed. Pick a good book (Bathe, Cook, Zienkiewicz, Liu, Reddy, .. among so many!) and solve a few problems.

Are you new to this forum? If so, please read these FAQ:

http://www.eng-tips.com/faqs.cfm?fid=376

http://www.eng-tips.com/faqs.cfm?fid=1083

 

[frztrb]

thank you for your kind response , well yes , there are examples for one beam element or two connected in series together , but for example when it's a truss and nodes are connected to two or three other nodes , the shape of element stiffness matrix gets difference and I could not find a way yet to do this type and understand the algorithm well