Simple Question About Shell constituitve ( ABD) matrix 1

[frztrb]

Hi All

First I would like to know that for shell (and plates?) we use and define ABD matrix like laminates or not ? is it correct that in ABD matrix calculation in the integral , in a laminate , we put the transformed matrix that it's stresses are along the fibers , cause the stresses in that direction matters

and in shell we use the stiffness matrix as it is in solid condition ?

the matrial is orthotropic

and in case that we calcualte ABD matrix , how we input it for example in Abaqus ?

 

[frztrb]

Ok , as I am reading here , on page 15 I see

http://www.colorado.edu/engineering/CAS/courses.d/AFEM.d/AFEM.Ch32.d/AFEM.Ch32.pdf

but the matrix is defined 6 * 6 and I think in shell with one layer we shoul not talk about ABD so ?

but here in this paper

http://www.enu.kz/repository/2010/AIAA-2010-2706.pdf

on page 4 , the ABD matrix is 8 * 8

what is taken into consideration and why is it called ABD here then ??!!

 

[rb1957]

"I think in shell with one layer" ... yes, but it's stiffness depends on the laminate lay-up. so you can model as a plate element and use typically an attached subroutine to assemble the laminates together to derive the ABD matrix.

your colorado.edu reference killed me with math ! ... looking at section 32.5, i think they're refering to their own developed elements (as opposed to NASTRAN) ... their stress vector in equ 32.36 shows three normal stresses and only one (inplane) shear stress. i expected to see a 6dof vector ... normal strain x, y, z, shear strain xy, yz, zx ?

similarly your AIAA reference, the stress vector is defined in equation 1; looks like it's some proprietary code.

I'd consult the user manual of the program you want to use, so that the stress vector is compatable with this coding.



another day in paradise, or is paradise one day closer ?

 

[frztrb]

your attention has given me some points , ok so it looks like that depending on which DOF s of shell we care about , we might shrink the constituitive matrix ?

the Colorado one is a paper I found when I was searching for ABD matrix of shell in google , but it is not discussed like this in Shell and Plate theory books , but sometimes in papers

So I don't know , is the concept written on shell n plate books comply with the one in softwares' manuals ?

do they follow the same thing ?

yet I have not got the complete Idea about the ABD matrix , when it is not a Laminate , why we use the expresssion of ABD for a shell ?

 

[rb1957]

i think all descriptions of the ABD matrix are dependent on the stress (or strain) vector assumed in the element coding.

another day in paradise, or is paradise one day closer ?

 

[frztrb]

what do you mean ?

can you elaborate it please ? for me , I meant before even entering the FEM , some papers mention like according to " classical model of isotropic homogeneous plates " they calculate the Stiffness matrix , and when they calculate the terms they use A , B , D terms , while the material is a one layer shell , not a laminate with fibers

 

[rb1957]

as you've seen with your two examples, the stress vector can be whatever you want it to be based on how you define your element.

another day in paradise, or is paradise one day closer ?