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Simple Question About Shell constituitve ( ABD) matrix

Simple Question About Shell constituitve ( ABD) matrix

(OP)
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 ?

RE: Simple Question About Shell constituitve ( ABD) matrix

"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.

RE: Simple Question About Shell constituitve ( ABD) matrix

(OP)
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 ?

RE: Simple Question About Shell constituitve ( ABD) matrix

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

RE: Simple Question About Shell constituitve ( ABD) matrix

(OP)
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

RE: Simple Question About Shell constituitve ( ABD) matrix

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.

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