vultur77
New member
- Jul 12, 2005
- 8
Hello everybody.
I have a shell FE model of a structure that it is made up of a truncated cone shape (just for the sake of clarity, imagine an ice-cream cone without the tip) and a bottom cap (which has a different taper angle, as it would belong to a bigger ice-cream cone) and I am investigating two different designs that differs only in the upper interface of the truncated cone shape:
Design 1) has a C-section flange
Design 2) has a half T section (i.e., like the capital Greek gamma letter)
I have performed a stiffness/flexibility analysis of the two designs by simply applying an unit load at the bottom interface node of the cap (the upper interface is fully clamped: 123456) and design 2 is 3% more stiff than design 1 in axial direction (cone axis).
If I replace, for both designs, the lower part of the cone with an RBE2 (keeping the bottom interface node and transferring only the translational dofs) I got the opposite: design 1 is more stiff than design 2 (still about 3 %).
This last results puzzles me because I am expecting to have the same behaviour as that I got without the RBE2 (i.e., design 2 more stiff).
I have checked the FE model for errors but it seems everything is ok.
Is there someone who has faced a similar situation who can give me some hints on how to explain this or, maybe, to build up a simpler model to better understand the behaviour of the structure?
Thank you in advance.
I have a shell FE model of a structure that it is made up of a truncated cone shape (just for the sake of clarity, imagine an ice-cream cone without the tip) and a bottom cap (which has a different taper angle, as it would belong to a bigger ice-cream cone) and I am investigating two different designs that differs only in the upper interface of the truncated cone shape:
Design 1) has a C-section flange
Design 2) has a half T section (i.e., like the capital Greek gamma letter)
I have performed a stiffness/flexibility analysis of the two designs by simply applying an unit load at the bottom interface node of the cap (the upper interface is fully clamped: 123456) and design 2 is 3% more stiff than design 1 in axial direction (cone axis).
If I replace, for both designs, the lower part of the cone with an RBE2 (keeping the bottom interface node and transferring only the translational dofs) I got the opposite: design 1 is more stiff than design 2 (still about 3 %).
This last results puzzles me because I am expecting to have the same behaviour as that I got without the RBE2 (i.e., design 2 more stiff).
I have checked the FE model for errors but it seems everything is ok.
Is there someone who has faced a similar situation who can give me some hints on how to explain this or, maybe, to build up a simpler model to better understand the behaviour of the structure?
Thank you in advance.